Add Constexpr Modifiers to Functions in <cstring> and <cwchar> Headers Full Text of Proposal P1944R0 References https://github.com/Neargye/WG21/tree/master/P1944 https://stdcpp.ru/proposals/b6000ec7-9db8-41b1-9a1e-1fe00a424bbd http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0202r0.html Tested GCC 10 Clang 10 Visual Studio 2019