gecko/xpcom/base/nsConsoleService.h
Andrew McCreight 8250bb45f5 Bug 1207368 - Use swap() instead of forget() to remove MessageElement::mMessage. r=froydnj
Using forget() to extract mMessage from MessageElement ends up going
from nsCOMPtr<T> to already_AddRefed<T> to nsCOMPtr<T>. For the second
step, the compiler can't tell that the already_AddRefed<T> came from a
canonical nsCOMPtr, so it calls Assert_NoQueryNeeded() in debug
builds. This in turn causes a QI, which does an AddRef. That is bad
because we're not on the main thread, and mMessage is
main-thread-only, so we get an assertion.

This patch works around that by using swap directly between two
nsCOMPtr<>, which avoids the Assert_NoQueryNeeded().

I called the method "swapMessage" rather than "swap" to emphasize that
we are not swapping the whole MessageElement, but just one part of
it. I find the existing forget() name to be confusing.
2015-10-02 14:47:13 -07:00

119 lines
3.1 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
* nsConsoleService class declaration.
*/
#ifndef __nsconsoleservice_h__
#define __nsconsoleservice_h__
#include "mozilla/Attributes.h"
#include "mozilla/Mutex.h"
#include "nsInterfaceHashtable.h"
#include "nsHashKeys.h"
#include "nsIConsoleService.h"
class nsConsoleService final : public nsIConsoleService,
public nsIObserver
{
public:
nsConsoleService();
nsresult Init();
NS_DECL_THREADSAFE_ISUPPORTS
NS_DECL_NSICONSOLESERVICE
NS_DECL_NSIOBSERVER
void SetIsDelivering()
{
MOZ_ASSERT(NS_IsMainThread());
MOZ_ASSERT(!mDeliveringMessage);
mDeliveringMessage = true;
}
void SetDoneDelivering()
{
MOZ_ASSERT(NS_IsMainThread());
MOZ_ASSERT(mDeliveringMessage);
mDeliveringMessage = false;
}
// This is a variant of LogMessage which allows the caller to determine
// if the message should be output to an OS-specific log. This is used on
// B2G to control whether the message is logged to the android log or not.
enum OutputMode {
SuppressLog,
OutputToLog
};
virtual nsresult LogMessageWithMode(nsIConsoleMessage* aMessage,
OutputMode aOutputMode);
typedef nsInterfaceHashtable<nsISupportsHashKey,
nsIConsoleListener> ListenerHash;
void CollectCurrentListeners(nsCOMArray<nsIConsoleListener>& aListeners);
private:
class MessageElement : public mozilla::LinkedListElement<MessageElement>
{
public:
explicit MessageElement(nsIConsoleMessage* aMessage) : mMessage(aMessage)
{}
nsIConsoleMessage* Get()
{
return mMessage.get();
}
// Swap directly into an nsCOMPtr to avoid spurious refcount
// traffic off the main thread in debug builds from
// NSCAP_ASSERT_NO_QUERY_NEEDED().
void swapMessage(nsCOMPtr<nsIConsoleMessage>& aRetVal)
{
mMessage.swap(aRetVal);
}
~MessageElement();
private:
nsCOMPtr<nsIConsoleMessage> mMessage;
MessageElement(const MessageElement&) = delete;
MessageElement& operator=(const MessageElement&) = delete;
MessageElement(MessageElement&&) = delete;
MessageElement& operator=(MessageElement&&) = delete;
};
~nsConsoleService();
void ClearMessagesForWindowID(const uint64_t innerID);
void ClearMessages();
mozilla::LinkedList<MessageElement> mMessages;
// The current size of mMessages.
uint32_t mCurrentSize;
// The maximum size of mMessages.
uint32_t mMaximumSize;
// Are we currently delivering a console message on the main thread? If
// so, we suppress incoming messages on the main thread only, to avoid
// infinite repitition.
bool mDeliveringMessage;
// Listeners to notify whenever a new message is logged.
ListenerHash mListeners;
// To serialize interesting methods.
mozilla::Mutex mLock;
};
#endif /* __nsconsoleservice_h__ */