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f1b859c9a5
Remove the multiple definitions of `std::bit_cast` into a header. While this is still not great, it does reduce the duplication. This also silently works towards reducing a bit of the UB introduced here by adding an inline namespace for `std` which you are not technically allowed to use. However, by doing this, we have a clear migration path away from this once we adopt C++20.
46 lines
1.5 KiB
C++
46 lines
1.5 KiB
C++
//===---- STLCompatibility.h - Runtime C++ Compatibiltiy Stubs --*- C++ -*-===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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#ifndef SWIFT_RUNTIME_STL_COMPATIBILITY_H
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#define SWIFT_RUNTIME_STL_COMPATIBILITY_H
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#if __cplusplus >= 202002l || defined(__cpp_lib_bit_cast)
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#include <bit>
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#else
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#include <cstdint>
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#include <cstring>
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#include <memory>
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#include <type_traits>
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namespace std {
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inline namespace __swift {
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template <typename Destination, typename Source>
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std::enable_if_t<sizeof(Destination) == sizeof(Source) &&
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std::is_trivially_copyable_v<Source> &&
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std::is_trivially_copyable_v<Destination>, Destination>
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bit_cast(const Source &src) noexcept {
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static_assert(std::is_trivially_constructible_v<Destination>,
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"The destination type must be trivially constructible");
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Destination dst;
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if constexpr (std::is_pointer_v<Source> || std::is_pointer_v<Destination>)
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std::memcpy(reinterpret_cast<uintptr_t *>(&dst),
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reinterpret_cast<const uintptr_t *>(&src), sizeof(Destination));
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else
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std::memcpy(&dst, &src, sizeof(Destination));
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return dst;
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}
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}
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}
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#endif
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#endif
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