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

This is to make it easier to determine the site Tasks are posted from in release builds, especially when only a minidump is available. It should help diagnose http://crbug.com/81499.

I added a debug function to alias variables so that the optimizer will not strip them out if they are not live.

The semantics of the MessageLoop::PostTask functions is changed and it is wrong but I am not sure what semantics are intended. It seems location information was no longer being tracked for Tasks wrapped as Closures and I don't know if this was intended. PTAL. Update: this has since been fixed.

TEST=Set breakpoint in TaskClosureAdapter::Run and very that the post site can be located in an optimized build.
BUG=81499
Review URL: http://codereview.chromium.org/7039020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@85991 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 40 insertions, 0 deletions

diff --git a/base/debug/alias.cc b/base/debug/alias.cc
new file mode 100644
index 0000000..04122fb
--- /dev/null
+++ b/base/debug/alias.cc
@@ -0,0 +1,20 @@
+// 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/debug/alias.h"
+#include "build/build_config.h"
+
+namespace base {
+namespace debug {
+
+namespace {
+const void* g_global;
+}
+
+void Alias(const void* var) {
+  g_global = var;
+}
+
+}  // namespace debug
+}  // namespace base
diff --git a/base/debug/alias.h b/base/debug/alias.h
new file mode 100644
index 0000000..957afdb
--- /dev/null
+++ b/base/debug/alias.h
@@ -0,0 +1,20 @@
+// 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.
+
+#ifndef BASE_DEBUG_ALIAS_H_
+#define BASE_DEBUG_ALIAS_H_
+#pragma once
+
+namespace base {
+namespace debug {
+
+// Make the optimizer think that var is aliased. This is to prevent it from
+// optimizing out variables that that would not otherwise be live at the point
+// of a potential crash.
+void Alias(const void* var);
+
+}  // namespace debug
+}  // namespace base
+
+#endif  // BASE_DEBUG_ALIAS_H_