IntPtr causing memory leak?

Question

This function is in a loop. When I run the program, the line with IntPtr is giving me memory problems, I've put delete[], but it still doesn't solve the memory problem, can anyone help please? thanks

void showImage(IplImage *img,System::Windows::Forms::PictureBox^ picturebox)
{

IntPtr ip(new unsigned char[img->widthStep*img->height]); // this line causing memory usage to keep going up very fast

//memcpy(ip.ToPointer(),img->imageData,img->widthStep*img->height);

//picturebox->Image = gcnew Bitmap(img->width,img->height, img->widthStep, System:rawing::Imaging::PixelFormat::Format24bppRgb, ip);

delete[] ip;
} 

This is C++\CLI

Answer 1

It is rather sad that this code compiles, but that is by design. The delete operator applied to a managed type doesn't actually free any memory. It calls the IDisposable::Dispose() method on the passed object. It is rather sad that this even works, the IntPtr gets boxed to turn it into an object and then checked to see if it implements the IDisposable interface. It doesn't of course, nothing happens.

You have to pass the pointer that you got back from the new operator. Don't forget to do this in a finally block so an exception cannot cause a leak.

Btw, there are more complications in the code that you commented. The Bitmap constructor you use requires you to keep the IntPtr valid, you cannot release the memory until the Bitmap is no longer used. So using delete isn't actually valid. Consider using Bitmap.LockBits() instead to get a pointer to a Bitmap that manages its own memory. And watch out for stride.