Memory problem and strange behaviour

Saroupille

Hi,

I'm quite new with Qt, and I have some issues with my program. Some executions end without any errors, and others don't.

Sometimes, the debug consol print a lot of lines, like there are a memory leak, sometimes the app stop promptly. I don't know why, I started to observ this behaviour after adding a layout on the "preference window".

This is my code :
main.cpp
@
#include <QtWidgets>
#include <QLineEdit>
#include <QToolButton>
#include <MainWindow.h>

int main(int argc, char *argv[]) {
QApplication app(argc, argv);
MainWindow window;
window.show();
return app.exec();
}
@
MainWindow.h
@#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QtWidgets>
#include <QMenu>
#include <QToolBar>
#include <QTabWidget>
#include <QAction>

class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow();
private slots:
void newWindow();
void openPreferencesMenu();
private:
/*
QMenu *fileMenu;
QToolBar *fileToolBar;
QToolBar *editToolBar;
*/
QMenu *fileMenu;
QMenu *editMenu;

QAction *newAct;
QAction *editAct;

};

#endif // MAINWINDOW_H@

PreferenceWindow.h
@#define PREFERENCEWINDOW_H

#include <QtWidgets>

class PreferenceWindow : public QDialog
{
Q_OBJECT
public:
PreferenceWindow();
private:
QLineEdit *programPath;
QLabel *programPathLabel;

QLineEdit *programDefaultOptions;
QLabel * programDefaultOptionsLabel;

QFormLayout *layout;
QPushButton *acceptButton;
QPushButton *cancelButton;

};

#endif // PREFERENCEWINDOW_H@

MainWIndow.cpp
@#include <PreferenceWindow.h>
MainWindow::MainWindow() {
fileMenu = menuBar()->addMenu(tr("&File"));
editMenu = menuBar()->addMenu(tr("&Edit"));
newAct=new QAction(QIcon("images/new.png"), tr("&New"), this);
newAct->setShortcuts(QKeySequence::New);
newAct->setStatusTip(tr("Create a new file"));
editAct = new QAction(tr("&Edit"), this);
editAct->setShortcuts(QKeySequence::Preferences);
editAct->setStatusTip(tr("Set preferences"));
connect(newAct, SIGNAL(triggered()), this, SLOT(newWindow()));
connect(editAct, SIGNAL(triggered()), this, SLOT(openPreferencesMenu()));
fileMenu->addAction(newAct);
editMenu->addAction(editAct);

}

void MainWindow::openPreferencesMenu() {
PreferenceWindow *p = new PreferenceWindow();
}

void MainWindow::newWindow() {

MainWindow *w=new MainWindow();
w->setAttribute(Qt::WA_DeleteOnClose);
w->move(x()-10,y()-10);
w->show();

}@

PreferenceWindow.cpp
@#include <PreferenceWindow.h>
#include <QHBoxLayout>
PreferenceWindow::PreferenceWindow() {

this->setModal(true);
programPath= new QLineEdit(this);
programPathLabel=new QLabel(tr("program path : "), this);
layout=new QFormLayout();

programDefaultOptions=new QLineEdit(this);
programDefaultOptionsLabel=new QLabel(tr("Default options :"),this);
acceptButton = new QPushButton(tr("Accept"));
cancelButton = new QPushButton(tr("Cancel"));

layout->addRow(programPathLabel, programPath);
layout->addRow(programDefaultOptionsLabel, programDefaultOptions);
layout->addRow(acceptButton, cancelButton);

this->setLayout(layout);
connect(acceptButton, SIGNAL(clicked()), this, SLOT(accept()));
connect(cancelButton, SIGNAL(clicked()), this, SLOT(reject()));

this->show();

}
@

Thanks,

Saroupille.

Colon

Create PreferenceWindow in MainWIndow.cpp like this:

pwin = new PreferenceWindow();
pwin->setHidden(true);

and the SOLT: openPreferencesMenu()
void MainWindow::openPreferencesMenu() {
pwin->show();
}

Saroupille

Thanks, it seems to work !

But I don't really understand why my method caused this error. And why your method is better ?

Colon

the compiler should tell you
with your code you get:
warning: unused variable 'p' [-Wunused-variable]
PreferenceWindow *p = new PreferenceWindow();
^
you create the window as local variable

Saroupille

Indeed, thanks !