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