# ============================================================================
#  https://www.gnu.org/software/autoconf-archive/ax_f90_module_extension.html
# ============================================================================
#
# SYNOPSIS
#
#   AX_F90_MODULE_EXTENSION
#
# DESCRIPTION
#
#   Find Fortran 90 modules file extension. The module extension is stored
#   in the cached variable ax_f90_modext, or "unknown" if the extension
#   cannot be found.
#
# LICENSE
#
#   Copyright (c) 2009 Luc Maisonobe <luc@spaceroots.org>
#   Copyright (c) 2009 Alexander Pletzer <pletzer@txcorp.com>
#
#   Copying and distribution of this file, with or without modification, are
#   permitted in any medium without royalty provided the copyright notice
#   and this notice are preserved. This file is offered as-is, without any
#   warranty.

#serial 12

AC_DEFUN([AX_F90_MODULE_EXTENSION],[
AC_CACHE_CHECK([fortran 90 modules extension],
ax_cv_f90_modext,
[AC_LANG_PUSH(Fortran)
i=0
while test \( -f tmpdir_$i \) -o \( -d tmpdir_$i \) ; do
  i=`expr $i + 1`
done
mkdir tmpdir_$i
cd tmpdir_$i
AC_COMPILE_IFELSE([
!234567
      module conftest_module
      contains
      subroutine conftest_routine
      write(*,'(a)') 'gotcha!'
      end subroutine conftest_routine
      end module conftest_module
  ],
  [ax_cv_f90_modext=`ls | sed -n 's,conftest_module\.,,p'`
   if test x$ax_cv_f90_modext = x ; then
dnl Some F90 compilers put module filename in uppercase letters
     ax_cv_f90_modext=`ls | sed -n 's,CONFTEST_MODULE\.,,p'`
     if test x$ax_cv_f90_modext = x ; then
       ax_cv_f90_modext=""
     fi
   fi
  ],
  [ax_cv_f90_modext=""])
cd ..
rm -fr tmpdir_$i
AC_LANG_POP(Fortran)
])])