Make NotifyFunction Optional

[Ayush1325]

Rust uses Option<fn ..> to represent Nullable Function pointer. It will have the same exact ABI (according to the docs I linked above) as a fn .. but will allow null.

This is needed since the NotifyFunction parameter is Optional.

It might be a good idea to check what other Function pointers should be represented in this way.

Signed-off-by: Ayush Singh ayushsingh1325@gmail.com

[dvdhrm]

It might be a good idea to check what other Function pointers should be represented in this way.

Correction: -should +must

I was not aware that rust does not allow NULL as function pointer, but obviously it does not. While you can still transmute the function call to void* and pass NULL, this is really ugly. So yeah, you are on to something, I think we have to convert them all.

I was shortly thinking of adjusting the type-definition to include the Option, but I think the correct call is to adjust the protocol-functions, just as you did. It does make us vulnerable to future spec updates that somehow allow passing NULL were it didn't before, but lets not think too hard about that.