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e829478c6a
cl/713346733 changed the type of some variables to pointers, but didn't adjust the placement new statements. From pkasting@: "I suspect your code is wrong and will crash. An array is a pointer, so taking its address also gives a pointer, which is why it compiles; but the value of that pointer is different. You're no longer providing the address of the storage, but rather the address of the array pointer." PiperOrigin-RevId: 717926210
51 lines
1.7 KiB
C++
51 lines
1.7 KiB
C++
// Copyright (c) 2018 The LevelDB Authors. All rights reserved.
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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. See the AUTHORS file for names of contributors.
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#ifndef STORAGE_LEVELDB_UTIL_NO_DESTRUCTOR_H_
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#define STORAGE_LEVELDB_UTIL_NO_DESTRUCTOR_H_
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#include <cstddef>
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#include <type_traits>
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#include <utility>
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namespace leveldb {
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// Wraps an instance whose destructor is never called.
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//
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// This is intended for use with function-level static variables.
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template <typename InstanceType>
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class NoDestructor {
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public:
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template <typename... ConstructorArgTypes>
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explicit NoDestructor(ConstructorArgTypes&&... constructor_args) {
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static_assert(sizeof(instance_storage_) >= sizeof(InstanceType),
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"instance_storage_ is not large enough to hold the instance");
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static_assert(std::is_standard_layout_v<NoDestructor<InstanceType>>);
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static_assert(
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offsetof(NoDestructor, instance_storage_) % alignof(InstanceType) == 0,
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"instance_storage_ does not meet the instance's alignment requirement");
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static_assert(
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alignof(NoDestructor<InstanceType>) % alignof(InstanceType) == 0,
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"instance_storage_ does not meet the instance's alignment requirement");
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new (instance_storage_)
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InstanceType(std::forward<ConstructorArgTypes>(constructor_args)...);
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}
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~NoDestructor() = default;
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NoDestructor(const NoDestructor&) = delete;
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NoDestructor& operator=(const NoDestructor&) = delete;
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InstanceType* get() {
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return reinterpret_cast<InstanceType*>(&instance_storage_);
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}
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private:
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alignas(InstanceType) char instance_storage_[sizeof(InstanceType)];
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};
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} // namespace leveldb
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#endif // STORAGE_LEVELDB_UTIL_NO_DESTRUCTOR_H_
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