What is the difference between a dangling pointer and memory leak?

Question

I'm new to C++ and would like to ask if the code below is an example of a dangling pointer or a memory leak because it is pointing outside the dynamically allocated array:

int * n = new int[10];
for (int prev = 0; prev < 10; prev++) {
    *n = *(n + prev + 1);
}
delete[] n;
n = nullptr;

Answer 1

A dangling pointer is a pointer which points to an address where no object resides. I.e. it points at invalid memory. The word "dangling" usually carries the connotation that it used to point to something valid and that something got destroyed (either because it was explicitly deallocated or because it went out of scope).

A memory leak happens when you lose all track of dynamically allocated piece of memory; that is, when you "forget" last pointer that was pointing to that memory, meaning you can no longer deallocate it. Your code would create a memory leak if you did n = nullptr; before you call delete[] n;.

If I had to describe your case with one of these two terms, it would be "dangling pointer," simply because you're reaching beyond the buffer in the last iteration. However, I wouldn't normally call it a "dangling pointer," because it was never valid in the first place. I would call this a "buffer overrun" or an "out-of-bounds access."