New macro AC_FC_MODULE_FLAG: Fortran 90 module include path.

* lib/autoconf/fortran.m4 (AC_FC_MODULE_FLAG): New macro,
adjusted and rewritten from the AX_F90_MODULE_FLAG macro from
the Autoconf Macro Archive by Luc Maisonobe, Julian C. Cummings,
and Alexander Pletzer.
* doc/autoconf.texi (Fortran Compiler): Document it.
* tests/fortran.at (AC_FC_MODULE_FLAG): New test.
* tests/local.at (AT_CHECK_ENV): Do not complain about FC_MODINC
setting.
* NEWS, THANKS: Update.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>

1 files changed, 77 insertions, 0 deletions

diff --git a/lib/autoconf/fortran.m4 b/lib/autoconf/fortran.m4
index 864fcaa5..25b05403 100644
--- a/lib/autoconf/fortran.m4
+++ b/lib/autoconf/fortran.m4
@@ -1559,3 +1559,80 @@ if test "$FC_MODEXT" = unknown; then
 fi
 AC_SUBST([FC_MODEXT])dnl
 ])
+
+
+# AC_FC_MODULE_FLAG([ACTION-IF-SUCCESS], [ACTION-IF-FAILURE = FAILURE])
+# ---------------------------------------------------------------------
+# Find a flag to include Fortran 90 modules from another directory.
+# If successful, run ACTION-IF-SUCCESS (defaults to nothing), otherwise
+# run ACTION-IF-FAILURE (defaults to failing with an error message).
+# The module flag is cached in the ac_cv_fc_module_flag variable.
+# It may contain significant trailing whitespace.
+#
+# Known flags:
+# gfortran: -Idir, -I dir (-M dir, -Mdir (deprecated), -Jdir for writing)
+# g95: -I dir (-fmod=dir for writing)
+# SUN: -Mdir, -M dir (-moddir=dir for writing;
+#                     -Idir for includes is also searched)
+# HP: -Idir, -I dir (+moddir=dir for writing)
+# IBM: -Idir (-qmoddir=dir for writing)
+# Intel: -Idir -I dir (-mod dir for writing)
+# Absoft: -pdir
+# Lahey: -mod dir
+# Cray: -module dir, -p dir (-J dir for writing)
+#       -e m is needed to enable writing .mod files at all
+# Compaq: -Idir
+# NAGWare: -I dir
+# PathScale: -I dir  (but -module dir is looked at first)
+# Portland: -module dir (first -module also names dir for writing)
+# Fujitsu: -Am -Idir (-Mdir for writing is searched first, then '.', then -I)
+#                    (-Am indicates how module information is saved)
+AC_DEFUN([AC_FC_MODULE_FLAG],[
+AC_CACHE_CHECK([Fortran 90 module inclusion flag], [ac_cv_fc_module_flag],
+[AC_LANG_PUSH([Fortran])
+ac_cv_fc_module_flag=unknown
+mkdir conftest.dir
+cd conftest.dir
+AC_COMPILE_IFELSE([[
+      module conftest_module
+      contains
+      subroutine conftest_routine
+      write(*,'(a)') 'gotcha!'
+      end subroutine
+      end module]],
+  [cd ..
+   ac_fc_module_flag_FCFLAGS_save=$FCFLAGS
+   # Flag ordering is significant for gfortran and Sun.
+   for ac_flag in -M -I '-I ' '-M ' -p '-mod ' '-module ' '-Am -I'; do
+     # Add the flag twice to prevent matching an output flag.
+     FCFLAGS="$ac_fc_module_flag_FCFLAGS_save ${ac_flag}conftest.dir ${ac_flag}conftest.dir"
+     AC_COMPILE_IFELSE([[
+      program main
+      use conftest_module
+      call conftest_routine
+      end program]],
+       [ac_cv_fc_module_flag="$ac_flag"])
+     if test "$ac_cv_fc_module_flag" != unknown; then
+       break
+     fi
+   done
+   FCFLAGS=$ac_fc_module_flag_FCFLAGS_save
+])
+rm -rf conftest.dir
+AC_LANG_POP([Fortran])
+])
+if test "$ac_cv_fc_module_flag" != unknown; then
+  FC_MODINC=$ac_cv_fc_module_flag
+  $1
+else
+  FC_MODINC=
+  m4_default([$2],
+    [AC_MSG_ERROR([unable to find compiler flag for module search path])])
+fi
+AC_SUBST([FC_MODINC])
+# Ensure trailing whitespace is preserved in a Makefile.
+AC_SUBST([ac_empty], [""])
+AC_CONFIG_COMMANDS_PRE([case $FC_MODINC in #(
+  *\ ) FC_MODINC=$FC_MODINC'${ac_empty}' ;;
+esac])dnl
+])