[Bug fortran/48279] [4.6/4.7 Regression] segfault in gfc_check_vardef_context

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48279

--- Comment #6 from Tobias Burnus <burnus at gcc dot gnu.org> 2011-03-28 13:21:30 UTC ---
==1823== Invalid read of size 1
==1823==    at 0x4C32E7: gfc_check_vardef_context (expr.c:4377)
==1823==    by 0x4CBC25: compare_actual_formal (interface.c:2291)
==1823==    by 0x4CD48B: gfc_arglist_matches_symbol (interface.c:2813)
==1823==    by 0x4CD6F4: gfc_search_interface (interface.c:2842)
==1823==    by 0x50D2A2: resolve_call (resolve.c:3204)

The issue - or at least cause - for the segfault is the following code in
gfc_check_vardef_context:

  if (!pointer && e->expr_type == EXPR_FUNCTION
      && e->symtree->n.sym->result->attr.pointer)

The problem is that e->symtree->n.sym->result == NULL. The symbol itself is
"get_d_string". If one uses gdb's "set e->symtree->n.sym->result =
e->symtree->n.sym" and continues, one gets the expected error:

  Error: There is no specific subroutine for the generic 'set' at (1)

One problem seems to be that "get_d_string" is a generic interface - and not a
specific one:

(gdb) p e->symtree->n.sym->attr.generic
$1 = 1

The specific interface has properly the result variables set:
(gdb) p e->symtree->n.sym->generic->sym->name
$3 = 0x2aaaae876280 "get_d_string_p"
(gdb) p e->symtree->n.sym->generic->sym->result
$4 = (struct gfc_symbol *) 0x1281280

Calling gfc_check_vardef_context for an generic interface seems to be
questionable.