libcxx/test/std/strings/basic.string/string.access/front.pass.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // <string>
  10
  11 // const charT& front() const; // constexpr since C++20
  12 //       charT& front(); // constexpr since C++20
  13
  14 #include <string>
  15 #include <cassert>
  16
  17 #include "test_macros.h"
  18 #include "min_allocator.h"
  19
  20 template <class S>
  21 TEST_CONSTEXPR_CXX20 void test(S s) {
  22   const S& cs = s;
  23   ASSERT_SAME_TYPE(decltype(s.front()), typename S::reference);
  24   ASSERT_SAME_TYPE(decltype(cs.front()), typename S::const_reference);
  25   LIBCPP_ASSERT_NOEXCEPT(s.front());
  26   LIBCPP_ASSERT_NOEXCEPT(cs.front());
  27   assert(&cs.front() == &cs[0]);
  28   assert(&s.front() == &s[0]);
  29   s.front() = typename S::value_type('z');
  30   assert(s.front() == typename S::value_type('z'));
  31 }
  32
  33 template <class S>
  34 TEST_CONSTEXPR_CXX20 void test_string() {
  35   test(S("1"));
  36   test(S("1234567890123456789012345678901234567890"));
  37 }
  38
  39 TEST_CONSTEXPR_CXX20 bool test() {
  40   test_string<std::string>();
  41 #if TEST_STD_VER >= 11
  42   test_string<std::basic_string<char, std::char_traits<char>, min_allocator<char>>>();
  43 #endif
  44
  45   return true;
  46 }
  47
  48 int main(int, char**) {
  49   test();
  50 #if TEST_STD_VER > 17
  51   static_assert(test());
  52 #endif
  53
  54   return 0;
  55 }