QDir::drives() causes crash in windows

mfaghani

I'm using QDir::drives() to make a list of drives in win7. I put the code below in constructor of mainwindow.cpp

QDir dir3;
foreach(QFileInfo item, dir3.drives() )
{
    qDebug() << item.absoluteFilePath();
}

I can see my drives' list in Application Output Window, but the program crashes after that. And it works well when I remove the code above.
The error I get in Application Output Window is "The program has unexpectedly finished."

SGaist

Hi,

What version of Qt are you using ?
Can you provide a stack trace ?
By the way, QDir::drives is a static method.

mfaghani

@SGaist
Thanks. I'm using Qt 5.4.0 and Qt Creator 3.3.0.
I also tryed as static method.

QFileInfoList fil = QDir::drives();
QMessageBox *msg;
qDebug() << fil.count();
msg->setText(QString::number(fil.count()));
msg->exec();

But I've got the same result.
qDebug() shows the number of drives correctly. But program crashes after that. I found that it happens when I use the instance of QFileInfoList (fil).
And sorry for providing a stack trace. I don't how to do that.

SGaist

Qt 5.4.0 is outdated, you should update to a more recent version. Current is Qt 5.11.2 with Qt 5.12 around the corner.

If you need an LTS version current is Qt 5.9.7.

SGaist

For the stack trace, start your application using the debugger.

mrjj

Hi
Might be copy & paste error
QMessageBox *msg; << dangling pointer
msg->setText(QString::number(fil.count())); << crash here

mfaghani

@mrjj said in QDir::drives() causes crash in windows:

msg->setText(QString::number(fil.count())); << crash here

It happens at the line which you mentioned, when I use fil.count().
Sorry I don't understand what you mean of copy and paste error.
In the first code I posted, I didn't use messagebox, I just used foreach loop for QFileInfo.absoluteFilePath() and I don't know if there was a copy and paste error.

SGaist

What @mrjj meant is that you are using an uninitialised pointer hence potentially the crash you see.

mfaghani

@SGaist
Thank you very much,
I modified it to QMessageBox *msg = new QMessageBox(); and every things went well. Anyway, it looks like a stupid mistake and I need to be more careful.
Thanks again