https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77582
--- Comment #3 from Cong Wang <xiyou.wangcong at gmail dot com> --- Hi, Andrew I just posted it: https://gcc.gnu.org/ml/libstdc++/2016-09/msg00051.html Please review. I caught this when using Google protobuf on Fedora 21, _M_mutate() is shown in perf top profile, inlined into clear(). AFAIK, only !_GLIBCXX_USE_CXX11_ABI impl uses _M_mutate(). Thanks.