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

	dynamic_cast more gracefully.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@215350 138bc75d-0d04-0410-961f-82ee72b054a4

2 files changed, 17 insertions, 0 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 2dc5a24d101..7682e279876 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -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,
diff --git a/libstdc++-v3/libsupc++/dyncast.cc b/libstdc++-v3/libsupc++/dyncast.cc
index 2bcb7ddbd9c..9f6adeffcf2 100644
--- a/libstdc++-v3/libsupc++/dyncast.cc
+++ b/libstdc++-v3/libsupc++/dyncast.cc
@@ -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);