Is codecvt not a std header?
The reason why GCC rejects this code is simple: libstdc++ doesn’t support <codecvt> yet. The C++11 support status page confirms this: 22.5 Standard code conversion facets N
codecvt
Deprecated header replacement
Don’t worry about that. According to the same information source: this library component should be retired to Annex D, along side , until a suitable replacement is standardized. So, you can still use it until a new standardized, more-secure version is done.