Memory leak in a simple opengl program

Question

Hi all, I've wrote a simple opengl program to make some test. Here is the program:

#include <QApplication>
#include <QGLWidget>
#include <QTimer>
#include <glut.h>

class Ren : public QGLWidget
{
public:
 Ren() : QGLWidget() 
 {
  timer = new QTimer(this);
  connect(timer, SIGNAL(timeout()),
   this, SLOT(updateGL()));
 }

 void startUpdateTimer()
 {
  timer->start(40);
 }

 void initializeGL()
 {
  glShadeModel(GL_SMOOTH);      
  glClearColor(0.5f, 0.5f, 0.5f, 0.0f);     
  glClearDepth(1.0f);       
  glEnable(GL_DEPTH_TEST);   
 }

 void resizeGL(int width, int height)
 {
  if(height == 0){
   height = 1;
  }
  glViewport(0, 0, width, height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  GLfloat aspectRatio = (GLfloat)width / (GLfloat)height;
  gluPerspective(60.0, aspectRatio, 0.01, 10000.0);
  glMatrixMode(GL_MODELVIEW);
 }

 void paintGL()
 {
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glLoadIdentity();

  gluLookAt(0, 0, 1, 0, 0, 0, 0, 1, 0);

  glColor3d(1, 0, 0);
  glutSolidCube(0.3);
 }

 QTimer *timer;
};

int main(int argc, char **argv)
{
 QApplication app(argc, argv);

 Ren r;
 r.show();
 r.startUpdateTimer();

 return app.exec();
}

The problem is that the application is leaking memory, when timer is active. For leak detection I used windows task manager.

Answer 1

Since Rend is a subclass you must declare a virtual destructor. Otherwise you have memory leaks and you can have heap corruption if you delete your Ren object while using it as QGLObject.

Edit: Removed part:

In the Constructor, your are allocating memory for the timer but you never release it. You need to delete the timer pointer.

Answer 2

Please give us more detail about how much memory your program is leaking. I highly doubt that your code is leaking because you're just allocating one QTimer object. Even if you don't delete your timer this wouldn't be a problem, because the OS releases the memory anyway. This is ugly, of course, but not leaking in a strict sense.

If the allocated memory grows steadily over time, then there's a memory leak. If that's the case, it's not your code's fault, since there's simply nothing you allocate except the timer once.

Answer 3

Sorry. I was wrong. There is now leaking. The 'leaking' is stopped after some time (about a minute). I think it's a kind of opengl or Qt job. I've looked some Qt examples and saw the same thing in Textures example. The same thing is happened, if I change another examples to draw something else in PaintGL() function (depending on it there is different 'leaking' time.