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On Mon, 21 Oct 2002, Mark Mitchell wrote:> FWIW. This change introduces a regression for arm-unknown-netbsd1.5Y: > > FAIL: g++.abi/vbase8-9.C Execution test > > (the test dumps core with a segmentation fault when run.) How disturbing. During the construction of which object? (Try removing lines from the end of main until you no longer get an error.)I can reproduce the problem with int main() { C9 c9; } All the other constructors work (or they do at least not dump core... ;)
I believe this problem will be fixed by the attached patch, which corrects
yet another ABI bug involving empty classes. Tested on i686-pc-linux-gnu,
applied on the mainline.
--
Mark Mitchell mark@codesourcery.com
CodeSourcery, LLC http://www.codesourcery.com
2002-10-21 Mark Mitchell <mark@codesourcery.com>
* class.c (empty_base_at_nonzero_offset_p): New function.
(layout_nonempty_base_or_field): Do not check for conflicts when
laying out a virtual base using the GCC 3.2 ABI.
(build_base_field): Correct checking for presence of empty classes
at non-zero offsets when clearing CLASSTYPE_NEARLY_EMPTY_P.
2002-10-21 Mark Mitchell <mark@codesourcery.com>
* g++.dg/abi/vbase13.C: New test.
* g++.dg/abi/vbase14.C: Likewise.
Index: cp/class.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cp/class.c,v
retrieving revision 1.482
diff -c -p -r1.482 class.c
*** cp/class.c 21 Oct 2002 21:47:44 -0000 1.482
--- cp/class.c 22 Oct 2002 05:01:02 -0000
*************** static bool type_requires_array_cookie P
*** 209,214 ****
--- 209,215 ----
static bool contains_empty_class_p (tree);
static tree dfs_base_derived_from (tree, void *);
static bool base_derived_from (tree, tree);
+ static int empty_base_at_nonzero_offset_p (tree, tree, splay_tree);
/* Macros for dfs walking during vtt construction. See
dfs_ctor_vtable_bases_queue_p, dfs_build_secondary_vptr_vtt_inits
*************** layout_nonempty_base_or_field (record_la
*** 3674,3679 ****
--- 3675,3684 ----
empty class, have nonzero size, any overlap can happen only
with a direct or indirect base-class -- it can't happen with
a data member. */
+ /* G++ 3.2 did not check for overlaps when placing a non-empty
+ virtual base. */
+ if (!abi_version_at_least (2) && binfo && TREE_VIA_VIRTUAL (binfo))
+ break;
if (layout_conflict_p (type, offset, offsets, field_p))
{
/* Strip off the size allocated to this field. That puts us
*************** layout_nonempty_base_or_field (record_la
*** 3708,3713 ****
--- 3713,3728 ----
t);
}
+ /* Returns true if TYPE is empty and OFFSET is non-zero. */
+
+ static int
+ empty_base_at_nonzero_offset_p (tree type,
+ tree offset,
+ splay_tree offsets ATTRIBUTE_UNUSED)
+ {
+ return is_empty_class (type) && !integer_zerop (offset);
+ }
+
/* Layout the empty base BINFO. EOC indicates the byte currently just
past the end of the class, and should be correctly aligned for a
class of the type indicated by BINFO; OFFSETS gives the offsets of
*************** build_base_field (record_layout_info rli
*** 3816,3829 ****
else
{
tree eoc;
/* On some platforms (ARM), even empty classes will not be
byte-aligned. */
eoc = round_up (rli_size_unit_so_far (rli),
CLASSTYPE_ALIGN_UNIT (basetype));
! if (layout_empty_base (binfo, eoc, offsets, t))
! CLASSTYPE_NEARLY_EMPTY_P (t) = 0;
!
/* We do not create a FIELD_DECL for empty base classes because
it might overlap some other field. We want to be able to
create CONSTRUCTORs for the class by iterating over the
--- 3831,3867 ----
else
{
tree eoc;
+ bool atend;
/* On some platforms (ARM), even empty classes will not be
byte-aligned. */
eoc = round_up (rli_size_unit_so_far (rli),
CLASSTYPE_ALIGN_UNIT (basetype));
! atend = layout_empty_base (binfo, eoc, offsets, t);
! /* A nearly-empty class "has no proper base class that is empty,
! not morally virtual, and at an offset other than zero." */
! if (!TREE_VIA_VIRTUAL (binfo) && CLASSTYPE_NEARLY_EMPTY_P (t))
! {
! if (atend)
! CLASSTYPE_NEARLY_EMPTY_P (t) = 0;
! /* The check above (used in G++ 3.2) is insufficient because
! an empty class placed at offset zero might itself have an
! empty base at a non-zero offset. */
! else if (walk_subobject_offsets (basetype,
! empty_base_at_nonzero_offset_p,
! size_zero_node,
! /*offsets=*/NULL,
! /*max_offset=*/NULL_TREE,
! /*vbases_p=*/true))
! {
! if (abi_version_at_least (2))
! CLASSTYPE_NEARLY_EMPTY_P (t) = 0;
! else if (warn_abi)
! warning ("class `%T' will be considered nearly empty in a "
! "future version of GCC", t);
! }
! }
!
/* We do not create a FIELD_DECL for empty base classes because
it might overlap some other field. We want to be able to
create CONSTRUCTORs for the class by iterating over the
Index: testsuite/g++.dg/abi/vbase13.C
===================================================================
RCS file: testsuite/g++.dg/abi/vbase13.C
diff -N testsuite/g++.dg/abi/vbase13.C
*** /dev/null 1 Jan 1970 00:00:00 -0000
--- testsuite/g++.dg/abi/vbase13.C 22 Oct 2002 05:01:02 -0000
***************
*** 0 ****
--- 1,17 ----
+ // { dg-do run }
+ // { dg-options "-fabi-version=0 -w" }
+
+ struct E1 {};
+ struct E2 : public E1 {};
+ struct E : public E1, public E2 {};
+ struct N : public E { virtual void f () {} };
+
+ struct X : virtual public N {
+ };
+
+ int main () {
+ X x;
+ /* N should not be the primary base of X; it is not nearly empty. */
+ if ((void*)&x == (void*)(N*)&x)
+ return 1;
+ }
Index: testsuite/g++.dg/abi/vbase14.C
===================================================================
RCS file: testsuite/g++.dg/abi/vbase14.C
diff -N testsuite/g++.dg/abi/vbase14.C
*** /dev/null 1 Jan 1970 00:00:00 -0000
--- testsuite/g++.dg/abi/vbase14.C 22 Oct 2002 05:01:02 -0000
***************
*** 0 ****
--- 1,6 ----
+ // { dg-options "-Wabi" }
+
+ struct E1 {};
+ struct E2 : public E1 {}; // { dg-warning "layout" }
+ struct E : public E1, public E2 {}; // { dg-warning "layout|ambiguity" }
+ struct N : public E { virtual void f () {} }; // { dg-warning "nearly" }
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