75 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// UNSUPPORTED: c++03, c++11, c++14, c++179 10// <span>11 12// constexpr reference back() const noexcept;13// Expects: empty() is false.14// Effects: Equivalent to: return *(data() + (size() - 1));15//16 17#include <span>18#include <cassert>19#include <string>20 21#include "test_macros.h"22 23template <typename Span>24constexpr bool testConstexprSpan(Span sp) {25 LIBCPP_ASSERT(noexcept(sp.back()));26 return std::addressof(sp.back()) == sp.data() + sp.size() - 1;27}28 29template <typename Span>30void testRuntimeSpan(Span sp) {31 LIBCPP_ASSERT(noexcept(sp.back()));32 assert(std::addressof(sp.back()) == sp.data() + sp.size() - 1);33}34 35template <typename Span>36void testEmptySpan(Span sp) {37 if (!sp.empty()) [[maybe_unused]]38 auto res = sp.back();39}40 41struct A {};42constexpr int iArr1[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};43int iArr2[] = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19};44 45int main(int, char**) {46 static_assert(testConstexprSpan(std::span<const int>(iArr1, 1)), "");47 static_assert(testConstexprSpan(std::span<const int>(iArr1, 2)), "");48 static_assert(testConstexprSpan(std::span<const int>(iArr1, 3)), "");49 static_assert(testConstexprSpan(std::span<const int>(iArr1, 4)), "");50 51 static_assert(testConstexprSpan(std::span<const int, 1>(iArr1, 1)), "");52 static_assert(testConstexprSpan(std::span<const int, 2>(iArr1, 2)), "");53 static_assert(testConstexprSpan(std::span<const int, 3>(iArr1, 3)), "");54 static_assert(testConstexprSpan(std::span<const int, 4>(iArr1, 4)), "");55 56 testRuntimeSpan(std::span<int>(iArr2, 1));57 testRuntimeSpan(std::span<int>(iArr2, 2));58 testRuntimeSpan(std::span<int>(iArr2, 3));59 testRuntimeSpan(std::span<int>(iArr2, 4));60 61 testRuntimeSpan(std::span<int, 1>(iArr2, 1));62 testRuntimeSpan(std::span<int, 2>(iArr2, 2));63 testRuntimeSpan(std::span<int, 3>(iArr2, 3));64 testRuntimeSpan(std::span<int, 4>(iArr2, 4));65 66 std::string s;67 testRuntimeSpan(std::span<std::string>(&s, 1));68 testRuntimeSpan(std::span<std::string, 1>(&s, 1));69 70 std::span<int, 0> sp;71 testEmptySpan(sp);72 73 return 0;74}75