Index: libstdc++-v3/include/ext/vstring.h
===================================================================
--- libstdc++-v3/include/ext/vstring.h	(revision 171950)
+++ libstdc++-v3/include/ext/vstring.h	(working copy)
@@ -37,6 +37,21 @@
 #include <ext/rc_string_base.h>
 #include <ext/sso_string_base.h>
 
+#if __google_stl_debug_string && !defined(_GLIBCXX_DEBUG)
+# undef _GLIBCXX_DEBUG_ASSERT
+# undef _GLIBCXX_DEBUG_PEDASSERT
+// Perform additional checks (but only in this file).
+# define _GLIBCXX_DEBUG_ASSERT(_Condition)                             \
+  if (! (_Condition)) {                                                \
+    char buf[512];                                                     \
+    __builtin_snprintf(buf, sizeof(buf),                               \
+                      "%s:%d: %s: Assertion '%s' failed.\n",           \
+                      __FILE__, __LINE__, __func__, # _Condition);     \
+    std::__throw_runtime_error(buf);                                   \
+  }
+# define _GLIBCXX_DEBUG_PEDASSERT(_Condition) _GLIBCXX_DEBUG_ASSERT(_Condition)
+#endif
+
 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
@@ -2793,4 +2808,12 @@
 
 #include "vstring.tcc" 
 
+#if __google_stl_debug_string && !defined(_GLIBCXX_DEBUG)
+// Undo our defines, so they don't affect anything else.
+# undef _GLIBCXX_DEBUG_ASSERT
+# undef _GLIBCXX_DEBUG_PEDASSERT
+# define _GLIBCXX_DEBUG_ASSERT(_Condition)
+# define _GLIBCXX_DEBUG_PEDASSERT(_Condition)
+#endif
+
 #endif /* _VSTRING_H */
Index: libstdc++-v3/include/ext/sso_string_base.h
===================================================================
--- libstdc++-v3/include/ext/sso_string_base.h	(revision 171950)
+++ libstdc++-v3/include/ext/sso_string_base.h	(working copy)
@@ -86,6 +86,13 @@
       {
 	if (!_M_is_local())
 	  _M_destroy(_M_allocated_capacity);
+#if __google_stl_debug_string_dangling
+	else {
+          // Wipe local storage for destructed string with 0xCD.
+          // This mimics what DebugAllocation does to free()d memory.
+          __builtin_memset(_M_local_data, 0xcd, sizeof(_M_local_data));
+        }
+#endif
       }
 
       void
Index: libstdc++-v3/include/bits/stl_vector.h
===================================================================
--- libstdc++-v3/include/bits/stl_vector.h	(revision 171950)
+++ libstdc++-v3/include/bits/stl_vector.h	(working copy)
@@ -690,10 +690,18 @@
        *  Note that data access with this operator is unchecked and
        *  out_of_range lookups are not defined. (For checked lookups
        *  see at().)
+       *
+       *  Local modification: range checks are performed if
+       *  __google_stl_debug_vector is defined to non-zero.
        */
       reference
       operator[](size_type __n)
-      { return *(this->_M_impl._M_start + __n); }
+      {
+#if __google_stl_debug_vector
+	_M_range_check(__n);
+#endif
+	return *(this->_M_impl._M_start + __n);
+      }
 
       /**
        *  @brief  Subscript access to the data contained in the %vector.
@@ -705,10 +713,18 @@
        *  Note that data access with this operator is unchecked and
        *  out_of_range lookups are not defined. (For checked lookups
        *  see at().)
+       *
+       *  Local modification: range checks are performed if
+       *  __google_stl_debug_vector is defined to non-zero.
        */
       const_reference
       operator[](size_type __n) const
-      { return *(this->_M_impl._M_start + __n); }
+      {
+#if __google_stl_debug_vector
+	_M_range_check(__n);
+#endif
+	return *(this->_M_impl._M_start + __n);
+      }
 
     protected:
       /// Safety check used only from at().
Index: libstdc++-v3/testsuite/23_containers/vector/requirements/dr438/assign_neg.cc
===================================================================
--- libstdc++-v3/testsuite/23_containers/vector/requirements/dr438/assign_neg.cc	(revision 171950)
+++ libstdc++-v3/testsuite/23_containers/vector/requirements/dr438/assign_neg.cc	(working copy)
@@ -18,7 +18,7 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do compile }
-// { dg-error "no matching" "" { target *-*-* } 1150 }
+// { dg-error "no matching" "" { target *-*-* } 1166 }
 // { dg-excess-errors "" }
 
 #include <vector>
Index: libstdc++-v3/testsuite/23_containers/vector/requirements/dr438/insert_neg.cc
===================================================================
--- libstdc++-v3/testsuite/23_containers/vector/requirements/dr438/insert_neg.cc	(revision 171950)
+++ libstdc++-v3/testsuite/23_containers/vector/requirements/dr438/insert_neg.cc	(working copy)
@@ -18,7 +18,7 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do compile }
-// { dg-error "no matching" "" { target *-*-* } 1191 }
+// { dg-error "no matching" "" { target *-*-* } 1207 }
 // { dg-excess-errors "" }
 
 #include <vector>
Index: libstdc++-v3/testsuite/23_containers/vector/requirements/dr438/constructor_1_neg.cc
===================================================================
--- libstdc++-v3/testsuite/23_containers/vector/requirements/dr438/constructor_1_neg.cc	(revision 171950)
+++ libstdc++-v3/testsuite/23_containers/vector/requirements/dr438/constructor_1_neg.cc	(working copy)
@@ -18,7 +18,7 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do compile }
-// { dg-error "no matching" "" { target *-*-* } 1080 }
+// { dg-error "no matching" "" { target *-*-* } 1096 }
 // { dg-excess-errors "" }
 
 #include <vector>
Index: libstdc++-v3/testsuite/23_containers/vector/requirements/dr438/constructor_2_neg.cc
===================================================================
--- libstdc++-v3/testsuite/23_containers/vector/requirements/dr438/constructor_2_neg.cc	(revision 171950)
+++ libstdc++-v3/testsuite/23_containers/vector/requirements/dr438/constructor_2_neg.cc	(working copy)
@@ -18,7 +18,7 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do compile }
-// { dg-error "no matching" "" { target *-*-* } 1080 }
+// { dg-error "no matching" "" { target *-*-* } 1096 }
 // { dg-excess-errors "" }
 
 #include <vector>
