70cb7f749d
Using bit_cast on pointers does not accomplish anything useful, and obscures what might be incorrect behavior. Do not allow base::bit_cast to be misused in that way. Bug: 1506769 Change-Id: Ib9f3acf954c5537c7520f72827854de81afda382 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5094596 Reviewed-by: Hongchan Choi <hongchan@chromium.org> Reviewed-by: Ilya Sherman <isherman@chromium.org> Reviewed-by: Will Harris <wfh@chromium.org> Reviewed-by: danakj <danakj@chromium.org> Reviewed-by: Kentaro Hara <haraken@chromium.org> Reviewed-by: Dominic Battre <battre@chromium.org> Commit-Queue: Avi Drissman <avi@chromium.org> Reviewed-by: Adam Rice <ricea@chromium.org> Reviewed-by: Robert Sesek <rsesek@chromium.org> Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com> Cr-Commit-Position: refs/heads/main@{#1236404}
46 lines
1.7 KiB
C++
46 lines
1.7 KiB
C++
// Copyright 2016 The Chromium Authors
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_BIT_CAST_H_
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#define BASE_BIT_CAST_H_
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#include <type_traits>
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namespace base {
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// This is an equivalent to C++20's std::bit_cast<>(), but with additional
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// warnings. It morally does what `*reinterpret_cast<Dest*>(&source)` does, but
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// the cast/deref pair is undefined behavior, while bit_cast<>() isn't.
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//
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// This is not a magic "get out of UB free" card. This must only be used on
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// values, not on references or pointers. For pointers, use
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// reinterpret_cast<>(), and then look at https://eel.is/c++draft/basic.lval#11
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// as that's probably UB also.
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template <class Dest, class Source>
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constexpr Dest bit_cast(const Source& source) {
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static_assert(!std::is_pointer_v<Source>,
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"bit_cast must not be used on pointer types");
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static_assert(!std::is_pointer_v<Dest>,
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"bit_cast must not be used on pointer types");
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static_assert(!std::is_reference_v<Source>,
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"bit_cast must not be used on reference types");
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static_assert(!std::is_reference_v<Dest>,
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"bit_cast must not be used on reference types");
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static_assert(
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sizeof(Dest) == sizeof(Source),
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"bit_cast requires source and destination types to be the same size");
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static_assert(std::is_trivially_copyable_v<Source>,
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"bit_cast requires the source type to be trivially copyable");
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static_assert(
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std::is_trivially_copyable_v<Dest>,
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"bit_cast requires the destination type to be trivially copyable");
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return __builtin_bit_cast(Dest, source);
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}
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} // namespace base
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#endif // BASE_BIT_CAST_H_
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