Change cfortran default to yes.

configure

@@ -1644,7 +1644,7 @@ Optional Features:
                           create Fortran 90 interface using Fortran 2003
                           ISO_C_BINDING facility [default=no]
   --enable-cf-interface   create Fortran 77 interface using cfortran.h
-                          [default=no]
+                          [default=yes, if F77 or FC works]
   --enable-ruby-interface create Ruby language interface (EXPERIMENTAL)
                           [default=no]
   --enable-python-interface
@@ -5121,8 +5121,12 @@ fi
 # Check whether --enable-cf-interface was given.
 if test "${enable_cf_interface+set}" = set; then :
   enableval=$enable_cf_interface; test "x$enableval" != xno && enable_cf_interface=yes
+else
+  if test "x$FC" != xno || test "x$F77" != xno; then :
+  enable_cf_interface=yes
 else
   enable_cf_interface=no
+fi
 fi
  if test "x$enable_cf_interface" = xyes; then
@@ -5786,7 +5790,7 @@ fi
    if test "x$FC" = xno; then :
   { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
-as_fn_error $? "the Fortran 90 interface is requested but the Fortran compiler is disabled, missing or lacks the required features
+as_fn_error $? "the Fortran 2003 interface is requested but the Fortran compiler is disabled, missing or lacks the required features
 See \`config.log' for more details" "$LINENO" 5; }
 fi
 fi

configure.ac

@@ -40,9 +40,10 @@ AM_CONDITIONAL([ENABLE_ISOC_INTERFACE],
 
 AC_ARG_ENABLE([cf-interface],
   [AS_HELP_STRING([--enable-cf-interface],
-     [create Fortran 77 interface using cfortran.h @<:@default=no@:>@])],
+     [create Fortran 77 interface using cfortran.h @<:@default=yes, if F77 or FC works@:>@])],
   [test "x$enableval" != xno && enable_cf_interface=yes],
-  [enable_cf_interface=no])
+  [AS_IF([test "x$FC" != xno || test "x$F77" != xno],
+     [enable_cf_interface=yes],[enable_cf_interface=no])])
 AM_CONDITIONAL([ENABLE_CF_INTERFACE], [test "x$enable_cf_interface" = xyes])
 
 dnl We need FC for the Fortran 90 and for the Fortran 77 interfaces. In the
@@ -85,11 +86,11 @@ else
   FC=no
 fi
 AM_CONDITIONAL([FC_MOD_UPPERCASE], [test "x$FCMODCASE" = xuc])
-dnl Additional checks required for the Fortran 90 interface:
+dnl Additional checks required for the Fortran 2003 interface:
 AS_VAR_IF([enable_iso_c_interface], [yes],
   [AS_IF([test "x$FC" != xno], [ACX_FC_CHECK_STRPTR_CONVERT([], [FC=no])])
    AS_VAR_IF([FC], [no],
-     [AC_MSG_FAILURE([the Fortran 90 interface is requested but the Fortran ]dnl
+     [AC_MSG_FAILURE([the Fortran 2003 interface is requested but the Fortran ]dnl
 [compiler is disabled, missing or lacks the required features])])])
 AM_CONDITIONAL([BUILD_FC_PROGRAMS], [test "x$FC" != xno])