c++ - what is causing this seq fault in Qt QGuiApplicationPrivate::processNativeEvent() -

-

i have simple qt program reading shared memory in separate thread. call routine waits until there data in shared memory segment, unblocks , returns , emits signal main gui thread. main gui thread slot received , in routine print std::cout received returns--no further data processing. program runs find 30 seconds seq faults.

running program under gdb catches seq fault , trace shows fault deep in event processing of qt. none of own code involved in seq fault. totally lost problem is.

here gdb output. in following gdb output, readsm() routine 1 blocks until there data available read shared memory, , readdatabuffer() slot main gui thread returns without further processing. there tons of std::cout lines signal , slot before seg fault. 

         ...many of following 2 lines before fault...     datareader::readsm(): calling m_psharedmemory->readwait()      readdatabuffer(): entered, returning      datareader::readsm(): calling m_psharedmemory->readwait()      readdatabuffer(): entered, returning 
  program received signal sigsegv, segmentation fault. 0xb72f5c54 in qguiapplicationprivate::processnativeevent(qwindow*, qbytearray const&, void*, long*) () /opt/qt/5.2.1/gcc/lib/libqt5gui.so.5 (gdb)  (gdb) bt #0  0xb72f5c54 in qguiapplicationprivate::processnativeevent(qwindow*, qbytearray const&, void*, long*) () /opt/qt/5.2.1/gcc/lib/libqt5gui.so.5 #1  0xb72e3ff3 in qwindowsysteminterface::handlenativeevent(qwindow*, qbytearray const&, void*, long*) ()     /opt/qt/5.2.1/gcc/lib/libqt5gui.so.5 #2  0xb3f40e2d in ?? () /opt/qt/5.2.1/gcc/plugins/platforms/libqxcb.so #3  0xb3f33170 in ?? () /opt/qt/5.2.1/gcc/plugins/platforms/libqxcb.so #4  0xb3f33dce in ?? () /opt/qt/5.2.1/gcc/plugins/platforms/libqxcb.so #5  0xb3f74e8b in ?? () /opt/qt/5.2.1/gcc/plugins/platforms/libqxcb.so #6  0xb701e943 in qmetacallevent::placemetacall(qobject*) ()        /opt/qt/5.2.1/gcc/lib/libqt5core.so.5 #7  0xb7021d92 in qobject::event(qevent*) () /opt/qt/5.2.1/gcc/lib/libqt5core.so.5 #8  0xb7913eb4 in qapplicationprivate::notify_helper(qobject*, qevent*) ()      /opt/qt/5.2.1/gcc/lib/libqt5widgets.so.5 #9  0xb7917d00 in qapplication::notify(qobject*, qevent*) ()      /opt/qt/5.2.1/gcc/lib/libqt5widgets.so.5 #10 0xb6ff3c2e in qcoreapplication::notifyinternal(qobject*, qevent*) ()      /opt/qt/5.2.1/gcc/lib/libqt5core.so.5 #11 0xb6ff68ec in qcoreapplicationprivate::sendpostedevents(qobject*, int, qthreaddata*) ()     /opt/qt/5.2.1/gcc/lib/libqt5core.so.5 #12 0xb6ff6e2c in qcoreapplication::sendpostedevents(qobject*, int) ()      /opt/qt/5.2.1/gcc/lib/libqt5core.so.5 #13 0xb704ad14 in ?? () /opt/qt/5.2.1/gcc/lib/libqt5core.so.5 #14 0xb68a06d3 in g_main_context_dispatch () /lib/i386-linux-gnu/libglib-2.0.so.0 #15 0xb68a0a70 in ?? () /lib/i386-linux-gnu/libglib-2.0.so.0 #16 0xb68a0b51 in g_main_context_iteration () /lib/i386-linux-gnu/libglib-2.0.so.0 #17 0xb704b128 in qeventdispatcherglib::processevents(qflags<qeventloop::processeventsflag>) ()     /opt/qt/5.2.1/gcc/lib/libqt5core.so.5 #18 0xb3f97836 in ?? () /opt/qt/5.2.1/gcc/plugins/platforms/libqxcb.so #19 0xb6ff22e6 in qeventloop::processevents(qflags<qeventloop::processeventsflag>) ()     /opt/qt/5.2.1/gcc/lib/libqt5core.so.5 #20 0xb6ff272c in qeventloop::exec(qflags<qeventloop::processeventsflag>) ()      /opt/qt/5.2.1/gcc/lib/libqt5core.so.5 #21 0xb6ff6ed2 in qcoreapplication::exec() () /opt/qt/5.2.1/gcc/lib/libqt5core.so.5 #22 0xb72f5b04 in qguiapplication::exec() () /opt/qt/5.2.1/gcc/lib/libqt5gui.so.5 #23 0xb790e914 in qapplication::exec() () /opt/qt/5.2.1/gcc/lib/libqt5widgets.so.5 #24 0x0805034b in main () (gdb)

since not processing of data in gui slot, , since program works fine 30 seconds usual signal/slots being called, @ loss @ causing seq fault in qt event processing.

any appreciated.

thanks,

-andres

update: thank andrew medico suggestion use valgrind. never thought of using debugging tool makes perfect sense. after using it, became obvious correct else causing problem , found cause elsewhere in code. on writing buffer. again andrew assistance.

-andres


Comments

Post a Comment

Popular posts from this blog

c++ - OpenCV Error: Assertion failed <scn == 3 ::scn == 4> in unknown function, -

-
i read alot other solution still confused should mine... #include <opencv2/objdetect/objdetect.hpp> #include <opencv2/highgui/highgui.hpp> #include <opencv2/imgproc/imgproc.hpp> #include <iostream> #include <stdio.h> using namespace std; using namespace cv; int main(int argc, const char** argv) { //create cascade classifier object used face detection cascadeclassifier face_cascade; //use haarcascade_frontalface_alt.xml library face_cascade.load("haarcascade_frontalface_alt.xml"); //setup video capture device , link first capture device videocapture capturedevice; capturedevice.open(0); //setup image files used in capture process mat captureframe; mat grayscaleframe; //create window present results namedwindow("outputcapture", 1); //create loop capture , find faces while (true) { //capture new image frame capturedevice >> captureframe; ...
Read more

php - render data via PDO::FETCH_FUNC vs loop -

-
i've been using 2 methods render data. the first one: function name($id,$name){ return '<div id="'.$id.'">'.$name.'</div>'; } echo implode($pdo->query("select id,name user")->fetchall(pdo::fetch_func,'name')); the second one: $users = $pdo->query("select id,name user")->fetchall(pdo::fetch_obj); foreach($users $user){ echo name($user->id,$user->name); } i don't understand how pdo::fetch_func works. tried figure out. however, not well-documented. could please explain fetch mode? , also, 1 performs better? thank you. both methods wrong , have learn how use templates , how separate business logic presentation logic. $users = $pdo->query("select id,name user")->fetchall(pdo::fetch_obj); tpl::assign('users', $users); is code business logic part. then in template <?php foreach $users $row): ?> <div id="<?=$...
Read more

The canvas has been tainted by cross-origin data in chrome only -

-
uncaught securityerror: failed execute 'getimagedata' on 'canvasrenderingcontext2d': canvas has been tainted cross-origin data i getting above error in chrome. code(following) works fine in mozilla. have not corss domain issue. why above error in chrome? var wheel_canvas, wheel_context, can_w, can_h, wheel_grd; var large_radius = 160; var small_radius = 120; var wheel_canvas = document.getelementbyid('wheel_canvas'); var wheel_context = wheel_canvas.getcontext('2d'); var can_w = $(wheel_canvas).width(); var can_h = $(wheel_canvas).height(); var centerx = can_w / 2, centery = can_h / 2; var wheel_grd = null; test('#ff0000'); function test(hex) { $('#clrpicker').css({'left': 210, 'top': 210 }); inverted = hexbw(hex); $('#color_val_show').val(hex); current_color_hex_val_selected = hex; $('#color_val_show').css({'color':inverted,'background':hex}); fillgradient...
Read more