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 9 // UNSUPPORTED: c++03, c++11, c++14, c++17 10 11 // <iterator> 12 // template <class C> constexpr auto ssize(const C& c) 13 // -> common_type_t<ptrdiff_t, make_signed_t<decltype(c.size())>>; // C++20 14 // template <class T, ptrdiff_t> constexpr ptrdiff_t ssize(const T (&array)[N]) noexcept; // C++20 15 16 #include <iterator> 17 #include <cassert> 18 #include <vector> 19 #include <array> 20 #include <list> 21 #include <initializer_list> 22 #include <string_view> 23 24 #include "test_macros.h" 25 26 // Ignore warning about std::numeric_limits comparisons being tautological. 27 #ifdef __GNUC__ 28 #pragma GCC diagnostic ignored "-Wtype-limits" 29 #endif 30 31 struct short_container { 32 uint16_t size() const { return 60000; } // not noexcept 33 }; 34 35 template<typename C> 36 void test_container(C& c) 37 { 38 // Can't say noexcept here because the container might not be 39 static_assert( std::is_signed_v<decltype(std::ssize(c))>, ""); 40 assert ( std::ssize(c) == static_cast<decltype(std::ssize(c))>(c.size())); 41 } 42 43 template<typename C> 44 void test_const_container(const C& c) 45 { 46 // Can't say noexcept here because the container might not be 47 static_assert( std::is_signed_v<decltype(std::ssize(c))>, ""); 48 assert ( std::ssize(c) == static_cast<decltype(std::ssize(c))>(c.size())); 49 } 50 51 template<typename T> 52 void test_const_container(const std::initializer_list<T>& c) 53 { 54 LIBCPP_ASSERT_NOEXCEPT(std::ssize(c)); // our std::ssize is conditionally noexcept 55 static_assert( std::is_signed_v<decltype(std::ssize(c))>, ""); 56 assert ( std::ssize(c) == static_cast<decltype(std::ssize(c))>(c.size())); 57 } 58 59 template<typename T> 60 void test_container(std::initializer_list<T>& c) 61 { 62 LIBCPP_ASSERT_NOEXCEPT(std::ssize(c)); // our std::ssize is conditionally noexcept 63 static_assert( std::is_signed_v<decltype(std::ssize(c))>, ""); 64 assert ( std::ssize(c) == static_cast<decltype(std::ssize(c))>(c.size())); 65 } 66 67 template<typename T, size_t Sz> 68 void test_const_array(const T (&array)[Sz]) 69 { 70 ASSERT_NOEXCEPT(std::ssize(array)); 71 static_assert( std::is_signed_v<decltype(std::ssize(array))>, ""); 72 assert ( std::ssize(array) == Sz ); 73 } 74 75 int main(int, char**) 76 { 77 std::vector<int> v; v.push_back(1); 78 std::list<int> l; l.push_back(2); 79 std::array<int, 1> a; a[0] = 3; 80 std::initializer_list<int> il = { 4 }; 81 using SSize = std::common_type_t<std::ptrdiff_t, std::make_signed_t<std::size_t>>; 82 test_container ( v ); 83 ASSERT_SAME_TYPE(SSize, decltype(std::ssize(v))); 84 test_container ( l ); 85 ASSERT_SAME_TYPE(SSize, decltype(std::ssize(l))); 86 test_container ( a ); 87 ASSERT_SAME_TYPE(SSize, decltype(std::ssize(a))); 88 test_container ( il ); 89 ASSERT_SAME_TYPE(SSize, decltype(std::ssize(il))); 90 91 test_const_container ( v ); 92 test_const_container ( l ); 93 test_const_container ( a ); 94 test_const_container ( il ); 95 96 std::string_view sv{"ABC"}; 97 test_container ( sv ); 98 ASSERT_SAME_TYPE(SSize, decltype(std::ssize(sv))); 99 test_const_container ( sv ); 100 101 static constexpr int arrA [] { 1, 2, 3 }; 102 ASSERT_SAME_TYPE(ptrdiff_t, decltype(std::ssize(arrA))); 103 static_assert( std::is_signed_v<decltype(std::ssize(arrA))>, ""); 104 test_const_array ( arrA ); 105 106 // From P1227R2: 107 // Note that the code does not just return the std::make_signed variant of 108 // the container's size() method, because it's conceivable that a container 109 // might choose to represent its size as a uint16_t, supporting up to 110 // 65,535 elements, and it would be a disaster for std::ssize() to turn a 111 // size of 60,000 into a size of -5,536. 112 113 short_container sc; 114 // is the return type signed? Is it big enough to hold 60K? 115 // is the "signed version" of sc.size() too small? 116 static_assert( std::is_signed_v< decltype(std::ssize(sc))>, ""); 117 static_assert( std::numeric_limits< decltype(std::ssize(sc))>::max() > 60000, ""); 118 static_assert( std::numeric_limits<std::make_signed_t<decltype(std:: size(sc))>>::max() < 60000, ""); 119 assert (std::ssize(sc) == 60000); 120 LIBCPP_ASSERT_NOT_NOEXCEPT(std::ssize(sc)); 121 122 return 0; 123 } 124