Maintain ABI backwards compatibility with gcc 4.7.

2014-07-09 Martin von Gagern

References:
 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61758
 * https://bugs.gentoo.org/show_bug.cgi?id=513386

Index: gcc-4.8.3/libstdc++-v3/src/c++11/chrono.cc
===================================================================
--- gcc-4.8.3.orig/libstdc++-v3/src/c++11/chrono.cc
+++ gcc-4.8.3/libstdc++-v3/src/c++11/chrono.cc
@@ -102,4 +102,13 @@ namespace std _GLIBCXX_VISIBILITY(defaul
   } // namespace chrono
 } // namespace std
 
+#if defined(_GLIBCXX_SYMVER_GNU) && defined(_GLIBCXX_SHARED) \
+ && defined(_GLIBCXX_HAVE_AS_SYMVER_DIRECTIVE)               \
+ && defined(_GLIBCXX_HAVE_SYMVER_SYMBOL_RENAMING_RUNTIME_SUPPORT)
+// alias for backwards abi compatibility, see GCC #61758 / Gentoo #513386
+asm (".symver "
+     "_ZNSt6chrono3_V212steady_clock3nowEv,"
+     "_ZNSt6chrono12steady_clock3nowEv@GLIBCXX_3.4.17");
+#endif
+
 #endif // _GLIBCXX_USE_C99_STDINT_TR1