g77 - GNU project Fortran Compiler (v0.5.24)
g77 [option | filename ]...
The information in this man page is an extract from the full documentation
of the GNU Fortran compiler (version 0.5.24), and is limited to
the meaning of some of the options.
This man page is not up to date, since no volunteers want to maintain
it. If you find a discrepancy between the man page and the software,
please check the Info file, which is the authoritative documentation.
If we find that the things in this man page that are out of date cause
significant confusion or complaints, we will stop distributing the man
page. The alternative, updating the man page when we update the Info
file, is impractical because the rest of the work of maintaining GNU
Fortran leaves us no time for that. The GNU project regards man pages
as obsolete and should not let them take time away from other things.
For complete and current documentation, refer to the Info file `g77' or
the manual Using and Porting GNU Fortran (for version 0.5.24). Both
are made from the Texinfo source file g77.texi.
If your system has the `info' command installed, the command `info g77'
should work, unless g77 has not been properly installed. If your system
lacks `info', or you wish to avoid using it for now, the command
`more /usr/info/g77.info*' should work, unless g77 has not been properly
If g77 has not been properly installed, so that you cannot easily
access the Info file for it, ask your system administrator, or the
installer of g77 (if you know who that is) to fix the problem.
The C and F77 compilers are integrated; g77 is a program to call gcc
with options to recognize programs written in Fortran (ANSI FORTRAN 77,
also called F77). gcc processes input files through one or more of
four stages: preprocessing, compilation, assembly, and linking. This
man page contains full descriptions for only F77-specific aspects of
the compiler, though it also contains summaries of some general-purpose
options. For a fuller explanation of the compiler, see gcc(1).
For complete documentation on GNU Fortran, type `info g77'.
F77 source files use the suffix `.f', `.for', or `.FOR'; F77 files to
be preprocessed by cpp(1) use the suffix `.F', `.fpp', or `.FPP'; Ratfor
source files use the suffix `.r' (though ratfor itself is not supplied
as part of g77).
There are many command-line options, including options to control
details of optimization, warnings, and code generation, which are common
to both gcc and g77. For full information on all options, see
Options must be separate: `-dr' is quite different from `-d -r '.
Most `-f' and `-W' options have two contrary forms: -fname and
-fno-name (or -Wname and -Wno-name). Only the non-default forms are
-c Compile or assemble the source files, but do not link. The compiler
output is an object file corresponding to each source
Define macro macro with the string `1' as its definition.
Define macro macro as defn.
-E Stop after the preprocessing stage; do not run the compiler
proper. The output is preprocessed source code, which is sent
to the standard output.
-g Produce debugging information in the operating system's native
format (for DBX or SDB or DWARF). GDB also can work with this
debugging information. On most systems that use DBX format,
`-g' enables use of extra debugging information that only GDB
Unlike most other Fortran compilers, GNU Fortran allows you to
use `-g' with `-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
-Idir Append directory dir to the list of directories searched for
-Ldir Add directory dir to the list of directories to be searched for
Use the library named library when linking.
Do not search the standard system directories for header files.
Only the directories you have specified with -I options (and the
current directory, if appropriate) are searched.
-O Optimize. Optimizing compilation takes somewhat more time, and
a lot more memory for a large function. See the GCC documentation
for further optimisation options. Loop unrolling, in particular,
may be worth investigating for typical numerical Fortran
Place output in file file.
-S Stop after the stage of compilation proper; do not assemble.
The output is an assembler code file for each non-assembler
input file specified.
Undefine macro macro.
-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. The version numbers of g77 itself and the GCC distribution
on which it is based are distinct.
-Wall Issue warnings for conditions which pertain to usage that we
recommend avoiding and that we believe is easy to avoid, even in
conjunction with macros.
file.h C header (preprocessor) file
file.f Fortran source file
file.for Fortran source file
file.FOR Fortran source file
file.F preprocessed Fortran source file
file.fpp preprocessed Fortran source file
file.FPP preprocessed Fortran source file
file.r Ratfor source file (ratfor not included)
file.s assembly language file
file.o object file
a.out link edited output
TMPDIR/cc* temporary files
LIBDIR/libg2c.a Fortran run-time library
LIBDIR/libgcc.a GCC subroutine library
/lib/crt[01n].o start-up routine
/lib/libc.a standard C library, see intro(3)
/usr/include standard directory for #include files
LIBDIR/include standard gcc directory for #include
LIBDIR is usually /usr/local/lib/machine/version.
TMPDIR comes from the environment variable TMPDIR (default /usr/tmp if
available, else /tmp).
gcc(1), cpp(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1).
`g77', `gcc', `cpp', `as', `ld', and `gdb' entries in info.
Using and Porting GNU Fortran (for version 0.5.24), James Craig Burley;
Using and Porting GNU CC (for version 2.0), Richard M. Stallman; The C
Preprocessor, Richard M. Stallman; Debugging with GDB: the GNU Source-
Level Debugger, Richard M. Stallman and Roland H. Pesch; Using as: the
GNU Assembler, Dean Elsner, Jay Fenlason & friends; gld: the GNU
linker, Steve Chamberlain and Roland Pesch.
For instructions on how to report bugs, type `info g77 -n Bugs'.
Copyright (c) 1991-1998 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a permission
notice identical to this one.
Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be included in translations
approved by the Free Software Foundation instead of in the original
See the GNU CC Manual for the contributors to GNU CC. See the GNU Fortran
Manual for the contributors to GNU Fortran.
GNU Tools 1999-02-14 G77(1)
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