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& back() const; // constexpr since C++20 12 // charT& back(); // 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 22 test(S s) 23 { 24 const S& cs = s; 25 ASSERT_SAME_TYPE(decltype( s.back()), typename S::reference); 26 ASSERT_SAME_TYPE(decltype(cs.back()), typename S::const_reference); 27 LIBCPP_ASSERT_NOEXCEPT( s.back()); 28 LIBCPP_ASSERT_NOEXCEPT( cs.back()); 29 assert(&cs.back() == &cs[cs.size()-1]); 30 assert(&s.back() == &s[cs.size()-1]); 31 s.back() = typename S::value_type('z'); 32 assert(s.back() == typename S::value_type('z')); 33 } 34 35 template <class S> 36 TEST_CONSTEXPR_CXX20 void test_string() { 37 test(S("1")); 38 test(S("1234567890123456789012345678901234567890")); 39 } 40 41 TEST_CONSTEXPR_CXX20 bool test() { 42 test_string<std::string>(); 43 #if TEST_STD_VER >= 11 44 test_string<std::basic_string<char, std::char_traits<char>, min_allocator<char>>>(); 45 #endif 46 47 return true; 48 } 49 50 int main(int, char**) 51 { 52 test(); 53 #if TEST_STD_VER > 17 54 static_assert(test()); 55 #endif 56 57 return 0; 58 } 59