Strange behavior of return statement

[Raadush]

Hi, I have this code:

void MyClass::MyMethod()
{
     message->setWindowTitle("Error");
     message->setText("foo");
     message->setInformativeText("bar");
     message->setIcon(QMessageBox::Critical);
     message->setStandardButtons(QMessageBox::Yes | QMessageBox::No);
     ret = message->exec();
 
     if(ret == QMessageBox::No)
     {
          suggestAction->setEnabled(true);
          solutions += "baz";
          this->suggestSolutions();
          return;
     }
 
     message->setWindowTitle("Title");
     message->setText("Message");
     message->setIcon(QMessageBox::Critical);
     message->setStandardButtons(QMessageBox::Ok);
     message->exec();
     this->MyMethod();
 
     treeClicked(navigator->currentItem());
}

void MyClass::MyMethod()
{
     message->setWindowTitle("Error");
     message->setText("foo");
     message->setInformativeText("bar");
     message->setIcon(QMessageBox::Critical);
     message->setStandardButtons(QMessageBox::Yes | QMessageBox::No);
     ret = message->exec();

     if(ret == QMessageBox::No)
     {
          suggestAction->setEnabled(true);
          solutions += "baz";
          this->suggestSolutions();
          return;
     }

     message->setWindowTitle("Title");
     message->setText("Message");
     message->setIcon(QMessageBox::Critical);
     message->setStandardButtons(QMessageBox::Ok);
     message->exec();
     this->MyMethod();

     treeClicked(navigator->currentItem());
}

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Problem is, that when I debug this and I press No, application jumps from line 15 on line 26 as expected, but then it jumps onto line 25, then again on 26, on 25 once more, then again on 26 and then out of MyMethod. Any suggestion why?

[sonulohani]

I didnt understand your problem, share the code.

[Santosh Reddy]

look at the disassembly you will get more insight

[d_stranz]

Any suggestion why?

Your code makes no sense. In the first half of MyMethod() (up to line 16), you're setting the parameters for a QMessageBox dialog of some sort, then posting it with exec().

If you click something other than "No" (like "Yes" maybe), then from line 18 onwards, you set up the message box parameters *again*, exec() the message box *again*, and then recursively call the same MyMethod(), which then posts the message box, and so on..

So what you are probably seeing is the result of unwinding the stack after two passes through the same code, because you've gone into MyMethod() at least twice.

If your poor user clicked Yes every time, he'd never get out of the recursion. Click Yes, click OK, click Yes again, click OK again, click Yes again, click OK again, until finally he's going to kill the process, uninstall your app and ask for his money back.

[amleto]

d_stranz has it.

[Raadush]

Ok, sorry for posting only that part of a code which is executed during one pass through MyMethod which is making problems. Whole MyMethod logic is:

void MyClass::MyMethod()
{
    verifyPIN(); //user promted to enter PIN here
    if(verification was successfull)                 
    {
        do some atcions
    } else if(verification was unsuccessfull)
    {
        if(PIN was locked)
        {
            message->setWindowTitle("Error");
            message->setText("PIN was locked");
            message->setInformativeText("Do you wand to unblock PIN?");
            message->setIcon(QMessageBox::Critical);
            message->setStandardButtons(QMessageBox::Yes | QMessageBox::No);
            ret = message->exec();
 
            if(ret == QMessageBox::Yes) unblockPIN();
            if(ret == QMessageBox::No)
            {
                 suggestAction->setEnabled(true);
                 solutions += "baz";
                 this->suggestSolutions();
            }
            return;
        }
 
        message->setWindowTitle("Title");
        message->setText("Wrong PIN");
        message->setIcon(QMessageBox::Critical);
        message->setStandardButtons(QMessageBox::Ok);
        message->exec();
        this->MyMethod();
    }
    treeClicked(navigator->currentItem());
}

void MyClass::MyMethod()
{
    verifyPIN(); //user promted to enter PIN here
    if(verification was successfull)                 
    {
        do some atcions
    } else if(verification was unsuccessfull)
    {
        if(PIN was locked)
        {
            message->setWindowTitle("Error");
            message->setText("PIN was locked");
            message->setInformativeText("Do you wand to unblock PIN?");
            message->setIcon(QMessageBox::Critical);
            message->setStandardButtons(QMessageBox::Yes | QMessageBox::No);
            ret = message->exec();
 
            if(ret == QMessageBox::Yes) unblockPIN();
            if(ret == QMessageBox::No)
            {
                 suggestAction->setEnabled(true);
                 solutions += "baz";
                 this->suggestSolutions();
            }
            return;
        }
 
        message->setWindowTitle("Title");
        message->setText("Wrong PIN");
        message->setIcon(QMessageBox::Critical);
        message->setStandardButtons(QMessageBox::Ok);
        message->exec();
        this->MyMethod();
    }
    treeClicked(navigator->currentItem());
}

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[Lesiok]

Line 33 : MyMethod calls itself. This leads to a stack overflow.

[Raadush]

No, it does not. MyMethod calls itself only in case wrong PIN was entered and only limited times (3 times in most cases). After that, the pin is blocked and return statement is executed.

[wysota]

... and then you get a cascade of returns, which is what you observe.