Smart pointers - cases where they cannot replace raw pointers

Question

HI,

I have this query about smart pointers.

I heard from one of my friends that smart pointers can almost always replace raw pointers. but when i asked him what are the other cases where smart pointers cannot replace the raw pointers,i did not get the answer from him.

could anybody please tell me when and where they cannot replace raw pointers?

Answer 1

1. Passing pointers to legacy APIs.
2. Back-references in a reference-counted tree structure (or any cyclic situation, for that matter). This one is debatable, since you could use weak-refs.
3. Iterating over an array.

There are also many cases where you could use smart pointers but may not want to, e.g.:

1. Some small programs are designed to leak everything, because it just isn't worth the added complexity of figuring out how to clean up after yourself.
2. Fine-grained batch algorithms such as parsers might allocate from a pre-allocated memory pool, and then just blow away the whole pool on completion. Having smart pointers into such a pool is usually pointless.