Is it good practice to NULL a pointer after deleting it?

Question

I\'ll start out by saying, use smart pointers and you\'ll never have to worry about this.

What are the problems with the following code?

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Answer 1

Setting pointers to NULL after you've deleted what it pointed to certainly can't hurt, but it's often a bit of a band-aid over a more fundamental problem: Why are you using a pointer in the first place? I can see two typical reasons:

• You simply wanted something allocated on the heap. In which case wrapping it in a RAII object would have been much safer and cleaner. End the RAII object's scope when you no longer need the object. That's how std::vector works, and it solves the problem of accidentally leaving pointers to deallocated memory around. There are no pointers.
• Or perhaps you wanted some complex shared ownership semantics. The pointer returned from new might not be the same as the one that delete is called on. Multiple objects may have used the object simultaneously in the meantime. In that case, a shared pointer or something similar would have been preferable.

My rule of thumb is that if you leave pointers around in user code, you're Doing It Wrong. The pointer shouldn't be there to point to garbage in the first place. Why isn't there an object taking responsibility for ensuring its validity? Why doesn't its scope end when the pointed-to object does?