[Bug c/114931] [14/15 regression] ICE in get_alias_set when building tcl with -std=c23

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114931

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
I'll note that seeing code like the following which possibly mutates existing
hash entries looks quite broken.  But of course type_hash_canon is a fragile
bit of code (well, it shouldn't ...).  To me it looks like we should compute
and set the canonical type first and _then_ do the hash lookup (which should
include the canonical type).  And I'd make type_hash_canon take a tree * to
modify, making its return value a bool whether we found an existing type so
we can simply do if (type_hash_canon (hash, &t)) { ggc_free (orig_t); return t;
}

tree
build_function_type (tree value_type, tree arg_types,
                     bool no_named_args_stdarg_p)
{
  tree t;
  inchash::hash hstate;
  bool any_structural_p, any_noncanonical_p;
  tree canon_argtypes;

  gcc_assert (arg_types != error_mark_node);

  if (TREE_CODE (value_type) == FUNCTION_TYPE)
    {
      error ("function return type cannot be function");
      value_type = integer_type_node;
    }

  /* Make a node of the sort we want.  */
  t = make_node (FUNCTION_TYPE);
  TREE_TYPE (t) = value_type;
  TYPE_ARG_TYPES (t) = arg_types;
  if (no_named_args_stdarg_p)
    {
      gcc_assert (arg_types == NULL_TREE);
      TYPE_NO_NAMED_ARGS_STDARG_P (t) = 1;
    }

  /* If we already have such a type, use the old one.  */
  hashval_t hash = type_hash_canon_hash (t);
  t = type_hash_canon (hash, t);

  /* Set up the canonical type. */
  any_structural_p   = TYPE_STRUCTURAL_EQUALITY_P (value_type);
  any_noncanonical_p = TYPE_CANONICAL (value_type) != value_type;
  canon_argtypes = maybe_canonicalize_argtypes (arg_types,
                                                &any_structural_p,
                                                &any_noncanonical_p);
  if (any_structural_p)
    SET_TYPE_STRUCTURAL_EQUALITY (t);
  else if (any_noncanonical_p)
    TYPE_CANONICAL (t) = build_function_type (TYPE_CANONICAL (value_type),
                                              canon_argtypes);

  if (!COMPLETE_TYPE_P (t))
    layout_type (t);
  return t;
}