Visual Studio 2012 C++ console application exits Immediately

Question

Im working with C++ In Visual Studio 2012 with the OpenCV library. The problem is that when I run my console application, after about 2 or 3 seconds it closes. Heres the code:

#include "cv.h"
#include "highgui.h"

IplImage* GetThresholdedImage(IplImage *img)
{
    // Convert the image into an HSV image
    IplImage* imgHSV = cvCreateImage(cvGetSize(img), 8, 3);

    cvCvtColor(img, imgHSV, CV_BGR2HSV);

    IplImage* imgThreshed = cvCreateImage(cvGetSize(img), 8, 1);

    cvInRangeS(imgHSV, cvScalar(20, 100, 100), cvScalar(30, 255, 255), imgThreshed); //Detect Colour

    cvReleaseImage(&imgHSV);
    return imgThreshed;
}

int main()
{
    // Initialize capturing live feed from the camera
    CvCapture* capture = 0;
    capture = cvCaptureFromCAM(0); // cvCaptureFromCAM(0) indicates camera being used,           Change the 0 for a different camera

    // Couldn't get a device? Throw an error and quit
    if(!capture)
    {
        printf("Camera not working\n");
        return -1;
    }

 // The two windows we'll be using
cvNamedWindow("video"); //Create new window containing video
cvNamedWindow("thresh"); //Create another window containing thresholded image

// This image holds the "scribble" data
// the tracked positions of the ball
IplImage* imgScribble = NULL;

// An infinite loop
while(true)
{
    // Will hold a frame captured from the camera
    IplImage* frame = 0;
    frame = cvQueryFrame(capture);

    // If we couldn't grab a frame... quit
    if(!frame)
        printf("Couldnt get frame \n");



     // If this is the first frame, we need to initialize it
    if(imgScribble == NULL)
    {
        imgScribble = cvCreateImage(cvGetSize(frame), 8, 3);
    }

    // Holds the yellow thresholded image (yellow = white, rest = black)
    IplImage* imgYellowThresh = GetThresholdedImage(frame);

    // Calculate the moments to estimate the position of the ball
    CvMoments *moments = (CvMoments*)malloc(sizeof(CvMoments));
    cvMoments(imgYellowThresh, moments, 1);

    // The actual moment values
    double moment10 = cvGetSpatialMoment(moments, 1, 0);
    double moment01 = cvGetSpatialMoment(moments, 0, 1);
    double area = cvGetCentralMoment(moments, 0, 0);

    // Holding the last and current ball positions
    static int posX = 0;
    static int posY = 0;

    int lastX = posX;
    int lastY = posY;

    posX = moment10/area;
    posY = moment01/area;

    // Print it out for debugging purposes
    printf("position (%d,%d)\n", posX, posY);

    // We want to draw a line only if its a valid position
    if(lastX>0 && lastY>0 && posX>0 && posY>0)
    {
        // Draw a yellow line from the previous point to the current point
        cvLine(imgScribble, cvPoint(posX, posY), cvPoint(lastX, lastY), cvScalar(0,255,255), 5);
    }

     // Add the scribbling image and the frame
    cvAdd(frame, imgScribble, frame);
    cvShowImage("thresh", imgYellowThresh);
    cvShowImage("video", frame);

    // Release the thresholded image+moments we need no memory leaks please
    cvReleaseImage(&imgYellowThresh);
    delete moments;

        // We're done using the camera. Other applications can now use it
    cvReleaseCapture(&capture);
    return 0;

    // Wait for a keypress
    int c = cvWaitKey(10);
    if(c!=-1)
    {
        // If pressed, break out of the loop
        break;
    }

}
}

My Camera is working properly and it still quits. Thanks in advance

Answer 1

You are mixing together two ways of allocating/freeing memory - malloc/free and new/delete :

CvMoments *moments = (CvMoments*)malloc(sizeof(CvMoments));

and

delete moments;

You should not mix the two. malloc/free do not call constructor/destructor on the allocated memory. new/delete do call constructor/destructor on the allocated memory, and MIGHT be using other memory function instead of malloc/free to allocate/free the actual memory. As a result, you can get all sorts of errors emanating from reasons ranging from calling a destructor on unconstructed object to using non-corresponding functions to allocate/free memory.

Plus, there can be other problems, of course. This is an obvious one and you should start by fixing it.

EDIT #1: While everything said above is true and should be fixed, Andrey Smorodov's answer, probably, nailed it: you unconditionally return from inside the loop. I should've not stopped checking your code after I saw malloc/delete problem ;).

EDIT #2: To answer your comment. If CvMoments is a C-struct, use free instead of delete. If it is a C++ class, use new instead of malloc.

You also have to review the code in the end of your loop. It is hard to say what you want to do there. By the looks of it, I would put memory allocation for moments before the loop and free memory after the loop - you keep allocating/freeing same amount of memory. Do you even need it on heap? Can you not just put it on stack? It also seems that you want to keep working with camera until user pressed a key. Do you need to release camera AFTER user pressed a key or every time before you start waiting for it? In any case, your return statement exits the loop and main (and program) before control goes to if statement. Put return statement OUTSIDE the loop.

In short:

Before loop - allocate memory. Remember to use malloc/free or new/delete, but do not mix them. Think if you need heap at all, maybe stack is ok.

In loop - remove freeing memory, remove releasing camera, remove return. You will be using them on the next go through the loop, right? If user presses a key (inside the loop), you'll go out of the loop.

After the loop - now you really want to clean up. Free memory, release camera, return from main.

Answer 2

I think

// We're done using the camera. Other applications can now use it

cvReleaseCapture(&capture);

return 0;

must be out of while loop body.

Answer 3

Malloc and delete cannot be used together, use free(ptr) instead.