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 // UNSUPPORTED: c++03, c++11, c++14, c++17 9 10 // <span> 11 12 // constexpr reference front() const noexcept; 13 // Expects: empty() is false. 14 // Effects: Equivalent to: return *data(); 15 // 16 17 18 #include <span> 19 #include <cassert> 20 #include <string> 21 22 #include "test_macros.h" 23 24 25 template <typename Span> 26 constexpr bool testConstexprSpan(Span sp) 27 { 28 LIBCPP_ASSERT(noexcept(sp.front())); 29 return std::addressof(sp.front()) == sp.data(); 30 } 31 32 33 template <typename Span> 34 void testRuntimeSpan(Span sp) 35 { 36 LIBCPP_ASSERT(noexcept(sp.front())); 37 assert(std::addressof(sp.front()) == sp.data()); 38 } 39 40 template <typename Span> 41 void testEmptySpan(Span sp) 42 { 43 if (!sp.empty()) 44 [[maybe_unused]] auto res = sp.front(); 45 } 46 47 struct A{}; 48 constexpr int iArr1[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9}; 49 int iArr2[] = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19}; 50 51 int main(int, char**) 52 { 53 static_assert(testConstexprSpan(std::span<const int>(iArr1, 1)), ""); 54 static_assert(testConstexprSpan(std::span<const int>(iArr1, 2)), ""); 55 static_assert(testConstexprSpan(std::span<const int>(iArr1, 3)), ""); 56 static_assert(testConstexprSpan(std::span<const int>(iArr1, 4)), ""); 57 58 static_assert(testConstexprSpan(std::span<const int, 1>(iArr1, 1)), ""); 59 static_assert(testConstexprSpan(std::span<const int, 2>(iArr1, 2)), ""); 60 static_assert(testConstexprSpan(std::span<const int, 3>(iArr1, 3)), ""); 61 static_assert(testConstexprSpan(std::span<const int, 4>(iArr1, 4)), ""); 62 63 64 testRuntimeSpan(std::span<int>(iArr2, 1)); 65 testRuntimeSpan(std::span<int>(iArr2, 2)); 66 testRuntimeSpan(std::span<int>(iArr2, 3)); 67 testRuntimeSpan(std::span<int>(iArr2, 4)); 68 69 70 testRuntimeSpan(std::span<int, 1>(iArr2, 1)); 71 testRuntimeSpan(std::span<int, 2>(iArr2, 2)); 72 testRuntimeSpan(std::span<int, 3>(iArr2, 3)); 73 testRuntimeSpan(std::span<int, 4>(iArr2, 4)); 74 75 std::string s; 76 testRuntimeSpan(std::span<std::string> (&s, 1)); 77 testRuntimeSpan(std::span<std::string, 1>(&s, 1)); 78 79 std::span<int, 0> sp; 80 testEmptySpan(sp); 81 82 return 0; 83 } 84