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ACX_F77_CMAIN_FFLAGS([ACTION-IF-SUCCEED], [ACTION-IF-FAIL])
This macro figures out if extra Fortran compiler flags are required in order to use the Fortran linker to link programs where the main() function is defined via C (or other language). On some systems, notably the Alpha with Compaq compilers, the Fortran libraries have their own main() function which must be disabled.
Runs ACTION-IF-SUCCEED if successful, and ACTION-IF-FAIL if not. Defines the output variable F77_CMAIN_FFLAGS to any discovered flags. (If ACTION-IF-FAIL is not specified, defaults to halting with an error.)
This macro is especially useful in conjunction with automake, since by default automake uses $F77 to link programs mixing C and Fortran, leading to a link error on some systems. In this case, you should set the FFLAGS for that program to include F77_CMAIN_FFLAGS.
Steven G. Johnson <stevenj@alum.mit.edu>
2003-03-27
AC_DEFUN([ACX_F77_CMAIN_FFLAGS], [AC_CACHE_CHECK([for f77 flags to use C main function], acx_cv_f77_cmain_fflags, [acx_cv_f77_cmain_fflags="unknown" AC_LANG_PUSH(C) AC_COMPILE_IFELSE([[int main(void) { return 0; }]], [mv conftest.$ac_objext conftest_cmain.$ac_objext], [acx_cv_f77_cmain_fflags=error]) AC_LANG_POP(C) if test "x$acx_cv_f77_cmain_fflags" != xerror; then AC_LANG_PUSH(Fortran 77) acx_save_LIBS=$LIBS LIBS="conftest_cmain.$ac_objext $LIBS" acx_save_FFLAGS=$FFLAGS for acx_flag in none -nofor_main; do case $acx_flag in none) FFLAGS=$acx_save_FFLAGS ;; *) FFLAGS="$acx_save_FFLAGS $acx_flag" ;; esac AC_LINK_IFELSE([ subroutine foobar() return end ], [acx_cv_f77_cmain_fflags=$acx_flag; break]); done FFLAGS=$acx_save_FFLAGS LIBS=$acx_save_LIBS AC_LANG_POP(Fortran 77) fi]) case $acx_cv_f77_cmain_fflags in error|unknown) F77_CMAIN_FFLAGS="" ifelse([$2],,[AC_MSG_ERROR([cannot link C main with Fortran])],[$2]) ;; *) if test "x$acx_cv_f77_cmain_fflags" = xnone; then F77_CMAIN_FFLAGS="" else F77_CMAIN_FFLAGS="$acx_cv_f77_cmain_fflags" fi $1 ;; esac AC_SUBST(F77_CMAIN_FFLAGS) ])