Errors with XCode C++ Standard Libraries

Question

Created Oct ’24

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So I was searching for answer to this question but nothing really came up. I am building a C++ static library for iOS and I use <vector> from standard library. However when I try to build I get error from within SDK iOS 17.5 char_trait.h as follows:

/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS17.5.sdk/usr/include/c++/v1/__string/char_traits.h:290:17 No member named '__constexpr_wmemcmp' in namespace 'std'; did you mean '__constexpr_memchr'?

and in constexpr_c_functions.h as follows:

/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS17.5.sdk/usr/include/c++/v1/__string/constexpr_c_functions.h:117:3 Static assertion failed due to requirement 'sizeof(const wchar_t) == 1': Calling memchr on non-trivially equality comparable types is unsafe.

I've set my c/c++ standards to C17 and C++17 in the build settings.

I have no idea what these weird errors are. Could really use some help.

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Answer 1

ssmith_c OP

Oct ’24

the first error suggests that your code does not #include <cwchar>

the second error indicates that your code is using memchr on a wchar_t, and it should be using wmemchar.

If you included the code that doesn't compile, rather than just the very last error message, someone might be able to help you further.

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Answer 2

avetis OP

Oct ’24

Here where therror is coming from in char_trait.h

  static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 int
  compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT {
    if (__n == 0)
      return 0;
    return std::__constexpr_wmemcmp(__s1, __s2, __n);
  }

Here are the sections throwing errors in constexpr_c_functions.h

template <class _Tp, class _Up>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp* __constexpr_memchr(_Tp* __str, _Up __value, size_t __count) {
  static_assert(sizeof(_Tp) == 1 && __libcpp_is_trivially_equality_comparable<_Tp, _Up>::value,
                "Calling memchr on non-trivially equality comparable types is unsafe.");

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