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Type: Bug
Resolution: Done
Priority: P2: Important
Fix Version/s: 5.15.8, 6.2.3, 6.3.0 Alpha
Affects Version/s: 5.12.11, 5.15.7
Component/s: GUI: Basic Input System (keyboard, mouse, touch), GUI: OpenGL
Labels:
- reported_by_support_standard

Platform/s:

Linux/Other display system
Commits:
875b8174eb6febf9a4c7d129b3152160ac301fbb (qt/qtbase/6.2) 30b0b72453239666952ab516c618c19f0ca0aca6 (qt/qtbase/dev) 0c5efb68dc8f976978a694be7ae8d1d66b9a86e6 (qt/tqtc-qtbase/5.15)

Description

Hi all,
On embedded system using Linux, GCC, touchscreen, eglfs we get sometimes following stacktrace at app closing:

2020-01-01 03:43:51.177|690|FATAL|void stackTraceSignalHandler(int)|StackTrace.cpp:35|Received signal 11: Segmentation fault
#0 (SP=0x00007fe0afffdd30 (IP=0x0000000001baefe6):stackTraceSignalHandler(int)+0x158
#1 (SP=0x00007fe0afffddc0 (IP=0x00007fe0b84ceee0):killpg+0x40
#2 (SP=0x00007fe0afffe450 (IP=0x00007fe0b92b0514):QScreen::geometry() const+0x14
#3 (SP=0x00007fe0afffe470 (IP=0x00007fe0b5d76698):QEvdevTouchScreenData::screenGeometry() const+0x1e8
#4 (SP=0x00007fe0afffe4f0 (IP=0x00007fe0b5d78ac6):QEvdevTouchScreenData::reportPoints()+0x26
#5 (SP=0x00007fe0afffe580 (IP=0x00007fe0b5d7becc):QEvdevTouchScreenData::processInputEvent(input_event*)+0x77c
#6 (SP=0x00007fe0afffe600 (IP=0x00007fe0b5d7dd30):QEvdevTouchScreenHandler::readData()+0xd0
#7 (SP=0x00007fe0afffe980 (IP=0x00007fe0b8df2c0f):QMetaObject::activate(QObject*, int, int, void**)+0x81f
#8 (SP=0x00007fe0afffea80 (IP=0x00007fe0b8e013cf):QSocketNotifier::activated(int, QSocketNotifier::QPrivateSignal)+0x4f
#9 (SP=0x00007fe0afffeac0 (IP=0x00007fe0b8e01871):QSocketNotifier::event(QEvent*)+0xf1
#a (SP=0x00007fe0afffeb00 (IP=0x00007fe0b8dbf4fb):QCoreApplication::notifyInternal2(QObject*, QEvent*)+0x19b
#b (SP=0x00007fe0afffeb60 (IP=0x00007fe0b8e263a5):socketNotifierSourceDispatch(_GSource*, int (*)(void*), void*)+0x75
#c (SP=0x00007fe0afffeba0 (IP=0x00007fe0b7ee205d):g_main_context_dispatch+0x28d
#d (SP=0x00007fe0afffec20 (IP=0x00007fe0b7ee2300):g_main_context_dispatch+0x530
#e (SP=0x00007fe0afffec80 (IP=0x00007fe0b7ee23bf):g_main_context_iteration+0x3f
#f (SP=0x00007fe0afffecb0 (IP=0x00007fe0b8e25081):QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>)+0x71
#10 (SP=0x00007fe0afffed10 (IP=0x00007fe0b8dbd5c3):QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>)+0xf3
#11 (SP=0x00007fe0afffed90 (IP=0x00007fe0b8bb6b3b):QThread::exec()+0x6b
#12 (SP=0x00007fe0afffede0 (IP=0x00007fe0b5d78994):QEvdevTouchScreenHandlerThread::run()+0xa4
#13 (SP=0x00007fe0afffee40 (IP=0x00007fe0b8bb81e3):QThreadPrivate::start(void*)+0x153
#14 (SP=0x00007fe0afffee90 (IP=0x00007fe0b89eef96):start_thread+0xd6
#15 (SP=0x00007fe0afffef40 (IP=0x00007fe0b858b82f):clone+0x3f
<end of stack>

The reason is obviously that in the QEvdevTouchScreenData::screenGeometry() there are no checking of (screen == nullptr) before this one:

return QHighDpi::toNativePixels(screen->geometry(), screen);

But after I inserted the:

if(screen == 0)
 return QRect{};

it works fine without crashing. It looks like at application closing the Screens removed before the touchscreen activities stopped and function access to nullptr

Best Regards,

Sergey

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For Gerrit Dashboard: QTBUG-95192
#	Subject	Branch	Project	Status	CR	V
385046,2	Test for nullptr before dereferencing the screen	dev	qt/qtbase	Status: MERGED	+2	0
385157,2	Test for nullptr before dereferencing the screen	6.2	qt/qtbase	Status: MERGED	+2	0
385158,3	Test for nullptr before dereferencing the screen	tqtc/lts-5.15	qt/tqtc-qtbase	Status: MERGED	+2	0