//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03, c++11
// <utility>
// exchange
// template<class T, class U=T>
// constexpr T // constexpr after C++17
// exchange(T& obj, U&& new_value)
// noexcept(is_nothrow_move_constructible<T>::value && is_nothrow_assignable<T&, U>::value);
#include <utility>
#include <cassert>
#include <string>
#include "test_macros.h"
#if TEST_STD_VER > 17
TEST_CONSTEXPR bool test_constexpr() {
int v = 12;
if (12 != std::exchange(v,23) || v != 23)
return false;
if (23 != std::exchange(v,static_cast<short>(67)) || v != 67)
return false;
if (67 != std::exchange<int, short>(v, {}) || v != 0)
return false;
return true;
}
#endif
template<bool Move, bool Assign>
struct TestNoexcept {
TestNoexcept() = default;
TestNoexcept(const TestNoexcept&);
TestNoexcept(TestNoexcept&&) noexcept(Move);
TestNoexcept& operator=(const TestNoexcept&);
TestNoexcept& operator=(TestNoexcept&&) noexcept(Assign);
};
constexpr bool test_noexcept() {
{
int x = 42;
ASSERT_NOEXCEPT(std::exchange(x, 42));
}
{
TestNoexcept<true, true> x;
ASSERT_NOEXCEPT(std::exchange(x, std::move(x)));
ASSERT_NOT_NOEXCEPT(std::exchange(x, x)); // copy-assignment is not noexcept
}
{
TestNoexcept<true, false> x;
ASSERT_NOT_NOEXCEPT(std::exchange(x, std::move(x)));
}
{
TestNoexcept<false, true> x;
ASSERT_NOT_NOEXCEPT(std::exchange(x, std::move(x)));
}
return true;
}
int main(int, char**)
{
{
int v = 12;
assert ( std::exchange ( v, 23 ) == 12 );
assert ( v == 23 );
assert ( std::exchange ( v, static_cast<short>(67) ) == 23 );
assert ( v == 67 );
assert ((std::exchange<int, short> ( v, {} )) == 67 );
assert ( v == 0 );
}
{
bool b = false;
assert ( !std::exchange ( b, true ));
assert ( b );
}
{
const std::string s1 ( "Hi Mom!" );
const std::string s2 ( "Yo Dad!" );
std::string s3 = s1; // Mom
assert ( std::exchange ( s3, s2 ) == s1 );
assert ( s3 == s2 );
assert ( std::exchange ( s3, "Hi Mom!" ) == s2 );
assert ( s3 == s1 );
s3 = s2; // Dad
assert ( std::exchange ( s3, {} ) == s2 );
assert ( s3.size () == 0 );
s3 = s2; // Dad
assert ( std::exchange ( s3, "" ) == s2 );
assert ( s3.size () == 0 );
}
#if TEST_STD_VER > 17
static_assert(test_constexpr());
#endif
static_assert(test_noexcept(), "");
return 0;
}