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ASSERT failure in QList<T>::at: "index out of range"

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qlistqstringlistc++qurlqt 5.7
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  • SGaistS Offline
    SGaistS Offline
    SGaist
    Lifetime Qt Champion
    wrote on last edited by
    #4

    Did you also check the value of current ?

    Interested in AI ? www.idiap.ch
    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

    QjayQ 1 Reply Last reply
    2
    • Paul ColbyP Offline
      Paul ColbyP Offline
      Paul Colby
      wrote on last edited by
      #5

      Hi @Qjay

      Where do you initialise dbmanager::current? And, are you re-using the dbmanager instance?

      eg:

      d->doDownload(one_set_of_down_links);
      // later
      d->doDownload(another_set_of_down_links);
      

      In which case you might need to be explicitly resetting dbmanager::current to 0? (and if the second list was smaller than the first, you will get the exception you've shown)

      Cheers.

      1 Reply Last reply
      3
      • QjayQ Offline
        QjayQ Offline
        Qjay
        wrote on last edited by
        #6

        hi @Paul like in my case

         dbmanager *d = new dbmanager(0) ;
            d->doDownload(down_links);
        
            dbmanager *p = new dbmanager(0) ;
            p->png_download(png_down_links, png_hash);
        

        i use
        int current= 0 // for doDownload(down_links)
        png_curr = 0; // for png_download

        here is the whole code of the .cpp file

        https://ghostbin.com/paste/rdfnb

        1 Reply Last reply
        0
        • SGaistS SGaist

          Did you also check the value of current ?

          QjayQ Offline
          QjayQ Offline
          Qjay
          wrote on last edited by
          #7

          @SGaist

          Yes i check the value of current .

          it is in global scope and i have initialized it to 0

          int current = 0 ;

          i have attached the full source code too

          https://ghostbin.com/paste/rdfnb

          and this is how i am calling the add function which calls save image and save file function

             Item{
                          visible: false
                          Text{
                              visible: false
                              id: responsetext
                              text:""
                          }
                      }
          
                      Button{
                          width: drawer.width
                          height: 40
          
                          text:"save offline"
                          onClicked: {
                              responsetext.text = dbman.add(current_title);
                              drawer.close();
          
                          }
                      }
          
          1 Reply Last reply
          0
          • SGaistS Offline
            SGaistS Offline
            SGaist
            Lifetime Qt Champion
            wrote on last edited by
            #8

            Why a global variable ?

            If you have an out of range error this means that current goes higher than the size of the list your are accessing.

            You are likely never reinitializing current. So it will work the first time however the second time, and unless your array gets bigger than current, it will fail.

            Interested in AI ? www.idiap.ch
            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

            1 Reply Last reply
            0
            • Paul ColbyP Offline
              Paul ColbyP Offline
              Paul Colby
              wrote on last edited by
              #9

              @Qjay, how sure are you that the exception happens at this line?

              QUrl url = v.toStringList().at(current);
              

              Did the debugger break at this line?

              The reasons I ask are,

              1. the output in your animated gif suggests (its not definitive) to me that the crash happens just after that point;
              2. its looks very likely to me, that the exception would be on this line:
              png_filename = n.toStringList().at(png_curr);
              

              Because the code in dbmanager::png_download is assuming that n (aka png_hash) always has the same number (or rather, at least as many) items as v (aka png_down_links). But, while I see code that streams entries into png_down_links (in save_images), I see no code anywhere that adds anything to png_hash.

              I highly recommend you try out the debugger (if you haven't already), and also add some range-checking / debug logging in the dbmanager::png_download function.

              Cheers.

              1 Reply Last reply
              1
              • QjayQ Offline
                QjayQ Offline
                Qjay
                wrote on last edited by Qjay
                #10

                @Paul i think you are right . I think my code is messed up ( this code is an older version ) . Yeah i just saw png_hash has nothing to do in whole code !!

                I have updated the code

                https://ghostbin.com/paste/j4meh

                1 Reply Last reply
                0
                • QjayQ Offline
                  QjayQ Offline
                  Qjay
                  wrote on last edited by
                  #11

                  @Paul @SGaist , i don't know why but i am never able to initialize QUrl url :( ;

                  AND I BELIEVE THAT"S WHAT CAUSING THE PROBLEM

                  i have tried different approaches too . Like in my code i was using QStringList i even tried Qvector<QString> down_links and end result was same

                  NOT ABLE TO set QUrl

                  in console screen
                  QUrl("")
                  ""
                  

                  What shoudl i do ?

                  jsulmJ 1 Reply Last reply
                  0
                  • QjayQ Qjay

                    @Paul @SGaist , i don't know why but i am never able to initialize QUrl url :( ;

                    AND I BELIEVE THAT"S WHAT CAUSING THE PROBLEM

                    i have tried different approaches too . Like in my code i was using QStringList i even tried Qvector<QString> down_links and end result was same

                    NOT ABLE TO set QUrl

                    in console screen
                    QUrl("")
                    ""
                    

                    What shoudl i do ?

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

                    @Qjay Can you show the code where you initialize QUrl? From your description we can only guess what could be the problem. Are you sure you don't pass an empty string to QUrl?

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

                    1 Reply Last reply
                    0
                    • QjayQ Offline
                      QjayQ Offline
                      Qjay
                      wrote on last edited by
                      #13

                      @jsulm , i have given the whole code

                      https://ghostbin.com/paste/v4t47

                      by the way this is where i set QUrl

                      line no 371

                       QUrl url = v.toStringList().at(current);
                              qDebug() << "why break" << url;
                      
                      1 Reply Last reply
                      0
                      • SGaistS Offline
                        SGaistS Offline
                        SGaist
                        Lifetime Qt Champion
                        wrote on last edited by
                        #14

                        Again, did you check that the value of current is lower than the size of the string list ?

                        Interested in AI ? www.idiap.ch
                        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                        1 Reply Last reply
                        0
                        • QjayQ Offline
                          QjayQ Offline
                          Qjay
                          wrote on last edited by
                          #15

                          I have initialized current =0; in global scope .

                          jsulmJ 1 Reply Last reply
                          0
                          • QjayQ Qjay

                            I have initialized current =0; in global scope .

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

                            @Qjay But is it changed somewhere?
                            Why not just check like this?

                            qDebug() << v.toStringList().size() << current;
                            qDebug() << v.toStringList().at(current);
                            QUrl url = v.toStringList().at(current);
                            

                            In such a situation this is actually the first thing to do...

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

                            1 Reply Last reply
                            1
                            • QjayQ Offline
                              QjayQ Offline
                              Qjay
                              wrote on last edited by
                              #17

                              hey @jsulm

                              i tried what you suggested

                              qDebug() << v.toStringList().size() << current;
                              qDebug() << v.toStringList().at(current);
                              QUrl url = v.toStringList().at(current);
                              

                              i did this

                              qDebug() << "stringlist size and current" << v.toStringList().size() << current;
                                      qDebug() << "current url in stringlist" << v.toStringList().at(current);
                                      QUrl url = v.toStringList().at(current);
                                      qDebug() << "why break" << url;
                              

                              output

                              stringlist size and current 33 0
                              current url in stringlist   "(http://restbase.wikitolearn.org/en.wikitolearn.org/v1/media/math/render/svg/3cd95482da53d42c5f7f249454f7ee1e85cacc0c)"
                              why break QUrl("")
                              ""
                              

                              and then error

                              ASSERT failure in QList<T>::at: "index out of range", file ../../Qt5.7.0/5.7/gcc_64/include/QtCore/qlist.h, line 537
                              The program has unexpectedly finished.
                              
                              jsulmJ 1 Reply Last reply
                              0
                              • QjayQ Qjay

                                hey @jsulm

                                i tried what you suggested

                                qDebug() << v.toStringList().size() << current;
                                qDebug() << v.toStringList().at(current);
                                QUrl url = v.toStringList().at(current);
                                

                                i did this

                                qDebug() << "stringlist size and current" << v.toStringList().size() << current;
                                        qDebug() << "current url in stringlist" << v.toStringList().at(current);
                                        QUrl url = v.toStringList().at(current);
                                        qDebug() << "why break" << url;
                                

                                output

                                stringlist size and current 33 0
                                current url in stringlist   "(http://restbase.wikitolearn.org/en.wikitolearn.org/v1/media/math/render/svg/3cd95482da53d42c5f7f249454f7ee1e85cacc0c)"
                                why break QUrl("")
                                ""
                                

                                and then error

                                ASSERT failure in QList<T>::at: "index out of range", file ../../Qt5.7.0/5.7/gcc_64/include/QtCore/qlist.h, line 537
                                The program has unexpectedly finished.
                                
                                jsulmJ Offline
                                jsulmJ Offline
                                jsulm
                                Lifetime Qt Champion
                                wrote on last edited by
                                #18

                                @Qjay Why is the URL in parentheses?

                                (http://restbase.wikitolearn.org/en.wikitolearn.org/v1/media/math/render/svg/3cd95482da53d42c5f7f249454f7ee1e85cacc0c)
                                

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

                                1 Reply Last reply
                                0
                                • SGaistS Offline
                                  SGaistS Offline
                                  SGaist
                                  Lifetime Qt Champion
                                  wrote on last edited by
                                  #19

                                  Looks like you are doing a lot of parsing, replacement etc.

                                  The first thing I'd do, is to just ensure that you really have URLs in your list. And get rid of that QVariant parameter. It really doesn't make any sense in your use case.

                                  Interested in AI ? www.idiap.ch
                                  Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                                  1 Reply Last reply
                                  0
                                  • QjayQ Offline
                                    QjayQ Offline
                                    Qjay
                                    wrote on last edited by Qjay
                                    #20

                                    Hello , thanks for the suggetions .

                                    1. yes there were useless ( ) in url . i have removed them . Now i am able to assign url to Qurl :D great!!

                                    2. i removed the Qvariant thing too

                                    now the code is

                                    .cpp : https://ghostbin.com/paste/vv2w7

                                    header file : https://ghostbin.com/paste/8z4y3

                                    but the assert error still exist :/

                                    1 Reply Last reply
                                    0
                                    • SGaistS Offline
                                      SGaistS Offline
                                      SGaist
                                      Lifetime Qt Champion
                                      wrote on last edited by
                                      #21

                                      Still at the same place ?

                                      Interested in AI ? www.idiap.ch
                                      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                                      1 Reply Last reply
                                      0
                                      • QjayQ Offline
                                        QjayQ Offline
                                        Qjay
                                        wrote on last edited by
                                        #22

                                        Hey @SGaist , @jsulm , thank you it's solved now

                                        To be honest i don't know why it worked :/

                                        but below is the code

                                        https://ghostbin.com/paste/528m6

                                        1 Reply Last reply
                                        0
                                        • SGaistS Offline
                                          SGaistS Offline
                                          SGaist
                                          Lifetime Qt Champion
                                          wrote on last edited by
                                          #23

                                          From the looks of it, you're currently lucky.

                                          I'd recommend considering refactoring and cleaning up this code. Maybe a full rewrite would even be better.

                                          Interested in AI ? www.idiap.ch
                                          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                                          1 Reply Last reply
                                          0

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