[google gcc-4_7, integration] Scribble on destructed strings to catch invalid accesses.

[Paul Pluzhnikov]

This patch allows us to catch use of destructed strings.

Google ref: b/5430313

Ok for google/gcc-4_7 and google/integration?

--
Paul Pluzhnikov



Index: libstdc++-v3/include/ext/sso_string_base.h
===================================================================
--- libstdc++-v3/include/ext/sso_string_base.h  (revision 195417)
+++ libstdc++-v3/include/ext/sso_string_base.h  (working copy)
@@ -215,7 +215,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
                          const _Alloc& __a);
 
       ~__sso_string_base()
-      { _M_dispose(); }
+      {
+          _M_dispose();
+#ifdef __google_stl_debug_dangling_string
+          __builtin_memset(this, 0xcd, sizeof(*this));
+#endif
+      }
 
       _CharT_alloc_type&
       _M_get_allocator()