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Thread: QApplication hanging on poll() (sometimes)

  1. #1
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    Question QApplication hanging on poll() (sometimes)

    I'm having an intermittent issue where the following main.cpp will hang on the call to QApplication (int argc, char *argv[]) at a poll() call.
    I'm using Qt 5.1.1, g++ 4.8.5 and Eclipse 4.11.0 on RHEL 7.8.

    This is the simple main program that QtCreator created for me so I'm assuming that it is doing it as expected.
    Qt Code:
    1. #include <QApplication>
    2.  
    3. #include "MyMainWindow.h"
    4.  
    5. int main (int argc, char *arg[])
    6. {
    7. QApplication a (argc, argv);
    8.  
    9. MyMainWindow w;
    10.  
    11. a.exec()
    12. }
    To copy to clipboard, switch view to plain text mode 

    I'm currently using Eclipse as my IDE and am using the .pro file from QtCreator and qmake to create a Makefile which I then compile with in Eclipse.

    My problem is that occasionally my program hangs and when I use the Eclipse debugger (gdb) to see where it's hanging up it's in a call to poll() . This means that it never leaves QApplication to start MyMainWindow.

    Like I said this only happens occasionally and sometimes I can just logoff and back on and it works. Rebooting the system always fixes it, but that's kind of exteme.

    Has anyone seen this before? It's very frustrating since I'm on a tight schedule and I can't reboot this system every time this happens.

  2. #2
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    Default Re: QApplication hanging on poll() (sometimes)

    Where is the call to "w.show()" to actually put your main window up on screen?

    And isn't there a "kill" command in linux to stop a process? Rebooting your PC just to stop a program seems a little extreme.
    <=== The Great Pumpkin says ===>
    Please use CODE tags when posting source code so it is more readable. Click "Go Advanced" and then the "#" icon to insert the tags. Paste your code between them.

  3. #3
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    Default Re: QApplication hanging on poll() (sometimes)

    Quote Originally Posted by d_stranz View Post
    Where is the call to "w.show()" to actually put your main window up on screen?
    It's in MyMainWidow

    And isn't there a "kill" command in linux to stop a process? Rebooting your PC just to stop a program seems a little extreme.
    After I exit out of the Eclipse, there's noting to kill.
    Last edited by DesertBroncoFan; 12th August 2021 at 16:54. Reason: reformatted to look better

  4. #4
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    Default Re: QApplication hanging on poll() (sometimes)

    I'm still having this problem.

    Could it be a result of having Gnome 3 on my system (there are other problems with this on RHEL 7.8)?

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