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dyncast.cc (__dynamic_cast): Handle mid-destruction dynamic_cast more gracefully.

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* libsupc++/dyncast.cc (__dynamic_cast): Handle mid-destruction
	dynamic_cast more gracefully.

From-SVN: r215350
This commit is contained in:
Jason Merrill 2014-09-18 08:34:43 -04:00 • committed by Jason Merrill
parent e770bfd997
commit 4666e1fb92
3 changed files with 45 additions and 0 deletions
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28
gcc/testsuite/g++.dg/rtti/dyncast7.C Normal file
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@ -0,0 +1,28 @@
// I think this dynamic_cast has undefined behavior when destroying E::o
// because we're the F period of destruction has started and ap doesn't
// point to the object currently being destroyed--but the reasonable
// options are success or failure, not SEGV.
// { dg-do run }
extern "C" void abort();
struct A { virtual ~A(); };
struct B { virtual ~B() { } };
struct C : B, A { };
struct E : virtual B { A o; };
struct F : virtual C, virtual E { };
A* ap;
C* cp;
A::~A() {
C* cp2 = dynamic_cast<C*>(ap);
if (cp2 != cp && cp2 != 0)
abort();
}
int main() {
F f;
ap = cp = &f;
}

5
libstdc++-v3/ChangeLog
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@ -1,3 +1,8 @@
2014-09-17 Jason Merrill <jason@redhat.com>
* libsupc++/dyncast.cc (__dynamic_cast): Handle mid-destruction
dynamic_cast more gracefully.
2014-09-15 Jakub Jelinek <jakub@redhat.com>
* testsuite/Makefile.am (check_p_numbers0, check_p_numbers1,

12
libstdc++-v3/libsupc++/dyncast.cc
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@ -55,6 +55,18 @@ __dynamic_cast (const void *src_ptr, // object started from
adjust_pointer <void> (src_ptr, prefix->whole_object);
const __class_type_info *whole_type = prefix->whole_type;
__class_type_info::__dyncast_result result;
// If the whole object vptr doesn't refer to the whole object type, we're
// in the middle of constructing a primary base, and src is a separate
// base. This has undefined behavior and we can't find anything outside
// of the base we're actually constructing, so fail now rather than
// segfault later trying to use a vbase offset that doesn't exist.
const void *whole_vtable = *static_cast <const void *const *> (whole_ptr);
const vtable_prefix *whole_prefix =
adjust_pointer <vtable_prefix> (whole_vtable,
-offsetof (vtable_prefix, origin));
if (whole_prefix->whole_type != whole_type)
return NULL;
whole_type->__do_dyncast (src2dst, __class_type_info::__contained_public,
dst_type, whole_ptr, src_type, src_ptr, result);