1 // -*- C++ -*-
2 //===------------------------------ span ---------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===---------------------------------------------------------------------===//
9 // UNSUPPORTED: c++03, c++11, c++14, c++17
10
11 // <span>
12
13 // constexpr reference front() const noexcept;
14 // Expects: empty() is false.
15 // Effects: Equivalent to: return *data();
16 //
17
18
19 #include <span>
20 #include <cassert>
21 #include <string>
22
23 #include "test_macros.h"
24
25
26 template <typename Span>
testConstexprSpan(Span sp)27 constexpr bool testConstexprSpan(Span sp)
28 {
29 LIBCPP_ASSERT(noexcept(sp.front()));
30 return std::addressof(sp.front()) == sp.data();
31 }
32
33
34 template <typename Span>
testRuntimeSpan(Span sp)35 void testRuntimeSpan(Span sp)
36 {
37 LIBCPP_ASSERT(noexcept(sp.front()));
38 assert(std::addressof(sp.front()) == sp.data());
39 }
40
41 template <typename Span>
testEmptySpan(Span sp)42 void testEmptySpan(Span sp)
43 {
44 if (!sp.empty())
45 [[maybe_unused]] auto res = sp.front();
46 }
47
48 struct A{};
49 constexpr int iArr1[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
50 int iArr2[] = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19};
51
main(int,char **)52 int main(int, char**)
53 {
54 static_assert(testConstexprSpan(std::span<const int>(iArr1, 1)), "");
55 static_assert(testConstexprSpan(std::span<const int>(iArr1, 2)), "");
56 static_assert(testConstexprSpan(std::span<const int>(iArr1, 3)), "");
57 static_assert(testConstexprSpan(std::span<const int>(iArr1, 4)), "");
58
59 static_assert(testConstexprSpan(std::span<const int, 1>(iArr1, 1)), "");
60 static_assert(testConstexprSpan(std::span<const int, 2>(iArr1, 2)), "");
61 static_assert(testConstexprSpan(std::span<const int, 3>(iArr1, 3)), "");
62 static_assert(testConstexprSpan(std::span<const int, 4>(iArr1, 4)), "");
63
64
65 testRuntimeSpan(std::span<int>(iArr2, 1));
66 testRuntimeSpan(std::span<int>(iArr2, 2));
67 testRuntimeSpan(std::span<int>(iArr2, 3));
68 testRuntimeSpan(std::span<int>(iArr2, 4));
69
70
71 testRuntimeSpan(std::span<int, 1>(iArr2, 1));
72 testRuntimeSpan(std::span<int, 2>(iArr2, 2));
73 testRuntimeSpan(std::span<int, 3>(iArr2, 3));
74 testRuntimeSpan(std::span<int, 4>(iArr2, 4));
75
76 std::string s;
77 testRuntimeSpan(std::span<std::string> (&s, 1));
78 testRuntimeSpan(std::span<std::string, 1>(&s, 1));
79
80 std::span<int, 0> sp;
81 testEmptySpan(sp);
82
83 return 0;
84 }
85