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>
testConstexprSpan(Span sp)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>
testRuntimeSpan(Span sp)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>
testEmptySpan(Span sp)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
main(int,char **)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