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72 lines
2.6 KiB
72 lines
2.6 KiB
// Copyright 2020 The Pigweed Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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// This file provides adapters for newer C++ language features so that they can
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// be used in older versions of C++ (though the code will not function exactly
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// the same). This file is not on an include path and is intended to be used
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// with -include when compiling C++.
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//
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// pw_polyfill/language_feature_macros.h provides macro wrappers for a few
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// specific uses of modern C++ keywords.
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#pragma once
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// C++11 is required for the features in this header.
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#if defined(__cplusplus) && __cplusplus >= 201103L
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// If consteval is not supported, use constexpr. This does not guarantee
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// compile-time execution, but works equivalently in constant expressions.
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#ifndef __cpp_consteval
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#define consteval constexpr
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#endif // __cpp_consteval
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// If constinit is not supported, use a compiler attribute or omit it. If
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// omitted, the compiler may still constant initialize the variable, but there
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// is no guarantee.
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#ifndef __cpp_constinit
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#ifdef __clang__
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#define constinit [[clang::require_constant_initialization]]
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#else
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#define constinit
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#endif // __clang__
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#endif // __cpp_constinit
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// This is an adapter for supporting static_assert with a single argument in
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// C++11 or C++14. Macros don't correctly parse commas in template expressions,
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// so the static_assert arguments are passed to an overloaded C++ function. The
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// full stringified static_assert arguments are used as the message.
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#if __cpp_static_assert < 201411L
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#undef __cpp_static_assert
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#define __cpp_static_assert 201411L
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#define static_assert(...) \
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static_assert(::pw::polyfill::internal::StaticAssertExpression(__VA_ARGS__), \
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#__VA_ARGS__)
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namespace pw {
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namespace polyfill {
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namespace internal {
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constexpr bool StaticAssertExpression(bool expression) { return expression; }
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constexpr bool StaticAssertExpression(bool expression, const char*) {
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return expression;
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}
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} // namespace internal
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} // namespace polyfill
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} // namespace pw
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#endif // __cpp_static_assert < 201411L
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#endif // defined(__cplusplus) && __cplusplus >= 201103L
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