38 lines
1.6 KiB
C
38 lines
1.6 KiB
C
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/*
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* Copyright (c) 2020 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef RTC_BASE_SYSTEM_NO_UNIQUE_ADDRESS_H_
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#define RTC_BASE_SYSTEM_NO_UNIQUE_ADDRESS_H_
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// RTC_NO_UNIQUE_ADDRESS is a portable annotation to tell the compiler that
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// a data member need not have an address distinct from all other non-static
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// data members of its class.
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// It allows empty types to actually occupy zero bytes as class members,
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// instead of occupying at least one byte just so that they get their own
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// address. There is almost never any reason not to use it on class members
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// that could possibly be empty.
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// The macro expands to [[no_unique_address]] if the compiler supports the
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// attribute, it expands to nothing otherwise.
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// Clang should supports this attribute since C++11, while other compilers
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// should add support for it starting from C++20. Among clang compilers,
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// clang-cl doesn't support it yet and support is unclear also when the target
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// platform is iOS.
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#ifndef __has_cpp_attribute
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#define __has_cpp_attribute(x) 0
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#endif
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#if __has_cpp_attribute(no_unique_address)
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// NOLINTNEXTLINE(whitespace/braces)
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#define RTC_NO_UNIQUE_ADDRESS [[no_unique_address]]
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#else
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#define RTC_NO_UNIQUE_ADDRESS
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#endif
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#endif // RTC_BASE_SYSTEM_NO_UNIQUE_ADDRESS_H_
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