Segmentation fault when trying to add GroupBox to mainLayout

[imperator]

Hi

I get an segmentation fault when running a program I'm working on. From a button in a application based on QMainWindow, I open a new dialog to create a new activity. In the dialog I want to group the layout in group boxes.

// This is the constructor of the dialog
NewEvent::NewEvent(QWidget* parent) : QDialog(parent){
 
	void createHorizontalGroupBox();
 
	QVBoxLayout* mainLayout = new QVBoxLayout(this);
 
	mainLayout->addWidget(horizontalGroupBox);
 
	setLayout(mainLayout);
 
        ...
}
 
void NewEvent::createHorizontalGroupBox(){
     // horizontalGroupBox is declared in the h-file
	horizontalGroupBox = new QGroupBox(tr("Some text"));
	QHBoxLayout* layout = new QHBoxLayout;
 
	QLabel* actLabel = new QLabel(tr("Some text"));
	QLineEdit* actType = new QLineEdit;
 
	layout->addWidget(actLabel);
	layout->addWidget(actType);
 
	horizontalGroupBox->setLayout(layout);
}

// This is the constructor of the dialog
NewEvent::NewEvent(QWidget* parent) : QDialog(parent){

	void createHorizontalGroupBox();

	QVBoxLayout* mainLayout = new QVBoxLayout(this);

	mainLayout->addWidget(horizontalGroupBox);

	setLayout(mainLayout);

        ...
}

void NewEvent::createHorizontalGroupBox(){
     // horizontalGroupBox is declared in the h-file
	horizontalGroupBox = new QGroupBox(tr("Some text"));
	QHBoxLayout* layout = new QHBoxLayout;

	QLabel* actLabel = new QLabel(tr("Some text"));
	QLineEdit* actType = new QLineEdit;

	layout->addWidget(actLabel);
	layout->addWidget(actType);

	horizontalGroupBox->setLayout(layout);
}

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What happens is that when I click the button in the application the program quits and the "segmentation fault" is returned to the terminal.

If I remove/comment the mainLayout->addWidget(horizontalGroupBox); line, the program works the way I want.

What could this be down to?

Regards,

André

[high_flyer]

Are you sure the code you posted compiles?

NewEvent::NewEvent(QWidget* parent) : QDialog(parent){
 
    void createHorizontalGroupBox(); //<<<--- this compiles?
 
    QVBoxLayout* mainLayout = new QVBoxLayout(this);
 
    mainLayout->addWidget(horizontalGroupBox);
 
    setLayout(mainLayout);
 
        ...
}

NewEvent::NewEvent(QWidget* parent) : QDialog(parent){
 
    void createHorizontalGroupBox(); //<<<--- this compiles?
 
    QVBoxLayout* mainLayout = new QVBoxLayout(this);
 
    mainLayout->addWidget(horizontalGroupBox);
 
    setLayout(mainLayout);
 
        ...
}

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[imperator]

Yes, it does compile.

It's similar to the layout example in the docs (search for Basic Layouts Example).

The function is declared as a private function in the h-file.

[rknowles]

Compare the example and your code again. It looks like the problem is just what high_flyer points out. Your code says:

void createHorizontalGroupBox();

void createHorizontalGroupBox();

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while this is more like the example:

createHorizontalGroupBox();

createHorizontalGroupBox();

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Your code declares a new local method. It never defines it and never calls it. Without "void" you actually call the defined method, which creates "horizontalGroupBox", which allows

mainLayout->addWidget(horizontalGroupBox);

mainLayout->addWidget(horizontalGroupBox);

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to run with a good rather than NULL pointer.

[imperator]

Oh my

I did not notice before now. It did compile, but I can see why I got the segmentation fault.

After correction it works just fine.

Thanks for the replies. I'm off having my eyes checked.

André

[disokika]

I accept with code:
void NewEvent::createHorizontalGroupBox()
{
// horizontalGroupBox is declared in the h-file
horizontalGroupBox = new QGroupBox(tr("hello all"));
QHBoxLayout* layout = new QHBoxLayout;

QLabel* actLabel = new QLabel(tr("I love you"));
QLineEdit* actType = new QLineEdit;

layout->addWidget(actLabel);
layout->addWidget(actType);

horizontalGroupBox->setLayout(layout);
}