ba87515fea
Currently, the library-internal feature test macros are only defined if the feature is not available, and always have the prefix `_LIBCPP_HAS_NO_`. This patch changes that, so that they are always defined and have the prefix `_LIBCPP_HAS_` instead. This changes the canonical use of these macros to `#if _LIBCPP_HAS_FEATURE`, which means that using an undefined macro (e.g. due to a missing include) is diagnosed now. While this is rather unlikely currently, a similar change in `<__configuration/availability.h>` caught a few bugs. This also improves readability, since it removes the double-negation of `#ifndef _LIBCPP_HAS_NO_FEATURE`. The current patch only touches the macros defined in `<__config>`. If people are happy with this approach, I'll make a follow-up PR to also change the macros defined in `<__config_site>`.
43 lines
1.4 KiB
C++
43 lines
1.4 KiB
C++
//===----------------------------------------------------------------------===//
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//
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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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// Define ~mutex.
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//
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// On some platforms ~mutex has been made trivial and the definition is only
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// provided for ABI compatibility.
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//
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// In order to avoid ODR violations within libc++ itself, we need to ensure
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// that *nothing* sees the non-trivial mutex declaration. For this reason
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// we re-declare the entire class in this file instead of using
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// _LIBCPP_BUILDING_LIBRARY to change the definition in the headers.
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#include <__config>
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#include <__thread/support.h>
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#if _LIBCPP_ABI_VERSION == 1 || !_LIBCPP_HAS_TRIVIAL_MUTEX_DESTRUCTION
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# define NEEDS_MUTEX_DESTRUCTOR
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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#ifdef NEEDS_MUTEX_DESTRUCTOR
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class _LIBCPP_EXPORTED_FROM_ABI mutex {
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__libcpp_mutex_t __m_ = _LIBCPP_MUTEX_INITIALIZER;
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public:
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_LIBCPP_ALWAYS_INLINE _LIBCPP_HIDE_FROM_ABI constexpr mutex() = default;
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mutex(const mutex&) = delete;
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mutex& operator=(const mutex&) = delete;
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~mutex() noexcept;
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};
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mutex::~mutex() noexcept { __libcpp_mutex_destroy(&__m_); }
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#endif // !NEEDS_MUTEX_DESTRUCTOR
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_LIBCPP_END_NAMESPACE_STD
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