Use AC_FC_SRCEXT in Automake

[Ralf Wildenhues]

Hello Steven, everyone,

Steven suggested (quite) a while ago[1] to exploit AC_FC_SRCEXT in
Automake in two ways:
- add the computed flag to the compilation rule,
- infer from the macro argument that files with this extensions
  should be compiled with $(FC) rather than $(F77).

I'm not yet sure about the desired semantics:

1) Should $(FCFLAGS_foo) be added to the compile command for Fortran
   sources ending with extension .foo
    - only if AC_FC_SRCEXT(foo) was given, or
    - in any case?
  (`foo' being a placeholder for some suitable extension)

2) Should `AC_FC_SRCEXT(f)' globally override Automake to use $(FC) for
   all files with extension .f, or should we have a thin wrapper
   AM_FC_SRCEXT that calls AC_FC_SRCEXT($@) _and_ overrides extension
   mapping (would be a bit more backwards-compatible probably)?
   Or even none of this overriding stuff?

The incomplete patch below chooses the first answer for both questions.
Based on feedback I can supply documentation and finish my tests.

Notes/questions:
- We add %SOURCEFLAG% to all compile commands in depend2, although
  strictly for FC it would suffice for a subset of rules.  I think
  it is better to be consistent here.
- The expansion of %SOURCEFLAG% contains a space, in order to not
  affect unrelated compile commands' spacing.
- AC_FC_SRCEXT tracing is enabled in autoconf-2.60/lib/autom4te.in,
  needed for the change to scan_autoconf_traces.  :-)
- The depend2.am patch conflicts (trivially) with the pending patch
  in PR 501.
- The patch contains only incomplete changes to automake.texi that
  need rewriting based on consensus for above.
- I'd like to not claim full Fortran 9x support: even after this and
  following stuff, modules handling (install/clean) and dependency
  tracking will not be automatic yet.
- Is it too dirty to use a global such as %sourceflags for Automake
  style?

[1] http://lists.gnu.org/archive/html/automake/2005-06/msg00012.html

Cheers,
Ralf

        * lib/am/depend2.am (%SOURCEFLAG%): New substitution, goes
        right before the expanded source file name.
        * automake.in (%sourceflags): New global: per-extension flag
        to denote that the next compiler argument is the source file.
        (scan_autoconf_traces): Trace AC_FC_SRCEXT; initialize
        %sourceflags accordingly; override extension map to use FC.
        (handle_languages): pass flag in SOURCEFLAG.
        * doc/automake.texi (): ...
        Suggested by Steven G. Johnson <address@hidden>.

Index: automake.in
===================================================================
RCS file: /cvs/automake/automake/automake.in,v
retrieving revision 1.1630
diff -u -r1.1630 automake.in
--- automake.in 30 Aug 2006 18:50:38 -0000      1.1630
+++ automake.in 30 Aug 2006 19:28:29 -0000
@@ -415,6 +415,9 @@
 # Maps each linker variable onto a language object.
 my %link_languages = ();
 
+# maps extensions to needed source flags.
+my %sourceflags = ();
+
 # List of targets we must always output.
 # FIXME: Complete, and remove falsely required targets.
 my %required_targets =
@@ -1223,6 +1228,7 @@
                         'AMDEP'   => $AMDEP,
                         'FASTDEP' => $FASTDEP,
                         '-c'      => $lang->compile_flag || '',
+                        SOURCEFLAG => $sourceflags{$ext} || '',
                         # These are not used, but they need to be defined
                         # so &transform do not complain.
                         SUBDIROBJ     => 0,
@@ -4775,6 +4783,7 @@
                AC_CONFIG_HEADERS => 1,
                AC_CONFIG_LIBOBJ_DIR => 1,
                AC_CONFIG_LINKS => 1,
+               AC_FC_SRCEXT => 1,
                AC_INIT => 0,
                AC_LIBSOURCE => 1,
                 AC_REQUIRE_AUX_FILE => 1,
@@ -4886,6 +4898,18 @@
              push @config_links, $spec;
            }
        }
+      elsif ($macro eq 'AC_FC_SRCEXT')
+        {
+         my $lang = $languages{'fc'};
+         my $suffix = $args[1];
+         my $ext = '.' . $suffix;
+         $extension_map{$ext} = 'fc';
+         ($sourceflags{$ext} = '$(FCFLAGS_' . $ext . ') ') =~ s/\.//;
+         foreach my $dest (&{$lang->output_extensions} ($suffix))
+           {
+             register_suffix_rule (INTERNAL, $suffix, $dest);
+           }
+       }
       elsif ($macro eq 'AC_INIT')
         {
          if (defined $args[2])
Index: doc/automake.texi
===================================================================
RCS file: /cvs/automake/automake/doc/automake.texi,v
retrieving revision 1.150
diff -u -r1.150 automake.texi
--- doc/automake.texi   28 Aug 2006 16:04:24 -0000      1.150
+++ doc/automake.texi   30 Aug 2006 19:28:36 -0000
@@ -2887,6 +2887,11 @@
 languages that include Fortran 77 (@pxref{Mixing Fortran 77 With C and
 C++}).  @xref{Macros, , Autoconf macros supplied with Automake}.
 
address@hidden AC_FC_SRCEXT
+Automake will add the flags computed by @code{AC_FC_SRCEXT} to compilation
+of files with the respective source extension (@pxref{Fortran Compiler, ,
+Fortran Compiler Characteristics, autoconf, The Autoconf Manual}).
+
 @item AC_PROG_FC
 This is required if any Fortran 90/95 source is included.  This macro is
 distributed with Autoconf version 2.58 and later.  @xref{Particular
@@ -6405,7 +6426,7 @@
 @cindex Fortran 9x support
 @cindex Support for Fortran 9x
 
-Automake includes full support for Fortran 9x.
+Automake includes support for Fortran 9x.
 
 Any package including Fortran 9x code must define the output variable
 @code{FC} in @file{configure.ac}; the simplest way to do this is to use
@@ -6445,13 +6466,22 @@
 @subsection Compiling Fortran 9x Files
 
 @file{N.o} is made automatically from @file{N.f90} or @file{N.f95}
-by running the Fortran 9x compiler.  The precise command used
-is as follows:
+by running the Fortran 9x compiler.
+
+If you use the Autoconf macro @code{AC_FC_SRCEXT(f90)} which computes
+the value of @samp{FCFLAGS_f90}, Automake will add this to the compile
+command (@pxref{Fortran Compiler, , Fortran Compiler Characteristics,
+autoconf, The Autoconf Manual}), and likewise with @code{f95}.
+
+The precise command used is then as follows:
 
 @table @file
 
address@hidden .f9x
address@hidden(FC) -c $(AM_FCFLAGS) $(FCFLAGS)}
address@hidden .f90
address@hidden(FC) $(AM_FCFLAGS) $(FCFLAGS) -c $(FCFLAGS_f90) $<}
+
address@hidden .f95
address@hidden(FC) $(AM_FCFLAGS) $(FCFLAGS) -c $(FCFLAGS_f95) $<}
 
 @end table
 
Index: lib/am/depend2.am
===================================================================
RCS file: /cvs/automake/automake/lib/am/depend2.am,v
retrieving revision 1.60
diff -u -r1.60 depend2.am
--- lib/am/depend2.am   23 Mar 2006 06:35:15 -0000      1.60
+++ lib/am/depend2.am   30 Aug 2006 19:28:37 -0000
@@ -65,9 +65,9 @@
 if %FASTDEP%
 ## In fast-dep mode, we can always use -o.
 ## For non-suffix rules, we must emulate a VPATH search on %SOURCE%.
-?!GENERIC?     if %COMPILE% -MT %OBJ% -MD -MP -MF "%DEPBASE%.Tpo" %-c% -o 
%OBJ% `test -f '%SOURCE%' || echo '$(srcdir)/'`%SOURCE%; \
+?!GENERIC?     if %COMPILE% -MT %OBJ% -MD -MP -MF "%DEPBASE%.Tpo" %-c% -o 
%OBJ% %SOURCEFLAG%`test -f '%SOURCE%' || echo '$(srcdir)/'`%SOURCE%; \
 ?SUBDIROBJ??GENERIC?   depbase=`echo %OBJ% | sed 
's|[^/]*$$|$(DEPDIR)/&|;s|\.o$$||'`; \
-?GENERIC?      if %COMPILE% -MT %OBJ% -MD -MP -MF "%DEPBASE%.Tpo" %-c% -o 
%OBJ% %SOURCE%; \
+?GENERIC?      if %COMPILE% -MT %OBJ% -MD -MP -MF "%DEPBASE%.Tpo" %-c% -o 
%OBJ% %SOURCEFLAG%%SOURCE%; \
        then mv -f "%DEPBASE%.Tpo" "%DEPBASE%.Po"; else rm -f "%DEPBASE%.Tpo"; 
exit 1; fi
 else !%FASTDEP%
 if %AMDEP%
@@ -75,12 +75,12 @@
        DEPDIR=$(DEPDIR) $(%FPFX%DEPMODE) $(depcomp) @AMDEPBACKSLASH@
 endif %AMDEP%
 if %?GENERIC%
-?-o?   %COMPILE% %-c% %-o% %OBJ% %SOURCE%
-?!-o?  %COMPILE% %-c% %SOURCE%
+?-o?   %COMPILE% %-c% %-o% %OBJ% %SOURCEFLAG%%SOURCE%
+?!-o?  %COMPILE% %-c% %SOURCEFLAG%%SOURCE%
 else !%?GENERIC%
 ## For non-suffix rules, we must emulate a VPATH search on %SOURCE%.
-?-o?   %COMPILE% %-c% %-o% %OBJ% `test -f '%SOURCE%' || echo 
'$(srcdir)/'`%SOURCE%
-?!-o?  %COMPILE% %-c% `test -f '%SOURCE%' || echo '$(srcdir)/'`%SOURCE%
+?-o?   %COMPILE% %-c% %-o% %OBJ% %SOURCEFLAG%`test -f '%SOURCE%' || echo 
'$(srcdir)/'`%SOURCE%
+?!-o?  %COMPILE% %-c% %SOURCEFLAG%`test -f '%SOURCE%' || echo 
'$(srcdir)/'`%SOURCE%
 endif !%?GENERIC%
 endif !%FASTDEP%
 
@@ -89,9 +89,9 @@
 if %FASTDEP%
 ## In fast-dep mode, we can always use -o.
 ## For non-suffix rules, we must emulate a VPATH search on %SOURCE%.
-?!GENERIC?     if %COMPILE% -MT %OBJOBJ% -MD -MP -MF "%DEPBASE%.Tpo" %-c% -o 
%OBJOBJ% `if test -f '%SOURCE%'; then $(CYGPATH_W) '%SOURCE%'; else 
$(CYGPATH_W) '$(srcdir)/%SOURCE%'; fi`; \
+?!GENERIC?     if %COMPILE% -MT %OBJOBJ% -MD -MP -MF "%DEPBASE%.Tpo" %-c% -o 
%OBJOBJ% %SOURCEFLAG%`if test -f '%SOURCE%'; then $(CYGPATH_W) '%SOURCE%'; else 
$(CYGPATH_W) '$(srcdir)/%SOURCE%'; fi`; \
 ?SUBDIROBJ??GENERIC?   depbase=`echo %OBJ% | sed 
's|[^/]*$$|$(DEPDIR)/&|;s|\.obj$$||'`; \
-?GENERIC?      if %COMPILE% -MT %OBJOBJ% -MD -MP -MF "%DEPBASE%.Tpo" %-c% -o 
%OBJOBJ% `$(CYGPATH_W) '%SOURCE%'`; \
+?GENERIC?      if %COMPILE% -MT %OBJOBJ% -MD -MP -MF "%DEPBASE%.Tpo" %-c% -o 
%OBJOBJ% %SOURCEFLAG%`$(CYGPATH_W) '%SOURCE%'`; \
        then mv -f "%DEPBASE%.Tpo" "%DEPBASE%.Po"; else rm -f "%DEPBASE%.Tpo"; 
exit 1; fi
 else !%FASTDEP%
 if %AMDEP%
@@ -99,12 +99,12 @@
        DEPDIR=$(DEPDIR) $(%FPFX%DEPMODE) $(depcomp) @AMDEPBACKSLASH@
 endif %AMDEP%
 if %?GENERIC%
-?-o?   %COMPILE% %-c% %-o% %OBJOBJ% `$(CYGPATH_W) '%SOURCE%'`
-?!-o?  %COMPILE% %-c% `$(CYGPATH_W) '%SOURCE%'`
+?-o?   %COMPILE% %-c% %-o% %OBJOBJ% %SOURCEFLAG%`$(CYGPATH_W) '%SOURCE%'`
+?!-o?  %COMPILE% %-c% %SOURCEFLAG%`$(CYGPATH_W) '%SOURCE%'`
 else !%?GENERIC%
 ## For non-suffix rules, we must emulate a VPATH search on %SOURCE%.
-?-o?   %COMPILE% %-c% %-o% %OBJOBJ% `if test -f '%SOURCE%'; then $(CYGPATH_W) 
'%SOURCE%'; else $(CYGPATH_W) '$(srcdir)/%SOURCE%'; fi`
-?!-o?  %COMPILE% %-c% `if test -f '%SOURCE%'; then $(CYGPATH_W) '%SOURCE%'; 
else $(CYGPATH_W) '$(srcdir)/%SOURCE%'; fi`
+?-o?   %COMPILE% %-c% %-o% %OBJOBJ% %SOURCEFLAG%`if test -f '%SOURCE%'; then 
$(CYGPATH_W) '%SOURCE%'; else $(CYGPATH_W) '$(srcdir)/%SOURCE%'; fi`
+?!-o?  %COMPILE% %-c% %SOURCEFLAG%`if test -f '%SOURCE%'; then $(CYGPATH_W) 
'%SOURCE%'; else $(CYGPATH_W) '$(srcdir)/%SOURCE%'; fi`
 endif !%?GENERIC%
 endif !%FASTDEP%
 endif %?NONLIBTOOL%
@@ -115,9 +115,9 @@
 if %FASTDEP%
 ## In fast-dep mode, we can always use -o.
 ## For non-suffix rules, we must emulate a VPATH search on %SOURCE%.
-?!GENERIC?     if %LTCOMPILE% -MT %LTOBJ% -MD -MP -MF "%DEPBASE%.Tpo" %-c% -o 
%LTOBJ% `test -f '%SOURCE%' || echo '$(srcdir)/'`%SOURCE%; \
+?!GENERIC?     if %LTCOMPILE% -MT %LTOBJ% -MD -MP -MF "%DEPBASE%.Tpo" %-c% -o 
%LTOBJ% %SOURCEFLAG%`test -f '%SOURCE%' || echo '$(srcdir)/'`%SOURCE%; \
  ?SUBDIROBJ??GENERIC?  depbase=`echo %OBJ% | sed 
's|[^/]*$$|$(DEPDIR)/&|;s|\.lo$$||'`; \
-?GENERIC?      if %LTCOMPILE% -MT %LTOBJ% -MD -MP -MF "%DEPBASE%.Tpo" %-c% -o 
%LTOBJ% %SOURCE%; \
+?GENERIC?      if %LTCOMPILE% -MT %LTOBJ% -MD -MP -MF "%DEPBASE%.Tpo" %-c% -o 
%LTOBJ% %SOURCEFLAG%%SOURCE%; \
        then mv -f "%DEPBASE%.Tpo" "%DEPBASE%.Plo"; else rm -f "%DEPBASE%.Tpo"; 
exit 1; fi
 else !%FASTDEP%
 if %AMDEP%
@@ -125,8 +125,8 @@
        DEPDIR=$(DEPDIR) $(%FPFX%DEPMODE) $(depcomp) @AMDEPBACKSLASH@
 endif %AMDEP%
 ## We can always use `-o' with Libtool.
-?GENERIC?      %LTCOMPILE% %-c% -o %LTOBJ% %SOURCE%
+?GENERIC?      %LTCOMPILE% %-c% -o %LTOBJ% %SOURCEFLAG%%SOURCE%
 ## For non-suffix rules, we must emulate a VPATH search on %SOURCE%.
-?!GENERIC?     %LTCOMPILE% %-c% -o %LTOBJ% `test -f '%SOURCE%' || echo 
'$(srcdir)/'`%SOURCE%
+?!GENERIC?     %LTCOMPILE% %-c% -o %LTOBJ% %SOURCEFLAG%`test -f '%SOURCE%' || 
echo '$(srcdir)/'`%SOURCE%
 endif !%FASTDEP%
 endif %?LIBTOOL%