Store a stacktrace of PrefService destruction in PrefChangeRegistrar

base/prefs/pref_change_registrar.cc

 // Copyright (c) 2010 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/prefs/pref_change_registrar.h"
 
 #include "base/bind.h"
+// TODO(battre): Delete this. See crbug.com/373435

[engedy, 2014/05/16 15:19:58]

nit: period to the end of the comment.

[battre, 2014/05/16 15:58:37]

Done.

+#include "base/debug/alias.h"
 #include "base/logging.h"
 #include "base/prefs/pref_service.h"
 
 PrefChangeRegistrar::PrefChangeRegistrar() : service_(NULL) {}
 
 PrefChangeRegistrar::~PrefChangeRegistrar() {
   // If you see an invalid memory access in this destructor, this
   // PrefChangeRegistrar might be subscribed to an OffTheRecordProfileImpl that
   // has been destroyed. This should not happen any more but be warned.
   // Feel free to contact battre@chromium.org in case this happens.
@@ skipping 23 matching lines @@
 }
 
 void PrefChangeRegistrar::Remove(const char* path) {
   DCHECK(IsObserved(path));
 
   observers_.erase(path);
   service_->RemovePrefObserver(path, this);
 }
 
 void PrefChangeRegistrar::RemoveAll() {
+  // TODO(battre): Delete this. See crbug.com/373435.
+  if (!observers_.empty() && !pref_service_destruction_.empty()) {
+    // The PrefService is already destroyed, so the following call to
+    // service_->RemovePrefObserver would crash anyway. When the PrefService
+    // was destroyed, it stored a stacktrack of the destruction in

[engedy, 2014/05/16 15:19:58]

nit: s/stacktrack/stack trace

[battre, 2014/05/16 15:58:37]

Done.

+    // pref_service_destruction_. We save this on the stack in the minidump to
+    // understand what happens.
+    char tmp[2048];
+    const int copy =
+        std::min<int>(sizeof(tmp) - 1, pref_service_destruction_.length());

[engedy, 2014/05/16 15:19:58]

Could we use strncat() here, like so:

char tmp[2048] = {};
strncat(tmp, pref_service_destruction_.c_str(), sizeof(tmp)-1);

[battre, 2014/05/16 15:58:37]

Done.

+    memcpy(tmp, pref_service_destruction_.c_str(), copy);
+    tmp[copy] = '\0';
+    base::debug::Alias(tmp);
+    CHECK(false) << tmp;
+  }
+
   for (ObserverMap::const_iterator it = observers_.begin();
        it != observers_.end(); ++it) {
     service_->RemovePrefObserver(it->first.c_str(), this);
   }
 
   observers_.clear();
 }
 
 bool PrefChangeRegistrar::IsEmpty() const {
   return observers_.empty();
@@ skipping 13 matching lines @@
   }
   return false;
 }
 
 void PrefChangeRegistrar::OnPreferenceChanged(PrefService* service,
                                               const std::string& pref) {
   if (IsObserved(pref))
     observers_[pref].Run(pref);
 }
 
+// TODO(battre): Delete this. See crbug.com/373435.
+void PrefChangeRegistrar::SetPrefServiceDestructionTrace(
+    const std::string& stacktrace) {

[engedy, 2014/05/16 15:19:58]

nit: stack_trace.

[battre, 2014/05/16 15:58:37]

Done.

+  pref_service_destruction_ = stacktrace;
+}
+
 void PrefChangeRegistrar::InvokeUnnamedCallback(const base::Closure& callback,
                                                 const std::string& pref_name) {
   callback.Run();
 }
 
 PrefService* PrefChangeRegistrar::prefs() {
   return service_;
 }
 
 const PrefService* PrefChangeRegistrar::prefs() const {
   return service_;
 }