> This is a regression present on the mainline and 5 branch, for a double
> record extension involving a size clause on the root type and a
> discriminant with variant part on the first extension...
>
> Tested on x86_64-suse-linux, applied on the mainline and 5 branch.
>
>
> 2016-03-27 Eric Botcazou <ebotca...@adacore.com>
>
> * gcc-interface/decl.c (components_to_record): Add special case for
> single field with representation clause at offset 0.
The attached patch restricts the change to the problematic cases.
Tested on x86_64-suse-linux, applied on the mainline and 5 branch.
* gcc-interface/decl.c (components_to_record): Restrict the previous
change to fields with variable size.
--
Eric BotcazouIndex: gcc-interface/decl.c
===================================================================
--- gcc-interface/decl.c (revision 234695)
+++ gcc-interface/decl.c (working copy)
@@ -7606,13 +7606,15 @@ components_to_record (tree gnu_record_ty
if (p_gnu_rep_list && gnu_rep_list)
*p_gnu_rep_list = chainon (*p_gnu_rep_list, gnu_rep_list);
- /* If only one field has a rep clause and it starts at 0, put back the field
- at the head of the regular field list. This will avoid creating a useless
- REP part below and deal with the annoying case of an extension of a record
- with variable size and rep clause, for which the _Parent field is forced
- at offset 0 and has variable size, which we do not support below. */
+ /* Deal with the annoying case of an extension of a record with variable size
+ and partial rep clause, for which the _Parent field is forced at offset 0
+ and has variable size, which we do not support below. Note that we cannot
+ do it if the field has fixed size because we rely on the presence of the
+ REP part built below to trigger the reordering of the fields in a derived
+ record type when all the fields have a fixed position. */
else if (gnu_rep_list
&& !DECL_CHAIN (gnu_rep_list)
+ && TREE_CODE (DECL_SIZE (gnu_rep_list)) != INTEGER_CST
&& !variants_have_rep
&& first_free_pos
&& integer_zerop (first_free_pos)
