Thread: Error, Access Violation, using Templated Class

Hey guys, anyone mind helping, I'd really appreciate it.

I'm getting an error, access violation according to MSVC6, and I've used cout/endl debugging method to show which method its in.

Code:

template< typename Datatype >
int Array<Datatype>::Resize (USHORT p_sizeChanged)
{
  Datatype* tempArray = new Datatype[p_sizeChanged];
  if (tempArray == 0) {
    std::cout << "Could not allocate enough memory." << std::endl;
    return -1;
  }

  USHORT* reSized;

  if (p_sizeChanged < m_size) {
    std::cout << "DEBUG 2" << std::endl;
    *reSized = p_sizeChanged;
  } else if (p_sizeChanged > m_size) {
    std::cout << "DEBUG 2++" << std::endl;
    *reSized = m_size;
  } else {
    std::cout << "Could not figure out the changed array size." << std::endl;
    return -1;
  }

  for (USHORT index = 0; index < *reSized; ++index)
    tempArray[index] = m_array[index];

  m_size = p_sizeChanged;

  if (m_array != 0)
    delete[] m_array;

  m_array = tempArray;
  tempArray = 0;

  return 0;
}

int main ()
{
  Array<int> listLevels(10);

  USHORT index;

  for (index = 0; index < 10; ++index) {
    listLevels[index] = index;
  }

  listLevels.Display ();

  std::cout << "DEBUG 1" << std::endl;

  std::cin.get ();

  //increase the size of the array with Renew.
  listLevels.Resize (30);

  std::cout << "DEBUG 3" << std::endl;
}

The Array class is in a .h file, and I'm using templates for the class so I had to use a template for the method thats in a different file. It doesnt get further than:
std::cout << "DEBUG 2++" << std::endl;
in the Resize method. I'm assuming its angry with me trying to access the private variable of the class: m_size. If it is, that really annoys me.. I mean if its going to pull some violation error because I'm using templates then what the hell is the point of them. Unless an error is occuring because of Datatype being unaccessible? since the method is seperated from the class and its templated.

Either way.. templates are starting to ........ me off.

Originally Posted by Daved

Why is reSized a pointer? You never allocate memory for it so it is not pointing to anything valid. You should just make it a plain USHORT. This has nothing to do with templates, just a simple pointer error.

Woah.. didnt even notice that, thanks! Why the hell did I make it a pointer in the first place... odd...

Topic Closed.

Don't start losing hope about working with templates. They are your friends and afford you magical opportunities in programming.

Your error is that you are dereferencing an uninitialized pointer. You declare reSized as a pointer that is pointing at nothing (except that it contains some garbage address) then you dereference it to assign it a value. What I believe you mean to be doing is making reSized point at a variable. So instead of *reSized = someval; you should be saying reSized = &someval;, setting the pointer to the address of an existing variable.

Dae already found the error.