[Bug fortran/41298] wrong-code: Default initializer C_NULL_PTR ignored

["burnus at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #1 from burnus at gcc dot gnu dot org  2009-09-08 16:06 -------
Regarding the initialization: Initializing proc pointers and pointers works.

The first time one hits gfc_conv_structure, one has:
  expr->expr_type == EXPR_STRUCTURE
for the type
  expr->ts->u.derived->name == "fgsl_file".
If one drills deeper, one finds another
  expr->value.constructor->expr->expr_type == EXPR_STRUCTURE
this time as expected of the type
  expr->value.constructor->expr->ts->u.derived->name == "c_ptr"
So far so good. Now one just needs to have an EXPR_NULL or EXPR_VARIABLE or
something like that -- but:
  expr->value.constructor->expr->value.constructor->expr == NULL

However, in gfc_conv_structure:
  for (c = expr->value.constructor; c; c = c->next, cm = cm->next)
    {
      if (!c->expr || cm->attr.allocatable)
        continue;

It shouldn't be NULL; if it weren't one could enter gfc_conv_initializer and
could enter there:
  if (expr != NULL && expr->ts.type == BT_DERIVED
      && expr->ts.is_iso_c && expr->ts.u.derived)
    expr = gfc_int_expr (0);

Thus the question is: Why is the last expr == NULL and not EXPR_VARIABLE of
flavour FL_PARAMETER?

 * * *

Another question: Why is there an
  if (file != 0)
I think it should always be true, unless sym is explicitly marked as optional.
Thus the following gives a nanosecond speed up and saves five bytes or so in
the file size (untested):

Index: trans-decl.c
===================================================================
--- trans-decl.c        (revision 151512)
+++ trans-decl.c        (working copy)
@@ -2992,7 +2992,7 @@ gfc_init_default_dt (gfc_symbol * sym, t
   gfc_set_sym_referenced (sym);
   e = gfc_lval_expr_from_sym (sym);
   tmp = gfc_trans_assignment (e, sym->value, false);
-  if (sym->attr.dummy)
+  if (sym->attr.dummy && sym->attr.optional)
     {
       present = gfc_conv_expr_present (sym);
       tmp = build3 (COND_EXPR, TREE_TYPE (tmp), present,
@@ -3030,9 +3030,12 @@ init_intent_out_dt (gfc_symbol * proc_sy
                                             f->sym->backend_decl,
                                             f->sym->as ? f->sym->as->rank :
0);

-           present = gfc_conv_expr_present (f->sym);
-           tmp = build3 (COND_EXPR, TREE_TYPE (tmp), present,
-                         tmp, build_empty_stmt (input_location));
+           if (f->sym->attr.optional)
+             {
+               present = gfc_conv_expr_present (f->sym);
+               tmp = build3 (COND_EXPR, TREE_TYPE (tmp), present,
+                             tmp, build_empty_stmt (input_location));
+             }

            gfc_add_expr_to_block (&fnblock, tmp);
          }


-- 

burnus at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|wrong-code: Default         |wrong-code: Default
                   |initializer ignored         |initializer C_NULL_PTR
                   |                            |ignored


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41298