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ASSERT failure in QList<T>::operator[]: "index out of range"

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  • JerwinprabuJ Jerwinprabu

    If I sent start command from server, output displayed like this on client side

    WebSocket connected
    message received : "straight|xy|3|0" 
    
    start xy value Received from server : "straight|xy|3|0"
    start x value emitted to Robot : 3
    start y value emitted to Robot: 0
    int of start x value emitted : 3
    int start y value emitted : 0
    

    If I click start button on client side that time only I got the error.

    WebSocket connected
    
    start xy value Received from server : ""
    ASSERT failure in QList<T>::operator[]: "index out of range", file /usr/include/arm-linux-gnueabihf/qt5/QtCore/qlist.h, line 487
    
    jsulmJ Offline
    jsulmJ Offline
    jsulm
    Lifetime Qt Champion
    wrote on last edited by jsulm
    #6

    @Jerwinprabu You see: you're trying to split an empty string, this is not going to work. So please add some check to your code as @joeQ suggested.
    And you should check why you don't get what server sent, but this is another issue.

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

    1 Reply Last reply
    3
    • JerwinprabuJ Offline
      JerwinprabuJ Offline
      Jerwinprabu
      wrote on last edited by Jerwinprabu
      #7

      @joeQ When I was try to run the program I got the error

      error: return-statement with a value, in function returning 'void' [-fpermissive]
               return false;
      
      joeQJ jsulmJ 2 Replies Last reply
      0
      • JerwinprabuJ Jerwinprabu

        @joeQ When I was try to run the program I got the error

        error: return-statement with a value, in function returning 'void' [-fpermissive]
                 return false;
        
        joeQJ Offline
        joeQJ Offline
        joeQ
        wrote on last edited by joeQ
        #8

        @Jerwinprabu (⊙o⊙)…

        bool myFunctionName() ///< Notes; function return value type must bool
        {
              /* ... */
              return true;
        }
        

        Just do it!

        1 Reply Last reply
        4
        • JerwinprabuJ Jerwinprabu

          @joeQ When I was try to run the program I got the error

          error: return-statement with a value, in function returning 'void' [-fpermissive]
                   return false;
          
          jsulmJ Offline
          jsulmJ Offline
          jsulm
          Lifetime Qt Champion
          wrote on last edited by
          #9

          @Jerwinprabu @joeQ Or just do

          return;
          

          if you do not use the return value...

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

          1 Reply Last reply
          3
          • JerwinprabuJ Offline
            JerwinprabuJ Offline
            Jerwinprabu
            wrote on last edited by Jerwinprabu
            #10

            @jsulm @joeQ Thanks for your help. Ya @joeQ given proper sample. I have tried that. Here I have posted the solution now client side that is working fine, one time I want to check from server side. Kindly check, if anything wrong awaiting for your further response

            startvaluexy = Client::straightxy;
            qDebug() << "start xy value Received from server :" << startvaluexy;
            QStringList xy = startvaluexy.split("|");
            int xySize = xy.size(); 
            qDebug() << "start xy size :" << xySize;
            
            if(xySize > 4){
                 x = xy[2];
                 y = xy[3];
              }
            
                 QString num1 = x;
                 int x = num1.toInt();
            
                 qDebug() << "start x value  :" << x;
            
                 QString num2 = y;
                 int y = num2.toInt();
            
                 qDebug() << "start y value :" << y;
            
                xstart = x;
                ystart = y;
            

            After checking the size will modify this xySize > 4

            jsulmJ 1 Reply Last reply
            0
            • JerwinprabuJ Jerwinprabu

              @jsulm @joeQ Thanks for your help. Ya @joeQ given proper sample. I have tried that. Here I have posted the solution now client side that is working fine, one time I want to check from server side. Kindly check, if anything wrong awaiting for your further response

              startvaluexy = Client::straightxy;
              qDebug() << "start xy value Received from server :" << startvaluexy;
              QStringList xy = startvaluexy.split("|");
              int xySize = xy.size(); 
              qDebug() << "start xy size :" << xySize;
              
              if(xySize > 4){
                   x = xy[2];
                   y = xy[3];
                }
              
                   QString num1 = x;
                   int x = num1.toInt();
              
                   qDebug() << "start x value  :" << x;
              
                   QString num2 = y;
                   int y = num2.toInt();
              
                   qDebug() << "start y value :" << y;
              
                  xstart = x;
                  ystart = y;
              

              After checking the size will modify this xySize > 4

              jsulmJ Offline
              jsulmJ Offline
              jsulm
              Lifetime Qt Champion
              wrote on last edited by jsulm
              #11

              @Jerwinprabu said in ASSERT failure in QList<T>::operator[]: "index out of range":

              if(xySize > 4){

              shouldn't it be

              if(xySize >= 4){
              

              ?
              And if it is not >= 4 what would be the values of x and y? Shouldn't you just skip processing in this case (do return as @joeQ suggested)?

              What are you trying to do with this

              QString num1 = x;
              int x = num1.toInt();
              

              ?! Why do you assign an integer to a string and then convert this string to integer again? Same for

              QString num2 = y;
              int y = num2.toInt();
              

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

              JerwinprabuJ 1 Reply Last reply
              0
              • jsulmJ jsulm

                @Jerwinprabu said in ASSERT failure in QList<T>::operator[]: "index out of range":

                if(xySize > 4){

                shouldn't it be

                if(xySize >= 4){
                

                ?
                And if it is not >= 4 what would be the values of x and y? Shouldn't you just skip processing in this case (do return as @joeQ suggested)?

                What are you trying to do with this

                QString num1 = x;
                int x = num1.toInt();
                

                ?! Why do you assign an integer to a string and then convert this string to integer again? Same for

                QString num2 = y;
                int y = num2.toInt();
                
                JerwinprabuJ Offline
                JerwinprabuJ Offline
                Jerwinprabu
                wrote on last edited by
                #12

                @jsulm from server I will receive the string then I want to convert that string into int. Again I want to convert for sending to server(for map).

                jsulmJ 1 Reply Last reply
                0
                • JerwinprabuJ Jerwinprabu

                  @jsulm from server I will receive the string then I want to convert that string into int. Again I want to convert for sending to server(for map).

                  jsulmJ Offline
                  jsulmJ Offline
                  jsulm
                  Lifetime Qt Champion
                  wrote on last edited by jsulm
                  #13

                  @Jerwinprabu Then why do you convert it back from string to int? x is already int, what's the point to convert from string to int?
                  Also

                  QString num1 = x;
                  

                  is not a conversion to string from int! It will not even compile. If you want to convert int to string then do it like shown here http://doc.qt.io/qt-5/qstring.html#number

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

                  JerwinprabuJ 1 Reply Last reply
                  0
                  • jsulmJ jsulm

                    @Jerwinprabu Then why do you convert it back from string to int? x is already int, what's the point to convert from string to int?
                    Also

                    QString num1 = x;
                    

                    is not a conversion to string from int! It will not even compile. If you want to convert int to string then do it like shown here http://doc.qt.io/qt-5/qstring.html#number

                    JerwinprabuJ Offline
                    JerwinprabuJ Offline
                    Jerwinprabu
                    wrote on last edited by Jerwinprabu
                    #14

                    @jsulm Because I want to take that value to int only xstart, ystart. I want to convert from string to int only. x, y is not int.

                    QString x;
                    QString y;
                    
                    jsulmJ 2 Replies Last reply
                    0
                    • JerwinprabuJ Jerwinprabu

                      @jsulm Because I want to take that value to int only xstart, ystart. I want to convert from string to int only. x, y is not int.

                      QString x;
                      QString y;
                      
                      jsulmJ Offline
                      jsulmJ Offline
                      jsulm
                      Lifetime Qt Champion
                      wrote on last edited by jsulm
                      #15

                      @Jerwinprabu Again

                      QString num1 = x;
                      int x = num1.toInt();
                      

                      x already contains the integer value! Now you convert it to string then again to int - it will be same as before.

                      int x = 1;
                      QString num1 = QString::number(x);
                      x = num1.toInt();
                      qDebug() << x;
                      

                      What do you think the last line will print out?
                      Shouldn't it be just

                      QString num1 = QString::number(x);
                      xstart = x;
                      

                      ?

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

                      1 Reply Last reply
                      0
                      • JerwinprabuJ Jerwinprabu

                        @jsulm Because I want to take that value to int only xstart, ystart. I want to convert from string to int only. x, y is not int.

                        QString x;
                        QString y;
                        
                        jsulmJ Offline
                        jsulmJ Offline
                        jsulm
                        Lifetime Qt Champion
                        wrote on last edited by
                        #16

                        @Jerwinprabu Also here you redefine the variable x

                        QString num1 = x;
                        int x = num1.toInt();
                        

                        is there a reason why you're doing this?

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

                        1 Reply Last reply
                        0
                        • jsulmJ Offline
                          jsulmJ Offline
                          jsulm
                          Lifetime Qt Champion
                          wrote on last edited by
                          #17

                          After chatting with @Jerwinprabu I realised that I misunderstood his code: x and y are actually QString not int.

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

                          mrjjM 1 Reply Last reply
                          1
                          • jsulmJ jsulm

                            After chatting with @Jerwinprabu I realised that I misunderstood his code: x and y are actually QString not int.

                            mrjjM Offline
                            mrjjM Offline
                            mrjj
                            Lifetime Qt Champion
                            wrote on last edited by
                            #18

                            @jsulm
                            Well x is a pretty confusing name for a string in most cases.
                            I was sure also it was int.

                            1 Reply Last reply
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