[Bug fortran/51308] PARAMETER attribute conflicts with SAVE attribute

[sgk at troutmask dot apl.washington.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51308

--- Comment #2 from Steve Kargl <sgk at troutmask dot apl.washington.edu> 2011-11-27 21:56:30 UTC ---
On Sat, Nov 26, 2011 at 07:21:29PM +0000, kargl at gcc dot gnu.org wrote:
> The problem comes about because of gen_special_c_interop_ptr() in
> symbol.c has the following lines:
> 
>   /* Set up the symbol's important fields.  Save attr required so we can
>      initialize the ptr to NULL.  */
>   tmp_sym->attr.save = SAVE_EXPLICIT;
> 
> I think that we should be setting 
> 
> tmp_sym->attr.flavor = FL_PARAMETER;
> 
> or something equivalent rather than the save attribute.
> 

attr.flavor was actually set further down in the file.  The
following patch appears to work, but it ceratinly feels to
be a kludge.

Index: symbol.c
===================================================================
--- symbol.c    (revision 181731)
+++ symbol.c    (working copy)
@@ -742,7 +742,8 @@ check_conflict (symbol_attribute *attr, 
       conf2 (asynchronous);
       conf2 (threadprivate);
       conf2 (value);
-      conf2 (is_bind_c);
+      if (!(name && (strcmp(name, "c_null_ptr") == 0 || strcmp(name,
"c_null_funptr") == 0)))
+    conf2 (is_bind_c);
       conf2 (codimension);
       conf2 (result);
       break;
@@ -3765,7 +3766,11 @@ gen_special_c_interop_ptr (int ptr_id, c

   /* Set up the symbol's important fields.  Save attr required so we can
      initialize the ptr to NULL.  */
-  tmp_sym->attr.save = SAVE_EXPLICIT;
+  tmp_sym->attr.save = SAVE_IMPLICIT;
+  /* Must declare c_null_ptr and c_null_funptr as having the
+     PARAMETER attribute so they can be used in init expressions.  */
+  tmp_sym->attr.flavor = FL_PARAMETER;
+
   tmp_sym->ts.is_c_interop = 1;
   tmp_sym->attr.is_c_interop = 1;
   tmp_sym->ts.is_iso_c = 1;
@@ -3777,6 +3782,7 @@ gen_special_c_interop_ptr (int ptr_id, c
     tmp_sym->ts.u.derived = get_iso_c_binding_dt (ISOCBINDING_PTR);
   else
     tmp_sym->ts.u.derived = get_iso_c_binding_dt (ISOCBINDING_FUNPTR);
+
   if (tmp_sym->ts.u.derived == NULL)
     {
       /* This can occur if the user forgot to declare c_ptr or
@@ -3817,9 +3823,6 @@ gen_special_c_interop_ptr (int ptr_id, c
   c->expr = gfc_get_expr ();
   c->expr->expr_type = EXPR_NULL;
   c->expr->ts.is_iso_c = 1;
-  /* Must declare c_null_ptr and c_null_funptr as having the
-     PARAMETER attribute so they can be used in init expressions.  */
-  tmp_sym->attr.flavor = FL_PARAMETER;

   return SUCCESS;
 }