[Insight-users] smart pointers and local scope

[Michael]

Hi,

if I properly understand

http://public.kitware.com/pipermail/insight-users/2003-September/004820.html

any memory referenced by smart pointers should be released when leaving 
the local scope in which the smart pointers were defined. I've written 
the following little program:

#include <iostream>
#include "itkImage.h"
#include "itkImageFileReader.h"

int main(int argc, char** argv)
{
    const unsigned int Dimension = 2;
    typedef unsigned char PixelType;
    typedef itk::Image<PixelType, Dimension> ImageType;
    typedef itk::ImageFileReader<ImageType> ReaderType;

    char ch;

    std::cout << "before block" << std::endl;
    std::cin >> ch;


    { // local scope

        ReaderType::Pointer reader = ReaderType::New();

        if (argc < 2) {
            std::cout << "filename required." << std::endl;
            return -1;
        }
        reader->SetFileName(argv[1]);

        try {
            reader->Update();
        } catch (itk::ExceptionObject &e) {
            std::cout << e << std::endl;
            return -1;
        }

        std::cout << "after update: " << std::endl;
        std::cin >> ch;
    }

    std::cout << "after block" << std::endl;
    std::cin >> ch;

    return 0;
}

When compiling it with Visual Studio 6 under Windows and looking at the 
memory usage at the points asking for input everything looks ok: The 
memory usage is about 1.5 MB before the local scope, about 7.8 MB after 
the update call and about 2.2 MB after leaving the local scope. 
Obviously, the image data has been released (I used the 
BrainProtonDensitySliceBorder20.png image, which I upscaled by a factor 
10 (in each direction)). Except of the (small) difference of 0.7 MB the 
same amount of memory is used before and after the local scope (where do 
the 0.7 MB come from?).

When I compile the program with gcc under SunOS, however, the memory 
usage behaves differently. "top" shows the following values:

before block: SIZE 4888K, RES 1672K
after update: SIZE 10M, RES 8520K
after block: SIZE 10M, RES 8520K

It seems to me, that the memory of the smart pointers was not freed 
after leaving the local scope. Why is the behaviour different from the 
one in Windows?

Thanks,

Michael