Tag all tracked objects, including Tasks, with the program counter at the site of FROM_HERE.

base/message_loop.cc

 // Copyright (c) 2011 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.
 
 #include "base/message_loop.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
+#include "base/debug/alias.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/message_pump_default.h"
 #include "base/metrics/histogram.h"
 #include "base/scoped_ptr.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
 #include "base/threading/thread_local.h"
 #include "base/time.h"
 #include "base/tracked_objects.h"
 
@@ skipping 439 matching lines @@
 
   RunTask(pending_task);
   return true;
 }
 
 void MessageLoop::RunTask(const PendingTask& pending_task) {
   DCHECK(nestable_tasks_allowed_);
   // Execute the task and assume the worst: It is probably not reentrant.
   nestable_tasks_allowed_ = false;
 
+  // Before running the task, store the program counter where it was posted
+  // and deliberately alias it to ensure it is on the stack if the task
+  // crashes. Be careful not to assume that the variable itself will have the
+  // expected value when displayed by the optimizer in an optimized build.
+  // Look at a memory dump of the stack.
+  const void* program_counter = pending_task.birth_program_counter;
+  base::debug::Alias(&program_counter);
+
   HistogramEvent(kTaskRunEvent);
   FOR_EACH_OBSERVER(TaskObserver, task_observers_,
                     WillProcessTask(pending_task.time_posted));
   pending_task.task.Run();
   FOR_EACH_OBSERVER(TaskObserver, task_observers_,
                     DidProcessTask(pending_task.time_posted));
 
 #if defined(TRACK_ALL_TASK_OBJECTS)
   if (tracked_objects::ThreadData::IsActive() && pending_task.post_births) {
     tracked_objects::ThreadData::current()->TallyADeath(
@@ skipping 279 matching lines @@
 
 MessageLoop::PendingTask::PendingTask(
     const base::Closure& task,
     const tracked_objects::Location& posted_from,
     TimeTicks delayed_run_time,
     bool nestable)
     : task(task),
       time_posted(TimeTicks::Now()),
       delayed_run_time(delayed_run_time),
       sequence_num(0),
-      nestable(nestable) {
+      nestable(nestable),
+      birth_program_counter(posted_from.program_counter()) {
 #if defined(TRACK_ALL_TASK_OBJECTS)
   if (tracked_objects::ThreadData::IsActive()) {
     tracked_objects::ThreadData* current_thread_data =
         tracked_objects::ThreadData::current();
     if (current_thread_data) {
       post_births = current_thread_data->TallyABirth(posted_from);
     } else {
       // Shutdown started, and this thread wasn't registered.
       post_births = NULL;
     }
@@ skipping 73 matching lines @@
                                            Watcher *delegate) {
   return pump_libevent()->WatchFileDescriptor(
       fd,
       persistent,
       static_cast<base::MessagePumpLibevent::Mode>(mode),
       controller,
       delegate);
 }
 
 #endif