https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91371
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- The problem is not with bind and bind_front, it's that std::is_function doesn't recognize such a function, and so std::decay doesn't know what to do with it: #include <functional> int bar(int) __attribute__((ms_abi)); //same with fastcall, thiscall static_assert(std::is_function<decltype(bar)>::value, ""); static_assert(std::is_pointer<std::decay_t<decltype(bar)>>::value, ""); Libstdc++ specializes std::is_function for every type of function, but doesn't handle alternative calling conventions. Libc++ uses a completely different approach which detects functions by testing whether it's a non-class type that supports implicit conversion from T& to T* (which is only true for functions).
