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# ===========================================================================
# https://www.gnu.org/software/autoconf-archive/ax_f77_cmain_fflags.html
# ===========================================================================
#
# SYNOPSIS
#
# AX_F77_CMAIN_FFLAGS([ACTION-IF-SUCCEED], [ACTION-IF-FAIL])
#
# DESCRIPTION
#
# 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 $F77 to link programs mixing C and Fortran,
# leading to a link error on some systems. In this case, you should set
# the FFLAGS for that program to include F77_CMAIN_FFLAGS.
#
# LICENSE
#
# Copyright (c) 2008 Steven G. Johnson <stevenj@alum.mit.edu>
#
# This program is free software: you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation, either version 3 of the License, or (at your
# option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
# Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program. If not, see <https://www.gnu.org/licenses/>.
#
# As a special exception, the respective Autoconf Macro's copyright owner
# gives unlimited permission to copy, distribute and modify the configure
# scripts that are the output of Autoconf when processing the Macro. You
# need not follow the terms of the GNU General Public License when using
# or distributing such scripts, even though portions of the text of the
# Macro appear in them. The GNU General Public License (GPL) does govern
# all other use of the material that constitutes the Autoconf Macro.
#
# This special exception to the GPL applies to versions of the Autoconf
# Macro released by the Autoconf Archive. When you make and distribute a
# modified version of the Autoconf Macro, you may extend this special
# exception to the GPL to apply to your modified version as well.
#serial 6
AU_ALIAS([ACX_F77_CMAIN_FFLAGS], [AX_F77_CMAIN_FFLAGS])
AC_DEFUN([AX_F77_CMAIN_FFLAGS],
[AC_CACHE_CHECK([for f77 flags to use C main function], ax_cv_f77_cmain_fflags,
[ax_cv_f77_cmain_fflags="unknown"
AC_LANG_PUSH(C)
AC_COMPILE_IFELSE([[int main(void) { return 0; }]],
[mv conftest.$ac_objext conftest_cmain.$ac_objext],
[ax_cv_f77_cmain_fflags=error])
AC_LANG_POP(C)
if test "x$ax_cv_f77_cmain_fflags" != xerror; then
AC_LANG_PUSH(Fortran 77)
ax_save_LIBS=$LIBS
LIBS="conftest_cmain.$ac_objext $LIBS"
ax_save_FFLAGS=$FFLAGS
for ax_flag in none -nofor_main; do
case $ax_flag in
none) FFLAGS=$ax_save_FFLAGS ;;
*) FFLAGS="$ax_save_FFLAGS $ax_flag" ;;
esac
AC_LINK_IFELSE([
subroutine foobar()
return
end
], [ax_cv_f77_cmain_fflags=$ax_flag; break]);
done
FFLAGS=$ax_save_FFLAGS
LIBS=$ax_save_LIBS
AC_LANG_POP(Fortran 77)
fi])
case $ax_cv_f77_cmain_fflags in
error|unknown)
F77_CMAIN_FFLAGS=""
ifelse([$2],,[AC_MSG_ERROR([cannot link C main with Fortran])],[$2])
;;
*)
if test "x$ax_cv_f77_cmain_fflags" = xnone; then
F77_CMAIN_FFLAGS=""
else
F77_CMAIN_FFLAGS="$ax_cv_f77_cmain_fflags"
fi
$1
;;
esac
AC_SUBST(F77_CMAIN_FFLAGS)
])
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