C++ Memory leaks on Windows 7

Question

I'm writing a program (C++, MinGW 32 bit) to batch process images using OpenCV functions, using AngelScript as a scripting language. As of right now, my software has some memory leaks that add up pretty quickly (the images are 100-200 MB each, and I'm processing thousands at once) but I'm running into an image where Windows doesn't seem to be releasing the memory used by my program until rebooting.

If I run it on a large set of images, it runs for a while and eventually OpenCV throws an exception saying that it's out of memory. At that point, I close the program, and Task Manager's physical memory meter drops back down to where it was before I started. But here's the catch - every time I try to run the program again, it will fail right off the bat to allocate memory to OpenCV, until I reboot the computer, at which point it will work just great for a few hundred images again.

Is there some way Windows could be holding on to that memory? Or is there another reason why Windows would fail to allocate memory to my program until a reboot occurs? This doesn't make sense to me.

EDIT: The computer I'm running this program on is Windows 7 64 bit with 32 GB of ram, so even with my program's memory issues, it's only using a small amount of the available memory. Normally the program maxes out at a little over 1 GB of ram before it quits.

EDIT 2: I'm also using FreeImage to load the images, I forgot to mention that. Here's the basis of my processing code:

//load bitmap with FreeImage
FIBITMAP *bitmap = NULL;
FREE_IMAGE_FORMAT fif = FIF_UNKNOWN;
fif = FreeImage_GetFileType(filename.c_str(), 0);
bitmap = FreeImage_Load(fif, filename.c_str(), 0);
if (!bitmap) {
    LogString("ScriptEngine: input file is not readable.");
    processingFile = false;
    return false;
}
//convert FreeImage bitmap to my custom wrapper for OpenCV::Mat
ScriptImage img;
img.image = fi2cv(bitmap);
FreeImage_Unload(bitmap);

try {
    //this executes the AngelScript code
    r = ctx->Execute();
} catch(std::exception e) {
    std::cout << "Exception in " << __FILE__ << ", line " << __LINE__ << ", " << __FUNCTION__ << ": " << e.what() << std::endl;
}

try {
    engine->GarbageCollect(asGC_FULL_CYCLE | asGC_DESTROY_GARBAGE);
} catch (std::exception e) {
    std::cout << "Exception in " << __FILE__ << ", line " << __LINE__ << ", " << __FUNCTION__ << ": " << e.what() << std::endl;
}

As you can see, the only pointer is to the FIBITMAP, which is freed.

Answer 1

It is very likely that you are making a copy of the image data on this line:

img.image = fi2cv(bitmap);

Since you are immediately freeing the bitmap afterwards, that data must persist after the free.

Check if there is a resource release for ScriptImage objects.