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//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
// <functional>
// namespace placeholders {
// // M is the implementation-defined number of placeholders
// extern unspecified _1;
// extern unspecified _2;
// .
// .
// .
// extern unspecified _Mp;
// }
// The Standard recommends implementing them as `inline constexpr` in C++17.
//
// Libc++ implements the placeholders as `extern const` in all standard modes
// to avoid an ABI break in C++03: making them `inline constexpr` requires removing
// their definition in the shared library to avoid ODR violations, which is an
// ABI break.
//
// Concretely, `extern const` is almost indistinguishable from constexpr for the
// placeholders since they are empty types.
#include <functional>
#include <type_traits>
#include "test_macros.h"
template <class T>
TEST_CONSTEXPR_CXX17 void test(const T& t) {
// Test default constructible.
{
T x; (void)x;
}
// Test copy constructible.
{
T x = t; (void)x;
static_assert(std::is_nothrow_copy_constructible<T>::value, "");
static_assert(std::is_nothrow_move_constructible<T>::value, "");
}
// It is implementation-defined whether placeholder types are CopyAssignable.
// CopyAssignable placeholders' copy assignment operators shall not throw exceptions.
#ifdef _LIBCPP_VERSION
{
T x;
x = t;
static_assert(std::is_nothrow_copy_assignable<T>::value, "");
static_assert(std::is_nothrow_move_assignable<T>::value, "");
}
#endif
}
TEST_CONSTEXPR_CXX17 bool test_all() {
test(std::placeholders::_1);
test(std::placeholders::_2);
test(std::placeholders::_3);
test(std::placeholders::_4);
test(std::placeholders::_5);
test(std::placeholders::_6);
test(std::placeholders::_7);
test(std::placeholders::_8);
test(std::placeholders::_9);
test(std::placeholders::_10);
return true;
}
int main(int, char**) {
test_all();
#if TEST_STD_VER >= 17
static_assert(test_all(), "");
#endif
return 0;
}
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