Hello, It disturbed me for a few months now, but G++ doesn't provide type_traits when built without libstdc++ (which happens when you build for embedded or kernel development), but it should normally be included in any form of freestanding C++ implementation from C++11 onwards: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3690.pdf#page=434&zoom=auto,-48,688 http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4296.pdf#page=464&zoom=auto,-63,722 http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf#page=426&zoom=auto,-71,773 Why is it not available ? Should this be considered a bug ? Ludovic 'Archivist' Lagouardette