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App crash during valgrind, on QProcess::start

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  • ocgltdO ocgltd

    I added my code to the question. Yes it crashes in gdb too (when running WITH valgrind). But, in debug mode alone it does not crash, and from command line with gdb it does not crash.

    Is this a Fedora34 + valgrind issue? I've never encountered this type of problem before so unsure...

    JoeCFDJ Offline
    JoeCFDJ Offline
    JoeCFD
    wrote on last edited by
    #4

    @ocgltd valgrind runs very slow normally. Do you have any syn actions or updates or sort of multi-threading after process starts?

    ocgltdO 1 Reply Last reply
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    • JoeCFDJ JoeCFD

      @ocgltd valgrind runs very slow normally. Do you have any syn actions or updates or sort of multi-threading after process starts?

      ocgltdO Offline
      ocgltdO Offline
      ocgltd
      wrote on last edited by
      #5

      @JoeCFD I have other threads running, but this thread is blocked at the start method. Those other threads don't interact with this thread in any way....(not sure how to interpret your question)

      JoeCFDJ 1 Reply Last reply
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      • ocgltdO ocgltd

        @JoeCFD I have other threads running, but this thread is blocked at the start method. Those other threads don't interact with this thread in any way....(not sure how to interpret your question)

        JoeCFDJ Offline
        JoeCFDJ Offline
        JoeCFD
        wrote on last edited by JoeCFD
        #6

        @ocgltd not sure if the process needs any resources from somewhere else. If no, simply comment out this piece of code to run valgrind. The purpose of running valgrind is to find memory issues. If this process is a simple run and your code works fine, this part of the code will not cause any memory problem and you can simply ignore it.

        ocgltdO JoeCFDJ 2 Replies Last reply
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        • JoeCFDJ JoeCFD

          @ocgltd not sure if the process needs any resources from somewhere else. If no, simply comment out this piece of code to run valgrind. The purpose of running valgrind is to find memory issues. If this process is a simple run and your code works fine, this part of the code will not cause any memory problem and you can simply ignore it.

          ocgltdO Offline
          ocgltdO Offline
          ocgltd
          wrote on last edited by
          #7

          @JoeCFD The data returned by this QProcess is actually important to the program. But I'll assume this is a valgrind + FC34 issue.

          I'll try the same under Red Hat 7 in the near future and will update the thread.

          ocgltdO 1 Reply Last reply
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          • JoeCFDJ JoeCFD

            @ocgltd not sure if the process needs any resources from somewhere else. If no, simply comment out this piece of code to run valgrind. The purpose of running valgrind is to find memory issues. If this process is a simple run and your code works fine, this part of the code will not cause any memory problem and you can simply ignore it.

            JoeCFDJ Offline
            JoeCFDJ Offline
            JoeCFD
            wrote on last edited by
            #8

            @JoeCFD
            Another tool to check memory issue is asan. Add this to your cmake
            set( CMAKE_CXX_FLAGS_DEBUG "-g -fsanitize-recover=address -fsanitize=address" CACHE STRING "compile flags" FORCE )
            try it out as well.

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            • JoeCFDJ Offline
              JoeCFDJ Offline
              JoeCFD
              wrote on last edited by
              #9

              https://forum.qt.io/topic/16837/program-started-with-qprocess-results-in-segmentation-fault-works-fine-on-console/7

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              • ocgltdO ocgltd

                @JoeCFD The data returned by this QProcess is actually important to the program. But I'll assume this is a valgrind + FC34 issue.

                I'll try the same under Red Hat 7 in the near future and will update the thread.

                ocgltdO Offline
                ocgltdO Offline
                ocgltd
                wrote on last edited by
                #10

                @ocgltd I tried valgrind under Fedora 38 and the problem remains...

                JoeCFDJ 1 Reply Last reply
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                • ocgltdO ocgltd

                  @ocgltd I tried valgrind under Fedora 38 and the problem remains...

                  JoeCFDJ Offline
                  JoeCFDJ Offline
                  JoeCFD
                  wrote on last edited by JoeCFD
                  #11

                  @ocgltd
                  in the link I posted above. There is something like:
                  today I tried to run my sender process with QProcess::startDetached() and it worked without any problems.
                  Try it out. If it works, simply change it back if you prefer the process to be attached after valgrind run.

                  I have a few processes running in my app and do not have this issue.

                  ocgltdO 1 Reply Last reply
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                  • JoeCFDJ JoeCFD

                    @ocgltd
                    in the link I posted above. There is something like:
                    today I tried to run my sender process with QProcess::startDetached() and it worked without any problems.
                    Try it out. If it works, simply change it back if you prefer the process to be attached after valgrind run.

                    I have a few processes running in my app and do not have this issue.

                    ocgltdO Offline
                    ocgltdO Offline
                    ocgltd
                    wrote on last edited by ocgltd
                    #12

                    @JoeCFD I tried using startDetached and my app still crashed at the same point. However, it dumped the stdout of my process to the terminal window, following by html tag structured valgrind output.

                    Another clue, is that after crashing valgrind reports:

                    syscall param waitid(infop) points to unaddressable byte(s)
                    

                    on the QProcess.start line

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                    • JoeCFDJ Offline
                      JoeCFDJ Offline
                      JoeCFD
                      wrote on last edited by
                      #13

                      https://bugreports.qt.io/browse/QTBUG-82351

                      ocgltdO 1 Reply Last reply
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                      • JoeCFDJ JoeCFD

                        https://bugreports.qt.io/browse/QTBUG-82351

                        ocgltdO Offline
                        ocgltdO Offline
                        ocgltd
                        wrote on last edited by
                        #14

                        @JoeCFD Well that sure looks similar, so I'll chalk it up to a Qt bug for now. My app does lots of forking, so hard to temporarily disable this (to test for other leaks). So I'll just have to wait until this is fixed and recheck for leaks later.

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