when compiling libstdc++ with --enable-symvers=gnu-versioned-namespace std::regex complaining about private data members trying to be accessed outside the class:

22:55:46 /home/y/include/c++/4.9.2/bits/regex.h:796:30: error: ‘std::__7::basic_regex<char>::_AutomatonPtr std::__7::basic_regex<char>::_M_automaton’ is protected
22:55:46        _AutomatonPtr          _M_automaton;

I believe the bug is related with the __detail namespace[1] and friend classes[2] as it lacks the NAMESPACE_VERSION expansion. This happens in other lines and I believe it extends to hashmap as well. Turning data members public "fixes" the compilation problem.

[1]: https://github.com/gcc-mirror/gcc/blob/e0f174323b4297f46d9109201666da42aaa55fc8/libstdc%2B%2B-v3/include/bits/regex.h#L46

[2]: https://github.com/gcc-mirror/gcc/blob/e0f174323b4297f46d9109201666da42aaa55fc8/libstdc%2B%2B-v3/include/bits/regex.h#L772