c++ - 加载特定网站时 QtWebKit 2.2 段错误

Question

在过去的几个月里，我一直在组装我自己的基于 QtWebKit 的浏览器( WildFox ，BSD 许可)，这是一次非常愉快的体验。然而，我注意到奇怪的崩溃，基本上是从一开始就发生的。昨天，当它无法重复加载我的个人网站 www.mayaposch.com 时，我决定深入研究这些崩溃。

事件顺序如下:我使用load()或setUrl()告诉QWebView元素加载http://www.mayaposch.com， loadFinished() 返回 false，表示在加载页面期间出现错误，然后是应用程序段错误。

我正在使用 Qt 4.8(最新的 SDK)，发布和调试库(动态)。

使用 gdb 运行调试构建时的堆栈跟踪:

0   WTF::HashTable<WTF::RefPtr<WebCore::ResourceLoader>, std::pair<WTF::RefPtr<WebCore::ResourceLoader>, WTF::RefPtr<WebCore::SubstituteResource> >, WTF::PairFirstExtractor<std::pair<WTF::RefPtr<WebCore::ResourceLoader>, WTF::RefPtr<WebCore::SubstituteResource> > >, WTF::PtrHash<WTF::RefPtr<WebCore::ResourceLoader> >, WTF::PairHashTraits<WTF::HashTraits<WTF::RefPtr<WebCore::ResourceLoader> >, WTF::HashTraits<WTF::RefPtr<WebCore::SubstituteResource> > >, WTF::HashTraits<WTF::RefPtr<WebCore::ResourceLoader> > >::isEmpty() const D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xbcd036e   
1   WTF::HashMap<WTF::RefPtr<WebCore::ResourceLoader>, WTF::RefPtr<WebCore::SubstituteResource>, WTF::PtrHash<WTF::RefPtr<WebCore::ResourceLoader> >, WTF::HashTraits<WTF::RefPtr<WebCore::ResourceLoader> >, WTF::HashTraits<WTF::RefPtr<WebCore::SubstituteResource> > >::isEmpty() const D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xbcc7315   
2   WebCore::DocumentLoader::cancelPendingSubstituteLoad(WebCore::ResourceLoader*)  D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb3cbb96   
3   WebCore::ResourceLoader::didCancel(WebCore::ResourceError const&)   D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb62277f   
4   WebCore::SubresourceLoader::didCancel(WebCore::ResourceError const&)    D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb75859c   
5   WebCore::ResourceLoader::cancel(WebCore::ResourceError const&)  D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb622900   
6   WebCore::ResourceLoader::cancel()   D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb62285a   
7   WebCore::cancelAll(WTF::HashSet<WTF::RefPtr<WebCore::ResourceLoader>, WTF::PtrHash<WTF::RefPtr<WebCore::ResourceLoader> >, WTF::HashTraits<WTF::RefPtr<WebCore::ResourceLoader> > > const&) D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb3c8725   
8   WebCore::DocumentLoader::stopLoadingSubresources()  D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb3cbfa4   
9   WebCore::DocumentLoader::stopLoading()  D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb3ca9e0   
10  WebCore::FrameLoader::stopAllLoaders(WebCore::ClearProvisionalItemPolicy)   D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb2f3694   
11  WebCore::FrameLoader::continueLoadAfterNavigationPolicy(WebCore::ResourceRequest const&, WTF::PassRefPtr<WebCore::FormState>, bool) D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb2f7d29   
12  WebCore::FrameLoader::callContinueLoadAfterNavigationPolicy(void*, WebCore::ResourceRequest const&, WTF::PassRefPtr<WebCore::FormState>, bool)  D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb2f76a1   
13  WebCore::PolicyCallback::call(bool) D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb56e06c   
14  WebCore::PolicyChecker::continueAfterNavigationPolicy(WebCore::PolicyAction)    D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb56ed26   
15  WebCore::FrameLoaderClientQt::callPolicyFunction(void (WebCore::PolicyChecker::*)(WebCore::PolicyAction), WebCore::PolicyAction)    D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb141188   
16  WebCore::FrameLoaderClientQt::dispatchDecidePolicyForNavigationAction(void (WebCore::PolicyChecker::*)(WebCore::PolicyAction), WebCore::NavigationAction const&, WebCore::ResourceRequest const&, WTF::PassRefPtr<WebCore::FormState>)  D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb146959   
17  WebCore::PolicyChecker::checkNavigationPolicy(WebCore::ResourceRequest const&, WebCore::DocumentLoader*, WTF::PassRefPtr<WebCore::FormState>, void (*)(void*, WebCore::ResourceRequest const&, WTF::PassRefPtr<WebCore::FormState>, bool), void*)   D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb56e7ef   
18  WebCore::FrameLoader::loadWithDocumentLoader(WebCore::DocumentLoader*, WebCore::FrameLoadType, WTF::PassRefPtr<WebCore::FormState>) D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb2f25e9   
19  WebCore::FrameLoader::loadWithNavigationAction(WebCore::ResourceRequest const&, WebCore::NavigationAction const&, bool, WebCore::FrameLoadType, WTF::PassRefPtr<WebCore::FormState>)    D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb2f1fc5   
20  WebCore::FrameLoader::loadURL(WebCore::KURL const&, WTF::String const&, WTF::String const&, bool, WebCore::FrameLoadType, WTF::PassRefPtr<WebCore::Event>, WTF::PassRefPtr<WebCore::FormState>) D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb2f17f1   
21  WebCore::FrameLoader::loadFrameRequest(WebCore::FrameLoadRequest const&, bool, bool, WTF::PassRefPtr<WebCore::Event>, WTF::PassRefPtr<WebCore::FormState>, WebCore::ReferrerPolicy) D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb2f1086   
22  WebCore::FrameLoader::urlSelected(WebCore::FrameLoadRequest const&, WTF::PassRefPtr<WebCore::Event>, bool, bool, WebCore::ReferrerPolicy, WebCore::ShouldReplaceDocumentIfJavaScriptURL)    D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb2ece3e   
23  WebCore::FrameLoader::changeLocation(WTF::PassRefPtr<WebCore::SecurityOrigin>, WebCore::KURL const&, WTF::String const&, bool, bool, bool)  D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb2ec9de   
24  WebCore::ScheduledURLNavigation::fire(WebCore::Frame*)  D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xbc30de8   
25  WebCore::NavigationScheduler::timerFired(WebCore::Timer<WebCore::NavigationScheduler>*) D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb3cd565   
26  WebCore::Timer<WebCore::NavigationScheduler>::fired()   D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xbc7adb2   
27  WebCore::ThreadTimers::sharedTimerFiredInternal()   D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb4a84e6   
28  WebCore::ThreadTimers::sharedTimerFired()   D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb4a8433   
29  WebCore::SharedTimerQt::timerEvent(QTimerEvent*)    D:\Dev\Qt\SDK\Desktop\Qt\4.8.0\mingw\bin\QtWebKitd4.dll 0   0xb686a5a   
30  QObject::event  qobject.cpp 1157    0x6a22499a  
31  QApplicationPrivate::notify_helper  qapplication.cpp    4550    0xa4c020    
32  QApplication::notify    qapplication.cpp    3932    0xa49973    
33  QCoreApplication::notifyInternal    qcoreapplication.cpp    876 0x6a213252  
34  QCoreApplication::sendEvent qcoreapplication.h  231 0x6a283f54  
35  QEventDispatcherWin32::event    qeventdispatcher_win.cpp    1135    0x6a23ac60  
36  QApplicationPrivate::notify_helper  qapplication.cpp    4550    0xa4c020    
37  QApplication::notify    qapplication.cpp    3932    0xa49973    
38  QCoreApplication::notifyInternal    qcoreapplication.cpp    876 0x6a213252  
39  QCoreApplication::sendEvent qcoreapplication.h  231 0x6a283f54  
40  QCoreApplicationPrivate::sendPostedEvents   qcoreapplication.cpp    1500    0x6a21416d  
41  qt_internal_proc    qeventdispatcher_win.cpp    496 0x6a238a2f  
42  USER32!IsDialogMessageW C:\Windows\syswow64\user32.dll  0   0x75a46238  
43  operator+       0   0x7113ae    
44  USER32!AllowForegroundActivation    C:\Windows\syswow64\user32.dll  0   0x75a468ea  
45  qt_fast_timer_proc  qeventdispatcher_win.cpp    428 0x6a2387c8  
46  USER32!GetMessageExtraInfo  C:\Windows\syswow64\user32.dll  0   0x75a47d31  
47  ??      0

故障线(拆机)表示为:

0xbcd036e  <+0x0006>         mov    0xc(%eax),%eax

这是内部 QtWebKit 错误吗？从堆栈跟踪我会说它是，但我缺乏它的内部知识来说明出了什么问题。崩溃最常发生在我的个人网站上，但其他人报告说它在其他网站上也会崩溃，包括中断加载时(例如，在加载完成之前单击链接)。

感谢您提供的任何帮助。

Answer 1

在与 Net147 (Jonathan Liu) 在#Qt @Freenode IRC 上进行讨论后，确定这确实是由于 webkit 中的一个错误:https://bugs.webkit.org/show_bug.cgi?id=83565

The crash is caused by a null pointer dereference in Source/WebCore/loader/ResourceLoader.cpp in the function ResourceLoader::didCancel(). m_documentLoader->cancelPendingSubstituteLoad(this) is called without checking if m_documentLoader is null.

我觉得最有趣的是我的代码触发了这个错误，而 Qt 浏览器演示却没有。任何愿意弄清楚为什么会这样的人都非常欢迎:)