This PR fixes Windows clang-cl build error: "constexpr variable 'strnlen' must be initialized by a constant expression. "
Unfortunately the strnlen() seems incompatible with constexpr in clang-cl compile.
But in the case of this case, MSVC/clang-cl can use the strnlen_s() function anyway.
This changes should only affects the Windows MSVC/clang-cl build.
This PR fixes Windows clang-cl build error: "constexpr variable 'strnlen' must be initialized by a constant expression. "
Unfortunately the strnlen() seems incompatible with constexpr in clang-cl compile. But in the case of this case, MSVC/clang-cl can use the strnlen_s() function anyway.
This changes should only affects the Windows MSVC/clang-cl build.
descrived in #399