My earlier patch for 58678 caused this problem: even if we aren't going
to refer to the dtor thunks from the vtable, we need to emit them in
case other translation units use them.
I'm adding xfails to two testcases: devirt-21.C and devirt-23.C. The
fails aren't a new bug; we are no longer seeing the devirtualization
because we remove the path to wrap() through a virtual call to
~MultiTermDocs that it occurred along. But it seems odd to me that it
isn't happening on path through a non-virtual call to ~MultiTermDocs, so
I'm filing a bug about that.
Tested x86_64-pc-linux-gnu, applying to trunk.
commit 38f48ae422064906ffc4acb3db6eaa962c702b39
Author: Jason Merrill <ja...@redhat.com>
Date: Wed Mar 26 00:02:35 2014 -0400
PR c++/60566
PR c++/58678
* class.c (build_vtbl_initializer): Handle abstract dtors here.
* search.c (get_pure_virtuals): Not here.
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index b46391b..d277e07 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -9017,6 +9017,16 @@ build_vtbl_initializer (tree binfo,
if (!TARGET_VTABLE_USES_DESCRIPTORS)
init = fold_convert (vfunc_ptr_type_node,
build_fold_addr_expr (fn));
+ /* Don't refer to a virtual destructor from a constructor
+ vtable or a vtable for an abstract class, since destroying
+ an object under construction is undefined behavior and we
+ don't want it to be considered a candidate for speculative
+ devirtualization. But do create the thunk for ABI
+ compliance. */
+ if (DECL_DESTRUCTOR_P (fn_original)
+ && (CLASSTYPE_PURE_VIRTUALS (DECL_CONTEXT (fn_original))
+ || orig_binfo != binfo))
+ init = size_zero_node;
}
}
diff --git a/gcc/cp/search.c b/gcc/cp/search.c
index d99e182..c3eed90 100644
--- a/gcc/cp/search.c
+++ b/gcc/cp/search.c
@@ -2115,22 +2115,6 @@ get_pure_virtuals (tree type)
which it is a primary base will contain vtable entries for the
pure virtuals in the base class. */
dfs_walk_once (TYPE_BINFO (type), NULL, dfs_get_pure_virtuals, type);
-
- /* Treat a virtual destructor in an abstract class as pure even if it
- isn't declared as pure; there is no way it would be called through the
- vtable except during construction, which causes undefined behavior. */
- if (CLASSTYPE_PURE_VIRTUALS (type)
- && TYPE_HAS_NONTRIVIAL_DESTRUCTOR (type))
- {
- tree dtor = CLASSTYPE_DESTRUCTORS (type);
- if (dtor && DECL_VIRTUAL_P (dtor) && !DECL_PURE_VIRTUAL_P (dtor))
- {
- tree clone;
- DECL_PURE_VIRTUAL_P (dtor) = true;
- FOR_EACH_CLONE (clone, dtor)
- DECL_PURE_VIRTUAL_P (clone) = true;
- }
- }
}
/* Debug info for C++ classes can get very large; try to avoid
diff --git a/gcc/ipa-devirt.c b/gcc/ipa-devirt.c
index 2f84f17..6fb1449 100644
--- a/gcc/ipa-devirt.c
+++ b/gcc/ipa-devirt.c
@@ -1261,7 +1261,7 @@ get_polymorphic_call_info (tree fndecl,
}
/* If the function is constructor or destructor, then
- the type is possibly in consturction, but we know
+ the type is possibly in construction, but we know
it is not derived type. */
if (DECL_CXX_CONSTRUCTOR_P (fndecl)
|| DECL_CXX_DESTRUCTOR_P (fndecl))
diff --git a/gcc/testsuite/g++.dg/abi/thunk6.C b/gcc/testsuite/g++.dg/abi/thunk6.C
new file mode 100644
index 0000000..e3d07f2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/abi/thunk6.C
@@ -0,0 +1,18 @@
+// PR c++/60566
+// We need to emit the construction vtable thunk for ~C even if we aren't
+// going to use it.
+
+struct A
+{
+ virtual void f() = 0;
+ virtual ~A() {}
+};
+
+struct B: virtual A { int i; };
+struct C: virtual A { int i; ~C(); };
+
+C::~C() {}
+
+int main() {}
+
+// { dg-final { scan-assembler "_ZTv0_n32_N1CD1Ev" } }
