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Bug
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Resolution: Done
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P1: Critical
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5.2.1
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None
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Mac OS 10.9.1 Mavericks; MacBook Pro; Qt5.2.1; llvm-g++-4.2
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macOS
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72ba4cd3858773757d3cc5a66f7859a483b6475b
On Qt5.2.1, I can't find a way to show two or more QGLWidgets in the same window without triggering a crash when they are deallocated. In my testing, the widgets operate properly while they are live, but they cause a crash when they are deallocated manually or when the program exits.
The attached test program provides the minimum necessary conditions for the crash:
#include <QApplication> #include <QWidget> #include <QHBoxLayout> #include <QGLWidget> int main(int argc, char *argv[]) { QApplication a(argc, argv); QWidget *topLevel = new QWidget; topLevel->setLayout(new QHBoxLayout); QGLWidget *firstGLWidget = new QGLWidget; topLevel->layout()->addWidget(firstGLWidget); QGLWidget *secondGLWidget = new QGLWidget; topLevel->layout()->addWidget(secondGLWidget); topLevel->resize(320,200); topLevel->show(); // delete secondGLWidget; // OK // delete firstGLWidget; // CRASH // delete topLevel; // CRASH return a.exec(); } // CRASH on exit
On my machine, this crashes about half of the time (it exits normally otherwise).
I have tried manually deleting the various widgets, and it appears that deleting firstGLWidget can be safely done and prevents the crash on exit. But deleting secondGLWidget or topLevel will crash. And if I instantiate three QGLWidgets, then I haven't found a combination of steps that would prevent a crash.
Removing the widgets from the layout using
topLevel->layout()->removeWidget(xxGLWidget);
can prevent the crash, but then I'd need to keep them around because any attempt to delete them fails.
The stack trace on exit for the above program shows that it's deallocating one of the widgets; however, the location of the crash is not consistent:
malloc: *** error for object 0x10163c740: pointer being freed was not allocated Thread 0 Crashed:: Dispatch queue: com.apple.main-thread 0 libsystem_kernel.dylib 0x00007fff895d7866 __pthread_kill + 10 1 libsystem_pthread.dylib 0x00007fff89d7235c pthread_kill + 92 2 libsystem_c.dylib 0x00007fff8964cbba abort + 125 3 libsystem_malloc.dylib 0x00007fff93211093 free + 411 4 QtCore 0x0000000100d95f45 QObject::~QObject() + 181 5 QtGui 0x00000001006f502c QWindow::~QWindow() + 140 6 QtWidgets 0x00000001000f71fb QWidgetWindow::~QWidgetWindow() + 139 7 QtWidgets 0x00000001000f711e QWidgetWindow::~QWidgetWindow() + 14 8 QtWidgets 0x00000001000f49d3 QWidgetPrivate::deleteTLSysExtra() + 83 9 QtWidgets 0x00000001000f4828 QWidget::destroy(bool, bool) + 888 10 QtWidgets 0x00000001000f47da QWidget::destroy(bool, bool) + 810 11 QtWidgets 0x000000010009e15e QApplication::~QApplication() + 270 12 com.yourcompany.glwidgettest 0x0000000100003a92 main + 562 (main.cpp:27) 13 com.yourcompany.glwidgettest 0x0000000100003854 start + 52
All of this worked fine on 5.2.0, and this test program also succeeds there. This also works fine on Qt5.2.1/Ubuntu.