10464 lines
385 KiB
Plaintext
10464 lines
385 KiB
Plaintext
@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
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@c 2000, 2001, 2002 Free Software Foundation, Inc.
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@c This is part of the GCC manual.
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@c For copying conditions, see the file gcc.texi.
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@ignore
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@c man begin COPYRIGHT
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Copyright @copyright{} 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997,
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1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.1 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being ``GNU General Public License'' and ``Funding
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Free Software'', the Front-Cover texts being (a) (see below), and with
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the Back-Cover Texts being (b) (see below). A copy of the license is
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included in the gfdl(7) man page.
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development.
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@c man end
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@c Set file name and title for the man page.
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@setfilename gcc
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@settitle GNU project C and C++ compiler
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@c man begin SYNOPSIS
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gcc [@option{-c}|@option{-S}|@option{-E}] [@option{-std=}@var{standard}]
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[@option{-g}] [@option{-pg}] [@option{-O}@var{level}]
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[@option{-W}@var{warn}@dots{}] [@option{-pedantic}]
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[@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}]
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[@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}]
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[@option{-f}@var{option}@dots{}] [@option{-m}@var{machine-option}@dots{}]
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[@option{-o} @var{outfile}] @var{infile}@dots{}
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Only the most useful options are listed here; see below for the
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remainder. @samp{g++} accepts mostly the same options as @samp{gcc}.
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@c man end
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@c man begin SEEALSO
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gpl(7), gfdl(7), fsf-funding(7),
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cpp(1), gcov(1), g77(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1)
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and the Info entries for @file{gcc}, @file{cpp}, @file{g77}, @file{as},
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@file{ld}, @file{binutils} and @file{gdb}.
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@c man end
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@c man begin BUGS
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For instructions on reporting bugs, see
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@w{@uref{http://gcc.gnu.org/bugs.html}}. Use of the @command{gccbug}
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script to report bugs is recommended.
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@c man end
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@c man begin AUTHOR
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See the Info entry for @command{gcc}, or
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@w{@uref{http://gcc.gnu.org/onlinedocs/gcc/Contributors.html}},
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for contributors to GCC@.
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@c man end
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@end ignore
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@node Invoking GCC
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@chapter GCC Command Options
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@cindex GCC command options
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@cindex command options
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@cindex options, GCC command
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@c man begin DESCRIPTION
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When you invoke GCC, it normally does preprocessing, compilation,
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assembly and linking. The ``overall options'' allow you to stop this
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process at an intermediate stage. For example, the @option{-c} option
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says not to run the linker. Then the output consists of object files
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output by the assembler.
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Other options are passed on to one stage of processing. Some options
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control the preprocessor and others the compiler itself. Yet other
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options control the assembler and linker; most of these are not
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documented here, since you rarely need to use any of them.
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@cindex C compilation options
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Most of the command line options that you can use with GCC are useful
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for C programs; when an option is only useful with another language
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(usually C++), the explanation says so explicitly. If the description
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for a particular option does not mention a source language, you can use
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that option with all supported languages.
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@cindex C++ compilation options
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@xref{Invoking G++,,Compiling C++ Programs}, for a summary of special
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options for compiling C++ programs.
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@cindex grouping options
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@cindex options, grouping
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The @command{gcc} program accepts options and file names as operands. Many
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options have multi-letter names; therefore multiple single-letter options
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may @emph{not} be grouped: @option{-dr} is very different from @w{@samp{-d
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-r}}.
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@cindex order of options
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@cindex options, order
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You can mix options and other arguments. For the most part, the order
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you use doesn't matter. Order does matter when you use several options
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of the same kind; for example, if you specify @option{-L} more than once,
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the directories are searched in the order specified.
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Many options have long names starting with @samp{-f} or with
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@samp{-W}---for example, @option{-fforce-mem},
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@option{-fstrength-reduce}, @option{-Wformat} and so on. Most of
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these have both positive and negative forms; the negative form of
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@option{-ffoo} would be @option{-fno-foo}. This manual documents
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only one of these two forms, whichever one is not the default.
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@c man end
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@xref{Option Index}, for an index to GCC's options.
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@menu
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* Option Summary:: Brief list of all options, without explanations.
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* Overall Options:: Controlling the kind of output:
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an executable, object files, assembler files,
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or preprocessed source.
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* Invoking G++:: Compiling C++ programs.
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* C Dialect Options:: Controlling the variant of C language compiled.
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* C++ Dialect Options:: Variations on C++.
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* Objective-C Dialect Options:: Variations on Objective-C.
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* Language Independent Options:: Controlling how diagnostics should be
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formatted.
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* Warning Options:: How picky should the compiler be?
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* Debugging Options:: Symbol tables, measurements, and debugging dumps.
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* Optimize Options:: How much optimization?
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* Preprocessor Options:: Controlling header files and macro definitions.
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Also, getting dependency information for Make.
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* Assembler Options:: Passing options to the assembler.
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* Link Options:: Specifying libraries and so on.
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* Directory Options:: Where to find header files and libraries.
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Where to find the compiler executable files.
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* Spec Files:: How to pass switches to sub-processes.
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* Target Options:: Running a cross-compiler, or an old version of GCC.
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* Submodel Options:: Specifying minor hardware or convention variations,
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such as 68010 vs 68020.
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* Code Gen Options:: Specifying conventions for function calls, data layout
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and register usage.
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* Environment Variables:: Env vars that affect GCC.
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* Running Protoize:: Automatically adding or removing function prototypes.
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@end menu
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@c man begin OPTIONS
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@node Option Summary
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@section Option Summary
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Here is a summary of all the options, grouped by type. Explanations are
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in the following sections.
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@table @emph
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@item Overall Options
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@xref{Overall Options,,Options Controlling the Kind of Output}.
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@gccoptlist{
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-c -S -E -o @var{file} -pipe -pass-exit-codes -x @var{language} @gol
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-v --target-help --help}
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@item C Language Options
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@xref{C Dialect Options,,Options Controlling C Dialect}.
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@gccoptlist{
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-ansi -std=@var{standard} -aux-info @var{filename} @gol
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-fno-asm -fno-builtin -fno-builtin-@var{function} @gol
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-fhosted -ffreestanding @gol
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-trigraphs -traditional -traditional-cpp @gol
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-fallow-single-precision -fcond-mismatch @gol
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-fsigned-bitfields -fsigned-char @gol
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-funsigned-bitfields -funsigned-char @gol
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-fwritable-strings -fshort-wchar}
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@item C++ Language Options
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@xref{C++ Dialect Options,,Options Controlling C++ Dialect}.
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@gccoptlist{
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-fno-access-control -fcheck-new -fconserve-space @gol
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-fno-const-strings -fdollars-in-identifiers @gol
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-fno-elide-constructors @gol
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-fno-enforce-eh-specs -fexternal-templates @gol
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-falt-external-templates @gol
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-ffor-scope -fno-for-scope -fno-gnu-keywords @gol
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-fno-implicit-templates @gol
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-fno-implicit-inline-templates @gol
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-fno-implement-inlines -fms-extensions @gol
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-fno-nonansi-builtins -fno-operator-names @gol
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-fno-optional-diags -fpermissive @gol
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-frepo -fno-rtti -fstats -ftemplate-depth-@var{n} @gol
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-fuse-cxa-atexit -fvtable-gc -fno-weak -nostdinc++ @gol
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-fno-default-inline -Wctor-dtor-privacy @gol
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-Wnon-virtual-dtor -Wreorder @gol
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-Weffc++ -Wno-deprecated @gol
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-Wno-non-template-friend -Wold-style-cast @gol
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-Woverloaded-virtual -Wno-pmf-conversions @gol
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-Wsign-promo -Wsynth}
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@item Objective-C Language Options
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@xref{Objective-C Dialect Options,,Options Controlling Objective-C Dialect}.
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@gccoptlist{
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-fconstant-string-class=@var{class-name} @gol
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-fgnu-runtime -fnext-runtime -gen-decls @gol
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-Wno-protocol -Wselector}
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@item Language Independent Options
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@xref{Language Independent Options,,Options to Control Diagnostic Messages Formatting}.
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@gccoptlist{
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-fmessage-length=@var{n} @gol
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-fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]}}
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@item Warning Options
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@xref{Warning Options,,Options to Request or Suppress Warnings}.
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@gccoptlist{
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-fsyntax-only -pedantic -pedantic-errors @gol
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-w -W -Wall -Waggregate-return @gol
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-Wcast-align -Wcast-qual -Wchar-subscripts -Wcomment @gol
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-Wconversion -Wno-deprecated-declarations @gol
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-Wdisabled-optimization -Wdiv-by-zero -Werror @gol
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-Wfloat-equal -Wformat -Wformat=2 @gol
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-Wformat-nonliteral -Wformat-security @gol
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-Wimplicit -Wimplicit-int @gol
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-Wimplicit-function-declaration @gol
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-Werror-implicit-function-declaration @gol
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-Wimport -Winline @gol
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-Wlarger-than-@var{len} -Wlong-long @gol
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-Wmain -Wmissing-braces -Wmissing-declarations @gol
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-Wmissing-format-attribute -Wmissing-noreturn @gol
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-Wmultichar -Wno-format-extra-args -Wno-format-y2k @gol
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-Wno-import -Wpacked -Wpadded @gol
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-Wparentheses -Wpointer-arith -Wredundant-decls @gol
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-Wreturn-type -Wsequence-point -Wshadow @gol
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-Wsign-compare -Wswitch -Wsystem-headers @gol
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-Wtrigraphs -Wundef -Wuninitialized @gol
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-Wunknown-pragmas -Wunreachable-code @gol
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-Wunused -Wunused-function -Wunused-label -Wunused-parameter @gol
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-Wunused-value -Wunused-variable -Wwrite-strings}
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@item C-only Warning Options
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@gccoptlist{
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-Wbad-function-cast -Wmissing-prototypes -Wnested-externs @gol
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-Wstrict-prototypes -Wtraditional}
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@item Debugging Options
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@xref{Debugging Options,,Options for Debugging Your Program or GCC}.
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@gccoptlist{
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-d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol
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-fdump-unnumbered -fdump-translation-unit@r{[}-@var{n}@r{]} @gol
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-fdump-class-hierarchy@r{[}-@var{n}@r{]} @gol
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-fdump-tree-original@r{[}-@var{n}@r{]} -fdump-tree-optimized@r{[}-@var{n}@r{]} @gol
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-fdump-tree-inlined@r{[}-@var{n}@r{]} @gol
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-fmem-report -fpretend-float @gol
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-fprofile-arcs -ftest-coverage -ftime-report @gol
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-g -g@var{level} -gcoff -gdwarf -gdwarf-1 -gdwarf-1+ -gdwarf-2 @gol
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-ggdb -gstabs -gstabs+ -gvms -gxcoff -gxcoff+ @gol
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-p -pg -print-file-name=@var{library} -print-libgcc-file-name @gol
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-print-multi-directory -print-multi-lib @gol
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-print-prog-name=@var{program} -print-search-dirs -Q @gol
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-save-temps -time}
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@item Optimization Options
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@xref{Optimize Options,,Options that Control Optimization}.
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@gccoptlist{
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-falign-functions=@var{n} -falign-jumps=@var{n} @gol
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-falign-labels=@var{n} -falign-loops=@var{n} @gol
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-fbranch-probabilities -fcaller-saves -fcprop-registers @gol
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-fcse-follow-jumps -fcse-skip-blocks -fdata-sections @gol
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-fdelayed-branch -fdelete-null-pointer-checks @gol
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-fexpensive-optimizations -ffast-math -ffloat-store @gol
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-fforce-addr -fforce-mem -ffunction-sections @gol
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-fgcse -fgcse-lm -fgcse-sm @gol
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-finline-functions -finline-limit=@var{n} -fkeep-inline-functions @gol
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-fkeep-static-consts -fmerge-constants -fmerge-all-constants @gol
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-fmove-all-movables -fno-default-inline -fno-defer-pop @gol
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-fno-function-cse -fno-guess-branch-probability @gol
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-fno-inline -fno-math-errno -fno-peephole -fno-peephole2 @gol
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-funsafe-math-optimizations -fno-trapping-math @gol
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-fomit-frame-pointer -foptimize-register-move @gol
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-foptimize-sibling-calls -fprefetch-loop-arrays @gol
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-freduce-all-givs -fregmove -frename-registers @gol
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-frerun-cse-after-loop -frerun-loop-opt @gol
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-fschedule-insns -fschedule-insns2 @gol
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-fsingle-precision-constant -fssa -fssa-ccp -fssa-dce @gol
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-fstrength-reduce -fstrict-aliasing -fthread-jumps -ftrapv @gol
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-funroll-all-loops -funroll-loops @gol
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--param @var{name}=@var{value}
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-O -O0 -O1 -O2 -O3 -Os}
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@item Preprocessor Options
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@xref{Preprocessor Options,,Options Controlling the Preprocessor}.
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@gccoptlist{
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-$ -A@var{question}=@var{answer} -A-@var{question}@r{[}=@var{answer}@r{]} @gol
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-C -dD -dI -dM -dN @gol
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-D@var{macro}@r{[}=@var{defn}@r{]} -E -H @gol
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-idirafter @var{dir} @gol
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-include @var{file} -imacros @var{file} @gol
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-iprefix @var{file} -iwithprefix @var{dir} @gol
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-iwithprefixbefore @var{dir} -isystem @var{dir} @gol
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-M -MM -MF -MG -MP -MQ -MT -nostdinc -P -remap @gol
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-trigraphs -undef -U@var{macro} -Wp,@var{option}}
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@item Assembler Option
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@xref{Assembler Options,,Passing Options to the Assembler}.
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@gccoptlist{
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-Wa,@var{option}}
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@item Linker Options
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@xref{Link Options,,Options for Linking}.
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@gccoptlist{
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@var{object-file-name} -l@var{library} @gol
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-nostartfiles -nodefaultlibs -nostdlib @gol
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-s -static -static-libgcc -shared -shared-libgcc -symbolic @gol
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-Wl,@var{option} -Xlinker @var{option} @gol
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-u @var{symbol}}
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@item Directory Options
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@xref{Directory Options,,Options for Directory Search}.
|
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@gccoptlist{
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-B@var{prefix} -I@var{dir} -I- -L@var{dir} -specs=@var{file}}
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@item Target Options
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|
@c I wrote this xref this way to avoid overfull hbox. -- rms
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@xref{Target Options}.
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@gccoptlist{
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-b @var{machine} -V @var{version}}
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@item Machine Dependent Options
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|
@xref{Submodel Options,,Hardware Models and Configurations}.
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|
@emph{M680x0 Options}
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|
@gccoptlist{
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|
-m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040 @gol
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|
-m68060 -mcpu32 -m5200 -m68881 -mbitfield -mc68000 -mc68020 @gol
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|
-mfpa -mnobitfield -mrtd -mshort -msoft-float -mpcrel @gol
|
|
-malign-int -mstrict-align}
|
|
|
|
@emph{M68hc1x Options}
|
|
@gccoptlist{
|
|
-m6811 -m6812 -m68hc11 -m68hc12 @gol
|
|
-mauto-incdec -mshort -msoft-reg-count=@var{count}}
|
|
|
|
@emph{VAX Options}
|
|
@gccoptlist{
|
|
-mg -mgnu -munix}
|
|
|
|
@emph{SPARC Options}
|
|
@gccoptlist{
|
|
-mcpu=@var{cpu-type} @gol
|
|
-mtune=@var{cpu-type} @gol
|
|
-mcmodel=@var{code-model} @gol
|
|
-m32 -m64 @gol
|
|
-mapp-regs -mbroken-saverestore -mcypress @gol
|
|
-mepilogue -mfaster-structs -mflat @gol
|
|
-mfpu -mhard-float -mhard-quad-float @gol
|
|
-mimpure-text -mlive-g0 -mno-app-regs @gol
|
|
-mno-epilogue -mno-faster-structs -mno-flat -mno-fpu @gol
|
|
-mno-impure-text -mno-stack-bias -mno-unaligned-doubles @gol
|
|
-msoft-float -msoft-quad-float -msparclite -mstack-bias @gol
|
|
-msupersparc -munaligned-doubles -mv8}
|
|
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|
@emph{Convex Options}
|
|
@gccoptlist{
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|
-mc1 -mc2 -mc32 -mc34 -mc38 @gol
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|
-margcount -mnoargcount @gol
|
|
-mlong32 -mlong64 @gol
|
|
-mvolatile-cache -mvolatile-nocache}
|
|
|
|
@emph{AMD29K Options}
|
|
@gccoptlist{
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|
-m29000 -m29050 -mbw -mnbw -mdw -mndw @gol
|
|
-mlarge -mnormal -msmall @gol
|
|
-mkernel-registers -mno-reuse-arg-regs @gol
|
|
-mno-stack-check -mno-storem-bug @gol
|
|
-mreuse-arg-regs -msoft-float -mstack-check @gol
|
|
-mstorem-bug -muser-registers}
|
|
|
|
@emph{ARM Options}
|
|
@gccoptlist{
|
|
-mapcs-frame -mno-apcs-frame @gol
|
|
-mapcs-26 -mapcs-32 @gol
|
|
-mapcs-stack-check -mno-apcs-stack-check @gol
|
|
-mapcs-float -mno-apcs-float @gol
|
|
-mapcs-reentrant -mno-apcs-reentrant @gol
|
|
-msched-prolog -mno-sched-prolog @gol
|
|
-mlittle-endian -mbig-endian -mwords-little-endian @gol
|
|
-malignment-traps -mno-alignment-traps @gol
|
|
-msoft-float -mhard-float -mfpe @gol
|
|
-mthumb-interwork -mno-thumb-interwork @gol
|
|
-mcpu=@var{name} -march=@var{name} -mfpe=@var{name} @gol
|
|
-mstructure-size-boundary=@var{n} @gol
|
|
-mbsd -mxopen -mno-symrename @gol
|
|
-mabort-on-noreturn @gol
|
|
-mlong-calls -mno-long-calls @gol
|
|
-msingle-pic-base -mno-single-pic-base @gol
|
|
-mpic-register=@var{reg} @gol
|
|
-mnop-fun-dllimport @gol
|
|
-mpoke-function-name @gol
|
|
-mthumb -marm @gol
|
|
-mtpcs-frame -mtpcs-leaf-frame @gol
|
|
-mcaller-super-interworking -mcallee-super-interworking }
|
|
|
|
@emph{MN10200 Options}
|
|
@gccoptlist{
|
|
-mrelax}
|
|
|
|
@emph{MN10300 Options}
|
|
@gccoptlist{
|
|
-mmult-bug -mno-mult-bug @gol
|
|
-mam33 -mno-am33 @gol
|
|
-mno-crt0 -mrelax}
|
|
|
|
@emph{M32R/D Options}
|
|
@gccoptlist{
|
|
-m32rx -m32r -mcode-model=@var{model-type} -msdata=@var{sdata-type} @gol
|
|
-G @var{num}}
|
|
|
|
@emph{M88K Options}
|
|
@gccoptlist{
|
|
-m88000 -m88100 -m88110 -mbig-pic @gol
|
|
-mcheck-zero-division -mhandle-large-shift @gol
|
|
-midentify-revision -mno-check-zero-division @gol
|
|
-mno-ocs-debug-info -mno-ocs-frame-position @gol
|
|
-mno-optimize-arg-area -mno-serialize-volatile @gol
|
|
-mno-underscores -mocs-debug-info @gol
|
|
-mocs-frame-position -moptimize-arg-area @gol
|
|
-mserialize-volatile -mshort-data-@var{num} -msvr3 @gol
|
|
-msvr4 -mtrap-large-shift -muse-div-instruction @gol
|
|
-mversion-03.00 -mwarn-passed-structs}
|
|
|
|
@emph{RS/6000 and PowerPC Options}
|
|
@gccoptlist{
|
|
-mcpu=@var{cpu-type} @gol
|
|
-mtune=@var{cpu-type} @gol
|
|
-mpower -mno-power -mpower2 -mno-power2 @gol
|
|
-mpowerpc -mpowerpc64 -mno-powerpc @gol
|
|
-maltivec -mno-altivec @gol
|
|
-mpowerpc-gpopt -mno-powerpc-gpopt @gol
|
|
-mpowerpc-gfxopt -mno-powerpc-gfxopt @gol
|
|
-mnew-mnemonics -mold-mnemonics @gol
|
|
-mfull-toc -mminimal-toc -mno-fop-in-toc -mno-sum-in-toc @gol
|
|
-m64 -m32 -mxl-call -mno-xl-call -mpe @gol
|
|
-msoft-float -mhard-float -mmultiple -mno-multiple @gol
|
|
-mstring -mno-string -mupdate -mno-update @gol
|
|
-mfused-madd -mno-fused-madd -mbit-align -mno-bit-align @gol
|
|
-mstrict-align -mno-strict-align -mrelocatable @gol
|
|
-mno-relocatable -mrelocatable-lib -mno-relocatable-lib @gol
|
|
-mtoc -mno-toc -mlittle -mlittle-endian -mbig -mbig-endian @gol
|
|
-mcall-aix -mcall-sysv -mcall-netbsd @gol
|
|
-maix-struct-return -msvr4-struct-return
|
|
-mabi=altivec @gol
|
|
-mprototype -mno-prototype @gol
|
|
-msim -mmvme -mads -myellowknife -memb -msdata @gol
|
|
-msdata=@var{opt} -mvxworks -G @var{num} -pthread}
|
|
|
|
@emph{RT Options}
|
|
@gccoptlist{
|
|
-mcall-lib-mul -mfp-arg-in-fpregs -mfp-arg-in-gregs @gol
|
|
-mfull-fp-blocks -mhc-struct-return -min-line-mul @gol
|
|
-mminimum-fp-blocks -mnohc-struct-return}
|
|
|
|
@emph{MIPS Options}
|
|
@gccoptlist{
|
|
-mabicalls -march=@var{cpu-type} -mtune=@var{cpu=type} @gol
|
|
-mcpu=@var{cpu-type} -membedded-data -muninit-const-in-rodata @gol
|
|
-membedded-pic -mfp32 -mfp64 -mfused-madd -mno-fused-madd @gol
|
|
-mgas -mgp32 -mgp64 @gol
|
|
-mgpopt -mhalf-pic -mhard-float -mint64 -mips1 @gol
|
|
-mips2 -mips3 -mips4 -mlong64 -mlong32 -mlong-calls -mmemcpy @gol
|
|
-mmips-as -mmips-tfile -mno-abicalls @gol
|
|
-mno-embedded-data -mno-uninit-const-in-rodata @gol
|
|
-mno-embedded-pic -mno-gpopt -mno-long-calls @gol
|
|
-mno-memcpy -mno-mips-tfile -mno-rnames -mno-stats @gol
|
|
-mrnames -msoft-float @gol
|
|
-m4650 -msingle-float -mmad @gol
|
|
-mstats -EL -EB -G @var{num} -nocpp @gol
|
|
-mabi=32 -mabi=n32 -mabi=64 -mabi=eabi @gol
|
|
-mfix7000 -mno-crt0 -mflush-func=@var{func} -mno-flush-func}
|
|
|
|
@emph{i386 and x86-64 Options}
|
|
@gccoptlist{
|
|
-mcpu=@var{cpu-type} -march=@var{cpu-type} -mfpmath=@var{unit} @gol
|
|
-masm=@var{dialect} -mno-fancy-math-387 @gol
|
|
-mno-fp-ret-in-387 -msoft-float -msvr3-shlib @gol
|
|
-mno-wide-multiply -mrtd -malign-double @gol
|
|
-mpreferred-stack-boundary=@var{num} @gol
|
|
-mmmx -msse -msse2 -msse-math -m3dnow @gol
|
|
-mthreads -mno-align-stringops -minline-all-stringops @gol
|
|
-mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol
|
|
-m96bit-long-double -mregparm=@var{num} -momit-leaf-frame-pointer @gol
|
|
-mno-red-zone@gol
|
|
-m32 -m64}
|
|
|
|
@emph{HPPA Options}
|
|
@gccoptlist{
|
|
-march=@var{architecture-type} @gol
|
|
-mbig-switch -mdisable-fpregs -mdisable-indexing @gol
|
|
-mfast-indirect-calls -mgas -mjump-in-delay @gol
|
|
-mlong-load-store -mno-big-switch -mno-disable-fpregs @gol
|
|
-mno-disable-indexing -mno-fast-indirect-calls -mno-gas @gol
|
|
-mno-jump-in-delay -mno-long-load-store @gol
|
|
-mno-portable-runtime -mno-soft-float @gol
|
|
-mno-space-regs -msoft-float -mpa-risc-1-0 @gol
|
|
-mpa-risc-1-1 -mpa-risc-2-0 -mportable-runtime @gol
|
|
-mschedule=@var{cpu-type} -mspace-regs}
|
|
|
|
@emph{Intel 960 Options}
|
|
@gccoptlist{
|
|
-m@var{cpu-type} -masm-compat -mclean-linkage @gol
|
|
-mcode-align -mcomplex-addr -mleaf-procedures @gol
|
|
-mic-compat -mic2.0-compat -mic3.0-compat @gol
|
|
-mintel-asm -mno-clean-linkage -mno-code-align @gol
|
|
-mno-complex-addr -mno-leaf-procedures @gol
|
|
-mno-old-align -mno-strict-align -mno-tail-call @gol
|
|
-mnumerics -mold-align -msoft-float -mstrict-align @gol
|
|
-mtail-call}
|
|
|
|
@emph{DEC Alpha Options}
|
|
@gccoptlist{
|
|
-mno-fp-regs -msoft-float -malpha-as -mgas @gol
|
|
-mieee -mieee-with-inexact -mieee-conformant @gol
|
|
-mfp-trap-mode=@var{mode} -mfp-rounding-mode=@var{mode} @gol
|
|
-mtrap-precision=@var{mode} -mbuild-constants @gol
|
|
-mcpu=@var{cpu-type} -mtune=@var{cpu-type} @gol
|
|
-mbwx -mmax -mfix -mcix @gol
|
|
-mfloat-vax -mfloat-ieee @gol
|
|
-mexplicit-relocs -msmall-data -mlarge-data @gol
|
|
-mmemory-latency=@var{time}}
|
|
|
|
@emph{DEC Alpha/VMS Options}
|
|
@gccoptlist{
|
|
-mvms-return-codes}
|
|
|
|
@emph{Clipper Options}
|
|
@gccoptlist{
|
|
-mc300 -mc400}
|
|
|
|
@emph{H8/300 Options}
|
|
@gccoptlist{
|
|
-mrelax -mh -ms -mint32 -malign-300}
|
|
|
|
@emph{SH Options}
|
|
@gccoptlist{
|
|
-m1 -m2 -m3 -m3e @gol
|
|
-m4-nofpu -m4-single-only -m4-single -m4 @gol
|
|
-mb -ml -mdalign -mrelax @gol
|
|
-mbigtable -mfmovd -mhitachi -mnomacsave @gol
|
|
-mieee -misize -mpadstruct -mspace @gol
|
|
-mprefergot -musermode}
|
|
|
|
@emph{System V Options}
|
|
@gccoptlist{
|
|
-Qy -Qn -YP,@var{paths} -Ym,@var{dir}}
|
|
|
|
@emph{ARC Options}
|
|
@gccoptlist{
|
|
-EB -EL @gol
|
|
-mmangle-cpu -mcpu=@var{cpu} -mtext=@var{text-section} @gol
|
|
-mdata=@var{data-section} -mrodata=@var{readonly-data-section}}
|
|
|
|
@emph{TMS320C3x/C4x Options}
|
|
@gccoptlist{
|
|
-mcpu=@var{cpu} -mbig -msmall -mregparm -mmemparm @gol
|
|
-mfast-fix -mmpyi -mbk -mti -mdp-isr-reload @gol
|
|
-mrpts=@var{count} -mrptb -mdb -mloop-unsigned @gol
|
|
-mparallel-insns -mparallel-mpy -mpreserve-float}
|
|
|
|
@emph{V850 Options}
|
|
@gccoptlist{
|
|
-mlong-calls -mno-long-calls -mep -mno-ep @gol
|
|
-mprolog-function -mno-prolog-function -mspace @gol
|
|
-mtda=@var{n} -msda=@var{n} -mzda=@var{n} @gol
|
|
-mv850 -mbig-switch}
|
|
|
|
@emph{NS32K Options}
|
|
@gccoptlist{
|
|
-m32032 -m32332 -m32532 -m32081 -m32381 @gol
|
|
-mmult-add -mnomult-add -msoft-float -mrtd -mnortd @gol
|
|
-mregparam -mnoregparam -msb -mnosb @gol
|
|
-mbitfield -mnobitfield -mhimem -mnohimem}
|
|
|
|
@emph{AVR Options}
|
|
@gccoptlist{
|
|
-mmcu=@var{mcu} -msize -minit-stack=@var{n} -mno-interrupts @gol
|
|
-mcall-prologues -mno-tablejump -mtiny-stack}
|
|
|
|
@emph{MCore Options}
|
|
@gccoptlist{
|
|
-mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediates @gol
|
|
-mno-relax-immediates -mwide-bitfields -mno-wide-bitfields @gol
|
|
-m4byte-functions -mno-4byte-functions -mcallgraph-data @gol
|
|
-mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim @gol
|
|
-mlittle-endian -mbig-endian -m210 -m340 -mstack-increment}
|
|
|
|
@emph{MMIX Options}
|
|
@gccoptlist{
|
|
-mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon -mabi=gnu @gol
|
|
-mabi=mmixware -mzero-extend -mknuthdiv -mtoplevel-symbols @gol
|
|
-melf -mbranch-predict -mno-branch-predict}
|
|
|
|
@emph{IA-64 Options}
|
|
@gccoptlist{
|
|
-mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic @gol
|
|
-mvolatile-asm-stop -mb-step -mregister-names -mno-sdata @gol
|
|
-mconstant-gp -mauto-pic -minline-divide-min-latency @gol
|
|
-minline-divide-max-throughput -mno-dwarf2-asm @gol
|
|
-mfixed-range=@var{register-range}}
|
|
|
|
@emph{D30V Options}
|
|
@gccoptlist{
|
|
-mextmem -mextmemory -monchip -mno-asm-optimize -masm-optimize @gol
|
|
-mbranch-cost=@var{n} -mcond-exec=@var{n}}
|
|
|
|
@emph{S/390 and zSeries Options}
|
|
@gccoptlist{
|
|
-mhard-float -msoft-float -mbackchain -mno-backchain @gol
|
|
-msmall-exec -mno-small-exec -mmvcle -mno-mvcle @gol
|
|
-m64 -m31 -mdebug -mno-debug}
|
|
|
|
@emph{CRIS Options}
|
|
@gccoptlist{
|
|
-mcpu=@var{cpu} -march=@var{cpu} -mtune=@var{cpu} @gol
|
|
-mmax-stack-frame=@var{n} -melinux-stacksize=@var{n} @gol
|
|
-metrax4 -metrax100 -mpdebug -mcc-init -mno-side-effects @gol
|
|
-mstack-align -mdata-align -mconst-align @gol
|
|
-m32-bit -m16-bit -m8-bit -mno-prologue-epilogue -mno-gotplt @gol
|
|
-melf -maout -melinux -mlinux -sim -sim2}
|
|
|
|
@emph{PDP-11 Options}
|
|
@gccoptlist{
|
|
-mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 @gol
|
|
-mbcopy -mbcopy-builtin -mint32 -mno-int16 @gol
|
|
-mint16 -mno-int32 -mfloat32 -mno-float64 @gol
|
|
-mfloat64 -mno-float32 -mabshi -mno-abshi @gol
|
|
-mbranch-expensive -mbranch-cheap @gol
|
|
-msplit -mno-split -munix-asm -mdec-asm}
|
|
|
|
@emph{Xstormy16 Options}
|
|
@gccoptlist{
|
|
-msim}
|
|
|
|
@emph{Xtensa Options}
|
|
@gccoptlist{
|
|
-mbig-endian -mlittle-endian @gol
|
|
-mdensity -mno-density @gol
|
|
-mmac16 -mno-mac16 @gol
|
|
-mmul16 -mno-mul16 @gol
|
|
-mmul32 -mno-mul32 @gol
|
|
-mnsa -mno-nsa @gol
|
|
-mminmax -mno-minmax @gol
|
|
-msext -mno-sext @gol
|
|
-mbooleans -mno-booleans @gol
|
|
-mhard-float -msoft-float @gol
|
|
-mfused-madd -mno-fused-madd @gol
|
|
-mserialize-volatile -mno-serialize-volatile @gol
|
|
-mtext-section-literals -mno-text-section-literals @gol
|
|
-mtarget-align -mno-target-align @gol
|
|
-mlongcalls -mno-longcalls}
|
|
|
|
@item Code Generation Options
|
|
@xref{Code Gen Options,,Options for Code Generation Conventions}.
|
|
@gccoptlist{
|
|
-fcall-saved-@var{reg} -fcall-used-@var{reg} @gol
|
|
-ffixed-@var{reg} -fexceptions @gol
|
|
-fnon-call-exceptions -funwind-tables @gol
|
|
-fasynchronous-unwind-tables @gol
|
|
-finhibit-size-directive -finstrument-functions @gol
|
|
-fno-common -fno-ident -fno-gnu-linker @gol
|
|
-fpcc-struct-return -fpic -fPIC @gol
|
|
-freg-struct-return -fshared-data -fshort-enums @gol
|
|
-fshort-double -fvolatile @gol
|
|
-fvolatile-global -fvolatile-static @gol
|
|
-fverbose-asm -fpack-struct -fstack-check @gol
|
|
-fstack-limit-register=@var{reg} -fstack-limit-symbol=@var{sym} @gol
|
|
-fargument-alias -fargument-noalias @gol
|
|
-fargument-noalias-global -fleading-underscore}
|
|
@end table
|
|
|
|
@menu
|
|
* Overall Options:: Controlling the kind of output:
|
|
an executable, object files, assembler files,
|
|
or preprocessed source.
|
|
* C Dialect Options:: Controlling the variant of C language compiled.
|
|
* C++ Dialect Options:: Variations on C++.
|
|
* Objective-C Dialect Options:: Variations on Objective-C.
|
|
* Language Independent Options:: Controlling how diagnostics should be
|
|
formatted.
|
|
* Warning Options:: How picky should the compiler be?
|
|
* Debugging Options:: Symbol tables, measurements, and debugging dumps.
|
|
* Optimize Options:: How much optimization?
|
|
* Preprocessor Options:: Controlling header files and macro definitions.
|
|
Also, getting dependency information for Make.
|
|
* Assembler Options:: Passing options to the assembler.
|
|
* Link Options:: Specifying libraries and so on.
|
|
* Directory Options:: Where to find header files and libraries.
|
|
Where to find the compiler executable files.
|
|
* Spec Files:: How to pass switches to sub-processes.
|
|
* Target Options:: Running a cross-compiler, or an old version of GCC.
|
|
@end menu
|
|
|
|
@node Overall Options
|
|
@section Options Controlling the Kind of Output
|
|
|
|
Compilation can involve up to four stages: preprocessing, compilation
|
|
proper, assembly and linking, always in that order. The first three
|
|
stages apply to an individual source file, and end by producing an
|
|
object file; linking combines all the object files (those newly
|
|
compiled, and those specified as input) into an executable file.
|
|
|
|
@cindex file name suffix
|
|
For any given input file, the file name suffix determines what kind of
|
|
compilation is done:
|
|
|
|
@table @gcctabopt
|
|
@item @var{file}.c
|
|
C source code which must be preprocessed.
|
|
|
|
@item @var{file}.i
|
|
C source code which should not be preprocessed.
|
|
|
|
@item @var{file}.ii
|
|
C++ source code which should not be preprocessed.
|
|
|
|
@item @var{file}.m
|
|
Objective-C source code. Note that you must link with the library
|
|
@file{libobjc.a} to make an Objective-C program work.
|
|
|
|
@item @var{file}.mi
|
|
Objective-C source code which should not be preprocessed.
|
|
|
|
@item @var{file}.h
|
|
C header file (not to be compiled or linked).
|
|
|
|
@item @var{file}.cc
|
|
@itemx @var{file}.cp
|
|
@itemx @var{file}.cxx
|
|
@itemx @var{file}.cpp
|
|
@itemx @var{file}.c++
|
|
@itemx @var{file}.C
|
|
C++ source code which must be preprocessed. Note that in @samp{.cxx},
|
|
the last two letters must both be literally @samp{x}. Likewise,
|
|
@samp{.C} refers to a literal capital C@.
|
|
|
|
@item @var{file}.f
|
|
@itemx @var{file}.for
|
|
@itemx @var{file}.FOR
|
|
Fortran source code which should not be preprocessed.
|
|
|
|
@item @var{file}.F
|
|
@itemx @var{file}.fpp
|
|
@itemx @var{file}.FPP
|
|
Fortran source code which must be preprocessed (with the traditional
|
|
preprocessor).
|
|
|
|
@item @var{file}.r
|
|
Fortran source code which must be preprocessed with a RATFOR
|
|
preprocessor (not included with GCC)@.
|
|
|
|
@xref{Overall Options,,Options Controlling the Kind of Output, g77,
|
|
Using and Porting GNU Fortran}, for more details of the handling of
|
|
Fortran input files.
|
|
|
|
@c FIXME: Descriptions of Java file types.
|
|
@c @var{file}.java
|
|
@c @var{file}.class
|
|
@c @var{file}.zip
|
|
@c @var{file}.jar
|
|
|
|
@item @var{file}.ads
|
|
Ada source code file which contains a library unit declaration (a
|
|
declaration of a package, subprogram, or generic, or a generic
|
|
instantiation), or a library unit renaming declaration (a package,
|
|
generic, or subprogram renaming declaration). Such files are also
|
|
called @dfn{specs}.
|
|
|
|
@itemx @var{file}.adb
|
|
Ada source code file containing a library unit body (a subprogram or
|
|
package body). Such files are also called @dfn{bodies}.
|
|
|
|
@c GCC also knows about some suffixes for languages not yet included:
|
|
@c Pascal:
|
|
@c @var{file}.p
|
|
@c @var{file}.pas
|
|
|
|
@item @var{file}.ch
|
|
@itemx @var{file}.chi
|
|
CHILL source code (preprocessed with the traditional preprocessor).
|
|
|
|
@item @var{file}.s
|
|
Assembler code.
|
|
|
|
@item @var{file}.S
|
|
Assembler code which must be preprocessed.
|
|
|
|
@item @var{other}
|
|
An object file to be fed straight into linking.
|
|
Any file name with no recognized suffix is treated this way.
|
|
@end table
|
|
|
|
@opindex x
|
|
You can specify the input language explicitly with the @option{-x} option:
|
|
|
|
@table @gcctabopt
|
|
@item -x @var{language}
|
|
Specify explicitly the @var{language} for the following input files
|
|
(rather than letting the compiler choose a default based on the file
|
|
name suffix). This option applies to all following input files until
|
|
the next @option{-x} option. Possible values for @var{language} are:
|
|
@example
|
|
c c-header cpp-output
|
|
c++ c++-cpp-output
|
|
objective-c objc-cpp-output
|
|
assembler assembler-with-cpp
|
|
ada
|
|
chill
|
|
f77 f77-cpp-input ratfor
|
|
java
|
|
@end example
|
|
|
|
@item -x none
|
|
Turn off any specification of a language, so that subsequent files are
|
|
handled according to their file name suffixes (as they are if @option{-x}
|
|
has not been used at all).
|
|
|
|
@item -pass-exit-codes
|
|
@opindex pass-exit-codes
|
|
Normally the @command{gcc} program will exit with the code of 1 if any
|
|
phase of the compiler returns a non-success return code. If you specify
|
|
@option{-pass-exit-codes}, the @command{gcc} program will instead return with
|
|
numerically highest error produced by any phase that returned an error
|
|
indication.
|
|
@end table
|
|
|
|
If you only want some of the stages of compilation, you can use
|
|
@option{-x} (or filename suffixes) to tell @command{gcc} where to start, and
|
|
one of the options @option{-c}, @option{-S}, or @option{-E} to say where
|
|
@command{gcc} is to stop. Note that some combinations (for example,
|
|
@samp{-x cpp-output -E}) instruct @command{gcc} to do nothing at all.
|
|
|
|
@table @gcctabopt
|
|
@item -c
|
|
@opindex c
|
|
Compile or assemble the source files, but do not link. The linking
|
|
stage simply is not done. The ultimate output is in the form of an
|
|
object file for each source file.
|
|
|
|
By default, the object file name for a source file is made by replacing
|
|
the suffix @samp{.c}, @samp{.i}, @samp{.s}, etc., with @samp{.o}.
|
|
|
|
Unrecognized input files, not requiring compilation or assembly, are
|
|
ignored.
|
|
|
|
@item -S
|
|
@opindex S
|
|
Stop after the stage of compilation proper; do not assemble. The output
|
|
is in the form of an assembler code file for each non-assembler input
|
|
file specified.
|
|
|
|
By default, the assembler file name for a source file is made by
|
|
replacing the suffix @samp{.c}, @samp{.i}, etc., with @samp{.s}.
|
|
|
|
Input files that don't require compilation are ignored.
|
|
|
|
@item -E
|
|
@opindex E
|
|
Stop after the preprocessing stage; do not run the compiler proper. The
|
|
output is in the form of preprocessed source code, which is sent to the
|
|
standard output.
|
|
|
|
Input files which don't require preprocessing are ignored.
|
|
|
|
@cindex output file option
|
|
@item -o @var{file}
|
|
@opindex o
|
|
Place output in file @var{file}. This applies regardless to whatever
|
|
sort of output is being produced, whether it be an executable file,
|
|
an object file, an assembler file or preprocessed C code.
|
|
|
|
Since only one output file can be specified, it does not make sense to
|
|
use @option{-o} when compiling more than one input file, unless you are
|
|
producing an executable file as output.
|
|
|
|
If @option{-o} is not specified, the default is to put an executable file
|
|
in @file{a.out}, the object file for @file{@var{source}.@var{suffix}} in
|
|
@file{@var{source}.o}, its assembler file in @file{@var{source}.s}, and
|
|
all preprocessed C source on standard output.
|
|
|
|
@item -v
|
|
@opindex v
|
|
Print (on standard error output) the commands executed to run the stages
|
|
of compilation. Also print the version number of the compiler driver
|
|
program and of the preprocessor and the compiler proper.
|
|
|
|
@item -pipe
|
|
@opindex pipe
|
|
Use pipes rather than temporary files for communication between the
|
|
various stages of compilation. This fails to work on some systems where
|
|
the assembler is unable to read from a pipe; but the GNU assembler has
|
|
no trouble.
|
|
|
|
@item --help
|
|
@opindex help
|
|
Print (on the standard output) a description of the command line options
|
|
understood by @command{gcc}. If the @option{-v} option is also specified
|
|
then @option{--help} will also be passed on to the various processes
|
|
invoked by @command{gcc}, so that they can display the command line options
|
|
they accept. If the @option{-W} option is also specified then command
|
|
line options which have no documentation associated with them will also
|
|
be displayed.
|
|
|
|
@item --target-help
|
|
@opindex target-help
|
|
Print (on the standard output) a description of target specific command
|
|
line options for each tool.
|
|
@end table
|
|
|
|
@node Invoking G++
|
|
@section Compiling C++ Programs
|
|
|
|
@cindex suffixes for C++ source
|
|
@cindex C++ source file suffixes
|
|
C++ source files conventionally use one of the suffixes @samp{.C},
|
|
@samp{.cc}, @samp{.cpp}, @samp{.c++}, @samp{.cp}, or @samp{.cxx};
|
|
preprocessed C++ files use the suffix @samp{.ii}. GCC recognizes
|
|
files with these names and compiles them as C++ programs even if you
|
|
call the compiler the same way as for compiling C programs (usually with
|
|
the name @command{gcc}).
|
|
|
|
@findex g++
|
|
@findex c++
|
|
However, C++ programs often require class libraries as well as a
|
|
compiler that understands the C++ language---and under some
|
|
circumstances, you might want to compile programs from standard input,
|
|
or otherwise without a suffix that flags them as C++ programs.
|
|
@command{g++} is a program that calls GCC with the default language
|
|
set to C++, and automatically specifies linking against the C++
|
|
library. On many systems, @command{g++} is also
|
|
installed with the name @command{c++}.
|
|
|
|
@cindex invoking @command{g++}
|
|
When you compile C++ programs, you may specify many of the same
|
|
command-line options that you use for compiling programs in any
|
|
language; or command-line options meaningful for C and related
|
|
languages; or options that are meaningful only for C++ programs.
|
|
@xref{C Dialect Options,,Options Controlling C Dialect}, for
|
|
explanations of options for languages related to C@.
|
|
@xref{C++ Dialect Options,,Options Controlling C++ Dialect}, for
|
|
explanations of options that are meaningful only for C++ programs.
|
|
|
|
@node C Dialect Options
|
|
@section Options Controlling C Dialect
|
|
@cindex dialect options
|
|
@cindex language dialect options
|
|
@cindex options, dialect
|
|
|
|
The following options control the dialect of C (or languages derived
|
|
from C, such as C++ and Objective-C) that the compiler accepts:
|
|
|
|
@table @gcctabopt
|
|
@cindex ANSI support
|
|
@cindex ISO support
|
|
@item -ansi
|
|
@opindex ansi
|
|
In C mode, support all ISO C89 programs. In C++ mode,
|
|
remove GNU extensions that conflict with ISO C++.
|
|
|
|
This turns off certain features of GCC that are incompatible with ISO
|
|
C89 (when compiling C code), or of standard C++ (when compiling C++ code),
|
|
such as the @code{asm} and @code{typeof} keywords, and
|
|
predefined macros such as @code{unix} and @code{vax} that identify the
|
|
type of system you are using. It also enables the undesirable and
|
|
rarely used ISO trigraph feature. For the C compiler,
|
|
it disables recognition of C++ style @samp{//} comments as well as
|
|
the @code{inline} keyword.
|
|
|
|
The alternate keywords @code{__asm__}, @code{__extension__},
|
|
@code{__inline__} and @code{__typeof__} continue to work despite
|
|
@option{-ansi}. You would not want to use them in an ISO C program, of
|
|
course, but it is useful to put them in header files that might be included
|
|
in compilations done with @option{-ansi}. Alternate predefined macros
|
|
such as @code{__unix__} and @code{__vax__} are also available, with or
|
|
without @option{-ansi}.
|
|
|
|
The @option{-ansi} option does not cause non-ISO programs to be
|
|
rejected gratuitously. For that, @option{-pedantic} is required in
|
|
addition to @option{-ansi}. @xref{Warning Options}.
|
|
|
|
The macro @code{__STRICT_ANSI__} is predefined when the @option{-ansi}
|
|
option is used. Some header files may notice this macro and refrain
|
|
from declaring certain functions or defining certain macros that the
|
|
ISO standard doesn't call for; this is to avoid interfering with any
|
|
programs that might use these names for other things.
|
|
|
|
Functions which would normally be built in but do not have semantics
|
|
defined by ISO C (such as @code{alloca} and @code{ffs}) are not built-in
|
|
functions with @option{-ansi} is used. @xref{Other Builtins,,Other
|
|
built-in functions provided by GCC}, for details of the functions
|
|
affected.
|
|
|
|
@item -std=
|
|
@opindex std
|
|
Determine the language standard. This option is currently only
|
|
supported when compiling C@. A value for this option must be provided;
|
|
possible values are
|
|
|
|
@table @samp
|
|
@item c89
|
|
@itemx iso9899:1990
|
|
ISO C89 (same as @option{-ansi}).
|
|
|
|
@item iso9899:199409
|
|
ISO C89 as modified in amendment 1.
|
|
|
|
@item c99
|
|
@itemx c9x
|
|
@itemx iso9899:1999
|
|
@itemx iso9899:199x
|
|
ISO C99. Note that this standard is not yet fully supported; see
|
|
@w{@uref{http://gcc.gnu.org/c99status.html}} for more information. The
|
|
names @samp{c9x} and @samp{iso9899:199x} are deprecated.
|
|
|
|
@item gnu89
|
|
Default, ISO C89 plus GNU extensions (including some C99 features).
|
|
|
|
@item gnu99
|
|
@item gnu9x
|
|
ISO C99 plus GNU extensions. When ISO C99 is fully implemented in GCC,
|
|
this will become the default. The name @samp{gnu9x} is deprecated.
|
|
|
|
@end table
|
|
|
|
Even when this option is not specified, you can still use some of the
|
|
features of newer standards in so far as they do not conflict with
|
|
previous C standards. For example, you may use @code{__restrict__} even
|
|
when @option{-std=c99} is not specified.
|
|
|
|
The @option{-std} options specifying some version of ISO C have the same
|
|
effects as @option{-ansi}, except that features that were not in ISO C89
|
|
but are in the specified version (for example, @samp{//} comments and
|
|
the @code{inline} keyword in ISO C99) are not disabled.
|
|
|
|
@xref{Standards,,Language Standards Supported by GCC}, for details of
|
|
these standard versions.
|
|
|
|
@item -aux-info @var{filename}
|
|
@opindex aux-info
|
|
Output to the given filename prototyped declarations for all functions
|
|
declared and/or defined in a translation unit, including those in header
|
|
files. This option is silently ignored in any language other than C@.
|
|
|
|
Besides declarations, the file indicates, in comments, the origin of
|
|
each declaration (source file and line), whether the declaration was
|
|
implicit, prototyped or unprototyped (@samp{I}, @samp{N} for new or
|
|
@samp{O} for old, respectively, in the first character after the line
|
|
number and the colon), and whether it came from a declaration or a
|
|
definition (@samp{C} or @samp{F}, respectively, in the following
|
|
character). In the case of function definitions, a K&R-style list of
|
|
arguments followed by their declarations is also provided, inside
|
|
comments, after the declaration.
|
|
|
|
@item -fno-asm
|
|
@opindex fno-asm
|
|
Do not recognize @code{asm}, @code{inline} or @code{typeof} as a
|
|
keyword, so that code can use these words as identifiers. You can use
|
|
the keywords @code{__asm__}, @code{__inline__} and @code{__typeof__}
|
|
instead. @option{-ansi} implies @option{-fno-asm}.
|
|
|
|
In C++, this switch only affects the @code{typeof} keyword, since
|
|
@code{asm} and @code{inline} are standard keywords. You may want to
|
|
use the @option{-fno-gnu-keywords} flag instead, which has the same
|
|
effect. In C99 mode (@option{-std=c99} or @option{-std=gnu99}), this
|
|
switch only affects the @code{asm} and @code{typeof} keywords, since
|
|
@code{inline} is a standard keyword in ISO C99.
|
|
|
|
@item -fno-builtin
|
|
@itemx -fno-builtin-@var{function} @r{(C and Objective-C only)}
|
|
@opindex fno-builtin
|
|
@cindex built-in functions
|
|
Don't recognize built-in functions that do not begin with
|
|
@samp{__builtin_} as prefix. @xref{Other Builtins,,Other built-in
|
|
functions provided by GCC}, for details of the functions affected,
|
|
including those which are not built-in functions when @option{-ansi} or
|
|
@option{-std} options for strict ISO C conformance are used because they
|
|
do not have an ISO standard meaning.
|
|
|
|
GCC normally generates special code to handle certain built-in functions
|
|
more efficiently; for instance, calls to @code{alloca} may become single
|
|
instructions that adjust the stack directly, and calls to @code{memcpy}
|
|
may become inline copy loops. The resulting code is often both smaller
|
|
and faster, but since the function calls no longer appear as such, you
|
|
cannot set a breakpoint on those calls, nor can you change the behavior
|
|
of the functions by linking with a different library.
|
|
|
|
In C++, @option{-fno-builtin} is always in effect. The @option{-fbuiltin}
|
|
option has no effect. Therefore, in C++, the only way to get the
|
|
optimization benefits of built-in functions is to call the function
|
|
using the @samp{__builtin_} prefix. The GNU C++ Standard Library uses
|
|
built-in functions to implement many functions (like
|
|
@code{std::strchr}), so that you automatically get efficient code.
|
|
|
|
With the @option{-fno-builtin-@var{function}} option, not available
|
|
when compiling C++, only the built-in function @var{function} is
|
|
disabled. @var{function} must not begin with @samp{__builtin_}. If a
|
|
function is named this is not built-in in this version of GCC, this
|
|
option is ignored. There is no corresponding
|
|
@option{-fbuiltin-@var{function}} option; if you wish to enable
|
|
built-in functions selectively when using @option{-fno-builtin} or
|
|
@option{-ffreestanding}, you may define macros such as:
|
|
|
|
@smallexample
|
|
#define abs(n) __builtin_abs ((n))
|
|
#define strcpy(d, s) __builtin_strcpy ((d), (s))
|
|
@end smallexample
|
|
|
|
@item -fhosted
|
|
@opindex fhosted
|
|
@cindex hosted environment
|
|
|
|
Assert that compilation takes place in a hosted environment. This implies
|
|
@option{-fbuiltin}. A hosted environment is one in which the
|
|
entire standard library is available, and in which @code{main} has a return
|
|
type of @code{int}. Examples are nearly everything except a kernel.
|
|
This is equivalent to @option{-fno-freestanding}.
|
|
|
|
@item -ffreestanding
|
|
@opindex ffreestanding
|
|
@cindex hosted environment
|
|
|
|
Assert that compilation takes place in a freestanding environment. This
|
|
implies @option{-fno-builtin}. A freestanding environment
|
|
is one in which the standard library may not exist, and program startup may
|
|
not necessarily be at @code{main}. The most obvious example is an OS kernel.
|
|
This is equivalent to @option{-fno-hosted}.
|
|
|
|
@xref{Standards,,Language Standards Supported by GCC}, for details of
|
|
freestanding and hosted environments.
|
|
|
|
@item -trigraphs
|
|
@opindex trigraphs
|
|
Support ISO C trigraphs. The @option{-ansi} option (and @option{-std}
|
|
options for strict ISO C conformance) implies @option{-trigraphs}.
|
|
|
|
@cindex traditional C language
|
|
@cindex C language, traditional
|
|
@item -traditional
|
|
@opindex traditional
|
|
Attempt to support some aspects of traditional C compilers.
|
|
Specifically:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
All @code{extern} declarations take effect globally even if they
|
|
are written inside of a function definition. This includes implicit
|
|
declarations of functions.
|
|
|
|
@item
|
|
The newer keywords @code{typeof}, @code{inline}, @code{signed}, @code{const}
|
|
and @code{volatile} are not recognized. (You can still use the
|
|
alternative keywords such as @code{__typeof__}, @code{__inline__}, and
|
|
so on.)
|
|
|
|
@item
|
|
Comparisons between pointers and integers are always allowed.
|
|
|
|
@item
|
|
Integer types @code{unsigned short} and @code{unsigned char} promote
|
|
to @code{unsigned int}.
|
|
|
|
@item
|
|
Out-of-range floating point literals are not an error.
|
|
|
|
@item
|
|
Certain constructs which ISO regards as a single invalid preprocessing
|
|
number, such as @samp{0xe-0xd}, are treated as expressions instead.
|
|
|
|
@item
|
|
String ``constants'' are not necessarily constant; they are stored in
|
|
writable space, and identical looking constants are allocated
|
|
separately. (This is the same as the effect of
|
|
@option{-fwritable-strings}.)
|
|
|
|
@cindex @code{longjmp} and automatic variables
|
|
@item
|
|
All automatic variables not declared @code{register} are preserved by
|
|
@code{longjmp}. Ordinarily, GNU C follows ISO C: automatic variables
|
|
not declared @code{volatile} may be clobbered.
|
|
|
|
@item
|
|
@cindex @samp{\x}
|
|
@cindex @samp{\a}
|
|
@cindex escape sequences, traditional
|
|
The character escape sequences @samp{\x} and @samp{\a} evaluate as the
|
|
literal characters @samp{x} and @samp{a} respectively. Without
|
|
@w{@option{-traditional}}, @samp{\x} is a prefix for the hexadecimal
|
|
representation of a character, and @samp{\a} produces a bell.
|
|
@end itemize
|
|
|
|
This option is deprecated and may be removed.
|
|
|
|
You may wish to use @option{-fno-builtin} as well as @option{-traditional}
|
|
if your program uses names that are normally GNU C built-in functions for
|
|
other purposes of its own.
|
|
|
|
You cannot use @option{-traditional} if you include any header files that
|
|
rely on ISO C features. Some vendors are starting to ship systems with
|
|
ISO C header files and you cannot use @option{-traditional} on such
|
|
systems to compile files that include any system headers.
|
|
|
|
The @option{-traditional} option also enables @option{-traditional-cpp}.
|
|
|
|
@item -traditional-cpp
|
|
@opindex traditional-cpp
|
|
Attempt to support some aspects of traditional C preprocessors.
|
|
See the GNU CPP manual for details.
|
|
|
|
@item -fcond-mismatch
|
|
@opindex fcond-mismatch
|
|
Allow conditional expressions with mismatched types in the second and
|
|
third arguments. The value of such an expression is void. This option
|
|
is not supported for C++.
|
|
|
|
@item -funsigned-char
|
|
@opindex funsigned-char
|
|
Let the type @code{char} be unsigned, like @code{unsigned char}.
|
|
|
|
Each kind of machine has a default for what @code{char} should
|
|
be. It is either like @code{unsigned char} by default or like
|
|
@code{signed char} by default.
|
|
|
|
Ideally, a portable program should always use @code{signed char} or
|
|
@code{unsigned char} when it depends on the signedness of an object.
|
|
But many programs have been written to use plain @code{char} and
|
|
expect it to be signed, or expect it to be unsigned, depending on the
|
|
machines they were written for. This option, and its inverse, let you
|
|
make such a program work with the opposite default.
|
|
|
|
The type @code{char} is always a distinct type from each of
|
|
@code{signed char} or @code{unsigned char}, even though its behavior
|
|
is always just like one of those two.
|
|
|
|
@item -fsigned-char
|
|
@opindex fsigned-char
|
|
Let the type @code{char} be signed, like @code{signed char}.
|
|
|
|
Note that this is equivalent to @option{-fno-unsigned-char}, which is
|
|
the negative form of @option{-funsigned-char}. Likewise, the option
|
|
@option{-fno-signed-char} is equivalent to @option{-funsigned-char}.
|
|
|
|
@item -fsigned-bitfields
|
|
@itemx -funsigned-bitfields
|
|
@itemx -fno-signed-bitfields
|
|
@itemx -fno-unsigned-bitfields
|
|
@opindex fsigned-bitfields
|
|
@opindex funsigned-bitfields
|
|
@opindex fno-signed-bitfields
|
|
@opindex fno-unsigned-bitfields
|
|
These options control whether a bit-field is signed or unsigned, when the
|
|
declaration does not use either @code{signed} or @code{unsigned}. By
|
|
default, such a bit-field is signed, because this is consistent: the
|
|
basic integer types such as @code{int} are signed types.
|
|
|
|
However, when @option{-traditional} is used, bit-fields are all unsigned
|
|
no matter what.
|
|
|
|
@item -fwritable-strings
|
|
@opindex fwritable-strings
|
|
Store string constants in the writable data segment and don't uniquize
|
|
them. This is for compatibility with old programs which assume they can
|
|
write into string constants. The option @option{-traditional} also has
|
|
this effect.
|
|
|
|
Writing into string constants is a very bad idea; ``constants'' should
|
|
be constant.
|
|
|
|
@item -fallow-single-precision
|
|
@opindex fallow-single-precision
|
|
Do not promote single precision math operations to double precision,
|
|
even when compiling with @option{-traditional}.
|
|
|
|
Traditional K&R C promotes all floating point operations to double
|
|
precision, regardless of the sizes of the operands. On the
|
|
architecture for which you are compiling, single precision may be faster
|
|
than double precision. If you must use @option{-traditional}, but want
|
|
to use single precision operations when the operands are single
|
|
precision, use this option. This option has no effect when compiling
|
|
with ISO or GNU C conventions (the default).
|
|
|
|
@item -fshort-wchar
|
|
@opindex fshort-wchar
|
|
Override the underlying type for @samp{wchar_t} to be @samp{short
|
|
unsigned int} instead of the default for the target. This option is
|
|
useful for building programs to run under WINE@.
|
|
@end table
|
|
|
|
@node C++ Dialect Options
|
|
@section Options Controlling C++ Dialect
|
|
|
|
@cindex compiler options, C++
|
|
@cindex C++ options, command line
|
|
@cindex options, C++
|
|
This section describes the command-line options that are only meaningful
|
|
for C++ programs; but you can also use most of the GNU compiler options
|
|
regardless of what language your program is in. For example, you
|
|
might compile a file @code{firstClass.C} like this:
|
|
|
|
@example
|
|
g++ -g -frepo -O -c firstClass.C
|
|
@end example
|
|
|
|
@noindent
|
|
In this example, only @option{-frepo} is an option meant
|
|
only for C++ programs; you can use the other options with any
|
|
language supported by GCC@.
|
|
|
|
Here is a list of options that are @emph{only} for compiling C++ programs:
|
|
|
|
@table @gcctabopt
|
|
@item -fno-access-control
|
|
@opindex fno-access-control
|
|
Turn off all access checking. This switch is mainly useful for working
|
|
around bugs in the access control code.
|
|
|
|
@item -fcheck-new
|
|
@opindex fcheck-new
|
|
Check that the pointer returned by @code{operator new} is non-null
|
|
before attempting to modify the storage allocated. The current Working
|
|
Paper requires that @code{operator new} never return a null pointer, so
|
|
this check is normally unnecessary.
|
|
|
|
An alternative to using this option is to specify that your
|
|
@code{operator new} does not throw any exceptions; if you declare it
|
|
@samp{throw()}, G++ will check the return value. See also @samp{new
|
|
(nothrow)}.
|
|
|
|
@item -fconserve-space
|
|
@opindex fconserve-space
|
|
Put uninitialized or runtime-initialized global variables into the
|
|
common segment, as C does. This saves space in the executable at the
|
|
cost of not diagnosing duplicate definitions. If you compile with this
|
|
flag and your program mysteriously crashes after @code{main()} has
|
|
completed, you may have an object that is being destroyed twice because
|
|
two definitions were merged.
|
|
|
|
This option is no longer useful on most targets, now that support has
|
|
been added for putting variables into BSS without making them common.
|
|
|
|
@item -fno-const-strings
|
|
@opindex fno-const-strings
|
|
Give string constants type @code{char *} instead of type @code{const
|
|
char *}. By default, G++ uses type @code{const char *} as required by
|
|
the standard. Even if you use @option{-fno-const-strings}, you cannot
|
|
actually modify the value of a string constant, unless you also use
|
|
@option{-fwritable-strings}.
|
|
|
|
This option might be removed in a future release of G++. For maximum
|
|
portability, you should structure your code so that it works with
|
|
string constants that have type @code{const char *}.
|
|
|
|
@item -fdollars-in-identifiers
|
|
@opindex fdollars-in-identifiers
|
|
Accept @samp{$} in identifiers. You can also explicitly prohibit use of
|
|
@samp{$} with the option @option{-fno-dollars-in-identifiers}. (GNU C allows
|
|
@samp{$} by default on most target systems, but there are a few exceptions.)
|
|
Traditional C allowed the character @samp{$} to form part of
|
|
identifiers. However, ISO C and C++ forbid @samp{$} in identifiers.
|
|
|
|
@item -fno-elide-constructors
|
|
@opindex fno-elide-constructors
|
|
The C++ standard allows an implementation to omit creating a temporary
|
|
which is only used to initialize another object of the same type.
|
|
Specifying this option disables that optimization, and forces G++ to
|
|
call the copy constructor in all cases.
|
|
|
|
@item -fno-enforce-eh-specs
|
|
@opindex fno-enforce-eh-specs
|
|
Don't check for violation of exception specifications at runtime. This
|
|
option violates the C++ standard, but may be useful for reducing code
|
|
size in production builds, much like defining @samp{NDEBUG}. The compiler
|
|
will still optimize based on the exception specifications.
|
|
|
|
@item -fexternal-templates
|
|
@opindex fexternal-templates
|
|
|
|
Cause @samp{#pragma interface} and @samp{implementation} to apply to
|
|
template instantiation; template instances are emitted or not according
|
|
to the location of the template definition. @xref{Template
|
|
Instantiation}, for more information.
|
|
|
|
This option is deprecated.
|
|
|
|
@item -falt-external-templates
|
|
@opindex falt-external-templates
|
|
Similar to @option{-fexternal-templates}, but template instances are
|
|
emitted or not according to the place where they are first instantiated.
|
|
@xref{Template Instantiation}, for more information.
|
|
|
|
This option is deprecated.
|
|
|
|
@item -ffor-scope
|
|
@itemx -fno-for-scope
|
|
@opindex ffor-scope
|
|
@opindex fno-for-scope
|
|
If @option{-ffor-scope} is specified, the scope of variables declared in
|
|
a @i{for-init-statement} is limited to the @samp{for} loop itself,
|
|
as specified by the C++ standard.
|
|
If @option{-fno-for-scope} is specified, the scope of variables declared in
|
|
a @i{for-init-statement} extends to the end of the enclosing scope,
|
|
as was the case in old versions of G++, and other (traditional)
|
|
implementations of C++.
|
|
|
|
The default if neither flag is given to follow the standard,
|
|
but to allow and give a warning for old-style code that would
|
|
otherwise be invalid, or have different behavior.
|
|
|
|
@item -fno-gnu-keywords
|
|
@opindex fno-gnu-keywords
|
|
Do not recognize @code{typeof} as a keyword, so that code can use this
|
|
word as an identifier. You can use the keyword @code{__typeof__} instead.
|
|
@option{-ansi} implies @option{-fno-gnu-keywords}.
|
|
|
|
@item -fno-implicit-templates
|
|
@opindex fno-implicit-templates
|
|
Never emit code for non-inline templates which are instantiated
|
|
implicitly (i.e.@: by use); only emit code for explicit instantiations.
|
|
@xref{Template Instantiation}, for more information.
|
|
|
|
@item -fno-implicit-inline-templates
|
|
@opindex fno-implicit-inline-templates
|
|
Don't emit code for implicit instantiations of inline templates, either.
|
|
The default is to handle inlines differently so that compiles with and
|
|
without optimization will need the same set of explicit instantiations.
|
|
|
|
@item -fno-implement-inlines
|
|
@opindex fno-implement-inlines
|
|
To save space, do not emit out-of-line copies of inline functions
|
|
controlled by @samp{#pragma implementation}. This will cause linker
|
|
errors if these functions are not inlined everywhere they are called.
|
|
|
|
@item -fms-extensions
|
|
@opindex fms-extensions
|
|
Disable pedantic warnings about constructs used in MFC, such as implicit
|
|
int and getting a pointer to member function via non-standard syntax.
|
|
|
|
@item -fno-nonansi-builtins
|
|
@opindex fno-nonansi-builtins
|
|
Disable built-in declarations of functions that are not mandated by
|
|
ANSI/ISO C@. These include @code{ffs}, @code{alloca}, @code{_exit},
|
|
@code{index}, @code{bzero}, @code{conjf}, and other related functions.
|
|
|
|
@item -fno-operator-names
|
|
@opindex fno-operator-names
|
|
Do not treat the operator name keywords @code{and}, @code{bitand},
|
|
@code{bitor}, @code{compl}, @code{not}, @code{or} and @code{xor} as
|
|
synonyms as keywords.
|
|
|
|
@item -fno-optional-diags
|
|
@opindex fno-optional-diags
|
|
Disable diagnostics that the standard says a compiler does not need to
|
|
issue. Currently, the only such diagnostic issued by G++ is the one for
|
|
a name having multiple meanings within a class.
|
|
|
|
@item -fpermissive
|
|
@opindex fpermissive
|
|
Downgrade messages about nonconformant code from errors to warnings. By
|
|
default, G++ effectively sets @option{-pedantic-errors} without
|
|
@option{-pedantic}; this option reverses that. This behavior and this
|
|
option are superseded by @option{-pedantic}, which works as it does for GNU C@.
|
|
|
|
@item -frepo
|
|
@opindex frepo
|
|
Enable automatic template instantiation at link time. This option also
|
|
implies @option{-fno-implicit-templates}. @xref{Template
|
|
Instantiation}, for more information.
|
|
|
|
@item -fno-rtti
|
|
@opindex fno-rtti
|
|
Disable generation of information about every class with virtual
|
|
functions for use by the C++ runtime type identification features
|
|
(@samp{dynamic_cast} and @samp{typeid}). If you don't use those parts
|
|
of the language, you can save some space by using this flag. Note that
|
|
exception handling uses the same information, but it will generate it as
|
|
needed.
|
|
|
|
@item -fstats
|
|
@opindex fstats
|
|
Emit statistics about front-end processing at the end of the compilation.
|
|
This information is generally only useful to the G++ development team.
|
|
|
|
@item -ftemplate-depth-@var{n}
|
|
@opindex ftemplate-depth
|
|
Set the maximum instantiation depth for template classes to @var{n}.
|
|
A limit on the template instantiation depth is needed to detect
|
|
endless recursions during template class instantiation. ANSI/ISO C++
|
|
conforming programs must not rely on a maximum depth greater than 17.
|
|
|
|
@item -fuse-cxa-atexit
|
|
@opindex fuse-cxa-atexit
|
|
Register destructors for objects with static storage duration with the
|
|
@code{__cxa_atexit} function rather than the @code{atexit} function.
|
|
This option is required for fully standards-compliant handling of static
|
|
destructors, but will only work if your C library supports
|
|
@code{__cxa_atexit}.
|
|
|
|
@item -fvtable-gc
|
|
@opindex fvtable-gc
|
|
Emit special relocations for vtables and virtual function references
|
|
so that the linker can identify unused virtual functions and zero out
|
|
vtable slots that refer to them. This is most useful with
|
|
@option{-ffunction-sections} and @option{-Wl,--gc-sections}, in order to
|
|
also discard the functions themselves.
|
|
|
|
This optimization requires GNU as and GNU ld. Not all systems support
|
|
this option. @option{-Wl,--gc-sections} is ignored without @option{-static}.
|
|
|
|
@item -fno-weak
|
|
@opindex fno-weak
|
|
Do not use weak symbol support, even if it is provided by the linker.
|
|
By default, G++ will use weak symbols if they are available. This
|
|
option exists only for testing, and should not be used by end-users;
|
|
it will result in inferior code and has no benefits. This option may
|
|
be removed in a future release of G++.
|
|
|
|
@item -nostdinc++
|
|
@opindex nostdinc++
|
|
Do not search for header files in the standard directories specific to
|
|
C++, but do still search the other standard directories. (This option
|
|
is used when building the C++ library.)
|
|
@end table
|
|
|
|
In addition, these optimization, warning, and code generation options
|
|
have meanings only for C++ programs:
|
|
|
|
@table @gcctabopt
|
|
@item -fno-default-inline
|
|
@opindex fno-default-inline
|
|
Do not assume @samp{inline} for functions defined inside a class scope.
|
|
@xref{Optimize Options,,Options That Control Optimization}. Note that these
|
|
functions will have linkage like inline functions; they just won't be
|
|
inlined by default.
|
|
|
|
@item -Wctor-dtor-privacy @r{(C++ only)}
|
|
@opindex Wctor-dtor-privacy
|
|
Warn when a class seems unusable, because all the constructors or
|
|
destructors in a class are private and the class has no friends or
|
|
public static member functions.
|
|
|
|
@item -Wnon-virtual-dtor @r{(C++ only)}
|
|
@opindex Wnon-virtual-dtor
|
|
Warn when a class declares a non-virtual destructor that should probably
|
|
be virtual, because it looks like the class will be used polymorphically.
|
|
|
|
@item -Wreorder @r{(C++ only)}
|
|
@opindex Wreorder
|
|
@cindex reordering, warning
|
|
@cindex warning for reordering of member initializers
|
|
Warn when the order of member initializers given in the code does not
|
|
match the order in which they must be executed. For instance:
|
|
|
|
@smallexample
|
|
struct A @{
|
|
int i;
|
|
int j;
|
|
A(): j (0), i (1) @{ @}
|
|
@};
|
|
@end smallexample
|
|
|
|
Here the compiler will warn that the member initializers for @samp{i}
|
|
and @samp{j} will be rearranged to match the declaration order of the
|
|
members.
|
|
@end table
|
|
|
|
The following @option{-W@dots{}} options are not affected by @option{-Wall}.
|
|
|
|
@table @gcctabopt
|
|
@item -Weffc++ @r{(C++ only)}
|
|
@opindex Weffc++
|
|
Warn about violations of various style guidelines from Scott Meyers'
|
|
@cite{Effective C++} books. If you use this option, you should be aware
|
|
that the standard library headers do not obey all of these guidelines;
|
|
you can use @samp{grep -v} to filter out those warnings.
|
|
|
|
@item -Wno-deprecated @r{(C++ only)}
|
|
@opindex Wno-deprecated
|
|
Do not warn about usage of deprecated features. @xref{Deprecated Features}.
|
|
|
|
@item -Wno-non-template-friend @r{(C++ only)}
|
|
@opindex Wno-non-template-friend
|
|
Disable warnings when non-templatized friend functions are declared
|
|
within a template. With the advent of explicit template specification
|
|
support in G++, if the name of the friend is an unqualified-id (i.e.,
|
|
@samp{friend foo(int)}), the C++ language specification demands that the
|
|
friend declare or define an ordinary, nontemplate function. (Section
|
|
14.5.3). Before G++ implemented explicit specification, unqualified-ids
|
|
could be interpreted as a particular specialization of a templatized
|
|
function. Because this non-conforming behavior is no longer the default
|
|
behavior for G++, @option{-Wnon-template-friend} allows the compiler to
|
|
check existing code for potential trouble spots, and is on by default.
|
|
This new compiler behavior can be turned off with
|
|
@option{-Wno-non-template-friend} which keeps the conformant compiler code
|
|
but disables the helpful warning.
|
|
|
|
@item -Wold-style-cast @r{(C++ only)}
|
|
@opindex Wold-style-cast
|
|
Warn if an old-style (C-style) cast to a non-void type is used within
|
|
a C++ program. The new-style casts (@samp{static_cast},
|
|
@samp{reinterpret_cast}, and @samp{const_cast}) are less vulnerable to
|
|
unintended effects, and much easier to grep for.
|
|
|
|
@item -Woverloaded-virtual @r{(C++ only)}
|
|
@opindex Woverloaded-virtual
|
|
@cindex overloaded virtual fn, warning
|
|
@cindex warning for overloaded virtual fn
|
|
Warn when a function declaration hides virtual functions from a
|
|
base class. For example, in:
|
|
|
|
@smallexample
|
|
struct A @{
|
|
virtual void f();
|
|
@};
|
|
|
|
struct B: public A @{
|
|
void f(int);
|
|
@};
|
|
@end smallexample
|
|
|
|
the @code{A} class version of @code{f} is hidden in @code{B}, and code
|
|
like this:
|
|
|
|
@smallexample
|
|
B* b;
|
|
b->f();
|
|
@end smallexample
|
|
|
|
will fail to compile.
|
|
|
|
@item -Wno-pmf-conversions @r{(C++ only)}
|
|
@opindex Wno-pmf-conversions
|
|
Disable the diagnostic for converting a bound pointer to member function
|
|
to a plain pointer.
|
|
|
|
@item -Wsign-promo @r{(C++ only)}
|
|
@opindex Wsign-promo
|
|
Warn when overload resolution chooses a promotion from unsigned or
|
|
enumeral type to a signed type over a conversion to an unsigned type of
|
|
the same size. Previous versions of G++ would try to preserve
|
|
unsignedness, but the standard mandates the current behavior.
|
|
|
|
@item -Wsynth @r{(C++ only)}
|
|
@opindex Wsynth
|
|
@cindex warning for synthesized methods
|
|
@cindex synthesized methods, warning
|
|
Warn when G++'s synthesis behavior does not match that of cfront. For
|
|
instance:
|
|
|
|
@smallexample
|
|
struct A @{
|
|
operator int ();
|
|
A& operator = (int);
|
|
@};
|
|
|
|
main ()
|
|
@{
|
|
A a,b;
|
|
a = b;
|
|
@}
|
|
@end smallexample
|
|
|
|
In this example, G++ will synthesize a default @samp{A& operator =
|
|
(const A&);}, while cfront will use the user-defined @samp{operator =}.
|
|
@end table
|
|
|
|
@node Objective-C Dialect Options
|
|
@section Options Controlling Objective-C Dialect
|
|
|
|
@cindex compiler options, Objective-C
|
|
@cindex Objective-C options, command line
|
|
@cindex options, Objective-C
|
|
This section describes the command-line options that are only meaningful
|
|
for Objective-C programs; but you can also use most of the GNU compiler
|
|
options regardless of what language your program is in. For example,
|
|
you might compile a file @code{some_class.m} like this:
|
|
|
|
@example
|
|
gcc -g -fgnu-runtime -O -c some_class.m
|
|
@end example
|
|
|
|
@noindent
|
|
In this example, only @option{-fgnu-runtime} is an option meant only for
|
|
Objective-C programs; you can use the other options with any language
|
|
supported by GCC@.
|
|
|
|
Here is a list of options that are @emph{only} for compiling Objective-C
|
|
programs:
|
|
|
|
@table @gcctabopt
|
|
@item -fconstant-string-class=@var{class-name}
|
|
@opindex fconstant-string-class
|
|
Use @var{class-name} as the name of the class to instantiate for each
|
|
literal string specified with the syntax @code{@@"@dots{}"}. The default
|
|
class name is @code{NXConstantString}.
|
|
|
|
@item -fgnu-runtime
|
|
@opindex fgnu-runtime
|
|
Generate object code compatible with the standard GNU Objective-C
|
|
runtime. This is the default for most types of systems.
|
|
|
|
@item -fnext-runtime
|
|
@opindex fnext-runtime
|
|
Generate output compatible with the NeXT runtime. This is the default
|
|
for NeXT-based systems, including Darwin and Mac OS X@.
|
|
|
|
@item -gen-decls
|
|
@opindex gen-decls
|
|
Dump interface declarations for all classes seen in the source file to a
|
|
file named @file{@var{sourcename}.decl}.
|
|
|
|
@item -Wno-protocol
|
|
@opindex Wno-protocol
|
|
Do not warn if methods required by a protocol are not implemented
|
|
in the class adopting it.
|
|
|
|
@item -Wselector
|
|
@opindex Wselector
|
|
Warn if a selector has multiple methods of different types defined.
|
|
|
|
@c not documented because only avail via -Wp
|
|
@c @item -print-objc-runtime-info
|
|
|
|
@end table
|
|
|
|
@node Language Independent Options
|
|
@section Options to Control Diagnostic Messages Formatting
|
|
@cindex options to control diagnostics formatting
|
|
@cindex diagnostic messages
|
|
@cindex message formatting
|
|
|
|
Traditionally, diagnostic messages have been formatted irrespective of
|
|
the output device's aspect (e.g.@: its width, @dots{}). The options described
|
|
below can be used to control the diagnostic messages formatting
|
|
algorithm, e.g.@: how many characters per line, how often source location
|
|
information should be reported. Right now, only the C++ front end can
|
|
honor these options. However it is expected, in the near future, that
|
|
the remaining front ends would be able to digest them correctly.
|
|
|
|
@table @gcctabopt
|
|
@item -fmessage-length=@var{n}
|
|
@opindex fmessage-length
|
|
Try to format error messages so that they fit on lines of about @var{n}
|
|
characters. The default is 72 characters for @command{g++} and 0 for the rest of
|
|
the front ends supported by GCC@. If @var{n} is zero, then no
|
|
line-wrapping will be done; each error message will appear on a single
|
|
line.
|
|
|
|
@opindex fdiagnostics-show-location
|
|
@item -fdiagnostics-show-location=once
|
|
Only meaningful in line-wrapping mode. Instructs the diagnostic messages
|
|
reporter to emit @emph{once} source location information; that is, in
|
|
case the message is too long to fit on a single physical line and has to
|
|
be wrapped, the source location won't be emitted (as prefix) again,
|
|
over and over, in subsequent continuation lines. This is the default
|
|
behavior.
|
|
|
|
@item -fdiagnostics-show-location=every-line
|
|
Only meaningful in line-wrapping mode. Instructs the diagnostic
|
|
messages reporter to emit the same source location information (as
|
|
prefix) for physical lines that result from the process of breaking
|
|
a message which is too long to fit on a single line.
|
|
|
|
@end table
|
|
|
|
@node Warning Options
|
|
@section Options to Request or Suppress Warnings
|
|
@cindex options to control warnings
|
|
@cindex warning messages
|
|
@cindex messages, warning
|
|
@cindex suppressing warnings
|
|
|
|
Warnings are diagnostic messages that report constructions which
|
|
are not inherently erroneous but which are risky or suggest there
|
|
may have been an error.
|
|
|
|
You can request many specific warnings with options beginning @samp{-W},
|
|
for example @option{-Wimplicit} to request warnings on implicit
|
|
declarations. Each of these specific warning options also has a
|
|
negative form beginning @samp{-Wno-} to turn off warnings;
|
|
for example, @option{-Wno-implicit}. This manual lists only one of the
|
|
two forms, whichever is not the default.
|
|
|
|
These options control the amount and kinds of warnings produced by GCC:
|
|
|
|
@table @gcctabopt
|
|
@cindex syntax checking
|
|
@item -fsyntax-only
|
|
@opindex fsyntax-only
|
|
Check the code for syntax errors, but don't do anything beyond that.
|
|
|
|
@item -pedantic
|
|
@opindex pedantic
|
|
Issue all the warnings demanded by strict ISO C and ISO C++;
|
|
reject all programs that use forbidden extensions, and some other
|
|
programs that do not follow ISO C and ISO C++. For ISO C, follows the
|
|
version of the ISO C standard specified by any @option{-std} option used.
|
|
|
|
Valid ISO C and ISO C++ programs should compile properly with or without
|
|
this option (though a rare few will require @option{-ansi} or a
|
|
@option{-std} option specifying the required version of ISO C)@. However,
|
|
without this option, certain GNU extensions and traditional C and C++
|
|
features are supported as well. With this option, they are rejected.
|
|
|
|
@option{-pedantic} does not cause warning messages for use of the
|
|
alternate keywords whose names begin and end with @samp{__}. Pedantic
|
|
warnings are also disabled in the expression that follows
|
|
@code{__extension__}. However, only system header files should use
|
|
these escape routes; application programs should avoid them.
|
|
@xref{Alternate Keywords}.
|
|
|
|
Some users try to use @option{-pedantic} to check programs for strict ISO
|
|
C conformance. They soon find that it does not do quite what they want:
|
|
it finds some non-ISO practices, but not all---only those for which
|
|
ISO C @emph{requires} a diagnostic, and some others for which
|
|
diagnostics have been added.
|
|
|
|
A feature to report any failure to conform to ISO C might be useful in
|
|
some instances, but would require considerable additional work and would
|
|
be quite different from @option{-pedantic}. We don't have plans to
|
|
support such a feature in the near future.
|
|
|
|
Where the standard specified with @option{-std} represents a GNU
|
|
extended dialect of C, such as @samp{gnu89} or @samp{gnu99}, there is a
|
|
corresponding @dfn{base standard}, the version of ISO C on which the GNU
|
|
extended dialect is based. Warnings from @option{-pedantic} are given
|
|
where they are required by the base standard. (It would not make sense
|
|
for such warnings to be given only for features not in the specified GNU
|
|
C dialect, since by definition the GNU dialects of C include all
|
|
features the compiler supports with the given option, and there would be
|
|
nothing to warn about.)
|
|
|
|
@item -pedantic-errors
|
|
@opindex pedantic-errors
|
|
Like @option{-pedantic}, except that errors are produced rather than
|
|
warnings.
|
|
|
|
@item -w
|
|
@opindex w
|
|
Inhibit all warning messages.
|
|
|
|
@item -Wno-import
|
|
@opindex Wno-import
|
|
Inhibit warning messages about the use of @samp{#import}.
|
|
|
|
@item -Wchar-subscripts
|
|
@opindex Wchar-subscripts
|
|
Warn if an array subscript has type @code{char}. This is a common cause
|
|
of error, as programmers often forget that this type is signed on some
|
|
machines.
|
|
|
|
@item -Wcomment
|
|
@opindex Wcomment
|
|
Warn whenever a comment-start sequence @samp{/*} appears in a @samp{/*}
|
|
comment, or whenever a Backslash-Newline appears in a @samp{//} comment.
|
|
|
|
@item -Wformat
|
|
@opindex Wformat
|
|
Check calls to @code{printf} and @code{scanf}, etc., to make sure that
|
|
the arguments supplied have types appropriate to the format string
|
|
specified, and that the conversions specified in the format string make
|
|
sense. This includes standard functions, and others specified by format
|
|
attributes (@pxref{Function Attributes}), in the @code{printf},
|
|
@code{scanf}, @code{strftime} and @code{strfmon} (an X/Open extension,
|
|
not in the C standard) families.
|
|
|
|
The formats are checked against the format features supported by GNU
|
|
libc version 2.2. These include all ISO C89 and C99 features, as well
|
|
as features from the Single Unix Specification and some BSD and GNU
|
|
extensions. Other library implementations may not support all these
|
|
features; GCC does not support warning about features that go beyond a
|
|
particular library's limitations. However, if @option{-pedantic} is used
|
|
with @option{-Wformat}, warnings will be given about format features not
|
|
in the selected standard version (but not for @code{strfmon} formats,
|
|
since those are not in any version of the C standard). @xref{C Dialect
|
|
Options,,Options Controlling C Dialect}.
|
|
|
|
@option{-Wformat} is included in @option{-Wall}. For more control over some
|
|
aspects of format checking, the options @option{-Wno-format-y2k},
|
|
@option{-Wno-format-extra-args}, @option{-Wformat-nonliteral},
|
|
@option{-Wformat-security} and @option{-Wformat=2} are available, but are
|
|
not included in @option{-Wall}.
|
|
|
|
@item -Wno-format-y2k
|
|
@opindex Wno-format-y2k
|
|
If @option{-Wformat} is specified, do not warn about @code{strftime}
|
|
formats which may yield only a two-digit year.
|
|
|
|
@item -Wno-format-extra-args
|
|
@opindex Wno-format-extra-args
|
|
If @option{-Wformat} is specified, do not warn about excess arguments to a
|
|
@code{printf} or @code{scanf} format function. The C standard specifies
|
|
that such arguments are ignored.
|
|
|
|
Where the unused arguments lie between used arguments that are
|
|
specified with @samp{$} operand number specifications, normally
|
|
warnings are still given, since the implementation could not know what
|
|
type to pass to @code{va_arg} to skip the unused arguments. However,
|
|
in the case of @code{scanf} formats, this option will suppress the
|
|
warning if the unused arguments are all pointers, since the Single
|
|
Unix Specification says that such unused arguments are allowed.
|
|
|
|
@item -Wformat-nonliteral
|
|
@opindex Wformat-nonliteral
|
|
If @option{-Wformat} is specified, also warn if the format string is not a
|
|
string literal and so cannot be checked, unless the format function
|
|
takes its format arguments as a @code{va_list}.
|
|
|
|
@item -Wformat-security
|
|
@opindex Wformat-security
|
|
If @option{-Wformat} is specified, also warn about uses of format
|
|
functions that represent possible security problems. At present, this
|
|
warns about calls to @code{printf} and @code{scanf} functions where the
|
|
format string is not a string literal and there are no format arguments,
|
|
as in @code{printf (foo);}. This may be a security hole if the format
|
|
string came from untrusted input and contains @samp{%n}. (This is
|
|
currently a subset of what @option{-Wformat-nonliteral} warns about, but
|
|
in future warnings may be added to @option{-Wformat-security} that are not
|
|
included in @option{-Wformat-nonliteral}.)
|
|
|
|
@item -Wformat=2
|
|
@opindex Wformat=2
|
|
Enable @option{-Wformat} plus format checks not included in
|
|
@option{-Wformat}. Currently equivalent to @samp{-Wformat
|
|
-Wformat-nonliteral -Wformat-security}.
|
|
|
|
@item -Wimplicit-int
|
|
@opindex Wimplicit-int
|
|
Warn when a declaration does not specify a type.
|
|
|
|
@item -Wimplicit-function-declaration
|
|
@itemx -Werror-implicit-function-declaration
|
|
@opindex Wimplicit-function-declaration
|
|
@opindex Werror-implicit-function-declaration
|
|
Give a warning (or error) whenever a function is used before being
|
|
declared.
|
|
|
|
@item -Wimplicit
|
|
@opindex Wimplicit
|
|
Same as @option{-Wimplicit-int} and @option{-Wimplicit-function-declaration}.
|
|
|
|
@item -Wmain
|
|
@opindex Wmain
|
|
Warn if the type of @samp{main} is suspicious. @samp{main} should be a
|
|
function with external linkage, returning int, taking either zero
|
|
arguments, two, or three arguments of appropriate types.
|
|
|
|
@item -Wmissing-braces
|
|
@opindex Wmissing-braces
|
|
Warn if an aggregate or union initializer is not fully bracketed. In
|
|
the following example, the initializer for @samp{a} is not fully
|
|
bracketed, but that for @samp{b} is fully bracketed.
|
|
|
|
@smallexample
|
|
int a[2][2] = @{ 0, 1, 2, 3 @};
|
|
int b[2][2] = @{ @{ 0, 1 @}, @{ 2, 3 @} @};
|
|
@end smallexample
|
|
|
|
@item -Wparentheses
|
|
@opindex Wparentheses
|
|
Warn if parentheses are omitted in certain contexts, such
|
|
as when there is an assignment in a context where a truth value
|
|
is expected, or when operators are nested whose precedence people
|
|
often get confused about.
|
|
|
|
Also warn about constructions where there may be confusion to which
|
|
@code{if} statement an @code{else} branch belongs. Here is an example of
|
|
such a case:
|
|
|
|
@smallexample
|
|
@group
|
|
@{
|
|
if (a)
|
|
if (b)
|
|
foo ();
|
|
else
|
|
bar ();
|
|
@}
|
|
@end group
|
|
@end smallexample
|
|
|
|
In C, every @code{else} branch belongs to the innermost possible @code{if}
|
|
statement, which in this example is @code{if (b)}. This is often not
|
|
what the programmer expected, as illustrated in the above example by
|
|
indentation the programmer chose. When there is the potential for this
|
|
confusion, GCC will issue a warning when this flag is specified.
|
|
To eliminate the warning, add explicit braces around the innermost
|
|
@code{if} statement so there is no way the @code{else} could belong to
|
|
the enclosing @code{if}. The resulting code would look like this:
|
|
|
|
@smallexample
|
|
@group
|
|
@{
|
|
if (a)
|
|
@{
|
|
if (b)
|
|
foo ();
|
|
else
|
|
bar ();
|
|
@}
|
|
@}
|
|
@end group
|
|
@end smallexample
|
|
|
|
@item -Wsequence-point
|
|
@opindex Wsequence-point
|
|
Warn about code that may have undefined semantics because of violations
|
|
of sequence point rules in the C standard.
|
|
|
|
The C standard defines the order in which expressions in a C program are
|
|
evaluated in terms of @dfn{sequence points}, which represent a partial
|
|
ordering between the execution of parts of the program: those executed
|
|
before the sequence point, and those executed after it. These occur
|
|
after the evaluation of a full expression (one which is not part of a
|
|
larger expression), after the evaluation of the first operand of a
|
|
@code{&&}, @code{||}, @code{? :} or @code{,} (comma) operator, before a
|
|
function is called (but after the evaluation of its arguments and the
|
|
expression denoting the called function), and in certain other places.
|
|
Other than as expressed by the sequence point rules, the order of
|
|
evaluation of subexpressions of an expression is not specified. All
|
|
these rules describe only a partial order rather than a total order,
|
|
since, for example, if two functions are called within one expression
|
|
with no sequence point between them, the order in which the functions
|
|
are called is not specified. However, the standards committee have
|
|
ruled that function calls do not overlap.
|
|
|
|
It is not specified when between sequence points modifications to the
|
|
values of objects take effect. Programs whose behavior depends on this
|
|
have undefined behavior; the C standard specifies that ``Between the
|
|
previous and next sequence point an object shall have its stored value
|
|
modified at most once by the evaluation of an expression. Furthermore,
|
|
the prior value shall be read only to determine the value to be
|
|
stored.''. If a program breaks these rules, the results on any
|
|
particular implementation are entirely unpredictable.
|
|
|
|
Examples of code with undefined behavior are @code{a = a++;}, @code{a[n]
|
|
= b[n++]} and @code{a[i++] = i;}. Some more complicated cases are not
|
|
diagnosed by this option, and it may give an occasional false positive
|
|
result, but in general it has been found fairly effective at detecting
|
|
this sort of problem in programs.
|
|
|
|
The present implementation of this option only works for C programs. A
|
|
future implementation may also work for C++ programs.
|
|
|
|
The C standard is worded confusingly, therefore there is some debate
|
|
over the precise meaning of the sequence point rules in subtle cases.
|
|
Links to discussions of the problem, including proposed formal
|
|
definitions, may be found on our readings page, at
|
|
@w{@uref{http://gcc.gnu.org/readings.html}}.
|
|
|
|
@item -Wreturn-type
|
|
@opindex Wreturn-type
|
|
Warn whenever a function is defined with a return-type that defaults to
|
|
@code{int}. Also warn about any @code{return} statement with no
|
|
return-value in a function whose return-type is not @code{void}.
|
|
|
|
For C++, a function without return type always produces a diagnostic
|
|
message, even when @option{-Wno-return-type} is specified. The only
|
|
exceptions are @samp{main} and functions defined in system headers.
|
|
|
|
@item -Wswitch
|
|
@opindex Wswitch
|
|
Warn whenever a @code{switch} statement has an index of enumeral type
|
|
and lacks a @code{case} for one or more of the named codes of that
|
|
enumeration. (The presence of a @code{default} label prevents this
|
|
warning.) @code{case} labels outside the enumeration range also
|
|
provoke warnings when this option is used.
|
|
|
|
@item -Wtrigraphs
|
|
@opindex Wtrigraphs
|
|
Warn if any trigraphs are encountered that might change the meaning of
|
|
the program (trigraphs within comments are not warned about).
|
|
|
|
@item -Wunused-function
|
|
@opindex Wunused-function
|
|
Warn whenever a static function is declared but not defined or a
|
|
non\-inline static function is unused.
|
|
|
|
@item -Wunused-label
|
|
@opindex Wunused-label
|
|
Warn whenever a label is declared but not used.
|
|
|
|
To suppress this warning use the @samp{unused} attribute
|
|
(@pxref{Variable Attributes}).
|
|
|
|
@item -Wunused-parameter
|
|
@opindex Wunused-parameter
|
|
Warn whenever a function parameter is unused aside from its declaration.
|
|
|
|
To suppress this warning use the @samp{unused} attribute
|
|
(@pxref{Variable Attributes}).
|
|
|
|
@item -Wunused-variable
|
|
@opindex Wunused-variable
|
|
Warn whenever a local variable or non-constant static variable is unused
|
|
aside from its declaration
|
|
|
|
To suppress this warning use the @samp{unused} attribute
|
|
(@pxref{Variable Attributes}).
|
|
|
|
@item -Wunused-value
|
|
@opindex Wunused-value
|
|
Warn whenever a statement computes a result that is explicitly not used.
|
|
|
|
To suppress this warning cast the expression to @samp{void}.
|
|
|
|
@item -Wunused
|
|
@opindex Wunused
|
|
All all the above @option{-Wunused} options combined.
|
|
|
|
In order to get a warning about an unused function parameter, you must
|
|
either specify @samp{-W -Wunused} or separately specify
|
|
@option{-Wunused-parameter}.
|
|
|
|
@item -Wuninitialized
|
|
@opindex Wuninitialized
|
|
Warn if an automatic variable is used without first being initialized or
|
|
if a variable may be clobbered by a @code{setjmp} call.
|
|
|
|
These warnings are possible only in optimizing compilation,
|
|
because they require data flow information that is computed only
|
|
when optimizing. If you don't specify @option{-O}, you simply won't
|
|
get these warnings.
|
|
|
|
These warnings occur only for variables that are candidates for
|
|
register allocation. Therefore, they do not occur for a variable that
|
|
is declared @code{volatile}, or whose address is taken, or whose size
|
|
is other than 1, 2, 4 or 8 bytes. Also, they do not occur for
|
|
structures, unions or arrays, even when they are in registers.
|
|
|
|
Note that there may be no warning about a variable that is used only
|
|
to compute a value that itself is never used, because such
|
|
computations may be deleted by data flow analysis before the warnings
|
|
are printed.
|
|
|
|
These warnings are made optional because GCC is not smart
|
|
enough to see all the reasons why the code might be correct
|
|
despite appearing to have an error. Here is one example of how
|
|
this can happen:
|
|
|
|
@smallexample
|
|
@group
|
|
@{
|
|
int x;
|
|
switch (y)
|
|
@{
|
|
case 1: x = 1;
|
|
break;
|
|
case 2: x = 4;
|
|
break;
|
|
case 3: x = 5;
|
|
@}
|
|
foo (x);
|
|
@}
|
|
@end group
|
|
@end smallexample
|
|
|
|
@noindent
|
|
If the value of @code{y} is always 1, 2 or 3, then @code{x} is
|
|
always initialized, but GCC doesn't know this. Here is
|
|
another common case:
|
|
|
|
@smallexample
|
|
@{
|
|
int save_y;
|
|
if (change_y) save_y = y, y = new_y;
|
|
@dots{}
|
|
if (change_y) y = save_y;
|
|
@}
|
|
@end smallexample
|
|
|
|
@noindent
|
|
This has no bug because @code{save_y} is used only if it is set.
|
|
|
|
@cindex @code{longjmp} warnings
|
|
This option also warns when a non-volatile automatic variable might be
|
|
changed by a call to @code{longjmp}. These warnings as well are possible
|
|
only in optimizing compilation.
|
|
|
|
The compiler sees only the calls to @code{setjmp}. It cannot know
|
|
where @code{longjmp} will be called; in fact, a signal handler could
|
|
call it at any point in the code. As a result, you may get a warning
|
|
even when there is in fact no problem because @code{longjmp} cannot
|
|
in fact be called at the place which would cause a problem.
|
|
|
|
Some spurious warnings can be avoided if you declare all the functions
|
|
you use that never return as @code{noreturn}. @xref{Function
|
|
Attributes}.
|
|
|
|
@item -Wreorder @r{(C++ only)}
|
|
@opindex Wreorder
|
|
@cindex reordering, warning
|
|
@cindex warning for reordering of member initializers
|
|
Warn when the order of member initializers given in the code does not
|
|
match the order in which they must be executed. For instance:
|
|
|
|
@item -Wunknown-pragmas
|
|
@opindex Wunknown-pragmas
|
|
@cindex warning for unknown pragmas
|
|
@cindex unknown pragmas, warning
|
|
@cindex pragmas, warning of unknown
|
|
Warn when a #pragma directive is encountered which is not understood by
|
|
GCC@. If this command line option is used, warnings will even be issued
|
|
for unknown pragmas in system header files. This is not the case if
|
|
the warnings were only enabled by the @option{-Wall} command line option.
|
|
|
|
@item -Wall
|
|
@opindex Wall
|
|
All of the above @samp{-W} options combined. This enables all the
|
|
warnings about constructions that some users consider questionable, and
|
|
that are easy to avoid (or modify to prevent the warning), even in
|
|
conjunction with macros.
|
|
|
|
@item -Wdiv-by-zero
|
|
@opindex Wno-div-by-zero
|
|
@opindex Wdiv-by-zero
|
|
Warn about compile-time integer division by zero. This is default. To
|
|
inhibit the warning messages, use @option{-Wno-div-by-zero}. Floating
|
|
point division by zero is not warned about, as it can be a legitimate
|
|
way of obtaining infinities and NaNs.
|
|
|
|
@item -Wmultichar
|
|
@opindex Wno-multichar
|
|
@opindex Wmultichar
|
|
Warn if a multicharacter constant (@samp{'FOOF'}) is used. This is
|
|
default. To inhibit the warning messages, use @option{-Wno-multichar}.
|
|
Usually they indicate a typo in the user's code, as they have
|
|
implementation-defined values, and should not be used in portable code.
|
|
|
|
@item -Wsystem-headers
|
|
@opindex Wsystem-headers
|
|
@cindex warnings from system headers
|
|
@cindex system headers, warnings from
|
|
Print warning messages for constructs found in system header files.
|
|
Warnings from system headers are normally suppressed, on the assumption
|
|
that they usually do not indicate real problems and would only make the
|
|
compiler output harder to read. Using this command line option tells
|
|
GCC to emit warnings from system headers as if they occurred in user
|
|
code. However, note that using @option{-Wall} in conjunction with this
|
|
option will @emph{not} warn about unknown pragmas in system
|
|
headers---for that, @option{-Wunknown-pragmas} must also be used.
|
|
@end table
|
|
|
|
The following @option{-W@dots{}} options are not implied by @option{-Wall}.
|
|
Some of them warn about constructions that users generally do not
|
|
consider questionable, but which occasionally you might wish to check
|
|
for; others warn about constructions that are necessary or hard to avoid
|
|
in some cases, and there is no simple way to modify the code to suppress
|
|
the warning.
|
|
|
|
@table @gcctabopt
|
|
@item -W
|
|
@opindex W
|
|
Print extra warning messages for these events:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
A function can return either with or without a value. (Falling
|
|
off the end of the function body is considered returning without
|
|
a value.) For example, this function would evoke such a
|
|
warning:
|
|
|
|
@smallexample
|
|
@group
|
|
foo (a)
|
|
@{
|
|
if (a > 0)
|
|
return a;
|
|
@}
|
|
@end group
|
|
@end smallexample
|
|
|
|
@item
|
|
An expression-statement or the left-hand side of a comma expression
|
|
contains no side effects.
|
|
To suppress the warning, cast the unused expression to void.
|
|
For example, an expression such as @samp{x[i,j]} will cause a warning,
|
|
but @samp{x[(void)i,j]} will not.
|
|
|
|
@item
|
|
An unsigned value is compared against zero with @samp{<} or @samp{<=}.
|
|
|
|
@item
|
|
A comparison like @samp{x<=y<=z} appears; this is equivalent to
|
|
@samp{(x<=y ? 1 : 0) <= z}, which is a different interpretation from
|
|
that of ordinary mathematical notation.
|
|
|
|
@item
|
|
Storage-class specifiers like @code{static} are not the first things in
|
|
a declaration. According to the C Standard, this usage is obsolescent.
|
|
|
|
@item
|
|
The return type of a function has a type qualifier such as @code{const}.
|
|
Such a type qualifier has no effect, since the value returned by a
|
|
function is not an lvalue. (But don't warn about the GNU extension of
|
|
@code{volatile void} return types. That extension will be warned about
|
|
if @option{-pedantic} is specified.)
|
|
|
|
@item
|
|
If @option{-Wall} or @option{-Wunused} is also specified, warn about unused
|
|
arguments.
|
|
|
|
@item
|
|
A comparison between signed and unsigned values could produce an
|
|
incorrect result when the signed value is converted to unsigned.
|
|
(But don't warn if @option{-Wno-sign-compare} is also specified.)
|
|
|
|
@item
|
|
An aggregate has a partly bracketed initializer.
|
|
For example, the following code would evoke such a warning,
|
|
because braces are missing around the initializer for @code{x.h}:
|
|
|
|
@smallexample
|
|
struct s @{ int f, g; @};
|
|
struct t @{ struct s h; int i; @};
|
|
struct t x = @{ 1, 2, 3 @};
|
|
@end smallexample
|
|
|
|
@item
|
|
An aggregate has an initializer which does not initialize all members.
|
|
For example, the following code would cause such a warning, because
|
|
@code{x.h} would be implicitly initialized to zero:
|
|
|
|
@smallexample
|
|
struct s @{ int f, g, h; @};
|
|
struct s x = @{ 3, 4 @};
|
|
@end smallexample
|
|
@end itemize
|
|
|
|
@item -Wfloat-equal
|
|
@opindex Wfloat-equal
|
|
Warn if floating point values are used in equality comparisons.
|
|
|
|
The idea behind this is that sometimes it is convenient (for the
|
|
programmer) to consider floating-point values as approximations to
|
|
infinitely precise real numbers. If you are doing this, then you need
|
|
to compute (by analysing the code, or in some other way) the maximum or
|
|
likely maximum error that the computation introduces, and allow for it
|
|
when performing comparisons (and when producing output, but that's a
|
|
different problem). In particular, instead of testing for equality, you
|
|
would check to see whether the two values have ranges that overlap; and
|
|
this is done with the relational operators, so equality comparisons are
|
|
probably mistaken.
|
|
|
|
@item -Wtraditional @r{(C only)}
|
|
@opindex Wtraditional
|
|
Warn about certain constructs that behave differently in traditional and
|
|
ISO C@. Also warn about ISO C constructs that have no traditional C
|
|
equivalent, and/or problematic constructs which should be avoided.
|
|
|
|
@itemize @bullet
|
|
@item
|
|
Macro parameters that appear within string literals in the macro body.
|
|
In traditional C macro replacement takes place within string literals,
|
|
but does not in ISO C@.
|
|
|
|
@item
|
|
In traditional C, some preprocessor directives did not exist.
|
|
Traditional preprocessors would only consider a line to be a directive
|
|
if the @samp{#} appeared in column 1 on the line. Therefore
|
|
@option{-Wtraditional} warns about directives that traditional C
|
|
understands but would ignore because the @samp{#} does not appear as the
|
|
first character on the line. It also suggests you hide directives like
|
|
@samp{#pragma} not understood by traditional C by indenting them. Some
|
|
traditional implementations would not recognize @samp{#elif}, so it
|
|
suggests avoiding it altogether.
|
|
|
|
@item
|
|
A function-like macro that appears without arguments.
|
|
|
|
@item
|
|
The unary plus operator.
|
|
|
|
@item
|
|
The @samp{U} integer constant suffix, or the @samp{F} or @samp{L} floating point
|
|
constant suffixes. (Traditional C does support the @samp{L} suffix on integer
|
|
constants.) Note, these suffixes appear in macros defined in the system
|
|
headers of most modern systems, e.g.@: the @samp{_MIN}/@samp{_MAX} macros in @code{<limits.h>}.
|
|
Use of these macros in user code might normally lead to spurious
|
|
warnings, however gcc's integrated preprocessor has enough context to
|
|
avoid warning in these cases.
|
|
|
|
@item
|
|
A function declared external in one block and then used after the end of
|
|
the block.
|
|
|
|
@item
|
|
A @code{switch} statement has an operand of type @code{long}.
|
|
|
|
@item
|
|
A non-@code{static} function declaration follows a @code{static} one.
|
|
This construct is not accepted by some traditional C compilers.
|
|
|
|
@item
|
|
The ISO type of an integer constant has a different width or
|
|
signedness from its traditional type. This warning is only issued if
|
|
the base of the constant is ten. I.e.@: hexadecimal or octal values, which
|
|
typically represent bit patterns, are not warned about.
|
|
|
|
@item
|
|
Usage of ISO string concatenation is detected.
|
|
|
|
@item
|
|
Initialization of automatic aggregates.
|
|
|
|
@item
|
|
Identifier conflicts with labels. Traditional C lacks a separate
|
|
namespace for labels.
|
|
|
|
@item
|
|
Initialization of unions. If the initializer is zero, the warning is
|
|
omitted. This is done under the assumption that the zero initializer in
|
|
user code appears conditioned on e.g.@: @code{__STDC__} to avoid missing
|
|
initializer warnings and relies on default initialization to zero in the
|
|
traditional C case.
|
|
|
|
@item
|
|
Conversions by prototypes between fixed/floating point values and vice
|
|
versa. The absence of these prototypes when compiling with traditional
|
|
C would cause serious problems. This is a subset of the possible
|
|
conversion warnings, for the full set use @option{-Wconversion}.
|
|
@end itemize
|
|
|
|
@item -Wundef
|
|
@opindex Wundef
|
|
Warn if an undefined identifier is evaluated in an @samp{#if} directive.
|
|
|
|
@item -Wshadow
|
|
@opindex Wshadow
|
|
Warn whenever a local variable shadows another local variable, parameter or
|
|
global variable or whenever a built-in function is shadowed.
|
|
|
|
@item -Wlarger-than-@var{len}
|
|
@opindex Wlarger-than
|
|
Warn whenever an object of larger than @var{len} bytes is defined.
|
|
|
|
@item -Wpointer-arith
|
|
@opindex Wpointer-arith
|
|
Warn about anything that depends on the ``size of'' a function type or
|
|
of @code{void}. GNU C assigns these types a size of 1, for
|
|
convenience in calculations with @code{void *} pointers and pointers
|
|
to functions.
|
|
|
|
@item -Wbad-function-cast @r{(C only)}
|
|
@opindex Wbad-function-cast
|
|
Warn whenever a function call is cast to a non-matching type.
|
|
For example, warn if @code{int malloc()} is cast to @code{anything *}.
|
|
|
|
@item -Wcast-qual
|
|
@opindex Wcast-qual
|
|
Warn whenever a pointer is cast so as to remove a type qualifier from
|
|
the target type. For example, warn if a @code{const char *} is cast
|
|
to an ordinary @code{char *}.
|
|
|
|
@item -Wcast-align
|
|
@opindex Wcast-align
|
|
Warn whenever a pointer is cast such that the required alignment of the
|
|
target is increased. For example, warn if a @code{char *} is cast to
|
|
an @code{int *} on machines where integers can only be accessed at
|
|
two- or four-byte boundaries.
|
|
|
|
@item -Wwrite-strings
|
|
@opindex Wwrite-strings
|
|
When compiling C, give string constants the type @code{const
|
|
char[@var{length}]} so that
|
|
copying the address of one into a non-@code{const} @code{char *}
|
|
pointer will get a warning; when compiling C++, warn about the
|
|
deprecated conversion from string constants to @code{char *}.
|
|
These warnings will help you find at
|
|
compile time code that can try to write into a string constant, but
|
|
only if you have been very careful about using @code{const} in
|
|
declarations and prototypes. Otherwise, it will just be a nuisance;
|
|
this is why we did not make @option{-Wall} request these warnings.
|
|
|
|
@item -Wconversion
|
|
@opindex Wconversion
|
|
Warn if a prototype causes a type conversion that is different from what
|
|
would happen to the same argument in the absence of a prototype. This
|
|
includes conversions of fixed point to floating and vice versa, and
|
|
conversions changing the width or signedness of a fixed point argument
|
|
except when the same as the default promotion.
|
|
|
|
Also, warn if a negative integer constant expression is implicitly
|
|
converted to an unsigned type. For example, warn about the assignment
|
|
@code{x = -1} if @code{x} is unsigned. But do not warn about explicit
|
|
casts like @code{(unsigned) -1}.
|
|
|
|
@item -Wsign-compare
|
|
@opindex Wsign-compare
|
|
@cindex warning for comparison of signed and unsigned values
|
|
@cindex comparison of signed and unsigned values, warning
|
|
@cindex signed and unsigned values, comparison warning
|
|
Warn when a comparison between signed and unsigned values could produce
|
|
an incorrect result when the signed value is converted to unsigned.
|
|
This warning is also enabled by @option{-W}; to get the other warnings
|
|
of @option{-W} without this warning, use @samp{-W -Wno-sign-compare}.
|
|
|
|
@item -Waggregate-return
|
|
@opindex Waggregate-return
|
|
Warn if any functions that return structures or unions are defined or
|
|
called. (In languages where you can return an array, this also elicits
|
|
a warning.)
|
|
|
|
@item -Wstrict-prototypes @r{(C only)}
|
|
@opindex Wstrict-prototypes
|
|
Warn if a function is declared or defined without specifying the
|
|
argument types. (An old-style function definition is permitted without
|
|
a warning if preceded by a declaration which specifies the argument
|
|
types.)
|
|
|
|
@item -Wmissing-prototypes @r{(C only)}
|
|
@opindex Wmissing-prototypes
|
|
Warn if a global function is defined without a previous prototype
|
|
declaration. This warning is issued even if the definition itself
|
|
provides a prototype. The aim is to detect global functions that fail
|
|
to be declared in header files.
|
|
|
|
@item -Wmissing-declarations
|
|
@opindex Wmissing-declarations
|
|
Warn if a global function is defined without a previous declaration.
|
|
Do so even if the definition itself provides a prototype.
|
|
Use this option to detect global functions that are not declared in
|
|
header files.
|
|
|
|
@item -Wmissing-noreturn
|
|
@opindex Wmissing-noreturn
|
|
Warn about functions which might be candidates for attribute @code{noreturn}.
|
|
Note these are only possible candidates, not absolute ones. Care should
|
|
be taken to manually verify functions actually do not ever return before
|
|
adding the @code{noreturn} attribute, otherwise subtle code generation
|
|
bugs could be introduced. You will not get a warning for @code{main} in
|
|
hosted C environments.
|
|
|
|
@item -Wmissing-format-attribute
|
|
@opindex Wmissing-format-attribute
|
|
@opindex Wformat
|
|
If @option{-Wformat} is enabled, also warn about functions which might be
|
|
candidates for @code{format} attributes. Note these are only possible
|
|
candidates, not absolute ones. GCC will guess that @code{format}
|
|
attributes might be appropriate for any function that calls a function
|
|
like @code{vprintf} or @code{vscanf}, but this might not always be the
|
|
case, and some functions for which @code{format} attributes are
|
|
appropriate may not be detected. This option has no effect unless
|
|
@option{-Wformat} is enabled (possibly by @option{-Wall}).
|
|
|
|
@item -Wno-deprecated-declarations
|
|
@opindex Wno-deprecated-declarations
|
|
Do not warn about uses of functions, variables, and types marked as
|
|
deprecated by using the @code{deprecated} attribute.
|
|
(@pxref{Function Attributes}, @pxref{Variable Attributes},
|
|
@pxref{Type Attributes}.)
|
|
|
|
@item -Wpacked
|
|
@opindex Wpacked
|
|
Warn if a structure is given the packed attribute, but the packed
|
|
attribute has no effect on the layout or size of the structure.
|
|
Such structures may be mis-aligned for little benefit. For
|
|
instance, in this code, the variable @code{f.x} in @code{struct bar}
|
|
will be misaligned even though @code{struct bar} does not itself
|
|
have the packed attribute:
|
|
|
|
@smallexample
|
|
@group
|
|
struct foo @{
|
|
int x;
|
|
char a, b, c, d;
|
|
@} __attribute__((packed));
|
|
struct bar @{
|
|
char z;
|
|
struct foo f;
|
|
@};
|
|
@end group
|
|
@end smallexample
|
|
|
|
@item -Wpadded
|
|
@opindex Wpadded
|
|
Warn if padding is included in a structure, either to align an element
|
|
of the structure or to align the whole structure. Sometimes when this
|
|
happens it is possible to rearrange the fields of the structure to
|
|
reduce the padding and so make the structure smaller.
|
|
|
|
@item -Wredundant-decls
|
|
@opindex Wredundant-decls
|
|
Warn if anything is declared more than once in the same scope, even in
|
|
cases where multiple declaration is valid and changes nothing.
|
|
|
|
@item -Wnested-externs @r{(C only)}
|
|
@opindex Wnested-externs
|
|
Warn if an @code{extern} declaration is encountered within a function.
|
|
|
|
@item -Wunreachable-code
|
|
@opindex Wunreachable-code
|
|
Warn if the compiler detects that code will never be executed.
|
|
|
|
This option is intended to warn when the compiler detects that at
|
|
least a whole line of source code will never be executed, because
|
|
some condition is never satisfied or because it is after a
|
|
procedure that never returns.
|
|
|
|
It is possible for this option to produce a warning even though there
|
|
are circumstances under which part of the affected line can be executed,
|
|
so care should be taken when removing apparently-unreachable code.
|
|
|
|
For instance, when a function is inlined, a warning may mean that the
|
|
line is unreachable in only one inlined copy of the function.
|
|
|
|
This option is not made part of @option{-Wall} because in a debugging
|
|
version of a program there is often substantial code which checks
|
|
correct functioning of the program and is, hopefully, unreachable
|
|
because the program does work. Another common use of unreachable
|
|
code is to provide behavior which is selectable at compile-time.
|
|
|
|
@item -Winline
|
|
@opindex Winline
|
|
Warn if a function can not be inlined and it was declared as inline.
|
|
|
|
@item -Wlong-long
|
|
@opindex Wlong-long
|
|
@opindex Wno-long-long
|
|
Warn if @samp{long long} type is used. This is default. To inhibit
|
|
the warning messages, use @option{-Wno-long-long}. Flags
|
|
@option{-Wlong-long} and @option{-Wno-long-long} are taken into account
|
|
only when @option{-pedantic} flag is used.
|
|
|
|
@item -Wdisabled-optimization
|
|
@opindex Wdisabled-optimization
|
|
Warn if a requested optimization pass is disabled. This warning does
|
|
not generally indicate that there is anything wrong with your code; it
|
|
merely indicates that GCC's optimizers were unable to handle the code
|
|
effectively. Often, the problem is that your code is too big or too
|
|
complex; GCC will refuse to optimize programs when the optimization
|
|
itself is likely to take inordinate amounts of time.
|
|
|
|
@item -Werror
|
|
@opindex Werror
|
|
Make all warnings into errors.
|
|
@end table
|
|
|
|
@node Debugging Options
|
|
@section Options for Debugging Your Program or GCC
|
|
@cindex options, debugging
|
|
@cindex debugging information options
|
|
|
|
GCC has various special options that are used for debugging
|
|
either your program or GCC:
|
|
|
|
@table @gcctabopt
|
|
@item -g
|
|
@opindex g
|
|
Produce debugging information in the operating system's native format
|
|
(stabs, COFF, XCOFF, or DWARF)@. GDB can work with this debugging
|
|
information.
|
|
|
|
On most systems that use stabs format, @option{-g} enables use of extra
|
|
debugging information that only GDB can use; this extra information
|
|
makes debugging work better in GDB but will probably make other debuggers
|
|
crash or
|
|
refuse to read the program. If you want to control for certain whether
|
|
to generate the extra information, use @option{-gstabs+}, @option{-gstabs},
|
|
@option{-gxcoff+}, @option{-gxcoff}, @option{-gdwarf-1+}, @option{-gdwarf-1},
|
|
or @option{-gvms} (see below).
|
|
|
|
Unlike most other C compilers, GCC allows you to use @option{-g} with
|
|
@option{-O}. The shortcuts taken by optimized code may occasionally
|
|
produce surprising results: some variables you declared may not exist
|
|
at all; flow of control may briefly move where you did not expect it;
|
|
some statements may not be executed because they compute constant
|
|
results or their values were already at hand; some statements may
|
|
execute in different places because they were moved out of loops.
|
|
|
|
Nevertheless it proves possible to debug optimized output. This makes
|
|
it reasonable to use the optimizer for programs that might have bugs.
|
|
|
|
The following options are useful when GCC is generated with the
|
|
capability for more than one debugging format.
|
|
|
|
@item -ggdb
|
|
@opindex ggdb
|
|
Produce debugging information for use by GDB@. This means to use the
|
|
most expressive format available (DWARF 2, stabs, or the native format
|
|
if neither of those are supported), including GDB extensions if at all
|
|
possible.
|
|
|
|
@item -gstabs
|
|
@opindex gstabs
|
|
Produce debugging information in stabs format (if that is supported),
|
|
without GDB extensions. This is the format used by DBX on most BSD
|
|
systems. On MIPS, Alpha and System V Release 4 systems this option
|
|
produces stabs debugging output which is not understood by DBX or SDB@.
|
|
On System V Release 4 systems this option requires the GNU assembler.
|
|
|
|
@item -gstabs+
|
|
@opindex gstabs+
|
|
Produce debugging information in stabs format (if that is supported),
|
|
using GNU extensions understood only by the GNU debugger (GDB)@. The
|
|
use of these extensions is likely to make other debuggers crash or
|
|
refuse to read the program.
|
|
|
|
@item -gcoff
|
|
@opindex gcoff
|
|
Produce debugging information in COFF format (if that is supported).
|
|
This is the format used by SDB on most System V systems prior to
|
|
System V Release 4.
|
|
|
|
@item -gxcoff
|
|
@opindex gxcoff
|
|
Produce debugging information in XCOFF format (if that is supported).
|
|
This is the format used by the DBX debugger on IBM RS/6000 systems.
|
|
|
|
@item -gxcoff+
|
|
@opindex gxcoff+
|
|
Produce debugging information in XCOFF format (if that is supported),
|
|
using GNU extensions understood only by the GNU debugger (GDB)@. The
|
|
use of these extensions is likely to make other debuggers crash or
|
|
refuse to read the program, and may cause assemblers other than the GNU
|
|
assembler (GAS) to fail with an error.
|
|
|
|
@item -gdwarf
|
|
@opindex gdwarf
|
|
Produce debugging information in DWARF version 1 format (if that is
|
|
supported). This is the format used by SDB on most System V Release 4
|
|
systems.
|
|
|
|
@item -gdwarf+
|
|
@opindex gdwarf+
|
|
Produce debugging information in DWARF version 1 format (if that is
|
|
supported), using GNU extensions understood only by the GNU debugger
|
|
(GDB)@. The use of these extensions is likely to make other debuggers
|
|
crash or refuse to read the program.
|
|
|
|
@item -gdwarf-2
|
|
@opindex gdwarf-2
|
|
Produce debugging information in DWARF version 2 format (if that is
|
|
supported). This is the format used by DBX on IRIX 6.
|
|
|
|
@item -gvms
|
|
@opindex gvms
|
|
Produce debugging information in VMS debug format (if that is
|
|
supported). This is the format used by DEBUG on VMS systems.
|
|
|
|
@item -g@var{level}
|
|
@itemx -ggdb@var{level}
|
|
@itemx -gstabs@var{level}
|
|
@itemx -gcoff@var{level}
|
|
@itemx -gxcoff@var{level}
|
|
@itemx -gdwarf@var{level}
|
|
@itemx -gdwarf-2@var{level}
|
|
@itemx -gvms@var{level}
|
|
Request debugging information and also use @var{level} to specify how
|
|
much information. The default level is 2.
|
|
|
|
Level 1 produces minimal information, enough for making backtraces in
|
|
parts of the program that you don't plan to debug. This includes
|
|
descriptions of functions and external variables, but no information
|
|
about local variables and no line numbers.
|
|
|
|
Level 3 includes extra information, such as all the macro definitions
|
|
present in the program. Some debuggers support macro expansion when
|
|
you use @option{-g3}.
|
|
|
|
@cindex @code{prof}
|
|
@item -p
|
|
@opindex p
|
|
Generate extra code to write profile information suitable for the
|
|
analysis program @code{prof}. You must use this option when compiling
|
|
the source files you want data about, and you must also use it when
|
|
linking.
|
|
|
|
@cindex @code{gprof}
|
|
@item -pg
|
|
@opindex pg
|
|
Generate extra code to write profile information suitable for the
|
|
analysis program @code{gprof}. You must use this option when compiling
|
|
the source files you want data about, and you must also use it when
|
|
linking.
|
|
|
|
@cindex @code{tcov}
|
|
@item -a
|
|
@opindex a
|
|
Generate extra code to write profile information for basic blocks, which will
|
|
record the number of times each basic block is executed, the basic block start
|
|
address, and the function name containing the basic block. If @option{-g} is
|
|
used, the line number and filename of the start of the basic block will also be
|
|
recorded. If not overridden by the machine description, the default action is
|
|
to append to the text file @file{bb.out}.
|
|
|
|
This data could be analyzed by a program like @code{tcov}. Note,
|
|
however, that the format of the data is not what @code{tcov} expects.
|
|
Eventually GNU @code{gprof} should be extended to process this data.
|
|
|
|
@item -Q
|
|
@opindex Q
|
|
Makes the compiler print out each function name as it is compiled, and
|
|
print some statistics about each pass when it finishes.
|
|
|
|
@item -ftime-report
|
|
@opindex ftime-report
|
|
Makes the compiler print some statistics about the time consumed by each
|
|
pass when it finishes.
|
|
|
|
@item -fmem-report
|
|
@opindex fmem-report
|
|
Makes the compiler print some statistics about permanent memory
|
|
allocation when it finishes.
|
|
|
|
@item -fprofile-arcs
|
|
@opindex fprofile-arcs
|
|
Instrument @dfn{arcs} during compilation to generate coverage data
|
|
or for profile-directed block ordering. During execution the program
|
|
records how many times each branch is executed and how many times it is
|
|
taken. When the compiled program exits it saves this data to a file
|
|
called @file{@var{sourcename}.da} for each source file.
|
|
|
|
For profile-directed block ordering, compile the program with
|
|
@option{-fprofile-arcs} plus optimization and code generation options,
|
|
generate the arc profile information by running the program on a
|
|
selected workload, and then compile the program again with the same
|
|
optimization and code generation options plus
|
|
@option{-fbranch-probabilities} (@pxref{Optimize Options,,Options that
|
|
Control Optimization}).
|
|
|
|
The other use of @option{-fprofile-arcs} is for use with @code{gcov},
|
|
when it is used with the @option{-ftest-coverage} option. GCC
|
|
supports two methods of determining code coverage: the options that
|
|
support @code{gcov}, and options @option{-a} and @option{-ax}, which
|
|
write information to text files. The options that support @code{gcov}
|
|
do not need to instrument every arc in the program, so a program compiled
|
|
with them runs faster than a program compiled with @option{-a}, which
|
|
adds instrumentation code to every basic block in the program. The
|
|
tradeoff: since @code{gcov} does not have execution counts for all
|
|
branches, it must start with the execution counts for the instrumented
|
|
branches, and then iterate over the program flow graph until the entire
|
|
graph has been solved. Hence, @code{gcov} runs a little more slowly than
|
|
a program which uses information from @option{-a} and @option{-ax}.
|
|
|
|
With @option{-fprofile-arcs}, for each function of your program GCC
|
|
creates a program flow graph, then finds a spanning tree for the graph.
|
|
Only arcs that are not on the spanning tree have to be instrumented: the
|
|
compiler adds code to count the number of times that these arcs are
|
|
executed. When an arc is the only exit or only entrance to a block, the
|
|
instrumentation code can be added to the block; otherwise, a new basic
|
|
block must be created to hold the instrumentation code.
|
|
|
|
This option makes it possible to estimate branch probabilities and to
|
|
calculate basic block execution counts. In general, basic block
|
|
execution counts as provided by @option{-a} do not give enough
|
|
information to estimate all branch probabilities.
|
|
|
|
@need 2000
|
|
@item -ftest-coverage
|
|
@opindex ftest-coverage
|
|
Create data files for the @code{gcov} code-coverage utility
|
|
(@pxref{Gcov,, @code{gcov}: a GCC Test Coverage Program}).
|
|
The data file names begin with the name of your source file:
|
|
|
|
@table @gcctabopt
|
|
@item @var{sourcename}.bb
|
|
A mapping from basic blocks to line numbers, which @code{gcov} uses to
|
|
associate basic block execution counts with line numbers.
|
|
|
|
@item @var{sourcename}.bbg
|
|
A list of all arcs in the program flow graph. This allows @code{gcov}
|
|
to reconstruct the program flow graph, so that it can compute all basic
|
|
block and arc execution counts from the information in the
|
|
@code{@var{sourcename}.da} file.
|
|
@end table
|
|
|
|
Use @option{-ftest-coverage} with @option{-fprofile-arcs}; the latter
|
|
option adds instrumentation to the program, which then writes
|
|
execution counts to another data file:
|
|
|
|
@table @gcctabopt
|
|
@item @var{sourcename}.da
|
|
Runtime arc execution counts, used in conjunction with the arc
|
|
information in the file @code{@var{sourcename}.bbg}.
|
|
@end table
|
|
|
|
Coverage data will map better to the source files if
|
|
@option{-ftest-coverage} is used without optimization.
|
|
|
|
@item -d@var{letters}
|
|
@opindex d
|
|
Says to make debugging dumps during compilation at times specified by
|
|
@var{letters}. This is used for debugging the compiler. The file names
|
|
for most of the dumps are made by appending a pass number and a word to
|
|
the source file name (e.g. @file{foo.c.00.rtl} or @file{foo.c.01.sibling}).
|
|
Here are the possible letters for use in @var{letters}, and their meanings:
|
|
|
|
@table @samp
|
|
@item A
|
|
@opindex dA
|
|
Annotate the assembler output with miscellaneous debugging information.
|
|
@item b
|
|
@opindex db
|
|
Dump after computing branch probabilities, to @file{@var{file}.14.bp}.
|
|
@item B
|
|
@opindex dB
|
|
Dump after block reordering, to @file{@var{file}.29.bbro}.
|
|
@item c
|
|
@opindex dc
|
|
Dump after instruction combination, to the file @file{@var{file}.16.combine}.
|
|
@item C
|
|
@opindex dC
|
|
Dump after the first if conversion, to the file @file{@var{file}.17.ce}.
|
|
@item d
|
|
@opindex dd
|
|
Dump after delayed branch scheduling, to @file{@var{file}.31.dbr}.
|
|
@item D
|
|
@opindex dD
|
|
Dump all macro definitions, at the end of preprocessing, in addition to
|
|
normal output.
|
|
@item e
|
|
@opindex de
|
|
Dump after SSA optimizations, to @file{@var{file}.04.ssa} and
|
|
@file{@var{file}.07.ussa}.
|
|
@item E
|
|
@opindex dE
|
|
Dump after the second if conversion, to @file{@var{file}.26.ce2}.
|
|
@item f
|
|
@opindex df
|
|
Dump after life analysis, to @file{@var{file}.15.life}.
|
|
@item F
|
|
@opindex dF
|
|
Dump after purging @code{ADDRESSOF} codes, to @file{@var{file}.09.addressof}.
|
|
@item g
|
|
@opindex dg
|
|
Dump after global register allocation, to @file{@var{file}.21.greg}.
|
|
@item h
|
|
@opindex dh
|
|
Dump after finalization of EH handling code, to @file{@var{file}.02.eh}.
|
|
@item k
|
|
@opindex dk
|
|
Dump after reg-to-stack conversion, to @file{@var{file}.28.stack}.
|
|
@item o
|
|
@opindex do
|
|
Dump after post-reload optimizations, to @file{@var{file}.22.postreload}.
|
|
@item G
|
|
@opindex dG
|
|
Dump after GCSE, to @file{@var{file}.10.gcse}.
|
|
@item i
|
|
@opindex di
|
|
Dump after sibling call optimizations, to @file{@var{file}.01.sibling}.
|
|
@item j
|
|
@opindex dj
|
|
Dump after the first jump optimization, to @file{@var{file}.03.jump}.
|
|
@item k
|
|
@opindex dk
|
|
Dump after conversion from registers to stack, to @file{@var{file}.32.stack}.
|
|
@item l
|
|
@opindex dl
|
|
Dump after local register allocation, to @file{@var{file}.20.lreg}.
|
|
@item L
|
|
@opindex dL
|
|
Dump after loop optimization, to @file{@var{file}.11.loop}.
|
|
@item M
|
|
@opindex dM
|
|
Dump after performing the machine dependent reorganisation pass, to
|
|
@file{@var{file}.30.mach}.
|
|
@item n
|
|
@opindex dn
|
|
Dump after register renumbering, to @file{@var{file}.25.rnreg}.
|
|
@item N
|
|
@opindex dN
|
|
Dump after the register move pass, to @file{@var{file}.18.regmove}.
|
|
@item r
|
|
@opindex dr
|
|
Dump after RTL generation, to @file{@var{file}.00.rtl}.
|
|
@item R
|
|
@opindex dR
|
|
Dump after the second scheduling pass, to @file{@var{file}.27.sched2}.
|
|
@item s
|
|
@opindex ds
|
|
Dump after CSE (including the jump optimization that sometimes follows
|
|
CSE), to @file{@var{file}.08.cse}.
|
|
@item S
|
|
@opindex dS
|
|
Dump after the first scheduling pass, to @file{@var{file}.19.sched}.
|
|
@item t
|
|
@opindex dt
|
|
Dump after the second CSE pass (including the jump optimization that
|
|
sometimes follows CSE), to @file{@var{file}.12.cse2}.
|
|
@item w
|
|
@opindex dw
|
|
Dump after the second flow pass, to @file{@var{file}.23.flow2}.
|
|
@item X
|
|
@opindex dX
|
|
Dump after SSA dead code elimination, to @file{@var{file}.06.ssadce}.
|
|
@item z
|
|
@opindex dz
|
|
Dump after the peephole pass, to @file{@var{file}.24.peephole2}.
|
|
@item a
|
|
@opindex da
|
|
Produce all the dumps listed above.
|
|
@item m
|
|
@opindex dm
|
|
Print statistics on memory usage, at the end of the run, to
|
|
standard error.
|
|
@item p
|
|
@opindex dp
|
|
Annotate the assembler output with a comment indicating which
|
|
pattern and alternative was used. The length of each instruction is
|
|
also printed.
|
|
@item P
|
|
@opindex dP
|
|
Dump the RTL in the assembler output as a comment before each instruction.
|
|
Also turns on @option{-dp} annotation.
|
|
@item v
|
|
@opindex dv
|
|
For each of the other indicated dump files (except for
|
|
@file{@var{file}.00.rtl}), dump a representation of the control flow graph
|
|
suitable for viewing with VCG to @file{@var{file}.@var{pass}.vcg}.
|
|
@item x
|
|
@opindex dx
|
|
Just generate RTL for a function instead of compiling it. Usually used
|
|
with @samp{r}.
|
|
@item y
|
|
@opindex dy
|
|
Dump debugging information during parsing, to standard error.
|
|
@end table
|
|
|
|
@item -fdump-unnumbered
|
|
@opindex fdump-unnumbered
|
|
When doing debugging dumps (see @option{-d} option above), suppress instruction
|
|
numbers and line number note output. This makes it more feasible to
|
|
use diff on debugging dumps for compiler invocations with different
|
|
options, in particular with and without @option{-g}.
|
|
|
|
@item -fdump-translation-unit @r{(C and C++ only)}
|
|
@itemx -fdump-translation-unit-@var{options} @r{(C and C++ only)}
|
|
@opindex fdump-translation-unit
|
|
Dump a representation of the tree structure for the entire translation
|
|
unit to a file. The file name is made by appending @file{.tu} to the
|
|
source file name. If the @samp{-@var{options}} form is used, @var{options}
|
|
controls the details of the dump as described for the
|
|
@option{-fdump-tree} options.
|
|
|
|
@item -fdump-class-hierarchy @r{(C++ only)}
|
|
@itemx -fdump-class-hierarchy-@var{options} @r{(C++ only)}
|
|
@opindex fdump-class-hierarchy
|
|
Dump a representation of each class's hierarchy and virtual function
|
|
table layout to a file. The file name is made by appending @file{.class}
|
|
to the source file name. If the @samp{-@var{options}} form is used,
|
|
@var{options} controls the details of the dump as described for the
|
|
@option{-fdump-tree} options.
|
|
|
|
@item -fdump-tree-@var{switch} @r{(C++ only)}
|
|
@itemx -fdump-tree-@var{switch}-@var{options} @r{(C++ only)}
|
|
@opindex fdump-tree
|
|
Control the dumping at various stages of processing the intermediate
|
|
language tree to a file. The file name is generated by appending a switch
|
|
specific suffix to the source file name. If the @samp{-@var{options}}
|
|
form is used, @var{options} is a list of @samp{-} separated options that
|
|
control the details of the dump. Not all options are applicable to all
|
|
dumps, those which are not meaningful will be ignored. The following
|
|
options are available
|
|
|
|
@table @samp
|
|
@item address
|
|
Print the address of each node. Usually this is not meaningful as it
|
|
changes according to the environment and source file. Its primary use
|
|
is for tying up a dump file with a debug environment.
|
|
@item slim
|
|
Inhibit dumping of members of a scope or body of a function merely
|
|
because that scope has been reached. Only dump such items when they
|
|
are directly reachable by some other path.
|
|
@item all
|
|
Turn on all options.
|
|
@end table
|
|
|
|
The following tree dumps are possible:
|
|
@table @samp
|
|
@item original
|
|
Dump before any tree based optimization, to @file{@var{file}.original}.
|
|
@item optimized
|
|
Dump after all tree based optimization, to @file{@var{file}.optimized}.
|
|
@item inlined
|
|
Dump after function inlining, to @file{@var{file}.inlined}.
|
|
@end table
|
|
|
|
@item -fpretend-float
|
|
@opindex fpretend-float
|
|
When running a cross-compiler, pretend that the target machine uses the
|
|
same floating point format as the host machine. This causes incorrect
|
|
output of the actual floating constants, but the actual instruction
|
|
sequence will probably be the same as GCC would make when running on
|
|
the target machine.
|
|
|
|
@item -save-temps
|
|
@opindex save-temps
|
|
Store the usual ``temporary'' intermediate files permanently; place them
|
|
in the current directory and name them based on the source file. Thus,
|
|
compiling @file{foo.c} with @samp{-c -save-temps} would produce files
|
|
@file{foo.i} and @file{foo.s}, as well as @file{foo.o}. This creates a
|
|
preprocessed @file{foo.i} output file even though the compiler now
|
|
normally uses an integrated preprocessor.
|
|
|
|
@item -time
|
|
@opindex time
|
|
Report the CPU time taken by each subprocess in the compilation
|
|
sequence. For C source files, this is the compiler proper and assembler
|
|
(plus the linker if linking is done). The output looks like this:
|
|
|
|
@smallexample
|
|
# cc1 0.12 0.01
|
|
# as 0.00 0.01
|
|
@end smallexample
|
|
|
|
The first number on each line is the ``user time,'' that is time spent
|
|
executing the program itself. The second number is ``system time,''
|
|
time spent executing operating system routines on behalf of the program.
|
|
Both numbers are in seconds.
|
|
|
|
@item -print-file-name=@var{library}
|
|
@opindex print-file-name
|
|
Print the full absolute name of the library file @var{library} that
|
|
would be used when linking---and don't do anything else. With this
|
|
option, GCC does not compile or link anything; it just prints the
|
|
file name.
|
|
|
|
@item -print-multi-directory
|
|
@opindex print-multi-directory
|
|
Print the directory name corresponding to the multilib selected by any
|
|
other switches present in the command line. This directory is supposed
|
|
to exist in @env{GCC_EXEC_PREFIX}.
|
|
|
|
@item -print-multi-lib
|
|
@opindex print-multi-lib
|
|
Print the mapping from multilib directory names to compiler switches
|
|
that enable them. The directory name is separated from the switches by
|
|
@samp{;}, and each switch starts with an @samp{@@} instead of the
|
|
@samp{-}, without spaces between multiple switches. This is supposed to
|
|
ease shell-processing.
|
|
|
|
@item -print-prog-name=@var{program}
|
|
@opindex print-prog-name
|
|
Like @option{-print-file-name}, but searches for a program such as @samp{cpp}.
|
|
|
|
@item -print-libgcc-file-name
|
|
@opindex print-libgcc-file-name
|
|
Same as @option{-print-file-name=libgcc.a}.
|
|
|
|
This is useful when you use @option{-nostdlib} or @option{-nodefaultlibs}
|
|
but you do want to link with @file{libgcc.a}. You can do
|
|
|
|
@example
|
|
gcc -nostdlib @var{files}@dots{} `gcc -print-libgcc-file-name`
|
|
@end example
|
|
|
|
@item -print-search-dirs
|
|
@opindex print-search-dirs
|
|
Print the name of the configured installation directory and a list of
|
|
program and library directories gcc will search---and don't do anything else.
|
|
|
|
This is useful when gcc prints the error message
|
|
@samp{installation problem, cannot exec cpp0: No such file or directory}.
|
|
To resolve this you either need to put @file{cpp0} and the other compiler
|
|
components where gcc expects to find them, or you can set the environment
|
|
variable @env{GCC_EXEC_PREFIX} to the directory where you installed them.
|
|
Don't forget the trailing '/'.
|
|
@xref{Environment Variables}.
|
|
|
|
@item -dumpmachine
|
|
@opindex dumpmachine
|
|
Print the compiler's target machine (for example,
|
|
@samp{i686-pc-linux-gnu})---and don't do anything else.
|
|
|
|
@item -dumpversion
|
|
@opindex dumpversion
|
|
Print the compiler version (for example, @samp{3.0})---and don't do
|
|
anything else.
|
|
|
|
@item -dumpspecs
|
|
@opindex dumpspecs
|
|
Print the compiler's built-in specs---and don't do anything else. (This
|
|
is used when GCC itself is being built.) @xref{Spec Files}.
|
|
@end table
|
|
|
|
@node Optimize Options
|
|
@section Options That Control Optimization
|
|
@cindex optimize options
|
|
@cindex options, optimization
|
|
|
|
These options control various sorts of optimizations:
|
|
|
|
@table @gcctabopt
|
|
@item -O
|
|
@itemx -O1
|
|
@opindex O
|
|
@opindex O1
|
|
Optimize. Optimizing compilation takes somewhat more time, and a lot
|
|
more memory for a large function.
|
|
|
|
Without @option{-O}, the compiler's goal is to reduce the cost of
|
|
compilation and to make debugging produce the expected results.
|
|
Statements are independent: if you stop the program with a breakpoint
|
|
between statements, you can then assign a new value to any variable or
|
|
change the program counter to any other statement in the function and
|
|
get exactly the results you would expect from the source code.
|
|
|
|
With @option{-O}, the compiler tries to reduce code size and execution
|
|
time, without performing any optimizations that take a great deal of
|
|
compilation time.
|
|
|
|
@item -O2
|
|
@opindex O2
|
|
Optimize even more. GCC performs nearly all supported optimizations
|
|
that do not involve a space-speed tradeoff. The compiler does not
|
|
perform loop unrolling or function inlining when you specify @option{-O2}.
|
|
As compared to @option{-O}, this option increases both compilation time
|
|
and the performance of the generated code.
|
|
|
|
@option{-O2} turns on all optional optimizations except for loop unrolling,
|
|
function inlining, and register renaming. It also turns on the
|
|
@option{-fforce-mem} option on all machines and frame pointer elimination
|
|
on machines where doing so does not interfere with debugging.
|
|
|
|
Please note the warning under @option{-fgcse} about
|
|
invoking @option{-O2} on programs that use computed gotos.
|
|
|
|
@item -O3
|
|
@opindex O3
|
|
Optimize yet more. @option{-O3} turns on all optimizations specified by
|
|
@option{-O2} and also turns on the @option{-finline-functions} and
|
|
@option{-frename-registers} options.
|
|
|
|
@item -O0
|
|
@opindex O0
|
|
Do not optimize.
|
|
|
|
@item -Os
|
|
@opindex Os
|
|
Optimize for size. @option{-Os} enables all @option{-O2} optimizations that
|
|
do not typically increase code size. It also performs further
|
|
optimizations designed to reduce code size.
|
|
|
|
If you use multiple @option{-O} options, with or without level numbers,
|
|
the last such option is the one that is effective.
|
|
@end table
|
|
|
|
Options of the form @option{-f@var{flag}} specify machine-independent
|
|
flags. Most flags have both positive and negative forms; the negative
|
|
form of @option{-ffoo} would be @option{-fno-foo}. In the table below,
|
|
only one of the forms is listed---the one which is not the default.
|
|
You can figure out the other form by either removing @samp{no-} or
|
|
adding it.
|
|
|
|
@table @gcctabopt
|
|
@item -ffloat-store
|
|
@opindex ffloat-store
|
|
Do not store floating point variables in registers, and inhibit other
|
|
options that might change whether a floating point value is taken from a
|
|
register or memory.
|
|
|
|
@cindex floating point precision
|
|
This option prevents undesirable excess precision on machines such as
|
|
the 68000 where the floating registers (of the 68881) keep more
|
|
precision than a @code{double} is supposed to have. Similarly for the
|
|
x86 architecture. For most programs, the excess precision does only
|
|
good, but a few programs rely on the precise definition of IEEE floating
|
|
point. Use @option{-ffloat-store} for such programs, after modifying
|
|
them to store all pertinent intermediate computations into variables.
|
|
|
|
@item -fno-default-inline
|
|
@opindex fno-default-inline
|
|
Do not make member functions inline by default merely because they are
|
|
defined inside the class scope (C++ only). Otherwise, when you specify
|
|
@w{@option{-O}}, member functions defined inside class scope are compiled
|
|
inline by default; i.e., you don't need to add @samp{inline} in front of
|
|
the member function name.
|
|
|
|
@item -fno-defer-pop
|
|
@opindex fno-defer-pop
|
|
Always pop the arguments to each function call as soon as that function
|
|
returns. For machines which must pop arguments after a function call,
|
|
the compiler normally lets arguments accumulate on the stack for several
|
|
function calls and pops them all at once.
|
|
|
|
@item -fforce-mem
|
|
@opindex fforce-mem
|
|
Force memory operands to be copied into registers before doing
|
|
arithmetic on them. This produces better code by making all memory
|
|
references potential common subexpressions. When they are not common
|
|
subexpressions, instruction combination should eliminate the separate
|
|
register-load. The @option{-O2} option turns on this option.
|
|
|
|
@item -fforce-addr
|
|
@opindex fforce-addr
|
|
Force memory address constants to be copied into registers before
|
|
doing arithmetic on them. This may produce better code just as
|
|
@option{-fforce-mem} may.
|
|
|
|
@item -fomit-frame-pointer
|
|
@opindex fomit-frame-pointer
|
|
Don't keep the frame pointer in a register for functions that
|
|
don't need one. This avoids the instructions to save, set up and
|
|
restore frame pointers; it also makes an extra register available
|
|
in many functions. @strong{It also makes debugging impossible on
|
|
some machines.}
|
|
|
|
On some machines, such as the VAX, this flag has no effect, because
|
|
the standard calling sequence automatically handles the frame pointer
|
|
and nothing is saved by pretending it doesn't exist. The
|
|
machine-description macro @code{FRAME_POINTER_REQUIRED} controls
|
|
whether a target machine supports this flag. @xref{Registers,,Register
|
|
Usage, gccint, GNU Compiler Collection (GCC) Internals}.
|
|
|
|
@item -foptimize-sibling-calls
|
|
@opindex foptimize-sibling-calls
|
|
Optimize sibling and tail recursive calls.
|
|
|
|
@item -ftrapv
|
|
@opindex ftrapv
|
|
This option generates traps for signed overflow on addition, subtraction,
|
|
multiplication operations.
|
|
|
|
@item -fno-inline
|
|
@opindex fno-inline
|
|
Don't pay attention to the @code{inline} keyword. Normally this option
|
|
is used to keep the compiler from expanding any functions inline.
|
|
Note that if you are not optimizing, no functions can be expanded inline.
|
|
|
|
@item -finline-functions
|
|
@opindex finline-functions
|
|
Integrate all simple functions into their callers. The compiler
|
|
heuristically decides which functions are simple enough to be worth
|
|
integrating in this way.
|
|
|
|
If all calls to a given function are integrated, and the function is
|
|
declared @code{static}, then the function is normally not output as
|
|
assembler code in its own right.
|
|
|
|
@item -finline-limit=@var{n}
|
|
@opindex finline-limit
|
|
By default, gcc limits the size of functions that can be inlined. This flag
|
|
allows the control of this limit for functions that are explicitly marked as
|
|
inline (ie marked with the inline keyword or defined within the class
|
|
definition in c++). @var{n} is the size of functions that can be inlined in
|
|
number of pseudo instructions (not counting parameter handling). The default
|
|
value of @var{n} is 600.
|
|
Increasing this value can result in more inlined code at
|
|
the cost of compilation time and memory consumption. Decreasing usually makes
|
|
the compilation faster and less code will be inlined (which presumably
|
|
means slower programs). This option is particularly useful for programs that
|
|
use inlining heavily such as those based on recursive templates with C++.
|
|
|
|
@emph{Note:} pseudo instruction represents, in this particular context, an
|
|
abstract measurement of function's size. In no way, it represents a count
|
|
of assembly instructions and as such its exact meaning might change from one
|
|
release to an another.
|
|
|
|
@item -fkeep-inline-functions
|
|
@opindex fkeep-inline-functions
|
|
Even if all calls to a given function are integrated, and the function
|
|
is declared @code{static}, nevertheless output a separate run-time
|
|
callable version of the function. This switch does not affect
|
|
@code{extern inline} functions.
|
|
|
|
@item -fkeep-static-consts
|
|
@opindex fkeep-static-consts
|
|
Emit variables declared @code{static const} when optimization isn't turned
|
|
on, even if the variables aren't referenced.
|
|
|
|
GCC enables this option by default. If you want to force the compiler to
|
|
check if the variable was referenced, regardless of whether or not
|
|
optimization is turned on, use the @option{-fno-keep-static-consts} option.
|
|
|
|
@item -fmerge-constants
|
|
Attempt to merge identical constants (string constants and floating point
|
|
constants) accross compilation units.
|
|
|
|
This option is default for optimized compilation if assembler and linker
|
|
support it. Use @option{-fno-merge-constants} to inhibit this behavior.
|
|
|
|
@item -fmerge-all-constants
|
|
Attempt to merge identical constants and identical variables.
|
|
|
|
This option implies @option{-fmerge-constants}. In addition to
|
|
@option{-fmerge-constants} this considers e.g. even constant initialized
|
|
arrays or initialized constant variables with integral or floating point
|
|
types. Languages like C or C++ require each non-automatic variable to
|
|
have distinct location, so using this option will result in non-conforming
|
|
behavior.
|
|
|
|
@item -fno-function-cse
|
|
@opindex fno-function-cse
|
|
Do not put function addresses in registers; make each instruction that
|
|
calls a constant function contain the function's address explicitly.
|
|
|
|
This option results in less efficient code, but some strange hacks
|
|
that alter the assembler output may be confused by the optimizations
|
|
performed when this option is not used.
|
|
|
|
@item -ffast-math
|
|
@opindex ffast-math
|
|
Sets @option{-fno-math-errno}, @option{-funsafe-math-optimizations}, and @*
|
|
@option{-fno-trapping-math}.
|
|
|
|
This option causes the preprocessor macro @code{__FAST_MATH__} to be defined.
|
|
|
|
This option should never be turned on by any @option{-O} option since
|
|
it can result in incorrect output for programs which depend on
|
|
an exact implementation of IEEE or ISO rules/specifications for
|
|
math functions.
|
|
|
|
@item -fno-math-errno
|
|
@opindex fno-math-errno
|
|
Do not set ERRNO after calling math functions that are executed
|
|
with a single instruction, e.g., sqrt. A program that relies on
|
|
IEEE exceptions for math error handling may want to use this flag
|
|
for speed while maintaining IEEE arithmetic compatibility.
|
|
|
|
This option should never be turned on by any @option{-O} option since
|
|
it can result in incorrect output for programs which depend on
|
|
an exact implementation of IEEE or ISO rules/specifications for
|
|
math functions.
|
|
|
|
The default is @option{-fmath-errno}.
|
|
|
|
@item -funsafe-math-optimizations
|
|
@opindex funsafe-math-optimizations
|
|
Allow optimizations for floating-point arithmetic that (a) assume
|
|
that arguments and results are valid and (b) may violate IEEE or
|
|
ANSI standards. When used at link-time, it may include libraries
|
|
or startup files that change the default FPU control word or other
|
|
similar optimizations.
|
|
|
|
This option should never be turned on by any @option{-O} option since
|
|
it can result in incorrect output for programs which depend on
|
|
an exact implementation of IEEE or ISO rules/specifications for
|
|
math functions.
|
|
|
|
The default is @option{-fno-unsafe-math-optimizations}.
|
|
|
|
@item -fno-trapping-math
|
|
@opindex fno-trapping-math
|
|
Compile code assuming that floating-point operations cannot generate
|
|
user-visible traps. Setting this option may allow faster code
|
|
if one relies on ``non-stop'' IEEE arithmetic, for example.
|
|
|
|
This option should never be turned on by any @option{-O} option since
|
|
it can result in incorrect output for programs which depend on
|
|
an exact implementation of IEEE or ISO rules/specifications for
|
|
math functions.
|
|
|
|
The default is @option{-ftrapping-math}.
|
|
@end table
|
|
|
|
The following options control specific optimizations. The @option{-O2}
|
|
option turns on all of these optimizations except @option{-funroll-loops}
|
|
and @option{-funroll-all-loops}. On most machines, the @option{-O} option
|
|
turns on the @option{-fthread-jumps} and @option{-fdelayed-branch} options,
|
|
but specific machines may handle it differently.
|
|
|
|
You can use the following flags in the rare cases when ``fine-tuning''
|
|
of optimizations to be performed is desired.
|
|
|
|
Not all of the optimizations performed by GCC have @option{-f} options
|
|
to control them.
|
|
|
|
@table @gcctabopt
|
|
@item -fstrength-reduce
|
|
@opindex fstrength-reduce
|
|
Perform the optimizations of loop strength reduction and
|
|
elimination of iteration variables.
|
|
|
|
@item -fthread-jumps
|
|
@opindex fthread-jumps
|
|
Perform optimizations where we check to see if a jump branches to a
|
|
location where another comparison subsumed by the first is found. If
|
|
so, the first branch is redirected to either the destination of the
|
|
second branch or a point immediately following it, depending on whether
|
|
the condition is known to be true or false.
|
|
|
|
@item -fcse-follow-jumps
|
|
@opindex fcse-follow-jumps
|
|
In common subexpression elimination, scan through jump instructions
|
|
when the target of the jump is not reached by any other path. For
|
|
example, when CSE encounters an @code{if} statement with an
|
|
@code{else} clause, CSE will follow the jump when the condition
|
|
tested is false.
|
|
|
|
@item -fcse-skip-blocks
|
|
@opindex fcse-skip-blocks
|
|
This is similar to @option{-fcse-follow-jumps}, but causes CSE to
|
|
follow jumps which conditionally skip over blocks. When CSE
|
|
encounters a simple @code{if} statement with no else clause,
|
|
@option{-fcse-skip-blocks} causes CSE to follow the jump around the
|
|
body of the @code{if}.
|
|
|
|
@item -frerun-cse-after-loop
|
|
@opindex frerun-cse-after-loop
|
|
Re-run common subexpression elimination after loop optimizations has been
|
|
performed.
|
|
|
|
@item -frerun-loop-opt
|
|
@opindex frerun-loop-opt
|
|
Run the loop optimizer twice.
|
|
|
|
@item -fgcse
|
|
@opindex fgcse
|
|
Perform a global common subexpression elimination pass.
|
|
This pass also performs global constant and copy propagation.
|
|
|
|
@emph{Note:} When compiling a program using computed gotos, a GCC
|
|
extension, you may get better runtime performance if you disable
|
|
the global common subexpression elmination pass by adding
|
|
@option{-fno-gcse} to the command line.
|
|
|
|
@item -fgcse-lm
|
|
@opindex fgcse-lm
|
|
When @option{-fgcse-lm} is enabled, global common subexpression elimination will
|
|
attempt to move loads which are only killed by stores into themselves. This
|
|
allows a loop containing a load/store sequence to be changed to a load outside
|
|
the loop, and a copy/store within the loop.
|
|
|
|
@item -fgcse-sm
|
|
@opindex fgcse-sm
|
|
When @option{-fgcse-sm} is enabled, A store motion pass is run after global common
|
|
subexpression elimination. This pass will attempt to move stores out of loops.
|
|
When used in conjunction with @option{-fgcse-lm}, loops containing a load/store sequence
|
|
can be changed to a load before the loop and a store after the loop.
|
|
|
|
@item -fdelete-null-pointer-checks
|
|
@opindex fdelete-null-pointer-checks
|
|
Use global dataflow analysis to identify and eliminate useless checks
|
|
for null pointers. The compiler assumes that dereferencing a null
|
|
pointer would have halted the program. If a pointer is checked after
|
|
it has already been dereferenced, it cannot be null.
|
|
|
|
In some environments, this assumption is not true, and programs can
|
|
safely dereference null pointers. Use
|
|
@option{-fno-delete-null-pointer-checks} to disable this optimization
|
|
for programs which depend on that behavior.
|
|
|
|
@item -fexpensive-optimizations
|
|
@opindex fexpensive-optimizations
|
|
Perform a number of minor optimizations that are relatively expensive.
|
|
|
|
@item -foptimize-register-move
|
|
@itemx -fregmove
|
|
@opindex foptimize-register-move
|
|
@opindex fregmove
|
|
Attempt to reassign register numbers in move instructions and as
|
|
operands of other simple instructions in order to maximize the amount of
|
|
register tying. This is especially helpful on machines with two-operand
|
|
instructions. GCC enables this optimization by default with @option{-O2}
|
|
or higher.
|
|
|
|
Note @option{-fregmove} and @option{-foptimize-register-move} are the same
|
|
optimization.
|
|
|
|
@item -fdelayed-branch
|
|
@opindex fdelayed-branch
|
|
If supported for the target machine, attempt to reorder instructions
|
|
to exploit instruction slots available after delayed branch
|
|
instructions.
|
|
|
|
@item -fschedule-insns
|
|
@opindex fschedule-insns
|
|
If supported for the target machine, attempt to reorder instructions to
|
|
eliminate execution stalls due to required data being unavailable. This
|
|
helps machines that have slow floating point or memory load instructions
|
|
by allowing other instructions to be issued until the result of the load
|
|
or floating point instruction is required.
|
|
|
|
@item -fschedule-insns2
|
|
@opindex fschedule-insns2
|
|
Similar to @option{-fschedule-insns}, but requests an additional pass of
|
|
instruction scheduling after register allocation has been done. This is
|
|
especially useful on machines with a relatively small number of
|
|
registers and where memory load instructions take more than one cycle.
|
|
|
|
@item -ffunction-sections
|
|
@itemx -fdata-sections
|
|
@opindex ffunction-sections
|
|
@opindex fdata-sections
|
|
Place each function or data item into its own section in the output
|
|
file if the target supports arbitrary sections. The name of the
|
|
function or the name of the data item determines the section's name
|
|
in the output file.
|
|
|
|
Use these options on systems where the linker can perform optimizations
|
|
to improve locality of reference in the instruction space. HPPA
|
|
processors running HP-UX and Sparc processors running Solaris 2 have
|
|
linkers with such optimizations. Other systems using the ELF object format
|
|
as well as AIX may have these optimizations in the future.
|
|
|
|
Only use these options when there are significant benefits from doing
|
|
so. When you specify these options, the assembler and linker will
|
|
create larger object and executable files and will also be slower.
|
|
You will not be able to use @code{gprof} on all systems if you
|
|
specify this option and you may have problems with debugging if
|
|
you specify both this option and @option{-g}.
|
|
|
|
@item -fcaller-saves
|
|
@opindex fcaller-saves
|
|
Enable values to be allocated in registers that will be clobbered by
|
|
function calls, by emitting extra instructions to save and restore the
|
|
registers around such calls. Such allocation is done only when it
|
|
seems to result in better code than would otherwise be produced.
|
|
|
|
This option is always enabled by default on certain machines, usually
|
|
those which have no call-preserved registers to use instead.
|
|
|
|
For all machines, optimization level 2 and higher enables this flag by
|
|
default.
|
|
|
|
@item -funroll-loops
|
|
@opindex funroll-loops
|
|
Unroll loops whose number of iterations can be determined at compile
|
|
time or upon entry to the loop. @option{-funroll-loops} implies both
|
|
@option{-fstrength-reduce} and @option{-frerun-cse-after-loop}. This
|
|
option makes code larger, and may or may not make it run faster.
|
|
|
|
@item -funroll-all-loops
|
|
@opindex funroll-all-loops
|
|
Unroll all loops, even if their number of iterations is uncertain when
|
|
the loop is entered. This usually makes programs run more slowly.
|
|
@option{-funroll-all-loops} implies the same options as
|
|
@option{-funroll-loops},
|
|
|
|
@item -fprefetch-loop-arrays
|
|
@opindex fprefetch-loop-arrays
|
|
If supported by the target machine, generate instructions to prefetch
|
|
memory to improve the performance of loops that access large arrays.
|
|
|
|
@item -fmove-all-movables
|
|
@opindex fmove-all-movables
|
|
Forces all invariant computations in loops to be moved
|
|
outside the loop.
|
|
|
|
@item -freduce-all-givs
|
|
@opindex freduce-all-givs
|
|
Forces all general-induction variables in loops to be
|
|
strength-reduced.
|
|
|
|
@emph{Note:} When compiling programs written in Fortran,
|
|
@option{-fmove-all-movables} and @option{-freduce-all-givs} are enabled
|
|
by default when you use the optimizer.
|
|
|
|
These options may generate better or worse code; results are highly
|
|
dependent on the structure of loops within the source code.
|
|
|
|
These two options are intended to be removed someday, once
|
|
they have helped determine the efficacy of various
|
|
approaches to improving loop optimizations.
|
|
|
|
Please let us (@w{@email{gcc@@gcc.gnu.org}} and @w{@email{fortran@@gnu.org}})
|
|
know how use of these options affects
|
|
the performance of your production code.
|
|
We're very interested in code that runs @emph{slower}
|
|
when these options are @emph{enabled}.
|
|
|
|
@item -fno-peephole
|
|
@itemx -fno-peephole2
|
|
@opindex fno-peephole
|
|
@opindex fno-peephole2
|
|
Disable any machine-specific peephole optimizations. The difference
|
|
between @option{-fno-peephole} and @option{-fno-peephole2} is in how they
|
|
are implemented in the compiler; some targets use one, some use the
|
|
other, a few use both.
|
|
|
|
@item -fbranch-probabilities
|
|
@opindex fbranch-probabilities
|
|
After running a program compiled with @option{-fprofile-arcs}
|
|
(@pxref{Debugging Options,, Options for Debugging Your Program or
|
|
@command{gcc}}), you can compile it a second time using
|
|
@option{-fbranch-probabilities}, to improve optimizations based on
|
|
the number of times each branch was taken. When the program
|
|
compiled with @option{-fprofile-arcs} exits it saves arc execution
|
|
counts to a file called @file{@var{sourcename}.da} for each source
|
|
file The information in this data file is very dependent on the
|
|
structure of the generated code, so you must use the same source code
|
|
and the same optimization options for both compilations.
|
|
|
|
With @option{-fbranch-probabilities}, GCC puts a @samp{REG_EXEC_COUNT}
|
|
note on the first instruction of each basic block, and a
|
|
@samp{REG_BR_PROB} note on each @samp{JUMP_INSN} and @samp{CALL_INSN}.
|
|
These can be used to improve optimization. Currently, they are only
|
|
used in one place: in @file{reorg.c}, instead of guessing which path a
|
|
branch is mostly to take, the @samp{REG_BR_PROB} values are used to
|
|
exactly determine which path is taken more often.
|
|
|
|
@item -fno-guess-branch-probability
|
|
@opindex fno-guess-branch-probability
|
|
Do not guess branch probabilities using a randomized model.
|
|
|
|
Sometimes gcc will opt to use a randomized model to guess branch
|
|
probabilities, when none are available from either profiling feedback
|
|
(@option{-fprofile-arcs}) or @samp{__builtin_expect}. This means that
|
|
different runs of the compiler on the same program may produce different
|
|
object code.
|
|
|
|
In a hard real-time system, people don't want different runs of the
|
|
compiler to produce code that has different behavior; minimizing
|
|
non-determinism is of paramount import. This switch allows users to
|
|
reduce non-determinism, possibly at the expense of inferior
|
|
optimization.
|
|
|
|
@item -fstrict-aliasing
|
|
@opindex fstrict-aliasing
|
|
Allows the compiler to assume the strictest aliasing rules applicable to
|
|
the language being compiled. For C (and C++), this activates
|
|
optimizations based on the type of expressions. In particular, an
|
|
object of one type is assumed never to reside at the same address as an
|
|
object of a different type, unless the types are almost the same. For
|
|
example, an @code{unsigned int} can alias an @code{int}, but not a
|
|
@code{void*} or a @code{double}. A character type may alias any other
|
|
type.
|
|
|
|
Pay special attention to code like this:
|
|
@example
|
|
union a_union @{
|
|
int i;
|
|
double d;
|
|
@};
|
|
|
|
int f() @{
|
|
a_union t;
|
|
t.d = 3.0;
|
|
return t.i;
|
|
@}
|
|
@end example
|
|
The practice of reading from a different union member than the one most
|
|
recently written to (called ``type-punning'') is common. Even with
|
|
@option{-fstrict-aliasing}, type-punning is allowed, provided the memory
|
|
is accessed through the union type. So, the code above will work as
|
|
expected. However, this code might not:
|
|
@example
|
|
int f() @{
|
|
a_union t;
|
|
int* ip;
|
|
t.d = 3.0;
|
|
ip = &t.i;
|
|
return *ip;
|
|
@}
|
|
@end example
|
|
|
|
Every language that wishes to perform language-specific alias analysis
|
|
should define a function that computes, given an @code{tree}
|
|
node, an alias set for the node. Nodes in different alias sets are not
|
|
allowed to alias. For an example, see the C front-end function
|
|
@code{c_get_alias_set}.
|
|
|
|
@item -falign-functions
|
|
@itemx -falign-functions=@var{n}
|
|
@opindex falign-functions
|
|
Align the start of functions to the next power-of-two greater than
|
|
@var{n}, skipping up to @var{n} bytes. For instance,
|
|
@option{-falign-functions=32} aligns functions to the next 32-byte
|
|
boundary, but @option{-falign-functions=24} would align to the next
|
|
32-byte boundary only if this can be done by skipping 23 bytes or less.
|
|
|
|
@option{-fno-align-functions} and @option{-falign-functions=1} are
|
|
equivalent and mean that functions will not be aligned.
|
|
|
|
Some assemblers only support this flag when @var{n} is a power of two;
|
|
in that case, it is rounded up.
|
|
|
|
If @var{n} is not specified, use a machine-dependent default.
|
|
|
|
@item -falign-labels
|
|
@itemx -falign-labels=@var{n}
|
|
@opindex falign-labels
|
|
Align all branch targets to a power-of-two boundary, skipping up to
|
|
@var{n} bytes like @option{-falign-functions}. This option can easily
|
|
make code slower, because it must insert dummy operations for when the
|
|
branch target is reached in the usual flow of the code.
|
|
|
|
If @option{-falign-loops} or @option{-falign-jumps} are applicable and
|
|
are greater than this value, then their values are used instead.
|
|
|
|
If @var{n} is not specified, use a machine-dependent default which is
|
|
very likely to be @samp{1}, meaning no alignment.
|
|
|
|
@item -falign-loops
|
|
@itemx -falign-loops=@var{n}
|
|
@opindex falign-loops
|
|
Align loops to a power-of-two boundary, skipping up to @var{n} bytes
|
|
like @option{-falign-functions}. The hope is that the loop will be
|
|
executed many times, which will make up for any execution of the dummy
|
|
operations.
|
|
|
|
If @var{n} is not specified, use a machine-dependent default.
|
|
|
|
@item -falign-jumps
|
|
@itemx -falign-jumps=@var{n}
|
|
@opindex falign-jumps
|
|
Align branch targets to a power-of-two boundary, for branch targets
|
|
where the targets can only be reached by jumping, skipping up to @var{n}
|
|
bytes like @option{-falign-functions}. In this case, no dummy operations
|
|
need be executed.
|
|
|
|
If @var{n} is not specified, use a machine-dependent default.
|
|
|
|
@item -fssa
|
|
@opindex fssa
|
|
Perform optimizations in static single assignment form. Each function's
|
|
flow graph is translated into SSA form, optimizations are performed, and
|
|
the flow graph is translated back from SSA form. Users should not
|
|
specify this option, since it is not yet ready for production use.
|
|
|
|
@item -fssa-ccp
|
|
@opindex fssa-ccp
|
|
Perform Sparse Conditional Constant Propagation in SSA form. Requires
|
|
@option{-fssa}. Like @option{-fssa}, this is an experimental feature.
|
|
|
|
@item -fssa-dce
|
|
@opindex fssa-dce
|
|
Perform aggressive dead-code elimination in SSA form. Requires @option{-fssa}.
|
|
Like @option{-fssa}, this is an experimental feature.
|
|
|
|
@item -fsingle-precision-constant
|
|
@opindex fsingle-precision-constant
|
|
Treat floating point constant as single precision constant instead of
|
|
implicitly converting it to double precision constant.
|
|
|
|
@item -frename-registers
|
|
@opindex frename-registers
|
|
Attempt to avoid false dependencies in scheduled code by making use
|
|
of registers left over after register allocation. This optimization
|
|
will most benefit processors with lots of registers. It can, however,
|
|
make debugging impossible, since variables will no longer stay in
|
|
a ``home register''.
|
|
|
|
@item -fno-cprop-registers
|
|
@opindex fno-cprop-registers
|
|
After register allocation and post-register allocation instruction splitting,
|
|
we perform a copy-propagation pass to try to reduce scheduling dependencies
|
|
and occasionally eliminate the copy.
|
|
|
|
@item --param @var{name}=@var{value}
|
|
@opindex param
|
|
In some places, GCC uses various constants to control the amount of
|
|
optimization that is done. For example, GCC will not inline functions
|
|
that contain more that a certain number of instructions. You can
|
|
control some of these constants on the command-line using the
|
|
@option{--param} option.
|
|
|
|
In each case, the @var{value} is an integer. The allowable choices for
|
|
@var{name} are given in the following table:
|
|
|
|
@table @gcctabopt
|
|
@item max-delay-slot-insn-search
|
|
The maximum number of instructions to consider when looking for an
|
|
instruction to fill a delay slot. If more than this arbitrary number of
|
|
instructions is searched, the time savings from filling the delay slot
|
|
will be minimal so stop searching. Increasing values mean more
|
|
aggressive optimization, making the compile time increase with probably
|
|
small improvement in executable run time.
|
|
|
|
@item max-delay-slot-live-search
|
|
When trying to fill delay slots, the maximum number of instructions to
|
|
consider when searching for a block with valid live register
|
|
information. Increasing this arbitrarily chosen value means more
|
|
aggressive optimization, increasing the compile time. This parameter
|
|
should be removed when the delay slot code is rewritten to maintain the
|
|
control-flow graph.
|
|
|
|
@item max-gcse-memory
|
|
The approximate maximum amount of memory that will be allocated in
|
|
order to perform the global common subexpression elimination
|
|
optimization. If more memory than specified is required, the
|
|
optimization will not be done.
|
|
|
|
@item max-gcse-passes
|
|
The maximum number of passes of GCSE to run.
|
|
|
|
@item max-pending-list-length
|
|
The maximum number of pending dependencies scheduling will allow
|
|
before flushing the current state and starting over. Large functions
|
|
with few branches or calls can create excessively large lists which
|
|
needlessly consume memory and resources.
|
|
|
|
@item max-inline-insns
|
|
If an function contains more than this many instructions, it
|
|
will not be inlined. This option is precisely equivalent to
|
|
@option{-finline-limit}.
|
|
|
|
@end table
|
|
@end table
|
|
|
|
@node Preprocessor Options
|
|
@section Options Controlling the Preprocessor
|
|
@cindex preprocessor options
|
|
@cindex options, preprocessor
|
|
|
|
These options control the C preprocessor, which is run on each C source
|
|
file before actual compilation.
|
|
|
|
If you use the @option{-E} option, nothing is done except preprocessing.
|
|
Some of these options make sense only together with @option{-E} because
|
|
they cause the preprocessor output to be unsuitable for actual
|
|
compilation.
|
|
|
|
@table @gcctabopt
|
|
@item -include @var{file}
|
|
@opindex include
|
|
Process @var{file} as input before processing the regular input file.
|
|
In effect, the contents of @var{file} are compiled first. Any @option{-D}
|
|
and @option{-U} options on the command line are always processed before
|
|
@option{-include @var{file}}, regardless of the order in which they are
|
|
written. All the @option{-include} and @option{-imacros} options are
|
|
processed in the order in which they are written.
|
|
|
|
@item -imacros @var{file}
|
|
@opindex imacros
|
|
Process @var{file} as input, discarding the resulting output, before
|
|
processing the regular input file. Because the output generated from
|
|
@var{file} is discarded, the only effect of @option{-imacros @var{file}}
|
|
is to make the macros defined in @var{file} available for use in the
|
|
main input. All the @option{-include} and @option{-imacros} options are
|
|
processed in the order in which they are written.
|
|
|
|
@item -idirafter @var{dir}
|
|
@opindex idirafter
|
|
@cindex second include path
|
|
Add the directory @var{dir} to the second include path. The directories
|
|
on the second include path are searched when a header file is not found
|
|
in any of the directories in the main include path (the one that
|
|
@option{-I} adds to).
|
|
|
|
@item -iprefix @var{prefix}
|
|
@opindex iprefix
|
|
Specify @var{prefix} as the prefix for subsequent @option{-iwithprefix}
|
|
options.
|
|
|
|
@item -iwithprefix @var{dir}
|
|
@opindex iwithprefix
|
|
Add a directory to the second include path. The directory's name is
|
|
made by concatenating @var{prefix} and @var{dir}, where @var{prefix} was
|
|
specified previously with @option{-iprefix}. If you have not specified a
|
|
prefix yet, the directory containing the installed passes of the
|
|
compiler is used as the default.
|
|
|
|
@item -iwithprefixbefore @var{dir}
|
|
@opindex iwithprefixbefore
|
|
Add a directory to the main include path. The directory's name is made
|
|
by concatenating @var{prefix} and @var{dir}, as in the case of
|
|
@option{-iwithprefix}.
|
|
|
|
@item -isystem @var{dir}
|
|
@opindex isystem
|
|
Add a directory to the beginning of the second include path, marking it
|
|
as a system directory, so that it gets the same special treatment as
|
|
is applied to the standard system directories.
|
|
|
|
@item -nostdinc
|
|
@opindex nostdinc
|
|
Do not search the standard system directories for header files. Only
|
|
the directories you have specified with @option{-I} options (and the
|
|
current directory, if appropriate) are searched. @xref{Directory
|
|
Options}, for information on @option{-I}.
|
|
|
|
By using both @option{-nostdinc} and @option{-I-}, you can limit the include-file
|
|
search path to only those directories you specify explicitly.
|
|
|
|
@item -remap
|
|
@opindex remap
|
|
When searching for a header file in a directory, remap file names if a
|
|
file named @file{header.gcc} exists in that directory. This can be used
|
|
to work around limitations of file systems with file name restrictions.
|
|
The @file{header.gcc} file should contain a series of lines with two
|
|
tokens on each line: the first token is the name to map, and the second
|
|
token is the actual name to use.
|
|
|
|
@item -undef
|
|
@opindex undef
|
|
Do not predefine any nonstandard macros. (Including architecture flags).
|
|
|
|
@item -E
|
|
@opindex E
|
|
Run only the C preprocessor. Preprocess all the C source files
|
|
specified and output the results to standard output or to the
|
|
specified output file.
|
|
|
|
@item -C
|
|
@opindex C
|
|
Tell the preprocessor not to discard comments. Used with the
|
|
@option{-E} option.
|
|
|
|
@item -P
|
|
@opindex P
|
|
Tell the preprocessor not to generate @samp{#line} directives.
|
|
Used with the @option{-E} option.
|
|
|
|
@cindex make
|
|
@cindex dependencies, make
|
|
@item -M
|
|
@opindex M
|
|
Instead of outputting the result of preprocessing, output a rule
|
|
suitable for @code{make} describing the dependencies of the main source
|
|
file. The preprocessor outputs one @code{make} rule containing the
|
|
object file name for that source file, a colon, and the names of all the
|
|
included files. Unless overridden explicitly, the object file name
|
|
consists of the basename of the source file with any suffix replaced with
|
|
object file suffix. If there are many included files then the
|
|
rule is split into several lines using @samp{\}-newline.
|
|
|
|
@option{-M} implies @option{-E}.
|
|
|
|
@item -MM
|
|
@opindex MM
|
|
Like @option{-M}, but mention only the files included with @samp{#include
|
|
"@var{file}"}. System header files included with @samp{#include
|
|
<@var{file}>} are omitted.
|
|
|
|
@item -MD
|
|
@opindex MD
|
|
Like @option{-M} but the dependency information is written to a file
|
|
rather than stdout. @code{gcc} will use the same file name and
|
|
directory as the object file, but with the suffix @file{.d} instead.
|
|
|
|
This is in addition to compiling the main file as specified---@option{-MD}
|
|
does not inhibit ordinary compilation the way @option{-M} does,
|
|
unless you also specify @option{-MG}.
|
|
|
|
With Mach, you can use the utility @code{md} to merge multiple
|
|
dependency files into a single dependency file suitable for using with
|
|
the @samp{make} command.
|
|
|
|
@item -MMD
|
|
@opindex MMD
|
|
Like @option{-MD} except mention only user header files, not system
|
|
-header files.
|
|
|
|
@item -MF @var{file}
|
|
@opindex MF
|
|
When used with @option{-M} or @option{-MM}, specifies a file to write the
|
|
dependencies to. This allows the preprocessor to write the preprocessed
|
|
file to stdout normally. If no @option{-MF} switch is given, CPP sends
|
|
the rules to stdout and suppresses normal preprocessed output.
|
|
|
|
Another way to specify output of a @code{make} rule is by setting
|
|
the environment variable @env{DEPENDENCIES_OUTPUT} (@pxref{Environment
|
|
Variables}).
|
|
|
|
@item -MG
|
|
@opindex MG
|
|
When used with @option{-M} or @option{-MM}, @option{-MG} says to treat missing
|
|
header files as generated files and assume they live in the same
|
|
directory as the source file. It suppresses preprocessed output, as a
|
|
missing header file is ordinarily an error.
|
|
|
|
This feature is used in automatic updating of makefiles.
|
|
|
|
@item -MP
|
|
@opindex MP
|
|
This option instructs CPP to add a phony target for each dependency
|
|
other than the main file, causing each to depend on nothing. These
|
|
dummy rules work around errors @code{make} gives if you remove header
|
|
files without updating the @code{Makefile} to match.
|
|
|
|
This is typical output:-
|
|
|
|
@smallexample
|
|
/tmp/test.o: /tmp/test.c /tmp/test.h
|
|
|
|
/tmp/test.h:
|
|
@end smallexample
|
|
|
|
@item -MQ @var{target}
|
|
@item -MT @var{target}
|
|
@opindex MQ
|
|
@opindex MT
|
|
By default CPP uses the main file name, including any path, and appends
|
|
the object suffix, normally ``.o'', to it to obtain the name of the
|
|
target for dependency generation. With @option{-MT} you can specify a
|
|
target yourself, overriding the default one.
|
|
|
|
If you want multiple targets, you can specify them as a single argument
|
|
to @option{-MT}, or use multiple @option{-MT} options.
|
|
|
|
The targets you specify are output in the order they appear on the
|
|
command line. @option{-MQ} is identical to @option{-MT}, except that the
|
|
target name is quoted for Make, but with @option{-MT} it isn't. For
|
|
example, @option{-MT '$(objpfx)foo.o'} gives
|
|
|
|
@smallexample
|
|
$(objpfx)foo.o: /tmp/foo.c
|
|
@end smallexample
|
|
|
|
but @option{-MQ '$(objpfx)foo.o'} gives
|
|
|
|
@smallexample
|
|
$$(objpfx)foo.o: /tmp/foo.c
|
|
@end smallexample
|
|
|
|
The default target is automatically quoted, as if it were given with
|
|
@option{-MQ}.
|
|
|
|
@item -H
|
|
@opindex H
|
|
Print the name of each header file used, in addition to other normal
|
|
activities.
|
|
|
|
@item -A@var{question}(@var{answer})
|
|
@opindex A
|
|
Assert the answer @var{answer} for @var{question}, in case it is tested
|
|
with a preprocessing conditional such as @samp{#if
|
|
#@var{question}(@var{answer})}. @option{-A-} disables the standard
|
|
assertions that normally describe the target machine.
|
|
|
|
@item -D@var{macro}
|
|
@opindex D
|
|
Define macro @var{macro} with the string @samp{1} as its definition.
|
|
|
|
@item -D@var{macro}=@var{defn}
|
|
Define macro @var{macro} as @var{defn}. All instances of @option{-D} on
|
|
the command line are processed before any @option{-U} options.
|
|
|
|
Any @option{-D} and @option{-U} options on the command line are processed in
|
|
order, and always before @option{-imacros @var{file}}, regardless of the
|
|
order in which they are written.
|
|
|
|
@item -U@var{macro}
|
|
@opindex U
|
|
Undefine macro @var{macro}. @option{-U} options are evaluated after all
|
|
@option{-D} options, but before any @option{-include} and @option{-imacros}
|
|
options.
|
|
|
|
Any @option{-D} and @option{-U} options on the command line are processed in
|
|
order, and always before @option{-imacros @var{file}}, regardless of the
|
|
order in which they are written.
|
|
|
|
@item -dM
|
|
@opindex dM
|
|
Tell the preprocessor to output only a list of the macro definitions
|
|
that are in effect at the end of preprocessing. Used with the @option{-E}
|
|
option.
|
|
|
|
@item -dD
|
|
@opindex dD
|
|
Tell the preprocessing to pass all macro definitions into the output, in
|
|
their proper sequence in the rest of the output.
|
|
|
|
@item -dN
|
|
@opindex dN
|
|
Like @option{-dD} except that the macro arguments and contents are omitted.
|
|
Only @samp{#define @var{name}} is included in the output.
|
|
|
|
@item -dI
|
|
@opindex dI
|
|
Output @samp{#include} directives in addition to the result of
|
|
preprocessing.
|
|
|
|
@item -fpreprocessed
|
|
@opindex fpreprocessed
|
|
Indicate to the preprocessor that the input file has already been
|
|
preprocessed. This suppresses things like macro expansion, trigraph
|
|
conversion, escaped newline splicing, and processing of most directives.
|
|
The preprocessor still recognizes and removes comments, so that you can
|
|
pass a file preprocessed with @option{-C} to the compiler without
|
|
problems. In this mode the integrated preprocessor is little more than
|
|
a tokenizer for the front ends.
|
|
|
|
@option{-fpreprocessed} is implicit if the input file has one of the
|
|
extensions @samp{i}, @samp{ii} or @samp{mi}. These are the extensions
|
|
that GCC uses for preprocessed files created by @option{-save-temps}.
|
|
|
|
@item -trigraphs
|
|
@opindex trigraphs
|
|
Process ISO standard trigraph sequences. These are three-character
|
|
sequences, all starting with @samp{??}, that are defined by ISO C to
|
|
stand for single characters. For example, @samp{??/} stands for
|
|
@samp{\}, so @samp{'??/n'} is a character constant for a newline. By
|
|
default, GCC ignores trigraphs, but in standard-conforming modes it
|
|
converts them. See the @option{-std} and @option{-ansi} options.
|
|
|
|
The nine trigraph sequences are
|
|
@table @samp
|
|
@item ??(
|
|
@expansion{} @samp{[}
|
|
|
|
@item ??)
|
|
@expansion{} @samp{]}
|
|
|
|
@item ??<
|
|
@expansion{} @samp{@{}
|
|
|
|
@item ??>
|
|
@expansion{} @samp{@}}
|
|
|
|
@item ??=
|
|
@expansion{} @samp{#}
|
|
|
|
@item ??/
|
|
@expansion{} @samp{\}
|
|
|
|
@item ??'
|
|
@expansion{} @samp{^}
|
|
|
|
@item ??!
|
|
@expansion{} @samp{|}
|
|
|
|
@item ??-
|
|
@expansion{} @samp{~}
|
|
|
|
@end table
|
|
|
|
Trigraph support is not popular, so many compilers do not implement it
|
|
properly. Portable code should not rely on trigraphs being either
|
|
converted or ignored.
|
|
|
|
@item -Wp,@var{option}
|
|
@opindex Wp
|
|
Pass @var{option} as an option to the preprocessor. If @var{option}
|
|
contains commas, it is split into multiple options at the commas.
|
|
@end table
|
|
|
|
@node Assembler Options
|
|
@section Passing Options to the Assembler
|
|
|
|
@c prevent bad page break with this line
|
|
You can pass options to the assembler.
|
|
|
|
@table @gcctabopt
|
|
@item -Wa,@var{option}
|
|
@opindex Wa
|
|
Pass @var{option} as an option to the assembler. If @var{option}
|
|
contains commas, it is split into multiple options at the commas.
|
|
@end table
|
|
|
|
@node Link Options
|
|
@section Options for Linking
|
|
@cindex link options
|
|
@cindex options, linking
|
|
|
|
These options come into play when the compiler links object files into
|
|
an executable output file. They are meaningless if the compiler is
|
|
not doing a link step.
|
|
|
|
@table @gcctabopt
|
|
@cindex file names
|
|
@item @var{object-file-name}
|
|
A file name that does not end in a special recognized suffix is
|
|
considered to name an object file or library. (Object files are
|
|
distinguished from libraries by the linker according to the file
|
|
contents.) If linking is done, these object files are used as input
|
|
to the linker.
|
|
|
|
@item -c
|
|
@itemx -S
|
|
@itemx -E
|
|
@opindex c
|
|
@opindex S
|
|
@opindex E
|
|
If any of these options is used, then the linker is not run, and
|
|
object file names should not be used as arguments. @xref{Overall
|
|
Options}.
|
|
|
|
@cindex Libraries
|
|
@item -l@var{library}
|
|
@itemx -l @var{library}
|
|
@opindex l
|
|
Search the library named @var{library} when linking. (The second
|
|
alternative with the library as a separate argument is only for
|
|
POSIX compliance and is not recommended.)
|
|
|
|
It makes a difference where in the command you write this option; the
|
|
linker searches and processes libraries and object files in the order they
|
|
are specified. Thus, @samp{foo.o -lz bar.o} searches library @samp{z}
|
|
after file @file{foo.o} but before @file{bar.o}. If @file{bar.o} refers
|
|
to functions in @samp{z}, those functions may not be loaded.
|
|
|
|
The linker searches a standard list of directories for the library,
|
|
which is actually a file named @file{lib@var{library}.a}. The linker
|
|
then uses this file as if it had been specified precisely by name.
|
|
|
|
The directories searched include several standard system directories
|
|
plus any that you specify with @option{-L}.
|
|
|
|
Normally the files found this way are library files---archive files
|
|
whose members are object files. The linker handles an archive file by
|
|
scanning through it for members which define symbols that have so far
|
|
been referenced but not defined. But if the file that is found is an
|
|
ordinary object file, it is linked in the usual fashion. The only
|
|
difference between using an @option{-l} option and specifying a file name
|
|
is that @option{-l} surrounds @var{library} with @samp{lib} and @samp{.a}
|
|
and searches several directories.
|
|
|
|
@item -lobjc
|
|
@opindex lobjc
|
|
You need this special case of the @option{-l} option in order to
|
|
link an Objective-C program.
|
|
|
|
@item -nostartfiles
|
|
@opindex nostartfiles
|
|
Do not use the standard system startup files when linking.
|
|
The standard system libraries are used normally, unless @option{-nostdlib}
|
|
or @option{-nodefaultlibs} is used.
|
|
|
|
@item -nodefaultlibs
|
|
@opindex nodefaultlibs
|
|
Do not use the standard system libraries when linking.
|
|
Only the libraries you specify will be passed to the linker.
|
|
The standard startup files are used normally, unless @option{-nostartfiles}
|
|
is used. The compiler may generate calls to memcmp, memset, and memcpy
|
|
for System V (and ISO C) environments or to bcopy and bzero for
|
|
BSD environments. These entries are usually resolved by entries in
|
|
libc. These entry points should be supplied through some other
|
|
mechanism when this option is specified.
|
|
|
|
@item -nostdlib
|
|
@opindex nostdlib
|
|
Do not use the standard system startup files or libraries when linking.
|
|
No startup files and only the libraries you specify will be passed to
|
|
the linker. The compiler may generate calls to memcmp, memset, and memcpy
|
|
for System V (and ISO C) environments or to bcopy and bzero for
|
|
BSD environments. These entries are usually resolved by entries in
|
|
libc. These entry points should be supplied through some other
|
|
mechanism when this option is specified.
|
|
|
|
@cindex @option{-lgcc}, use with @option{-nostdlib}
|
|
@cindex @option{-nostdlib} and unresolved references
|
|
@cindex unresolved references and @option{-nostdlib}
|
|
@cindex @option{-lgcc}, use with @option{-nodefaultlibs}
|
|
@cindex @option{-nodefaultlibs} and unresolved references
|
|
@cindex unresolved references and @option{-nodefaultlibs}
|
|
One of the standard libraries bypassed by @option{-nostdlib} and
|
|
@option{-nodefaultlibs} is @file{libgcc.a}, a library of internal subroutines
|
|
that GCC uses to overcome shortcomings of particular machines, or special
|
|
needs for some languages.
|
|
(@xref{Interface,,Interfacing to GCC Output,gccint,GNU Compiler
|
|
Collection (GCC) Internals},
|
|
for more discussion of @file{libgcc.a}.)
|
|
In most cases, you need @file{libgcc.a} even when you want to avoid
|
|
other standard libraries. In other words, when you specify @option{-nostdlib}
|
|
or @option{-nodefaultlibs} you should usually specify @option{-lgcc} as well.
|
|
This ensures that you have no unresolved references to internal GCC
|
|
library subroutines. (For example, @samp{__main}, used to ensure C++
|
|
constructors will be called; @pxref{Collect2,,@code{collect2}, gccint,
|
|
GNU Compiler Collection (GCC) Internals}.)
|
|
|
|
@item -s
|
|
@opindex s
|
|
Remove all symbol table and relocation information from the executable.
|
|
|
|
@item -static
|
|
@opindex static
|
|
On systems that support dynamic linking, this prevents linking with the shared
|
|
libraries. On other systems, this option has no effect.
|
|
|
|
@item -shared
|
|
@opindex shared
|
|
Produce a shared object which can then be linked with other objects to
|
|
form an executable. Not all systems support this option. For predictable
|
|
results, you must also specify the same set of options that were used to
|
|
generate code (@option{-fpic}, @option{-fPIC}, or model suboptions)
|
|
when you specify this option.@footnote{On some systems, @samp{gcc -shared}
|
|
needs to build supplementary stub code for constructors to work. On
|
|
multi-libbed systems, @samp{gcc -shared} must select the correct support
|
|
libraries to link against. Failing to supply the correct flags may lead
|
|
to subtle defects. Supplying them in cases where they are not necessary
|
|
is innocuous.}
|
|
|
|
@item -shared-libgcc
|
|
@itemx -static-libgcc
|
|
@opindex shared-libgcc
|
|
@opindex static-libgcc
|
|
On systems that provide @file{libgcc} as a shared library, these options
|
|
force the use of either the shared or static version respectively.
|
|
If no shared version of @file{libgcc} was built when the compiler was
|
|
configured, these options have no effect.
|
|
|
|
There are several situations in which an application should use the
|
|
shared @file{libgcc} instead of the static version. The most common
|
|
of these is when the application wishes to throw and catch exceptions
|
|
across different shared libraries. In that case, each of the libraries
|
|
as well as the application itself should use the shared @file{libgcc}.
|
|
|
|
Therefore, whenever you specify the @option{-shared} option, the GCC
|
|
driver automatically adds @option{-shared-libgcc}, unless you explicitly
|
|
specify @option{-static-libgcc}. The G++ driver automatically adds
|
|
@option{-shared-libgcc} when you build a main executable as well because
|
|
for C++ programs that is typically the right thing to do.
|
|
(Exception-handling will not work reliably otherwise.)
|
|
|
|
However, when linking a main executable written in C, you must
|
|
explicitly say @option{-shared-libgcc} if you want to use the shared
|
|
@file{libgcc}.
|
|
|
|
@item -symbolic
|
|
@opindex symbolic
|
|
Bind references to global symbols when building a shared object. Warn
|
|
about any unresolved references (unless overridden by the link editor
|
|
option @samp{-Xlinker -z -Xlinker defs}). Only a few systems support
|
|
this option.
|
|
|
|
@item -Xlinker @var{option}
|
|
@opindex Xlinker
|
|
Pass @var{option} as an option to the linker. You can use this to
|
|
supply system-specific linker options which GCC does not know how to
|
|
recognize.
|
|
|
|
If you want to pass an option that takes an argument, you must use
|
|
@option{-Xlinker} twice, once for the option and once for the argument.
|
|
For example, to pass @option{-assert definitions}, you must write
|
|
@samp{-Xlinker -assert -Xlinker definitions}. It does not work to write
|
|
@option{-Xlinker "-assert definitions"}, because this passes the entire
|
|
string as a single argument, which is not what the linker expects.
|
|
|
|
@item -Wl,@var{option}
|
|
@opindex Wl
|
|
Pass @var{option} as an option to the linker. If @var{option} contains
|
|
commas, it is split into multiple options at the commas.
|
|
|
|
@item -u @var{symbol}
|
|
@opindex u
|
|
Pretend the symbol @var{symbol} is undefined, to force linking of
|
|
library modules to define it. You can use @option{-u} multiple times with
|
|
different symbols to force loading of additional library modules.
|
|
@end table
|
|
|
|
@node Directory Options
|
|
@section Options for Directory Search
|
|
@cindex directory options
|
|
@cindex options, directory search
|
|
@cindex search path
|
|
|
|
These options specify directories to search for header files, for
|
|
libraries and for parts of the compiler:
|
|
|
|
@table @gcctabopt
|
|
@item -I@var{dir}
|
|
@opindex I
|
|
Add the directory @var{dir} to the head of the list of directories to be
|
|
searched for header files. This can be used to override a system header
|
|
file, substituting your own version, since these directories are
|
|
searched before the system header file directories. However, you should
|
|
not use this option to add directories that contain vendor-supplied
|
|
system header files (use @option{-isystem} for that). If you use more than
|
|
one @option{-I} option, the directories are scanned in left-to-right
|
|
order; the standard system directories come after.
|
|
|
|
If a standard system include directory, or a directory specified with
|
|
@option{-isystem}, is also specified with @option{-I}, it will be
|
|
searched only in the position requested by @option{-I}. Also, it will
|
|
not be considered a system include directory. If that directory really
|
|
does contain system headers, there is a good chance that they will
|
|
break. For instance, if GCC's installation procedure edited the headers
|
|
in @file{/usr/include} to fix bugs, @samp{-I/usr/include} will cause the
|
|
original, buggy headers to be found instead of the corrected ones. GCC
|
|
will issue a warning when a system include directory is hidden in this
|
|
way.
|
|
|
|
@item -I-
|
|
@opindex I-
|
|
Any directories you specify with @option{-I} options before the @option{-I-}
|
|
option are searched only for the case of @samp{#include "@var{file}"};
|
|
they are not searched for @samp{#include <@var{file}>}.
|
|
|
|
If additional directories are specified with @option{-I} options after
|
|
the @option{-I-}, these directories are searched for all @samp{#include}
|
|
directives. (Ordinarily @emph{all} @option{-I} directories are used
|
|
this way.)
|
|
|
|
In addition, the @option{-I-} option inhibits the use of the current
|
|
directory (where the current input file came from) as the first search
|
|
directory for @samp{#include "@var{file}"}. There is no way to
|
|
override this effect of @option{-I-}. With @option{-I.} you can specify
|
|
searching the directory which was current when the compiler was
|
|
invoked. That is not exactly the same as what the preprocessor does
|
|
by default, but it is often satisfactory.
|
|
|
|
@option{-I-} does not inhibit the use of the standard system directories
|
|
for header files. Thus, @option{-I-} and @option{-nostdinc} are
|
|
independent.
|
|
|
|
@item -L@var{dir}
|
|
@opindex L
|
|
Add directory @var{dir} to the list of directories to be searched
|
|
for @option{-l}.
|
|
|
|
@item -B@var{prefix}
|
|
@opindex B
|
|
This option specifies where to find the executables, libraries,
|
|
include files, and data files of the compiler itself.
|
|
|
|
The compiler driver program runs one or more of the subprograms
|
|
@file{cpp}, @file{cc1}, @file{as} and @file{ld}. It tries
|
|
@var{prefix} as a prefix for each program it tries to run, both with and
|
|
without @samp{@var{machine}/@var{version}/} (@pxref{Target Options}).
|
|
|
|
For each subprogram to be run, the compiler driver first tries the
|
|
@option{-B} prefix, if any. If that name is not found, or if @option{-B}
|
|
was not specified, the driver tries two standard prefixes, which are
|
|
@file{/usr/lib/gcc/} and @file{/usr/local/lib/gcc-lib/}. If neither of
|
|
those results in a file name that is found, the unmodified program
|
|
name is searched for using the directories specified in your
|
|
@env{PATH} environment variable.
|
|
|
|
The compiler will check to see if the path provided by the @option{-B}
|
|
refers to a directory, and if necessary it will add a directory
|
|
separator character at the end of the path.
|
|
|
|
@option{-B} prefixes that effectively specify directory names also apply
|
|
to libraries in the linker, because the compiler translates these
|
|
options into @option{-L} options for the linker. They also apply to
|
|
includes files in the preprocessor, because the compiler translates these
|
|
options into @option{-isystem} options for the preprocessor. In this case,
|
|
the compiler appends @samp{include} to the prefix.
|
|
|
|
The run-time support file @file{libgcc.a} can also be searched for using
|
|
the @option{-B} prefix, if needed. If it is not found there, the two
|
|
standard prefixes above are tried, and that is all. The file is left
|
|
out of the link if it is not found by those means.
|
|
|
|
Another way to specify a prefix much like the @option{-B} prefix is to use
|
|
the environment variable @env{GCC_EXEC_PREFIX}. @xref{Environment
|
|
Variables}.
|
|
|
|
As a special kludge, if the path provided by @option{-B} is
|
|
@file{[dir/]stage@var{N}/}, where @var{N} is a number in the range 0 to
|
|
9, then it will be replaced by @file{[dir/]include}. This is to help
|
|
with boot-strapping the compiler.
|
|
|
|
@item -specs=@var{file}
|
|
@opindex specs
|
|
Process @var{file} after the compiler reads in the standard @file{specs}
|
|
file, in order to override the defaults that the @file{gcc} driver
|
|
program uses when determining what switches to pass to @file{cc1},
|
|
@file{cc1plus}, @file{as}, @file{ld}, etc. More than one
|
|
@option{-specs=@var{file}} can be specified on the command line, and they
|
|
are processed in order, from left to right.
|
|
@end table
|
|
|
|
@c man end
|
|
|
|
@node Spec Files
|
|
@section Specifying subprocesses and the switches to pass to them
|
|
@cindex Spec Files
|
|
@command{gcc} is a driver program. It performs its job by invoking a
|
|
sequence of other programs to do the work of compiling, assembling and
|
|
linking. GCC interprets its command-line parameters and uses these to
|
|
deduce which programs it should invoke, and which command-line options
|
|
it ought to place on their command lines. This behavior is controlled
|
|
by @dfn{spec strings}. In most cases there is one spec string for each
|
|
program that GCC can invoke, but a few programs have multiple spec
|
|
strings to control their behavior. The spec strings built into GCC can
|
|
be overridden by using the @option{-specs=} command-line switch to specify
|
|
a spec file.
|
|
|
|
@dfn{Spec files} are plaintext files that are used to construct spec
|
|
strings. They consist of a sequence of directives separated by blank
|
|
lines. The type of directive is determined by the first non-whitespace
|
|
character on the line and it can be one of the following:
|
|
|
|
@table @code
|
|
@item %@var{command}
|
|
Issues a @var{command} to the spec file processor. The commands that can
|
|
appear here are:
|
|
|
|
@table @code
|
|
@item %include <@var{file}>
|
|
@cindex %include
|
|
Search for @var{file} and insert its text at the current point in the
|
|
specs file.
|
|
|
|
@item %include_noerr <@var{file}>
|
|
@cindex %include_noerr
|
|
Just like @samp{%include}, but do not generate an error message if the include
|
|
file cannot be found.
|
|
|
|
@item %rename @var{old_name} @var{new_name}
|
|
@cindex %rename
|
|
Rename the spec string @var{old_name} to @var{new_name}.
|
|
|
|
@end table
|
|
|
|
@item *[@var{spec_name}]:
|
|
This tells the compiler to create, override or delete the named spec
|
|
string. All lines after this directive up to the next directive or
|
|
blank line are considered to be the text for the spec string. If this
|
|
results in an empty string then the spec will be deleted. (Or, if the
|
|
spec did not exist, then nothing will happened.) Otherwise, if the spec
|
|
does not currently exist a new spec will be created. If the spec does
|
|
exist then its contents will be overridden by the text of this
|
|
directive, unless the first character of that text is the @samp{+}
|
|
character, in which case the text will be appended to the spec.
|
|
|
|
@item [@var{suffix}]:
|
|
Creates a new @samp{[@var{suffix}] spec} pair. All lines after this directive
|
|
and up to the next directive or blank line are considered to make up the
|
|
spec string for the indicated suffix. When the compiler encounters an
|
|
input file with the named suffix, it will processes the spec string in
|
|
order to work out how to compile that file. For example:
|
|
|
|
@smallexample
|
|
.ZZ:
|
|
z-compile -input %i
|
|
@end smallexample
|
|
|
|
This says that any input file whose name ends in @samp{.ZZ} should be
|
|
passed to the program @samp{z-compile}, which should be invoked with the
|
|
command-line switch @option{-input} and with the result of performing the
|
|
@samp{%i} substitution. (See below.)
|
|
|
|
As an alternative to providing a spec string, the text that follows a
|
|
suffix directive can be one of the following:
|
|
|
|
@table @code
|
|
@item @@@var{language}
|
|
This says that the suffix is an alias for a known @var{language}. This is
|
|
similar to using the @option{-x} command-line switch to GCC to specify a
|
|
language explicitly. For example:
|
|
|
|
@smallexample
|
|
.ZZ:
|
|
@@c++
|
|
@end smallexample
|
|
|
|
Says that .ZZ files are, in fact, C++ source files.
|
|
|
|
@item #@var{name}
|
|
This causes an error messages saying:
|
|
|
|
@smallexample
|
|
@var{name} compiler not installed on this system.
|
|
@end smallexample
|
|
@end table
|
|
|
|
GCC already has an extensive list of suffixes built into it.
|
|
This directive will add an entry to the end of the list of suffixes, but
|
|
since the list is searched from the end backwards, it is effectively
|
|
possible to override earlier entries using this technique.
|
|
|
|
@end table
|
|
|
|
GCC has the following spec strings built into it. Spec files can
|
|
override these strings or create their own. Note that individual
|
|
targets can also add their own spec strings to this list.
|
|
|
|
@smallexample
|
|
asm Options to pass to the assembler
|
|
asm_final Options to pass to the assembler post-processor
|
|
cpp Options to pass to the C preprocessor
|
|
cc1 Options to pass to the C compiler
|
|
cc1plus Options to pass to the C++ compiler
|
|
endfile Object files to include at the end of the link
|
|
link Options to pass to the linker
|
|
lib Libraries to include on the command line to the linker
|
|
libgcc Decides which GCC support library to pass to the linker
|
|
linker Sets the name of the linker
|
|
predefines Defines to be passed to the C preprocessor
|
|
signed_char Defines to pass to CPP to say whether @code{char} is signed
|
|
by default
|
|
startfile Object files to include at the start of the link
|
|
@end smallexample
|
|
|
|
Here is a small example of a spec file:
|
|
|
|
@smallexample
|
|
%rename lib old_lib
|
|
|
|
*lib:
|
|
--start-group -lgcc -lc -leval1 --end-group %(old_lib)
|
|
@end smallexample
|
|
|
|
This example renames the spec called @samp{lib} to @samp{old_lib} and
|
|
then overrides the previous definition of @samp{lib} with a new one.
|
|
The new definition adds in some extra command-line options before
|
|
including the text of the old definition.
|
|
|
|
@dfn{Spec strings} are a list of command-line options to be passed to their
|
|
corresponding program. In addition, the spec strings can contain
|
|
@samp{%}-prefixed sequences to substitute variable text or to
|
|
conditionally insert text into the command line. Using these constructs
|
|
it is possible to generate quite complex command lines.
|
|
|
|
Here is a table of all defined @samp{%}-sequences for spec
|
|
strings. Note that spaces are not generated automatically around the
|
|
results of expanding these sequences. Therefore you can concatenate them
|
|
together or combine them with constant text in a single argument.
|
|
|
|
@table @code
|
|
@item %%
|
|
Substitute one @samp{%} into the program name or argument.
|
|
|
|
@item %i
|
|
Substitute the name of the input file being processed.
|
|
|
|
@item %b
|
|
Substitute the basename of the input file being processed.
|
|
This is the substring up to (and not including) the last period
|
|
and not including the directory.
|
|
|
|
@item %B
|
|
This is the same as @samp{%b}, but include the file suffix (text after
|
|
the last period).
|
|
|
|
@item %d
|
|
Marks the argument containing or following the @samp{%d} as a
|
|
temporary file name, so that that file will be deleted if GCC exits
|
|
successfully. Unlike @samp{%g}, this contributes no text to the
|
|
argument.
|
|
|
|
@item %g@var{suffix}
|
|
Substitute a file name that has suffix @var{suffix} and is chosen
|
|
once per compilation, and mark the argument in the same way as
|
|
@samp{%d}. To reduce exposure to denial-of-service attacks, the file
|
|
name is now chosen in a way that is hard to predict even when previously
|
|
chosen file names are known. For example, @samp{%g.s @dots{} %g.o @dots{} %g.s}
|
|
might turn into @samp{ccUVUUAU.s ccXYAXZ12.o ccUVUUAU.s}. @var{suffix} matches
|
|
the regexp @samp{[.A-Za-z]*} or the special string @samp{%O}, which is
|
|
treated exactly as if @samp{%O} had been preprocessed. Previously, @samp{%g}
|
|
was simply substituted with a file name chosen once per compilation,
|
|
without regard to any appended suffix (which was therefore treated
|
|
just like ordinary text), making such attacks more likely to succeed.
|
|
|
|
@item %u@var{suffix}
|
|
Like @samp{%g}, but generates a new temporary file name even if
|
|
@samp{%u@var{suffix}} was already seen.
|
|
|
|
@item %U@var{suffix}
|
|
Substitutes the last file name generated with @samp{%u@var{suffix}}, generating a
|
|
new one if there is no such last file name. In the absence of any
|
|
@samp{%u@var{suffix}}, this is just like @samp{%g@var{suffix}}, except they don't share
|
|
the same suffix @emph{space}, so @samp{%g.s @dots{} %U.s @dots{} %g.s @dots{} %U.s}
|
|
would involve the generation of two distinct file names, one
|
|
for each @samp{%g.s} and another for each @samp{%U.s}. Previously, @samp{%U} was
|
|
simply substituted with a file name chosen for the previous @samp{%u},
|
|
without regard to any appended suffix.
|
|
|
|
@item %j@var{SUFFIX}
|
|
Substitutes the name of the @code{HOST_BIT_BUCKET}, if any, and if it is
|
|
writable, and if save-temps is off; otherwise, substitute the name
|
|
of a temporary file, just like @samp{%u}. This temporary file is not
|
|
meant for communication between processes, but rather as a junk
|
|
disposal mechanism.
|
|
|
|
@item %.@var{SUFFIX}
|
|
Substitutes @var{.SUFFIX} for the suffixes of a matched switch's args
|
|
when it is subsequently output with @samp{%*}. @var{SUFFIX} is
|
|
terminated by the next space or %.
|
|
|
|
@item %w
|
|
Marks the argument containing or following the @samp{%w} as the
|
|
designated output file of this compilation. This puts the argument
|
|
into the sequence of arguments that @samp{%o} will substitute later.
|
|
|
|
@item %o
|
|
Substitutes the names of all the output files, with spaces
|
|
automatically placed around them. You should write spaces
|
|
around the @samp{%o} as well or the results are undefined.
|
|
@samp{%o} is for use in the specs for running the linker.
|
|
Input files whose names have no recognized suffix are not compiled
|
|
at all, but they are included among the output files, so they will
|
|
be linked.
|
|
|
|
@item %O
|
|
Substitutes the suffix for object files. Note that this is
|
|
handled specially when it immediately follows @samp{%g, %u, or %U},
|
|
because of the need for those to form complete file names. The
|
|
handling is such that @samp{%O} is treated exactly as if it had already
|
|
been substituted, except that @samp{%g, %u, and %U} do not currently
|
|
support additional @var{suffix} characters following @samp{%O} as they would
|
|
following, for example, @samp{.o}.
|
|
|
|
@item %p
|
|
Substitutes the standard macro predefinitions for the
|
|
current target machine. Use this when running @code{cpp}.
|
|
|
|
@item %P
|
|
Like @samp{%p}, but puts @samp{__} before and after the name of each
|
|
predefined macro, except for macros that start with @samp{__} or with
|
|
@samp{_@var{L}}, where @var{L} is an uppercase letter. This is for ISO
|
|
C@.
|
|
|
|
@item %I
|
|
Substitute a @option{-iprefix} option made from @env{GCC_EXEC_PREFIX}.
|
|
|
|
@item %s
|
|
Current argument is the name of a library or startup file of some sort.
|
|
Search for that file in a standard list of directories and substitute
|
|
the full name found.
|
|
|
|
@item %e@var{str}
|
|
Print @var{str} as an error message. @var{str} is terminated by a newline.
|
|
Use this when inconsistent options are detected.
|
|
|
|
@item %|
|
|
Output @samp{-} if the input for the current command is coming from a pipe.
|
|
|
|
@item %(@var{name})
|
|
Substitute the contents of spec string @var{name} at this point.
|
|
|
|
@item %[@var{name}]
|
|
Like @samp{%(@dots{})} but put @samp{__} around @option{-D} arguments.
|
|
|
|
@item %x@{@var{option}@}
|
|
Accumulate an option for @samp{%X}.
|
|
|
|
@item %X
|
|
Output the accumulated linker options specified by @option{-Wl} or a @samp{%x}
|
|
spec string.
|
|
|
|
@item %Y
|
|
Output the accumulated assembler options specified by @option{-Wa}.
|
|
|
|
@item %Z
|
|
Output the accumulated preprocessor options specified by @option{-Wp}.
|
|
|
|
@item %v1
|
|
Substitute the major version number of GCC@.
|
|
(For version 2.9.5, this is 2.)
|
|
|
|
@item %v2
|
|
Substitute the minor version number of GCC@.
|
|
(For version 2.9.5, this is 9.)
|
|
|
|
@item %v3
|
|
Substitute the patch level number of GCC@.
|
|
(For version 2.9.5, this is 5.)
|
|
|
|
@item %a
|
|
Process the @code{asm} spec. This is used to compute the
|
|
switches to be passed to the assembler.
|
|
|
|
@item %A
|
|
Process the @code{asm_final} spec. This is a spec string for
|
|
passing switches to an assembler post-processor, if such a program is
|
|
needed.
|
|
|
|
@item %l
|
|
Process the @code{link} spec. This is the spec for computing the
|
|
command line passed to the linker. Typically it will make use of the
|
|
@samp{%L %G %S %D and %E} sequences.
|
|
|
|
@item %D
|
|
Dump out a @option{-L} option for each directory that GCC believes might
|
|
contain startup files. If the target supports multilibs then the
|
|
current multilib directory will be prepended to each of these paths.
|
|
|
|
@item %M
|
|
Output the multilib directory with directory separators replaced with
|
|
@samp{_}. If multilib directories are not set, or the multilib directory is
|
|
@file{.} then this option emits nothing.
|
|
|
|
@item %L
|
|
Process the @code{lib} spec. This is a spec string for deciding which
|
|
libraries should be included on the command line to the linker.
|
|
|
|
@item %G
|
|
Process the @code{libgcc} spec. This is a spec string for deciding
|
|
which GCC support library should be included on the command line to the linker.
|
|
|
|
@item %S
|
|
Process the @code{startfile} spec. This is a spec for deciding which
|
|
object files should be the first ones passed to the linker. Typically
|
|
this might be a file named @file{crt0.o}.
|
|
|
|
@item %E
|
|
Process the @code{endfile} spec. This is a spec string that specifies
|
|
the last object files that will be passed to the linker.
|
|
|
|
@item %C
|
|
Process the @code{cpp} spec. This is used to construct the arguments
|
|
to be passed to the C preprocessor.
|
|
|
|
@item %c
|
|
Process the @code{signed_char} spec. This is intended to be used
|
|
to tell cpp whether a char is signed. It typically has the definition:
|
|
@smallexample
|
|
%@{funsigned-char:-D__CHAR_UNSIGNED__@}
|
|
@end smallexample
|
|
|
|
@item %1
|
|
Process the @code{cc1} spec. This is used to construct the options to be
|
|
passed to the actual C compiler (@samp{cc1}).
|
|
|
|
@item %2
|
|
Process the @code{cc1plus} spec. This is used to construct the options to be
|
|
passed to the actual C++ compiler (@samp{cc1plus}).
|
|
|
|
@item %*
|
|
Substitute the variable part of a matched option. See below.
|
|
Note that each comma in the substituted string is replaced by
|
|
a single space.
|
|
|
|
@item %@{@code{S}@}
|
|
Substitutes the @code{-S} switch, if that switch was given to GCC@.
|
|
If that switch was not specified, this substitutes nothing. Note that
|
|
the leading dash is omitted when specifying this option, and it is
|
|
automatically inserted if the substitution is performed. Thus the spec
|
|
string @samp{%@{foo@}} would match the command-line option @option{-foo}
|
|
and would output the command line option @option{-foo}.
|
|
|
|
@item %W@{@code{S}@}
|
|
Like %@{@code{S}@} but mark last argument supplied within as a file to be
|
|
deleted on failure.
|
|
|
|
@item %@{@code{S}*@}
|
|
Substitutes all the switches specified to GCC whose names start
|
|
with @code{-S}, but which also take an argument. This is used for
|
|
switches like @option{-o}, @option{-D}, @option{-I}, etc.
|
|
GCC considers @option{-o foo} as being
|
|
one switch whose names starts with @samp{o}. %@{o*@} would substitute this
|
|
text, including the space. Thus two arguments would be generated.
|
|
|
|
@item %@{^@code{S}*@}
|
|
Like %@{@code{S}*@}, but don't put a blank between a switch and its
|
|
argument. Thus %@{^o*@} would only generate one argument, not two.
|
|
|
|
@item %@{@code{S}*&@code{T}*@}
|
|
Like %@{@code{S}*@}, but preserve order of @code{S} and @code{T} options
|
|
(the order of @code{S} and @code{T} in the spec is not significant).
|
|
There can be any number of ampersand-separated variables; for each the
|
|
wild card is optional. Useful for CPP as @samp{%@{D*&U*&A*@}}.
|
|
|
|
@item %@{<@code{S}@}
|
|
Remove all occurrences of @code{-S} from the command line. Note---this
|
|
command is position dependent. @samp{%} commands in the spec string
|
|
before this option will see @code{-S}, @samp{%} commands in the spec
|
|
string after this option will not.
|
|
|
|
@item %@{@code{S}*:@code{X}@}
|
|
Substitutes @code{X} if one or more switches whose names start with
|
|
@code{-S} are specified to GCC@. Note that the tail part of the
|
|
@code{-S} option (i.e.@: the part matched by the @samp{*}) will be substituted
|
|
for each occurrence of @samp{%*} within @code{X}.
|
|
|
|
@item %@{@code{S}:@code{X}@}
|
|
Substitutes @code{X}, but only if the @samp{-S} switch was given to GCC@.
|
|
|
|
@item %@{!@code{S}:@code{X}@}
|
|
Substitutes @code{X}, but only if the @samp{-S} switch was @emph{not} given to GCC@.
|
|
|
|
@item %@{|@code{S}:@code{X}@}
|
|
Like %@{@code{S}:@code{X}@}, but if no @code{S} switch, substitute @samp{-}.
|
|
|
|
@item %@{|!@code{S}:@code{X}@}
|
|
Like %@{!@code{S}:@code{X}@}, but if there is an @code{S} switch, substitute @samp{-}.
|
|
|
|
@item %@{.@code{S}:@code{X}@}
|
|
Substitutes @code{X}, but only if processing a file with suffix @code{S}.
|
|
|
|
@item %@{!.@code{S}:@code{X}@}
|
|
Substitutes @code{X}, but only if @emph{not} processing a file with suffix @code{S}.
|
|
|
|
@item %@{@code{S}|@code{P}:@code{X}@}
|
|
Substitutes @code{X} if either @code{-S} or @code{-P} was given to GCC@. This may be
|
|
combined with @samp{!} and @samp{.} sequences as well, although they
|
|
have a stronger binding than the @samp{|}. For example a spec string
|
|
like this:
|
|
|
|
@smallexample
|
|
%@{.c:-foo@} %@{!.c:-bar@} %@{.c|d:-baz@} %@{!.c|d:-boggle@}
|
|
@end smallexample
|
|
|
|
will output the following command-line options from the following input
|
|
command-line options:
|
|
|
|
@smallexample
|
|
fred.c -foo -baz
|
|
jim.d -bar -boggle
|
|
-d fred.c -foo -baz -boggle
|
|
-d jim.d -bar -baz -boggle
|
|
@end smallexample
|
|
|
|
@end table
|
|
|
|
The conditional text @code{X} in a %@{@code{S}:@code{X}@} or
|
|
%@{!@code{S}:@code{X}@} construct may contain other nested @samp{%} constructs
|
|
or spaces, or even newlines. They are processed as usual, as described
|
|
above.
|
|
|
|
The @option{-O}, @option{-f}, @option{-m}, and @option{-W}
|
|
switches are handled specifically in these
|
|
constructs. If another value of @option{-O} or the negated form of a @option{-f}, @option{-m}, or
|
|
@option{-W} switch is found later in the command line, the earlier switch
|
|
value is ignored, except with @{@code{S}*@} where @code{S} is just one
|
|
letter, which passes all matching options.
|
|
|
|
The character @samp{|} at the beginning of the predicate text is used to indicate
|
|
that a command should be piped to the following command, but only if @option{-pipe}
|
|
is specified.
|
|
|
|
It is built into GCC which switches take arguments and which do not.
|
|
(You might think it would be useful to generalize this to allow each
|
|
compiler's spec to say which switches take arguments. But this cannot
|
|
be done in a consistent fashion. GCC cannot even decide which input
|
|
files have been specified without knowing which switches take arguments,
|
|
and it must know which input files to compile in order to tell which
|
|
compilers to run).
|
|
|
|
GCC also knows implicitly that arguments starting in @option{-l} are to be
|
|
treated as compiler output files, and passed to the linker in their
|
|
proper position among the other output files.
|
|
|
|
@c man begin OPTIONS
|
|
|
|
@node Target Options
|
|
@section Specifying Target Machine and Compiler Version
|
|
@cindex target options
|
|
@cindex cross compiling
|
|
@cindex specifying machine version
|
|
@cindex specifying compiler version and target machine
|
|
@cindex compiler version, specifying
|
|
@cindex target machine, specifying
|
|
|
|
By default, GCC compiles code for the same type of machine that you
|
|
are using. However, it can also be installed as a cross-compiler, to
|
|
compile for some other type of machine. In fact, several different
|
|
configurations of GCC, for different target machines, can be
|
|
installed side by side. Then you specify which one to use with the
|
|
@option{-b} option.
|
|
|
|
In addition, older and newer versions of GCC can be installed side
|
|
by side. One of them (probably the newest) will be the default, but
|
|
you may sometimes wish to use another.
|
|
|
|
@table @gcctabopt
|
|
@item -b @var{machine}
|
|
@opindex b
|
|
The argument @var{machine} specifies the target machine for compilation.
|
|
This is useful when you have installed GCC as a cross-compiler.
|
|
|
|
The value to use for @var{machine} is the same as was specified as the
|
|
machine type when configuring GCC as a cross-compiler. For
|
|
example, if a cross-compiler was configured with @samp{configure
|
|
i386v}, meaning to compile for an 80386 running System V, then you
|
|
would specify @option{-b i386v} to run that cross compiler.
|
|
|
|
When you do not specify @option{-b}, it normally means to compile for
|
|
the same type of machine that you are using.
|
|
|
|
@item -V @var{version}
|
|
@opindex V
|
|
The argument @var{version} specifies which version of GCC to run.
|
|
This is useful when multiple versions are installed. For example,
|
|
@var{version} might be @samp{2.0}, meaning to run GCC version 2.0.
|
|
|
|
The default version, when you do not specify @option{-V}, is the last
|
|
version of GCC that you installed.
|
|
@end table
|
|
|
|
The @option{-b} and @option{-V} options actually work by controlling part of
|
|
the file name used for the executable files and libraries used for
|
|
compilation. A given version of GCC, for a given target machine, is
|
|
normally kept in the directory @file{/usr/local/lib/gcc-lib/@var{machine}/@var{version}}.
|
|
|
|
Thus, sites can customize the effect of @option{-b} or @option{-V} either by
|
|
changing the names of these directories or adding alternate names (or
|
|
symbolic links). If in directory @file{/usr/local/lib/gcc-lib/} the
|
|
file @file{80386} is a link to the file @file{i386v}, then @option{-b
|
|
80386} becomes an alias for @option{-b i386v}.
|
|
|
|
In one respect, the @option{-b} or @option{-V} do not completely change
|
|
to a different compiler: the top-level driver program @command{gcc}
|
|
that you originally invoked continues to run and invoke the other
|
|
executables (preprocessor, compiler per se, assembler and linker)
|
|
that do the real work. However, since no real work is done in the
|
|
driver program, it usually does not matter that the driver program
|
|
in use is not the one for the specified target. It is common for the
|
|
interface to the other executables to change incompatibly between
|
|
compiler versions, so unless the version specified is very close to that
|
|
of the driver (for example, @option{-V 3.0} with a driver program from GCC
|
|
version 3.0.1), use of @option{-V} may not work; for example, using
|
|
@option{-V 2.95.2} will not work with a driver program from GCC 3.0.
|
|
|
|
The only way that the driver program depends on the target machine is
|
|
in the parsing and handling of special machine-specific options.
|
|
However, this is controlled by a file which is found, along with the
|
|
other executables, in the directory for the specified version and
|
|
target machine. As a result, a single installed driver program adapts
|
|
to any specified target machine, and sufficiently similar compiler
|
|
versions.
|
|
|
|
The driver program executable does control one significant thing,
|
|
however: the default version and target machine. Therefore, you can
|
|
install different instances of the driver program, compiled for
|
|
different targets or versions, under different names.
|
|
|
|
For example, if the driver for version 2.0 is installed as @command{ogcc}
|
|
and that for version 2.1 is installed as @command{gcc}, then the command
|
|
@command{gcc} will use version 2.1 by default, while @command{ogcc} will use
|
|
2.0 by default. However, you can choose either version with either
|
|
command with the @option{-V} option.
|
|
|
|
@node Submodel Options
|
|
@section Hardware Models and Configurations
|
|
@cindex submodel options
|
|
@cindex specifying hardware config
|
|
@cindex hardware models and configurations, specifying
|
|
@cindex machine dependent options
|
|
|
|
Earlier we discussed the standard option @option{-b} which chooses among
|
|
different installed compilers for completely different target
|
|
machines, such as VAX vs.@: 68000 vs.@: 80386.
|
|
|
|
In addition, each of these target machine types can have its own
|
|
special options, starting with @samp{-m}, to choose among various
|
|
hardware models or configurations---for example, 68010 vs 68020,
|
|
floating coprocessor or none. A single installed version of the
|
|
compiler can compile for any model or configuration, according to the
|
|
options specified.
|
|
|
|
Some configurations of the compiler also support additional special
|
|
options, usually for compatibility with other compilers on the same
|
|
platform.
|
|
|
|
These options are defined by the macro @code{TARGET_SWITCHES} in the
|
|
machine description. The default for the options is also defined by
|
|
that macro, which enables you to change the defaults.
|
|
|
|
@menu
|
|
* M680x0 Options::
|
|
* M68hc1x Options::
|
|
* VAX Options::
|
|
* SPARC Options::
|
|
* Convex Options::
|
|
* AMD29K Options::
|
|
* ARM Options::
|
|
* MN10200 Options::
|
|
* MN10300 Options::
|
|
* M32R/D Options::
|
|
* M88K Options::
|
|
* RS/6000 and PowerPC Options::
|
|
* RT Options::
|
|
* MIPS Options::
|
|
* i386 and x86-64 Options::
|
|
* HPPA Options::
|
|
* Intel 960 Options::
|
|
* DEC Alpha Options::
|
|
* DEC Alpha/VMS Options::
|
|
* Clipper Options::
|
|
* H8/300 Options::
|
|
* SH Options::
|
|
* System V Options::
|
|
* TMS320C3x/C4x Options::
|
|
* V850 Options::
|
|
* ARC Options::
|
|
* NS32K Options::
|
|
* AVR Options::
|
|
* MCore Options::
|
|
* IA-64 Options::
|
|
* D30V Options::
|
|
* S/390 and zSeries Options::
|
|
* CRIS Options::
|
|
* MMIX Options::
|
|
* PDP-11 Options::
|
|
* Xstormy16 Options::
|
|
* Xtensa Options::
|
|
@end menu
|
|
|
|
@node M680x0 Options
|
|
@subsection M680x0 Options
|
|
@cindex M680x0 options
|
|
|
|
These are the @samp{-m} options defined for the 68000 series. The default
|
|
values for these options depends on which style of 68000 was selected when
|
|
the compiler was configured; the defaults for the most common choices are
|
|
given below.
|
|
|
|
@table @gcctabopt
|
|
@item -m68000
|
|
@itemx -mc68000
|
|
@opindex m68000
|
|
@opindex mc68000
|
|
Generate output for a 68000. This is the default
|
|
when the compiler is configured for 68000-based systems.
|
|
|
|
Use this option for microcontrollers with a 68000 or EC000 core,
|
|
including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356.
|
|
|
|
@item -m68020
|
|
@itemx -mc68020
|
|
@opindex m68020
|
|
@opindex mc68020
|
|
Generate output for a 68020. This is the default
|
|
when the compiler is configured for 68020-based systems.
|
|
|
|
@item -m68881
|
|
@opindex m68881
|
|
Generate output containing 68881 instructions for floating point.
|
|
This is the default for most 68020 systems unless @option{--nfp} was
|
|
specified when the compiler was configured.
|
|
|
|
@item -m68030
|
|
@opindex m68030
|
|
Generate output for a 68030. This is the default when the compiler is
|
|
configured for 68030-based systems.
|
|
|
|
@item -m68040
|
|
@opindex m68040
|
|
Generate output for a 68040. This is the default when the compiler is
|
|
configured for 68040-based systems.
|
|
|
|
This option inhibits the use of 68881/68882 instructions that have to be
|
|
emulated by software on the 68040. Use this option if your 68040 does not
|
|
have code to emulate those instructions.
|
|
|
|
@item -m68060
|
|
@opindex m68060
|
|
Generate output for a 68060. This is the default when the compiler is
|
|
configured for 68060-based systems.
|
|
|
|
This option inhibits the use of 68020 and 68881/68882 instructions that
|
|
have to be emulated by software on the 68060. Use this option if your 68060
|
|
does not have code to emulate those instructions.
|
|
|
|
@item -mcpu32
|
|
@opindex mcpu32
|
|
Generate output for a CPU32. This is the default
|
|
when the compiler is configured for CPU32-based systems.
|
|
|
|
Use this option for microcontrollers with a
|
|
CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334,
|
|
68336, 68340, 68341, 68349 and 68360.
|
|
|
|
@item -m5200
|
|
@opindex m5200
|
|
Generate output for a 520X ``coldfire'' family cpu. This is the default
|
|
when the compiler is configured for 520X-based systems.
|
|
|
|
Use this option for microcontroller with a 5200 core, including
|
|
the MCF5202, MCF5203, MCF5204 and MCF5202.
|
|
|
|
|
|
@item -m68020-40
|
|
@opindex m68020-40
|
|
Generate output for a 68040, without using any of the new instructions.
|
|
This results in code which can run relatively efficiently on either a
|
|
68020/68881 or a 68030 or a 68040. The generated code does use the
|
|
68881 instructions that are emulated on the 68040.
|
|
|
|
@item -m68020-60
|
|
@opindex m68020-60
|
|
Generate output for a 68060, without using any of the new instructions.
|
|
This results in code which can run relatively efficiently on either a
|
|
68020/68881 or a 68030 or a 68040. The generated code does use the
|
|
68881 instructions that are emulated on the 68060.
|
|
|
|
@item -mfpa
|
|
@opindex mfpa
|
|
Generate output containing Sun FPA instructions for floating point.
|
|
|
|
@item -msoft-float
|
|
@opindex msoft-float
|
|
Generate output containing library calls for floating point.
|
|
@strong{Warning:} the requisite libraries are not available for all m68k
|
|
targets. Normally the facilities of the machine's usual C compiler are
|
|
used, but this can't be done directly in cross-compilation. You must
|
|
make your own arrangements to provide suitable library functions for
|
|
cross-compilation. The embedded targets @samp{m68k-*-aout} and
|
|
@samp{m68k-*-coff} do provide software floating point support.
|
|
|
|
@item -mshort
|
|
@opindex mshort
|
|
Consider type @code{int} to be 16 bits wide, like @code{short int}.
|
|
|
|
@item -mnobitfield
|
|
@opindex mnobitfield
|
|
Do not use the bit-field instructions. The @option{-m68000}, @option{-mcpu32}
|
|
and @option{-m5200} options imply @w{@option{-mnobitfield}}.
|
|
|
|
@item -mbitfield
|
|
@opindex mbitfield
|
|
Do use the bit-field instructions. The @option{-m68020} option implies
|
|
@option{-mbitfield}. This is the default if you use a configuration
|
|
designed for a 68020.
|
|
|
|
@item -mrtd
|
|
@opindex mrtd
|
|
Use a different function-calling convention, in which functions
|
|
that take a fixed number of arguments return with the @code{rtd}
|
|
instruction, which pops their arguments while returning. This
|
|
saves one instruction in the caller since there is no need to pop
|
|
the arguments there.
|
|
|
|
This calling convention is incompatible with the one normally
|
|
used on Unix, so you cannot use it if you need to call libraries
|
|
compiled with the Unix compiler.
|
|
|
|
Also, you must provide function prototypes for all functions that
|
|
take variable numbers of arguments (including @code{printf});
|
|
otherwise incorrect code will be generated for calls to those
|
|
functions.
|
|
|
|
In addition, seriously incorrect code will result if you call a
|
|
function with too many arguments. (Normally, extra arguments are
|
|
harmlessly ignored.)
|
|
|
|
The @code{rtd} instruction is supported by the 68010, 68020, 68030,
|
|
68040, 68060 and CPU32 processors, but not by the 68000 or 5200.
|
|
|
|
@item -malign-int
|
|
@itemx -mno-align-int
|
|
@opindex malign-int
|
|
@opindex mno-align-int
|
|
Control whether GCC aligns @code{int}, @code{long}, @code{long long},
|
|
@code{float}, @code{double}, and @code{long double} variables on a 32-bit
|
|
boundary (@option{-malign-int}) or a 16-bit boundary (@option{-mno-align-int}).
|
|
Aligning variables on 32-bit boundaries produces code that runs somewhat
|
|
faster on processors with 32-bit busses at the expense of more memory.
|
|
|
|
@strong{Warning:} if you use the @option{-malign-int} switch, GCC will
|
|
align structures containing the above types differently than
|
|
most published application binary interface specifications for the m68k.
|
|
|
|
@item -mpcrel
|
|
@opindex mpcrel
|
|
Use the pc-relative addressing mode of the 68000 directly, instead of
|
|
using a global offset table. At present, this option implies @option{-fpic},
|
|
allowing at most a 16-bit offset for pc-relative addressing. @option{-fPIC} is
|
|
not presently supported with @option{-mpcrel}, though this could be supported for
|
|
68020 and higher processors.
|
|
|
|
@item -mno-strict-align
|
|
@itemx -mstrict-align
|
|
@opindex mno-strict-align
|
|
@opindex mstrict-align
|
|
Do not (do) assume that unaligned memory references will be handled by
|
|
the system.
|
|
|
|
@end table
|
|
|
|
@node M68hc1x Options
|
|
@subsection M68hc1x Options
|
|
@cindex M68hc1x options
|
|
|
|
These are the @samp{-m} options defined for the 68hc11 and 68hc12
|
|
microcontrollers. The default values for these options depends on
|
|
which style of microcontroller was selected when the compiler was configured;
|
|
the defaults for the most common choices are given below.
|
|
|
|
@table @gcctabopt
|
|
@item -m6811
|
|
@itemx -m68hc11
|
|
@opindex m6811
|
|
@opindex m68hc11
|
|
Generate output for a 68HC11. This is the default
|
|
when the compiler is configured for 68HC11-based systems.
|
|
|
|
@item -m6812
|
|
@itemx -m68hc12
|
|
@opindex m6812
|
|
@opindex m68hc12
|
|
Generate output for a 68HC12. This is the default
|
|
when the compiler is configured for 68HC12-based systems.
|
|
|
|
@item -mauto-incdec
|
|
@opindex mauto-incdec
|
|
Enable the use of 68HC12 pre and post auto-increment and auto-decrement
|
|
addressing modes.
|
|
|
|
@item -mshort
|
|
@opindex mshort
|
|
Consider type @code{int} to be 16 bits wide, like @code{short int}.
|
|
|
|
@item -msoft-reg-count=@var{count}
|
|
@opindex msoft-reg-count
|
|
Specify the number of pseudo-soft registers which are used for the
|
|
code generation. The maximum number is 32. Using more pseudo-soft
|
|
register may or may not result in better code depending on the program.
|
|
The default is 4 for 68HC11 and 2 for 68HC12.
|
|
|
|
@end table
|
|
|
|
@node VAX Options
|
|
@subsection VAX Options
|
|
@cindex VAX options
|
|
|
|
These @samp{-m} options are defined for the VAX:
|
|
|
|
@table @gcctabopt
|
|
@item -munix
|
|
@opindex munix
|
|
Do not output certain jump instructions (@code{aobleq} and so on)
|
|
that the Unix assembler for the VAX cannot handle across long
|
|
ranges.
|
|
|
|
@item -mgnu
|
|
@opindex mgnu
|
|
Do output those jump instructions, on the assumption that you
|
|
will assemble with the GNU assembler.
|
|
|
|
@item -mg
|
|
@opindex mg
|
|
Output code for g-format floating point numbers instead of d-format.
|
|
@end table
|
|
|
|
@node SPARC Options
|
|
@subsection SPARC Options
|
|
@cindex SPARC options
|
|
|
|
These @samp{-m} switches are supported on the SPARC:
|
|
|
|
@table @gcctabopt
|
|
@item -mno-app-regs
|
|
@itemx -mapp-regs
|
|
@opindex mno-app-regs
|
|
@opindex mapp-regs
|
|
Specify @option{-mapp-regs} to generate output using the global registers
|
|
2 through 4, which the SPARC SVR4 ABI reserves for applications. This
|
|
is the default.
|
|
|
|
To be fully SVR4 ABI compliant at the cost of some performance loss,
|
|
specify @option{-mno-app-regs}. You should compile libraries and system
|
|
software with this option.
|
|
|
|
@item -mfpu
|
|
@itemx -mhard-float
|
|
@opindex mfpu
|
|
@opindex mhard-float
|
|
Generate output containing floating point instructions. This is the
|
|
default.
|
|
|
|
@item -mno-fpu
|
|
@itemx -msoft-float
|
|
@opindex mno-fpu
|
|
@opindex msoft-float
|
|
Generate output containing library calls for floating point.
|
|
@strong{Warning:} the requisite libraries are not available for all SPARC
|
|
targets. Normally the facilities of the machine's usual C compiler are
|
|
used, but this cannot be done directly in cross-compilation. You must make
|
|
your own arrangements to provide suitable library functions for
|
|
cross-compilation. The embedded targets @samp{sparc-*-aout} and
|
|
@samp{sparclite-*-*} do provide software floating point support.
|
|
|
|
@option{-msoft-float} changes the calling convention in the output file;
|
|
therefore, it is only useful if you compile @emph{all} of a program with
|
|
this option. In particular, you need to compile @file{libgcc.a}, the
|
|
library that comes with GCC, with @option{-msoft-float} in order for
|
|
this to work.
|
|
|
|
@item -mhard-quad-float
|
|
@opindex mhard-quad-float
|
|
Generate output containing quad-word (long double) floating point
|
|
instructions.
|
|
|
|
@item -msoft-quad-float
|
|
@opindex msoft-quad-float
|
|
Generate output containing library calls for quad-word (long double)
|
|
floating point instructions. The functions called are those specified
|
|
in the SPARC ABI@. This is the default.
|
|
|
|
As of this writing, there are no sparc implementations that have hardware
|
|
support for the quad-word floating point instructions. They all invoke
|
|
a trap handler for one of these instructions, and then the trap handler
|
|
emulates the effect of the instruction. Because of the trap handler overhead,
|
|
this is much slower than calling the ABI library routines. Thus the
|
|
@option{-msoft-quad-float} option is the default.
|
|
|
|
@item -mno-epilogue
|
|
@itemx -mepilogue
|
|
@opindex mno-epilogue
|
|
@opindex mepilogue
|
|
With @option{-mepilogue} (the default), the compiler always emits code for
|
|
function exit at the end of each function. Any function exit in
|
|
the middle of the function (such as a return statement in C) will
|
|
generate a jump to the exit code at the end of the function.
|
|
|
|
With @option{-mno-epilogue}, the compiler tries to emit exit code inline
|
|
at every function exit.
|
|
|
|
@item -mno-flat
|
|
@itemx -mflat
|
|
@opindex mno-flat
|
|
@opindex mflat
|
|
With @option{-mflat}, the compiler does not generate save/restore instructions
|
|
and will use a ``flat'' or single register window calling convention.
|
|
This model uses %i7 as the frame pointer and is compatible with the normal
|
|
register window model. Code from either may be intermixed.
|
|
The local registers and the input registers (0--5) are still treated as
|
|
``call saved'' registers and will be saved on the stack as necessary.
|
|
|
|
With @option{-mno-flat} (the default), the compiler emits save/restore
|
|
instructions (except for leaf functions) and is the normal mode of operation.
|
|
|
|
@item -mno-unaligned-doubles
|
|
@itemx -munaligned-doubles
|
|
@opindex mno-unaligned-doubles
|
|
@opindex munaligned-doubles
|
|
Assume that doubles have 8 byte alignment. This is the default.
|
|
|
|
With @option{-munaligned-doubles}, GCC assumes that doubles have 8 byte
|
|
alignment only if they are contained in another type, or if they have an
|
|
absolute address. Otherwise, it assumes they have 4 byte alignment.
|
|
Specifying this option avoids some rare compatibility problems with code
|
|
generated by other compilers. It is not the default because it results
|
|
in a performance loss, especially for floating point code.
|
|
|
|
@item -mno-faster-structs
|
|
@itemx -mfaster-structs
|
|
@opindex mno-faster-structs
|
|
@opindex mfaster-structs
|
|
With @option{-mfaster-structs}, the compiler assumes that structures
|
|
should have 8 byte alignment. This enables the use of pairs of
|
|
@code{ldd} and @code{std} instructions for copies in structure
|
|
assignment, in place of twice as many @code{ld} and @code{st} pairs.
|
|
However, the use of this changed alignment directly violates the Sparc
|
|
ABI@. Thus, it's intended only for use on targets where the developer
|
|
acknowledges that their resulting code will not be directly in line with
|
|
the rules of the ABI@.
|
|
|
|
@item -mv8
|
|
@itemx -msparclite
|
|
@opindex mv8
|
|
@opindex msparclite
|
|
These two options select variations on the SPARC architecture.
|
|
|
|
By default (unless specifically configured for the Fujitsu SPARClite),
|
|
GCC generates code for the v7 variant of the SPARC architecture.
|
|
|
|
@option{-mv8} will give you SPARC v8 code. The only difference from v7
|
|
code is that the compiler emits the integer multiply and integer
|
|
divide instructions which exist in SPARC v8 but not in SPARC v7.
|
|
|
|
@option{-msparclite} will give you SPARClite code. This adds the integer
|
|
multiply, integer divide step and scan (@code{ffs}) instructions which
|
|
exist in SPARClite but not in SPARC v7.
|
|
|
|
These options are deprecated and will be deleted in a future GCC release.
|
|
They have been replaced with @option{-mcpu=xxx}.
|
|
|
|
@item -mcypress
|
|
@itemx -msupersparc
|
|
@opindex mcypress
|
|
@opindex msupersparc
|
|
These two options select the processor for which the code is optimized.
|
|
|
|
With @option{-mcypress} (the default), the compiler optimizes code for the
|
|
Cypress CY7C602 chip, as used in the SparcStation/SparcServer 3xx series.
|
|
This is also appropriate for the older SparcStation 1, 2, IPX etc.
|
|
|
|
With @option{-msupersparc} the compiler optimizes code for the SuperSparc cpu, as
|
|
used in the SparcStation 10, 1000 and 2000 series. This flag also enables use
|
|
of the full SPARC v8 instruction set.
|
|
|
|
These options are deprecated and will be deleted in a future GCC release.
|
|
They have been replaced with @option{-mcpu=xxx}.
|
|
|
|
@item -mcpu=@var{cpu_type}
|
|
@opindex mcpu
|
|
Set the instruction set, register set, and instruction scheduling parameters
|
|
for machine type @var{cpu_type}. Supported values for @var{cpu_type} are
|
|
@samp{v7}, @samp{cypress}, @samp{v8}, @samp{supersparc}, @samp{sparclite},
|
|
@samp{hypersparc}, @samp{sparclite86x}, @samp{f930}, @samp{f934},
|
|
@samp{sparclet}, @samp{tsc701}, @samp{v9}, and @samp{ultrasparc}.
|
|
|
|
Default instruction scheduling parameters are used for values that select
|
|
an architecture and not an implementation. These are @samp{v7}, @samp{v8},
|
|
@samp{sparclite}, @samp{sparclet}, @samp{v9}.
|
|
|
|
Here is a list of each supported architecture and their supported
|
|
implementations.
|
|
|
|
@smallexample
|
|
v7: cypress
|
|
v8: supersparc, hypersparc
|
|
sparclite: f930, f934, sparclite86x
|
|
sparclet: tsc701
|
|
v9: ultrasparc
|
|
@end smallexample
|
|
|
|
@item -mtune=@var{cpu_type}
|
|
@opindex mtune
|
|
Set the instruction scheduling parameters for machine type
|
|
@var{cpu_type}, but do not set the instruction set or register set that the
|
|
option @option{-mcpu=@var{cpu_type}} would.
|
|
|
|
The same values for @option{-mcpu=@var{cpu_type}} can be used for
|
|
@option{-mtune=@var{cpu_type}}, but the only useful values are those
|
|
that select a particular cpu implementation. Those are @samp{cypress},
|
|
@samp{supersparc}, @samp{hypersparc}, @samp{f930}, @samp{f934},
|
|
@samp{sparclite86x}, @samp{tsc701}, and @samp{ultrasparc}.
|
|
|
|
@end table
|
|
|
|
These @samp{-m} switches are supported in addition to the above
|
|
on the SPARCLET processor.
|
|
|
|
@table @gcctabopt
|
|
@item -mlittle-endian
|
|
@opindex mlittle-endian
|
|
Generate code for a processor running in little-endian mode.
|
|
|
|
@item -mlive-g0
|
|
@opindex mlive-g0
|
|
Treat register @code{%g0} as a normal register.
|
|
GCC will continue to clobber it as necessary but will not assume
|
|
it always reads as 0.
|
|
|
|
@item -mbroken-saverestore
|
|
@opindex mbroken-saverestore
|
|
Generate code that does not use non-trivial forms of the @code{save} and
|
|
@code{restore} instructions. Early versions of the SPARCLET processor do
|
|
not correctly handle @code{save} and @code{restore} instructions used with
|
|
arguments. They correctly handle them used without arguments. A @code{save}
|
|
instruction used without arguments increments the current window pointer
|
|
but does not allocate a new stack frame. It is assumed that the window
|
|
overflow trap handler will properly handle this case as will interrupt
|
|
handlers.
|
|
@end table
|
|
|
|
These @samp{-m} switches are supported in addition to the above
|
|
on SPARC V9 processors in 64-bit environments.
|
|
|
|
@table @gcctabopt
|
|
@item -mlittle-endian
|
|
@opindex mlittle-endian
|
|
Generate code for a processor running in little-endian mode.
|
|
|
|
@item -m32
|
|
@itemx -m64
|
|
@opindex m32
|
|
@opindex m64
|
|
Generate code for a 32-bit or 64-bit environment.
|
|
The 32-bit environment sets int, long and pointer to 32 bits.
|
|
The 64-bit environment sets int to 32 bits and long and pointer
|
|
to 64 bits.
|
|
|
|
@item -mcmodel=medlow
|
|
@opindex mcmodel=medlow
|
|
Generate code for the Medium/Low code model: the program must be linked
|
|
in the low 32 bits of the address space. Pointers are 64 bits.
|
|
Programs can be statically or dynamically linked.
|
|
|
|
@item -mcmodel=medmid
|
|
@opindex mcmodel=medmid
|
|
Generate code for the Medium/Middle code model: the program must be linked
|
|
in the low 44 bits of the address space, the text segment must be less than
|
|
2G bytes, and data segment must be within 2G of the text segment.
|
|
Pointers are 64 bits.
|
|
|
|
@item -mcmodel=medany
|
|
@opindex mcmodel=medany
|
|
Generate code for the Medium/Anywhere code model: the program may be linked
|
|
anywhere in the address space, the text segment must be less than
|
|
2G bytes, and data segment must be within 2G of the text segment.
|
|
Pointers are 64 bits.
|
|
|
|
@item -mcmodel=embmedany
|
|
@opindex mcmodel=embmedany
|
|
Generate code for the Medium/Anywhere code model for embedded systems:
|
|
assume a 32-bit text and a 32-bit data segment, both starting anywhere
|
|
(determined at link time). Register %g4 points to the base of the
|
|
data segment. Pointers are still 64 bits.
|
|
Programs are statically linked, PIC is not supported.
|
|
|
|
@item -mstack-bias
|
|
@itemx -mno-stack-bias
|
|
@opindex mstack-bias
|
|
@opindex mno-stack-bias
|
|
With @option{-mstack-bias}, GCC assumes that the stack pointer, and
|
|
frame pointer if present, are offset by @minus{}2047 which must be added back
|
|
when making stack frame references.
|
|
Otherwise, assume no such offset is present.
|
|
@end table
|
|
|
|
@node Convex Options
|
|
@subsection Convex Options
|
|
@cindex Convex options
|
|
|
|
These @samp{-m} options are defined for Convex:
|
|
|
|
@table @gcctabopt
|
|
@item -mc1
|
|
@opindex mc1
|
|
Generate output for C1. The code will run on any Convex machine.
|
|
The preprocessor symbol @code{__convex__c1__} is defined.
|
|
|
|
@item -mc2
|
|
@opindex mc2
|
|
Generate output for C2. Uses instructions not available on C1.
|
|
Scheduling and other optimizations are chosen for max performance on C2.
|
|
The preprocessor symbol @code{__convex_c2__} is defined.
|
|
|
|
@item -mc32
|
|
@opindex mc32
|
|
Generate output for C32xx. Uses instructions not available on C1.
|
|
Scheduling and other optimizations are chosen for max performance on C32.
|
|
The preprocessor symbol @code{__convex_c32__} is defined.
|
|
|
|
@item -mc34
|
|
@opindex mc34
|
|
Generate output for C34xx. Uses instructions not available on C1.
|
|
Scheduling and other optimizations are chosen for max performance on C34.
|
|
The preprocessor symbol @code{__convex_c34__} is defined.
|
|
|
|
@item -mc38
|
|
@opindex mc38
|
|
Generate output for C38xx. Uses instructions not available on C1.
|
|
Scheduling and other optimizations are chosen for max performance on C38.
|
|
The preprocessor symbol @code{__convex_c38__} is defined.
|
|
|
|
@item -margcount
|
|
@opindex margcount
|
|
Generate code which puts an argument count in the word preceding each
|
|
argument list. This is compatible with regular CC, and a few programs
|
|
may need the argument count word. GDB and other source-level debuggers
|
|
do not need it; this info is in the symbol table.
|
|
|
|
@item -mnoargcount
|
|
@opindex mnoargcount
|
|
Omit the argument count word. This is the default.
|
|
|
|
@item -mvolatile-cache
|
|
@opindex mvolatile-cache
|
|
Allow volatile references to be cached. This is the default.
|
|
|
|
@item -mvolatile-nocache
|
|
@opindex mvolatile-nocache
|
|
Volatile references bypass the data cache, going all the way to memory.
|
|
This is only needed for multi-processor code that does not use standard
|
|
synchronization instructions. Making non-volatile references to volatile
|
|
locations will not necessarily work.
|
|
|
|
@item -mlong32
|
|
@opindex mlong32
|
|
Type long is 32 bits, the same as type int. This is the default.
|
|
|
|
@item -mlong64
|
|
@opindex mlong64
|
|
Type long is 64 bits, the same as type long long. This option is useless,
|
|
because no library support exists for it.
|
|
@end table
|
|
|
|
@node AMD29K Options
|
|
@subsection AMD29K Options
|
|
@cindex AMD29K options
|
|
|
|
These @samp{-m} options are defined for the AMD Am29000:
|
|
|
|
@table @gcctabopt
|
|
@item -mdw
|
|
@opindex mdw
|
|
@cindex DW bit (29k)
|
|
Generate code that assumes the @code{DW} bit is set, i.e., that byte and
|
|
halfword operations are directly supported by the hardware. This is the
|
|
default.
|
|
|
|
@item -mndw
|
|
@opindex mndw
|
|
Generate code that assumes the @code{DW} bit is not set.
|
|
|
|
@item -mbw
|
|
@opindex mbw
|
|
@cindex byte writes (29k)
|
|
Generate code that assumes the system supports byte and halfword write
|
|
operations. This is the default.
|
|
|
|
@item -mnbw
|
|
@opindex mnbw
|
|
Generate code that assumes the systems does not support byte and
|
|
halfword write operations. @option{-mnbw} implies @option{-mndw}.
|
|
|
|
@item -msmall
|
|
@opindex msmall
|
|
@cindex memory model (29k)
|
|
Use a small memory model that assumes that all function addresses are
|
|
either within a single 256 KB segment or at an absolute address of less
|
|
than 256k. This allows the @code{call} instruction to be used instead
|
|
of a @code{const}, @code{consth}, @code{calli} sequence.
|
|
|
|
@item -mnormal
|
|
@opindex mnormal
|
|
Use the normal memory model: Generate @code{call} instructions only when
|
|
calling functions in the same file and @code{calli} instructions
|
|
otherwise. This works if each file occupies less than 256 KB but allows
|
|
the entire executable to be larger than 256 KB@. This is the default.
|
|
|
|
@item -mlarge
|
|
@opindex mlarge
|
|
Always use @code{calli} instructions. Specify this option if you expect
|
|
a single file to compile into more than 256 KB of code.
|
|
|
|
@item -m29050
|
|
@opindex m29050
|
|
@cindex processor selection (29k)
|
|
Generate code for the Am29050.
|
|
|
|
@item -m29000
|
|
@opindex m29000
|
|
Generate code for the Am29000. This is the default.
|
|
|
|
@item -mkernel-registers
|
|
@opindex mkernel-registers
|
|
@cindex kernel and user registers (29k)
|
|
Generate references to registers @code{gr64-gr95} instead of to
|
|
registers @code{gr96-gr127}. This option can be used when compiling
|
|
kernel code that wants a set of global registers disjoint from that used
|
|
by user-mode code.
|
|
|
|
Note that when this option is used, register names in @samp{-f} flags
|
|
must use the normal, user-mode, names.
|
|
|
|
@item -muser-registers
|
|
@opindex muser-registers
|
|
Use the normal set of global registers, @code{gr96-gr127}. This is the
|
|
default.
|
|
|
|
@item -mstack-check
|
|
@itemx -mno-stack-check
|
|
@opindex mstack-check
|
|
@opindex mno-stack-check
|
|
@cindex stack checks (29k)
|
|
Insert (or do not insert) a call to @code{__msp_check} after each stack
|
|
adjustment. This is often used for kernel code.
|
|
|
|
@item -mstorem-bug
|
|
@itemx -mno-storem-bug
|
|
@opindex mstorem-bug
|
|
@opindex mno-storem-bug
|
|
@cindex storem bug (29k)
|
|
@option{-mstorem-bug} handles 29k processors which cannot handle the
|
|
separation of a mtsrim insn and a storem instruction (most 29000 chips
|
|
to date, but not the 29050).
|
|
|
|
@item -mno-reuse-arg-regs
|
|
@itemx -mreuse-arg-regs
|
|
@opindex mno-reuse-arg-regs
|
|
@opindex mreuse-arg-regs
|
|
@option{-mno-reuse-arg-regs} tells the compiler to only use incoming argument
|
|
registers for copying out arguments. This helps detect calling a function
|
|
with fewer arguments than it was declared with.
|
|
|
|
@item -mno-impure-text
|
|
@itemx -mimpure-text
|
|
@opindex mno-impure-text
|
|
@opindex mimpure-text
|
|
@option{-mimpure-text}, used in addition to @option{-shared}, tells the compiler to
|
|
not pass @option{-assert pure-text} to the linker when linking a shared object.
|
|
|
|
@item -msoft-float
|
|
@opindex msoft-float
|
|
Generate output containing library calls for floating point.
|
|
@strong{Warning:} the requisite libraries are not part of GCC@.
|
|
Normally the facilities of the machine's usual C compiler are used, but
|
|
this can't be done directly in cross-compilation. You must make your
|
|
own arrangements to provide suitable library functions for
|
|
cross-compilation.
|
|
|
|
@item -mno-multm
|
|
@opindex mno-multm
|
|
Do not generate multm or multmu instructions. This is useful for some embedded
|
|
systems which do not have trap handlers for these instructions.
|
|
@end table
|
|
|
|
@node ARM Options
|
|
@subsection ARM Options
|
|
@cindex ARM options
|
|
|
|
These @samp{-m} options are defined for Advanced RISC Machines (ARM)
|
|
architectures:
|
|
|
|
@table @gcctabopt
|
|
@item -mapcs-frame
|
|
@opindex mapcs-frame
|
|
Generate a stack frame that is compliant with the ARM Procedure Call
|
|
Standard for all functions, even if this is not strictly necessary for
|
|
correct execution of the code. Specifying @option{-fomit-frame-pointer}
|
|
with this option will cause the stack frames not to be generated for
|
|
leaf functions. The default is @option{-mno-apcs-frame}.
|
|
|
|
@item -mapcs
|
|
@opindex mapcs
|
|
This is a synonym for @option{-mapcs-frame}.
|
|
|
|
@item -mapcs-26
|
|
@opindex mapcs-26
|
|
Generate code for a processor running with a 26-bit program counter,
|
|
and conforming to the function calling standards for the APCS 26-bit
|
|
option. This option replaces the @option{-m2} and @option{-m3} options
|
|
of previous releases of the compiler.
|
|
|
|
@item -mapcs-32
|
|
@opindex mapcs-32
|
|
Generate code for a processor running with a 32-bit program counter,
|
|
and conforming to the function calling standards for the APCS 32-bit
|
|
option. This option replaces the @option{-m6} option of previous releases
|
|
of the compiler.
|
|
|
|
@ignore
|
|
@c not currently implemented
|
|
@item -mapcs-stack-check
|
|
@opindex mapcs-stack-check
|
|
Generate code to check the amount of stack space available upon entry to
|
|
every function (that actually uses some stack space). If there is
|
|
insufficient space available then either the function
|
|
@samp{__rt_stkovf_split_small} or @samp{__rt_stkovf_split_big} will be
|
|
called, depending upon the amount of stack space required. The run time
|
|
system is required to provide these functions. The default is
|
|
@option{-mno-apcs-stack-check}, since this produces smaller code.
|
|
|
|
@c not currently implemented
|
|
@item -mapcs-float
|
|
@opindex mapcs-float
|
|
Pass floating point arguments using the float point registers. This is
|
|
one of the variants of the APCS@. This option is recommended if the
|
|
target hardware has a floating point unit or if a lot of floating point
|
|
arithmetic is going to be performed by the code. The default is
|
|
@option{-mno-apcs-float}, since integer only code is slightly increased in
|
|
size if @option{-mapcs-float} is used.
|
|
|
|
@c not currently implemented
|
|
@item -mapcs-reentrant
|
|
@opindex mapcs-reentrant
|
|
Generate reentrant, position independent code. The default is
|
|
@option{-mno-apcs-reentrant}.
|
|
@end ignore
|
|
|
|
@item -mthumb-interwork
|
|
@opindex mthumb-interwork
|
|
Generate code which supports calling between the ARM and Thumb
|
|
instruction sets. Without this option the two instruction sets cannot
|
|
be reliably used inside one program. The default is
|
|
@option{-mno-thumb-interwork}, since slightly larger code is generated
|
|
when @option{-mthumb-interwork} is specified.
|
|
|
|
@item -mno-sched-prolog
|
|
@opindex mno-sched-prolog
|
|
Prevent the reordering of instructions in the function prolog, or the
|
|
merging of those instruction with the instructions in the function's
|
|
body. This means that all functions will start with a recognizable set
|
|
of instructions (or in fact one of a choice from a small set of
|
|
different function prologues), and this information can be used to
|
|
locate the start if functions inside an executable piece of code. The
|
|
default is @option{-msched-prolog}.
|
|
|
|
@item -mhard-float
|
|
@opindex mhard-float
|
|
Generate output containing floating point instructions. This is the
|
|
default.
|
|
|
|
@item -msoft-float
|
|
@opindex msoft-float
|
|
Generate output containing library calls for floating point.
|
|
@strong{Warning:} the requisite libraries are not available for all ARM
|
|
targets. Normally the facilities of the machine's usual C compiler are
|
|
used, but this cannot be done directly in cross-compilation. You must make
|
|
your own arrangements to provide suitable library functions for
|
|
cross-compilation.
|
|
|
|
@option{-msoft-float} changes the calling convention in the output file;
|
|
therefore, it is only useful if you compile @emph{all} of a program with
|
|
this option. In particular, you need to compile @file{libgcc.a}, the
|
|
library that comes with GCC, with @option{-msoft-float} in order for
|
|
this to work.
|
|
|
|
@item -mlittle-endian
|
|
@opindex mlittle-endian
|
|
Generate code for a processor running in little-endian mode. This is
|
|
the default for all standard configurations.
|
|
|
|
@item -mbig-endian
|
|
@opindex mbig-endian
|
|
Generate code for a processor running in big-endian mode; the default is
|
|
to compile code for a little-endian processor.
|
|
|
|
@item -mwords-little-endian
|
|
@opindex mwords-little-endian
|
|
This option only applies when generating code for big-endian processors.
|
|
Generate code for a little-endian word order but a big-endian byte
|
|
order. That is, a byte order of the form @samp{32107654}. Note: this
|
|
option should only be used if you require compatibility with code for
|
|
big-endian ARM processors generated by versions of the compiler prior to
|
|
2.8.
|
|
|
|
@item -malignment-traps
|
|
@opindex malignment-traps
|
|
Generate code that will not trap if the MMU has alignment traps enabled.
|
|
On ARM architectures prior to ARMv4, there were no instructions to
|
|
access half-word objects stored in memory. However, when reading from
|
|
memory a feature of the ARM architecture allows a word load to be used,
|
|
even if the address is unaligned, and the processor core will rotate the
|
|
data as it is being loaded. This option tells the compiler that such
|
|
misaligned accesses will cause a MMU trap and that it should instead
|
|
synthesise the access as a series of byte accesses. The compiler can
|
|
still use word accesses to load half-word data if it knows that the
|
|
address is aligned to a word boundary.
|
|
|
|
This option is ignored when compiling for ARM architecture 4 or later,
|
|
since these processors have instructions to directly access half-word
|
|
objects in memory.
|
|
|
|
@item -mno-alignment-traps
|
|
@opindex mno-alignment-traps
|
|
Generate code that assumes that the MMU will not trap unaligned
|
|
accesses. This produces better code when the target instruction set
|
|
does not have half-word memory operations (i.e.@: implementations prior to
|
|
ARMv4).
|
|
|
|
Note that you cannot use this option to access unaligned word objects,
|
|
since the processor will only fetch one 32-bit aligned object from
|
|
memory.
|
|
|
|
The default setting for most targets is @option{-mno-alignment-traps}, since
|
|
this produces better code when there are no half-word memory
|
|
instructions available.
|
|
|
|
@item -mshort-load-bytes
|
|
@itemx -mno-short-load-words
|
|
@opindex mshort-load-bytes
|
|
@opindex mno-short-load-words
|
|
These are deprecated aliases for @option{-malignment-traps}.
|
|
|
|
@item -mno-short-load-bytes
|
|
@itemx -mshort-load-words
|
|
@opindex mno-short-load-bytes
|
|
@opindex mshort-load-words
|
|
This are deprecated aliases for @option{-mno-alignment-traps}.
|
|
|
|
@item -mbsd
|
|
@opindex mbsd
|
|
This option only applies to RISC iX@. Emulate the native BSD-mode
|
|
compiler. This is the default if @option{-ansi} is not specified.
|
|
|
|
@item -mxopen
|
|
@opindex mxopen
|
|
This option only applies to RISC iX@. Emulate the native X/Open-mode
|
|
compiler.
|
|
|
|
@item -mno-symrename
|
|
@opindex mno-symrename
|
|
This option only applies to RISC iX@. Do not run the assembler
|
|
post-processor, @samp{symrename}, after code has been assembled.
|
|
Normally it is necessary to modify some of the standard symbols in
|
|
preparation for linking with the RISC iX C library; this option
|
|
suppresses this pass. The post-processor is never run when the
|
|
compiler is built for cross-compilation.
|
|
|
|
@item -mcpu=@var{name}
|
|
@opindex mcpu
|
|
This specifies the name of the target ARM processor. GCC uses this name
|
|
to determine what kind of instructions it can emit when generating
|
|
assembly code. Permissible names are: @samp{arm2}, @samp{arm250},
|
|
@samp{arm3}, @samp{arm6}, @samp{arm60}, @samp{arm600}, @samp{arm610},
|
|
@samp{arm620}, @samp{arm7}, @samp{arm7m}, @samp{arm7d}, @samp{arm7dm},
|
|
@samp{arm7di}, @samp{arm7dmi}, @samp{arm70}, @samp{arm700},
|
|
@samp{arm700i}, @samp{arm710}, @samp{arm710c}, @samp{arm7100},
|
|
@samp{arm7500}, @samp{arm7500fe}, @samp{arm7tdmi}, @samp{arm8},
|
|
@samp{strongarm}, @samp{strongarm110}, @samp{strongarm1100},
|
|
@samp{arm8}, @samp{arm810}, @samp{arm9}, @samp{arm9e}, @samp{arm920},
|
|
@samp{arm920t}, @samp{arm940t}, @samp{arm9tdmi}, @samp{arm10tdmi},
|
|
@samp{arm1020t}, @samp{xscale}.
|
|
|
|
@itemx -mtune=@var{name}
|
|
@opindex mtune
|
|
This option is very similar to the @option{-mcpu=} option, except that
|
|
instead of specifying the actual target processor type, and hence
|
|
restricting which instructions can be used, it specifies that GCC should
|
|
tune the performance of the code as if the target were of the type
|
|
specified in this option, but still choosing the instructions that it
|
|
will generate based on the cpu specified by a @option{-mcpu=} option.
|
|
For some ARM implementations better performance can be obtained by using
|
|
this option.
|
|
|
|
@item -march=@var{name}
|
|
@opindex march
|
|
This specifies the name of the target ARM architecture. GCC uses this
|
|
name to determine what kind of instructions it can emit when generating
|
|
assembly code. This option can be used in conjunction with or instead
|
|
of the @option{-mcpu=} option. Permissible names are: @samp{armv2},
|
|
@samp{armv2a}, @samp{armv3}, @samp{armv3m}, @samp{armv4}, @samp{armv4t},
|
|
@samp{armv5}, @samp{armv5t}, @samp{armv5te}.
|
|
|
|
@item -mfpe=@var{number}
|
|
@itemx -mfp=@var{number}
|
|
@opindex mfpe
|
|
@opindex mfp
|
|
This specifies the version of the floating point emulation available on
|
|
the target. Permissible values are 2 and 3. @option{-mfp=} is a synonym
|
|
for @option{-mfpe=}, for compatibility with older versions of GCC@.
|
|
|
|
@item -mstructure-size-boundary=@var{n}
|
|
@opindex mstructure-size-boundary
|
|
The size of all structures and unions will be rounded up to a multiple
|
|
of the number of bits set by this option. Permissible values are 8 and
|
|
32. The default value varies for different toolchains. For the COFF
|
|
targeted toolchain the default value is 8. Specifying the larger number
|
|
can produce faster, more efficient code, but can also increase the size
|
|
of the program. The two values are potentially incompatible. Code
|
|
compiled with one value cannot necessarily expect to work with code or
|
|
libraries compiled with the other value, if they exchange information
|
|
using structures or unions.
|
|
|
|
@item -mabort-on-noreturn
|
|
@opindex mabort-on-noreturn
|
|
Generate a call to the function @code{abort} at the end of a
|
|
@code{noreturn} function. It will be executed if the function tries to
|
|
return.
|
|
|
|
@item -mlong-calls
|
|
@itemx -mno-long-calls
|
|
@opindex mlong-calls
|
|
@opindex mno-long-calls
|
|
Tells the compiler to perform function calls by first loading the
|
|
address of the function into a register and then performing a subroutine
|
|
call on this register. This switch is needed if the target function
|
|
will lie outside of the 64 megabyte addressing range of the offset based
|
|
version of subroutine call instruction.
|
|
|
|
Even if this switch is enabled, not all function calls will be turned
|
|
into long calls. The heuristic is that static functions, functions
|
|
which have the @samp{short-call} attribute, functions that are inside
|
|
the scope of a @samp{#pragma no_long_calls} directive and functions whose
|
|
definitions have already been compiled within the current compilation
|
|
unit, will not be turned into long calls. The exception to this rule is
|
|
that weak function definitions, functions with the @samp{long-call}
|
|
attribute or the @samp{section} attribute, and functions that are within
|
|
the scope of a @samp{#pragma long_calls} directive, will always be
|
|
turned into long calls.
|
|
|
|
This feature is not enabled by default. Specifying
|
|
@option{-mno-long-calls} will restore the default behavior, as will
|
|
placing the function calls within the scope of a @samp{#pragma
|
|
long_calls_off} directive. Note these switches have no effect on how
|
|
the compiler generates code to handle function calls via function
|
|
pointers.
|
|
|
|
@item -mnop-fun-dllimport
|
|
@opindex mnop-fun-dllimport
|
|
Disable support for the @code{dllimport} attribute.
|
|
|
|
@item -msingle-pic-base
|
|
@opindex msingle-pic-base
|
|
Treat the register used for PIC addressing as read-only, rather than
|
|
loading it in the prologue for each function. The run-time system is
|
|
responsible for initializing this register with an appropriate value
|
|
before execution begins.
|
|
|
|
@item -mpic-register=@var{reg}
|
|
@opindex mpic-register
|
|
Specify the register to be used for PIC addressing. The default is R10
|
|
unless stack-checking is enabled, when R9 is used.
|
|
|
|
@item -mpoke-function-name
|
|
@opindex mpoke-function-name
|
|
Write the name of each function into the text section, directly
|
|
preceding the function prologue. The generated code is similar to this:
|
|
|
|
@smallexample
|
|
t0
|
|
.ascii "arm_poke_function_name", 0
|
|
.align
|
|
t1
|
|
.word 0xff000000 + (t1 - t0)
|
|
arm_poke_function_name
|
|
mov ip, sp
|
|
stmfd sp!, @{fp, ip, lr, pc@}
|
|
sub fp, ip, #4
|
|
@end smallexample
|
|
|
|
When performing a stack backtrace, code can inspect the value of
|
|
@code{pc} stored at @code{fp + 0}. If the trace function then looks at
|
|
location @code{pc - 12} and the top 8 bits are set, then we know that
|
|
there is a function name embedded immediately preceding this location
|
|
and has length @code{((pc[-3]) & 0xff000000)}.
|
|
|
|
@item -mthumb
|
|
@opindex mthumb
|
|
Generate code for the 16-bit Thumb instruction set. The default is to
|
|
use the 32-bit ARM instruction set.
|
|
|
|
@item -mtpcs-frame
|
|
@opindex mtpcs-frame
|
|
Generate a stack frame that is compliant with the Thumb Procedure Call
|
|
Standard for all non-leaf functions. (A leaf function is one that does
|
|
not call any other functions.) The default is @option{-mno-tpcs-frame}.
|
|
|
|
@item -mtpcs-leaf-frame
|
|
@opindex mtpcs-leaf-frame
|
|
Generate a stack frame that is compliant with the Thumb Procedure Call
|
|
Standard for all leaf functions. (A leaf function is one that does
|
|
not call any other functions.) The default is @option{-mno-apcs-leaf-frame}.
|
|
|
|
@item -mcallee-super-interworking
|
|
@opindex mcallee-super-interworking
|
|
Gives all externally visible functions in the file being compiled an ARM
|
|
instruction set header which switches to Thumb mode before executing the
|
|
rest of the function. This allows these functions to be called from
|
|
non-interworking code.
|
|
|
|
@item -mcaller-super-interworking
|
|
@opindex mcaller-super-interworking
|
|
Allows calls via function pointers (including virtual functions) to
|
|
execute correctly regardless of whether the target code has been
|
|
compiled for interworking or not. There is a small overhead in the cost
|
|
of executing a function pointer if this option is enabled.
|
|
|
|
@end table
|
|
|
|
@node MN10200 Options
|
|
@subsection MN10200 Options
|
|
@cindex MN10200 options
|
|
These @option{-m} options are defined for Matsushita MN10200 architectures:
|
|
@table @gcctabopt
|
|
|
|
@item -mrelax
|
|
@opindex mrelax
|
|
Indicate to the linker that it should perform a relaxation optimization pass
|
|
to shorten branches, calls and absolute memory addresses. This option only
|
|
has an effect when used on the command line for the final link step.
|
|
|
|
This option makes symbolic debugging impossible.
|
|
@end table
|
|
|
|
@node MN10300 Options
|
|
@subsection MN10300 Options
|
|
@cindex MN10300 options
|
|
These @option{-m} options are defined for Matsushita MN10300 architectures:
|
|
|
|
@table @gcctabopt
|
|
@item -mmult-bug
|
|
@opindex mmult-bug
|
|
Generate code to avoid bugs in the multiply instructions for the MN10300
|
|
processors. This is the default.
|
|
|
|
@item -mno-mult-bug
|
|
@opindex mno-mult-bug
|
|
Do not generate code to avoid bugs in the multiply instructions for the
|
|
MN10300 processors.
|
|
|
|
@item -mam33
|
|
@opindex mam33
|
|
Generate code which uses features specific to the AM33 processor.
|
|
|
|
@item -mno-am33
|
|
@opindex mno-am33
|
|
Do not generate code which uses features specific to the AM33 processor. This
|
|
is the default.
|
|
|
|
@item -mno-crt0
|
|
@opindex mno-crt0
|
|
Do not link in the C run-time initialization object file.
|
|
|
|
@item -mrelax
|
|
@opindex mrelax
|
|
Indicate to the linker that it should perform a relaxation optimization pass
|
|
to shorten branches, calls and absolute memory addresses. This option only
|
|
has an effect when used on the command line for the final link step.
|
|
|
|
This option makes symbolic debugging impossible.
|
|
@end table
|
|
|
|
|
|
@node M32R/D Options
|
|
@subsection M32R/D Options
|
|
@cindex M32R/D options
|
|
|
|
These @option{-m} options are defined for Mitsubishi M32R/D architectures:
|
|
|
|
@table @gcctabopt
|
|
@item -m32rx
|
|
@opindex m32rx
|
|
Generate code for the M32R/X@.
|
|
|
|
@item -m32r
|
|
@opindex m32r
|
|
Generate code for the M32R@. This is the default.
|
|
|
|
@item -mcode-model=small
|
|
@opindex mcode-model=small
|
|
Assume all objects live in the lower 16MB of memory (so that their addresses
|
|
can be loaded with the @code{ld24} instruction), and assume all subroutines
|
|
are reachable with the @code{bl} instruction.
|
|
This is the default.
|
|
|
|
The addressability of a particular object can be set with the
|
|
@code{model} attribute.
|
|
|
|
@item -mcode-model=medium
|
|
@opindex mcode-model=medium
|
|
Assume objects may be anywhere in the 32-bit address space (the compiler
|
|
will generate @code{seth/add3} instructions to load their addresses), and
|
|
assume all subroutines are reachable with the @code{bl} instruction.
|
|
|
|
@item -mcode-model=large
|
|
@opindex mcode-model=large
|
|
Assume objects may be anywhere in the 32-bit address space (the compiler
|
|
will generate @code{seth/add3} instructions to load their addresses), and
|
|
assume subroutines may not be reachable with the @code{bl} instruction
|
|
(the compiler will generate the much slower @code{seth/add3/jl}
|
|
instruction sequence).
|
|
|
|
@item -msdata=none
|
|
@opindex msdata=none
|
|
Disable use of the small data area. Variables will be put into
|
|
one of @samp{.data}, @samp{bss}, or @samp{.rodata} (unless the
|
|
@code{section} attribute has been specified).
|
|
This is the default.
|
|
|
|
The small data area consists of sections @samp{.sdata} and @samp{.sbss}.
|
|
Objects may be explicitly put in the small data area with the
|
|
@code{section} attribute using one of these sections.
|
|
|
|
@item -msdata=sdata
|
|
@opindex msdata=sdata
|
|
Put small global and static data in the small data area, but do not
|
|
generate special code to reference them.
|
|
|
|
@item -msdata=use
|
|
@opindex msdata=use
|
|
Put small global and static data in the small data area, and generate
|
|
special instructions to reference them.
|
|
|
|
@item -G @var{num}
|
|
@opindex G
|
|
@cindex smaller data references
|
|
Put global and static objects less than or equal to @var{num} bytes
|
|
into the small data or bss sections instead of the normal data or bss
|
|
sections. The default value of @var{num} is 8.
|
|
The @option{-msdata} option must be set to one of @samp{sdata} or @samp{use}
|
|
for this option to have any effect.
|
|
|
|
All modules should be compiled with the same @option{-G @var{num}} value.
|
|
Compiling with different values of @var{num} may or may not work; if it
|
|
doesn't the linker will give an error message---incorrect code will not be
|
|
generated.
|
|
|
|
@end table
|
|
|
|
@node M88K Options
|
|
@subsection M88K Options
|
|
@cindex M88k options
|
|
|
|
These @samp{-m} options are defined for Motorola 88k architectures:
|
|
|
|
@table @gcctabopt
|
|
@item -m88000
|
|
@opindex m88000
|
|
Generate code that works well on both the m88100 and the
|
|
m88110.
|
|
|
|
@item -m88100
|
|
@opindex m88100
|
|
Generate code that works best for the m88100, but that also
|
|
runs on the m88110.
|
|
|
|
@item -m88110
|
|
@opindex m88110
|
|
Generate code that works best for the m88110, and may not run
|
|
on the m88100.
|
|
|
|
@item -mbig-pic
|
|
@opindex mbig-pic
|
|
Obsolete option to be removed from the next revision.
|
|
Use @option{-fPIC}.
|
|
|
|
@item -midentify-revision
|
|
@opindex midentify-revision
|
|
@cindex identifying source, compiler (88k)
|
|
Include an @code{ident} directive in the assembler output recording the
|
|
source file name, compiler name and version, timestamp, and compilation
|
|
flags used.
|
|
|
|
@item -mno-underscores
|
|
@opindex mno-underscores
|
|
@cindex underscores, avoiding (88k)
|
|
In assembler output, emit symbol names without adding an underscore
|
|
character at the beginning of each name. The default is to use an
|
|
underscore as prefix on each name.
|
|
|
|
@item -mocs-debug-info
|
|
@itemx -mno-ocs-debug-info
|
|
@opindex mocs-debug-info
|
|
@opindex mno-ocs-debug-info
|
|
@cindex OCS (88k)
|
|
@cindex debugging, 88k OCS
|
|
Include (or omit) additional debugging information (about registers used
|
|
in each stack frame) as specified in the 88open Object Compatibility
|
|
Standard, ``OCS''@. This extra information allows debugging of code that
|
|
has had the frame pointer eliminated. The default for DG/UX, SVr4, and
|
|
Delta 88 SVr3.2 is to include this information; other 88k configurations
|
|
omit this information by default.
|
|
|
|
@item -mocs-frame-position
|
|
@opindex mocs-frame-position
|
|
@cindex register positions in frame (88k)
|
|
When emitting COFF debugging information for automatic variables and
|
|
parameters stored on the stack, use the offset from the canonical frame
|
|
address, which is the stack pointer (register 31) on entry to the
|
|
function. The DG/UX, SVr4, Delta88 SVr3.2, and BCS configurations use
|
|
@option{-mocs-frame-position}; other 88k configurations have the default
|
|
@option{-mno-ocs-frame-position}.
|
|
|
|
@item -mno-ocs-frame-position
|
|
@opindex mno-ocs-frame-position
|
|
@cindex register positions in frame (88k)
|
|
When emitting COFF debugging information for automatic variables and
|
|
parameters stored on the stack, use the offset from the frame pointer
|
|
register (register 30). When this option is in effect, the frame
|
|
pointer is not eliminated when debugging information is selected by the
|
|
-g switch.
|
|
|
|
@item -moptimize-arg-area
|
|
@opindex moptimize-arg-area
|
|
@cindex arguments in frame (88k)
|
|
Save space by reorganizing the stack frame. This option generates code
|
|
that does not agree with the 88open specifications, but uses less
|
|
memory.
|
|
|
|
@itemx -mno-optimize-arg-area
|
|
@opindex mno-optimize-arg-area
|
|
Do not reorganize the stack frame to save space. This is the default.
|
|
The generated conforms to the specification, but uses more memory.
|
|
|
|
@item -mshort-data-@var{num}
|
|
@opindex mshort-data
|
|
@cindex smaller data references (88k)
|
|
@cindex r0-relative references (88k)
|
|
Generate smaller data references by making them relative to @code{r0},
|
|
which allows loading a value using a single instruction (rather than the
|
|
usual two). You control which data references are affected by
|
|
specifying @var{num} with this option. For example, if you specify
|
|
@option{-mshort-data-512}, then the data references affected are those
|
|
involving displacements of less than 512 bytes.
|
|
@option{-mshort-data-@var{num}} is not effective for @var{num} greater
|
|
than 64k.
|
|
|
|
@item -mserialize-volatile
|
|
@opindex mserialize-volatile
|
|
@itemx -mno-serialize-volatile
|
|
@opindex mno-serialize-volatile
|
|
@cindex sequential consistency on 88k
|
|
Do, or don't, generate code to guarantee sequential consistency
|
|
of volatile memory references. By default, consistency is
|
|
guaranteed.
|
|
|
|
The order of memory references made by the MC88110 processor does
|
|
not always match the order of the instructions requesting those
|
|
references. In particular, a load instruction may execute before
|
|
a preceding store instruction. Such reordering violates
|
|
sequential consistency of volatile memory references, when there
|
|
are multiple processors. When consistency must be guaranteed,
|
|
GCC generates special instructions, as needed, to force
|
|
execution in the proper order.
|
|
|
|
The MC88100 processor does not reorder memory references and so
|
|
always provides sequential consistency. However, by default, GCC
|
|
generates the special instructions to guarantee consistency
|
|
even when you use @option{-m88100}, so that the code may be run on an
|
|
MC88110 processor. If you intend to run your code only on the
|
|
MC88100 processor, you may use @option{-mno-serialize-volatile}.
|
|
|
|
The extra code generated to guarantee consistency may affect the
|
|
performance of your application. If you know that you can safely
|
|
forgo this guarantee, you may use @option{-mno-serialize-volatile}.
|
|
|
|
@item -msvr4
|
|
@itemx -msvr3
|
|
@opindex msvr4
|
|
@opindex msvr3
|
|
@cindex assembler syntax, 88k
|
|
@cindex SVr4
|
|
Turn on (@option{-msvr4}) or off (@option{-msvr3}) compiler extensions
|
|
related to System V release 4 (SVr4). This controls the following:
|
|
|
|
@enumerate
|
|
@item
|
|
Which variant of the assembler syntax to emit.
|
|
@item
|
|
@option{-msvr4} makes the C preprocessor recognize @samp{#pragma weak}
|
|
that is used on System V release 4.
|
|
@item
|
|
@option{-msvr4} makes GCC issue additional declaration directives used in
|
|
SVr4.
|
|
@end enumerate
|
|
|
|
@option{-msvr4} is the default for the m88k-motorola-sysv4 and
|
|
m88k-dg-dgux m88k configurations. @option{-msvr3} is the default for all
|
|
other m88k configurations.
|
|
|
|
@item -mversion-03.00
|
|
@opindex mversion-03.00
|
|
This option is obsolete, and is ignored.
|
|
@c ??? which asm syntax better for GAS? option there too?
|
|
|
|
@item -mno-check-zero-division
|
|
@itemx -mcheck-zero-division
|
|
@opindex mno-check-zero-division
|
|
@opindex mcheck-zero-division
|
|
@cindex zero division on 88k
|
|
Do, or don't, generate code to guarantee that integer division by
|
|
zero will be detected. By default, detection is guaranteed.
|
|
|
|
Some models of the MC88100 processor fail to trap upon integer
|
|
division by zero under certain conditions. By default, when
|
|
compiling code that might be run on such a processor, GCC
|
|
generates code that explicitly checks for zero-valued divisors
|
|
and traps with exception number 503 when one is detected. Use of
|
|
@option{-mno-check-zero-division} suppresses such checking for code
|
|
generated to run on an MC88100 processor.
|
|
|
|
GCC assumes that the MC88110 processor correctly detects all instances
|
|
of integer division by zero. When @option{-m88110} is specified, no
|
|
explicit checks for zero-valued divisors are generated, and both
|
|
@option{-mcheck-zero-division} and @option{-mno-check-zero-division} are
|
|
ignored.
|
|
|
|
@item -muse-div-instruction
|
|
@opindex muse-div-instruction
|
|
@cindex divide instruction, 88k
|
|
Use the div instruction for signed integer division on the
|
|
MC88100 processor. By default, the div instruction is not used.
|
|
|
|
On the MC88100 processor the signed integer division instruction
|
|
div) traps to the operating system on a negative operand. The
|
|
operating system transparently completes the operation, but at a
|
|
large cost in execution time. By default, when compiling code
|
|
that might be run on an MC88100 processor, GCC emulates signed
|
|
integer division using the unsigned integer division instruction
|
|
divu), thereby avoiding the large penalty of a trap to the
|
|
operating system. Such emulation has its own, smaller, execution
|
|
cost in both time and space. To the extent that your code's
|
|
important signed integer division operations are performed on two
|
|
nonnegative operands, it may be desirable to use the div
|
|
instruction directly.
|
|
|
|
On the MC88110 processor the div instruction (also known as the
|
|
divs instruction) processes negative operands without trapping to
|
|
the operating system. When @option{-m88110} is specified,
|
|
@option{-muse-div-instruction} is ignored, and the div instruction is used
|
|
for signed integer division.
|
|
|
|
Note that the result of dividing @code{INT_MIN} by @minus{}1 is undefined. In
|
|
particular, the behavior of such a division with and without
|
|
@option{-muse-div-instruction} may differ.
|
|
|
|
@item -mtrap-large-shift
|
|
@itemx -mhandle-large-shift
|
|
@opindex mtrap-large-shift
|
|
@opindex mhandle-large-shift
|
|
@cindex bit shift overflow (88k)
|
|
@cindex large bit shifts (88k)
|
|
Include code to detect bit-shifts of more than 31 bits; respectively,
|
|
trap such shifts or emit code to handle them properly. By default GCC
|
|
makes no special provision for large bit shifts.
|
|
|
|
@item -mwarn-passed-structs
|
|
@opindex mwarn-passed-structs
|
|
@cindex structure passing (88k)
|
|
Warn when a function passes a struct as an argument or result.
|
|
Structure-passing conventions have changed during the evolution of the C
|
|
language, and are often the source of portability problems. By default,
|
|
GCC issues no such warning.
|
|
@end table
|
|
|
|
@c break page here to avoid unsightly interparagraph stretch.
|
|
@c -zw, 2001-8-17
|
|
@page
|
|
|
|
@node RS/6000 and PowerPC Options
|
|
@subsection IBM RS/6000 and PowerPC Options
|
|
@cindex RS/6000 and PowerPC Options
|
|
@cindex IBM RS/6000 and PowerPC Options
|
|
|
|
These @samp{-m} options are defined for the IBM RS/6000 and PowerPC:
|
|
@table @gcctabopt
|
|
@item -mpower
|
|
@itemx -mno-power
|
|
@itemx -mpower2
|
|
@itemx -mno-power2
|
|
@itemx -mpowerpc
|
|
@itemx -mno-powerpc
|
|
@itemx -mpowerpc-gpopt
|
|
@itemx -mno-powerpc-gpopt
|
|
@itemx -mpowerpc-gfxopt
|
|
@itemx -mno-powerpc-gfxopt
|
|
@itemx -mpowerpc64
|
|
@itemx -mno-powerpc64
|
|
@opindex mpower
|
|
@opindex mno-power
|
|
@opindex mpower2
|
|
@opindex mno-power2
|
|
@opindex mpowerpc
|
|
@opindex mno-powerpc
|
|
@opindex mpowerpc-gpopt
|
|
@opindex mno-powerpc-gpopt
|
|
@opindex mpowerpc-gfxopt
|
|
@opindex mno-powerpc-gfxopt
|
|
@opindex mpowerpc64
|
|
@opindex mno-powerpc64
|
|
GCC supports two related instruction set architectures for the
|
|
RS/6000 and PowerPC@. The @dfn{POWER} instruction set are those
|
|
instructions supported by the @samp{rios} chip set used in the original
|
|
RS/6000 systems and the @dfn{PowerPC} instruction set is the
|
|
architecture of the Motorola MPC5xx, MPC6xx, MPC8xx microprocessors, and
|
|
the IBM 4xx microprocessors.
|
|
|
|
Neither architecture is a subset of the other. However there is a
|
|
large common subset of instructions supported by both. An MQ
|
|
register is included in processors supporting the POWER architecture.
|
|
|
|
You use these options to specify which instructions are available on the
|
|
processor you are using. The default value of these options is
|
|
determined when configuring GCC@. Specifying the
|
|
@option{-mcpu=@var{cpu_type}} overrides the specification of these
|
|
options. We recommend you use the @option{-mcpu=@var{cpu_type}} option
|
|
rather than the options listed above.
|
|
|
|
The @option{-mpower} option allows GCC to generate instructions that
|
|
are found only in the POWER architecture and to use the MQ register.
|
|
Specifying @option{-mpower2} implies @option{-power} and also allows GCC
|
|
to generate instructions that are present in the POWER2 architecture but
|
|
not the original POWER architecture.
|
|
|
|
The @option{-mpowerpc} option allows GCC to generate instructions that
|
|
are found only in the 32-bit subset of the PowerPC architecture.
|
|
Specifying @option{-mpowerpc-gpopt} implies @option{-mpowerpc} and also allows
|
|
GCC to use the optional PowerPC architecture instructions in the
|
|
General Purpose group, including floating-point square root. Specifying
|
|
@option{-mpowerpc-gfxopt} implies @option{-mpowerpc} and also allows GCC to
|
|
use the optional PowerPC architecture instructions in the Graphics
|
|
group, including floating-point select.
|
|
|
|
The @option{-mpowerpc64} option allows GCC to generate the additional
|
|
64-bit instructions that are found in the full PowerPC64 architecture
|
|
and to treat GPRs as 64-bit, doubleword quantities. GCC defaults to
|
|
@option{-mno-powerpc64}.
|
|
|
|
If you specify both @option{-mno-power} and @option{-mno-powerpc}, GCC
|
|
will use only the instructions in the common subset of both
|
|
architectures plus some special AIX common-mode calls, and will not use
|
|
the MQ register. Specifying both @option{-mpower} and @option{-mpowerpc}
|
|
permits GCC to use any instruction from either architecture and to
|
|
allow use of the MQ register; specify this for the Motorola MPC601.
|
|
|
|
@item -mnew-mnemonics
|
|
@itemx -mold-mnemonics
|
|
@opindex mnew-mnemonics
|
|
@opindex mold-mnemonics
|
|
Select which mnemonics to use in the generated assembler code. With
|
|
@option{-mnew-mnemonics}, GCC uses the assembler mnemonics defined for
|
|
the PowerPC architecture. With @option{-mold-mnemonics} it uses the
|
|
assembler mnemonics defined for the POWER architecture. Instructions
|
|
defined in only one architecture have only one mnemonic; GCC uses that
|
|
mnemonic irrespective of which of these options is specified.
|
|
|
|
GCC defaults to the mnemonics appropriate for the architecture in
|
|
use. Specifying @option{-mcpu=@var{cpu_type}} sometimes overrides the
|
|
value of these option. Unless you are building a cross-compiler, you
|
|
should normally not specify either @option{-mnew-mnemonics} or
|
|
@option{-mold-mnemonics}, but should instead accept the default.
|
|
|
|
@item -mcpu=@var{cpu_type}
|
|
@opindex mcpu
|
|
Set architecture type, register usage, choice of mnemonics, and
|
|
instruction scheduling parameters for machine type @var{cpu_type}.
|
|
Supported values for @var{cpu_type} are @samp{rios}, @samp{rios1},
|
|
@samp{rsc}, @samp{rios2}, @samp{rs64a}, @samp{601}, @samp{602},
|
|
@samp{603}, @samp{603e}, @samp{604}, @samp{604e}, @samp{620},
|
|
@samp{630}, @samp{740}, @samp{7400}, @samp{7450}, @samp{750},
|
|
@samp{power}, @samp{power2}, @samp{powerpc}, @samp{403}, @samp{505},
|
|
@samp{801}, @samp{821}, @samp{823}, and @samp{860} and @samp{common}.
|
|
|
|
@option{-mcpu=common} selects a completely generic processor. Code
|
|
generated under this option will run on any POWER or PowerPC processor.
|
|
GCC will use only the instructions in the common subset of both
|
|
architectures, and will not use the MQ register. GCC assumes a generic
|
|
processor model for scheduling purposes.
|
|
|
|
@option{-mcpu=power}, @option{-mcpu=power2}, @option{-mcpu=powerpc}, and
|
|
@option{-mcpu=powerpc64} specify generic POWER, POWER2, pure 32-bit
|
|
PowerPC (i.e., not MPC601), and 64-bit PowerPC architecture machine
|
|
types, with an appropriate, generic processor model assumed for
|
|
scheduling purposes.
|
|
|
|
The other options specify a specific processor. Code generated under
|
|
those options will run best on that processor, and may not run at all on
|
|
others.
|
|
|
|
The @option{-mcpu} options automatically enable or disable other
|
|
@option{-m} options as follows:
|
|
|
|
@table @samp
|
|
@item common
|
|
@option{-mno-power}, @option{-mno-powerc}
|
|
|
|
@item power
|
|
@itemx power2
|
|
@itemx rios1
|
|
@itemx rios2
|
|
@itemx rsc
|
|
@option{-mpower}, @option{-mno-powerpc}, @option{-mno-new-mnemonics}
|
|
|
|
@item powerpc
|
|
@itemx rs64a
|
|
@itemx 602
|
|
@itemx 603
|
|
@itemx 603e
|
|
@itemx 604
|
|
@itemx 620
|
|
@itemx 630
|
|
@itemx 740
|
|
@itemx 7400
|
|
@itemx 7450
|
|
@itemx 750
|
|
@itemx 505
|
|
@option{-mno-power}, @option{-mpowerpc}, @option{-mnew-mnemonics}
|
|
|
|
@item 601
|
|
@option{-mpower}, @option{-mpowerpc}, @option{-mnew-mnemonics}
|
|
|
|
@item 403
|
|
@itemx 821
|
|
@itemx 860
|
|
@option{-mno-power}, @option{-mpowerpc}, @option{-mnew-mnemonics}, @option{-msoft-float}
|
|
@end table
|
|
|
|
@item -mtune=@var{cpu_type}
|
|
@opindex mtune
|
|
Set the instruction scheduling parameters for machine type
|
|
@var{cpu_type}, but do not set the architecture type, register usage, or
|
|
choice of mnemonics, as @option{-mcpu=@var{cpu_type}} would. The same
|
|
values for @var{cpu_type} are used for @option{-mtune} as for
|
|
@option{-mcpu}. If both are specified, the code generated will use the
|
|
architecture, registers, and mnemonics set by @option{-mcpu}, but the
|
|
scheduling parameters set by @option{-mtune}.
|
|
|
|
@item -maltivec
|
|
@itemx -mno-altivec
|
|
@opindex maltivec
|
|
@opindex mno-altivec
|
|
These switches enable or disable the use of built-in functions that
|
|
allow access to the AltiVec instruction set. You may also need to set
|
|
@option{-mabi=altivec} to adjust the current ABI with AltiVec ABI
|
|
enhancements.
|
|
|
|
@item -mfull-toc
|
|
@itemx -mno-fp-in-toc
|
|
@itemx -mno-sum-in-toc
|
|
@itemx -mminimal-toc
|
|
@opindex mfull-toc
|
|
@opindex mno-fp-in-toc
|
|
@opindex mno-sum-in-toc
|
|
@opindex mminimal-toc
|
|
Modify generation of the TOC (Table Of Contents), which is created for
|
|
every executable file. The @option{-mfull-toc} option is selected by
|
|
default. In that case, GCC will allocate at least one TOC entry for
|
|
each unique non-automatic variable reference in your program. GCC
|
|
will also place floating-point constants in the TOC@. However, only
|
|
16,384 entries are available in the TOC@.
|
|
|
|
If you receive a linker error message that saying you have overflowed
|
|
the available TOC space, you can reduce the amount of TOC space used
|
|
with the @option{-mno-fp-in-toc} and @option{-mno-sum-in-toc} options.
|
|
@option{-mno-fp-in-toc} prevents GCC from putting floating-point
|
|
constants in the TOC and @option{-mno-sum-in-toc} forces GCC to
|
|
generate code to calculate the sum of an address and a constant at
|
|
run-time instead of putting that sum into the TOC@. You may specify one
|
|
or both of these options. Each causes GCC to produce very slightly
|
|
slower and larger code at the expense of conserving TOC space.
|
|
|
|
If you still run out of space in the TOC even when you specify both of
|
|
these options, specify @option{-mminimal-toc} instead. This option causes
|
|
GCC to make only one TOC entry for every file. When you specify this
|
|
option, GCC will produce code that is slower and larger but which
|
|
uses extremely little TOC space. You may wish to use this option
|
|
only on files that contain less frequently executed code.
|
|
|
|
@item -maix64
|
|
@itemx -maix32
|
|
@opindex maix64
|
|
@opindex maix32
|
|
Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit
|
|
@code{long} type, and the infrastructure needed to support them.
|
|
Specifying @option{-maix64} implies @option{-mpowerpc64} and
|
|
@option{-mpowerpc}, while @option{-maix32} disables the 64-bit ABI and
|
|
implies @option{-mno-powerpc64}. GCC defaults to @option{-maix32}.
|
|
|
|
@item -mxl-call
|
|
@itemx -mno-xl-call
|
|
@opindex mxl-call
|
|
@opindex mno-xl-call
|
|
On AIX, pass floating-point arguments to prototyped functions beyond the
|
|
register save area (RSA) on the stack in addition to argument FPRs. The
|
|
AIX calling convention was extended but not initially documented to
|
|
handle an obscure K&R C case of calling a function that takes the
|
|
address of its arguments with fewer arguments than declared. AIX XL
|
|
compilers access floating point arguments which do not fit in the
|
|
RSA from the stack when a subroutine is compiled without
|
|
optimization. Because always storing floating-point arguments on the
|
|
stack is inefficient and rarely needed, this option is not enabled by
|
|
default and only is necessary when calling subroutines compiled by AIX
|
|
XL compilers without optimization.
|
|
|
|
@item -mpe
|
|
@opindex mpe
|
|
Support @dfn{IBM RS/6000 SP} @dfn{Parallel Environment} (PE)@. Link an
|
|
application written to use message passing with special startup code to
|
|
enable the application to run. The system must have PE installed in the
|
|
standard location (@file{/usr/lpp/ppe.poe/}), or the @file{specs} file
|
|
must be overridden with the @option{-specs=} option to specify the
|
|
appropriate directory location. The Parallel Environment does not
|
|
support threads, so the @option{-mpe} option and the @option{-pthread}
|
|
option are incompatible.
|
|
|
|
@item -msoft-float
|
|
@itemx -mhard-float
|
|
@opindex msoft-float
|
|
@opindex mhard-float
|
|
Generate code that does not use (uses) the floating-point register set.
|
|
Software floating point emulation is provided if you use the
|
|
@option{-msoft-float} option, and pass the option to GCC when linking.
|
|
|
|
@item -mmultiple
|
|
@itemx -mno-multiple
|
|
@opindex mmultiple
|
|
@opindex mno-multiple
|
|
Generate code that uses (does not use) the load multiple word
|
|
instructions and the store multiple word instructions. These
|
|
instructions are generated by default on POWER systems, and not
|
|
generated on PowerPC systems. Do not use @option{-mmultiple} on little
|
|
endian PowerPC systems, since those instructions do not work when the
|
|
processor is in little endian mode. The exceptions are PPC740 and
|
|
PPC750 which permit the instructions usage in little endian mode.
|
|
|
|
@item -mstring
|
|
@itemx -mno-string
|
|
@opindex mstring
|
|
@opindex mno-string
|
|
Generate code that uses (does not use) the load string instructions
|
|
and the store string word instructions to save multiple registers and
|
|
do small block moves. These instructions are generated by default on
|
|
POWER systems, and not generated on PowerPC systems. Do not use
|
|
@option{-mstring} on little endian PowerPC systems, since those
|
|
instructions do not work when the processor is in little endian mode.
|
|
The exceptions are PPC740 and PPC750 which permit the instructions
|
|
usage in little endian mode.
|
|
|
|
@item -mupdate
|
|
@itemx -mno-update
|
|
@opindex mupdate
|
|
@opindex mno-update
|
|
Generate code that uses (does not use) the load or store instructions
|
|
that update the base register to the address of the calculated memory
|
|
location. These instructions are generated by default. If you use
|
|
@option{-mno-update}, there is a small window between the time that the
|
|
stack pointer is updated and the address of the previous frame is
|
|
stored, which means code that walks the stack frame across interrupts or
|
|
signals may get corrupted data.
|
|
|
|
@item -mfused-madd
|
|
@itemx -mno-fused-madd
|
|
@opindex mfused-madd
|
|
@opindex mno-fused-madd
|
|
Generate code that uses (does not use) the floating point multiply and
|
|
accumulate instructions. These instructions are generated by default if
|
|
hardware floating is used.
|
|
|
|
@item -mno-bit-align
|
|
@itemx -mbit-align
|
|
@opindex mno-bit-align
|
|
@opindex mbit-align
|
|
On System V.4 and embedded PowerPC systems do not (do) force structures
|
|
and unions that contain bit-fields to be aligned to the base type of the
|
|
bit-field.
|
|
|
|
For example, by default a structure containing nothing but 8
|
|
@code{unsigned} bit-fields of length 1 would be aligned to a 4 byte
|
|
boundary and have a size of 4 bytes. By using @option{-mno-bit-align},
|
|
the structure would be aligned to a 1 byte boundary and be one byte in
|
|
size.
|
|
|
|
@item -mno-strict-align
|
|
@itemx -mstrict-align
|
|
@opindex mno-strict-align
|
|
@opindex mstrict-align
|
|
On System V.4 and embedded PowerPC systems do not (do) assume that
|
|
unaligned memory references will be handled by the system.
|
|
|
|
@item -mrelocatable
|
|
@itemx -mno-relocatable
|
|
@opindex mrelocatable
|
|
@opindex mno-relocatable
|
|
On embedded PowerPC systems generate code that allows (does not allow)
|
|
the program to be relocated to a different address at runtime. If you
|
|
use @option{-mrelocatable} on any module, all objects linked together must
|
|
be compiled with @option{-mrelocatable} or @option{-mrelocatable-lib}.
|
|
|
|
@item -mrelocatable-lib
|
|
@itemx -mno-relocatable-lib
|
|
@opindex mrelocatable-lib
|
|
@opindex mno-relocatable-lib
|
|
On embedded PowerPC systems generate code that allows (does not allow)
|
|
the program to be relocated to a different address at runtime. Modules
|
|
compiled with @option{-mrelocatable-lib} can be linked with either modules
|
|
compiled without @option{-mrelocatable} and @option{-mrelocatable-lib} or
|
|
with modules compiled with the @option{-mrelocatable} options.
|
|
|
|
@item -mno-toc
|
|
@itemx -mtoc
|
|
@opindex mno-toc
|
|
@opindex mtoc
|
|
On System V.4 and embedded PowerPC systems do not (do) assume that
|
|
register 2 contains a pointer to a global area pointing to the addresses
|
|
used in the program.
|
|
|
|
@item -mlittle
|
|
@itemx -mlittle-endian
|
|
@opindex mlittle
|
|
@opindex mlittle-endian
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
|
processor in little endian mode. The @option{-mlittle-endian} option is
|
|
the same as @option{-mlittle}.
|
|
|
|
@item -mbig
|
|
@itemx -mbig-endian
|
|
@opindex mbig
|
|
@opindex mbig-endian
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
|
processor in big endian mode. The @option{-mbig-endian} option is
|
|
the same as @option{-mbig}.
|
|
|
|
@item -mcall-sysv
|
|
@opindex mcall-sysv
|
|
On System V.4 and embedded PowerPC systems compile code using calling
|
|
conventions that adheres to the March 1995 draft of the System V
|
|
Application Binary Interface, PowerPC processor supplement. This is the
|
|
default unless you configured GCC using @samp{powerpc-*-eabiaix}.
|
|
|
|
@item -mcall-sysv-eabi
|
|
@opindex mcall-sysv-eabi
|
|
Specify both @option{-mcall-sysv} and @option{-meabi} options.
|
|
|
|
@item -mcall-sysv-noeabi
|
|
@opindex mcall-sysv-noeabi
|
|
Specify both @option{-mcall-sysv} and @option{-mno-eabi} options.
|
|
|
|
@item -mcall-aix
|
|
@opindex mcall-aix
|
|
On System V.4 and embedded PowerPC systems compile code using calling
|
|
conventions that are similar to those used on AIX@. This is the
|
|
default if you configured GCC using @samp{powerpc-*-eabiaix}.
|
|
|
|
@item -mcall-solaris
|
|
@opindex mcall-solaris
|
|
On System V.4 and embedded PowerPC systems compile code for the Solaris
|
|
operating system.
|
|
|
|
@item -mcall-linux
|
|
@opindex mcall-linux
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
|
Linux-based GNU system.
|
|
|
|
@item -mcall-gnu
|
|
@opindex mcall-gnu
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
|
Hurd-based GNU system.
|
|
|
|
@item -mcall-netbsd
|
|
@opindex mcall-netbsd
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
|
NetBSD operating system.
|
|
|
|
@item -maix-struct-return
|
|
@opindex maix-struct-return
|
|
Return all structures in memory (as specified by the AIX ABI)@.
|
|
|
|
@item -msvr4-struct-return
|
|
@opindex msvr4-struct-return
|
|
Return structures smaller than 8 bytes in registers (as specified by the
|
|
SVR4 ABI)@.
|
|
|
|
@item -mabi=altivec
|
|
@opindex mabi=altivec
|
|
Extend the current ABI with AltiVec ABI extensions. This does not
|
|
change the default ABI, instead it adds the AltiVec ABI extensions to
|
|
the current ABI@.
|
|
|
|
@item -mprototype
|
|
@itemx -mno-prototype
|
|
@opindex mprototype
|
|
@opindex mno-prototype
|
|
On System V.4 and embedded PowerPC systems assume that all calls to
|
|
variable argument functions are properly prototyped. Otherwise, the
|
|
compiler must insert an instruction before every non prototyped call to
|
|
set or clear bit 6 of the condition code register (@var{CR}) to
|
|
indicate whether floating point values were passed in the floating point
|
|
registers in case the function takes a variable arguments. With
|
|
@option{-mprototype}, only calls to prototyped variable argument functions
|
|
will set or clear the bit.
|
|
|
|
@item -msim
|
|
@opindex msim
|
|
On embedded PowerPC systems, assume that the startup module is called
|
|
@file{sim-crt0.o} and that the standard C libraries are @file{libsim.a} and
|
|
@file{libc.a}. This is the default for @samp{powerpc-*-eabisim}.
|
|
configurations.
|
|
|
|
@item -mmvme
|
|
@opindex mmvme
|
|
On embedded PowerPC systems, assume that the startup module is called
|
|
@file{crt0.o} and the standard C libraries are @file{libmvme.a} and
|
|
@file{libc.a}.
|
|
|
|
@item -mads
|
|
@opindex mads
|
|
On embedded PowerPC systems, assume that the startup module is called
|
|
@file{crt0.o} and the standard C libraries are @file{libads.a} and
|
|
@file{libc.a}.
|
|
|
|
@item -myellowknife
|
|
@opindex myellowknife
|
|
On embedded PowerPC systems, assume that the startup module is called
|
|
@file{crt0.o} and the standard C libraries are @file{libyk.a} and
|
|
@file{libc.a}.
|
|
|
|
@item -mvxworks
|
|
@opindex mvxworks
|
|
On System V.4 and embedded PowerPC systems, specify that you are
|
|
compiling for a VxWorks system.
|
|
|
|
@item -memb
|
|
@opindex memb
|
|
On embedded PowerPC systems, set the @var{PPC_EMB} bit in the ELF flags
|
|
header to indicate that @samp{eabi} extended relocations are used.
|
|
|
|
@item -meabi
|
|
@itemx -mno-eabi
|
|
@opindex meabi
|
|
@opindex mno-eabi
|
|
On System V.4 and embedded PowerPC systems do (do not) adhere to the
|
|
Embedded Applications Binary Interface (eabi) which is a set of
|
|
modifications to the System V.4 specifications. Selecting @option{-meabi}
|
|
means that the stack is aligned to an 8 byte boundary, a function
|
|
@code{__eabi} is called to from @code{main} to set up the eabi
|
|
environment, and the @option{-msdata} option can use both @code{r2} and
|
|
@code{r13} to point to two separate small data areas. Selecting
|
|
@option{-mno-eabi} means that the stack is aligned to a 16 byte boundary,
|
|
do not call an initialization function from @code{main}, and the
|
|
@option{-msdata} option will only use @code{r13} to point to a single
|
|
small data area. The @option{-meabi} option is on by default if you
|
|
configured GCC using one of the @samp{powerpc*-*-eabi*} options.
|
|
|
|
@item -msdata=eabi
|
|
@opindex msdata=eabi
|
|
On System V.4 and embedded PowerPC systems, put small initialized
|
|
@code{const} global and static data in the @samp{.sdata2} section, which
|
|
is pointed to by register @code{r2}. Put small initialized
|
|
non-@code{const} global and static data in the @samp{.sdata} section,
|
|
which is pointed to by register @code{r13}. Put small uninitialized
|
|
global and static data in the @samp{.sbss} section, which is adjacent to
|
|
the @samp{.sdata} section. The @option{-msdata=eabi} option is
|
|
incompatible with the @option{-mrelocatable} option. The
|
|
@option{-msdata=eabi} option also sets the @option{-memb} option.
|
|
|
|
@item -msdata=sysv
|
|
@opindex msdata=sysv
|
|
On System V.4 and embedded PowerPC systems, put small global and static
|
|
data in the @samp{.sdata} section, which is pointed to by register
|
|
@code{r13}. Put small uninitialized global and static data in the
|
|
@samp{.sbss} section, which is adjacent to the @samp{.sdata} section.
|
|
The @option{-msdata=sysv} option is incompatible with the
|
|
@option{-mrelocatable} option.
|
|
|
|
@item -msdata=default
|
|
@itemx -msdata
|
|
@opindex msdata=default
|
|
@opindex msdata
|
|
On System V.4 and embedded PowerPC systems, if @option{-meabi} is used,
|
|
compile code the same as @option{-msdata=eabi}, otherwise compile code the
|
|
same as @option{-msdata=sysv}.
|
|
|
|
@item -msdata-data
|
|
@opindex msdata-data
|
|
On System V.4 and embedded PowerPC systems, put small global and static
|
|
data in the @samp{.sdata} section. Put small uninitialized global and
|
|
static data in the @samp{.sbss} section. Do not use register @code{r13}
|
|
to address small data however. This is the default behavior unless
|
|
other @option{-msdata} options are used.
|
|
|
|
@item -msdata=none
|
|
@itemx -mno-sdata
|
|
@opindex msdata=none
|
|
@opindex mno-sdata
|
|
On embedded PowerPC systems, put all initialized global and static data
|
|
in the @samp{.data} section, and all uninitialized data in the
|
|
@samp{.bss} section.
|
|
|
|
@item -G @var{num}
|
|
@opindex G
|
|
@cindex smaller data references (PowerPC)
|
|
@cindex .sdata/.sdata2 references (PowerPC)
|
|
On embedded PowerPC systems, put global and static items less than or
|
|
equal to @var{num} bytes into the small data or bss sections instead of
|
|
the normal data or bss section. By default, @var{num} is 8. The
|
|
@option{-G @var{num}} switch is also passed to the linker.
|
|
All modules should be compiled with the same @option{-G @var{num}} value.
|
|
|
|
@item -mregnames
|
|
@itemx -mno-regnames
|
|
@opindex mregnames
|
|
@opindex mno-regnames
|
|
On System V.4 and embedded PowerPC systems do (do not) emit register
|
|
names in the assembly language output using symbolic forms.
|
|
|
|
@item -pthread
|
|
@opindex pthread
|
|
Adds support for multithreading with the @dfn{pthreads} library.
|
|
This option sets flags for both the preprocessor and linker.
|
|
|
|
@end table
|
|
|
|
@node RT Options
|
|
@subsection IBM RT Options
|
|
@cindex RT options
|
|
@cindex IBM RT options
|
|
|
|
These @samp{-m} options are defined for the IBM RT PC:
|
|
|
|
@table @gcctabopt
|
|
@item -min-line-mul
|
|
@opindex min-line-mul
|
|
Use an in-line code sequence for integer multiplies. This is the
|
|
default.
|
|
|
|
@item -mcall-lib-mul
|
|
@opindex mcall-lib-mul
|
|
Call @code{lmul$$} for integer multiples.
|
|
|
|
@item -mfull-fp-blocks
|
|
@opindex mfull-fp-blocks
|
|
Generate full-size floating point data blocks, including the minimum
|
|
amount of scratch space recommended by IBM@. This is the default.
|
|
|
|
@item -mminimum-fp-blocks
|
|
@opindex mminimum-fp-blocks
|
|
Do not include extra scratch space in floating point data blocks. This
|
|
results in smaller code, but slower execution, since scratch space must
|
|
be allocated dynamically.
|
|
|
|
@cindex @file{varargs.h} and RT PC
|
|
@cindex @file{stdarg.h} and RT PC
|
|
@item -mfp-arg-in-fpregs
|
|
@opindex mfp-arg-in-fpregs
|
|
Use a calling sequence incompatible with the IBM calling convention in
|
|
which floating point arguments are passed in floating point registers.
|
|
Note that @code{varargs.h} and @code{stdarg.h} will not work with
|
|
floating point operands if this option is specified.
|
|
|
|
@item -mfp-arg-in-gregs
|
|
@opindex mfp-arg-in-gregs
|
|
Use the normal calling convention for floating point arguments. This is
|
|
the default.
|
|
|
|
@item -mhc-struct-return
|
|
@opindex mhc-struct-return
|
|
Return structures of more than one word in memory, rather than in a
|
|
register. This provides compatibility with the MetaWare HighC (hc)
|
|
compiler. Use the option @option{-fpcc-struct-return} for compatibility
|
|
with the Portable C Compiler (pcc).
|
|
|
|
@item -mnohc-struct-return
|
|
@opindex mnohc-struct-return
|
|
Return some structures of more than one word in registers, when
|
|
convenient. This is the default. For compatibility with the
|
|
IBM-supplied compilers, use the option @option{-fpcc-struct-return} or the
|
|
option @option{-mhc-struct-return}.
|
|
@end table
|
|
|
|
@node MIPS Options
|
|
@subsection MIPS Options
|
|
@cindex MIPS options
|
|
|
|
These @samp{-m} options are defined for the MIPS family of computers:
|
|
|
|
@table @gcctabopt
|
|
|
|
@item -march=@var{cpu-type}
|
|
@opindex march
|
|
Assume the defaults for the machine type @var{cpu-type} when generating
|
|
instructions. The choices for @var{cpu-type} are @samp{r2000}, @samp{r3000},
|
|
@samp{r3900}, @samp{r4000}, @samp{r4100}, @samp{r4300}, @samp{r4400},
|
|
@samp{r4600}, @samp{r4650}, @samp{r5000}, @samp{r6000}, @samp{r8000},
|
|
and @samp{orion}. Additionally, the @samp{r2000}, @samp{r3000},
|
|
@samp{r4000}, @samp{r5000}, and @samp{r6000} can be abbreviated as
|
|
@samp{r2k} (or @samp{r2K}), @samp{r3k}, etc.
|
|
|
|
@item -mtune=@var{cpu-type}
|
|
@opindex mtune
|
|
Assume the defaults for the machine type @var{cpu-type} when scheduling
|
|
instructions. The choices for @var{cpu-type} are @samp{r2000}, @samp{r3000},
|
|
@samp{r3900}, @samp{r4000}, @samp{r4100}, @samp{r4300}, @samp{r4400},
|
|
@samp{r4600}, @samp{r4650}, @samp{r5000}, @samp{r6000}, @samp{r8000},
|
|
and @samp{orion}. Additionally, the @samp{r2000}, @samp{r3000},
|
|
@samp{r4000}, @samp{r5000}, and @samp{r6000} can be abbreviated as
|
|
@samp{r2k} (or @samp{r2K}), @samp{r3k}, etc. While picking a specific
|
|
@var{cpu-type} will schedule things appropriately for that particular
|
|
chip, the compiler will not generate any code that does not meet level 1
|
|
of the MIPS ISA (instruction set architecture) without a @option{-mipsX}
|
|
or @option{-mabi} switch being used.
|
|
|
|
@item -mcpu=@var{cpu-type}
|
|
@opindex mcpu
|
|
This is identical to specifying both @option{-march} and @option{-mtune}.
|
|
|
|
@item -mips1
|
|
@opindex mips1
|
|
Issue instructions from level 1 of the MIPS ISA@. This is the default.
|
|
@samp{r3000} is the default @var{cpu-type} at this ISA level.
|
|
|
|
@item -mips2
|
|
@opindex mips2
|
|
Issue instructions from level 2 of the MIPS ISA (branch likely, square
|
|
root instructions). @samp{r6000} is the default @var{cpu-type} at this
|
|
ISA level.
|
|
|
|
@item -mips3
|
|
@opindex mips3
|
|
Issue instructions from level 3 of the MIPS ISA (64-bit instructions).
|
|
@samp{r4000} is the default @var{cpu-type} at this ISA level.
|
|
|
|
@item -mips4
|
|
@opindex mips4
|
|
Issue instructions from level 4 of the MIPS ISA (conditional move,
|
|
prefetch, enhanced FPU instructions). @samp{r8000} is the default
|
|
@var{cpu-type} at this ISA level.
|
|
|
|
@item -mfp32
|
|
@opindex mfp32
|
|
Assume that 32 32-bit floating point registers are available. This is
|
|
the default.
|
|
|
|
@item -mfp64
|
|
@opindex mfp64
|
|
Assume that 32 64-bit floating point registers are available. This is
|
|
the default when the @option{-mips3} option is used.
|
|
|
|
@item -mfused-madd
|
|
@itemx -mno-fused-madd
|
|
@opindex mfused-madd
|
|
@opindex mno-fused-madd
|
|
Generate code that uses (does not use) the floating point multiply and
|
|
accumulate instructions, when they are available. These instructions
|
|
are generated by default if they are available, but this may be
|
|
undesirable if the extra precision causes problems or on certain chips
|
|
in the mode where denormals are rounded to zero where denormals
|
|
generated by multiply and accumulate instructions cause exceptions
|
|
anyway.
|
|
|
|
@item -mgp32
|
|
@opindex mgp32
|
|
Assume that 32 32-bit general purpose registers are available. This is
|
|
the default.
|
|
|
|
@item -mgp64
|
|
@opindex mgp64
|
|
Assume that 32 64-bit general purpose registers are available. This is
|
|
the default when the @option{-mips3} option is used.
|
|
|
|
@item -mint64
|
|
@opindex mint64
|
|
Force int and long types to be 64 bits wide. See @option{-mlong32} for an
|
|
explanation of the default, and the width of pointers.
|
|
|
|
@item -mlong64
|
|
@opindex mlong64
|
|
Force long types to be 64 bits wide. See @option{-mlong32} for an
|
|
explanation of the default, and the width of pointers.
|
|
|
|
@item -mlong32
|
|
@opindex mlong32
|
|
Force long, int, and pointer types to be 32 bits wide.
|
|
|
|
If none of @option{-mlong32}, @option{-mlong64}, or @option{-mint64} are set,
|
|
the size of ints, longs, and pointers depends on the ABI and ISA chosen.
|
|
For @option{-mabi=32}, and @option{-mabi=n32}, ints and longs are 32 bits
|
|
wide. For @option{-mabi=64}, ints are 32 bits, and longs are 64 bits wide.
|
|
For @option{-mabi=eabi} and either @option{-mips1} or @option{-mips2}, ints
|
|
and longs are 32 bits wide. For @option{-mabi=eabi} and higher ISAs, ints
|
|
are 32 bits, and longs are 64 bits wide. The width of pointer types is
|
|
the smaller of the width of longs or the width of general purpose
|
|
registers (which in turn depends on the ISA)@.
|
|
|
|
@item -mabi=32
|
|
@itemx -mabi=o64
|
|
@itemx -mabi=n32
|
|
@itemx -mabi=64
|
|
@itemx -mabi=eabi
|
|
@opindex mabi=32
|
|
@opindex mabi=o64
|
|
@opindex mabi=n32
|
|
@opindex mabi=64
|
|
@opindex mabi=eabi
|
|
Generate code for the indicated ABI@. The default instruction level is
|
|
@option{-mips1} for @samp{32}, @option{-mips3} for @samp{n32}, and
|
|
@option{-mips4} otherwise. Conversely, with @option{-mips1} or
|
|
@option{-mips2}, the default ABI is @samp{32}; otherwise, the default ABI
|
|
is @samp{64}.
|
|
|
|
@item -mmips-as
|
|
@opindex mmips-as
|
|
Generate code for the MIPS assembler, and invoke @file{mips-tfile} to
|
|
add normal debug information. This is the default for all
|
|
platforms except for the OSF/1 reference platform, using the OSF/rose
|
|
object format. If the either of the @option{-gstabs} or @option{-gstabs+}
|
|
switches are used, the @file{mips-tfile} program will encapsulate the
|
|
stabs within MIPS ECOFF@.
|
|
|
|
@item -mgas
|
|
@opindex mgas
|
|
Generate code for the GNU assembler. This is the default on the OSF/1
|
|
reference platform, using the OSF/rose object format. Also, this is
|
|
the default if the configure option @option{--with-gnu-as} is used.
|
|
|
|
@item -msplit-addresses
|
|
@itemx -mno-split-addresses
|
|
@opindex msplit-addresses
|
|
@opindex mno-split-addresses
|
|
Generate code to load the high and low parts of address constants separately.
|
|
This allows GCC to optimize away redundant loads of the high order
|
|
bits of addresses. This optimization requires GNU as and GNU ld.
|
|
This optimization is enabled by default for some embedded targets where
|
|
GNU as and GNU ld are standard.
|
|
|
|
@item -mrnames
|
|
@itemx -mno-rnames
|
|
@opindex mrnames
|
|
@opindex mno-rnames
|
|
The @option{-mrnames} switch says to output code using the MIPS software
|
|
names for the registers, instead of the hardware names (ie, @var{a0}
|
|
instead of @var{$4}). The only known assembler that supports this option
|
|
is the Algorithmics assembler.
|
|
|
|
@item -mgpopt
|
|
@itemx -mno-gpopt
|
|
@opindex mgpopt
|
|
@opindex mno-gpopt
|
|
The @option{-mgpopt} switch says to write all of the data declarations
|
|
before the instructions in the text section, this allows the MIPS
|
|
assembler to generate one word memory references instead of using two
|
|
words for short global or static data items. This is on by default if
|
|
optimization is selected.
|
|
|
|
@item -mstats
|
|
@itemx -mno-stats
|
|
@opindex mstats
|
|
@opindex mno-stats
|
|
For each non-inline function processed, the @option{-mstats} switch
|
|
causes the compiler to emit one line to the standard error file to
|
|
print statistics about the program (number of registers saved, stack
|
|
size, etc.).
|
|
|
|
@item -mmemcpy
|
|
@itemx -mno-memcpy
|
|
@opindex mmemcpy
|
|
@opindex mno-memcpy
|
|
The @option{-mmemcpy} switch makes all block moves call the appropriate
|
|
string function (@samp{memcpy} or @samp{bcopy}) instead of possibly
|
|
generating inline code.
|
|
|
|
@item -mmips-tfile
|
|
@itemx -mno-mips-tfile
|
|
@opindex mmips-tfile
|
|
@opindex mno-mips-tfile
|
|
The @option{-mno-mips-tfile} switch causes the compiler not
|
|
postprocess the object file with the @file{mips-tfile} program,
|
|
after the MIPS assembler has generated it to add debug support. If
|
|
@file{mips-tfile} is not run, then no local variables will be
|
|
available to the debugger. In addition, @file{stage2} and
|
|
@file{stage3} objects will have the temporary file names passed to the
|
|
assembler embedded in the object file, which means the objects will
|
|
not compare the same. The @option{-mno-mips-tfile} switch should only
|
|
be used when there are bugs in the @file{mips-tfile} program that
|
|
prevents compilation.
|
|
|
|
@item -msoft-float
|
|
@opindex msoft-float
|
|
Generate output containing library calls for floating point.
|
|
@strong{Warning:} the requisite libraries are not part of GCC@.
|
|
Normally the facilities of the machine's usual C compiler are used, but
|
|
this can't be done directly in cross-compilation. You must make your
|
|
own arrangements to provide suitable library functions for
|
|
cross-compilation.
|
|
|
|
@item -mhard-float
|
|
@opindex mhard-float
|
|
Generate output containing floating point instructions. This is the
|
|
default if you use the unmodified sources.
|
|
|
|
@item -mabicalls
|
|
@itemx -mno-abicalls
|
|
@opindex mabicalls
|
|
@opindex mno-abicalls
|
|
Emit (or do not emit) the pseudo operations @samp{.abicalls},
|
|
@samp{.cpload}, and @samp{.cprestore} that some System V.4 ports use for
|
|
position independent code.
|
|
|
|
@item -mlong-calls
|
|
@itemx -mno-long-calls
|
|
@opindex mlong-calls
|
|
@opindex mno-long-calls
|
|
Do all calls with the @samp{JALR} instruction, which requires
|
|
loading up a function's address into a register before the call.
|
|
You need to use this switch, if you call outside of the current
|
|
512 megabyte segment to functions that are not through pointers.
|
|
|
|
@item -mhalf-pic
|
|
@itemx -mno-half-pic
|
|
@opindex mhalf-pic
|
|
@opindex mno-half-pic
|
|
Put pointers to extern references into the data section and load them
|
|
up, rather than put the references in the text section.
|
|
|
|
@item -membedded-pic
|
|
@itemx -mno-embedded-pic
|
|
@opindex membedded-pic
|
|
@opindex mno-embedded-pic
|
|
Generate PIC code suitable for some embedded systems. All calls are
|
|
made using PC relative address, and all data is addressed using the $gp
|
|
register. No more than 65536 bytes of global data may be used. This
|
|
requires GNU as and GNU ld which do most of the work. This currently
|
|
only works on targets which use ECOFF; it does not work with ELF@.
|
|
|
|
@item -membedded-data
|
|
@itemx -mno-embedded-data
|
|
@opindex membedded-data
|
|
@opindex mno-embedded-data
|
|
Allocate variables to the read-only data section first if possible, then
|
|
next in the small data section if possible, otherwise in data. This gives
|
|
slightly slower code than the default, but reduces the amount of RAM required
|
|
when executing, and thus may be preferred for some embedded systems.
|
|
|
|
@item -muninit-const-in-rodata
|
|
@itemx -mno-uninit-const-in-rodata
|
|
@opindex muninit-const-in-rodata
|
|
@opindex mno-uninit-const-in-rodata
|
|
When used together with @option{-membedded-data}, it will always store uninitialized
|
|
const variables in the read-only data section.
|
|
|
|
@item -msingle-float
|
|
@itemx -mdouble-float
|
|
@opindex msingle-float
|
|
@opindex mdouble-float
|
|
The @option{-msingle-float} switch tells gcc to assume that the floating
|
|
point coprocessor only supports single precision operations, as on the
|
|
@samp{r4650} chip. The @option{-mdouble-float} switch permits gcc to use
|
|
double precision operations. This is the default.
|
|
|
|
@item -mmad
|
|
@itemx -mno-mad
|
|
@opindex mmad
|
|
@opindex mno-mad
|
|
Permit use of the @samp{mad}, @samp{madu} and @samp{mul} instructions,
|
|
as on the @samp{r4650} chip.
|
|
|
|
@item -m4650
|
|
@opindex m4650
|
|
Turns on @option{-msingle-float}, @option{-mmad}, and, at least for now,
|
|
@option{-mcpu=r4650}.
|
|
|
|
@item -mips16
|
|
@itemx -mno-mips16
|
|
@opindex mips16
|
|
@opindex mno-mips16
|
|
Enable 16-bit instructions.
|
|
|
|
@item -mentry
|
|
@opindex mentry
|
|
Use the entry and exit pseudo ops. This option can only be used with
|
|
@option{-mips16}.
|
|
|
|
@item -EL
|
|
@opindex EL
|
|
Compile code for the processor in little endian mode.
|
|
The requisite libraries are assumed to exist.
|
|
|
|
@item -EB
|
|
@opindex EB
|
|
Compile code for the processor in big endian mode.
|
|
The requisite libraries are assumed to exist.
|
|
|
|
@item -G @var{num}
|
|
@opindex G
|
|
@cindex smaller data references (MIPS)
|
|
@cindex gp-relative references (MIPS)
|
|
Put global and static items less than or equal to @var{num} bytes into
|
|
the small data or bss sections instead of the normal data or bss
|
|
section. This allows the assembler to emit one word memory reference
|
|
instructions based on the global pointer (@var{gp} or @var{$28}),
|
|
instead of the normal two words used. By default, @var{num} is 8 when
|
|
the MIPS assembler is used, and 0 when the GNU assembler is used. The
|
|
@option{-G @var{num}} switch is also passed to the assembler and linker.
|
|
All modules should be compiled with the same @option{-G @var{num}}
|
|
value.
|
|
|
|
@item -nocpp
|
|
@opindex nocpp
|
|
Tell the MIPS assembler to not run its preprocessor over user
|
|
assembler files (with a @samp{.s} suffix) when assembling them.
|
|
|
|
@item -mfix7000
|
|
@opindex mfix7000
|
|
Pass an option to gas which will cause nops to be inserted if
|
|
the read of the destination register of an mfhi or mflo instruction
|
|
occurs in the following two instructions.
|
|
|
|
@item -no-crt0
|
|
@opindex no-crt0
|
|
Do not include the default crt0.
|
|
|
|
@item -mflush-func=@var{func}
|
|
@itemx -mno-flush-func
|
|
@opindex mflush-func
|
|
Specifies the function to call to flush the I and D caches, or to not
|
|
call any such function. If called, the function must take the same
|
|
arguments as the common @code{_flush_func()}, that is, the address of the
|
|
memory range for which the cache is being flushed, the size of the
|
|
memory range, and the number 3 (to flush both caches). The default
|
|
depends on the target gcc was configured for, but commonly is either
|
|
@samp{_flush_func} or @samp{__cpu_flush}.
|
|
@end table
|
|
|
|
These options are defined by the macro
|
|
@code{TARGET_SWITCHES} in the machine description. The default for the
|
|
options is also defined by that macro, which enables you to change the
|
|
defaults.
|
|
|
|
@node i386 and x86-64 Options
|
|
@subsection Intel 386 and AMD x86-64 Options
|
|
@cindex i386 Options
|
|
@cindex x86-64 Options
|
|
@cindex Intel 386 Options
|
|
@cindex AMD x86-64 Options
|
|
|
|
These @samp{-m} options are defined for the i386 and x86-64 family of
|
|
computers:
|
|
|
|
@table @gcctabopt
|
|
@item -mcpu=@var{cpu-type}
|
|
@opindex mcpu
|
|
Tune to @var{cpu-type} everything applicable about the generated code, except
|
|
for the ABI and the set of available instructions. The choices for
|
|
@var{cpu-type} are @samp{i386}, @samp{i486}, @samp{i586}, @samp{i686},
|
|
@samp{pentium}, @samp{pentium-mmx}, @samp{pentiumpro}, @samp{pentium2},
|
|
@samp{pentium3}, @samp{pentium4}, @samp{k6}, @samp{k6-2}, @samp{k6-3},
|
|
@samp{athlon}, @samp{athlon-tbird}, @samp{athlon-4}, @samp{athlon-xp}
|
|
and @samp{athlon-mp}.
|
|
|
|
While picking a specific @var{cpu-type} will schedule things appropriately
|
|
for that particular chip, the compiler will not generate any code that
|
|
does not run on the i386 without the @option{-march=@var{cpu-type}} option
|
|
being used. @samp{i586} is equivalent to @samp{pentium} and @samp{i686}
|
|
is equivalent to @samp{pentiumpro}. @samp{k6} and @samp{athlon} are the
|
|
AMD chips as opposed to the Intel ones.
|
|
|
|
@item -march=@var{cpu-type}
|
|
@opindex march
|
|
Generate instructions for the machine type @var{cpu-type}. The choices
|
|
for @var{cpu-type} are the same as for @option{-mcpu}. Moreover,
|
|
specifying @option{-march=@var{cpu-type}} implies @option{-mcpu=@var{cpu-type}}.
|
|
|
|
@item -m386
|
|
@itemx -m486
|
|
@itemx -mpentium
|
|
@itemx -mpentiumpro
|
|
@opindex m386
|
|
@opindex m486
|
|
@opindex mpentium
|
|
@opindex mpentiumpro
|
|
These options are synonyms for @option{-mcpu=i386}, @option{-mcpu=i486},
|
|
@option{-mcpu=pentium}, and @option{-mcpu=pentiumpro} respectively.
|
|
These synonyms are deprecated.
|
|
|
|
@item -mfpmath=@var{unit}
|
|
@opindex march
|
|
generate floating point arithmetics for selected unit @var{unit}. the choices
|
|
for @var{unit} are:
|
|
|
|
@table @samp
|
|
@item 387
|
|
Use the standard 387 floating point coprocessor present majority of chips and
|
|
emulated otherwise. Code compiled with this option will run almost everywhere.
|
|
The temporary results are computed in 80bit precesion instead of precision
|
|
specified by the type resulting in slightly different results compared to most
|
|
of other chips. See @option{-ffloat-store} for more detailed description.
|
|
|
|
This is the default choice for i386 compiler.
|
|
|
|
@item sse
|
|
Use scalar floating point instructions present in the SSE instruction set.
|
|
This instruction set is supported by Pentium3 and newer chips, in the AMD line
|
|
by Athlon-4, Athlon-xp and Athlon-mp chips. The earlier version of SSE
|
|
instruction set supports only single precision arithmetics, thus the double and
|
|
extended precision arithmetics is still done using 387. Later version, present
|
|
only in Pentium4 and the future AMD x86-64 chips supports double precision
|
|
arithmetics too.
|
|
|
|
For i387 you need to use @option{-march=@var{cpu-type}}, @option{-msse} or
|
|
@option{-msse2} switches to enable SSE extensions and make this option
|
|
effective. For x86-64 compiler, these extensions are enabled by default.
|
|
|
|
The resulting code should be considerably faster in majority of cases and avoid
|
|
the numerical instability problems of 387 code, but may break some existing
|
|
code that expects temporaries to be 80bit.
|
|
|
|
This is the default choice for x86-64 compiler.
|
|
|
|
@item sse,387
|
|
Attempt to utilize both instruction sets at once. This effectivly double the
|
|
amount of available registers and on chips with separate execution units for
|
|
387 and SSE the execution resources too. Use this option with care, as it is
|
|
still experimental, because gcc register allocator does not model separate
|
|
functional units well resulting in instable performance.
|
|
@end table
|
|
|
|
@item -masm=@var{dialect}
|
|
@opindex masm=@var{dialect}
|
|
Output asm instructions using selected @var{dialect}. Supported choices are
|
|
@samp{intel} or @samp{att} (the default one).
|
|
|
|
@item -mieee-fp
|
|
@itemx -mno-ieee-fp
|
|
@opindex mieee-fp
|
|
@opindex mno-ieee-fp
|
|
Control whether or not the compiler uses IEEE floating point
|
|
comparisons. These handle correctly the case where the result of a
|
|
comparison is unordered.
|
|
|
|
@item -msoft-float
|
|
@opindex msoft-float
|
|
Generate output containing library calls for floating point.
|
|
@strong{Warning:} the requisite libraries are not part of GCC@.
|
|
Normally the facilities of the machine's usual C compiler are used, but
|
|
this can't be done directly in cross-compilation. You must make your
|
|
own arrangements to provide suitable library functions for
|
|
cross-compilation.
|
|
|
|
On machines where a function returns floating point results in the 80387
|
|
register stack, some floating point opcodes may be emitted even if
|
|
@option{-msoft-float} is used.
|
|
|
|
@item -mno-fp-ret-in-387
|
|
@opindex mno-fp-ret-in-387
|
|
Do not use the FPU registers for return values of functions.
|
|
|
|
The usual calling convention has functions return values of types
|
|
@code{float} and @code{double} in an FPU register, even if there
|
|
is no FPU@. The idea is that the operating system should emulate
|
|
an FPU@.
|
|
|
|
The option @option{-mno-fp-ret-in-387} causes such values to be returned
|
|
in ordinary CPU registers instead.
|
|
|
|
@item -mno-fancy-math-387
|
|
@opindex mno-fancy-math-387
|
|
Some 387 emulators do not support the @code{sin}, @code{cos} and
|
|
@code{sqrt} instructions for the 387. Specify this option to avoid
|
|
generating those instructions. This option is the default on FreeBSD@.
|
|
As of revision 2.6.1, these instructions are not generated unless you
|
|
also use the @option{-funsafe-math-optimizations} switch.
|
|
|
|
@item -malign-double
|
|
@itemx -mno-align-double
|
|
@opindex malign-double
|
|
@opindex mno-align-double
|
|
Control whether GCC aligns @code{double}, @code{long double}, and
|
|
@code{long long} variables on a two word boundary or a one word
|
|
boundary. Aligning @code{double} variables on a two word boundary will
|
|
produce code that runs somewhat faster on a @samp{Pentium} at the
|
|
expense of more memory.
|
|
|
|
@item -m128bit-long-double
|
|
@opindex m128bit-long-double
|
|
Control the size of @code{long double} type. i386 application binary interface
|
|
specify the size to be 12 bytes, while modern architectures (Pentium and newer)
|
|
prefer @code{long double} aligned to 8 or 16 byte boundary. This is
|
|
impossible to reach with 12 byte long doubles in the array accesses.
|
|
|
|
@strong{Warning:} if you use the @option{-m128bit-long-double} switch, the
|
|
structures and arrays containing @code{long double} will change their size as
|
|
well as function calling convention for function taking @code{long double}
|
|
will be modified.
|
|
|
|
@item -m96bit-long-double
|
|
@opindex m96bit-long-double
|
|
Set the size of @code{long double} to 96 bits as required by the i386
|
|
application binary interface. This is the default.
|
|
|
|
@item -msvr3-shlib
|
|
@itemx -mno-svr3-shlib
|
|
@opindex msvr3-shlib
|
|
@opindex mno-svr3-shlib
|
|
Control whether GCC places uninitialized local variables into the
|
|
@code{bss} or @code{data} segments. @option{-msvr3-shlib} places them
|
|
into @code{bss}. These options are meaningful only on System V Release 3.
|
|
|
|
@item -mrtd
|
|
@opindex mrtd
|
|
Use a different function-calling convention, in which functions that
|
|
take a fixed number of arguments return with the @code{ret} @var{num}
|
|
instruction, which pops their arguments while returning. This saves one
|
|
instruction in the caller since there is no need to pop the arguments
|
|
there.
|
|
|
|
You can specify that an individual function is called with this calling
|
|
sequence with the function attribute @samp{stdcall}. You can also
|
|
override the @option{-mrtd} option by using the function attribute
|
|
@samp{cdecl}. @xref{Function Attributes}.
|
|
|
|
@strong{Warning:} this calling convention is incompatible with the one
|
|
normally used on Unix, so you cannot use it if you need to call
|
|
libraries compiled with the Unix compiler.
|
|
|
|
Also, you must provide function prototypes for all functions that
|
|
take variable numbers of arguments (including @code{printf});
|
|
otherwise incorrect code will be generated for calls to those
|
|
functions.
|
|
|
|
In addition, seriously incorrect code will result if you call a
|
|
function with too many arguments. (Normally, extra arguments are
|
|
harmlessly ignored.)
|
|
|
|
@item -mregparm=@var{num}
|
|
@opindex mregparm
|
|
Control how many registers are used to pass integer arguments. By
|
|
default, no registers are used to pass arguments, and at most 3
|
|
registers can be used. You can control this behavior for a specific
|
|
function by using the function attribute @samp{regparm}.
|
|
@xref{Function Attributes}.
|
|
|
|
@strong{Warning:} if you use this switch, and
|
|
@var{num} is nonzero, then you must build all modules with the same
|
|
value, including any libraries. This includes the system libraries and
|
|
startup modules.
|
|
|
|
@item -mpreferred-stack-boundary=@var{num}
|
|
@opindex mpreferred-stack-boundary
|
|
Attempt to keep the stack boundary aligned to a 2 raised to @var{num}
|
|
byte boundary. If @option{-mpreferred-stack-boundary} is not specified,
|
|
the default is 4 (16 bytes or 128 bits), except when optimizing for code
|
|
size (@option{-Os}), in which case the default is the minimum correct
|
|
alignment (4 bytes for x86, and 8 bytes for x86-64).
|
|
|
|
On Pentium and PentiumPro, @code{double} and @code{long double} values
|
|
should be aligned to an 8 byte boundary (see @option{-malign-double}) or
|
|
suffer significant run time performance penalties. On Pentium III, the
|
|
Streaming SIMD Extension (SSE) data type @code{__m128} suffers similar
|
|
penalties if it is not 16 byte aligned.
|
|
|
|
To ensure proper alignment of this values on the stack, the stack boundary
|
|
must be as aligned as that required by any value stored on the stack.
|
|
Further, every function must be generated such that it keeps the stack
|
|
aligned. Thus calling a function compiled with a higher preferred
|
|
stack boundary from a function compiled with a lower preferred stack
|
|
boundary will most likely misalign the stack. It is recommended that
|
|
libraries that use callbacks always use the default setting.
|
|
|
|
This extra alignment does consume extra stack space, and generally
|
|
increases code size. Code that is sensitive to stack space usage, such
|
|
as embedded systems and operating system kernels, may want to reduce the
|
|
preferred alignment to @option{-mpreferred-stack-boundary=2}.
|
|
|
|
@item -mmmx
|
|
@itemx -mno-mmx
|
|
@item -msse
|
|
@itemx -mno-sse
|
|
@item -msse2
|
|
@itemx -mno-sse2
|
|
@item -m3dnow
|
|
@itemx -mno-3dnow
|
|
@opindex mmmx
|
|
@opindex mno-mmx
|
|
@opindex msse
|
|
@opindex mno-sse
|
|
@opindex m3dnow
|
|
@opindex mno-3dnow
|
|
These switches enable or disable the use of built-in functions that allow
|
|
direct access to the MMX, SSE and 3Dnow extensions of the instruction set.
|
|
|
|
@xref{X86 Built-in Functions}, for details of the functions enabled
|
|
and disabled by these switches.
|
|
|
|
@item -mpush-args
|
|
@itemx -mno-push-args
|
|
@opindex mpush-args
|
|
@opindex mno-push-args
|
|
Use PUSH operations to store outgoing parameters. This method is shorter
|
|
and usually equally fast as method using SUB/MOV operations and is enabled
|
|
by default. In some cases disabling it may improve performance because of
|
|
improved scheduling and reduced dependencies.
|
|
|
|
@item -maccumulate-outgoing-args
|
|
@opindex maccumulate-outgoing-args
|
|
If enabled, the maximum amount of space required for outgoing arguments will be
|
|
computed in the function prologue. This is faster on most modern CPUs
|
|
because of reduced dependencies, improved scheduling and reduced stack usage
|
|
when preferred stack boundary is not equal to 2. The drawback is a notable
|
|
increase in code size. This switch implies @option{-mno-push-args}.
|
|
|
|
@item -mthreads
|
|
@opindex mthreads
|
|
Support thread-safe exception handling on @samp{Mingw32}. Code that relies
|
|
on thread-safe exception handling must compile and link all code with the
|
|
@option{-mthreads} option. When compiling, @option{-mthreads} defines
|
|
@option{-D_MT}; when linking, it links in a special thread helper library
|
|
@option{-lmingwthrd} which cleans up per thread exception handling data.
|
|
|
|
@item -mno-align-stringops
|
|
@opindex mno-align-stringops
|
|
Do not align destination of inlined string operations. This switch reduces
|
|
code size and improves performance in case the destination is already aligned,
|
|
but gcc don't know about it.
|
|
|
|
@item -minline-all-stringops
|
|
@opindex minline-all-stringops
|
|
By default GCC inlines string operations only when destination is known to be
|
|
aligned at least to 4 byte boundary. This enables more inlining, increase code
|
|
size, but may improve performance of code that depends on fast memcpy, strlen
|
|
and memset for short lengths.
|
|
|
|
@item -momit-leaf-frame-pointer
|
|
@opindex momit-leaf-frame-pointer
|
|
Don't keep the frame pointer in a register for leaf functions. This
|
|
avoids the instructions to save, set up and restore frame pointers and
|
|
makes an extra register available in leaf functions. The option
|
|
@option{-fomit-frame-pointer} removes the frame pointer for all functions
|
|
which might make debugging harder.
|
|
@end table
|
|
|
|
These @samp{-m} switches are supported in addition to the above
|
|
on AMD x86-64 processors in 64-bit environments.
|
|
|
|
@table @gcctabopt
|
|
@item -m32
|
|
@itemx -m64
|
|
@opindex m32
|
|
@opindex m64
|
|
Generate code for a 32-bit or 64-bit environment.
|
|
The 32-bit environment sets int, long and pointer to 32 bits and
|
|
generates code that runs on any i386 system.
|
|
The 64-bit environment sets int to 32 bits and long and pointer
|
|
to 64 bits and generates code for AMD's x86-64 architecture.
|
|
|
|
@item -mno-red-zone
|
|
@opindex no-red-zone
|
|
Do not use a so called red zone for x86-64 code. The red zone is mandated
|
|
by the x86-64 ABI, it is a 128-byte area beyond the location of the
|
|
stack pointer that will not be modified by signal or interrupt handlers
|
|
and therefore can be used for temporary data without adjusting the stack
|
|
pointer. The flag @option{-mno-red-zone} disables this red zone.
|
|
@end table
|
|
|
|
@node HPPA Options
|
|
@subsection HPPA Options
|
|
@cindex HPPA Options
|
|
|
|
These @samp{-m} options are defined for the HPPA family of computers:
|
|
|
|
@table @gcctabopt
|
|
@item -march=@var{architecture-type}
|
|
@opindex march
|
|
Generate code for the specified architecture. The choices for
|
|
@var{architecture-type} are @samp{1.0} for PA 1.0, @samp{1.1} for PA
|
|
1.1, and @samp{2.0} for PA 2.0 processors. Refer to
|
|
@file{/usr/lib/sched.models} on an HP-UX system to determine the proper
|
|
architecture option for your machine. Code compiled for lower numbered
|
|
architectures will run on higher numbered architectures, but not the
|
|
other way around.
|
|
|
|
PA 2.0 support currently requires gas snapshot 19990413 or later. The
|
|
next release of binutils (current is 2.9.1) will probably contain PA 2.0
|
|
support.
|
|
|
|
@item -mpa-risc-1-0
|
|
@itemx -mpa-risc-1-1
|
|
@itemx -mpa-risc-2-0
|
|
@opindex mpa-risc-1-0
|
|
@opindex mpa-risc-1-1
|
|
@opindex mpa-risc-2-0
|
|
Synonyms for @option{-march=1.0}, @option{-march=1.1}, and @option{-march=2.0} respectively.
|
|
|
|
@item -mbig-switch
|
|
@opindex mbig-switch
|
|
Generate code suitable for big switch tables. Use this option only if
|
|
the assembler/linker complain about out of range branches within a switch
|
|
table.
|
|
|
|
@item -mjump-in-delay
|
|
@opindex mjump-in-delay
|
|
Fill delay slots of function calls with unconditional jump instructions
|
|
by modifying the return pointer for the function call to be the target
|
|
of the conditional jump.
|
|
|
|
@item -mdisable-fpregs
|
|
@opindex mdisable-fpregs
|
|
Prevent floating point registers from being used in any manner. This is
|
|
necessary for compiling kernels which perform lazy context switching of
|
|
floating point registers. If you use this option and attempt to perform
|
|
floating point operations, the compiler will abort.
|
|
|
|
@item -mdisable-indexing
|
|
@opindex mdisable-indexing
|
|
Prevent the compiler from using indexing address modes. This avoids some
|
|
rather obscure problems when compiling MIG generated code under MACH@.
|
|
|
|
@item -mno-space-regs
|
|
@opindex mno-space-regs
|
|
Generate code that assumes the target has no space registers. This allows
|
|
GCC to generate faster indirect calls and use unscaled index address modes.
|
|
|
|
Such code is suitable for level 0 PA systems and kernels.
|
|
|
|
@item -mfast-indirect-calls
|
|
@opindex mfast-indirect-calls
|
|
Generate code that assumes calls never cross space boundaries. This
|
|
allows GCC to emit code which performs faster indirect calls.
|
|
|
|
This option will not work in the presence of shared libraries or nested
|
|
functions.
|
|
|
|
@item -mlong-load-store
|
|
@opindex mlong-load-store
|
|
Generate 3-instruction load and store sequences as sometimes required by
|
|
the HP-UX 10 linker. This is equivalent to the @samp{+k} option to
|
|
the HP compilers.
|
|
|
|
@item -mportable-runtime
|
|
@opindex mportable-runtime
|
|
Use the portable calling conventions proposed by HP for ELF systems.
|
|
|
|
@item -mgas
|
|
@opindex mgas
|
|
Enable the use of assembler directives only GAS understands.
|
|
|
|
@item -mschedule=@var{cpu-type}
|
|
@opindex mschedule
|
|
Schedule code according to the constraints for the machine type
|
|
@var{cpu-type}. The choices for @var{cpu-type} are @samp{700}
|
|
@samp{7100}, @samp{7100LC}, @samp{7200}, and @samp{8000}. Refer to
|
|
@file{/usr/lib/sched.models} on an HP-UX system to determine the
|
|
proper scheduling option for your machine.
|
|
|
|
@item -mlinker-opt
|
|
@opindex mlinker-opt
|
|
Enable the optimization pass in the HPUX linker. Note this makes symbolic
|
|
debugging impossible. It also triggers a bug in the HPUX 8 and HPUX 9 linkers
|
|
in which they give bogus error messages when linking some programs.
|
|
|
|
@item -msoft-float
|
|
@opindex msoft-float
|
|
Generate output containing library calls for floating point.
|
|
@strong{Warning:} the requisite libraries are not available for all HPPA
|
|
targets. Normally the facilities of the machine's usual C compiler are
|
|
used, but this cannot be done directly in cross-compilation. You must make
|
|
your own arrangements to provide suitable library functions for
|
|
cross-compilation. The embedded target @samp{hppa1.1-*-pro}
|
|
does provide software floating point support.
|
|
|
|
@option{-msoft-float} changes the calling convention in the output file;
|
|
therefore, it is only useful if you compile @emph{all} of a program with
|
|
this option. In particular, you need to compile @file{libgcc.a}, the
|
|
library that comes with GCC, with @option{-msoft-float} in order for
|
|
this to work.
|
|
@end table
|
|
|
|
@node Intel 960 Options
|
|
@subsection Intel 960 Options
|
|
|
|
These @samp{-m} options are defined for the Intel 960 implementations:
|
|
|
|
@table @gcctabopt
|
|
@item -m@var{cpu-type}
|
|
@opindex mka
|
|
@opindex mkb
|
|
@opindex mmc
|
|
@opindex mca
|
|
@opindex mcf
|
|
@opindex msa
|
|
@opindex msb
|
|
Assume the defaults for the machine type @var{cpu-type} for some of
|
|
the other options, including instruction scheduling, floating point
|
|
support, and addressing modes. The choices for @var{cpu-type} are
|
|
@samp{ka}, @samp{kb}, @samp{mc}, @samp{ca}, @samp{cf},
|
|
@samp{sa}, and @samp{sb}.
|
|
The default is
|
|
@samp{kb}.
|
|
|
|
@item -mnumerics
|
|
@itemx -msoft-float
|
|
@opindex mnumerics
|
|
@opindex msoft-float
|
|
The @option{-mnumerics} option indicates that the processor does support
|
|
floating-point instructions. The @option{-msoft-float} option indicates
|
|
that floating-point support should not be assumed.
|
|
|
|
@item -mleaf-procedures
|
|
@itemx -mno-leaf-procedures
|
|
@opindex mleaf-procedures
|
|
@opindex mno-leaf-procedures
|
|
Do (or do not) attempt to alter leaf procedures to be callable with the
|
|
@code{bal} instruction as well as @code{call}. This will result in more
|
|
efficient code for explicit calls when the @code{bal} instruction can be
|
|
substituted by the assembler or linker, but less efficient code in other
|
|
cases, such as calls via function pointers, or using a linker that doesn't
|
|
support this optimization.
|
|
|
|
@item -mtail-call
|
|
@itemx -mno-tail-call
|
|
@opindex mtail-call
|
|
@opindex mno-tail-call
|
|
Do (or do not) make additional attempts (beyond those of the
|
|
machine-independent portions of the compiler) to optimize tail-recursive
|
|
calls into branches. You may not want to do this because the detection of
|
|
cases where this is not valid is not totally complete. The default is
|
|
@option{-mno-tail-call}.
|
|
|
|
@item -mcomplex-addr
|
|
@itemx -mno-complex-addr
|
|
@opindex mcomplex-addr
|
|
@opindex mno-complex-addr
|
|
Assume (or do not assume) that the use of a complex addressing mode is a
|
|
win on this implementation of the i960. Complex addressing modes may not
|
|
be worthwhile on the K-series, but they definitely are on the C-series.
|
|
The default is currently @option{-mcomplex-addr} for all processors except
|
|
the CB and CC@.
|
|
|
|
@item -mcode-align
|
|
@itemx -mno-code-align
|
|
@opindex mcode-align
|
|
@opindex mno-code-align
|
|
Align code to 8-byte boundaries for faster fetching (or don't bother).
|
|
Currently turned on by default for C-series implementations only.
|
|
|
|
@ignore
|
|
@item -mclean-linkage
|
|
@itemx -mno-clean-linkage
|
|
@opindex mclean-linkage
|
|
@opindex mno-clean-linkage
|
|
These options are not fully implemented.
|
|
@end ignore
|
|
|
|
@item -mic-compat
|
|
@itemx -mic2.0-compat
|
|
@itemx -mic3.0-compat
|
|
@opindex mic-compat
|
|
@opindex mic2.0-compat
|
|
@opindex mic3.0-compat
|
|
Enable compatibility with iC960 v2.0 or v3.0.
|
|
|
|
@item -masm-compat
|
|
@itemx -mintel-asm
|
|
@opindex masm-compat
|
|
@opindex mintel-asm
|
|
Enable compatibility with the iC960 assembler.
|
|
|
|
@item -mstrict-align
|
|
@itemx -mno-strict-align
|
|
@opindex mstrict-align
|
|
@opindex mno-strict-align
|
|
Do not permit (do permit) unaligned accesses.
|
|
|
|
@item -mold-align
|
|
@opindex mold-align
|
|
Enable structure-alignment compatibility with Intel's gcc release version
|
|
1.3 (based on gcc 1.37). This option implies @option{-mstrict-align}.
|
|
|
|
@item -mlong-double-64
|
|
@opindex mlong-double-64
|
|
Implement type @samp{long double} as 64-bit floating point numbers.
|
|
Without the option @samp{long double} is implemented by 80-bit
|
|
floating point numbers. The only reason we have it because there is
|
|
no 128-bit @samp{long double} support in @samp{fp-bit.c} yet. So it
|
|
is only useful for people using soft-float targets. Otherwise, we
|
|
should recommend against use of it.
|
|
|
|
@end table
|
|
|
|
@node DEC Alpha Options
|
|
@subsection DEC Alpha Options
|
|
|
|
These @samp{-m} options are defined for the DEC Alpha implementations:
|
|
|
|
@table @gcctabopt
|
|
@item -mno-soft-float
|
|
@itemx -msoft-float
|
|
@opindex mno-soft-float
|
|
@opindex msoft-float
|
|
Use (do not use) the hardware floating-point instructions for
|
|
floating-point operations. When @option{-msoft-float} is specified,
|
|
functions in @file{libgcc.a} will be used to perform floating-point
|
|
operations. Unless they are replaced by routines that emulate the
|
|
floating-point operations, or compiled in such a way as to call such
|
|
emulations routines, these routines will issue floating-point
|
|
operations. If you are compiling for an Alpha without floating-point
|
|
operations, you must ensure that the library is built so as not to call
|
|
them.
|
|
|
|
Note that Alpha implementations without floating-point operations are
|
|
required to have floating-point registers.
|
|
|
|
@item -mfp-reg
|
|
@itemx -mno-fp-regs
|
|
@opindex mfp-reg
|
|
@opindex mno-fp-regs
|
|
Generate code that uses (does not use) the floating-point register set.
|
|
@option{-mno-fp-regs} implies @option{-msoft-float}. If the floating-point
|
|
register set is not used, floating point operands are passed in integer
|
|
registers as if they were integers and floating-point results are passed
|
|
in @code{$0} instead of @code{$f0}. This is a non-standard calling sequence,
|
|
so any function with a floating-point argument or return value called by code
|
|
compiled with @option{-mno-fp-regs} must also be compiled with that
|
|
option.
|
|
|
|
A typical use of this option is building a kernel that does not use,
|
|
and hence need not save and restore, any floating-point registers.
|
|
|
|
@item -mieee
|
|
@opindex mieee
|
|
The Alpha architecture implements floating-point hardware optimized for
|
|
maximum performance. It is mostly compliant with the IEEE floating
|
|
point standard. However, for full compliance, software assistance is
|
|
required. This option generates code fully IEEE compliant code
|
|
@emph{except} that the @var{inexact-flag} is not maintained (see below).
|
|
If this option is turned on, the preprocessor macro @code{_IEEE_FP} is
|
|
defined during compilation. The resulting code is less efficient but is
|
|
able to correctly support denormalized numbers and exceptional IEEE
|
|
values such as not-a-number and plus/minus infinity. Other Alpha
|
|
compilers call this option @option{-ieee_with_no_inexact}.
|
|
|
|
@item -mieee-with-inexact
|
|
@opindex mieee-with-inexact
|
|
This is like @option{-mieee} except the generated code also maintains
|
|
the IEEE @var{inexact-flag}. Turning on this option causes the
|
|
generated code to implement fully-compliant IEEE math. In addition to
|
|
@code{_IEEE_FP}, @code{_IEEE_FP_EXACT} is defined as a preprocessor
|
|
macro. On some Alpha implementations the resulting code may execute
|
|
significantly slower than the code generated by default. Since there is
|
|
very little code that depends on the @var{inexact-flag}, you should
|
|
normally not specify this option. Other Alpha compilers call this
|
|
option @option{-ieee_with_inexact}.
|
|
|
|
@item -mfp-trap-mode=@var{trap-mode}
|
|
@opindex mfp-trap-mode
|
|
This option controls what floating-point related traps are enabled.
|
|
Other Alpha compilers call this option @option{-fptm @var{trap-mode}}.
|
|
The trap mode can be set to one of four values:
|
|
|
|
@table @samp
|
|
@item n
|
|
This is the default (normal) setting. The only traps that are enabled
|
|
are the ones that cannot be disabled in software (e.g., division by zero
|
|
trap).
|
|
|
|
@item u
|
|
In addition to the traps enabled by @samp{n}, underflow traps are enabled
|
|
as well.
|
|
|
|
@item su
|
|
Like @samp{su}, but the instructions are marked to be safe for software
|
|
completion (see Alpha architecture manual for details).
|
|
|
|
@item sui
|
|
Like @samp{su}, but inexact traps are enabled as well.
|
|
@end table
|
|
|
|
@item -mfp-rounding-mode=@var{rounding-mode}
|
|
@opindex mfp-rounding-mode
|
|
Selects the IEEE rounding mode. Other Alpha compilers call this option
|
|
@option{-fprm @var{rounding-mode}}. The @var{rounding-mode} can be one
|
|
of:
|
|
|
|
@table @samp
|
|
@item n
|
|
Normal IEEE rounding mode. Floating point numbers are rounded towards
|
|
the nearest machine number or towards the even machine number in case
|
|
of a tie.
|
|
|
|
@item m
|
|
Round towards minus infinity.
|
|
|
|
@item c
|
|
Chopped rounding mode. Floating point numbers are rounded towards zero.
|
|
|
|
@item d
|
|
Dynamic rounding mode. A field in the floating point control register
|
|
(@var{fpcr}, see Alpha architecture reference manual) controls the
|
|
rounding mode in effect. The C library initializes this register for
|
|
rounding towards plus infinity. Thus, unless your program modifies the
|
|
@var{fpcr}, @samp{d} corresponds to round towards plus infinity.
|
|
@end table
|
|
|
|
@item -mtrap-precision=@var{trap-precision}
|
|
@opindex mtrap-precision
|
|
In the Alpha architecture, floating point traps are imprecise. This
|
|
means without software assistance it is impossible to recover from a
|
|
floating trap and program execution normally needs to be terminated.
|
|
GCC can generate code that can assist operating system trap handlers
|
|
in determining the exact location that caused a floating point trap.
|
|
Depending on the requirements of an application, different levels of
|
|
precisions can be selected:
|
|
|
|
@table @samp
|
|
@item p
|
|
Program precision. This option is the default and means a trap handler
|
|
can only identify which program caused a floating point exception.
|
|
|
|
@item f
|
|
Function precision. The trap handler can determine the function that
|
|
caused a floating point exception.
|
|
|
|
@item i
|
|
Instruction precision. The trap handler can determine the exact
|
|
instruction that caused a floating point exception.
|
|
@end table
|
|
|
|
Other Alpha compilers provide the equivalent options called
|
|
@option{-scope_safe} and @option{-resumption_safe}.
|
|
|
|
@item -mieee-conformant
|
|
@opindex mieee-conformant
|
|
This option marks the generated code as IEEE conformant. You must not
|
|
use this option unless you also specify @option{-mtrap-precision=i} and either
|
|
@option{-mfp-trap-mode=su} or @option{-mfp-trap-mode=sui}. Its only effect
|
|
is to emit the line @samp{.eflag 48} in the function prologue of the
|
|
generated assembly file. Under DEC Unix, this has the effect that
|
|
IEEE-conformant math library routines will be linked in.
|
|
|
|
@item -mbuild-constants
|
|
@opindex mbuild-constants
|
|
Normally GCC examines a 32- or 64-bit integer constant to
|
|
see if it can construct it from smaller constants in two or three
|
|
instructions. If it cannot, it will output the constant as a literal and
|
|
generate code to load it from the data segment at runtime.
|
|
|
|
Use this option to require GCC to construct @emph{all} integer constants
|
|
using code, even if it takes more instructions (the maximum is six).
|
|
|
|
You would typically use this option to build a shared library dynamic
|
|
loader. Itself a shared library, it must relocate itself in memory
|
|
before it can find the variables and constants in its own data segment.
|
|
|
|
@item -malpha-as
|
|
@itemx -mgas
|
|
@opindex malpha-as
|
|
@opindex mgas
|
|
Select whether to generate code to be assembled by the vendor-supplied
|
|
assembler (@option{-malpha-as}) or by the GNU assembler @option{-mgas}.
|
|
|
|
@item -mbwx
|
|
@itemx -mno-bwx
|
|
@itemx -mcix
|
|
@itemx -mno-cix
|
|
@itemx -mfix
|
|
@itemx -mno-fix
|
|
@itemx -mmax
|
|
@itemx -mno-max
|
|
@opindex mbwx
|
|
@opindex mno-bwx
|
|
@opindex mcix
|
|
@opindex mno-cix
|
|
@opindex mfix
|
|
@opindex mno-fix
|
|
@opindex mmax
|
|
@opindex mno-max
|
|
Indicate whether GCC should generate code to use the optional BWX,
|
|
CIX, FIX and MAX instruction sets. The default is to use the instruction
|
|
sets supported by the CPU type specified via @option{-mcpu=} option or that
|
|
of the CPU on which GCC was built if none was specified.
|
|
|
|
@item -mfloat-vax
|
|
@itemx -mfloat-ieee
|
|
@opindex mfloat-vax
|
|
@opindex mfloat-ieee
|
|
Generate code that uses (does not use) VAX F and G floating point
|
|
arithmetic instead of IEEE single and double precision.
|
|
|
|
@item -mexplicit-relocs
|
|
@itemx -mno-explicit-relocs
|
|
@opindex mexplicit-relocs
|
|
@opindex mno-explicit-relocs
|
|
Older Alpha assemblers provided no way to generate symbol relocations
|
|
except via assembler macros. Use of these macros does not allow
|
|
optimial instruction scheduling. GNU binutils as of version 2.12
|
|
supports a new syntax that allows the compiler to explicitly mark
|
|
which relocations should apply to which instructions. This option
|
|
is mostly useful for debugging, as GCC detects the capabilities of
|
|
the assembler when it is built and sets the default accordingly.
|
|
|
|
@item -msmall-data
|
|
@itemx -mlarge-data
|
|
@opindex msmall-data
|
|
@opindex mlarge-data
|
|
When @option{-mexplicit-relocs} is in effect, static data is
|
|
accessed via @dfn{gp-relative} relocations. When @option{-msmall-data}
|
|
is used, objects 8 bytes long or smaller are placed in a @dfn{small data area}
|
|
(the @code{.sdata} and @code{.sbss} sections) and are accessed via
|
|
16-bit relocations off of the @code{$gp} register. This limits the
|
|
size of the small data area to 64KB, but allows the variables to be
|
|
directly accessed via a single instruction.
|
|
|
|
The default is @option{-mlarge-data}. With this option the data area
|
|
is limited to just below 2GB. Programs that require more than 2GB of
|
|
data must use @code{malloc} or @code{mmap} to allocate the data in the
|
|
heap instead of in the program's data segment.
|
|
|
|
When generating code for shared libraries, @option{-fpic} implies
|
|
@option{-msmall-data} and @option{-fPIC} implies @option{-mlarge-data}.
|
|
|
|
@item -mcpu=@var{cpu_type}
|
|
@opindex mcpu
|
|
Set the instruction set and instruction scheduling parameters for
|
|
machine type @var{cpu_type}. You can specify either the @samp{EV}
|
|
style name or the corresponding chip number. GCC supports scheduling
|
|
parameters for the EV4, EV5 and EV6 family of processors and will
|
|
choose the default values for the instruction set from the processor
|
|
you specify. If you do not specify a processor type, GCC will default
|
|
to the processor on which the compiler was built.
|
|
|
|
Supported values for @var{cpu_type} are
|
|
|
|
@table @samp
|
|
@item ev4
|
|
@item ev45
|
|
@itemx 21064
|
|
Schedules as an EV4 and has no instruction set extensions.
|
|
|
|
@item ev5
|
|
@itemx 21164
|
|
Schedules as an EV5 and has no instruction set extensions.
|
|
|
|
@item ev56
|
|
@itemx 21164a
|
|
Schedules as an EV5 and supports the BWX extension.
|
|
|
|
@item pca56
|
|
@itemx 21164pc
|
|
@itemx 21164PC
|
|
Schedules as an EV5 and supports the BWX and MAX extensions.
|
|
|
|
@item ev6
|
|
@itemx 21264
|
|
Schedules as an EV6 and supports the BWX, FIX, and MAX extensions.
|
|
|
|
@item ev67
|
|
@item 21264a
|
|
Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions.
|
|
@end table
|
|
|
|
@item -mtune=@var{cpu_type}
|
|
@opindex mtune
|
|
Set only the instruction scheduling parameters for machine type
|
|
@var{cpu_type}. The instruction set is not changed.
|
|
|
|
@item -mmemory-latency=@var{time}
|
|
@opindex mmemory-latency
|
|
Sets the latency the scheduler should assume for typical memory
|
|
references as seen by the application. This number is highly
|
|
dependent on the memory access patterns used by the application
|
|
and the size of the external cache on the machine.
|
|
|
|
Valid options for @var{time} are
|
|
|
|
@table @samp
|
|
@item @var{number}
|
|
A decimal number representing clock cycles.
|
|
|
|
@item L1
|
|
@itemx L2
|
|
@itemx L3
|
|
@itemx main
|
|
The compiler contains estimates of the number of clock cycles for
|
|
``typical'' EV4 & EV5 hardware for the Level 1, 2 & 3 caches
|
|
(also called Dcache, Scache, and Bcache), as well as to main memory.
|
|
Note that L3 is only valid for EV5.
|
|
|
|
@end table
|
|
@end table
|
|
|
|
@node DEC Alpha/VMS Options
|
|
@subsection DEC Alpha/VMS Options
|
|
|
|
These @samp{-m} options are defined for the DEC Alpha/VMS implementations:
|
|
|
|
@table @gcctabopt
|
|
@item -mvms-return-codes
|
|
@opindex mvms-return-codes
|
|
Return VMS condition codes from main. The default is to return POSIX
|
|
style condition (e.g.@ error) codes.
|
|
@end table
|
|
|
|
@node Clipper Options
|
|
@subsection Clipper Options
|
|
|
|
These @samp{-m} options are defined for the Clipper implementations:
|
|
|
|
@table @gcctabopt
|
|
@item -mc300
|
|
@opindex mc300
|
|
Produce code for a C300 Clipper processor. This is the default.
|
|
|
|
@item -mc400
|
|
@opindex mc400
|
|
Produce code for a C400 Clipper processor, i.e.@: use floating point
|
|
registers f8--f15.
|
|
@end table
|
|
|
|
@node H8/300 Options
|
|
@subsection H8/300 Options
|
|
|
|
These @samp{-m} options are defined for the H8/300 implementations:
|
|
|
|
@table @gcctabopt
|
|
@item -mrelax
|
|
@opindex mrelax
|
|
Shorten some address references at link time, when possible; uses the
|
|
linker option @option{-relax}. @xref{H8/300,, @code{ld} and the H8/300,
|
|
ld.info, Using ld}, for a fuller description.
|
|
|
|
@item -mh
|
|
@opindex mh
|
|
Generate code for the H8/300H@.
|
|
|
|
@item -ms
|
|
@opindex ms
|
|
Generate code for the H8/S@.
|
|
|
|
@item -ms2600
|
|
@opindex ms2600
|
|
Generate code for the H8/S2600. This switch must be used with @option{-ms}.
|
|
|
|
@item -mint32
|
|
@opindex mint32
|
|
Make @code{int} data 32 bits by default.
|
|
|
|
@item -malign-300
|
|
@opindex malign-300
|
|
On the H8/300H and H8/S, use the same alignment rules as for the H8/300.
|
|
The default for the H8/300H and H8/S is to align longs and floats on 4
|
|
byte boundaries.
|
|
@option{-malign-300} causes them to be aligned on 2 byte boundaries.
|
|
This option has no effect on the H8/300.
|
|
@end table
|
|
|
|
@node SH Options
|
|
@subsection SH Options
|
|
|
|
These @samp{-m} options are defined for the SH implementations:
|
|
|
|
@table @gcctabopt
|
|
@item -m1
|
|
@opindex m1
|
|
Generate code for the SH1.
|
|
|
|
@item -m2
|
|
@opindex m2
|
|
Generate code for the SH2.
|
|
|
|
@item -m3
|
|
@opindex m3
|
|
Generate code for the SH3.
|
|
|
|
@item -m3e
|
|
@opindex m3e
|
|
Generate code for the SH3e.
|
|
|
|
@item -m4-nofpu
|
|
@opindex m4-nofpu
|
|
Generate code for the SH4 without a floating-point unit.
|
|
|
|
@item -m4-single-only
|
|
@opindex m4-single-only
|
|
Generate code for the SH4 with a floating-point unit that only
|
|
supports single-precision arithmetic.
|
|
|
|
@item -m4-single
|
|
@opindex m4-single
|
|
Generate code for the SH4 assuming the floating-point unit is in
|
|
single-precision mode by default.
|
|
|
|
@item -m4
|
|
@opindex m4
|
|
Generate code for the SH4.
|
|
|
|
@item -mb
|
|
@opindex mb
|
|
Compile code for the processor in big endian mode.
|
|
|
|
@item -ml
|
|
@opindex ml
|
|
Compile code for the processor in little endian mode.
|
|
|
|
@item -mdalign
|
|
@opindex mdalign
|
|
Align doubles at 64-bit boundaries. Note that this changes the calling
|
|
conventions, and thus some functions from the standard C library will
|
|
not work unless you recompile it first with @option{-mdalign}.
|
|
|
|
@item -mrelax
|
|
@opindex mrelax
|
|
Shorten some address references at link time, when possible; uses the
|
|
linker option @option{-relax}.
|
|
|
|
@item -mbigtable
|
|
@opindex mbigtable
|
|
Use 32-bit offsets in @code{switch} tables. The default is to use
|
|
16-bit offsets.
|
|
|
|
@item -mfmovd
|
|
@opindex mfmovd
|
|
Enable the use of the instruction @code{fmovd}.
|
|
|
|
@item -mhitachi
|
|
@opindex mhitachi
|
|
Comply with the calling conventions defined by Hitachi.
|
|
|
|
@item -mnomacsave
|
|
@opindex mnomacsave
|
|
Mark the @code{MAC} register as call-clobbered, even if
|
|
@option{-mhitachi} is given.
|
|
|
|
@item -mieee
|
|
@opindex mieee
|
|
Increase IEEE-compliance of floating-point code.
|
|
|
|
@item -misize
|
|
@opindex misize
|
|
Dump instruction size and location in the assembly code.
|
|
|
|
@item -mpadstruct
|
|
@opindex mpadstruct
|
|
This option is deprecated. It pads structures to multiple of 4 bytes,
|
|
which is incompatible with the SH ABI@.
|
|
|
|
@item -mspace
|
|
@opindex mspace
|
|
Optimize for space instead of speed. Implied by @option{-Os}.
|
|
|
|
@item -mprefergot
|
|
@opindex mprefergot
|
|
When generating position-independent code, emit function calls using
|
|
the Global Offset Table instead of the Procedure Linkage Table.
|
|
|
|
@item -musermode
|
|
@opindex musermode
|
|
Generate a library function call to invalidate instruction cache
|
|
entries, after fixing up a trampoline. This library function call
|
|
doesn't assume it can write to the whole memory address space. This
|
|
is the default when the target is @code{sh-*-linux*}.
|
|
@end table
|
|
|
|
@node System V Options
|
|
@subsection Options for System V
|
|
|
|
These additional options are available on System V Release 4 for
|
|
compatibility with other compilers on those systems:
|
|
|
|
@table @gcctabopt
|
|
@item -G
|
|
@opindex G
|
|
Create a shared object.
|
|
It is recommended that @option{-symbolic} or @option{-shared} be used instead.
|
|
|
|
@item -Qy
|
|
@opindex Qy
|
|
Identify the versions of each tool used by the compiler, in a
|
|
@code{.ident} assembler directive in the output.
|
|
|
|
@item -Qn
|
|
@opindex Qn
|
|
Refrain from adding @code{.ident} directives to the output file (this is
|
|
the default).
|
|
|
|
@item -YP,@var{dirs}
|
|
@opindex YP
|
|
Search the directories @var{dirs}, and no others, for libraries
|
|
specified with @option{-l}.
|
|
|
|
@item -Ym,@var{dir}
|
|
@opindex Ym
|
|
Look in the directory @var{dir} to find the M4 preprocessor.
|
|
The assembler uses this option.
|
|
@c This is supposed to go with a -Yd for predefined M4 macro files, but
|
|
@c the generic assembler that comes with Solaris takes just -Ym.
|
|
@end table
|
|
|
|
@node TMS320C3x/C4x Options
|
|
@subsection TMS320C3x/C4x Options
|
|
@cindex TMS320C3x/C4x Options
|
|
|
|
These @samp{-m} options are defined for TMS320C3x/C4x implementations:
|
|
|
|
@table @gcctabopt
|
|
|
|
@item -mcpu=@var{cpu_type}
|
|
@opindex mcpu
|
|
Set the instruction set, register set, and instruction scheduling
|
|
parameters for machine type @var{cpu_type}. Supported values for
|
|
@var{cpu_type} are @samp{c30}, @samp{c31}, @samp{c32}, @samp{c40}, and
|
|
@samp{c44}. The default is @samp{c40} to generate code for the
|
|
TMS320C40.
|
|
|
|
@item -mbig-memory
|
|
@item -mbig
|
|
@itemx -msmall-memory
|
|
@itemx -msmall
|
|
@opindex mbig-memory
|
|
@opindex mbig
|
|
@opindex msmall-memory
|
|
@opindex msmall
|
|
Generates code for the big or small memory model. The small memory
|
|
model assumed that all data fits into one 64K word page. At run-time
|
|
the data page (DP) register must be set to point to the 64K page
|
|
containing the .bss and .data program sections. The big memory model is
|
|
the default and requires reloading of the DP register for every direct
|
|
memory access.
|
|
|
|
@item -mbk
|
|
@itemx -mno-bk
|
|
@opindex mbk
|
|
@opindex mno-bk
|
|
Allow (disallow) allocation of general integer operands into the block
|
|
count register BK@.
|
|
|
|
@item -mdb
|
|
@itemx -mno-db
|
|
@opindex mdb
|
|
@opindex mno-db
|
|
Enable (disable) generation of code using decrement and branch,
|
|
DBcond(D), instructions. This is enabled by default for the C4x. To be
|
|
on the safe side, this is disabled for the C3x, since the maximum
|
|
iteration count on the C3x is @math{2^23 + 1} (but who iterates loops more than
|
|
@math{2^23} times on the C3x?). Note that GCC will try to reverse a loop so
|
|
that it can utilise the decrement and branch instruction, but will give
|
|
up if there is more than one memory reference in the loop. Thus a loop
|
|
where the loop counter is decremented can generate slightly more
|
|
efficient code, in cases where the RPTB instruction cannot be utilised.
|
|
|
|
@item -mdp-isr-reload
|
|
@itemx -mparanoid
|
|
@opindex mdp-isr-reload
|
|
@opindex mparanoid
|
|
Force the DP register to be saved on entry to an interrupt service
|
|
routine (ISR), reloaded to point to the data section, and restored on
|
|
exit from the ISR@. This should not be required unless someone has
|
|
violated the small memory model by modifying the DP register, say within
|
|
an object library.
|
|
|
|
@item -mmpyi
|
|
@itemx -mno-mpyi
|
|
@opindex mmpyi
|
|
@opindex mno-mpyi
|
|
For the C3x use the 24-bit MPYI instruction for integer multiplies
|
|
instead of a library call to guarantee 32-bit results. Note that if one
|
|
of the operands is a constant, then the multiplication will be performed
|
|
using shifts and adds. If the @option{-mmpyi} option is not specified for the C3x,
|
|
then squaring operations are performed inline instead of a library call.
|
|
|
|
@item -mfast-fix
|
|
@itemx -mno-fast-fix
|
|
@opindex mfast-fix
|
|
@opindex mno-fast-fix
|
|
The C3x/C4x FIX instruction to convert a floating point value to an
|
|
integer value chooses the nearest integer less than or equal to the
|
|
floating point value rather than to the nearest integer. Thus if the
|
|
floating point number is negative, the result will be incorrectly
|
|
truncated an additional code is necessary to detect and correct this
|
|
case. This option can be used to disable generation of the additional
|
|
code required to correct the result.
|
|
|
|
@item -mrptb
|
|
@itemx -mno-rptb
|
|
@opindex mrptb
|
|
@opindex mno-rptb
|
|
Enable (disable) generation of repeat block sequences using the RPTB
|
|
instruction for zero overhead looping. The RPTB construct is only used
|
|
for innermost loops that do not call functions or jump across the loop
|
|
boundaries. There is no advantage having nested RPTB loops due to the
|
|
overhead required to save and restore the RC, RS, and RE registers.
|
|
This is enabled by default with @option{-O2}.
|
|
|
|
@item -mrpts=@var{count}
|
|
@itemx -mno-rpts
|
|
@opindex mrpts
|
|
@opindex mno-rpts
|
|
Enable (disable) the use of the single instruction repeat instruction
|
|
RPTS@. If a repeat block contains a single instruction, and the loop
|
|
count can be guaranteed to be less than the value @var{count}, GCC will
|
|
emit a RPTS instruction instead of a RPTB@. If no value is specified,
|
|
then a RPTS will be emitted even if the loop count cannot be determined
|
|
at compile time. Note that the repeated instruction following RPTS does
|
|
not have to be reloaded from memory each iteration, thus freeing up the
|
|
CPU buses for operands. However, since interrupts are blocked by this
|
|
instruction, it is disabled by default.
|
|
|
|
@item -mloop-unsigned
|
|
@itemx -mno-loop-unsigned
|
|
@opindex mloop-unsigned
|
|
@opindex mno-loop-unsigned
|
|
The maximum iteration count when using RPTS and RPTB (and DB on the C40)
|
|
is @math{2^31 + 1} since these instructions test if the iteration count is
|
|
negative to terminate the loop. If the iteration count is unsigned
|
|
there is a possibility than the @math{2^31 + 1} maximum iteration count may be
|
|
exceeded. This switch allows an unsigned iteration count.
|
|
|
|
@item -mti
|
|
@opindex mti
|
|
Try to emit an assembler syntax that the TI assembler (asm30) is happy
|
|
with. This also enforces compatibility with the API employed by the TI
|
|
C3x C compiler. For example, long doubles are passed as structures
|
|
rather than in floating point registers.
|
|
|
|
@item -mregparm
|
|
@itemx -mmemparm
|
|
@opindex mregparm
|
|
@opindex mmemparm
|
|
Generate code that uses registers (stack) for passing arguments to functions.
|
|
By default, arguments are passed in registers where possible rather
|
|
than by pushing arguments on to the stack.
|
|
|
|
@item -mparallel-insns
|
|
@itemx -mno-parallel-insns
|
|
@opindex mparallel-insns
|
|
@opindex mno-parallel-insns
|
|
Allow the generation of parallel instructions. This is enabled by
|
|
default with @option{-O2}.
|
|
|
|
@item -mparallel-mpy
|
|
@itemx -mno-parallel-mpy
|
|
@opindex mparallel-mpy
|
|
@opindex mno-parallel-mpy
|
|
Allow the generation of MPY||ADD and MPY||SUB parallel instructions,
|
|
provided @option{-mparallel-insns} is also specified. These instructions have
|
|
tight register constraints which can pessimize the code generation
|
|
of large functions.
|
|
|
|
@end table
|
|
|
|
@node V850 Options
|
|
@subsection V850 Options
|
|
@cindex V850 Options
|
|
|
|
These @samp{-m} options are defined for V850 implementations:
|
|
|
|
@table @gcctabopt
|
|
@item -mlong-calls
|
|
@itemx -mno-long-calls
|
|
@opindex mlong-calls
|
|
@opindex mno-long-calls
|
|
Treat all calls as being far away (near). If calls are assumed to be
|
|
far away, the compiler will always load the functions address up into a
|
|
register, and call indirect through the pointer.
|
|
|
|
@item -mno-ep
|
|
@itemx -mep
|
|
@opindex mno-ep
|
|
@opindex mep
|
|
Do not optimize (do optimize) basic blocks that use the same index
|
|
pointer 4 or more times to copy pointer into the @code{ep} register, and
|
|
use the shorter @code{sld} and @code{sst} instructions. The @option{-mep}
|
|
option is on by default if you optimize.
|
|
|
|
@item -mno-prolog-function
|
|
@itemx -mprolog-function
|
|
@opindex mno-prolog-function
|
|
@opindex mprolog-function
|
|
Do not use (do use) external functions to save and restore registers at
|
|
the prolog and epilog of a function. The external functions are slower,
|
|
but use less code space if more than one function saves the same number
|
|
of registers. The @option{-mprolog-function} option is on by default if
|
|
you optimize.
|
|
|
|
@item -mspace
|
|
@opindex mspace
|
|
Try to make the code as small as possible. At present, this just turns
|
|
on the @option{-mep} and @option{-mprolog-function} options.
|
|
|
|
@item -mtda=@var{n}
|
|
@opindex mtda
|
|
Put static or global variables whose size is @var{n} bytes or less into
|
|
the tiny data area that register @code{ep} points to. The tiny data
|
|
area can hold up to 256 bytes in total (128 bytes for byte references).
|
|
|
|
@item -msda=@var{n}
|
|
@opindex msda
|
|
Put static or global variables whose size is @var{n} bytes or less into
|
|
the small data area that register @code{gp} points to. The small data
|
|
area can hold up to 64 kilobytes.
|
|
|
|
@item -mzda=@var{n}
|
|
@opindex mzda
|
|
Put static or global variables whose size is @var{n} bytes or less into
|
|
the first 32 kilobytes of memory.
|
|
|
|
@item -mv850
|
|
@opindex mv850
|
|
Specify that the target processor is the V850.
|
|
|
|
@item -mbig-switch
|
|
@opindex mbig-switch
|
|
Generate code suitable for big switch tables. Use this option only if
|
|
the assembler/linker complain about out of range branches within a switch
|
|
table.
|
|
@end table
|
|
|
|
@node ARC Options
|
|
@subsection ARC Options
|
|
@cindex ARC Options
|
|
|
|
These options are defined for ARC implementations:
|
|
|
|
@table @gcctabopt
|
|
@item -EL
|
|
@opindex EL
|
|
Compile code for little endian mode. This is the default.
|
|
|
|
@item -EB
|
|
@opindex EB
|
|
Compile code for big endian mode.
|
|
|
|
@item -mmangle-cpu
|
|
@opindex mmangle-cpu
|
|
Prepend the name of the cpu to all public symbol names.
|
|
In multiple-processor systems, there are many ARC variants with different
|
|
instruction and register set characteristics. This flag prevents code
|
|
compiled for one cpu to be linked with code compiled for another.
|
|
No facility exists for handling variants that are ``almost identical''.
|
|
This is an all or nothing option.
|
|
|
|
@item -mcpu=@var{cpu}
|
|
@opindex mcpu
|
|
Compile code for ARC variant @var{cpu}.
|
|
Which variants are supported depend on the configuration.
|
|
All variants support @option{-mcpu=base}, this is the default.
|
|
|
|
@item -mtext=@var{text-section}
|
|
@itemx -mdata=@var{data-section}
|
|
@itemx -mrodata=@var{readonly-data-section}
|
|
@opindex mtext
|
|
@opindex mdata
|
|
@opindex mrodata
|
|
Put functions, data, and readonly data in @var{text-section},
|
|
@var{data-section}, and @var{readonly-data-section} respectively
|
|
by default. This can be overridden with the @code{section} attribute.
|
|
@xref{Variable Attributes}.
|
|
|
|
@end table
|
|
|
|
@node NS32K Options
|
|
@subsection NS32K Options
|
|
@cindex NS32K options
|
|
|
|
These are the @samp{-m} options defined for the 32000 series. The default
|
|
values for these options depends on which style of 32000 was selected when
|
|
the compiler was configured; the defaults for the most common choices are
|
|
given below.
|
|
|
|
@table @gcctabopt
|
|
@item -m32032
|
|
@itemx -m32032
|
|
@opindex m32032
|
|
@opindex m32032
|
|
Generate output for a 32032. This is the default
|
|
when the compiler is configured for 32032 and 32016 based systems.
|
|
|
|
@item -m32332
|
|
@itemx -m32332
|
|
@opindex m32332
|
|
@opindex m32332
|
|
Generate output for a 32332. This is the default
|
|
when the compiler is configured for 32332-based systems.
|
|
|
|
@item -m32532
|
|
@itemx -m32532
|
|
@opindex m32532
|
|
@opindex m32532
|
|
Generate output for a 32532. This is the default
|
|
when the compiler is configured for 32532-based systems.
|
|
|
|
@item -m32081
|
|
@opindex m32081
|
|
Generate output containing 32081 instructions for floating point.
|
|
This is the default for all systems.
|
|
|
|
@item -m32381
|
|
@opindex m32381
|
|
Generate output containing 32381 instructions for floating point. This
|
|
also implies @option{-m32081}. The 32381 is only compatible with the 32332
|
|
and 32532 cpus. This is the default for the pc532-netbsd configuration.
|
|
|
|
@item -mmulti-add
|
|
@opindex mmulti-add
|
|
Try and generate multiply-add floating point instructions @code{polyF}
|
|
and @code{dotF}. This option is only available if the @option{-m32381}
|
|
option is in effect. Using these instructions requires changes to
|
|
register allocation which generally has a negative impact on
|
|
performance. This option should only be enabled when compiling code
|
|
particularly likely to make heavy use of multiply-add instructions.
|
|
|
|
@item -mnomulti-add
|
|
@opindex mnomulti-add
|
|
Do not try and generate multiply-add floating point instructions
|
|
@code{polyF} and @code{dotF}. This is the default on all platforms.
|
|
|
|
@item -msoft-float
|
|
@opindex msoft-float
|
|
Generate output containing library calls for floating point.
|
|
@strong{Warning:} the requisite libraries may not be available.
|
|
|
|
@item -mnobitfield
|
|
@opindex mnobitfield
|
|
Do not use the bit-field instructions. On some machines it is faster to
|
|
use shifting and masking operations. This is the default for the pc532.
|
|
|
|
@item -mbitfield
|
|
@opindex mbitfield
|
|
Do use the bit-field instructions. This is the default for all platforms
|
|
except the pc532.
|
|
|
|
@item -mrtd
|
|
@opindex mrtd
|
|
Use a different function-calling convention, in which functions
|
|
that take a fixed number of arguments return pop their
|
|
arguments on return with the @code{ret} instruction.
|
|
|
|
This calling convention is incompatible with the one normally
|
|
used on Unix, so you cannot use it if you need to call libraries
|
|
compiled with the Unix compiler.
|
|
|
|
Also, you must provide function prototypes for all functions that
|
|
take variable numbers of arguments (including @code{printf});
|
|
otherwise incorrect code will be generated for calls to those
|
|
functions.
|
|
|
|
In addition, seriously incorrect code will result if you call a
|
|
function with too many arguments. (Normally, extra arguments are
|
|
harmlessly ignored.)
|
|
|
|
This option takes its name from the 680x0 @code{rtd} instruction.
|
|
|
|
|
|
@item -mregparam
|
|
@opindex mregparam
|
|
Use a different function-calling convention where the first two arguments
|
|
are passed in registers.
|
|
|
|
This calling convention is incompatible with the one normally
|
|
used on Unix, so you cannot use it if you need to call libraries
|
|
compiled with the Unix compiler.
|
|
|
|
@item -mnoregparam
|
|
@opindex mnoregparam
|
|
Do not pass any arguments in registers. This is the default for all
|
|
targets.
|
|
|
|
@item -msb
|
|
@opindex msb
|
|
It is OK to use the sb as an index register which is always loaded with
|
|
zero. This is the default for the pc532-netbsd target.
|
|
|
|
@item -mnosb
|
|
@opindex mnosb
|
|
The sb register is not available for use or has not been initialized to
|
|
zero by the run time system. This is the default for all targets except
|
|
the pc532-netbsd. It is also implied whenever @option{-mhimem} or
|
|
@option{-fpic} is set.
|
|
|
|
@item -mhimem
|
|
@opindex mhimem
|
|
Many ns32000 series addressing modes use displacements of up to 512MB@.
|
|
If an address is above 512MB then displacements from zero can not be used.
|
|
This option causes code to be generated which can be loaded above 512MB@.
|
|
This may be useful for operating systems or ROM code.
|
|
|
|
@item -mnohimem
|
|
@opindex mnohimem
|
|
Assume code will be loaded in the first 512MB of virtual address space.
|
|
This is the default for all platforms.
|
|
|
|
|
|
@end table
|
|
|
|
@node AVR Options
|
|
@subsection AVR Options
|
|
@cindex AVR Options
|
|
|
|
These options are defined for AVR implementations:
|
|
|
|
@table @gcctabopt
|
|
@item -mmcu=@var{mcu}
|
|
@opindex mmcu
|
|
Specify ATMEL AVR instruction set or MCU type.
|
|
|
|
Instruction set avr1 is for the minimal AVR core, not supported by the C
|
|
compiler, only for assembler programs (MCU types: at90s1200, attiny10,
|
|
attiny11, attiny12, attiny15, attiny28).
|
|
|
|
Instruction set avr2 (default) is for the classic AVR core with up to
|
|
8K program memory space (MCU types: at90s2313, at90s2323, attiny22,
|
|
at90s2333, at90s2343, at90s4414, at90s4433, at90s4434, at90s8515,
|
|
at90c8534, at90s8535).
|
|
|
|
Instruction set avr3 is for the classic AVR core with up to 128K program
|
|
memory space (MCU types: atmega103, atmega603, at43usb320, at76c711).
|
|
|
|
Instruction set avr4 is for the enhanced AVR core with up to 8K program
|
|
memory space (MCU types: atmega8, atmega83, atmega85).
|
|
|
|
Instruction set avr5 is for the enhanced AVR core with up to 128K program
|
|
memory space (MCU types: atmega16, atmega161, atmega163, atmega32, atmega323,
|
|
atmega64, atmega128, at43usb355, at94k).
|
|
|
|
@item -msize
|
|
@opindex msize
|
|
Output instruction sizes to the asm file.
|
|
|
|
@item -minit-stack=@var{N}
|
|
@opindex minit-stack
|
|
Specify the initial stack address, which may be a symbol or numeric value,
|
|
@samp{__stack} is the default.
|
|
|
|
@item -mno-interrupts
|
|
@opindex mno-interrupts
|
|
Generated code is not compatible with hardware interrupts.
|
|
Code size will be smaller.
|
|
|
|
@item -mcall-prologues
|
|
@opindex mcall-prologues
|
|
Functions prologues/epilogues expanded as call to appropriate
|
|
subroutines. Code size will be smaller.
|
|
|
|
@item -mno-tablejump
|
|
@opindex mno-tablejump
|
|
Do not generate tablejump insns which sometimes increase code size.
|
|
|
|
@item -mtiny-stack
|
|
@opindex mtiny-stack
|
|
Change only the low 8 bits of the stack pointer.
|
|
@end table
|
|
|
|
@node MCore Options
|
|
@subsection MCore Options
|
|
@cindex MCore options
|
|
|
|
These are the @samp{-m} options defined for the Motorola M*Core
|
|
processors.
|
|
|
|
@table @gcctabopt
|
|
|
|
@item -mhardlit
|
|
@itemx -mhardlit
|
|
@itemx -mno-hardlit
|
|
@opindex mhardlit
|
|
@opindex mhardlit
|
|
@opindex mno-hardlit
|
|
Inline constants into the code stream if it can be done in two
|
|
instructions or less.
|
|
|
|
@item -mdiv
|
|
@itemx -mdiv
|
|
@itemx -mno-div
|
|
@opindex mdiv
|
|
@opindex mdiv
|
|
@opindex mno-div
|
|
Use the divide instruction. (Enabled by default).
|
|
|
|
@item -mrelax-immediate
|
|
@itemx -mrelax-immediate
|
|
@itemx -mno-relax-immediate
|
|
@opindex mrelax-immediate
|
|
@opindex mrelax-immediate
|
|
@opindex mno-relax-immediate
|
|
Allow arbitrary sized immediates in bit operations.
|
|
|
|
@item -mwide-bitfields
|
|
@itemx -mwide-bitfields
|
|
@itemx -mno-wide-bitfields
|
|
@opindex mwide-bitfields
|
|
@opindex mwide-bitfields
|
|
@opindex mno-wide-bitfields
|
|
Always treat bit-fields as int-sized.
|
|
|
|
@item -m4byte-functions
|
|
@itemx -m4byte-functions
|
|
@itemx -mno-4byte-functions
|
|
@opindex m4byte-functions
|
|
@opindex m4byte-functions
|
|
@opindex mno-4byte-functions
|
|
Force all functions to be aligned to a four byte boundary.
|
|
|
|
@item -mcallgraph-data
|
|
@itemx -mcallgraph-data
|
|
@itemx -mno-callgraph-data
|
|
@opindex mcallgraph-data
|
|
@opindex mcallgraph-data
|
|
@opindex mno-callgraph-data
|
|
Emit callgraph information.
|
|
|
|
@item -mslow-bytes
|
|
@itemx -mslow-bytes
|
|
@itemx -mno-slow-bytes
|
|
@opindex mslow-bytes
|
|
@opindex mslow-bytes
|
|
@opindex mno-slow-bytes
|
|
Prefer word access when reading byte quantities.
|
|
|
|
@item -mlittle-endian
|
|
@itemx -mlittle-endian
|
|
@itemx -mbig-endian
|
|
@opindex mlittle-endian
|
|
@opindex mlittle-endian
|
|
@opindex mbig-endian
|
|
Generate code for a little endian target.
|
|
|
|
@item -m210
|
|
@itemx -m210
|
|
@itemx -m340
|
|
@opindex m210
|
|
@opindex m210
|
|
@opindex m340
|
|
Generate code for the 210 processor.
|
|
@end table
|
|
|
|
@node IA-64 Options
|
|
@subsection IA-64 Options
|
|
@cindex IA-64 Options
|
|
|
|
These are the @samp{-m} options defined for the Intel IA-64 architecture.
|
|
|
|
@table @gcctabopt
|
|
@item -mbig-endian
|
|
@opindex mbig-endian
|
|
Generate code for a big endian target. This is the default for HPUX@.
|
|
|
|
@item -mlittle-endian
|
|
@opindex mlittle-endian
|
|
Generate code for a little endian target. This is the default for AIX5
|
|
and Linux.
|
|
|
|
@item -mgnu-as
|
|
@itemx -mno-gnu-as
|
|
@opindex mgnu-as
|
|
@opindex mno-gnu-as
|
|
Generate (or don't) code for the GNU assembler. This is the default.
|
|
@c Also, this is the default if the configure option @option{--with-gnu-as}
|
|
@c is used.
|
|
|
|
@item -mgnu-ld
|
|
@itemx -mno-gnu-ld
|
|
@opindex mgnu-ld
|
|
@opindex mno-gnu-ld
|
|
Generate (or don't) code for the GNU linker. This is the default.
|
|
@c Also, this is the default if the configure option @option{--with-gnu-ld}
|
|
@c is used.
|
|
|
|
@item -mno-pic
|
|
@opindex mno-pic
|
|
Generate code that does not use a global pointer register. The result
|
|
is not position independent code, and violates the IA-64 ABI@.
|
|
|
|
@item -mvolatile-asm-stop
|
|
@itemx -mno-volatile-asm-stop
|
|
@opindex mvolatile-asm-stop
|
|
@opindex mno-volatile-asm-stop
|
|
Generate (or don't) a stop bit immediately before and after volatile asm
|
|
statements.
|
|
|
|
@item -mb-step
|
|
@opindex mb-step
|
|
Generate code that works around Itanium B step errata.
|
|
|
|
@item -mregister-names
|
|
@itemx -mno-register-names
|
|
@opindex mregister-names
|
|
@opindex mno-register-names
|
|
Generate (or don't) @samp{in}, @samp{loc}, and @samp{out} register names for
|
|
the stacked registers. This may make assembler output more readable.
|
|
|
|
@item -mno-sdata
|
|
@itemx -msdata
|
|
@opindex mno-sdata
|
|
@opindex msdata
|
|
Disable (or enable) optimizations that use the small data section. This may
|
|
be useful for working around optimizer bugs.
|
|
|
|
@item -mconstant-gp
|
|
@opindex mconstant-gp
|
|
Generate code that uses a single constant global pointer value. This is
|
|
useful when compiling kernel code.
|
|
|
|
@item -mauto-pic
|
|
@opindex mauto-pic
|
|
Generate code that is self-relocatable. This implies @option{-mconstant-gp}.
|
|
This is useful when compiling firmware code.
|
|
|
|
@item -minline-divide-min-latency
|
|
@opindex minline-divide-min-latency
|
|
Generate code for inline divides using the minimum latency algorithm.
|
|
|
|
@item -minline-divide-max-throughput
|
|
@opindex minline-divide-max-throughput
|
|
Generate code for inline divides using the maximum throughput algorithm.
|
|
|
|
@item -mno-dwarf2-asm
|
|
@itemx -mdwarf2-asm
|
|
@opindex mno-dwarf2-asm
|
|
@opindex mdwarf2-asm
|
|
Don't (or do) generate assembler code for the DWARF2 line number debugging
|
|
info. This may be useful when not using the GNU assembler.
|
|
|
|
@item -mfixed-range=@var{register-range}
|
|
@opindex mfixed-range
|
|
Generate code treating the given register range as fixed registers.
|
|
A fixed register is one that the register allocator can not use. This is
|
|
useful when compiling kernel code. A register range is specified as
|
|
two registers separated by a dash. Multiple register ranges can be
|
|
specified separated by a comma.
|
|
@end table
|
|
|
|
@node D30V Options
|
|
@subsection D30V Options
|
|
@cindex D30V Options
|
|
|
|
These @samp{-m} options are defined for D30V implementations:
|
|
|
|
@table @gcctabopt
|
|
@item -mextmem
|
|
@opindex mextmem
|
|
Link the @samp{.text}, @samp{.data}, @samp{.bss}, @samp{.strings},
|
|
@samp{.rodata}, @samp{.rodata1}, @samp{.data1} sections into external
|
|
memory, which starts at location @code{0x80000000}.
|
|
|
|
@item -mextmemory
|
|
@opindex mextmemory
|
|
Same as the @option{-mextmem} switch.
|
|
|
|
@item -monchip
|
|
@opindex monchip
|
|
Link the @samp{.text} section into onchip text memory, which starts at
|
|
location @code{0x0}. Also link @samp{.data}, @samp{.bss},
|
|
@samp{.strings}, @samp{.rodata}, @samp{.rodata1}, @samp{.data1} sections
|
|
into onchip data memory, which starts at location @code{0x20000000}.
|
|
|
|
@item -mno-asm-optimize
|
|
@itemx -masm-optimize
|
|
@opindex mno-asm-optimize
|
|
@opindex masm-optimize
|
|
Disable (enable) passing @option{-O} to the assembler when optimizing.
|
|
The assembler uses the @option{-O} option to automatically parallelize
|
|
adjacent short instructions where possible.
|
|
|
|
@item -mbranch-cost=@var{n}
|
|
@opindex mbranch-cost
|
|
Increase the internal costs of branches to @var{n}. Higher costs means
|
|
that the compiler will issue more instructions to avoid doing a branch.
|
|
The default is 2.
|
|
|
|
@item -mcond-exec=@var{n}
|
|
@opindex mcond-exec
|
|
Specify the maximum number of conditionally executed instructions that
|
|
replace a branch. The default is 4.
|
|
@end table
|
|
|
|
@node S/390 and zSeries Options
|
|
@subsection S/390 and zSeries Options
|
|
@cindex S/390 and zSeries Options
|
|
|
|
These are the @samp{-m} options defined for the S/390 and zSeries architecture.
|
|
|
|
@table @gcctabopt
|
|
@item -mhard-float
|
|
@itemx -msoft-float
|
|
@opindex mhard-float
|
|
@opindex msoft-float
|
|
Use (do not use) the hardware floating-point instructions and registers
|
|
for floating-point operations. When @option{-msoft-float} is specified,
|
|
functions in @file{libgcc.a} will be used to perform floating-point
|
|
operations. When @option{-mhard-float} is specified, the compiler
|
|
generates IEEE floating-point instructions. This is the default.
|
|
|
|
@item -mbackchain
|
|
@itemx -mno-backchain
|
|
@opindex mbackchain
|
|
@opindex mno-backchain
|
|
Generate (or do not generate) code which maintains an explicit
|
|
backchain within the stack frame that points to the caller's frame.
|
|
This is currently needed to allow debugging. The default is to
|
|
generate the backchain.
|
|
|
|
@item -msmall-exec
|
|
@itemx -mno-small-exec
|
|
@opindex msmall-exec
|
|
@opindex mno-small-exec
|
|
Generate (or do not generate) code using the @code{bras} instruction
|
|
to do subroutine calls.
|
|
This only works reliably if the total executable size does not
|
|
exceed 64k. The default is to use the @code{basr} instruction instead,
|
|
which does not have this limitation.
|
|
|
|
@item -m64
|
|
@itemx -m31
|
|
@opindex m64
|
|
@opindex m31
|
|
When @option{-m31} is specified, generate code compliant to the
|
|
Linux for S/390 ABI@. When @option{-m64} is specified, generate
|
|
code compliant to the Linux for zSeries ABI@. This allows GCC in
|
|
particular to generate 64-bit instructions. For the @samp{s390}
|
|
targets, the default is @option{-m31}, while the @samp{s390x}
|
|
targets default to @option{-m64}.
|
|
|
|
@item -mmvcle
|
|
@itemx -mno-mvcle
|
|
@opindex mmvcle
|
|
@opindex mno-mvcle
|
|
Generate (or do not generate) code using the @code{mvcle} instruction
|
|
to perform block moves. When @option{-mno-mvcle} is specifed,
|
|
use a @code{mvc} loop instead. This is the default.
|
|
|
|
@item -mdebug
|
|
@itemx -mno-debug
|
|
@opindex mdebug
|
|
@opindex mno-debug
|
|
Print (or do not print) additional debug information when compiling.
|
|
The default is to not print debug information.
|
|
|
|
@end table
|
|
|
|
@node CRIS Options
|
|
@subsection CRIS Options
|
|
@cindex CRIS Options
|
|
|
|
These options are defined specifically for the CRIS ports.
|
|
|
|
@table @gcctabopt
|
|
@item -march=@var{architecture-type}
|
|
@itemx -mcpu=@var{architecture-type}
|
|
@opindex march
|
|
@opindex mcpu
|
|
Generate code for the specified architecture. The choices for
|
|
@var{architecture-type} are @samp{v3}, @samp{v8} and @samp{v10} for
|
|
respectively ETRAX@w{ }4, ETRAX@w{ }100, and ETRAX@w{ }100@w{ }LX.
|
|
Default is @samp{v0} except for cris-axis-linux-gnu, where the default is
|
|
@samp{v10}.
|
|
|
|
@item -mtune=@var{architecture-type}
|
|
@opindex mtune
|
|
Tune to @var{architecture-type} everything applicable about the generated
|
|
code, except for the ABI and the set of available instructions. The
|
|
choices for @var{architecture-type} are the same as for
|
|
@option{-march=@var{architecture-type}}.
|
|
|
|
@item -mmax-stack-frame=@var{n}
|
|
@opindex mmax-stack-frame
|
|
Warn when the stack frame of a function exceeds @var{n} bytes.
|
|
|
|
@item -melinux-stacksize=@var{n}
|
|
@opindex melinux-stacksize
|
|
Only available with the @samp{cris-axis-aout} target. Arranges for
|
|
indications in the program to the kernel loader that the stack of the
|
|
program should be set to @var{n} bytes.
|
|
|
|
@item -metrax4
|
|
@itemx -metrax100
|
|
@opindex metrax4
|
|
@opindex metrax100
|
|
The options @option{-metrax4} and @option{-metrax100} are synonyms for
|
|
@option{-march=v3} and @option{-march=v8} respectively.
|
|
|
|
@item -mpdebug
|
|
@opindex mpdebug
|
|
Enable CRIS-specific verbose debug-related information in the assembly
|
|
code. This option also has the effect to turn off the @samp{#NO_APP}
|
|
formatted-code indicator to the assembler at the beginning of the
|
|
assembly file.
|
|
|
|
@item -mcc-init
|
|
@opindex mcc-init
|
|
Do not use condition-code results from previous instruction; always emit
|
|
compare and test instructions before use of condition codes.
|
|
|
|
@item -mno-side-effects
|
|
@opindex mno-side-effects
|
|
Do not emit instructions with side-effects in addressing modes other than
|
|
post-increment.
|
|
|
|
@item -mstack-align
|
|
@itemx -mno-stack-align
|
|
@itemx -mdata-align
|
|
@itemx -mno-data-align
|
|
@itemx -mconst-align
|
|
@itemx -mno-const-align
|
|
@opindex mstack-align
|
|
@opindex mno-stack-align
|
|
@opindex mdata-align
|
|
@opindex mno-data-align
|
|
@opindex mconst-align
|
|
@opindex mno-const-align
|
|
These options (no-options) arranges (eliminate arrangements) for the
|
|
stack-frame, individual data and constants to be aligned for the maximum
|
|
single data access size for the chosen CPU model. The default is to
|
|
arrange for 32-bit alignment. ABI details such as structure layout are
|
|
not affected by these options.
|
|
|
|
@item -m32-bit
|
|
@itemx -m16-bit
|
|
@itemx -m8-bit
|
|
@opindex m32-bit
|
|
@opindex m16-bit
|
|
@opindex m8-bit
|
|
Similar to the stack- data- and const-align options above, these options
|
|
arrange for stack-frame, writable data and constants to all be 32-bit,
|
|
16-bit or 8-bit aligned. The default is 32-bit alignment.
|
|
|
|
@item -mno-prologue-epilogue
|
|
@itemx -mprologue-epilogue
|
|
@opindex mno-prologue-epilogue
|
|
@opindex mprologue-epilogue
|
|
With @option{-mno-prologue-epilogue}, the normal function prologue and
|
|
epilogue that sets up the stack-frame are omitted and no return
|
|
instructions or return sequences are generated in the code. Use this
|
|
option only together with visual inspection of the compiled code: no
|
|
warnings or errors are generated when call-saved registers must be saved,
|
|
or storage for local variable needs to be allocated.
|
|
|
|
@item -mno-gotplt
|
|
@itemx -mgotplt
|
|
@opindex mno-gotplt
|
|
@opindex mgotplt
|
|
With @option{-fpic} and @option{-fPIC}, don't generate (do generate)
|
|
instruction sequences that load addresses for functions from the PLT part
|
|
of the GOT rather than (traditional on other architectures) calls to the
|
|
PLT. The default is @option{-mgotplt}.
|
|
|
|
@item -maout
|
|
@opindex maout
|
|
Legacy no-op option only recognized with the cris-axis-aout target.
|
|
|
|
@item -melf
|
|
@opindex melf
|
|
Legacy no-op option only recognized with the cris-axis-elf and
|
|
cris-axis-linux-gnu targets.
|
|
|
|
@item -melinux
|
|
@opindex melinux
|
|
Only recognized with the cris-axis-aout target, where it selects a
|
|
GNU/linux-like multilib, include files and instruction set for
|
|
@option{-march=v8}.
|
|
|
|
@item -mlinux
|
|
@opindex mlinux
|
|
Legacy no-op option only recognized with the cris-axis-linux-gnu target.
|
|
|
|
@item -sim
|
|
@opindex sim
|
|
This option, recognized for the cris-axis-aout and cris-axis-elf arranges
|
|
to link with input-output functions from a simulator library. Code,
|
|
initialized data and zero-initialized data are allocated consecutively.
|
|
|
|
@item -sim2
|
|
@opindex sim2
|
|
Like @option{-sim}, but pass linker options to locate initialized data at
|
|
0x40000000 and zero-initialized data at 0x80000000.
|
|
@end table
|
|
|
|
@node MMIX Options
|
|
@subsection MMIX Options
|
|
@cindex MMIX Options
|
|
|
|
These options are defined for the MMIX:
|
|
|
|
@table @gcctabopt
|
|
@item -mlibfuncs
|
|
@itemx -mno-libfuncs
|
|
@opindex mlibfuncs
|
|
@opindex mno-libfuncs
|
|
Specify that intrinsic library functions are being compiled, passing all
|
|
values in registers, no matter the size.
|
|
|
|
@item -mepsilon
|
|
@itemx -mno-epsilon
|
|
@opindex mepsilon
|
|
@opindex mno-epsilon
|
|
Generate floating-point comparison instructions that compare with respect
|
|
to the @code{rE} epsilon register.
|
|
|
|
@item -mabi=mmixware
|
|
@itemx -mabi=gnu
|
|
@opindex mabi-mmixware
|
|
@opindex mabi=gnu
|
|
Generate code that passes function parameters and return values that (in
|
|
the called function) are seen as registers @code{$0} and up, as opposed to
|
|
the GNU ABI which uses global registers @code{$231} and up.
|
|
|
|
@item -mzero-extend
|
|
@itemx -mno-zero-extend
|
|
@opindex mzero-extend
|
|
@opindex mno-zero-extend
|
|
When reading data from memory in sizes shorter than 64 bits, use (do not
|
|
use) zero-extending load instructions by default, rather than
|
|
sign-extending ones.
|
|
|
|
@item -mknuthdiv
|
|
@itemx -mno-knuthdiv
|
|
@opindex mknuthdiv
|
|
@opindex mno-knuthdiv
|
|
Make the result of a division yielding a remainder have the same sign as
|
|
the divisor. With the default, @option{-mno-knuthdiv}, the sign of the
|
|
remainder follows the sign of the dividend. Both methods are
|
|
arithmetically valid, the latter being almost exclusively used.
|
|
|
|
@item -mtoplevel-symbols
|
|
@itemx -mno-toplevel-symbols
|
|
@opindex mtoplevel-symbols
|
|
@opindex mno-toplevel-symbols
|
|
Prepend (do not prepend) a @samp{:} to all global symbols, so the assembly
|
|
code can be used with the @code{PREFIX} assembly directive.
|
|
|
|
@item -melf
|
|
@opindex melf
|
|
Generate an executable in the ELF format, rather than the default
|
|
@samp{mmo} format used by the @command{mmix} simulator.
|
|
|
|
@item -mbranch-predict
|
|
@itemx -mno-branch-predict
|
|
@opindex mbranch-predict
|
|
@opindex mno-branch-predict
|
|
Use (do not use) the probable-branch instructions, when static branch
|
|
prediction indicates a probable branch.
|
|
@end table
|
|
|
|
@node PDP-11 Options
|
|
@subsection PDP-11 Options
|
|
@cindex PDP-11 Options
|
|
|
|
These options are defined for the PDP-11:
|
|
|
|
@table @gcctabopt
|
|
@item -mfpu
|
|
@opindex mfpu
|
|
Use hardware FPP floating point. This is the default. (FIS floating
|
|
point on the PDP-11/40 is not supported.)
|
|
|
|
@item -msoft-float
|
|
@opindex msoft-float
|
|
Do not use hardware floating point.
|
|
|
|
@item -mac0
|
|
@opindex mac0
|
|
Return floating-point results in ac0 (fr0 in Unix assembler syntax).
|
|
|
|
@item -mno-ac0
|
|
@opindex mno-ac0
|
|
Return floating-point results in memory. This is the default.
|
|
|
|
@item -m40
|
|
@opindex m40
|
|
Generate code for a PDP-11/40.
|
|
|
|
@item -m45
|
|
@opindex m45
|
|
Generate code for a PDP-11/45. This is the default.
|
|
|
|
@item -m10
|
|
@opindex m10
|
|
Generate code for a PDP-11/10.
|
|
|
|
@item -mbcopy-builtin
|
|
@opindex bcopy-builtin
|
|
Use inline @code{movstrhi} patterns for copying memory. This is the
|
|
default.
|
|
|
|
@item -mbcopy
|
|
@opindex mbcopy
|
|
Do not use inline @code{movstrhi} patterns for copying memory.
|
|
|
|
@item -mint16
|
|
@itemx -mno-int32
|
|
@opindex mint16
|
|
@opindex mno-int32
|
|
Use 16-bit @code{int}. This is the default.
|
|
|
|
@item -mint32
|
|
@itemx -mno-int16
|
|
@opindex mint32
|
|
@opindex mno-int16
|
|
Use 32-bit @code{int}.
|
|
|
|
@item -mfloat64
|
|
@itemx -mno-float32
|
|
@opindex mfloat64
|
|
@opindex mno-float32
|
|
Use 64-bit @code{float}. This is the default.
|
|
|
|
@item -mfloat32
|
|
@item -mno-float64
|
|
@opindex mfloat32
|
|
@opindex mno-float64
|
|
Use 32-bit @code{float}.
|
|
|
|
@item -mabshi
|
|
@opindex mabshi
|
|
Use @code{abshi2} pattern. This is the default.
|
|
|
|
@item -mno-abshi
|
|
@opindex mno-abshi
|
|
Do not use @code{abshi2} pattern.
|
|
|
|
@item -mbranch-expensive
|
|
@opindex mbranch-expensive
|
|
Pretend that branches are expensive. This is for experimenting with
|
|
code generation only.
|
|
|
|
@item -mbranch-cheap
|
|
@opindex mbranch-cheap
|
|
Do not pretend that branches are expensive. This is the default.
|
|
|
|
@item -msplit
|
|
@opindex msplit
|
|
Generate code for a system with split I&D.
|
|
|
|
@item -mno-split
|
|
@opindex mno-split
|
|
Generate code for a system without split I&D. This is the default.
|
|
|
|
@item -munix-asm
|
|
@opindex munix-asm
|
|
Use Unix assembler syntax. This is the default when configured for
|
|
@samp{pdp11-*-bsd}.
|
|
|
|
@item -mdec-asm
|
|
@opindex mdec-asm
|
|
Use DEC assembler syntax. This is the default when configured for any
|
|
PDP-11 target other than @samp{pdp11-*-bsd}.
|
|
@end table
|
|
|
|
@node Xstormy16 Options
|
|
@subsection Xstormy16 Options
|
|
@cindex Xstormy16 Options
|
|
|
|
These options are defined for Xstormy16:
|
|
|
|
@table @gcctabopt
|
|
@item -msim
|
|
@opindex msim
|
|
Choose startup files and linker script suitable for the simulator.
|
|
@end table
|
|
|
|
@node Xtensa Options
|
|
@subsection Xtensa Options
|
|
@cindex Xtensa Options
|
|
|
|
The Xtensa architecture is designed to support many different
|
|
configurations. The compiler's default options can be set to match a
|
|
particular Xtensa configuration by copying a configuration file into the
|
|
GCC sources when building GCC@. The options below may be used to
|
|
override the default options.
|
|
|
|
@table @gcctabopt
|
|
@item -mbig-endian
|
|
@itemx -mlittle-endian
|
|
@opindex mbig-endian
|
|
@opindex mlittle-endian
|
|
Specify big-endian or little-endian byte ordering for the target Xtensa
|
|
processor.
|
|
|
|
@item -mdensity
|
|
@itemx -mno-density
|
|
@opindex mdensity
|
|
@opindex mno-density
|
|
Enable or disable use of the optional Xtensa code density instructions.
|
|
|
|
@item -mmac16
|
|
@itemx -mno-mac16
|
|
@opindex mmac16
|
|
@opindex mno-mac16
|
|
Enable or disable use of the Xtensa MAC16 option. When enabled, GCC
|
|
will generate MAC16 instructions from standard C code, with the
|
|
limitation that it will use neither the MR register file nor any
|
|
instruction that operates on the MR registers. When this option is
|
|
disabled, GCC will translate 16-bit multiply/accumulate operations to a
|
|
combination of core instructions and library calls, depending on whether
|
|
any other multiplier options are enabled.
|
|
|
|
@item -mmul16
|
|
@itemx -mno-mul16
|
|
@opindex mmul16
|
|
@opindex mno-mul16
|
|
Enable or disable use of the 16-bit integer multiplier option. When
|
|
enabled, the compiler will generate 16-bit multiply instructions for
|
|
multiplications of 16 bits or smaller in standard C code. When this
|
|
option is disabled, the compiler will either use 32-bit multiply or
|
|
MAC16 instructions if they are available or generate library calls to
|
|
perform the multiply operations using shifts and adds.
|
|
|
|
@item -mmul32
|
|
@itemx -mno-mul32
|
|
@opindex mmul32
|
|
@opindex mno-mul32
|
|
Enable or disable use of the 32-bit integer multiplier option. When
|
|
enabled, the compiler will generate 32-bit multiply instructions for
|
|
multiplications of 32 bits or smaller in standard C code. When this
|
|
option is disabled, the compiler will generate library calls to perform
|
|
the multiply operations using either shifts and adds or 16-bit multiply
|
|
instructions if they are available.
|
|
|
|
@item -mnsa
|
|
@itemx -mno-nsa
|
|
@opindex mnsa
|
|
@opindex mno-nsa
|
|
Enable or disable use of the optional normalization shift amount
|
|
(@code{NSA}) instructions to implement the built-in @code{ffs} function.
|
|
|
|
@item -mminmax
|
|
@itemx -mno-minmax
|
|
@opindex mminmax
|
|
@opindex mno-minmax
|
|
Enable or disable use of the optional minimum and maximum value
|
|
instructions.
|
|
|
|
@item -msext
|
|
@itemx -mno-sext
|
|
@opindex msext
|
|
@opindex mno-sext
|
|
Enable or disable use of the optional sign extend (@code{SEXT})
|
|
instruction.
|
|
|
|
@item -mbooleans
|
|
@itemx -mno-booleans
|
|
@opindex mbooleans
|
|
@opindex mno-booleans
|
|
Enable or disable support for the boolean register file used by Xtensa
|
|
coprocessors. This is not typically useful by itself but may be
|
|
required for other options that make use of the boolean registers (e.g.,
|
|
the floating-point option).
|
|
|
|
@item -mhard-float
|
|
@itemx -msoft-float
|
|
@opindex mhard-float
|
|
@opindex msoft-float
|
|
Enable or disable use of the floating-point option. When enabled, GCC
|
|
generates floating-point instructions for 32-bit @code{float}
|
|
operations. When this option is disabled, GCC generates library calls
|
|
to emulate 32-bit floating-point operations using integer instructions.
|
|
Regardless of this option, 64-bit @code{double} operations are always
|
|
emulated with calls to library functions.
|
|
|
|
@item -mfused-madd
|
|
@itemx -mno-fused-madd
|
|
@opindex mfused-madd
|
|
@opindex mno-fused-madd
|
|
Enable or disable use of fused multiply/add and multiply/subtract
|
|
instructions in the floating-point option. This has no effect if the
|
|
floating-point option is not also enabled. Disabling fused multiply/add
|
|
and multiply/subtract instructions forces the compiler to use separate
|
|
instructions for the multiply and add/subtract operations. This may be
|
|
desirable in some cases where strict IEEE 754-compliant results are
|
|
required: the fused multiply add/subtract instructions do not round the
|
|
intermediate result, thereby producing results with @emph{more} bits of
|
|
precision than specified by the IEEE standard. Disabling fused multiply
|
|
add/subtract instructions also ensures that the program output is not
|
|
sensitive to the compiler's ability to combine multiply and add/subtract
|
|
operations.
|
|
|
|
@item -mserialize-volatile
|
|
@itemx -mno-serialize-volatile
|
|
@opindex mserialize-volatile
|
|
@opindex mno-serialize-volatile
|
|
When this option is enabled, GCC inserts @code{MEMW} instructions before
|
|
@code{volatile} memory references to guarantee sequential consistency.
|
|
The default is @option{-mserialize-volatile}. Use
|
|
@option{-mno-serialize-volatile} to omit the @code{MEMW} instructions.
|
|
|
|
@item -mtext-section-literals
|
|
@itemx -mno-text-section-literals
|
|
@opindex mtext-section-literals
|
|
@opindex mno-text-section-literals
|
|
Control the treatment of literal pools. The default is
|
|
@option{-mno-text-section-literals}, which places literals in a separate
|
|
section in the output file. This allows the literal pool to be placed
|
|
in a data RAM/ROM, and it also allows the linker to combine literal
|
|
pools from separate object files to remove redundant literals and
|
|
improve code size. With @option{-mtext-section-literals}, the literals
|
|
are interspersed in the text section in order to keep them as close as
|
|
possible to their references. This may be necessary for large assembly
|
|
files.
|
|
|
|
@item -mtarget-align
|
|
@itemx -mno-target-align
|
|
@opindex mtarget-align
|
|
@opindex mno-target-align
|
|
When this option is enabled, GCC instructs the assembler to
|
|
automatically align instructions to reduce branch penalties at the
|
|
expense of some code density. The assembler attempts to widen density
|
|
instructions to align branch targets and the instructions following call
|
|
instructions. If there are not enough preceding safe density
|
|
instructions to align a target, no widening will be performed. The
|
|
default is @option{-mtarget-align}. These options do not affect the
|
|
treatment of auto-aligned instructions like @code{LOOP}, which the
|
|
assembler will always align, either by widening density instructions or
|
|
by inserting no-op instructions.
|
|
|
|
@item -mlongcalls
|
|
@itemx -mno-longcalls
|
|
@opindex mlongcalls
|
|
@opindex mno-longcalls
|
|
When this option is enabled, GCC instructs the assembler to translate
|
|
direct calls to indirect calls unless it can determine that the target
|
|
of a direct call is in the range allowed by the call instruction. This
|
|
translation typically occurs for calls to functions in other source
|
|
files. Specifically, the assembler translates a direct @code{CALL}
|
|
instruction into an @code{L32R} followed by a @code{CALLX} instruction.
|
|
The default is @option{-mno-longcalls}. This option should be used in
|
|
programs where the call target can potentially be out of range. This
|
|
option is implemented in the assembler, not the compiler, so the
|
|
assembly code generated by GCC will still show direct call
|
|
instructions---look at the disassembled object code to see the actual
|
|
instructions. Note that the assembler will use an indirect call for
|
|
every cross-file call, not just those that really will be out of range.
|
|
@end table
|
|
|
|
@node Code Gen Options
|
|
@section Options for Code Generation Conventions
|
|
@cindex code generation conventions
|
|
@cindex options, code generation
|
|
@cindex run-time options
|
|
|
|
These machine-independent options control the interface conventions
|
|
used in code generation.
|
|
|
|
Most of them have both positive and negative forms; the negative form
|
|
of @option{-ffoo} would be @option{-fno-foo}. In the table below, only
|
|
one of the forms is listed---the one which is not the default. You
|
|
can figure out the other form by either removing @samp{no-} or adding
|
|
it.
|
|
|
|
@table @gcctabopt
|
|
@item -fexceptions
|
|
@opindex fexceptions
|
|
Enable exception handling. Generates extra code needed to propagate
|
|
exceptions. For some targets, this implies GCC will generate frame
|
|
unwind information for all functions, which can produce significant data
|
|
size overhead, although it does not affect execution. If you do not
|
|
specify this option, GCC will enable it by default for languages like
|
|
C++ which normally require exception handling, and disable it for
|
|
languages like C that do not normally require it. However, you may need
|
|
to enable this option when compiling C code that needs to interoperate
|
|
properly with exception handlers written in C++. You may also wish to
|
|
disable this option if you are compiling older C++ programs that don't
|
|
use exception handling.
|
|
|
|
@item -fnon-call-exceptions
|
|
@opindex fnon-call-exceptions
|
|
Generate code that allows trapping instructions to throw exceptions.
|
|
Note that this requires platform-specific runtime support that does
|
|
not exist everywhere. Moreover, it only allows @emph{trapping}
|
|
instructions to throw exceptions, i.e.@: memory references or floating
|
|
point instructions. It does not allow exceptions to be thrown from
|
|
arbitrary signal handlers such as @code{SIGALRM}.
|
|
|
|
@item -funwind-tables
|
|
@opindex funwind-tables
|
|
Similar to @option{-fexceptions}, except that it will just generate any needed
|
|
static data, but will not affect the generated code in any other way.
|
|
You will normally not enable this option; instead, a language processor
|
|
that needs this handling would enable it on your behalf.
|
|
|
|
@item -fasynchronous-unwind-tables
|
|
@opindex funwind-tables
|
|
Generate unwind table in dwarf2 format, if supported by target machine. The
|
|
table is exact at each instruction boundary, so it can be used for stack
|
|
unwinding from asynchronous events (such as debugger or garbage collector).
|
|
|
|
@item -fpcc-struct-return
|
|
@opindex fpcc-struct-return
|
|
Return ``short'' @code{struct} and @code{union} values in memory like
|
|
longer ones, rather than in registers. This convention is less
|
|
efficient, but it has the advantage of allowing intercallability between
|
|
GCC-compiled files and files compiled with other compilers.
|
|
|
|
The precise convention for returning structures in memory depends
|
|
on the target configuration macros.
|
|
|
|
Short structures and unions are those whose size and alignment match
|
|
that of some integer type.
|
|
|
|
@item -freg-struct-return
|
|
@opindex freg-struct-return
|
|
Return @code{struct} and @code{union} values in registers when possible.
|
|
This is more efficient for small structures than
|
|
@option{-fpcc-struct-return}.
|
|
|
|
If you specify neither @option{-fpcc-struct-return} nor
|
|
@option{-freg-struct-return}, GCC defaults to whichever convention is
|
|
standard for the target. If there is no standard convention, GCC
|
|
defaults to @option{-fpcc-struct-return}, except on targets where GCC is
|
|
the principal compiler. In those cases, we can choose the standard, and
|
|
we chose the more efficient register return alternative.
|
|
|
|
@item -fshort-enums
|
|
@opindex fshort-enums
|
|
Allocate to an @code{enum} type only as many bytes as it needs for the
|
|
declared range of possible values. Specifically, the @code{enum} type
|
|
will be equivalent to the smallest integer type which has enough room.
|
|
|
|
@item -fshort-double
|
|
@opindex fshort-double
|
|
Use the same size for @code{double} as for @code{float}.
|
|
|
|
@item -fshared-data
|
|
@opindex fshared-data
|
|
Requests that the data and non-@code{const} variables of this
|
|
compilation be shared data rather than private data. The distinction
|
|
makes sense only on certain operating systems, where shared data is
|
|
shared between processes running the same program, while private data
|
|
exists in one copy per process.
|
|
|
|
@item -fno-common
|
|
@opindex fno-common
|
|
In C, allocate even uninitialized global variables in the data section of the
|
|
object file, rather than generating them as common blocks. This has the
|
|
effect that if the same variable is declared (without @code{extern}) in
|
|
two different compilations, you will get an error when you link them.
|
|
The only reason this might be useful is if you wish to verify that the
|
|
program will work on other systems which always work this way.
|
|
|
|
@item -fno-ident
|
|
@opindex fno-ident
|
|
Ignore the @samp{#ident} directive.
|
|
|
|
@item -fno-gnu-linker
|
|
@opindex fno-gnu-linker
|
|
Do not output global initializations (such as C++ constructors and
|
|
destructors) in the form used by the GNU linker (on systems where the GNU
|
|
linker is the standard method of handling them). Use this option when
|
|
you want to use a non-GNU linker, which also requires using the
|
|
@command{collect2} program to make sure the system linker includes
|
|
constructors and destructors. (@command{collect2} is included in the GCC
|
|
distribution.) For systems which @emph{must} use @command{collect2}, the
|
|
compiler driver @command{gcc} is configured to do this automatically.
|
|
|
|
@item -finhibit-size-directive
|
|
@opindex finhibit-size-directive
|
|
Don't output a @code{.size} assembler directive, or anything else that
|
|
would cause trouble if the function is split in the middle, and the
|
|
two halves are placed at locations far apart in memory. This option is
|
|
used when compiling @file{crtstuff.c}; you should not need to use it
|
|
for anything else.
|
|
|
|
@item -fverbose-asm
|
|
@opindex fverbose-asm
|
|
Put extra commentary information in the generated assembly code to
|
|
make it more readable. This option is generally only of use to those
|
|
who actually need to read the generated assembly code (perhaps while
|
|
debugging the compiler itself).
|
|
|
|
@option{-fno-verbose-asm}, the default, causes the
|
|
extra information to be omitted and is useful when comparing two assembler
|
|
files.
|
|
|
|
@item -fvolatile
|
|
@opindex fvolatile
|
|
Consider all memory references through pointers to be volatile.
|
|
|
|
@item -fvolatile-global
|
|
@opindex fvolatile-global
|
|
Consider all memory references to extern and global data items to
|
|
be volatile. GCC does not consider static data items to be volatile
|
|
because of this switch.
|
|
|
|
@item -fvolatile-static
|
|
@opindex fvolatile-static
|
|
Consider all memory references to static data to be volatile.
|
|
|
|
@item -fpic
|
|
@opindex fpic
|
|
@cindex global offset table
|
|
@cindex PIC
|
|
Generate position-independent code (PIC) suitable for use in a shared
|
|
library, if supported for the target machine. Such code accesses all
|
|
constant addresses through a global offset table (GOT)@. The dynamic
|
|
loader resolves the GOT entries when the program starts (the dynamic
|
|
loader is not part of GCC; it is part of the operating system). If
|
|
the GOT size for the linked executable exceeds a machine-specific
|
|
maximum size, you get an error message from the linker indicating that
|
|
@option{-fpic} does not work; in that case, recompile with @option{-fPIC}
|
|
instead. (These maximums are 16k on the m88k, 8k on the Sparc, and 32k
|
|
on the m68k and RS/6000. The 386 has no such limit.)
|
|
|
|
Position-independent code requires special support, and therefore works
|
|
only on certain machines. For the 386, GCC supports PIC for System V
|
|
but not for the Sun 386i. Code generated for the IBM RS/6000 is always
|
|
position-independent.
|
|
|
|
@item -fPIC
|
|
@opindex fPIC
|
|
If supported for the target machine, emit position-independent code,
|
|
suitable for dynamic linking and avoiding any limit on the size of the
|
|
global offset table. This option makes a difference on the m68k, m88k,
|
|
and the Sparc.
|
|
|
|
Position-independent code requires special support, and therefore works
|
|
only on certain machines.
|
|
|
|
@item -ffixed-@var{reg}
|
|
@opindex ffixed
|
|
Treat the register named @var{reg} as a fixed register; generated code
|
|
should never refer to it (except perhaps as a stack pointer, frame
|
|
pointer or in some other fixed role).
|
|
|
|
@var{reg} must be the name of a register. The register names accepted
|
|
are machine-specific and are defined in the @code{REGISTER_NAMES}
|
|
macro in the machine description macro file.
|
|
|
|
This flag does not have a negative form, because it specifies a
|
|
three-way choice.
|
|
|
|
@item -fcall-used-@var{reg}
|
|
@opindex fcall-used
|
|
Treat the register named @var{reg} as an allocable register that is
|
|
clobbered by function calls. It may be allocated for temporaries or
|
|
variables that do not live across a call. Functions compiled this way
|
|
will not save and restore the register @var{reg}.
|
|
|
|
It is an error to used this flag with the frame pointer or stack pointer.
|
|
Use of this flag for other registers that have fixed pervasive roles in
|
|
the machine's execution model will produce disastrous results.
|
|
|
|
This flag does not have a negative form, because it specifies a
|
|
three-way choice.
|
|
|
|
@item -fcall-saved-@var{reg}
|
|
@opindex fcall-saved
|
|
Treat the register named @var{reg} as an allocable register saved by
|
|
functions. It may be allocated even for temporaries or variables that
|
|
live across a call. Functions compiled this way will save and restore
|
|
the register @var{reg} if they use it.
|
|
|
|
It is an error to used this flag with the frame pointer or stack pointer.
|
|
Use of this flag for other registers that have fixed pervasive roles in
|
|
the machine's execution model will produce disastrous results.
|
|
|
|
A different sort of disaster will result from the use of this flag for
|
|
a register in which function values may be returned.
|
|
|
|
This flag does not have a negative form, because it specifies a
|
|
three-way choice.
|
|
|
|
@item -fpack-struct
|
|
@opindex fpack-struct
|
|
Pack all structure members together without holes. Usually you would
|
|
not want to use this option, since it makes the code suboptimal, and
|
|
the offsets of structure members won't agree with system libraries.
|
|
|
|
@item -finstrument-functions
|
|
@opindex finstrument-functions
|
|
Generate instrumentation calls for entry and exit to functions. Just
|
|
after function entry and just before function exit, the following
|
|
profiling functions will be called with the address of the current
|
|
function and its call site. (On some platforms,
|
|
@code{__builtin_return_address} does not work beyond the current
|
|
function, so the call site information may not be available to the
|
|
profiling functions otherwise.)
|
|
|
|
@example
|
|
void __cyg_profile_func_enter (void *this_fn,
|
|
void *call_site);
|
|
void __cyg_profile_func_exit (void *this_fn,
|
|
void *call_site);
|
|
@end example
|
|
|
|
The first argument is the address of the start of the current function,
|
|
which may be looked up exactly in the symbol table.
|
|
|
|
This instrumentation is also done for functions expanded inline in other
|
|
functions. The profiling calls will indicate where, conceptually, the
|
|
inline function is entered and exited. This means that addressable
|
|
versions of such functions must be available. If all your uses of a
|
|
function are expanded inline, this may mean an additional expansion of
|
|
code size. If you use @samp{extern inline} in your C code, an
|
|
addressable version of such functions must be provided. (This is
|
|
normally the case anyways, but if you get lucky and the optimizer always
|
|
expands the functions inline, you might have gotten away without
|
|
providing static copies.)
|
|
|
|
A function may be given the attribute @code{no_instrument_function}, in
|
|
which case this instrumentation will not be done. This can be used, for
|
|
example, for the profiling functions listed above, high-priority
|
|
interrupt routines, and any functions from which the profiling functions
|
|
cannot safely be called (perhaps signal handlers, if the profiling
|
|
routines generate output or allocate memory).
|
|
|
|
@item -fstack-check
|
|
@opindex fstack-check
|
|
Generate code to verify that you do not go beyond the boundary of the
|
|
stack. You should specify this flag if you are running in an
|
|
environment with multiple threads, but only rarely need to specify it in
|
|
a single-threaded environment since stack overflow is automatically
|
|
detected on nearly all systems if there is only one stack.
|
|
|
|
Note that this switch does not actually cause checking to be done; the
|
|
operating system must do that. The switch causes generation of code
|
|
to ensure that the operating system sees the stack being extended.
|
|
|
|
@item -fstack-limit-register=@var{reg}
|
|
@itemx -fstack-limit-symbol=@var{sym}
|
|
@itemx -fno-stack-limit
|
|
@opindex fstack-limit-register
|
|
@opindex fstack-limit-symbol
|
|
@opindex fno-stack-limit
|
|
Generate code to ensure that the stack does not grow beyond a certain value,
|
|
either the value of a register or the address of a symbol. If the stack
|
|
would grow beyond the value, a signal is raised. For most targets,
|
|
the signal is raised before the stack overruns the boundary, so
|
|
it is possible to catch the signal without taking special precautions.
|
|
|
|
For instance, if the stack starts at absolute address @samp{0x80000000}
|
|
and grows downwards, you can use the flags
|
|
@option{-fstack-limit-symbol=__stack_limit} and
|
|
@option{-Wl,--defsym,__stack_limit=0x7ffe0000} to enforce a stack limit
|
|
of 128KB@. Note that this may only work with the GNU linker.
|
|
|
|
@cindex aliasing of parameters
|
|
@cindex parameters, aliased
|
|
@item -fargument-alias
|
|
@itemx -fargument-noalias
|
|
@itemx -fargument-noalias-global
|
|
@opindex fargument-alias
|
|
@opindex fargument-noalias
|
|
@opindex fargument-noalias-global
|
|
Specify the possible relationships among parameters and between
|
|
parameters and global data.
|
|
|
|
@option{-fargument-alias} specifies that arguments (parameters) may
|
|
alias each other and may alias global storage.@*
|
|
@option{-fargument-noalias} specifies that arguments do not alias
|
|
each other, but may alias global storage.@*
|
|
@option{-fargument-noalias-global} specifies that arguments do not
|
|
alias each other and do not alias global storage.
|
|
|
|
Each language will automatically use whatever option is required by
|
|
the language standard. You should not need to use these options yourself.
|
|
|
|
@item -fleading-underscore
|
|
@opindex fleading-underscore
|
|
This option and its counterpart, @option{-fno-leading-underscore}, forcibly
|
|
change the way C symbols are represented in the object file. One use
|
|
is to help link with legacy assembly code.
|
|
|
|
Be warned that you should know what you are doing when invoking this
|
|
option, and that not all targets provide complete support for it.
|
|
@end table
|
|
|
|
@c man end
|
|
|
|
@node Environment Variables
|
|
@section Environment Variables Affecting GCC
|
|
@cindex environment variables
|
|
|
|
@c man begin ENVIRONMENT
|
|
|
|
This section describes several environment variables that affect how GCC
|
|
operates. Some of them work by specifying directories or prefixes to use
|
|
when searching for various kinds of files. Some are used to specify other
|
|
aspects of the compilation environment.
|
|
|
|
Note that you can also specify places to search using options such as
|
|
@option{-B}, @option{-I} and @option{-L} (@pxref{Directory Options}). These
|
|
take precedence over places specified using environment variables, which
|
|
in turn take precedence over those specified by the configuration of GCC@.
|
|
@xref{Driver,, Controlling the Compilation Driver @file{gcc}, gccint,
|
|
GNU Compiler Collection (GCC) Internals}.
|
|
|
|
@table @env
|
|
@item LANG
|
|
@itemx LC_CTYPE
|
|
@c @itemx LC_COLLATE
|
|
@itemx LC_MESSAGES
|
|
@c @itemx LC_MONETARY
|
|
@c @itemx LC_NUMERIC
|
|
@c @itemx LC_TIME
|
|
@itemx LC_ALL
|
|
@findex LANG
|
|
@findex LC_CTYPE
|
|
@c @findex LC_COLLATE
|
|
@findex LC_MESSAGES
|
|
@c @findex LC_MONETARY
|
|
@c @findex LC_NUMERIC
|
|
@c @findex LC_TIME
|
|
@findex LC_ALL
|
|
@cindex locale
|
|
These environment variables control the way that GCC uses
|
|
localization information that allow GCC to work with different
|
|
national conventions. GCC inspects the locale categories
|
|
@env{LC_CTYPE} and @env{LC_MESSAGES} if it has been configured to do
|
|
so. These locale categories can be set to any value supported by your
|
|
installation. A typical value is @samp{en_UK} for English in the United
|
|
Kingdom.
|
|
|
|
The @env{LC_CTYPE} environment variable specifies character
|
|
classification. GCC uses it to determine the character boundaries in
|
|
a string; this is needed for some multibyte encodings that contain quote
|
|
and escape characters that would otherwise be interpreted as a string
|
|
end or escape.
|
|
|
|
The @env{LC_MESSAGES} environment variable specifies the language to
|
|
use in diagnostic messages.
|
|
|
|
If the @env{LC_ALL} environment variable is set, it overrides the value
|
|
of @env{LC_CTYPE} and @env{LC_MESSAGES}; otherwise, @env{LC_CTYPE}
|
|
and @env{LC_MESSAGES} default to the value of the @env{LANG}
|
|
environment variable. If none of these variables are set, GCC
|
|
defaults to traditional C English behavior.
|
|
|
|
@item TMPDIR
|
|
@findex TMPDIR
|
|
If @env{TMPDIR} is set, it specifies the directory to use for temporary
|
|
files. GCC uses temporary files to hold the output of one stage of
|
|
compilation which is to be used as input to the next stage: for example,
|
|
the output of the preprocessor, which is the input to the compiler
|
|
proper.
|
|
|
|
@item GCC_EXEC_PREFIX
|
|
@findex GCC_EXEC_PREFIX
|
|
If @env{GCC_EXEC_PREFIX} is set, it specifies a prefix to use in the
|
|
names of the subprograms executed by the compiler. No slash is added
|
|
when this prefix is combined with the name of a subprogram, but you can
|
|
specify a prefix that ends with a slash if you wish.
|
|
|
|
If @env{GCC_EXEC_PREFIX} is not set, GCC will attempt to figure out
|
|
an appropriate prefix to use based on the pathname it was invoked with.
|
|
|
|
If GCC cannot find the subprogram using the specified prefix, it
|
|
tries looking in the usual places for the subprogram.
|
|
|
|
The default value of @env{GCC_EXEC_PREFIX} is
|
|
@file{@var{prefix}/lib/gcc-lib/} where @var{prefix} is the value
|
|
of @code{prefix} when you ran the @file{configure} script.
|
|
|
|
Other prefixes specified with @option{-B} take precedence over this prefix.
|
|
|
|
This prefix is also used for finding files such as @file{crt0.o} that are
|
|
used for linking.
|
|
|
|
In addition, the prefix is used in an unusual way in finding the
|
|
directories to search for header files. For each of the standard
|
|
directories whose name normally begins with @samp{/usr/local/lib/gcc-lib}
|
|
(more precisely, with the value of @env{GCC_INCLUDE_DIR}), GCC tries
|
|
replacing that beginning with the specified prefix to produce an
|
|
alternate directory name. Thus, with @option{-Bfoo/}, GCC will search
|
|
@file{foo/bar} where it would normally search @file{/usr/local/lib/bar}.
|
|
These alternate directories are searched first; the standard directories
|
|
come next.
|
|
|
|
@item COMPILER_PATH
|
|
@findex COMPILER_PATH
|
|
The value of @env{COMPILER_PATH} is a colon-separated list of
|
|
directories, much like @env{PATH}. GCC tries the directories thus
|
|
specified when searching for subprograms, if it can't find the
|
|
subprograms using @env{GCC_EXEC_PREFIX}.
|
|
|
|
@item LIBRARY_PATH
|
|
@findex LIBRARY_PATH
|
|
The value of @env{LIBRARY_PATH} is a colon-separated list of
|
|
directories, much like @env{PATH}. When configured as a native compiler,
|
|
GCC tries the directories thus specified when searching for special
|
|
linker files, if it can't find them using @env{GCC_EXEC_PREFIX}. Linking
|
|
using GCC also uses these directories when searching for ordinary
|
|
libraries for the @option{-l} option (but directories specified with
|
|
@option{-L} come first).
|
|
|
|
@item C_INCLUDE_PATH
|
|
@itemx CPLUS_INCLUDE_PATH
|
|
@itemx OBJC_INCLUDE_PATH
|
|
@findex C_INCLUDE_PATH
|
|
@findex CPLUS_INCLUDE_PATH
|
|
@findex OBJC_INCLUDE_PATH
|
|
@c @itemx OBJCPLUS_INCLUDE_PATH
|
|
These environment variables pertain to particular languages. Each
|
|
variable's value is a colon-separated list of directories, much like
|
|
@env{PATH}. When GCC searches for header files, it tries the
|
|
directories listed in the variable for the language you are using, after
|
|
the directories specified with @option{-I} but before the standard header
|
|
file directories.
|
|
|
|
@item DEPENDENCIES_OUTPUT
|
|
@findex DEPENDENCIES_OUTPUT
|
|
@cindex dependencies for make as output
|
|
If this variable is set, its value specifies how to output dependencies
|
|
for Make based on the header files processed by the compiler. This
|
|
output looks much like the output from the @option{-M} option
|
|
(@pxref{Preprocessor Options}), but it goes to a separate file, and is
|
|
in addition to the usual results of compilation.
|
|
|
|
The value of @env{DEPENDENCIES_OUTPUT} can be just a file name, in
|
|
which case the Make rules are written to that file, guessing the target
|
|
name from the source file name. Or the value can have the form
|
|
@samp{@var{file} @var{target}}, in which case the rules are written to
|
|
file @var{file} using @var{target} as the target name.
|
|
|
|
@item LANG
|
|
@findex LANG
|
|
@cindex locale definition
|
|
This variable is used to pass locale information to the compiler. One way in
|
|
which this information is used is to determine the character set to be used
|
|
when character literals, string literals and comments are parsed in C and C++.
|
|
When the compiler is configured to allow multibyte characters,
|
|
the following values for @env{LANG} are recognized:
|
|
|
|
@table @samp
|
|
@item C-JIS
|
|
Recognize JIS characters.
|
|
@item C-SJIS
|
|
Recognize SJIS characters.
|
|
@item C-EUCJP
|
|
Recognize EUCJP characters.
|
|
@end table
|
|
|
|
If @env{LANG} is not defined, or if it has some other value, then the
|
|
compiler will use mblen and mbtowc as defined by the default locale to
|
|
recognize and translate multibyte characters.
|
|
@end table
|
|
|
|
@c man end
|
|
|
|
@node Running Protoize
|
|
@section Running Protoize
|
|
|
|
The program @code{protoize} is an optional part of GCC@. You can use
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it to add prototypes to a program, thus converting the program to ISO
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C in one respect. The companion program @code{unprotoize} does the
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reverse: it removes argument types from any prototypes that are found.
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When you run these programs, you must specify a set of source files as
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command line arguments. The conversion programs start out by compiling
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these files to see what functions they define. The information gathered
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about a file @var{foo} is saved in a file named @file{@var{foo}.X}.
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After scanning comes actual conversion. The specified files are all
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eligible to be converted; any files they include (whether sources or
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just headers) are eligible as well.
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But not all the eligible files are converted. By default,
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@code{protoize} and @code{unprotoize} convert only source and header
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files in the current directory. You can specify additional directories
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whose files should be converted with the @option{-d @var{directory}}
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option. You can also specify particular files to exclude with the
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@option{-x @var{file}} option. A file is converted if it is eligible, its
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directory name matches one of the specified directory names, and its
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name within the directory has not been excluded.
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Basic conversion with @code{protoize} consists of rewriting most
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function definitions and function declarations to specify the types of
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the arguments. The only ones not rewritten are those for varargs
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functions.
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@code{protoize} optionally inserts prototype declarations at the
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beginning of the source file, to make them available for any calls that
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precede the function's definition. Or it can insert prototype
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declarations with block scope in the blocks where undeclared functions
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are called.
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Basic conversion with @code{unprotoize} consists of rewriting most
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function declarations to remove any argument types, and rewriting
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function definitions to the old-style pre-ISO form.
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Both conversion programs print a warning for any function declaration or
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definition that they can't convert. You can suppress these warnings
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with @option{-q}.
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The output from @code{protoize} or @code{unprotoize} replaces the
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original source file. The original file is renamed to a name ending
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with @samp{.save} (for DOS, the saved filename ends in @samp{.sav}
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without the original @samp{.c} suffix). If the @samp{.save} (@samp{.sav}
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for DOS) file already exists, then the source file is simply discarded.
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@code{protoize} and @code{unprotoize} both depend on GCC itself to
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scan the program and collect information about the functions it uses.
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So neither of these programs will work until GCC is installed.
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Here is a table of the options you can use with @code{protoize} and
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@code{unprotoize}. Each option works with both programs unless
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otherwise stated.
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@table @code
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@item -B @var{directory}
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Look for the file @file{SYSCALLS.c.X} in @var{directory}, instead of the
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usual directory (normally @file{/usr/local/lib}). This file contains
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prototype information about standard system functions. This option
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applies only to @code{protoize}.
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@item -c @var{compilation-options}
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Use @var{compilation-options} as the options when running @code{gcc} to
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produce the @samp{.X} files. The special option @option{-aux-info} is
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always passed in addition, to tell @code{gcc} to write a @samp{.X} file.
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Note that the compilation options must be given as a single argument to
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@code{protoize} or @code{unprotoize}. If you want to specify several
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@code{gcc} options, you must quote the entire set of compilation options
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to make them a single word in the shell.
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There are certain @code{gcc} arguments that you cannot use, because they
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would produce the wrong kind of output. These include @option{-g},
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@option{-O}, @option{-c}, @option{-S}, and @option{-o} If you include these in
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the @var{compilation-options}, they are ignored.
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@item -C
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Rename files to end in @samp{.C} (@samp{.cc} for DOS-based file
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systems) instead of @samp{.c}. This is convenient if you are converting
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a C program to C++. This option applies only to @code{protoize}.
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@item -g
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Add explicit global declarations. This means inserting explicit
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declarations at the beginning of each source file for each function
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that is called in the file and was not declared. These declarations
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precede the first function definition that contains a call to an
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undeclared function. This option applies only to @code{protoize}.
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@item -i @var{string}
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Indent old-style parameter declarations with the string @var{string}.
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This option applies only to @code{protoize}.
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@code{unprotoize} converts prototyped function definitions to old-style
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function definitions, where the arguments are declared between the
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argument list and the initial @samp{@{}. By default, @code{unprotoize}
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uses five spaces as the indentation. If you want to indent with just
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one space instead, use @option{-i " "}.
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@item -k
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Keep the @samp{.X} files. Normally, they are deleted after conversion
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is finished.
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@item -l
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Add explicit local declarations. @code{protoize} with @option{-l} inserts
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a prototype declaration for each function in each block which calls the
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function without any declaration. This option applies only to
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@code{protoize}.
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@item -n
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Make no real changes. This mode just prints information about the conversions
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that would have been done without @option{-n}.
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@item -N
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Make no @samp{.save} files. The original files are simply deleted.
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Use this option with caution.
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@item -p @var{program}
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Use the program @var{program} as the compiler. Normally, the name
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@file{gcc} is used.
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@item -q
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Work quietly. Most warnings are suppressed.
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@item -v
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Print the version number, just like @option{-v} for @code{gcc}.
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@end table
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If you need special compiler options to compile one of your program's
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source files, then you should generate that file's @samp{.X} file
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specially, by running @code{gcc} on that source file with the
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appropriate options and the option @option{-aux-info}. Then run
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@code{protoize} on the entire set of files. @code{protoize} will use
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the existing @samp{.X} file because it is newer than the source file.
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For example:
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@example
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gcc -Dfoo=bar file1.c -aux-info file1.X
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protoize *.c
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@end example
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@noindent
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You need to include the special files along with the rest in the
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@code{protoize} command, even though their @samp{.X} files already
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exist, because otherwise they won't get converted.
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@xref{Protoize Caveats}, for more information on how to use
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@code{protoize} successfully.
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