/*************************
destroyBinTree
this function destroys the binary tree and all data that is in the tree
when destroy is called.
****************************/
void destroyBinTree(Tree * toDie)
{
if(toDie)
{
destroyBinTree(toDie->left);
destroyBinTree(toDie->right);
free(toDie);
}
}
void exploitMemLeaks() {
// All data allocated and tracked, all will be freed
int * low = calloc(1, sizeof(int));
* low = 1;
int * mid = calloc(1, sizeof(int));
* mid = 2;
int * hi = calloc(1, sizeof(int));
* hi = 3;
printf("Created the following data to add to a tree:\n");
printf("Low: %d, Mid: %d, Hi: %d\n", * low, * mid, * hi);
// Test inside a tree
Tree * test = createBinTree(&compNum, &destructor);
addToTree(test, mid);
addToTree(test, low);
addToTree(test, hi);
printInOrder(test, &print);
// Up to here, as long as destroyBinTree is called, no leaks are possible
// Now lets look at some of the issues with the library
// Left will contain Low (1), we know this. This function allocates memory
// so it's return value must be freed
Tree * left = getLeftSubtree(test);
free(left);
// All is well, no memory leaks here
// Now let's get the right subtree, Hi (3), but before we free it, let's get
// get one of it's subtrees too. We know it won't contain anything so
// presumably we'll get some sort of error return value
Tree * right = getRightSubtree(test);
Tree * empty = getRightSubtree(right);
if (empty == NULL)
printf("The call to an empty subtree returned NULL.\n");
// Oh good, we did get some error handling, great now there's no problem
// OOPS, no, there's a huge issue. The getSubtree functions are presumably
// doing the following: allocating memory to a temporary new tree pointer,
// checking what's in the subtree and returning NULL if nothing is in it.
// So the temporary new tree pointer to allocated memory is completely lost
// in all instances.
// We can't even detect the error without a memory checker because the
// following call of free(NULL) has no effect
free(empty);
free(right);
destroyBinTree(test);
}
