| 1997-06-20 |
| |
| This directory contains the version 0.5.21 release of the GNU Fortran |
| compiler. The GNU Fortran compiler is free software. See the file |
| COPYING.g77 for copying permission. |
| |
| * IMPORTANT: Things you _must_ do are marked with a * at the beginning of |
| the line in this file!!! |
| |
| This README is for GNU Fortran, and describes the files in the f/ |
| directory. The f/ directory is intended to be a subdirectory of a |
| gcc source tree. These directories are referred to below as gcc/, |
| which is the top-level directory containing the gcc back end, the |
| gcc C front end, and other non-Fortran files, and gcc/f/, which |
| contains all of the Fortran files. |
| |
| * Note, if this is an egcs release, all the installation information |
| which follows is not needed. It is provided for historical reference |
| only. |
| |
| * To build GNU Fortran, you must have a source distribution of gcc |
| version 2.7.2.2. Do not attempt to use any other version |
| of gcc, because this version of g77 is designed to work only with |
| gcc version 2.7.2.2. |
| |
| * Note that you must have source copies of these gcc distributions!! |
| You cannot build g77 just using binaries of gcc. Also, unless you |
| are an expert, avoid using any distribution of gcc not identical to |
| the one distributed by the FSF -- for example, using a special version |
| modified to produce better code for the Pentium (sometimes labeled |
| gcc-i2.6.3 -- note the `i') will not work with this distribution of g77. |
| |
| If you have just unpacked the g77 distribution, before proceeding, |
| you must merge the contents of the g77 distribution with the appropriate |
| gcc distribution on your system before proceeding. |
| |
| * Read and follow the instructions in g77-0.5.21/f/INSTALL that |
| explain how to merge a g77 source directory into a gcc source |
| directory. You can use Info to read the same installation |
| instructions via: |
| |
| info -f g77-0.5.21/f/g77.info -n Unpacking |
| |
| The resulting directory layout includes the following, where gcc/ might be |
| a link to, for example, gcc-2.7.2.2/: |
| |
| gcc/ Non-Fortran files in gcc (not part of g77*.tar) |
| gcc/README.g77 This file |
| gcc/f/ GNU Fortran front end |
| gcc/f/gbe/ Patches required for gcc back end versions |
| gcc/f/runtime/ libf2c configuration and f2c.h file generation |
| gcc/f/runtime/libF77/ Non-I/O portion of libf2c |
| gcc/f/runtime/libI77/ I/O portion of libf2c |
| gcc/f/runtime/libU77/ Additional interfaces to libc for libf2c |
| |
| gcc/f/ as a whole contains the program GNU Fortran (g77), plus a portion |
| of the separate program f2c, which is in gcc/f/runtime. NOTE: The f2c |
| code is not part of the program g77, just distributed with it. |
| |
| This directory is named gcc/f/ because it, along with its contents, is |
| designed to be a subdirectory of a GNU CC (gcc) development directory. I.e. |
| when a gcc distribution is unpacked into a directory (named gcc/ for |
| example), it typically contains subdirectories like gcc/config/ and |
| gcc/cp/. The latter is the subdirectory for the GNU C++ (g++) program. |
| |
| Similarly, the g77 directory f/ is designed to be placed in gcc/ so that |
| it becomes the subdirectory gcc/f/. g77 is distributed as g77-someversion/f/ |
| so that unpacking the g77 distribution is done in the normal GNU way, |
| resulting in a directory having the version number in the name. However, |
| to build g77, the g77 distribution must be merged with an appropriate gcc |
| distribution, normally in a gcc directory, before configuring, building, |
| and installing g77. |
| |
| Applying g77 patches in the form of .diff files is done by typing |
| "patch -p1 -d gcc" (where gcc/f/ is the active version). That is, |
| g77 patches are distributed in the same form, and at the same directory |
| level, as patches to the gcc distribution. |
| |
| gcc/f/ has text files that document the Fortran compiler, source |
| files for the GNU Fortran Front End (FFE), and some other stuff. |
| |
| gcc/f/gbe/ has patch files for various versions of gcc, primarily |
| needed to patch the GNU compiler Back End (GBE) to fix and improve it |
| for use with g77. If a patch file exists for the version of gcc you |
| want to build along with g77, you MUST apply the patch before building |
| g77 with that version or g77 will not build or work properly.* |
| |
| * Read gcc/f/gbe/README for more information. |
| |
| gcc/f/runtime/ contains the run-time libraries for the f2c program, also used |
| by g77, and referred to as libf2c (though libf2c is really a combination of |
| two distinct libraries, libF77 and libI77 -- in g77, this distinction is |
| not made, and, further, Dave Love's implementation of libU77 is added |
| to the mix). This separate subdirectory is not part of the program g77, just |
| distributed with it. Some new files have been added to this subdirectory |
| and some minor changes made to the files contained therein, to fix some |
| bugs and facilitate automatic configuration, building, and installation of |
| libf2c for use by g77 users. See gcc/f/runtime/README for more information. |
| |
| gcc/f/BUGS lists some important bugs known to be in g77. Or: |
| |
| info -f gcc/f/g77.info -n "Actual Bugs" |
| |
| gcc/f/ChangeLog lists recent changes to g77 internals. |
| |
| gcc/f/INSTALL describes how to build and install GNU Fortran. Or: |
| |
| info -f gcc/f/g77.info -n Installation |
| |
| gcc/f/NEWS contains the per-release changes (not just user-visible ones |
| seen in gcc/f/DOC) listed in the ~fortran/.plan file. Or: |
| |
| info -f gcc/f/g77.info -n News |
| |
| * Read gcc/f/BUGS, gcc/f/INSTALL, and gcc/f/NEWS at the very least! |
| All users of g77 (not just installers) should read gcc/f/g77.info* |
| as well, using the "more" command if the "info" command is |
| unavailable or they aren't accustomed to using it. |
| |
| If you want to get into the FFE code, which lives entirely in gcc/f/, here |
| are a few clues. The file g77.c is the stand-alone source file for the |
| `g77' command driver only -- this just invokes the `gcc' command, so it has |
| nothing to do with the rest of the code in g77. Most of the code |
| ends up in an executable named `f771', which does the actual compiling, |
| so it has the FFE merged with the gcc back end. |
| |
| The file parse.c is the source file for main() for a stand-alone FFE and |
| yyparse() for f771. (Stand-alone building of the FFE doesn't work these days.) |
| The file top.c contains the top-level FFE function ffe_file and it (along |
| with top.h) define all ffe_[a-z].*, ffe[A-Z].*, and FFE_[A-Za-z].* symbols. |
| The file fini.c is a main() program that is used when building the FFE to |
| generate C header and source files for recognizing keywords. The files |
| malloc.c and malloc.h comprise a memory manager that defines all |
| malloc_[a-z].*, malloc[A-Z].*, and MALLOC_[A-Za-z].* symbols. All other |
| modules named <xyz> are comprised of all files named <xyz>*.<ext> and |
| define all ffe<xyz>_[a-z].*, ffe<xyz>[A-Z].*, and FFE<XYZ>_[A-Za-z].* symbols. |
| If you understand all this, congratulations -- it's easier for me to remember |
| how it works than to type in these grep patterns (such as they are). But it |
| does make it easy to find where a symbol is defined -- for example, |
| the symbol "ffexyz_set_something" would be defined in xyz.h and implemented |
| there (if it's a macro) or in xyz.c. |
| |
| The "porting" files of note currently are: proj.h, which defines the |
| "language" used by all the other source files (the language being |
| Standard C plus some useful things like ARRAY_SIZE and such) -- change |
| this file when you find your system doesn't properly define a Standard C |
| macro or function, for example; target.h and target.c, which describe |
| the target machine in terms of what data types are supported, how they are |
| denoted (what C type does an INTEGER*8 map to, for example), how to convert |
| between them, and so on (though as of 0.5.3, more and more of this information |
| is being dynamically configured by ffecom_init_0); com.h and com.c, which |
| interface to the target back end (currently only FFE stand-alone and the GBE); |
| ste.c, which contains code for implementing recognized executable statements |
| in the target back end (again currently either FFE or GBE); src.h and src.c, |
| which describe information on the format(s) of source files (like whether |
| they are never to be processed as case-insensitive with regard to Fortran |
| keywords); and proj.c, which contains whatever code is needed to support |
| the language defined by proj.h. |
| |
| If you want to debug the f771 executable, for example if it crashes, |
| note that the global variables "lineno" and "input_filename" are set |
| to reflect the current line being read by the lexer during the first-pass |
| analysis of a program unit and to reflect the current line being |
| processed during the second-pass compilation of a program unit. If |
| an invocation of the function ffestd_exec_end() is on the stack, |
| the compiler is in the second pass, otherwise it is in the first. |
| (This information might help you reduce a test case and/or work around |
| a bug in g77 until a fix is available.) |
| |
| Any questions or comments on these topics, email egcs@cygnus.com |