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// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_THREADING_THREAD_LOCAL_INTERNAL_H_
#define BASE_THREADING_THREAD_LOCAL_INTERNAL_H_
#if DCHECK_IS_ON()
#include <atomic>
#include <memory>
#include "base/macros.h"
#include "base/threading/thread_local_storage.h"
namespace base {
namespace internal {
// A version of ThreadLocalOwnedPointer which verifies that it's only destroyed
// when no threads, other than the one it is destroyed on, have remaining state
// set in it. A ThreadLocalOwnedPointer instance being destroyed too early would
// result in leaks per unregistering the TLS slot (and thus the DeleteTlsPtr
// hook).
template <typename T>
class CheckedThreadLocalOwnedPointer {
public:
CheckedThreadLocalOwnedPointer() = default;
~CheckedThreadLocalOwnedPointer() {
Set(nullptr);
DCHECK_EQ(num_assigned_threads_.load(std::memory_order_relaxed), 0)
<< "Memory leak: Must join all threads or release all associated "
"thread-local slots before ~ThreadLocalOwnedPointer";
}
T* Get() const {
PtrTracker* const ptr_tracker = static_cast<PtrTracker*>(slot_.Get());
return ptr_tracker ? ptr_tracker->ptr_.get() : nullptr;
}
void Set(std::unique_ptr<T> ptr) {
delete static_cast<PtrTracker*>(slot_.Get());
if (ptr)
slot_.Set(new PtrTracker(this, std::move(ptr)));
else
slot_.Set(nullptr);
}
private:
struct PtrTracker {
public:
PtrTracker(CheckedThreadLocalOwnedPointer<T>* outer, std::unique_ptr<T> ptr)
: outer_(outer), ptr_(std::move(ptr)) {
outer_->num_assigned_threads_.fetch_add(1, std::memory_order_relaxed);
}
~PtrTracker() {
outer_->num_assigned_threads_.fetch_sub(1, std::memory_order_relaxed);
}
CheckedThreadLocalOwnedPointer<T>* const outer_;
const std::unique_ptr<T> ptr_;
};
static void DeleteTlsPtr(void* ptr) { delete static_cast<PtrTracker*>(ptr); }
ThreadLocalStorage::Slot slot_{&DeleteTlsPtr};
std::atomic_int num_assigned_threads_{0};
DISALLOW_COPY_AND_ASSIGN(CheckedThreadLocalOwnedPointer<T>);
};
} // namespace internal
} // namespace base
#endif // DCHECK_IS_ON()
#endif // BASE_THREADING_THREAD_LOCAL_INTERNAL_H_
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