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> test(S s)21TEST_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> test_string()34TEST_CONSTEXPR_CXX20 void test_string() { 35 test(S("1")); 36 test(S("1234567890123456789012345678901234567890")); 37 } 38 test()39TEST_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 main(int,char **)48int main(int, char**) { 49 test(); 50 #if TEST_STD_VER > 17 51 static_assert(test()); 52 #endif 53 54 return 0; 55 } 56