The layout of variant record types doesn't always guarantee the proper
alignment of aliased components if the record types are also packed.
Fixed thusly, tested on x86_64-suse-linux, applied on the mainline.
2012-11-23 Eric Botcazou <ebotca...@adacore.com>
* gcc-interface/decl.c (components_need_strict_alignment): New.
(components_to_record): Do not pack the variants if one of the fields
needs strict alignment. Likewise for the variant part as a whole.
Specify the position of the variants even if the size isn't specified,
but do not specify the size of the variant part in this case.
2012-11-23 Eric Botcazou <ebotca...@adacore.com>
* gnat.dg/discr39.adb: New test.
--
Eric BotcazouIndex: gcc-interface/decl.c
===================================================================
--- gcc-interface/decl.c (revision 193720)
+++ gcc-interface/decl.c (working copy)
@@ -6650,6 +6650,30 @@ gnat_to_gnu_field (Entity_Id gnat_field,
return gnu_field;
}
+/* Return true if at least one member of COMPONENT_LIST needs strict
+ alignment. */
+
+static bool
+components_need_strict_alignment (Node_Id component_list)
+{
+ Node_Id component_decl;
+
+ for (component_decl = First_Non_Pragma (Component_Items (component_list));
+ Present (component_decl);
+ component_decl = Next_Non_Pragma (component_decl))
+ {
+ Entity_Id gnat_field = Defining_Entity (component_decl);
+
+ if (Is_Aliased (gnat_field))
+ return True;
+
+ if (Strict_Alignment (Etype (gnat_field)))
+ return True;
+ }
+
+ return False;
+}
+
/* Return true if TYPE is a type with variable size or a padding type with a
field of variable size or a record that has a field with such a type. */
@@ -6880,6 +6904,7 @@ components_to_record (tree gnu_record_ty
"XVN");
tree gnu_union_type, gnu_union_name;
tree this_first_free_pos, gnu_variant_list = NULL_TREE;
+ bool union_field_needs_strict_alignment = false;
if (TREE_CODE (gnu_name) == TYPE_DECL)
gnu_name = DECL_NAME (gnu_name);
@@ -6980,8 +7005,18 @@ components_to_record (tree gnu_record_ty
else
{
/* Deal with packedness like in gnat_to_gnu_field. */
- int field_packed
- = adjust_packed (gnu_variant_type, gnu_record_type, packed);
+ bool field_needs_strict_alignment
+ = components_need_strict_alignment (Component_List (variant));
+ int field_packed;
+
+ if (field_needs_strict_alignment)
+ {
+ field_packed = 0;
+ union_field_needs_strict_alignment = true;
+ }
+ else
+ field_packed
+ = adjust_packed (gnu_variant_type, gnu_record_type, packed);
/* Finalize the record type now. We used to throw away
empty records but we no longer do that because we need
@@ -6997,8 +7032,7 @@ components_to_record (tree gnu_record_ty
gnu_union_type,
all_rep_and_size
? TYPE_SIZE (gnu_variant_type) : 0,
- all_rep_and_size
- ? bitsize_zero_node : 0,
+ all_rep ? bitsize_zero_node : 0,
field_packed, 0);
DECL_INTERNAL_P (gnu_field) = 1;
@@ -7041,12 +7075,16 @@ components_to_record (tree gnu_record_ty
NULL, true, debug_info, gnat_component_list);
/* Deal with packedness like in gnat_to_gnu_field. */
- union_field_packed
- = adjust_packed (gnu_union_type, gnu_record_type, packed);
+ if (union_field_needs_strict_alignment)
+ union_field_packed = 0;
+ else
+ union_field_packed
+ = adjust_packed (gnu_union_type, gnu_record_type, packed);
gnu_variant_part
= create_field_decl (gnu_var_name, gnu_union_type, gnu_record_type,
- all_rep ? TYPE_SIZE (gnu_union_type) : 0,
+ all_rep_and_size
+ ? TYPE_SIZE (gnu_union_type) : 0,
all_rep || this_first_free_pos
? bitsize_zero_node : 0,
union_field_packed, 0);-- { dg-do run }
with System.Storage_Elements; use System.Storage_Elements;
procedure Discr39 is
type Rec (Has_Src : Boolean) is record
case Has_Src is
when True => Src : aliased Integer;
when False => null;
end case;
end record;
pragma Pack(Rec);
for Rec'Alignment use Integer'Alignment;
R : Rec (Has_Src => True);
begin
if R.Src'Address mod Integer'Alignment /= 0 then
raise Program_Error;
end if;
end;
