Segmentation fault during QApplication.exec()

[Jibims]

Hey,

I've got a segmentation during the QApplication.exec() call, the seg fault doesn't occurs every time i launch the program bur more ling 6 times on 10. Do you know what could cause it ?

Here is a backtrace from GDB:
Thread 1 "client" received signal SIGSEGV, Segmentation fault.
0x00007ffff61fcd56 in QMetaObject::activate(QObject*, int, int, void**) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Core.so.5
(gdb) bt full
#0 0x00007ffff61fcd56 in QMetaObject::activate(QObject*, int, int, void**) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#1 0x00007ffff7669b07 in QWidgetLineControl::processKeyEvent(QKeyEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#2 0x00007ffff75d9daa in QLineEdit::keyPressEvent(QKeyEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#3 0x00007ffff74e9db4 in QWidget::event(QEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#4 0x00007ffff75df6f5 in QLineEdit::event(QEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#5 0x00007ffff74a452c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#6 0x00007ffff74ab029 in QApplication::notify(QObject*, QEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#7 0x00007ffff61d5ae0 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#8 0x00007ffff750752b in ?? () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#9 0x00007ffff74a452c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#10 0x00007ffff74ab220 in QApplication::notify(QObject*, QEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
No symbol table info available.
#11 0x00007ffff61d5ae0 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#12 0x00007ffff6775a58 in QGuiApplicationPrivate::processKeyEvent(QWindowSystemInterfacePrivate::KeyEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Gui.so.5
No symbol table info available.
#13 0x00007ffff677a725 in QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Gui.so.5
No symbol table info available.
#14 0x00007ffff675be73 in QWindowSystemInterface::sendWindowSystemEvents(QFlagsQEventLoop::ProcessEventsFlag) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Gui.so.5
No symbol table info available.
#15 0x00007fffec943080 in ?? () from /home/benjamin/Qt5.7.0/5.7/gcc_64/plugins/platforms/../../lib/libQt5XcbQpa.so.5
No symbol table info available.
#16 0x00007ffff1db4197 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#17 0x00007ffff1db43f0 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#18 0x00007ffff1db449c in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#19 0x00007ffff6223047 in QEventDispatcherGlib::processEvents(QFlagsQEventLoop::ProcessEventsFlag) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#20 0x00007ffff61d3dca in QEventLoop::exec(QFlagsQEventLoop::ProcessEventsFlag) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#21 0x00007ffff61dbbad in QCoreApplication::exec() () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Core.so.5
No symbol table info available.
#22 0x0000000000408e92 in main (argc=2, argv=0x7fffffffe3b8) at /home/benjamin/CLionProjects/Group4/code/client/ClientLauncher.cpp:37
application = <incomplete type>
app = {_vptr.App = 0x64f628 <vtable for App+16>, server_ip_address = 0x7fffffffe765 "127.0.0.1", player_id = 11, username = "b", current_manager = 0xa1f290}
app = {_vptr.App = 0x64f628 <vtable for App+16>, server_ip_address = 0x7fffffffe765 "127.0.0.1", player_id = 11, username = "b", current_manager = 0xa1f290}

[A Former User]

Hi, welcome to the forum.

signal SIGSEGV, Segmentation fault.

ClientLauncher.cpp:37

Somewhere in line 37 bad things happen. Maybe you want to show us some code? :)

[Jibims]

I can't post all the source code but line 37 is simply : return application.exec();

[Jibims]

application is a QApplication ;)

[A Former User]

Without code, no-one but you can find out.

[JKSH]

@Jibims said in Segmentation fault during QApplication.exec():

#1 0x00007ffff7669b07 in QWidgetLineControl::processKeyEvent(QKeyEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5
#2 0x00007ffff75d9daa in QLineEdit::keyPressEvent(QKeyEvent*) () from /home/benjamin/Qt5.7.0/5.7/gcc_64/lib/libQt5Widgets.so.5

I don't know what's causing the crash, but these lines look interesting. Are you pressing any keys during application startup? Does it still crash if you refrain from pressing any keys?

[Jibims]

Yep, there is no seg fault if i don't press any key

[JKSH]

@Jibims said in Segmentation fault during QApplication.exec():

Yep, there is no seg fault if i don't press any key

So back in Qt 5.4, does it crash if you press keys at startup?

[Jibims]

@JKSH Dunno, i have to use Qt 5.7 :/

[JKSH]

@Jibims said in Segmentation fault during QApplication.exec():

@JKSH Dunno, i have to use Qt 5.7 :/

Sorry, I got mixed up between your issue and someone else (they got crashes after upgrading from Qt 5.4).

Anyway,

1. Is it a particular key that causes the crash? Or does it crash no matter what key you're pressing at startup?
2. At startup, if you wait for 5 seconds before you press the key(s), does it still crash?

[SGaist]

Hi,

Even if you have to use 5.7, it's a good idea to test against an older version to help determine whether that behaviour is new to 5.7.