[SOLVED] QTextEdit + Singleton = Memleak?

Adelost

I am using Qt 4.8.4 and if I make a singleton out of a QMainWindow and assign a QTextEdit, I get a huge memory leak. Any ideas?

@class Window : public QMainWindow
{
Q_OBJECT

private:
Window()
{
QTextEdit* textEdit = new QTextEdit(this);
this->setCentralWidget(textEdit);
textEdit->setPlainText(
"\n"
" INITIALIZING\n"
"\n"
" ~-_ Steamin'\n"
" -~ Hot\n"
" c|| COFFEE\n"
"");
}

public:
static Window* instance()
{
static Window instance;
return &instance;
}
};@

EDIT
Found a way to solve it! If I swap my lazy singleton to an ordinary singleton, things will work out.
@Window* instance()
{
// NOTE: "s_instance" is a static member variable
if(!s_instance)
s_instance = new Window();

return s_instance;
}@

DerManu

How do you know you get a huge memory leak? (Do you mean on termination of your program? Technically that's not a memory leak, more of a moral thing...)

Adelost

I tested it with Qt 5.0.2 as well, same result.

[quote author="DerManu" date="1368224963"](Do you mean on termination of your program?)[/quote] Yes during termination. Still feels quite bad thought.

My main looks like this:
@int main(int argc, char *argv[])
{
// Detect memory leaks
#if defined(DEBUG) | defined(_DEBUG)
_CrtSetDbgFlag( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF );
#endif

// Create window
QApplication a(argc, argv);
Window* w = Window::instance();
w->show();

return a.exec&#40;&#41;;

}@

Haven't counted, but the memleak seems rather huge.
!http://i.imgur.com/gEnd0Tb.png(Memory leak QTextEdit.)!

DerManu

[quote author="Adelost" date="1368225736"]Yes during termination. Still feels quite bad thought.[/quote] Yes, you should feel a little dirty, that's okay.

Just a guess: Delete the singleton memory in a controlled fashion before QApplication goes out of scope. Or try hard to get rid of the singleton, in case you haven't done that yet.

Adelost

QTextEdit really doesn't like singletons it seems. Even if I delete the Widget manually still memleak. Gives me the creeps.
@Window()
{
QTextEdit* textEdit = new QTextEdit();
delete textEdit; // Deletes widget

// Still memleak, hmm...
}@

The only widget affected so far seem to be QTextEdit and QPlainTextEdit, ordinary widgets seems to work fine.

Adelost

Found a way to solve it! If I swap my lazy singleton to an ordinary singleton, things will work out.

@Window* instance()
{
if(!s_instance)
s_instance = new Window();

return s_instance;
}@