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QProgressDialog::setValue导致随机堆栈溢出。

c++windowsqtubuntustack-overflow
4

我正在开发一个不能分享源代码的重大项目。在该项目中，我们在Windows操作系统中（而不是Ubuntu）遇到了一些无法很好地重现的栈溢出错误，并且调试器的堆栈跟踪显示进度对话框设置为窗口模态时，递归调用了QProgressDialog :: setValue(int)。

我创建了这个小的示例来尝试重现错误。虽然我在使用此示例时（在Windows或Ubuntu上）没有遇到过栈溢出错误，但是当我通过在调试器中添加断点并查看QProgressDialog :: setValue时， 我看到它也递归地调用自己（在两个操作系统中），只是没有足够的次数产生堆栈溢出。最令人印象深刻的是，有时它确实只调用了一次QPrigressDialog :: setValue。

请参见Windows的调用堆栈示例：

Qt5Widgets.dll!QProgressDialog::setValue(int progress) Line 653 C++
[Inline Frame] Qt5Core.dll!QtPrivate::QSlotObjectBase::call(QObject *) Line 398 C++
Qt5Core.dll!QMetaCallEvent::placeMetaCall(QObject * object) Line 626    C++
Qt5Core.dll!QObject::event(QEvent * e) Line 1339    C++
Qt5Widgets.dll!QWidget::event(QEvent * event) Line 9094 C++
Qt5Widgets.dll!QApplicationPrivate::notify_helper(QObject * receiver, QEvent * e) Line 3687 C++
Qt5Widgets.dll!QApplication::notify(QObject * receiver, QEvent * e) Line 3639   C++
Qt5Core.dll!QCoreApplication::notifyInternal2(QObject * receiver, QEvent * event) Line 1075 C++
[Inline Frame] Qt5Core.dll!QCoreApplication::sendEvent(QObject *) Line 1470 C++
Qt5Core.dll!QCoreApplicationPrivate::sendPostedEvents(QObject * receiver, int event_type, QThreadData * data) Line 1815 C++
qwindows.dll!QWindowsGuiEventDispatcher::sendPostedEvents() Line 82 C++
Qt5Core.dll!QEventDispatcherWin32::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 525 C++
qwindows.dll!QWindowsGuiEventDispatcher::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 75    C++
Qt5Widgets.dll!QProgressDialog::setValue(int progress) Line 663 C++
[Inline Frame] Qt5Core.dll!QtPrivate::QSlotObjectBase::call(QObject *) Line 398 C++
Qt5Core.dll!QMetaCallEvent::placeMetaCall(QObject * object) Line 626    C++
Qt5Core.dll!QObject::event(QEvent * e) Line 1339    C++
Qt5Widgets.dll!QWidget::event(QEvent * event) Line 9094 C++
Qt5Widgets.dll!QApplicationPrivate::notify_helper(QObject * receiver, QEvent * e) Line 3687 C++
Qt5Widgets.dll!QApplication::notify(QObject * receiver, QEvent * e) Line 3639   C++
Qt5Core.dll!QCoreApplication::notifyInternal2(QObject * receiver, QEvent * event) Line 1075 C++
[Inline Frame] Qt5Core.dll!QCoreApplication::sendEvent(QObject *) Line 1470 C++
Qt5Core.dll!QCoreApplicationPrivate::sendPostedEvents(QObject * receiver, int event_type, QThreadData * data) Line 1815 C++
qwindows.dll!QWindowsGuiEventDispatcher::sendPostedEvents() Line 82 C++
Qt5Core.dll!QEventDispatcherWin32::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 525 C++
qwindows.dll!QWindowsGuiEventDispatcher::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 75    C++
Qt5Widgets.dll!QProgressDialog::setValue(int progress) Line 663 C++
[Inline Frame] Qt5Core.dll!QtPrivate::QSlotObjectBase::call(QObject *) Line 398 C++
Qt5Core.dll!QMetaCallEvent::placeMetaCall(QObject * object) Line 626    C++
Qt5Core.dll!QObject::event(QEvent * e) Line 1339    C++
Qt5Widgets.dll!QWidget::event(QEvent * event) Line 9094 C++
Qt5Widgets.dll!QApplicationPrivate::notify_helper(QObject * receiver, QEvent * e) Line 3687 C++
Qt5Widgets.dll!QApplication::notify(QObject * receiver, QEvent * e) Line 3639   C++
Qt5Core.dll!QCoreApplication::notifyInternal2(QObject * receiver, QEvent * event) Line 1075 C++
[Inline Frame] Qt5Core.dll!QCoreApplication::sendEvent(QObject *) Line 1470 C++
Qt5Core.dll!QCoreApplicationPrivate::sendPostedEvents(QObject * receiver, int event_type, QThreadData * data) Line 1815 C++
qwindows.dll!QWindowsGuiEventDispatcher::sendPostedEvents() Line 82 C++
Qt5Core.dll!QEventDispatcherWin32::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 525 C++
qwindows.dll!QWindowsGuiEventDispatcher::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 75    C++
Qt5Widgets.dll!QProgressDialog::setValue(int progress) Line 663 C++
[Inline Frame] Qt5Core.dll!QtPrivate::QSlotObjectBase::call(QObject *) Line 398 C++
Qt5Core.dll!QMetaCallEvent::placeMetaCall(QObject * object) Line 626    C++
Qt5Core.dll!QObject::event(QEvent * e) Line 1339    C++
Qt5Widgets.dll!QWidget::event(QEvent * event) Line 9094 C++
Qt5Widgets.dll!QApplicationPrivate::notify_helper(QObject * receiver, QEvent * e) Line 3687 C++
Qt5Widgets.dll!QApplication::notify(QObject * receiver, QEvent * e) Line 3639   C++
Qt5Core.dll!QCoreApplication::notifyInternal2(QObject * receiver, QEvent * event) Line 1075 C++
[Inline Frame] Qt5Core.dll!QCoreApplication::sendEvent(QObject *) Line 1470 C++
Qt5Core.dll!QCoreApplicationPrivate::sendPostedEvents(QObject * receiver, int event_type, QThreadData * data) Line 1815 C++
qwindows.dll!QWindowsGuiEventDispatcher::sendPostedEvents() Line 82 C++
Qt5Core.dll!QEventDispatcherWin32::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 525 C++
qwindows.dll!QWindowsGuiEventDispatcher::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 75    C++
Qt5Widgets.dll!QProgressDialog::setValue(int progress) Line 663 C++
[Inline Frame] Qt5Core.dll!QtPrivate::QSlotObjectBase::call(QObject *) Line 398 C++
Qt5Core.dll!QMetaCallEvent::placeMetaCall(QObject * object) Line 626    C++
Qt5Core.dll!QObject::event(QEvent * e) Line 1339    C++
Qt5Widgets.dll!QWidget::event(QEvent * event) Line 9094 C++
Qt5Widgets.dll!QApplicationPrivate::notify_helper(QObject * receiver, QEvent * e) Line 3687 C++
Qt5Widgets.dll!QApplication::notify(QObject * receiver, QEvent * e) Line 3639   C++
Qt5Core.dll!QCoreApplication::notifyInternal2(QObject * receiver, QEvent * event) Line 1075 C++
[Inline Frame] Qt5Core.dll!QCoreApplication::sendEvent(QObject *) Line 1470 C++
Qt5Core.dll!QCoreApplicationPrivate::sendPostedEvents(QObject * receiver, int event_type, QThreadData * data) Line 1815 C++
qwindows.dll!QWindowsGuiEventDispatcher::sendPostedEvents() Line 82 C++
Qt5Core.dll!QEventDispatcherWin32::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 525 C++
qwindows.dll!QWindowsGuiEventDispatcher::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 75    C++
Qt5Widgets.dll!QProgressDialog::setValue(int progress) Line 663 C++
[Inline Frame] Qt5Core.dll!QtPrivate::QSlotObjectBase::call(QObject *) Line 398 C++
Qt5Core.dll!QMetaCallEvent::placeMetaCall(QObject * object) Line 626    C++
Qt5Core.dll!QObject::event(QEvent * e) Line 1339    C++
Qt5Widgets.dll!QWidget::event(QEvent * event) Line 9094 C++
Qt5Widgets.dll!QApplicationPrivate::notify_helper(QObject * receiver, QEvent * e) Line 3687 C++
Qt5Widgets.dll!QApplication::notify(QObject * receiver, QEvent * e) Line 3639   C++
Qt5Core.dll!QCoreApplication::notifyInternal2(QObject * receiver, QEvent * event) Line 1075 C++
[Inline Frame] Qt5Core.dll!QCoreApplication::sendEvent(QObject *) Line 1470 C++
Qt5Core.dll!QCoreApplicationPrivate::sendPostedEvents(QObject * receiver, int event_type, QThreadData * data) Line 1815 C++
qwindows.dll!QWindowsGuiEventDispatcher::sendPostedEvents() Line 82 C++
Qt5Core.dll!QEventDispatcherWin32::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 525 C++
qwindows.dll!QWindowsGuiEventDispatcher::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 75    C++
Qt5Widgets.dll!QProgressDialog::setValue(int progress) Line 663 C++
[Inline Frame] Qt5Core.dll!QtPrivate::QSlotObjectBase::call(QObject *) Line 398 C++
Qt5Core.dll!QMetaCallEvent::placeMetaCall(QObject * object) Line 626    C++
Qt5Core.dll!QObject::event(QEvent * e) Line 1339    C++
Qt5Widgets.dll!QWidget::event(QEvent * event) Line 9094 C++
Qt5Widgets.dll!QApplicationPrivate::notify_helper(QObject * receiver, QEvent * e) Line 3687 C++
Qt5Widgets.dll!QApplication::notify(QObject * receiver, QEvent * e) Line 3639   C++
Qt5Core.dll!QCoreApplication::notifyInternal2(QObject * receiver, QEvent * event) Line 1075 C++
[Inline Frame] Qt5Core.dll!QCoreApplication::sendEvent(QObject *) Line 1470 C++
Qt5Core.dll!QCoreApplicationPrivate::sendPostedEvents(QObject * receiver, int event_type, QThreadData * data) Line 1815 C++
qwindows.dll!QWindowsGuiEventDispatcher::sendPostedEvents() Line 82 C++
Qt5Core.dll!QEventDispatcherWin32::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 525 C++
qwindows.dll!QWindowsGuiEventDispatcher::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 75    C++
[Inline Frame] Qt5Core.dll!QEventLoop::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag>) Line 138   C++
Qt5Core.dll!QEventLoop::exec(QFlags<enum QEventLoop::ProcessEventsFlag> flags) Line 225 C++
Qt5Core.dll!QCoreApplication::exec() Line 1383  C++
progress_bar.exe!main(int argc, char * * argv) Line 9   C++
[External Code]

看一个在Ubuntu上的调用栈示例：

#0  0x00007ffff76fa330 in QProgressDialog::setValue(int) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#1  0x00007ffff60a3dec in QtPrivate::FunctorCall<QtPrivate::IndexesList<0>, QtPrivate::List<int>, void, void (QProgressDialog::*)(int)>::call(void (QProgressDialog::*)(int), QProgressDialog*, void**) ()
    at /home/apalomer/programming_workspace/progress_bar_example/build/libthreadedworker.so
#2  0x00007ffff60a3ba4 in void QtPrivate::FunctionPointer<void (QProgressDialog::*)(int)>::call<QtPrivate::List<int>, void>(void (QProgressDialog::*)(int), QProgressDialog*, void**) ()
    at /home/apalomer/programming_workspace/progress_bar_example/build/libthreadedworker.so
#3  0x00007ffff60a3759 in QtPrivate::QSlotObject<void (QProgressDialog::*)(int), QtPrivate::List<int>, void>::impl(int, QtPrivate::QSlotObjectBase*, QObject*, void**, bool*) ()
    at /home/apalomer/programming_workspace/progress_bar_example/build/libthreadedworker.so
#4  0x00007ffff6ef30c2 in QObject::event(QEvent*) (this=0x555555b74610, e=<optimized out>) at kernel/qobject.cpp:1247
#5  0x00007ffff751775b in QWidget::event(QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#6  0x00007ffff74d883c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#7  0x00007ffff74e0104 in QApplication::notify(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#8  0x00007ffff6ec38d8 in QCoreApplication::notifyInternal2(QObject*, QEvent*) (receiver=0x555555b74610, event=event@entry=0x7fffc80037a0) at kernel/qcoreapplication.cpp:1024
#9  0x00007ffff6ec604d in QCoreApplication::sendEvent(QObject*, QEvent*) (event=0x7fffc80037a0, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:233
#10 0x00007ffff6ec604d in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) (receiver=receiver@entry=0x0, event_type=event_type@entry=0, data=0x55555576fef0)
    at kernel/qcoreapplication.cpp:1699
#11 0x00007ffff6ec65d8 in QCoreApplication::sendPostedEvents(QObject*, int) (receiver=receiver@entry=0x0, event_type=event_type@entry=0) at kernel/qcoreapplication.cpp:1553
#12 0x00007ffff6f1d263 in postEventSourceDispatch(GSource*, GSourceFunc, gpointer) (s=0x5555558952a0) at kernel/qeventdispatcher_glib.cpp:276
#13 0x00007ffff4221417 in g_main_context_dispatch () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#14 0x00007ffff4221650 in  () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#15 0x00007ffff42216dc in g_main_context_iteration () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#16 0x00007ffff6f1c88f in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x5555558d2b80, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#17 0x00007ffff76fa4c7 in QProgressDialog::setValue(int) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#18 0x00007ffff60a3dec in QtPrivate::FunctorCall<QtPrivate::IndexesList<0>, QtPrivate::List<int>, void, void (QProgressDialog::*)(int)>::call(void (QProgressDialog::*)(int), QProgressDialog*, void**) ()
    at /home/apalomer/programming_workspace/progress_bar_example/build/libthreadedworker.so
#19 0x00007ffff60a3ba4 in void QtPrivate::FunctionPointer<void (QProgressDialog::*)(int)>::call<QtPrivate::List<int>, void>(void (QProgressDialog::*)(int), QProgressDialog*, void**) ()
    at /home/apalomer/programming_workspace/progress_bar_example/build/libthreadedworker.so
#20 0x00007ffff60a3759 in QtPrivate::QSlotObject<void (QProgressDialog::*)(int), QtPrivate::List<int>, void>::impl(int, QtPrivate::QSlotObjectBase*, QObject*, void**, bool*) ()
    at /home/apalomer/programming_workspace/progress_bar_example/build/libthreadedworker.so
#21 0x00007ffff6ef30c2 in QObject::event(QEvent*) (this=0x555555b74610, e=<optimized out>) at kernel/qobject.cpp:1247
#22 0x00007ffff751775b in QWidget::event(QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#23 0x00007ffff74d883c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#24 0x00007ffff74e0104 in QApplication::notify(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#25 0x00007ffff6ec38d8 in QCoreApplication::notifyInternal2(QObject*, QEvent*) (receiver=0x555555b74610, event=event@entry=0x7fffc8002ef0) at kernel/qcoreapplication.cpp:1024
#26 0x00007ffff6ec604d in QCoreApplication::sendEvent(QObject*, QEvent*) (event=0x7fffc8002ef0, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:233
#27 0x00007ffff6ec604d in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) (receiver=receiver@entry=0x0, event_type=event_type@entry=0, data=0x55555576fef0)
    at kernel/qcoreapplication.cpp:1699
#28 0x00007ffff6ec65d8 in QCoreApplication::sendPostedEvents(QObject*, int) (receiver=receiver@entry=0x0, event_type=event_type@entry=0) at kernel/qcoreapplication.cpp:1553
#29 0x00007ffff6f1d263 in postEventSourceDispatch(GSource*, GSourceFunc, gpointer) (s=0x5555558952a0) at kernel/qeventdispatcher_glib.cpp:276
#30 0x00007ffff4221417 in g_main_context_dispatch () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#31 0x00007ffff4221650 in  () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#32 0x00007ffff42216dc in g_main_context_iteration () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#33 0x00007ffff6f1c88f in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x5555558d2b80, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#34 0x00007ffff6ec190a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7fffffffcfb0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:212
#35 0x00007ffff6eca9b4 in QCoreApplication::exec() () at kernel/qcoreapplication.cpp:1297
#36 0x0000555555554cb4 in main ()

有没有任何想法可以修复这个递归问题？我应该将其移动到错误报告中吗？如果我手动逐步执行程序，它会经常发生。
我已在Windows 10、Visual Studio 16.5.2、MSVC 19.25.28612.0和Qt 5.14.2以及Qt 5.14.1、Qt 5.9.5中进行了测试。此外，我还尝试在Ubuntu 18.04、g++ 7.5.0和Qt 5.9.5中进行了尝试。
为什么有人要求关闭这个问题？我已经提供了一个示例和一种重现不良行为的方法。 - apalomer
从关闭原因以及您问题的文本来看，我认为可能是因为您提供了示例的链接而不是示例本身。 - scopchanov
1个回答
1
据我从您的示例代码中了解到：
  1. 有一个工作线程每200毫秒向主事件队列发布事件。（由于从工作线程发出的信号是在排队连接上，这将在接收器的线程事件循环中发布一个事件）
  2. QProgressDialog源代码清楚地显示，当以模态模式配置时，在其setValue方法中调用QCoreApplication::processEvents。
因此，为了引起堆栈溢出，一个线程应该能够在对话框开始处理它们之前在线程事件循环中发布足够的事件。
一旦它开始处理这些事件链，它将递归自身并可能导致堆栈溢出。如果您正在使用调试器步进主线程，则可以解释为什么其他线程能够在主事件循环中累积如此多的事件。
我不知道这是否可以被视为Qt项目的错误，但您仍然可以在他们的IRC频道上询问或打开问题，看看会发生什么。
尽管如此，一个可能的特定解决方案是避免从工作线程爆发信号，以避免陷入这个陷阱（例如触发每秒钟而不是短暂的不可察觉的间隔的状态更新，供最终用户使用）。
你说得完全正确。我已经能够在我发布的项目的修改版中持续地出现这个问题。我还向Qt 报告了这个问题，以查看他们是否真正将其视为一个问题。 - apalomer
1
@apalomer，我认为你可能需要更好地解释一下在QTBUG中发生这种情况的环境。Thiago已经关闭了它，因为他认为你正在直接从另一个线程更新QProgressDialog（而不是通过排队信号）。 - epsilon
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