bf95a0cd20
Found while running libc++'s test suite with MSVC's STL, where we use both Clang and MSVC's compiler. libc++'s test suite has started using some C++23 Core Language features that MSVC hasn't implemented yet. When avoiding these features costs just a tiny bit of syntax, I would like to ask libc++ to consider making that change in the interest of practical portability, at least until MSVC catches up. If there's no desire to do so, then I could skip the affected tests, but that would make me a slightly sad kitty.
86 lines
2.3 KiB
C++
86 lines
2.3 KiB
C++
//===----------------------------------------------------------------------===//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
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// constexpr bool has_value() const noexcept;
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#include <cassert>
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#include <concepts>
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#include <expected>
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#include <optional>
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#include <type_traits>
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#include <utility>
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#include "test_macros.h"
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#include "../../types.h"
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// Test noexcept
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template <class T>
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concept HasValueNoexcept =
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requires(T t) {
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{ t.has_value() } noexcept;
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};
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struct Foo {};
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static_assert(!HasValueNoexcept<Foo>);
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static_assert(HasValueNoexcept<std::expected<int, int>>);
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static_assert(HasValueNoexcept<const std::expected<int, int>>);
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constexpr bool test() {
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// has_value
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{
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const std::expected<int, int> e(5);
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assert(e.has_value());
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}
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// !has_value
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{
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const std::expected<int, int> e(std::unexpect, 5);
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assert(!e.has_value());
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}
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// The following tests check that the "has_value" flag is not overwritten
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// by the constructor of the value. This could happen because the flag is
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// stored in the tail padding of the value.
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//
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// The first test is a simplified version of the real code where this was
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// first observed.
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//
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// The other tests use a synthetic struct that clobbers its tail padding
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// on construction, making the issue easier to reproduce.
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//
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// See https://github.com/llvm/llvm-project/issues/68552 and the linked PR.
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{
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auto f1 = []() -> std::expected<std::optional<int>, long> { return 0; };
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auto f2 = [&f1]() -> std::expected<std::optional<int>, int> {
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return f1().transform_error([](auto) { return 0; });
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};
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auto e = f2();
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assert(e.has_value());
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}
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{
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const std::expected<TailClobberer<0>, bool> e = {};
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// clang-cl does not support [[no_unique_address]] yet.
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#if !(defined(TEST_COMPILER_CLANG) && defined(_MSC_VER))
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LIBCPP_STATIC_ASSERT(sizeof(TailClobberer<0>) == sizeof(e));
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#endif
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assert(e.has_value());
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}
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return true;
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}
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int main(int, char**) {
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test();
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static_assert(test());
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return 0;
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}
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