On Wed, May 30, 2007 at 12:49:53PM -0700, Brian T.N. Gunney wrote:
> I'm trying to ink a C++ program with fortran objects, but I get
> /nfs/apps/gcc/3.3.6/bin/../lib/gcc-lib/i686-pc-linux-gnu/3.3.6/../../../libfrtbegin.a(frtbegin.o)(.text+0x32): In function `main':
> ../../../../gcc-3.3.6/libf2c/libF77/main.c:28: undefined reference to `MAIN__'
You must mark an F77_MAIN function `extern "C"' when you define it in a C++
compilation unit.
> cprog.C
> ::::::::::::::
> #include "config.h"
> extern "C" {
> void F77_FUNC(fortsub,FORTSUB)( double &x );
> }
>
> #ifdef F77_DUMMY_MAIN
> # ifdef __cplusplus
> extern "C"
> # endif
> int F77_DUMMY_MAIN() { return 1; }
> #endif
Use exactly one of F77_DUMMY_MAIN or F77_MAIN in a given executable. F77_MAIN
is correct for this application; delete the above.
> int F77_MAIN( int argc, char **argv ) {
Write `extern "C" F77_MAIN( int argc, char **argv ) {' instead. The manual was
not explicit on thise point, so I installed the following patch to (hopefully)
clarify things.
2007-06-04 Noah Misch <noah@xxxxxxxxxxxxxx>
* doc/autoconf.texi (AC_F77_MAIN): Give a specific usage example that
works with both C and C++.
diff -Nurp -X dontdiff ac-clean/doc/autoconf.texi ac-fortcpp/doc/autoconf.texi
--- ac-clean/doc/autoconf.texi 2007-06-04 08:11:56.000000000 -0400
+++ ac-fortcpp/doc/autoconf.texi 2007-06-04 18:39:00.000000000 -0400
@@ -7094,8 +7094,16 @@ alternate main function name is found, @
simply defined to @code{main}.)
Thus, when calling Fortran routines from C that perform things like I/O,
-one should use this macro and name the "main" function
-@code{F77_MAIN} or @code{FC_MAIN} instead of @code{main}.
+one should use this macro and declare the "main" function like so:
+
+@example
+#ifdef __cplusplus
+ extern "C"
+#endif
+int F77_MAIN(int argc, char *argv[]);
+@end example
+
+(Again, replace @code{F77} with @code{FC} for Fortran instead of Fortran 77.)
@end defmac
@defmac AC_F77_WRAPPERS
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