[ I realized I ought to supply the crash backtrace; I have appended it below my
signature. ]
Hi folks. I’m seeing something weird that I don’t understand. I have a
connection defined for the main window of my Qt Widgets app, like so:
connect(qApp, &QApplication::focusChanged, [this]() { updateUIEnabling(); });
I’m seeing a 100% reproducible crash as a result of this. When the
focusChanged signal fires, I end up in updateUIEnabling() as expected, but I
immediately crash because something about the state of things is corrupted; the
immediate symptom, according to the debugger, is that the ui pointer for my
main window is equal to 0x1 (yuck). I try to access a button,
ui->playOneStepButton, and it crashes. As I said, 100% reproducible.
The weird thing is that this does *not* happen if I change the connect
statement to this:
connect(qApp, &QApplication::focusChanged, this,
&QtSLiMWindow::updateUIEnabling);
Now, 100% of the time, there is no problem, no crash, and my app chugs along
happily. No other code changes involved. I can literally flip this connect
definition back and forth in my code and go from 100% crashing to 100% fine.
I’m pretty new to Qt and maybe I’m just being clueless somehow; but I thought
that the two definitions above would be essentially identical in their effect.
Why does the first one crash? Note that it works fine in general; it seems to
crash specifically when I open a *second* main window (which makes its own
connection to focusChanged in the same way), and then close that second main
window. Now the first main window’s connection is somehow unhappy, and the
next time I trigger the focusChanged() signal, boom. It’s as if the connection
for the second window somehow interferes with the connection for the first
window, and closing the second window leads to a corruption in the connection
state.
Naturally, I am now nervous about using the first type of connection anywhere
in my code, since I don’t understand what the issue is. Can anyone shed light
on this?
Cheers,
-B.
Benjamin C. Haller
Messer Lab
Cornell University
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 com.sticksoftware.QtSLiM 0x00000001003c84b1
QtSLiMWindow::updateUIEnabling() + 17 (QtSLiMWindow.cpp:1589)
1 com.sticksoftware.QtSLiM 0x00000001003d224e
QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void,
QtSLiMWindow::init()::$_3>::call(QtSLiMWindow::init()::$_3&, void**) + 14
(qobjectdefs_impl.h:146)
2 org.qt-project.QtCore 0x000000010228ca95 void
doActivate<false>(QObject*, int, void**) + 1157 (memory:2597)
3 org.qt-project.QtWidgets 0x00000001013d67de
QApplicationPrivate::setFocusWidget(QWidget*, Qt::FocusReason) + 510
4 org.qt-project.QtWidgets 0x000000010140f6fd
QWidget::setFocus(Qt::FocusReason) + 637 (qwidget.cpp:6356)
5 org.qt-project.QtWidgets 0x00000001013d7dd8
QApplication::setActiveWindow(QWidget*) + 1160
6 org.qt-project.QtWidgets 0x00000001013d8333
QApplicationPrivate::notifyActiveWindowChange(QWindow*) + 51
(qapplication.cpp:2101)
7 org.qt-project.QtGui 0x0000000101a35623
QGuiApplicationPrivate::processActivatedEvent(QWindowSystemInterfacePrivate::ActivatedWindowEvent*)
+ 675 (qguiapplication.cpp:2438)
8 org.qt-project.QtGui 0x0000000101a12cc3 bool
QWindowSystemInterfacePrivate::handleWindowSystemEvent<QWindowSystemInterface::SynchronousDelivery>(QWindowSystemInterfacePrivate::WindowSystemEvent*)
+ 115 (qwindowsysteminterface.cpp:106)
9 libqcocoa.dylib 0x00000001063511ee
QCocoaWindow::windowDidBecomeKey() + 238 (qcocoawindow.mm:1194)
10 org.qt-project.QtCore 0x00000001022648d6
QMetaMethod::invoke(QObject*, Qt::ConnectionType, QGenericReturnArgument,
QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument,
QGenericArgument, QGenericArgument, QGenericArgument, QGenericArgument,
QGenericArgument, QGenericArgument) const + 1270
11 libqcocoa.dylib 0x0000000106354830 invocation function
for block in qRegisterNotificationCallbacks() + 1936 (qcocoawindow.mm:131)
12 com.apple.Foundation 0x00007fff3860cfab -[__NSObserver
_doit:] + 296
13 com.apple.CoreFoundation 0x00007fff35f8c35f
__CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 12
14 com.apple.CoreFoundation 0x00007fff35f8c2f3
___CFXRegistrationPost1_block_invoke + 63
15 com.apple.CoreFoundation 0x00007fff35f8c268
_CFXRegistrationPost1 + 372
16 com.apple.CoreFoundation 0x00007fff35f8bebe
___CFXNotificationPost_block_invoke + 97
17 com.apple.CoreFoundation 0x00007fff35f5b7e2
-[_CFXNotificationRegistrar find:object:observer:enumerator:] + 1575
18 com.apple.CoreFoundation 0x00007fff35f5ac82 _CFXNotificationPost
+ 1351
19 com.apple.Foundation 0x00007fff385e0a22
-[NSNotificationCenter postNotificationName:object:userInfo:] + 59
20 com.apple.AppKit 0x00007fff3333675e -[NSWindow
becomeKeyWindow] + 1276
21 com.apple.AppKit 0x00007fff332b85ae -[NSWindow
_changeKeyAndMainLimitedOK:] + 963
22 com.apple.AppKit 0x00007fff332b80b2 -[NSWindow
_makeKeyRegardlessOfVisibility] + 76
23 com.apple.AppKit 0x00007fff332ab8d9 -[NSWindow
makeKeyAndOrderFront:] + 40
24 libqcocoa.dylib 0x000000010634d83d
QCocoaWindow::setVisible(bool) + 1597 (qcocoawindow.mm:370)
25 org.qt-project.QtGui 0x0000000101a3d138
QWindowPrivate::setVisible(bool) + 1112 (qwindow.cpp:410)
26 org.qt-project.QtWidgets 0x00000001014115f7
QWidgetPrivate::show_sys() + 903 (qwidget.cpp:7910)
27 org.qt-project.QtWidgets 0x00000001014129e5
QWidgetPrivate::show_helper() + 405 (qwidget.cpp:7833)
28 org.qt-project.QtWidgets 0x0000000101413626
QWidgetPrivate::setVisible(bool) + 806 (qwidget.cpp:8129)
29 com.sticksoftware.QtSLiM 0x0000000100426d55
QtSLiMEidosConsole::setVariableBrowserVisibility(bool) + 149
(QtSLiMEidosConsole.cpp:221)
30 com.sticksoftware.QtSLiM 0x00000001003d1170
QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, void
(QtSLiMAppDelegate::*)()>::call(void (QtSLiMAppDelegate::*)(),
QtSLiMAppDelegate*, void**) + 32 (qobjectdefs_impl.h:152)
31 org.qt-project.QtCore 0x000000010228ca95 void
doActivate<false>(QObject*, int, void**) + 1157 (memory:2597)
32 org.qt-project.QtWidgets 0x00000001014c271f
QAbstractButtonPrivate::emitClicked() + 111 (qsharedpointer_impl.h:701)
33 org.qt-project.QtWidgets 0x00000001014c25b9
QAbstractButtonPrivate::click() + 233 (qabstractbutton.cpp:409)
34 org.qt-project.QtWidgets 0x00000001014c36ef
QAbstractButton::mouseReleaseEvent(QMouseEvent*) + 271
(qabstractbutton.cpp:1013)
35 org.qt-project.QtWidgets 0x000000010141399d
QWidget::event(QEvent*) + 445 (qwidget.cpp:8659)
36 org.qt-project.QtWidgets 0x00000001013d8f5a
QApplicationPrivate::notify_helper(QObject*, QEvent*) + 266
(qapplication.cpp:3687)
37 org.qt-project.QtWidgets 0x00000001013dbe32
QApplication::notify(QObject*, QEvent*) + 7330 (qapplication.cpp:3129)
38 org.qt-project.QtCore 0x00000001022599f4
QCoreApplication::notifyInternal2(QObject*, QEvent*) + 212
(qcoreapplication.cpp:1075)
39 org.qt-project.QtWidgets 0x00000001013d9880
QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*,
QWidget**, QPointer<QWidget>&, bool, bool) + 896
40 org.qt-project.QtWidgets 0x0000000101432908
QWidgetWindow::handleMouseEvent(QMouseEvent*) + 1704 (qwidgetwindow.cpp:673)
41 org.qt-project.QtWidgets 0x00000001014315f5
QWidgetWindow::event(QEvent*) + 229 (qwidgetwindow.cpp:295)
42 org.qt-project.QtWidgets 0x00000001013d8f5a
QApplicationPrivate::notify_helper(QObject*, QEvent*) + 266
(qapplication.cpp:3687)
43 org.qt-project.QtWidgets 0x00000001013da3e6
QApplication::notify(QObject*, QEvent*) + 598
44 org.qt-project.QtCore 0x00000001022599f4
QCoreApplication::notifyInternal2(QObject*, QEvent*) + 212
(qcoreapplication.cpp:1075)
45 org.qt-project.QtGui 0x0000000101a32895
QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent*)
+ 3397 (qguiapplication.cpp:2204)
46 org.qt-project.QtGui 0x0000000101a1815b
QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>)
+ 219 (qwindowsysteminterface.cpp:1176)
47 libqcocoa.dylib 0x00000001063690f0
QCocoaEventDispatcherPrivate::processPostedEvents() + 320
(qcocoaeventdispatcher.mm:890)
48 libqcocoa.dylib 0x0000000106369858
QCocoaEventDispatcherPrivate::postedEventsSourceCallback(void*) + 40
49 com.apple.CoreFoundation 0x00007fff35f96b21
__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
50 com.apple.CoreFoundation 0x00007fff35f96ac0 __CFRunLoopDoSource0
+ 103
51 com.apple.CoreFoundation 0x00007fff35f968d4
__CFRunLoopDoSources0 + 209
52 com.apple.CoreFoundation 0x00007fff35f95740 __CFRunLoopRun + 1272
53 com.apple.CoreFoundation 0x00007fff35f94bd3 CFRunLoopRunSpecific
+ 499
54 com.apple.HIToolbox 0x00007fff34aea65d
RunCurrentEventLoopInMode + 292
55 com.apple.HIToolbox 0x00007fff34aea2a9
ReceiveNextEventCommon + 356
56 com.apple.HIToolbox 0x00007fff34aea127
_BlockUntilNextEventMatchingListInModeWithFilter + 64
57 com.apple.AppKit 0x00007fff3315aba4 _DPSNextEvent + 990
58 com.apple.AppKit 0x00007fff33159380
-[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:]
+ 1352
59 com.apple.AppKit 0x00007fff3314b09e -[NSApplication run]
+ 658
60 libqcocoa.dylib 0x00000001063685d3
QCocoaEventDispatcher::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) +
2579 (qcocoaeventdispatcher.mm:430)
61 org.qt-project.QtCore 0x0000000102255a7f
QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) + 431 (atomic:929)
62 org.qt-project.QtCore 0x000000010225a002
QCoreApplication::exec() + 130 (qcoreapplication.cpp:1383)
63 com.sticksoftware.QtSLiM 0x00000001003ba56e main + 670
64 libdyld.dylib 0x00007fff6d4a17fd start + 1
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