264 lines
12 KiB
Plaintext
264 lines
12 KiB
Plaintext
1998-08-11
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This directory contains the egcs variant of version 0.5.24 of the
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GNU Fortran compiler (g77). The GNU Fortran compiler is free software.
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See the file COPYING.g77 for copying permission.
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Currently, two variants of g77 exist. One is the Free Software Foundation
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(FSF) variant. The other is the egcs variant. As of egcs version 1.1,
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these variants are kept fairly similar in most respects. Pertinent
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differences, such as the layout of the source code, are specified below.
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Below, `[FSF]' denotes information applicable to only the FSF variant of
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g77, while `[egcs]' denotes egcs-only information.
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* IMPORTANT: Things you *must* do (or avoid) are marked with a * at the
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beginning of the line in this file!!!
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The email address to which bugs are to be reported is either
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[FSF] <fortran@gnu.org> or [egcs] <egcs-bugs@cygnus.com>.
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* *DO NOT* send any email (reporting bugs, asking questions, etc.) to
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either of these addresses without *first* reading the g77 documentation.
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Use `info', Info mode in GNU Emacs, or a text viewer such as `more' to
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do this.
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The g77 documentation is in the source files named `g77.info',
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`g77.info-1', `g77.info-2', and so on in the `f' subdirectory. If these
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files are not present or you can't find them, contact the person or
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organization that put together the g77 distribution you are using (probably
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not the FSF or egcs), or ask your system administrator for help.
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This README applies to only the g77-specific portions of the source-code
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tree that contains it. These portions include:
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- The README.g77 and [FSF] COPYING.g77 files, in this directory, "this
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directory" being [FSF] the top-level directory containing a g77
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distribution or [egcs] the gcc/ subdirectory of an egcs distribution.
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- The g77 front end, in the f/ subdirectory of this directory.
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- The libg2c library, in [FSF] the f/runtime/ subdirectory of this
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directory or [egcs] the libf2c/ directory under the top-level
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directory of the egcs distribution.
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* To build g77, you must have a source distribution of [FSF] gcc
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version 2.8 or [egcs] egcs version 1.1. Do not attempt to use
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any other version of gcc or egcs, because this version of g77 is
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designed to work with only those versions.
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Note that you must have *source* copies of the gcc or egcs distribution!
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You cannot build g77 just using binaries of gcc or egcs. Also, unless
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you are an expert, avoid using any distribution of gcc or egcs not
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identical to the ones distributed by the FSF and Cygnus Support,
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respectively. The primary FSF distribution site is:
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<ftp://ftp.gnu.org/pub/gnu/>
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The primary egcs distribution site is:
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<ftp://ftp.cygnus.com/pub/egcs/>
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Both of these sites have approved mirror sites from which valid
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distributions also may be obtained.
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* Do not attempt to combine the egcs version of g77 with the FSF
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gcc distribution, or the FSF version of g77 with the egcs gcc
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distribution. Although the differences are minor, they might
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be sufficient to prevent g77 from building properly, or from
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working properly if the build appears to succeed.
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[FSF] g77 is distributed as g77-<version>/f/ so that unpacking the g77
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distribution is done in the normal GNU way, resulting in a directory having
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the version number in the name. However, to build g77, the g77 distribution
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must be merged with an appropriate gcc distribution, normally in a gcc
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source directory, before configuring, building, and installing g77.
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[FSF] If you have just unpacked the g77 distribution, before proceeding,
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you must merge the contents of the g77 distribution with the appropriate
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gcc distribution on your system.
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* [FSF] Read and follow the instructions in f/INSTALL that
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explain how to merge a g77 source directory into a gcc source
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directory. You can use Info to read the same installation
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instructions via:
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info -f f/g77.info -n Unpacking
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[FSF] The resulting directory layout includes the following, where gcc/
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might be a link to, for example, gcc-2.8.1/:
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gcc/ Non-g77 files in gcc
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gcc/COPYING.g77 A copy of the GPL, under which g77 is licensed
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gcc/README.g77 This file
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gcc/f/ GNU Fortran front end
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gcc/f/runtime/ libg2c configuration and g2c.h file generation
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gcc/f/runtime/libF77/ Non-I/O portion of libg2c
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gcc/f/runtime/libI77/ I/O portion of libg2c
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gcc/f/runtime/libU77/ Additional interfaces to libc for libg2c
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[FSF] Applying g77 patches in the form of .diff files is done by typing
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`patch -p1 -d gcc' (where gcc/ contains the f/ subdirectory). That is,
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g77 patches are distributed in the same form, and at the same directory
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level, as patches to the gcc distribution. (Note: make sure you're
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using GNU patch, version 2.5 or later! Other versions of patch
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have trouble with g77-related patches.)
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[egcs] The egcs version of g77 is distributed already merged with
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the rest of egcs (such as the gcc back end).
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[egcs] The resulting directory layout includes the following, where egcs/
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might be a link to, for example, egcs-1.1/:
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egcs/gcc/ Non-g77 files in gcc
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egcs/gcc/README.g77 This file
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egcs/gcc/f/ GNU Fortran front end
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egcs/libf2c/ libg2c configuration and g2c.h file generation
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egcs/libf2c/libF77/ Non-I/O portion of libg2c
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egcs/libf2c/libI77/ I/O portion of libg2c
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egcs/libf2c/libU77/ Additional interfaces to libc for libg2c
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[egcs] Applying g77-specific patches to egcs is done the same way as
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applying other egcs patches.
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Below, `libf2c/' shall denote [FSF] gcc/f/runtime/ or [egcs] egcs/libf2c/,
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while `f/' shall denote [FSF] the rest of gcc/f/ or [egcs] egcs/gcc/f/.
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Components of note in g77 are described below.
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f/ as a whole contains the program GNU Fortran (g77), while libf2c/
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contains a portion of the separate program f2c. Note: The libf2c
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code is not part of the program g77, just distributed with it.
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f/ contains text files that document the Fortran compiler, source
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files for the GNU Fortran Front End (FFE), and some other stuff.
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The g77 compiler code is placed in f/ because it, along with its contents,
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is designed to be a subdirectory of a GNU CC (gcc) source directory, gcc/,
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which is structured so that language-specific front ends can be "dropped
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in" as subdirectories. The C++ front end (g++), is an example of this --
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it resides in the cp/ subdirectory. Note that the C front end (also
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referred to as gcc) is an exception to this, as its source files reside
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in the gcc/ directory itself.
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libf2c/ contains the run-time libraries for the f2c program, also used
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by g77. These libraries normally referred to collectively as libf2c.
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When built as part of g77, libf2c is installed under the name libg2c to avoid
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conflict with any existing version of libf2c, and thus is often referred
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to as libg2c when the g77 version is specifically being referred to.
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The netlib version of libf2c/ contains two distinct libraries, libF77 and
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libI77, each in their own subdirectories. In g77, this distinction is not
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made, beyond maintaining the subdirectory structure in the source-code tree.
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libf2c/ is not part of the program g77, just distributed with it. It
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contains files not present in the official (netlib) version of libf2c,
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and also contains some minor changes made from libf2c, to fix some bugs,
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and to facilitate automatic configuration, building, and installation of
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libf2c (as libg2c) for use by g77 users.
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* See libf2c/README for more information, including licensing conditions
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governing distribution of programs containing code from libg2c.
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libg2c, g77's version of libf2c, adds Dave Love's implementation of
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libU77, in the libf2c/libU77/ directory. This library is distributed
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under the GNU Library General Public License (LGPL) -- see the
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file libf2c/libU77/COPYING.LIB for more information, as this license
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governs distribution conditions for programs containing code from
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this portion of the library.
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Files of note in g77 are described below.
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f/BUGS lists some important bugs known to be in g77. Or:
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info -f f/g77.info -n "Actual Bugs"
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f/ChangeLog lists recent changes to g77 internals.
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libf2c/ChangeLog lists recent changes to libg2c internals.
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[FSF] f/INSTALL describes how to build and install GNU Fortran. Or:
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info -f f/g77.info -n Installation
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f/NEWS contains the per-release changes. These include the user-visible
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changes described under "Changes" in the g77 documentation, plus internal
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changes of import. Or:
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info -f f/g77.info -n News
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* All users of g77 (not just installers) should read f/g77.info*
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as well, using the `more' command if neither the `info' command,
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nor GNU Emacs (with its Info mode), are available, or if they
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aren't yet accustomed to using these tools. Read f/BUGS and f/NEWS
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plus, if you are planning on building or installing the FSF version
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of g77, f/INSTALL, at the very least! All of these files are
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readable as "plain text" files.
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* Also see <ftp://alpha.gnu.org/g77.plan> for up-to-date information
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regarding g77 bug reports, known bugs, bug-fixes, and new versions.
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The rest of this file is of note to only those who wish to
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debug, modify, or test the FFE (in conjunction with the gcc back end).
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If you want to explore the FFE code, which lives entirely in f/, here
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are a few clues. The file g77spec.c contains the g77-specific source code
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for the `g77' command only -- this just forms a variant of the `gcc'
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command, so, just as the `gcc' command itself does not contain
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the C front end, the `g77' command does not contain the Fortran front
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end (FFE). The FFE code ends up in an executable named `f771', which
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does the actual compiling, so it contains the FFE plus the gcc back end
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(the latter to do most of the optimization, and the code generation).
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The file parse.c is the source file for main() for a stand-alone FFE and
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yyparse() for f771. (Stand-alone building of the FFE doesn't work these days.)
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The file top.c contains the top-level FFE function ffe_file and it (along
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with top.h) define all ffe_[a-z].*, ffe[A-Z].*, and FFE_[A-Za-z].* symbols.
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The file fini.c is a main() program that is used when building the FFE to
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generate C header and source files for recognizing keywords. The files
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malloc.c and malloc.h comprise a memory manager that defines all
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malloc_[a-z].*, malloc[A-Z].*, and MALLOC_[A-Za-z].* symbols. All other
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modules named <xyz> are comprised of all files named <xyz>*.<ext> and
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define all ffe<xyz>_[a-z].*, ffe<xyz>[A-Z].*, and FFE<XYZ>_[A-Za-z].* symbols.
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If you understand all this, congratulations -- it's easier for me to remember
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how it works than to type in these grep patterns (such as they are). But it
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does make it easy to find where a symbol is defined -- for example,
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the symbol "ffexyz_set_something" would be defined in xyz.h and implemented
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there (if it's a macro) or in xyz.c.
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The "porting" files of note currently are: proj.h, which defines the
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"language" used by all the other source files (the language being
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Standard C plus some useful things like ARRAY_SIZE and such) -- change
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this file when you find your system doesn't properly define a Standard C
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macro or function, for example; target.h and target.c, which describe
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the target machine in terms of what data types are supported, how they are
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denoted (what C type does an INTEGER*8 map to, for example), how to convert
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between them, and so on (though as of 0.5.3, more and more of this information
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is being dynamically configured by ffecom_init_0); com.h and com.c, which
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interface to the target back end (currently only FFE stand-alone and the GBE);
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ste.c, which contains code for implementing recognized executable statements
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in the target back end (again currently either FFE or GBE); src.h and src.c,
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which describe information on the format(s) of source files (such as whether
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they are never to be processed as case-insensitive with regard to Fortran
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keywords); and proj.c, which contains whatever code is needed to support
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the language defined by proj.h.
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If you want to debug the f771 executable, for example if it crashes,
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note that the global variables "lineno" and "input_filename" are set
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to reflect the current line being read by the lexer during the first-pass
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analysis of a program unit and to reflect the current line being
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processed during the second-pass compilation of a program unit. If
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an invocation of the function ffestd_exec_end() is on the stack,
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the compiler is in the second pass, otherwise it is in the first.
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(This information might help you reduce a test case and/or work around
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a bug in g77 until a fix is available.)
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Any questions or comments on these topics? Read the g77 documentation!
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