I wonder why libstdc++ development is so slow. Regex support has been missing since TR1.
libstdc++ is gcc's C++ stdlib; libc++ is clang's (although clang can used libstdc++). libc++ supports all of C++11, although there's still some bugs. libc++ is ABI incompatible with libstdc++, but it's explicitly designed to support using both libstdc++ and libc++ within the same program, so that's often not a program.
[1] http://gcc.gnu.org/wiki/Cxx11AbiCompatibility [2] http://stackoverflow.com/questions/12542971/using-libstdc-co...