Properly Reading a Char from an Int in C on a Stack

Answer 1

Well . . . it looks like you're double-freeing the data pointer:

pushStack( stack, letter );
...
free( letter );
...
free( stack->top->dataPointer ); //(in destroyStack)

So, I would start by removing the free( letter ) line.

Answer 2

Your problem is with letter. It's only allocated once and when you push it onto the stack, it doesn't make a copy. That's why your top data pointer is always the last thing you pushed. Then you free it and destroyStack frees it and you get another error. Since the stack functions were from your assignment, the fix is to allocate a new data pointer inside the loop every iteration and ensure that it's not freed outside of destroyStack.

Answer 3

Look at how many int sized pieces of memory you've allocated. I think you'll need to allocate a new one for each entry you push onto the stack.