[Bug fortran/87566] ICE with class(*) and select

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87566

--- Comment #3 from Tobias Burnus <burnus at gcc dot gnu.org> ---
@Paul: Some guidance is welcome!

(In reply to Tobias Burnus from comment #2)
> For some odd reasons the gimplfier does not like that f951 assigns a value
> to the digit 0 (last but one line of the "finally") ...

That's in trans-expr.c's gfc_conv_class_to_class():

      if (UNLIMITED_POLY (e))
        tmp = gfc_class_len_get (tmp);
      else if (e->ts.type == BT_CHARACTER)
          tmp = slen;
      else
        tmp = build_zero_cst (size_type_node);
      gfc_add_modify (&parmse->pre, ctree,
                      fold_convert (TREE_TYPE (ctree), tmp));

OK so far – now comes the finally part:

      if (!elemental && full_array && copyback)
          gfc_add_modify (&parmse->post, tmp,
                          fold_convert (TREE_TYPE (tmp), ctree));

And here we have assigned (if the "else" branch for tmp branch was taken) a
value to the build_zero_cst()!


Actually, I wonder whether the _len = 0 is needed. The current code is:

                class.0._len = 0;
                class.0._data =
__tmp_class_object_array_pointer->_data->p._data;
                class.0._vptr =
__tmp_class_object_array_pointer->_data->p._vptr;
                class.0._len = __tmp_class_object_array_pointer->_data->p._len;

i.e. we set _len twice. And also in finally, we have it also twice:

     0 = (unsigned long) class.0._len;
     __tmp_class_object_array_pointer->_data->p._len = class.0._len;

As band-aid the following works (on top of the patch from attachment 44831)

--- a/gcc/fortran/trans-expr.c
+++ b/gcc/fortran/trans-expr.c
@@ -1133,3 +1133,3 @@ gfc_conv_class_to_class (gfc_se *parmse, gfc_expr *e,
gfc_typespec class_ts,
        references, where the dynamic type cannot change.  */
-      if (!elemental && full_array && copyback)
+      if (!elemental && full_array && copyback && !INTEGER_CST_P (tmp))
          gfc_add_modify (&parmse->post, tmp,