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9b4dc24721
Configure the runtime to build with -Wglobal-constructors, and Lazy-fy almost everything that gets flagged. (I gave "swift_isaMask" a pass since that's almost definitely hot enough to warrant a static initialization.) Make some improvements to the Lazy wrapper, using aligned_storage to ensure that it's trivially constructed and destructed. Swift SVN r28199
76 lines
1.9 KiB
C++
76 lines
1.9 KiB
C++
//===--- Lazy.h - A lazily-initialized object -----------------------------===//
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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 - 2015 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 http://swift.org/LICENSE.txt for license information
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// See http://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_LAZY_H
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#define SWIFT_RUNTIME_LAZY_H
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#ifdef __APPLE__
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#include <dispatch/dispatch.h>
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#else
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#include <mutex>
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#endif
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#include "swift/Basic/type_traits.h"
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namespace swift {
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/// A template for lazily-constructed, zero-initialized, leaked-on-exit
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/// global objects.
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template <class T> class Lazy {
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typename std::aligned_storage<sizeof(T), alignof(T)>::type Value;
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#ifdef __APPLE__
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dispatch_once_t OnceToken;
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#else
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std::once_flag OnceToken;
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#endif
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public:
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T &get();
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/// Get the value, assuming it must have already been initialized by this
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/// point.
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T &unsafeGetAlreadyInitialized() {
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return *reinterpret_cast<T*>(&Value);
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}
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Lazy() = default;
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private:
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static void lazyInitCallback(void *Argument) {
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auto self = reinterpret_cast<Lazy *>(Argument);
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::new (&self->unsafeGetAlreadyInitialized()) T();
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}
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Lazy(const Lazy &) = delete;
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Lazy &operator=(const Lazy &) = delete;
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};
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template<typename T>
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inline T& Lazy<T>::get() {
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static_assert(IsTriviallyConstructible<Lazy<T>>::value,
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"Lazy must be trivially default constructible");
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static_assert(IsTriviallyDestructible<Lazy<T>>::value,
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"Lazy must be trivially destructible");
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#ifdef __APPLE__
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dispatch_once_f(&OnceToken, this, lazyInitCallback);
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#else
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std::call_once(OnceToken, lazyInitCallback, this);
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#endif
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return unsafeGetAlreadyInitialized();
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}
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} // namespace swift
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#endif // SWIFT_RUNTIME_LAZY_H
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