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QtWidget application: OK with mouse, Crashes with Touchscreen

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  • S sitti

    I am running on a ARM based Linux device a very basic application with 1 QPushButton and 1 QLabel. I am experiencing this strange problem: if I use the mouse to interact with the app, all is OK. If I reconfigure the device in order to enable thetouchscree, when I touch the QPushbutton (or other) the app crashes with Segmentation Fault.
    Can anyone give me a suggestion to guide me in the right direction to solve the problem please? Thanks!

    Pablo J. RoginaP Offline
    Pablo J. RoginaP Offline
    Pablo J. Rogina
    wrote on last edited by
    #2

    @sitti said in QtWidget application: OK with mouse, Crashes with Touchscreen:

    Can anyone give me a suggestion to guide me in the right direction to solve the problem please?

    Besides enabling debugging, are you able to run any other non-Qt application using the touchscreen?

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    • JoeCFDJ Offline
      JoeCFDJ Offline
      JoeCFD
      wrote on last edited by
      #3

      make a debug build and show your backtrace here.

      S 1 Reply Last reply
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      • JoeCFDJ JoeCFD

        make a debug build and show your backtrace here.

        S Offline
        S Offline
        sitti
        wrote on last edited by
        #4

        @JoeCFD You mean run it via debugger or simply make a debug build and run it on the device?

        jsulmJ 1 Reply Last reply
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        • S sitti

          @JoeCFD You mean run it via debugger or simply make a debug build and run it on the device?

          jsulmJ Offline
          jsulmJ Offline
          jsulm
          Lifetime Qt Champion
          wrote on last edited by
          #5

          @sitti Run a debug build in a debugger

          https://forum.qt.io/topic/113070/qt-code-of-conduct

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          • S Offline
            S Offline
            sitti
            wrote on last edited by sitti
            #6

            @jsulm Still trying to debug my application via SSH with the built-in debugger in Qt Creator, but I get the following error message:

            The remote file system has only 0 megabytes of free space, but 5 megabytes are required.
            

            I don't think there is a real problem about space in the device.
            Anyone have any suggestion please?

            S 1 Reply Last reply
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            • S sitti

              @jsulm Still trying to debug my application via SSH with the built-in debugger in Qt Creator, but I get the following error message:

              The remote file system has only 0 megabytes of free space, but 5 megabytes are required.
              

              I don't think there is a real problem about space in the device.
              Anyone have any suggestion please?

              S Offline
              S Offline
              sitti
              wrote on last edited by
              #7

              Doing df -h on the device, I obtain the following:

              Filesystem                Size      Used Available Use% Mounted on
              /dev/root                25.3M     25.3M         0 100% /
              devtmpfs                234.3M         0    234.3M   0% /dev
              tmpfs                   234.6M         0    234.6M   0% /dev/shm
              tmpfs                   234.6M    232.0K    234.4M   0% /tmp
              ubi0:data               462.3M     83.8M    378.5M  18% /media/nand
              
              jsulmJ 1 Reply Last reply
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              • S sitti

                Doing df -h on the device, I obtain the following:

                Filesystem                Size      Used Available Use% Mounted on
                /dev/root                25.3M     25.3M         0 100% /
                devtmpfs                234.3M         0    234.3M   0% /dev
                tmpfs                   234.6M         0    234.6M   0% /dev/shm
                tmpfs                   234.6M    232.0K    234.4M   0% /tmp
                ubi0:data               462.3M     83.8M    378.5M  18% /media/nand
                
                jsulmJ Offline
                jsulmJ Offline
                jsulm
                Lifetime Qt Champion
                wrote on last edited by
                #8

                @sitti Root file system is indeed full. To which location do you deploy your app?

                https://forum.qt.io/topic/113070/qt-code-of-conduct

                S 1 Reply Last reply
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                • jsulmJ jsulm

                  @sitti Root file system is indeed full. To which location do you deploy your app?

                  S Offline
                  S Offline
                  sitti
                  wrote on last edited by
                  #9

                  @jsulm you are right. I'm trying to figure out where that /dev/root came from. I want to deploy in /media/nand/project

                  1 Reply Last reply
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                  • S Offline
                    S Offline
                    sitti
                    wrote on last edited by sitti
                    #10

                    I solved the space leakage adding my deploy path on "Remote path to check for free space" in Run Settings in Qt Creator.
                    Now, when I launch the application in the debugger, it does not start, and the following error message appears on the output console:

                    Process /media/nand/project/verySimpleApp created; pid = 3569
                    File transfers from remote targets can be slow. Use "set sysroot" to access files locally instead.
                    Unable to find dynamic linker breakpoint function.
                    GDB will be unable to debug shared library initializers
                    and track explicitly loaded dynamic code./media/nand/project/verySimpleApp: error while loading shared libraries: libQt5Widgets.so.5: cannot open shared object file: No such file or directory
                    

                    In the device, the Qt libraries are in a custom path, and I add that path to the LD_LIBRARY_PATH environmental variable. In fact, if I run the application directly on the device, it starts. Have I to tell the debugger where the Qt libraries on the target are?
                    Thanks.

                    S 1 Reply Last reply
                    0
                    • S sitti

                      I solved the space leakage adding my deploy path on "Remote path to check for free space" in Run Settings in Qt Creator.
                      Now, when I launch the application in the debugger, it does not start, and the following error message appears on the output console:

                      Process /media/nand/project/verySimpleApp created; pid = 3569
                      File transfers from remote targets can be slow. Use "set sysroot" to access files locally instead.
                      Unable to find dynamic linker breakpoint function.
                      GDB will be unable to debug shared library initializers
                      and track explicitly loaded dynamic code./media/nand/project/verySimpleApp: error while loading shared libraries: libQt5Widgets.so.5: cannot open shared object file: No such file or directory
                      

                      In the device, the Qt libraries are in a custom path, and I add that path to the LD_LIBRARY_PATH environmental variable. In fact, if I run the application directly on the device, it starts. Have I to tell the debugger where the Qt libraries on the target are?
                      Thanks.

                      S Offline
                      S Offline
                      sitti
                      wrote on last edited by sitti
                      #11

                      @jsulm Ok, I solved the missing library issue by adding the proper environmental variables in the Environment field Project -> Run in Qt Creator. Now I am able to deploy my application.
                      Returning to the main topic:

                      • I run a debug build of my application in the debugger
                      • When I touch for the first time the screen, the application crashes
                        In the application Output window there are no insteresting messages, but a pop up appears with the following error:
                      The inferior stopped because it received a signal from the operating system.
                      Signal name : SIGSEGV
                      Signal meaning : Segmentation fault
                      

                      Running the app with the debugger, I was hoping to have some additional information .. Any help is appreciated.

                      jsulmJ 1 Reply Last reply
                      0
                      • S sitti

                        @jsulm Ok, I solved the missing library issue by adding the proper environmental variables in the Environment field Project -> Run in Qt Creator. Now I am able to deploy my application.
                        Returning to the main topic:

                        • I run a debug build of my application in the debugger
                        • When I touch for the first time the screen, the application crashes
                          In the application Output window there are no insteresting messages, but a pop up appears with the following error:
                        The inferior stopped because it received a signal from the operating system.
                        Signal name : SIGSEGV
                        Signal meaning : Segmentation fault
                        

                        Running the app with the debugger, I was hoping to have some additional information .. Any help is appreciated.

                        jsulmJ Offline
                        jsulmJ Offline
                        jsulm
                        Lifetime Qt Champion
                        wrote on last edited by
                        #12

                        @sitti If you run through debugger there must be more information in the debug view (the stack trace). So, please take closer look at debug output.

                        https://forum.qt.io/topic/113070/qt-code-of-conduct

                        1 Reply Last reply
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                        • S Offline
                          S Offline
                          sitti
                          wrote on last edited by
                          #13

                          The problem is that I have no idea where to put a breakpoint to stop the execution and go step by step, because the app crashes when I touch the screen before any slot is called..

                          jsulmJ 1 Reply Last reply
                          0
                          • S sitti

                            The problem is that I have no idea where to put a breakpoint to stop the execution and go step by step, because the app crashes when I touch the screen before any slot is called..

                            jsulmJ Offline
                            jsulmJ Offline
                            jsulm
                            Lifetime Qt Champion
                            wrote on last edited by jsulm
                            #14

                            @sitti There is no need to put any break points in this case. Simply start the app through debugger, after it crashes close the dialog telling you that it crashed and then check the stack trace in debugger view.

                            https://forum.qt.io/topic/113070/qt-code-of-conduct

                            S 1 Reply Last reply
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                            • jsulmJ jsulm

                              @sitti There is no need to put any break points in this case. Simply start the app through debugger, after it crashes close the dialog telling you that it crashed and then check the stack trace in debugger view.

                              S Offline
                              S Offline
                              sitti
                              wrote on last edited by
                              #15

                              @jsulm I's sorry, perhaps I have a non.standard view. Please explain me what do you mean with "stack trace in the debugger view". Below is my view when I close the dialog containing the error message:
                              06bac469-dca2-4d98-945b-e308e7f47ded-immagine.png

                              jsulmJ 1 Reply Last reply
                              0
                              • S sitti

                                @jsulm I's sorry, perhaps I have a non.standard view. Please explain me what do you mean with "stack trace in the debugger view". Below is my view when I close the dialog containing the error message:
                                06bac469-dca2-4d98-945b-e308e7f47ded-immagine.png

                                jsulmJ Offline
                                jsulmJ Offline
                                jsulm
                                Lifetime Qt Champion
                                wrote on last edited by jsulm
                                #16

                                @sitti said in QtWidget application: OK with mouse, Crashes with Touchscreen:

                                stack trace in the debugger view"

                                Stack trace is what you see in your screen shot in bottom left corner. It shows the chain of calls leading to the crash.
                                Please build in debug mode to get readable information...

                                https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                • S Offline
                                  S Offline
                                  sitti
                                  wrote on last edited by
                                  #17

                                  @jsulm thanks, now that's clear. There should be another issue, because I am actually running in debug mode:
                                  4ffb0e09-c082-4655-9ff5-efbd76f16741-immagine.png

                                  jsulmJ 1 Reply Last reply
                                  0
                                  • S sitti

                                    @jsulm thanks, now that's clear. There should be another issue, because I am actually running in debug mode:
                                    4ffb0e09-c082-4655-9ff5-efbd76f16741-immagine.png

                                    jsulmJ Offline
                                    jsulmJ Offline
                                    jsulm
                                    Lifetime Qt Champion
                                    wrote on last edited by
                                    #18

                                    @sitti said in QtWidget application: OK with mouse, Crashes with Touchscreen:

                                    I am actually running in debug mode

                                    What I mean is: build first in debug mode, not in release mode, then run through debugger.

                                    https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                    • S Offline
                                      S Offline
                                      sitti
                                      wrote on last edited by
                                      #19

                                      @jsulm It is actually what I am doing.

                                      1 Reply Last reply
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