The MS bitfields ABI and its stringent rules totally break packing in Ada, so
we cannot use the C layout in this case. The i386.c hunk fixes an oversight
which would result in gazillions of warnings for QUAL_UNION_TYPE.
Tested on i586-suse-linux and i686-pc-mingw32, applied on the mainline and the
4.7 branch (as obvious for the i386.c hunk).
2012-04-30 Eric Botcazou <ebotca...@adacore.com>
* config/i386/i386.c (ix86_handle_struct_attribute): Use the proper
predicate to discriminate types.
2012-04-30 Eric Botcazou <ebotca...@adacore.com>
* gcc-interface/utils.c (finish_record_type): Force the traditional GCC
layout for bitfields on the type if it is packed or has a representation
clause and an alternate layout is available.
--
Eric Botcazou
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c (revision 186907)
+++ config/i386/i386.c (working copy)
@@ -32465,8 +32465,7 @@ ix86_handle_struct_attribute (tree *node
else
type = node;
- if (!(type && (TREE_CODE (*type) == RECORD_TYPE
- || TREE_CODE (*type) == UNION_TYPE)))
+ if (!(type && RECORD_OR_UNION_TYPE_P (*type)))
{
warning (OPT_Wattributes, "%qE attribute ignored",
name);
Index: ada/gcc-interface/utils.c
===================================================================
--- ada/gcc-interface/utils.c (revision 186956)
+++ ada/gcc-interface/utils.c (working copy)
@@ -721,6 +721,19 @@ finish_record_type (tree record_type, tr
case where there is a rep clause but all fields have errors and
no longer have a position. */
TYPE_SIZE (record_type) = 0;
+
+ /* Ensure we use the traditional GCC layout for bitfields when we need
+ to pack the record type or have a representation clause. The other
+ possible layout (Microsoft C compiler), if available, would prevent
+ efficient packing in almost all cases. */
+#ifdef TARGET_MS_BITFIELD_LAYOUT
+ if (TARGET_MS_BITFIELD_LAYOUT && TYPE_PACKED (record_type))
+ decl_attributes (&record_type,
+ tree_cons (get_identifier ("gcc_struct"),
+ NULL_TREE, NULL_TREE),
+ ATTR_FLAG_TYPE_IN_PLACE);
+#endif
+
layout_type (record_type);
}
