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Executing QProcess in QThread: memory leak

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  • sitesvS sitesv

    UPD:
    I found the cause of this situation. Ip's are not available. How to set a timeout for the process execution in this case?

    KroMignonK Offline
    KroMignonK Offline
    KroMignon
    wrote on last edited by
    #54

    @sitesv said in Executing QProcess in QThread: memory leak:

    How to set a timeout for the process execution in this case?

    Have you tried to look at ping parameters (ping --help)

    And I would only wait once, for all pings to be done:

    QStringList ip_list = {"192.168.0.1", "192.168.0.2"};
    int success_count = 0;
    int pingsToDo = ip_list.count();
    QEventLoop l;
    foreach(auto ip, ip_list)
    {
        QProcess ping;
        ping.setProcessChannelMode(QProcess::MergedChannels);
        connect(&ping,
                QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
                [&l, &ping, &success_count, &pingsToDo]() {
                    --pingsToDo;
                    QString output(ping.readAll());
                    if(output.contains("ttl",Qt::CaseInsensitive)) success_count++;
                    if(!pingsToDo)
                        l.exit();
                });
        ping.start("/bin/ping", QStringList() << ip << "-c" << "1");
    }
    
    // wait all pings done
    l.exec();
    if(success_count == ip_list.count())
       emit setStatus(true);
    else
       emit setStatus(false);
    m_timer->start();
    

    It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

    sitesvS 1 Reply Last reply
    1
    • KroMignonK KroMignon

      @sitesv said in Executing QProcess in QThread: memory leak:

      How to set a timeout for the process execution in this case?

      Have you tried to look at ping parameters (ping --help)

      And I would only wait once, for all pings to be done:

      QStringList ip_list = {"192.168.0.1", "192.168.0.2"};
      int success_count = 0;
      int pingsToDo = ip_list.count();
      QEventLoop l;
      foreach(auto ip, ip_list)
      {
          QProcess ping;
          ping.setProcessChannelMode(QProcess::MergedChannels);
          connect(&ping,
                  QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
                  [&l, &ping, &success_count, &pingsToDo]() {
                      --pingsToDo;
                      QString output(ping.readAll());
                      if(output.contains("ttl",Qt::CaseInsensitive)) success_count++;
                      if(!pingsToDo)
                          l.exit();
                  });
          ping.start("/bin/ping", QStringList() << ip << "-c" << "1");
      }
      
      // wait all pings done
      l.exec();
      if(success_count == ip_list.count())
         emit setStatus(true);
      else
         emit setStatus(false);
      m_timer->start();
      
      sitesvS Offline
      sitesvS Offline
      sitesv
      wrote on last edited by sitesv
      #55

      @KroMignon said in Executing QProcess in QThread: memory leak:

      And I would only wait once, for all pings to be done:

      Wow! Very nice!! Thank you!

      @KroMignon
      UPD: app is freezing on line l.exec() althought l.exit() is done....

      1 Reply Last reply
      0
      • sitesvS Offline
        sitesvS Offline
        sitesv
        wrote on last edited by
        #56

        Guys, how to resolve this?

        KroMignonK 1 Reply Last reply
        0
        • sitesvS sitesv

          Guys, how to resolve this?

          KroMignonK Offline
          KroMignonK Offline
          KroMignon
          wrote on last edited by
          #57

          @sitesv said in Executing QProcess in QThread: memory leak:

          Guys, how to resolve this?

          Hmm, I think it is a tricky issue. I would start with forcing QueuedConnection, to avoid threading issues:

          connect(&ping,
                      QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
                      [&l, &ping, &success_count, &pingsToDo]() {
                          ...
                      }, Qt::QueuedConnection);
          

          It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

          sitesvS 1 Reply Last reply
          0
          • KroMignonK KroMignon

            @sitesv said in Executing QProcess in QThread: memory leak:

            Guys, how to resolve this?

            Hmm, I think it is a tricky issue. I would start with forcing QueuedConnection, to avoid threading issues:

            connect(&ping,
                        QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
                        [&l, &ping, &success_count, &pingsToDo]() {
                            ...
                        }, Qt::QueuedConnection);
            
            sitesvS Offline
            sitesvS Offline
            sitesv
            wrote on last edited by
            #58

            @KroMignon said in Executing QProcess in QThread: memory leak:

            connect(&ping,
            QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
            &l, &ping, &success_count, &pingsToDo {
            ...
            }, Qt::QueuedConnection);

            'connect' failed again
            img1.png

            KroMignonK 2 Replies Last reply
            0
            • sitesvS sitesv

              @KroMignon said in Executing QProcess in QThread: memory leak:

              connect(&ping,
              QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
              &l, &ping, &success_count, &pingsToDo {
              ...
              }, Qt::QueuedConnection);

              'connect' failed again
              img1.png

              KroMignonK Offline
              KroMignonK Offline
              KroMignon
              wrote on last edited by KroMignon
              #59

              @sitesv Can you show the code you have written

              Sorry my fault, should be:

              connect(&ping,
                      QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
                      &l, // receiver!
                      [&l, &ping, &success_count, &pingsToDo]() {
                          ...
                      }, Qt::QueuedConnection);
              

              It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

              sitesvS 1 Reply Last reply
              0
              • KroMignonK KroMignon

                @sitesv Can you show the code you have written

                Sorry my fault, should be:

                connect(&ping,
                        QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
                        &l, // receiver!
                        [&l, &ping, &success_count, &pingsToDo]() {
                            ...
                        }, Qt::QueuedConnection);
                
                sitesvS Offline
                sitesvS Offline
                sitesv
                wrote on last edited by
                #60

                @KroMignon

                QStringList ip_list = {"192.168.0.1", "192.168.0.2"};
                    int success_count = 0;
                    int pingsToDo = ip_list.count();
                    QEventLoop l; // used for passive wait until process finished
                    foreach(auto ip, ip_list)
                    {
                        QProcess ping;
                        ping.setProcessChannelMode(QProcess::MergedChannels);
                        connect(&ping,
                                QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished), &l,
                                [&l, &ping, &success_count, &pingsToDo]() {
                                    --pingsToDo;
                                    QString output(ping.readAll()); // <<<<<<<<<<<<<<<< SIGSEGV Segmentation fault
                                    if(output.contains("ttl",Qt::CaseInsensitive)){
                                        success_count++;
                                    }
                                    if(!pingsToDo){
                                        l.exit();
                                    }
                                }, Qt::QueuedConnection);
                        ping.start("/bin/ping", QStringList() << ip << "-c" << "1");
                    }
                    l.exec();
                    if(success_count == ip_list.count()) emit setLedStatus(0, 0, true);
                    else                                 emit setLedStatus(0, 0, false);
                
                    m_timer->start();
                
                

                There is SIGSEGV Segmentation fault on ping.readAll string. :((

                1 Reply Last reply
                0
                • sitesvS sitesv

                  @KroMignon said in Executing QProcess in QThread: memory leak:

                  connect(&ping,
                  QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
                  &l, &ping, &success_count, &pingsToDo {
                  ...
                  }, Qt::QueuedConnection);

                  'connect' failed again
                  img1.png

                  KroMignonK Offline
                  KroMignonK Offline
                  KroMignon
                  wrote on last edited by KroMignon
                  #61

                  @sitesv Sorry but I was a little bit confused when I suggest you this code.
                  This cannot work, because QProcess is killed/destroyed at end of the for loop!
                  Should be:

                  QStringList ip_list = {"192.168.0.1", "192.168.0.2"};
                  int success_count = 0;
                  int pingsToDo = ip_list.count();
                  QEventLoop l;
                  foreach(auto ip, ip_list)
                  {
                      auto ping = new QProcess();
                      ping->setProcessChannelMode(QProcess::MergedChannels);
                      connect(ping,
                              QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
                              [&l, ping, &success_count, &pingsToDo]() {
                                  --pingsToDo;
                                  QString output(ping->readAll());
                                  if(output.contains("ttl",Qt::CaseInsensitive))
                                      success_count++;
                                  // free memory
                                  ping->deleteLater();
                                  //  exit event loop after all pings done
                                  if(!pingsToDo)
                                      l.exit();
                              });
                      ping->start("/bin/ping", QStringList() << ip << "-c" << "1");
                  }
                  
                  // wait all pings done
                  l.exec();
                  

                  It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                  1 Reply Last reply
                  0
                  • JonBJ Online
                    JonBJ Online
                    JonB
                    wrote on last edited by
                    #62

                    @sitesv , @KroMignon
                    I will say one thing.

                    You are writing code which will call QEventLoop::exec(), blocking whatever calls it. It relies on hitting the QEventLoop::exit() statement, which you only have in response to the QProcess::finished signal. If for whatever reason that does not get hit, your event loop will never be exited.

                    I would not write production (or even development) code like this, and certainly not for distribution. It is asking for an "unseen hang" to occur, one day. I would at minimum hook onto QProcess::errorOccurred, maybe stateChanged() too. And I would put in some sort of timer/timeout, so that if something goes badly wrong you get out of the blocking loop (with perhaps an error flag) instead of waiting for Hell to freeze over....

                    KroMignonK 1 Reply Last reply
                    3
                    • JonBJ JonB

                      @sitesv , @KroMignon
                      I will say one thing.

                      You are writing code which will call QEventLoop::exec(), blocking whatever calls it. It relies on hitting the QEventLoop::exit() statement, which you only have in response to the QProcess::finished signal. If for whatever reason that does not get hit, your event loop will never be exited.

                      I would not write production (or even development) code like this, and certainly not for distribution. It is asking for an "unseen hang" to occur, one day. I would at minimum hook onto QProcess::errorOccurred, maybe stateChanged() too. And I would put in some sort of timer/timeout, so that if something goes badly wrong you get out of the blocking loop (with perhaps an error flag) instead of waiting for Hell to freeze over....

                      KroMignonK Offline
                      KroMignonK Offline
                      KroMignon
                      wrote on last edited by
                      #63

                      @JonB said in Executing QProcess in QThread: memory leak:

                      I would not write production (or even development) code like this, and certainly not for distribution. It is asking for an "unseen hang" to occur, one day. I would at minimum hook onto QProcess::errorOccurred, maybe stateChanged() too. And I would put in some sort of timer/timeout, so that if something goes badly wrong you get out of the blocking loop (with perhaps an error flag) instead of waiting for Hell to freeze over....

                      Yes, this is a good advice.

                      It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                      sitesvS 1 Reply Last reply
                      1
                      • KroMignonK KroMignon

                        @JonB said in Executing QProcess in QThread: memory leak:

                        I would not write production (or even development) code like this, and certainly not for distribution. It is asking for an "unseen hang" to occur, one day. I would at minimum hook onto QProcess::errorOccurred, maybe stateChanged() too. And I would put in some sort of timer/timeout, so that if something goes badly wrong you get out of the blocking loop (with perhaps an error flag) instead of waiting for Hell to freeze over....

                        Yes, this is a good advice.

                        sitesvS Offline
                        sitesvS Offline
                        sitesv
                        wrote on last edited by sitesv
                        #64

                        @JonB said in Executing QProcess in QThread: memory leak:

                        You are writing code which will call QEventLoop::exec(), blocking whatever calls it. It relies on hitting the QEventLoop::exit() statement, which you only have in response to the QProcess::finished signal. If for whatever reason that does not get hit, your event loop will never be exited.

                        Maybe my first variant was good (QThread + QProcess)?

                        if(!myProcess) myProcess = new QProcess(this);
                        myProcess->start(exe_path, arguments);
                        myProcess->waitForFinished(500);
                        output = myProcess->readAll();
                        output_str = codec->toUnicode(output);
                        output_strlst = output_str.split("\r\n");
                        myProcess->close();
                        ...
                        

                        There is QProcess "waitForFinished" with timeout.
                        The app wasn't freezing with this approach.

                        KroMignonK jsulmJ 2 Replies Last reply
                        0
                        • sitesvS sitesv

                          @JonB said in Executing QProcess in QThread: memory leak:

                          You are writing code which will call QEventLoop::exec(), blocking whatever calls it. It relies on hitting the QEventLoop::exit() statement, which you only have in response to the QProcess::finished signal. If for whatever reason that does not get hit, your event loop will never be exited.

                          Maybe my first variant was good (QThread + QProcess)?

                          if(!myProcess) myProcess = new QProcess(this);
                          myProcess->start(exe_path, arguments);
                          myProcess->waitForFinished(500);
                          output = myProcess->readAll();
                          output_str = codec->toUnicode(output);
                          output_strlst = output_str.split("\r\n");
                          myProcess->close();
                          ...
                          

                          There is QProcess "waitForFinished" with timeout.
                          The app wasn't freezing with this approach.

                          KroMignonK Offline
                          KroMignonK Offline
                          KroMignon
                          wrote on last edited by
                          #65

                          @sitesv said in Executing QProcess in QThread: memory leak:

                          There is QProcess "waitForFinished" with timeout.
                          The app wasn't freezing with this approach.

                          Why not, but you have to wait ping finished before starting next.
                          If it is what you want, then go with it.

                          It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                          1 Reply Last reply
                          0
                          • sitesvS sitesv

                            @JonB said in Executing QProcess in QThread: memory leak:

                            You are writing code which will call QEventLoop::exec(), blocking whatever calls it. It relies on hitting the QEventLoop::exit() statement, which you only have in response to the QProcess::finished signal. If for whatever reason that does not get hit, your event loop will never be exited.

                            Maybe my first variant was good (QThread + QProcess)?

                            if(!myProcess) myProcess = new QProcess(this);
                            myProcess->start(exe_path, arguments);
                            myProcess->waitForFinished(500);
                            output = myProcess->readAll();
                            output_str = codec->toUnicode(output);
                            output_strlst = output_str.split("\r\n");
                            myProcess->close();
                            ...
                            

                            There is QProcess "waitForFinished" with timeout.
                            The app wasn't freezing with this approach.

                            jsulmJ Offline
                            jsulmJ Offline
                            jsulm
                            Lifetime Qt Champion
                            wrote on last edited by
                            #66

                            @sitesv I'm still wondering why you think you need a local event loop...

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

                            sitesvS 1 Reply Last reply
                            1
                            • jsulmJ jsulm

                              @sitesv I'm still wondering why you think you need a local event loop...

                              sitesvS Offline
                              sitesvS Offline
                              sitesv
                              wrote on last edited by
                              #67

                              @jsulm said in Executing QProcess in QThread: memory leak:

                              @sitesv I'm still wondering why you think you need a local event loop...

                              Hi! I have done variant as you recommend. It's working!

                              void PingTester::doPing(){
                                  QStringList ip_list = {"192.168.0.1", "192.168.0.2"};
                                  int success_count = 0;
                                  int pingsToDo = ip_list.count();
                                  int ipCnt = pingsToDo;
                                  foreach(auto ip, ip_list)
                                  {
                                      QProcess ping;
                                      ping.setProcessChannelMode(QProcess::MergedChannels);
                                      connect(&ping,
                                              QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
                                              [this, &ping, &success_count, &pingsToDo, ipCnt]() {
                                                  --pingsToDo;
                                                  QString output(ping.readAll());
                                                  if(output.contains("ttl",Qt::CaseInsensitive)){
                                                      success_count++;
                                                  }
                                                  if(!pingsToDo){
                                                      if(success_count == ipCnt) emit setStatus(true);
                                                      else                       emit setStatus(false);
                                                      m_timer->start();
                                                  }
                                              });
                                      ping.start("/bin/ping", QStringList() << ip << "-c" << "1" << "-w" << "1");
                                  }
                              }
                              

                              I made another experiment:

                              1. Created a QThread
                              2. In QThread::run() method::
                              • made a QTimer* object,
                              • set him as "one shot kind",
                              • ran QTimer, and in final
                                * ran QThread::exec() (for run local EventLoop)...
                              1. There is timer->start() in timeout slot, It executed, but QTimer doesn't start again.

                              Any ideas?

                              JonBJ KroMignonK 2 Replies Last reply
                              0
                              • sitesvS sitesv

                                @jsulm said in Executing QProcess in QThread: memory leak:

                                @sitesv I'm still wondering why you think you need a local event loop...

                                Hi! I have done variant as you recommend. It's working!

                                void PingTester::doPing(){
                                    QStringList ip_list = {"192.168.0.1", "192.168.0.2"};
                                    int success_count = 0;
                                    int pingsToDo = ip_list.count();
                                    int ipCnt = pingsToDo;
                                    foreach(auto ip, ip_list)
                                    {
                                        QProcess ping;
                                        ping.setProcessChannelMode(QProcess::MergedChannels);
                                        connect(&ping,
                                                QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
                                                [this, &ping, &success_count, &pingsToDo, ipCnt]() {
                                                    --pingsToDo;
                                                    QString output(ping.readAll());
                                                    if(output.contains("ttl",Qt::CaseInsensitive)){
                                                        success_count++;
                                                    }
                                                    if(!pingsToDo){
                                                        if(success_count == ipCnt) emit setStatus(true);
                                                        else                       emit setStatus(false);
                                                        m_timer->start();
                                                    }
                                                });
                                        ping.start("/bin/ping", QStringList() << ip << "-c" << "1" << "-w" << "1");
                                    }
                                }
                                

                                I made another experiment:

                                1. Created a QThread
                                2. In QThread::run() method::
                                • made a QTimer* object,
                                • set him as "one shot kind",
                                • ran QTimer, and in final
                                  * ran QThread::exec() (for run local EventLoop)...
                                1. There is timer->start() in timeout slot, It executed, but QTimer doesn't start again.

                                Any ideas?

                                JonBJ Online
                                JonBJ Online
                                JonB
                                wrote on last edited by JonB
                                #68

                                @sitesv
                                I don't know how/whether your issue relates this, but in your code: you set off ping.start(), but QProcess ping; is a local variable in your foreach loop and so immediately goes out of scope (not to mention, you also re-use the same local variable for each time round the loop, overwriting/destroying the previous one). Nothing should work (it might actually "crash"), I don't understand how you say it does.

                                On top of all of this: I think we've said it already here above, but goodness only knows why you are using a thread, with all the complications that involves? If you want to run a QProcess and the main thread to know when it's finished, it's asynchronous anyway, it would be a whole lot simpler not to have any thread. I think I said this earlier, but up to you.

                                And finally, while I'm on a roll: I think you are just using a /bin/ping in order to read the textual output, parse it, and see whether something is there/alive. In which case I'd be tempted to just write it myself in Qt instead of running some external command, I would have thought it's only a few lines of code. Your "parsing" of the output is beyond hokey, not even sure what you think it tells you....

                                1 Reply Last reply
                                0
                                • sitesvS sitesv

                                  @jsulm said in Executing QProcess in QThread: memory leak:

                                  @sitesv I'm still wondering why you think you need a local event loop...

                                  Hi! I have done variant as you recommend. It's working!

                                  void PingTester::doPing(){
                                      QStringList ip_list = {"192.168.0.1", "192.168.0.2"};
                                      int success_count = 0;
                                      int pingsToDo = ip_list.count();
                                      int ipCnt = pingsToDo;
                                      foreach(auto ip, ip_list)
                                      {
                                          QProcess ping;
                                          ping.setProcessChannelMode(QProcess::MergedChannels);
                                          connect(&ping,
                                                  QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
                                                  [this, &ping, &success_count, &pingsToDo, ipCnt]() {
                                                      --pingsToDo;
                                                      QString output(ping.readAll());
                                                      if(output.contains("ttl",Qt::CaseInsensitive)){
                                                          success_count++;
                                                      }
                                                      if(!pingsToDo){
                                                          if(success_count == ipCnt) emit setStatus(true);
                                                          else                       emit setStatus(false);
                                                          m_timer->start();
                                                      }
                                                  });
                                          ping.start("/bin/ping", QStringList() << ip << "-c" << "1" << "-w" << "1");
                                      }
                                  }
                                  

                                  I made another experiment:

                                  1. Created a QThread
                                  2. In QThread::run() method::
                                  • made a QTimer* object,
                                  • set him as "one shot kind",
                                  • ran QTimer, and in final
                                    * ran QThread::exec() (for run local EventLoop)...
                                  1. There is timer->start() in timeout slot, It executed, but QTimer doesn't start again.

                                  Any ideas?

                                  KroMignonK Offline
                                  KroMignonK Offline
                                  KroMignon
                                  wrote on last edited by
                                  #69

                                  @sitesv said in Executing QProcess in QThread: memory leak:

                                  Hi! I have done variant as you recommend. It's working!

                                  I am not sure this is really working!
                                  I think you have to (re)learn C++ object life cycle.
                                  You create a QProcess local instance in the for loop, this object will be destroyed at loop end.

                                  It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                                  1 Reply Last reply
                                  1
                                  • sitesvS Offline
                                    sitesvS Offline
                                    sitesv
                                    wrote on last edited by sitesv
                                    #70

                                    @JonB @KroMignon
                                    Agree with you, guys.
                                    But it works...
                                    I can reimplement to QProcess pointers of PingTester class...

                                    KroMignonK 1 Reply Last reply
                                    0
                                    • sitesvS sitesv

                                      @JonB @KroMignon
                                      Agree with you, guys.
                                      But it works...
                                      I can reimplement to QProcess pointers of PingTester class...

                                      KroMignonK Offline
                                      KroMignonK Offline
                                      KroMignon
                                      wrote on last edited by
                                      #71

                                      @sitesv said in Executing QProcess in QThread: memory leak:

                                      But it works...

                                      It don't, "it seems to work" would be the correct answer ;)

                                      If you try to ping a not valid/accessible IP address, I am pretty sure it will not work.

                                      If you want to do it sequentially, you have to be consistent in your choice:

                                      foreach(auto ip, ip_list)
                                      {
                                          QProcess ping;
                                          ping.setProcessChannelMode(QProcess::MergedChannels);
                                          ping.start("/bin/ping", QStringList() << ip << "-c" << "1" << "-w" << "1");
                                          ping.waitForFinished(5000); // wait up to 5 seconds
                                          QString output(ping.readAll());
                                          if(output.contains("ttl",Qt::CaseInsensitive)){
                                              success_count++;
                                          }
                                      }
                                      

                                      It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                                      sitesvS JonBJ 2 Replies Last reply
                                      0
                                      • KroMignonK KroMignon

                                        @sitesv said in Executing QProcess in QThread: memory leak:

                                        But it works...

                                        It don't, "it seems to work" would be the correct answer ;)

                                        If you try to ping a not valid/accessible IP address, I am pretty sure it will not work.

                                        If you want to do it sequentially, you have to be consistent in your choice:

                                        foreach(auto ip, ip_list)
                                        {
                                            QProcess ping;
                                            ping.setProcessChannelMode(QProcess::MergedChannels);
                                            ping.start("/bin/ping", QStringList() << ip << "-c" << "1" << "-w" << "1");
                                            ping.waitForFinished(5000); // wait up to 5 seconds
                                            QString output(ping.readAll());
                                            if(output.contains("ttl",Qt::CaseInsensitive)){
                                                success_count++;
                                            }
                                        }
                                        
                                        sitesvS Offline
                                        sitesvS Offline
                                        sitesv
                                        wrote on last edited by
                                        #72

                                        @KroMignon said in Executing QProcess in QThread: memory leak:

                                        If you try to ping a not valid/accessible IP address, I am pretty sure it will not work.

                                        There is "-w 1" key. It helps with unaccessible IP.

                                        KroMignonK 1 Reply Last reply
                                        0
                                        • KroMignonK KroMignon

                                          @sitesv said in Executing QProcess in QThread: memory leak:

                                          But it works...

                                          It don't, "it seems to work" would be the correct answer ;)

                                          If you try to ping a not valid/accessible IP address, I am pretty sure it will not work.

                                          If you want to do it sequentially, you have to be consistent in your choice:

                                          foreach(auto ip, ip_list)
                                          {
                                              QProcess ping;
                                              ping.setProcessChannelMode(QProcess::MergedChannels);
                                              ping.start("/bin/ping", QStringList() << ip << "-c" << "1" << "-w" << "1");
                                              ping.waitForFinished(5000); // wait up to 5 seconds
                                              QString output(ping.readAll());
                                              if(output.contains("ttl",Qt::CaseInsensitive)){
                                                  success_count++;
                                              }
                                          }
                                          
                                          JonBJ Online
                                          JonBJ Online
                                          JonB
                                          wrote on last edited by JonB
                                          #73

                                          @KroMignon
                                          I would think doing it sequentially, with waitForFinished(), for his multiple IP addresses would be a poor way to do things. He has a number of IP addresses to check, these should be done in parallel....

                                          1 Reply Last reply
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