===================================================================
@@ -102,6 +102,7 @@ one is not the default.
and register usage.
* Interoperability Options:: Options for interoperability with other
languages.
+* File Output Options:: Which files the compiler generates during compilation.
* Environment Variables:: Environment variables that affect @command{gfortran}.
@end menu
@@ -178,6 +179,10 @@ and warnings}.
@xref{Interoperability Options,,Options for interoperability}.
@gccoptlist{-fc-prototypes}
+@item File Output Options
+@xref{File Output Options,,Options for determining output of files}.
+@gccoptlist{-fwrite-module-files}
+
@item Code Generation Options
@xref{Code Gen Options,,Options for code generation conventions}.
@gccoptlist{-faggressive-function-elimination -fblas-matmul-limit=@var{n} @gol
@@ -791,9 +796,12 @@ messages produced.
@item -fsyntax-only
@opindex @code{fsyntax-only}
@cindex syntax checking
-Check the code for syntax errors, but do not actually compile it. This
-will generate module files for each module present in the code, but no
-other output file.
+Check the code for syntax errors, but do not actually compile it.
+This will generate module files for each module present in the code,
+but no other output file. Using this option, it is possible to
+generate module files much faster. Together with the
+@option{-fwrite-module-files} options, it can be used for speeding up
+compilation processes.
@item -Wpedantic
@itemx -pedantic
@@ -1865,6 +1873,44 @@ where the C code intended for interoperating with
then uses @code{#include "foo.h"}.
@end table
+@node File Output Options
+@section Which files the compiler generates during compilation
+
+@table @asis
+
+@item -fwrite-module-files
+@opindex @code{write-module-files}
+@cindex Writing out module files
+This option will write out a @file{foo.mod} file when the module
+@code{foo} has been successfully compiled. This file will be read in
+later when @code{use foo} is encountered in the code.
+Writing out the file is the default.
+
+The negative form, @option{-fno-write-module-files}, supresses writing
+of module files. This can be useful when the module files have
+previously been generated with @option{-fsyntax-only}, for example to
+support a more parallel make process. When code has been changed and
+@option{-fno-write-module-files} is used, it is possible to generate
+inconsistent module files, which will lead to hard-to-find bugs. Use
+with care.
+
+An example of how this could be used is the following Makefile
+snippet. It assumes that @file{foo.f90} contains a module @code{foo},
+which is used by module @code{bar} in @file{bar.f90}. This would
+allow parallel compilation of @file{foo.f90} and @file{bar.f90}.
+
+@smallexample
+foo.mod: foo.f90
+ gfortran -fmodule-files=only foo.f90
+
+foo.o: foo.f90
+ gfortran -fmodule-files=no foo.f90
+
+bar.o: bar.f90 foo.mod
+ gfortran -c bar.f90
+@end smallexample
+@end table
+
@node Environment Variables
@section Environment variables affecting @command{gfortran}
@cindex environment variable
===================================================================
@@ -722,6 +722,10 @@ frepack-arrays
Fortran Var(flag_repack_arrays)
Copy array sections into a contiguous block on procedure entry.
+fwrite-module-files
+Fortran Var(flag_write_module_files) Init(1)
+Write module files.
+
fcoarray=
Fortran RejectNegative Joined Enum(gfc_fcoarray) Var(flag_coarray) Init(GFC_FCOARRAY_NONE)
-fcoarray=<none|single|lib> Specify which coarray parallelization should be used.
===================================================================
@@ -6284,7 +6284,9 @@ loop:
gfc_get_errors (NULL, &errors);
if (s.state == COMP_MODULE || s.state == COMP_SUBMODULE)
{
- gfc_dump_module (s.sym->name, errors_before == errors);
+ if (flag_write_module_files)
+ gfc_dump_module (s.sym->name, errors_before == errors);
+
gfc_current_ns->derived_types = gfc_derived_types;
gfc_derived_types = NULL;
goto prog_units;
Hello world, the attached patch adds a -fwrite-module-files options, but the main point is that it adds its opposite, -fno-write-module-files. This has advantages in parallel compiling, as it is quite fast to generate a module file with -fsyntax-only, and a subsequent compilation with -fno-write-module-files will not overwrite this. Yes, submodules also address some of the same issues. For details, see the PR. Regression-tested. Documentation tested with "make info", "make dvi" and "make pdf". Test case... well, it works when run by hand, and I'm not sure how to check for the presence or absence of a module file in dejagnu. OK for trunk? Regards Thomas 2019-01-13 Thomas Koenig <tkoenig@gcc.gnu.org> PR fortran/82215 * invoke.texi: Document -fwrite-module-files. * lang.opt: Add -fwrite-module-files. * parse.c (gfc_parse_file): Write module only if -f-write-module-files is in effect.