205 lines
8.9 KiB
Plaintext
205 lines
8.9 KiB
Plaintext
@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
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@c 2000, 2001, 2002, 2003 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 gccint.texi.
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@node Host Config
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@chapter Host Configuration
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@cindex host configuration
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Most details about the machine and system on which the compiler is
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actually running are detected by the @command{configure} script. Some
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things are impossible for @command{configure} to detect; these are
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described in two ways, either by macros defined in a file named
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@file{xm-@var{machine}.h} or by hook functions in the file specified
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by the @var{out_host_hook_obj} variable in @file{config.gcc}. (The
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intention is that very few hosts will need a header file but nearly
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every fully supported host will need to override some hooks.)
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If you need to define only a few macros, and they have simple
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definitions, consider using the @code{xm_defines} variable in your
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@file{config.gcc} entry instead of creating a host configuration
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header. @xref{System Config}.
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@menu
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* Host Common:: Things every host probably needs implemented.
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* Filesystem:: Your host can't have the letter `a' in filenames?
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* Host Misc:: Rare configuration options for hosts.
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@end menu
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@node Host Common
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@section Host Common
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@cindex host hooks
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@cindex host functions
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Some things are just not portable, even between similar operating systems,
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and are too difficult for autoconf to detect. They get implemented using
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hook functions in the file specified by the @var{host_hook_obj}
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variable in @file{config.gcc}.
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@deftypefn {Host Hook} void HOST_HOOKS_EXTRA_SIGNALS (void)
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This host hook is used to set up handling for extra signals. The most
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common thing to do in this hook is to detect stack overflow.
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@end deftypefn
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@deftypefn {Host Hook} void * HOST_HOOKS_GT_PCH_GET_ADDRESS (size_t @var{size})
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This host hook returns the address of some space in which a PCH may be
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loaded with @samp{HOST_HOOKS_PCH_LOAD_PCH}. The space will need to
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have @var{size} bytes. If insufficient space is available,
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@samp{NULL} may be returned; the PCH machinery will try to find a
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suitable address using a heuristic.
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The memory does not have to be available now. In fact, usually
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@samp{HOST_HOOKS_PCH_LOAD_PCH} will already have been called. The memory
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need only be available in future invocations of GCC.
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@end deftypefn
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@deftypefn {Host Hook} bool HOST_HOOKS_GT_PCH_USE_ADDRESS (size_t @var{size}, void * @var{address})
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This host hook is called when a PCH file is about to be loaded. If
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@var{address} is the address that would have been returned by
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@samp{HOST_HOOKS_PCH_MEMORY_ADDRESS}, and @var{size} is smaller than
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the maximum than @samp{HOST_HOOKS_PCH_MEMORY_ADDRESS} would have
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accepted, return true, otherwise return false.
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In addition, free any address space reserved that isn't needed to hold
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@var{size} bytes (whether or not true is returned). The PCH machinery will
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use @samp{mmap} with @samp{MAP_FIXED} to load the PCH if @samp{HAVE_MMAP_FILE},
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or will use @samp{fread} otherwise.
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If no PCH will be loaded, this hook may be called with @var{size}
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zero, in which case all reserved address space should be freed.
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Do not try to handle values of @var{address} that could not have been
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returned by this executable; just return false. Such values usually
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indicate an out-of-date PCH file (built by some other GCC executable),
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and such a PCH file won't work.
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@end deftypefn
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@node Filesystem
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@section Host Filesystem
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@cindex configuration file
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@cindex @file{xm-@var{machine}.h}
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GCC needs to know a number of things about the semantics of the host
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machine's filesystem. Filesystems with Unix and MS-DOS semantics are
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automatically detected. For other systems, you can define the
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following macros in @file{xm-@var{machine}.h}.
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@ftable @code
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@item HAVE_DOS_BASED_FILE_SYSTEM
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This macro is automatically defined by @file{system.h} if the host
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file system obeys the semantics defined by MS-DOS instead of Unix.
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DOS file systems are case insensitive, file specifications may begin
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with a drive letter, and both forward slash and backslash (@samp{/}
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and @samp{\}) are directory separators.
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@item DIR_SEPARATOR
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@itemx DIR_SEPARATOR_2
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If defined, these macros expand to character constants specifying
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separators for directory names within a file specification.
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@file{system.h} will automatically give them appropriate values on
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Unix and MS-DOS file systems. If your file system is neither of
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these, define one or both appropriately in @file{xm-@var{machine}.h}.
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However, operating systems like VMS, where constructing a pathname is
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more complicated than just stringing together directory names
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separated by a special character, should not define either of these
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macros.
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@item PATH_SEPARATOR
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If defined, this macro should expand to a character constant
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specifying the separator for elements of search paths. The default
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value is a colon (@samp{:}). DOS-based systems usually, but not
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always, use semicolon (@samp{;}).
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@item VMS
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Define this macro if the host system is VMS@.
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@item HOST_OBJECT_SUFFIX
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Define this macro to be a C string representing the suffix for object
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files on your host machine. If you do not define this macro, GCC will
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use @samp{.o} as the suffix for object files.
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@item HOST_EXECUTABLE_SUFFIX
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Define this macro to be a C string representing the suffix for
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executable files on your host machine. If you do not define this macro,
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GCC will use the null string as the suffix for executable files.
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@item HOST_BIT_BUCKET
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A pathname defined by the host operating system, which can be opened as
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a file and written to, but all the information written is discarded.
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This is commonly known as a @dfn{bit bucket} or @dfn{null device}. If
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you do not define this macro, GCC will use @samp{/dev/null} as the bit
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bucket. If the host does not support a bit bucket, define this macro to
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an invalid filename.
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@item UPDATE_PATH_HOST_CANONICALIZE (@var{path})
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If defined, a C statement (sans semicolon) that performs host-dependent
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canonicalization when a path used in a compilation driver or
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preprocessor is canonicalized. @var{path} is a malloc-ed path to be
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canonicalized. If the C statement does canonicalize @var{path} into a
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different buffer, the old path should be freed and the new buffer should
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have been allocated with malloc.
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@item DUMPFILE_FORMAT
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Define this macro to be a C string representing the format to use for
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constructing the index part of debugging dump file names. The resultant
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string must fit in fifteen bytes. The full filename will be the
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concatenation of: the prefix of the assembler file name, the string
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resulting from applying this format to an index number, and a string
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unique to each dump file kind, e.g. @samp{rtl}.
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If you do not define this macro, GCC will use @samp{.%02d.}. You should
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define this macro if using the default will create an invalid file name.
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@end ftable
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@node Host Misc
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@section Host Misc
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@cindex configuration file
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@cindex @file{xm-@var{machine}.h}
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@ftable @code
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@item FATAL_EXIT_CODE
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A C expression for the status code to be returned when the compiler
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exits after serious errors. The default is the system-provided macro
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@samp{EXIT_FAILURE}, or @samp{1} if the system doesn't define that
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macro. Define this macro only if these defaults are incorrect.
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@item SUCCESS_EXIT_CODE
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A C expression for the status code to be returned when the compiler
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exits without serious errors. (Warnings are not serious errors.) The
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default is the system-provided macro @samp{EXIT_SUCCESS}, or @samp{0} if
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the system doesn't define that macro. Define this macro only if these
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defaults are incorrect.
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@item USE_C_ALLOCA
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Define this macro if GCC should use the C implementation of @code{alloca}
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provided by @file{libiberty.a}. This only affects how some parts of the
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compiler itself allocate memory. It does not change code generation.
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When GCC is built with a compiler other than itself, the C @code{alloca}
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is always used. This is because most other implementations have serious
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bugs. You should define this macro only on a system where no
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stack-based @code{alloca} can possibly work. For instance, if a system
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has a small limit on the size of the stack, GCC's builtin @code{alloca}
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will not work reliably.
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@item COLLECT2_HOST_INITIALIZATION
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If defined, a C statement (sans semicolon) that performs host-dependent
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initialization when @code{collect2} is being initialized.
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@item GCC_DRIVER_HOST_INITIALIZATION
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If defined, a C statement (sans semicolon) that performs host-dependent
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initialization when a compilation driver is being initialized.
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@item SMALL_ARG_MAX
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Define this macro if the host system has a small limit on the total
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size of an argument vector. This causes the driver to take more care
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not to pass unnecessary arguments to subprocesses.
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@end ftable
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In addition, if @command{configure} generates an incorrect definition of
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any of the macros in @file{auto-host.h}, you can override that
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definition in a host configuration header. If you need to do this,
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first see if it is possible to fix @command{configure}.
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