Program crashes (SIGSEGV)

[Voldemort]

Hello,

My program crashes sometimes (SIGSEGV - Segmentation fault). This is (a part of) the code:

This shows the error message when the connection with the server was broken or stopped.

void Window_Login_Busy::show_errors(int sort_error)
{
    close();
    window_login->show();
    progressbar->setValue(0);
 
    QString text = "Aanmelden mislukt";
    if(sort_error == 1)
        text += ": Disconnected from server.";
    else if (sort_error == 2)
        text += ": Gebruikersnaam of wachtwoord is fout.";
 
    QMessageBox err;
    err.setIcon(QMessageBox::Warning);
    err.setWindowTitle("QQMsn: Error");
    err.setText(text);
    err.exec();
 
    //debug->setData("bla");
}

void Window_Login_Busy::show_errors(int sort_error)
{
    close();
    window_login->show();
    progressbar->setValue(0);

    QString text = "Aanmelden mislukt";
    if(sort_error == 1)
        text += ": Disconnected from server.";
    else if (sort_error == 2)
        text += ": Gebruikersnaam of wachtwoord is fout.";

    QMessageBox err;
    err.setIcon(QMessageBox::Warning);
    err.setWindowTitle("QQMsn: Error");
    err.setText(text);
    err.exec();

    //debug->setData("bla");
}

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and

Here someone entered the wrong password, I break the connection with the server.

while(ssl_sck_dalogin->canReadLine())
    {
        [...]
        else if(line.contains("HTTP/1.1 302 FOUND"))
        {
            debug->setData("Redirect");
 
            break;
        }
                [...]
    }

while(ssl_sck_dalogin->canReadLine())
    {
        [...]
        else if(line.contains("HTTP/1.1 302 FOUND"))
        {
            debug->setData("Redirect");

            break;
        }
                [...]
    }

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and

This is the emited slot when I close the connection, it uses the standard Qt signal:

connect(socket, SIGNAL(disconnected()), SLOT(isDisconnected()));

login_busy->show_errors(1); is the function in the first code I posted.

void cmsn::isDisconnected()
{
    debug->setData("\nDisconnected from host (Notification server).");
 
    if(login_busy->change_lbl)
        login_busy->show_errors(1);
}

void cmsn::isDisconnected()
{
    debug->setData("\nDisconnected from host (Notification server).");

    if(login_busy->change_lbl)
        login_busy->show_errors(1);
}

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When someone enters the wrong password, I get an error dialog with an Ok button, the login screen is showed and the login_busy is closed. But when you close that screen or press the Ok button, the program receives the SIGSEGV signal and crashes.

gdb says:

`/home/quinten/QQMsn_build/QQMsn' has changed; re-reading symbols.
Starting program: /home/quinten/QQMsn_build/QQMsn
Failed to read a valid object file image from memory.
[Thread debugging using libthread_db enabled]
[New Thread -1223088432 (LWP 4881)]
[New Thread -1225602160 (LWP 4882)]

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1223088432 (LWP 4881)]

When I don't show an MessageBox, the program does not crash and gdb says:

Starting program: /home/quinten/QQMsn_build/QQMsn
Failed to read a valid object file image from memory.
[Thread debugging using libthread_db enabled]
[New Thread -1222646064 (LWP 4927)]
[New Thread -1225159792 (LWP 4928)]
[Thread -1225159792 (LWP 4928) exited]

Program exited normally.

There are some cases where the server closes the connection (e.g. entering a wrong username). In that case, the same slot is emited, the
MessageBox shows, and when pressing OK, the MessageBox closes and the program doesn't crash.


Why does my program crash? How can I solve it? I don't understand where the error is, in my ssl class, in my window_login class, in Qt, in OpenSSL or somewhere else? When you need the whole source code, I'll post it.