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The program crashes suddenly when working with a new feature

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  • tomyT tomy

    @JonB

    I don't know, but:

    • ++i; QTableWidget::setItem(i, j, item);: How many rows does your QTableWidget start with? Do you need to call https://doc.qt.io/qt-5/qtablewidget.html#setRowCount to increase it before you try to setItem() in the new row at the end?

    QTableWidget::setItem(i, j, item); sets the item (which is a double number, the sum of numbers) into the cell with row and column numbers i, j. The numbers i, j have been previously set by the position function, void position(QList<QTableWidgetItem *>, int&, int&). That function gives i the last row number:

    QTableWidgetItem* last = items.last();
           i = last->row();
    

    Then we increase it, ++i;, to refer to the next (blank) cell where we want to put the result of the sum into.

    Is there still any ambiguity about this section please?

    • somethingChanged();: What does this do, does it have any relevant side-effects?

    It's somethingChanged(). I mentioned the name of the book and chapters and thought every Qt programmer has (read) that book.
    If needed, please tell me and then I upload the project for further scrutiny.

    void Spreadsheet::somethingChanged()
    {
        if(autoRecalc)
            recalculate();
        emit modified();
    }
    
    • If you know how to use the debugger for MinGW, you will get more information about exactly where/why the crash is happening if you let it "crash" while inside the debugger?

    Months ago, when I for the first time was manipulating this project, I became a little familiar running the project by Debugger. But after a huge gap that I recently came back to Qt, I don't know much of that.
    I just looked at the Debub menu which is grayed out. I think I should put some breakpoints to be able to run the code by Debugger in order to be able to see the "crash" while inside the debugger. right?

    Is pressing F5 enough?

    JonBJ Offline
    JonBJ Offline
    JonB
    wrote on last edited by
    #6

    @tomy said in The program crashes suddenly when working with a new feature:

    Then we increase it, ++i;, to refer to the next (blank) cell where we want to put the result of the sum into.

    Incrementing i means you are now referring to the next row. How do you/we know whether there is a next row in your QTableWidget? I gave you a reference to QTableWidget::setRowCount(), which I said you may need to call to increase how many rows there are, I don't know.

    Meanwhile, as I & the others have said, if you can use the debugger it may be the quickest way to get to whatever your problem is.

    tomyT 1 Reply Last reply
    0
    • JonBJ JonB

      @tomy said in The program crashes suddenly when working with a new feature:

      Then we increase it, ++i;, to refer to the next (blank) cell where we want to put the result of the sum into.

      Incrementing i means you are now referring to the next row. How do you/we know whether there is a next row in your QTableWidget? I gave you a reference to QTableWidget::setRowCount(), which I said you may need to call to increase how many rows there are, I don't know.

      Meanwhile, as I & the others have said, if you can use the debugger it may be the quickest way to get to whatever your problem is.

      tomyT Offline
      tomyT Offline
      tomy
      wrote on last edited by
      #7

      @JonB
      There are 1000 rows in each sheet while I'm working on the rows number 1 to 30 utmost. Yes, it would be better to use that function you sent, but it's not improving the code for those rows. I will make use of that afterwards. so thanks.

      1 Reply Last reply
      0
      • VRoninV VRonin

        Just run using the debugger, crash your program and look at the stack trace window

        tomyT Offline
        tomyT Offline
        tomy
        wrote on last edited by
        #8

        @VRonin

        It's more than 20 times I'm testing the program after running it by F5. But extremely astonishing, the program doesn't crash!!!! I changed nothing in the code.

        I should dedicate more time and hopefully see it crash. But, where is the window called "stack trace window", please?

        0_1551787511732_Capture.PNG

        VRoninV 1 Reply Last reply
        0
        • tomyT tomy

          @VRonin

          It's more than 20 times I'm testing the program after running it by F5. But extremely astonishing, the program doesn't crash!!!! I changed nothing in the code.

          I should dedicate more time and hopefully see it crash. But, where is the window called "stack trace window", please?

          0_1551787511732_Capture.PNG

          VRoninV Offline
          VRoninV Offline
          VRonin
          wrote on last edited by
          #9

          @tomy said in The program crashes suddenly when working with a new feature:

          where is the window called "stack trace window", please?

          It's the one in the bottom right corner

          "La mort n'est rien, mais vivre vaincu et sans gloire, c'est mourir tous les jours"
          ~Napoleon Bonaparte

          On a crusade to banish setIndexWidget() from the holy land of Qt

          1 Reply Last reply
          3
          • tomyT Offline
            tomyT Offline
            tomy
            wrote on last edited by
            #10

            I ran the program with Debugger (F5) and tested it for crash many a time, but thus far it's never crashed in this mode. But when I run it by crtl+R, it crashes at the second or third time I apply the sum action on the highlighted cells!
            Why please? Does the debugger change the behavior of the program, please?

            Here is the project spreadsheet.rar. Please if possible test it and let me know what makes the program crash, please?
            I wanted to upload it here but faced a message saying I haven't that privilege! so posted that below:
            https://www.dropbox.com/s/anuk091qr8tjeem/spreadsheet.rar?dl=0

            1 Reply Last reply
            0
            • SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #11

              Hi,

              Check for uninitialised pointers and/or variables. In debug mode, the pointers at least are initialised to zero but not in release mode (that's nothing Qt specific though)

              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
              2
              • tomyT Offline
                tomyT Offline
                tomy
                wrote on last edited by tomy
                #12

                I changed the initial value of some pointers from 0 to nullptr and also assigned 0 to some uninitialized variables too ( E.g., quint16) then reran the project and tested for the crash. This time I got this message at the time of crash:

                12:53:28: Starting C:\Users\Abbasi\Desktop\Documents\Qt\qt-book\chap03\build-spreadsheet-Desktop_Qt_5_12_0_MinGW_64_bit-Debug\debug\spreadsheet.exe...
                ASSERT: "size == 0 || offset < 0 || size_t(offset) >= sizeof(QArrayData)" in file..\..\include/QtCore/../../src/corelib/tools/qarraydata.h, line 67
                12:53:50: The program has unexpectedly finished.
                12:53:50: The process was ended forcefully.
                12:53:51: C:/Users/Abbasi/Desktop/Documents/Qt/qt-book/chap03/build-spreadsheet-Desktop_Qt_5_12_0_MinGW_64_bit-Debug/debug/spreadsheet.exe crashed.

                And when I clicked on that file I got this message:

                0_1552123884284_Capture.PNG

                By the way, I always run the programs in the Debug mode unless they're in their last state before creating an installer for them. So all crashes have happened in the Debug mode so far.

                And still by the Debugger, I get no crashes!!

                1 Reply Last reply
                0
                • Christian EhrlicherC Offline
                  Christian EhrlicherC Offline
                  Christian Ehrlicher
                  Lifetime Qt Champion
                  wrote on last edited by
                  #13

                  You're hitting an assertion because you are accesing a QVector/QList with an index which is out-of-bounds. Take a look at the backtrace to see from where the call is coming.

                  So all crashes have happened in the Debug mode so far. And still by the Debugger, I get no crashes!!

                  This somehow makes no sense from me - either it crashes in debug or not.

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

                  J.HilkJ tomyT 2 Replies Last reply
                  2
                  • Christian EhrlicherC Christian Ehrlicher

                    You're hitting an assertion because you are accesing a QVector/QList with an index which is out-of-bounds. Take a look at the backtrace to see from where the call is coming.

                    So all crashes have happened in the Debug mode so far. And still by the Debugger, I get no crashes!!

                    This somehow makes no sense from me - either it crashes in debug or not.

                    J.HilkJ Offline
                    J.HilkJ Offline
                    J.Hilk
                    Moderators
                    wrote on last edited by
                    #14

                    @Christian-Ehrlicher
                    as far as i unerstand it, it‘s always a debug build but only crashes, when rhe debugger is not attached.

                    which is unusual.

                    You could potentially try attaching the debugger after wards to the running process via VS.


                    Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                    Q: What's that?
                    A: It's blue light.
                    Q: What does it do?
                    A: It turns blue.

                    1 Reply Last reply
                    1
                    • Christian EhrlicherC Offline
                      Christian EhrlicherC Offline
                      Christian Ehrlicher
                      Lifetime Qt Champion
                      wrote on last edited by
                      #15

                      Since it's an assertion it will also happen when a debugger is attached. And that's also the reason why it does 'work' in release mode.

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

                      1 Reply Last reply
                      0
                      • Christian EhrlicherC Christian Ehrlicher

                        You're hitting an assertion because you are accesing a QVector/QList with an index which is out-of-bounds. Take a look at the backtrace to see from where the call is coming.

                        So all crashes have happened in the Debug mode so far. And still by the Debugger, I get no crashes!!

                        This somehow makes no sense from me - either it crashes in debug or not.

                        tomyT Offline
                        tomyT Offline
                        tomy
                        wrote on last edited by tomy
                        #16

                        @Christian-Ehrlicher

                        Take a look at the backtrace to see from where the call is coming.

                        As I said, when run by the Debugger, the project never crashes, at least based on my many tests' result!

                        This somehow makes no sense from me - either it crashes in debug or not.

                        I don't use the Release mode, so please let's drop this word down for the time being.

                        I run the program only in the Debug mode, either by pressing F5 (which is the Debugger) or ctrl+R (which is a rormal run).

                        • When run normally: Crash occurs.
                        • when run by the Debugger: Crash doesn't occur.

                        Why don't you simply download and run the project, please?

                        1 Reply Last reply
                        0
                        • Christian EhrlicherC Offline
                          Christian EhrlicherC Offline
                          Christian Ehrlicher
                          Lifetime Qt Champion
                          wrote on last edited by
                          #17

                          @tomy said in The program crashes suddenly when working with a new feature:

                          QTableWidgetItem* item = new QTableWidgetItem;

                          This is wrong, you have to use 'Cell' ...

                          Cell *Spreadsheet::cell(int row, int column) const
                          {
                              return static_cast<Cell *>(item(row, column));
                          }
                          

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

                          tomyT 1 Reply Last reply
                          3
                          • Christian EhrlicherC Christian Ehrlicher

                            @tomy said in The program crashes suddenly when working with a new feature:

                            QTableWidgetItem* item = new QTableWidgetItem;

                            This is wrong, you have to use 'Cell' ...

                            Cell *Spreadsheet::cell(int row, int column) const
                            {
                                return static_cast<Cell *>(item(row, column));
                            }
                            
                            tomyT Offline
                            tomyT Offline
                            tomy
                            wrote on last edited by tomy
                            #18

                            @Christian-Ehrlicher

                            Do you mean I use sum() this way:

                            void Spreadsheet::sum()
                            {
                                double d = 0.0;
                            
                                QList<QTableWidgetItem *> items = selectedItems();
                            
                                if(add(items, d)) {
                                    int row = 0, column = 0;
                                    position(items, row, column);
                            
                                    ++row;
                                    Cell *c = cell(row, column);
                                    c->setTextAlignment(Qt::AlignRight);
                                    c->setText((QString::number(d)));
                            
                                    somethingChanged();
                                }
                            }
                            

                            It still crashes.

                            1 Reply Last reply
                            0
                            • Christian EhrlicherC Offline
                              Christian EhrlicherC Offline
                              Christian Ehrlicher
                              Lifetime Qt Champion
                              wrote on last edited by
                              #19

                              @tomy said in The program crashes suddenly when working with a new feature:

                              It still crashes.

                              But this time your debugger will show you where...

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

                              tomyT 1 Reply Last reply
                              3
                              • Christian EhrlicherC Christian Ehrlicher

                                @tomy said in The program crashes suddenly when working with a new feature:

                                It still crashes.

                                But this time your debugger will show you where...

                                tomyT Offline
                                tomyT Offline
                                tomy
                                wrote on last edited by
                                #20

                                @Christian-Ehrlicher
                                Right!

                                0_1552139876140_4.PNG ![0_1552139887443_5.PNG]

                                1 Reply Last reply
                                0
                                • Christian EhrlicherC Offline
                                  Christian EhrlicherC Offline
                                  Christian Ehrlicher
                                  Lifetime Qt Champion
                                  wrote on last edited by
                                  #21

                                  So when you go up the backtrace you see that "Cell *c = cell(row, column);" returns a nullptr.

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

                                  tomyT 1 Reply Last reply
                                  2
                                  • Christian EhrlicherC Christian Ehrlicher

                                    So when you go up the backtrace you see that "Cell *c = cell(row, column);" returns a nullptr.

                                    tomyT Offline
                                    tomyT Offline
                                    tomy
                                    wrote on last edited by
                                    #22

                                    @Christian-Ehrlicher

                                    So when you go up the backtrace you see that "Cell *c = cell(row, column);" returns a nullptr.

                                    Since it's empty, yeah?

                                    So how to get to the next row (which may or may not be empty) to set the result into it, please?

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                                    0
                                    • Christian EhrlicherC Offline
                                      Christian EhrlicherC Offline
                                      Christian Ehrlicher
                                      Lifetime Qt Champion
                                      wrote on last edited by
                                      #23

                                      When there is no object (yet) you should create one, or?

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

                                      tomyT 2 Replies Last reply
                                      0
                                      • Christian EhrlicherC Christian Ehrlicher

                                        When there is no object (yet) you should create one, or?

                                        tomyT Offline
                                        tomyT Offline
                                        tomy
                                        wrote on last edited by tomy
                                        #24

                                        @Christian-Ehrlicher
                                        I was doing it by:

                                        QTableWidgetItem* item = new QTableWidgetItem;

                                        I don't know why we need: Cell *c = cell(row, column); while it's the last filled cell and we can't increase its row number to get to the next cell to put the result of sum() into it!

                                        1 Reply Last reply
                                        0
                                        • Christian EhrlicherC Offline
                                          Christian EhrlicherC Offline
                                          Christian Ehrlicher
                                          Lifetime Qt Champion
                                          wrote on last edited by
                                          #25

                                          I already told you that you don't have to use QTableWidgetItem but Cell since the model is working with Cell objects (which derives from QTableWidgetItem) instead QTableWidgetItem and therefore the static cast does undefined stuff -> c++ basics...

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

                                          1 Reply Last reply
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