[Bug fortran/53597] New: [4.6/4.7/4.8 Regression] F95/F2003 constraint no longer triggers: un-SAVED default-initialized module variable

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53597

             Bug #: 53597
           Summary: [4.6/4.7/4.8 Regression] F95/F2003 constraint no
                    longer triggers: un-SAVED default-initialized module
                    variable
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Keywords: accepts-invalid, diagnostic
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: bur...@gcc.gnu.org


Based on the discussion at
https://groups.google.com/forum/?fromgroups#!topic/comp.lang.fortran/7QfDs7wtKVY

The following check in resolve.c does not trigger as attr.save ==
SAVE_IMPLICIT:

  if (!(sym->value || no_init_flag) && sym->ns->proc_name
      && sym->ns->proc_name->attr.flavor == FL_MODULE
      && !sym->ns->save_all && !sym->attr.save
      && !sym->attr.pointer && !sym->attr.allocatable
      && gfc_has_default_initializer (sym->ts.u.derived)
      && gfc_notify_std (GFC_STD_F2008, "Fortran 2008: Implied SAVE for "
                         "module variable '%s' at %L, needed due to "
                         "the default initialization", sym->name,

when compiling the following program with -std=f95 or -std=f2003:

MODULE somemodule
  IMPLICIT NONE
  TYPE sometype
    INTEGER :: i
    DOUBLE PRECISION, POINTER, DIMENSION(:,:) :: coef => NULL()
  END TYPE sometype
  TYPE(sometype) :: somevariable
END MODULE somemodule 



Possible patches:
a) Check for (sym->attr.save == SAVE_EXPLICIT || sym->value)
b) Use the patch below:

--- a/gcc/fortran/decl.c
+++ b/gcc/fortran/decl.c
@@ -3810,8 +3810,9 @@ match_attr_spec (void)
        }
     }

-  /* Module variables implicitly have the SAVE attribute.  */
-  if (gfc_current_state () == COMP_MODULE && !current_attr.save)
+  /* Since Fortran 2008 module variables implicitly have the SAVE attribute. 
*/
+  if (gfc_current_state () == COMP_MODULE && !current_attr.save
+      && (gfc_option.allow_std & GFC_STD_F2008) != 0)
     current_attr.save = SAVE_IMPLICIT;

   colon_seen = 1;