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 TEST_CONSTEXPR_CXX20 bool test() { 36 { 37 typedef std::string S; 38 test(S("1")); 39 test(S("1234567890123456789012345678901234567890")); 40 } 41 #if TEST_STD_VER >= 11 42 { 43 typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S; 44 test(S("1")); 45 test(S("1234567890123456789012345678901234567890")); 46 } 47 #endif 48 49 return true; 50 } 51 52 int main(int, char**) 53 { 54 test(); 55 #if TEST_STD_VER > 17 56 static_assert(test()); 57 #endif 58 59 return 0; 60 } 61