libcxx/test/support/test_format_string.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef SUPPORT_TEST_FORMAT_STRING_HPP
  11 #define SUPPORT_TEST_FORMAT_STRING_HPP
  12
  13 #include <concepts>
  14 #include <format>
  15 #include <type_traits>
  16
  17 #include "test_macros.h"
  18
  19 #if TEST_STD_VER < 20
  20 #  error "The format header requires at least C++20"
  21 #endif
  22
  23 // Wrapper for basic_format_string.
  24 //
  25 // This layer of indirection is used since it's not possible to use
  26 // std::basic_format_string<CharT, Args...> in the test function directly.
  27 //
  28 // In C++20 the basic-format-string was an exposition only type. In C++23 is
  29 // has been replaced with basic_format_string. Both libc++ and MSVC STL offer
  30 // it as an extension in C++20.
  31 #if TEST_STD_VER > 20 || defined(_LIBCPP_VERSION) || defined(_MSVC_STL_VERSION)
  32 #  ifndef TEST_HAS_NO_WIDE_CHARACTERS
  33 template <class CharT, class... Args>
  34 using test_format_string =
  35     std::conditional_t<std::same_as<CharT, char>, std::format_string<Args...>, std::wformat_string<Args...>>;
  36 #  else
  37 template <class CharT, class... Args>
  38 using test_format_string = std::format_string<Args...>;
  39 #  endif
  40
  41 #else // TEST_STD_VER > 20 || defined(_LIBCPP_VERSION) || defined( _MSVC_STL_VERSION)
  42
  43 #  error
  44 "Please create a vendor specific version of the test typedef and file a review at https://reviews.llvm.org/"
  45
  46 #endif // TEST_STD_VER > 20 || defined(_LIBCPP_VERSION) || defined( _MSVC_STL_VERSION)
  47
  48 #endif // SUPPORT_TEST_FORMAT_STRING_HPP