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// Copyright (c) 2012 The Chromium 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.
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#ifndef BASE_DEBUG_LEAK_TRACKER_H_
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#define BASE_DEBUG_LEAK_TRACKER_H_
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// Only enable leak tracking in debug builds.
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#define ENABLE_LEAK_TRACKER
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#ifdef ENABLE_LEAK_TRACKER
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#include "base/containers/linked_list.h"
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#include "base/debug/stack_trace.h"
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#include "base/logging.h"
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#endif // ENABLE_LEAK_TRACKER
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// LeakTracker is a helper to verify that all instances of a class
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// have been destroyed.
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// It is particularly useful for classes that are bound to a single thread --
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// before destroying that thread, one can check that there are no remaining
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// instances of that class.
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// For example, to enable leak tracking for class net::URLRequest, start by
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// adding a member variable of type LeakTracker<net::URLRequest>.
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// base::LeakTracker<URLRequest> leak_tracker_;
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// Next, when we believe all instances of net::URLRequest have been deleted:
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// LeakTracker<net::URLRequest>::CheckForLeaks();
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// Should the check fail (because there are live instances of net::URLRequest),
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// then the allocation callstack for each leaked instances is dumped to
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// If ENABLE_LEAK_TRACKER is not defined, then the check has no effect.
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#ifndef ENABLE_LEAK_TRACKER
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// If leak tracking is disabled, do nothing.
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static void CheckForLeaks() {}
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static int NumLiveInstances() { return -1; }
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// If leak tracking is enabled we track where the object was allocated from.
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class LeakTracker : public LinkNode<LeakTracker<T> > {
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instances()->Append(this);
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this->RemoveFromList();
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static void CheckForLeaks() {
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// Walk the allocation list and print each entry it contains.
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// Copy the first 3 leak allocation callstacks onto the stack.
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// This way if we hit the CHECK() in a release build, the leak
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// information will be available in mini-dump.
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const size_t kMaxStackTracesToCopyOntoStack = 3;
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StackTrace stacktraces[kMaxStackTracesToCopyOntoStack];
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for (LinkNode<LeakTracker<T> >* node = instances()->head();
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node != instances()->end();
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node = node->next()) {
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StackTrace& allocation_stack = node->value()->allocation_stack_;
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if (count < kMaxStackTracesToCopyOntoStack)
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stacktraces[count] = allocation_stack;
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if (LOG_IS_ON(ERROR)) {
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LOG_STREAM(ERROR) << "Leaked " << node << " which was allocated by:";
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allocation_stack.OutputToStream(&LOG_STREAM(ERROR));
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// Hack to keep |stacktraces| and |count| alive (so compiler
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// doesn't optimize it out, and it will appear in mini-dumps).
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if (count == 0x1234) {
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for (size_t i = 0; i < kMaxStackTracesToCopyOntoStack; ++i)
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stacktraces[i].Print();
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static int NumLiveInstances() {
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// Walk the allocation list and count how many entries it has.
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for (LinkNode<LeakTracker<T> >* node = instances()->head();
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node != instances()->end();
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node = node->next()) {
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// Each specialization of LeakTracker gets its own static storage.
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static LinkedList<LeakTracker<T> >* instances() {
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static LinkedList<LeakTracker<T> > list;
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StackTrace allocation_stack_;
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#endif // ENABLE_LEAK_TRACKER
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#endif // BASE_DEBUG_LEAK_TRACKER_H_