configury: revamp the fortran_check_use_only test

split the test into three source files in order to avoid a false positive when using old XCode version and gcc 5

config/ompi_fortran_check_use_only.m4

@@ -11,6 +11,8 @@ dnl                         University of Stuttgart.  All rights reserved.
 dnl Copyright (c) 2004-2005 The Regents of the University of California.
 dnl                         All rights reserved.
 dnl Copyright (c) 2010-2015 Cisco Systems, Inc.  All rights reserved.
+dnl Copyright (c) 2015      Research Organization for Information Science
+dnl                         and Technology (RIST). All rights reserved.
 dnl $COPYRIGHT$
 dnl
 dnl Additional copyrights may follow
@@ -32,30 +34,41 @@ dnl                                [action if not supported])
 dnl ----------------------------------------------------
 AC_DEFUN([OMPI_FORTRAN_CHECK_USE_ONLY],[
     AS_VAR_PUSHDEF([use_only_var], [ompi_cv_fortran_use_only])
+    OPAL_VAR_SCOPE_PUSH([FCFLAGS_save])
+    FCFLAGS="-I. $FCFLAGS"
 
     AC_CACHE_CHECK([if Fortran compiler supports USE...ONLY], use_only_var,
        [AC_LANG_PUSH([Fortran])
-        AC_COMPILE_IFELSE([AC_LANG_SOURCE([[MODULE aaa
-INTEGER :: aaa_unique
-COMMON/common_to_both/COMMON_NAME_TO_BOTH
+        cat > aaa.f90 << EOF
+MODULE aaa
+INTEGER :: CMON(1)
+COMMON/CMMON/CMON
+INTEGER :: global_aaa
 END MODULE aaa
-
+EOF
+        cat > bbb.f90 << EOF
 MODULE bbb
-INTEGER :: bbb_unique
-INTEGER, BIND(C, name="common_to_both_") :: COMMON_NAME_TO_BOTH
+integer, bind(C, name="cmmon_") :: CMON
+INTEGER :: global_bbb
 END MODULE bbb
-
-PROGRAM test_proc
-  USE :: aaa, ONLY: aaa_unique
-  USE :: bbb, ONLY: bbb_unique
+EOF
+        OPAL_LOG_COMMAND([$FC $FCFLAGS -c aaa.f90],
+                         [OPAL_LOG_COMMAND([$FC $FCFLAGS -c bbb.f90],
+                                           [AC_COMPILE_IFELSE([AC_LANG_SOURCE([[PROGRAM test
+USE aaa, ONLY : global_aaa
+USE bbb, ONLY : global_bbb
+implicit none
 END PROGRAM]])],
-             [AS_VAR_SET(use_only_var, yes)],
-             [AS_VAR_SET(use_only_var, no)])
-        touch conftest_foo.mod
-        rm -rf *.mod 2>/dev/null
+                                                              [AS_VAR_SET(use_only_var, yes)],
+                                                              [AS_VAR_SET(use_only_var, no)])],
+                                           [AS_VAR_SET(use_only_var, no)])],
+                         [AS_VAR_SET(use_only_var, no)])
+        rm -rf aaa.f90 aaa.o bbb.f90 bbb.o *.mod 2>/dev/null
         AC_LANG_POP([Fortran])
        ])
 
     AS_VAR_IF(use_only_var, [yes], [$1], [$2])
+    FCFLAGS=$FCFLAGS_save
+    OPAL_VAR_SCOPE_POP
     AS_VAR_POPDEF([use_only_var])dnl
 ])