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Memoy leak using QtCharts

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  • Christian EhrlicherC Offline
    Christian EhrlicherC Offline
    Christian Ehrlicher
    Lifetime Qt Champion
    wrote on last edited by
    #6

    A small, compilable testcase would be the best here so we can check it (and maybe at it to the bugreport later on) :)

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    1 Reply Last reply
    2
    • K Offline
      K Offline
      kuzulis
      Qt Champions 2020
      wrote on last edited by kuzulis
      #7

      @aawawa said in Memoy leak using QtCharts:

      hahahhabut by the way. I want to understand here why it doesn't work in this case!

      I'm too tried to use QtCharts and too faced with a memory leaks and etc.. I spat on QtCharts and replaced it with Qwt. (Because I haven't time to understand why QtCharts does not work as expected.. This was in Qt 5.9, as I remember).

      kshegunovK 1 Reply Last reply
      0
      • K kuzulis

        @aawawa said in Memoy leak using QtCharts:

        hahahhabut by the way. I want to understand here why it doesn't work in this case!

        I'm too tried to use QtCharts and too faced with a memory leaks and etc.. I spat on QtCharts and replaced it with Qwt. (Because I haven't time to understand why QtCharts does not work as expected.. This was in Qt 5.9, as I remember).

        kshegunovK Offline
        kshegunovK Offline
        kshegunov
        Moderators
        wrote on last edited by
        #8

        @kuzulis said in Memoy leak using QtCharts:

        I spat on QtCharts and replaced it with Qwt. (Because I haven't time to unterstand why QtCharts does not work as expected.. This was in Qt 5.9, as I remember).

        It hasn't improved since then. I did the same as you but picked QCustomPlot instead.

        Read and abide by the Qt Code of Conduct

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        • A Offline
          A Offline
          aawawa
          wrote on last edited by
          #9

          @Christian-Ehrlicher : please find a micro project here : link text

          @mrjj : if I comment as this :

          //SerieToAdd->append(i, sin(static_cast<double>(i) * 3.14*2
          

          I have always the memory leak but it seems to be less important (around 6ko)

          mrjjM 1 Reply Last reply
          0
          • A aawawa

            @Christian-Ehrlicher : please find a micro project here : link text

            @mrjj : if I comment as this :

            //SerieToAdd->append(i, sin(static_cast<double>(i) * 3.14*2
            

            I have always the memory leak but it seems to be less important (around 6ko)

            mrjjM Offline
            mrjjM Offline
            mrjj
            Lifetime Qt Champion
            wrote on last edited by
            #10

            @aawawa
            Ok so it does seems related to the series.
            If you want to dig into it, you can very handy browse code here
            https://code.woboq.org/qt5/

            Super with sample.

            1 Reply Last reply
            1
            • A Offline
              A Offline
              aawawa
              wrote on last edited by
              #11

              @mrjj I 'm going to take a look to your link. Is it a database or you want me to send my code there?

              mrjjM 1 Reply Last reply
              0
              • A aawawa

                @mrjj I 'm going to take a look to your link. Is it a database or you want me to send my code there?

                mrjjM Offline
                mrjjM Offline
                mrjj
                Lifetime Qt Champion
                wrote on last edited by
                #12

                @aawawa
                Hi
                Its a code browser. it makes it really easy to see what is being used. all call to functions are links and
                its almost as good as the debugger. at least to see what is going on.
                I was thinking you would go and look how it deletes the series or something like that.
                The sample is for Christian-Ehrlicher as he might make it into a bug report if we can
                reproduce it and find no good reason for not release the mem on RemoveAllSeries.

                1 Reply Last reply
                1
                • Christian EhrlicherC Offline
                  Christian EhrlicherC Offline
                  Christian Ehrlicher
                  Lifetime Qt Champion
                  wrote on last edited by
                  #13

                  I can see some kind of 'leak' but need to do some more investigations.

                  Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                  Visit the Qt Academy at https://academy.qt.io/catalog

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                  • Christian EhrlicherC Offline
                    Christian EhrlicherC Offline
                    Christian Ehrlicher
                    Lifetime Qt Champion
                    wrote on last edited by
                    #14

                    Ok, no leak there. Just a lot of data. You're creating 100000 QLineSeries with 10000 each - this will need some memory and time. I would rather try to add the points to one QLineSeries.

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                    • A Offline
                      A Offline
                      aawawa
                      wrote on last edited by
                      #15

                      @Christian-Ehrlicher thank you... But it is supposed to be deleted 100000 times in my case no when I use RemoveAllSeries no?

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                      • A Offline
                        A Offline
                        aawawa
                        wrote on last edited by
                        #16

                        @Christian-Ehrlicher would rather try to add the points to one QLineSeries this strategy works quiet well.
                        By changing y program as this for the header :

                        class MyChartView:public QChartView
                        {
                        public:
                        	MyChartView();
                        	~MyChartView();
                        	void Draw(void);
                        
                        private:	
                        	QLineSeries *mSeries;
                        };
                        

                        and for the .cpp

                        MyChartView::MyChartView()
                        {
                        
                        	mSeries = new QLineSeries;
                        	chart()->addSeries(mSeries);
                        
                        }
                        
                        
                        MyChartView::~MyChartView()
                        {
                        }
                        
                        void MyChartView::Draw(void)
                        {
                        	int Length = 1000;
                        	mSeries->clear();
                        	for (int i = 0; i < Length; i++)
                        	{
                        		mSeries->append(QPoint (i, sin(2 * i*3.141516*0.1)));
                        	}
                        	//update();
                        
                        }
                        
                        

                        It seems (I have to confirm this point later) to not have anymore memory leak

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                        • Christian EhrlicherC Offline
                          Christian EhrlicherC Offline
                          Christian Ehrlicher
                          Lifetime Qt Champion
                          wrote on last edited by
                          #17

                          @aawawa said in Memoy leak using QtCharts:

                          But it is supposed to be deleted 100000 times in my case no when I use RemoveAllSeries no?

                          You're right. I think I found the culprit:

                          qlineseries.cpp:112
                          
                          QLineSeries::QLineSeries(QObject *parent)
                              : QXYSeries(*new QLineSeriesPrivate(this), parent)
                          

                          this is never deleted... :/

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                          JonBJ 1 Reply Last reply
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                          • Christian EhrlicherC Christian Ehrlicher

                            @aawawa said in Memoy leak using QtCharts:

                            But it is supposed to be deleted 100000 times in my case no when I use RemoveAllSeries no?

                            You're right. I think I found the culprit:

                            qlineseries.cpp:112
                            
                            QLineSeries::QLineSeries(QObject *parent)
                                : QXYSeries(*new QLineSeriesPrivate(this), parent)
                            

                            this is never deleted... :/

                            JonBJ Offline
                            JonBJ Offline
                            JonB
                            wrote on last edited by
                            #18

                            @Christian-Ehrlicher
                            I think this is the second time I've seen that *new cause this. When will people decide that C++ is getting too clever for its boots? ;-)

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                            • SGaistS Offline
                              SGaistS Offline
                              SGaist
                              Lifetime Qt Champion
                              wrote on last edited by SGaist
                              #19

                              Hi,

                              @Christian-Ehrlicher said in Memoy leak using QtCharts:

                              QLineSeriesPrivate

                              It's QObject based, so when the QXYSeries object is deleted it should also get deleted.

                              It's indeed QObject based but stored in a QScopedPointer so it will automatically get delete on object's destruction.

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                              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                              • A Offline
                                A Offline
                                aawawa
                                wrote on last edited by
                                #20

                                @Christian-Ehrlicher Thank you. It's the first time I see *new in c++ what does it mean?

                                mrjjM 1 Reply Last reply
                                0
                                • A aawawa

                                  @Christian-Ehrlicher Thank you. It's the first time I see *new in c++ what does it mean?

                                  mrjjM Offline
                                  mrjjM Offline
                                  mrjj
                                  Lifetime Qt Champion
                                  wrote on last edited by
                                  #21

                                  @aawawa
                                  Hi
                                  Its a Dereference
                                  http://www.cplusplus.com/doc/tutorial/pointers/
                                  See section Dereference operator (*)

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                                  • A Offline
                                    A Offline
                                    aawawa
                                    wrote on last edited by
                                    #22

                                    @mrjj yes... I understand... But I don't understand the location of the asterix (*). I am used for example to write

                                    int *a = new int;
                                    

                                    what does

                                    *new int
                                    

                                    means?

                                    mrjjM 1 Reply Last reply
                                    0
                                    • A aawawa

                                      @mrjj yes... I understand... But I don't understand the location of the asterix (*). I am used for example to write

                                      int *a = new int;
                                      

                                      what does

                                      *new int
                                      

                                      means?

                                      mrjjM Offline
                                      mrjjM Offline
                                      mrjj
                                      Lifetime Qt Champion
                                      wrote on last edited by mrjj
                                      #23

                                      @aawawa
                                      Means
                                      value pointed to by ptr
                                      The actual value.

                                      int copy = *SomeIntPtr;
                                      that will copy the value to the copy var.
                                      if you did
                                      int copy = SomeIntPtr;
                                      you get the address of pointer into copy

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                                      • Christian EhrlicherC Offline
                                        Christian EhrlicherC Offline
                                        Christian Ehrlicher
                                        Lifetime Qt Champion
                                        wrote on last edited by
                                        #24

                                        Ok, no memleak at all. You testcase is wrong / inaccurate.
                                        The problem with your testcase is that your eventloop is not (yet) running and that you also call it in an loop without a chance for the eventloop to do it's work. Since the internals of QLineSeries is cleaned up with a deferred delete it is not cleaned up until the eventloop is called (and after app.exec()). That's also the reason I thought the dtor is not called at all.

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                                        • J Offline
                                          J Offline
                                          JosuGZ
                                          wrote on last edited by JosuGZ
                                          #25

                                          @Christian-Ehrlicher said in Memoy leak using QtCharts:

                                          Ok, no memleak at all. You testcase is wrong / inaccurate.
                                          The problem with your testcase is that your eventloop is not (yet) running and that you also call it in an loop without a chance for the eventloop to do it's work. Since the internals of QLineSeries is cleaned up with a deferred delete it is not cleaned up until the eventloop is called (and after app.exec()). That's also the reason I thought the dtor is not called at all.

                                          It seems to me that there are some memory leaks happening here.

                                          This code increases memory usage continuously:

                                          aSeries->remove(aSeries->points().size() - 1);
                                          aSeries->append(timestamp, mean);

                                          Bit this one does not:

                                          aSeries->replace(aSeries->points().size() - 1, timestamp, mean);

                                          I'm using Qt 5.11.2.

                                          JonBJ J.HilkJ 2 Replies Last reply
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