56 lines · 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-exception6//7//===----------------------------------------------------------------------===//8 9// <string>10 11// const charT& back() const; // constexpr since C++2012// charT& back(); // constexpr since C++2013 14#include <string>15#include <cassert>16 17#include "test_macros.h"18#include "min_allocator.h"19 20template <class S>21TEST_CONSTEXPR_CXX20 void test(S s) {22 const S& cs = s;23 ASSERT_SAME_TYPE(decltype(s.back()), typename S::reference);24 ASSERT_SAME_TYPE(decltype(cs.back()), typename S::const_reference);25 LIBCPP_ASSERT_NOEXCEPT(s.back());26 LIBCPP_ASSERT_NOEXCEPT(cs.back());27 assert(&cs.back() == &cs[cs.size() - 1]);28 assert(&s.back() == &s[cs.size() - 1]);29 s.back() = typename S::value_type('z');30 assert(s.back() == typename S::value_type('z'));31}32 33template <class S>34TEST_CONSTEXPR_CXX20 void test_string() {35 test(S("1"));36 test(S("1234567890123456789012345678901234567890"));37}38 39TEST_CONSTEXPR_CXX20 bool test() {40 test_string<std::string>();41#if TEST_STD_VER >= 1142 test_string<std::basic_string<char, std::char_traits<char>, min_allocator<char>>>();43#endif44 45 return true;46}47 48int main(int, char**) {49 test();50#if TEST_STD_VER > 1751 static_assert(test());52#endif53 54 return 0;55}56