[rhelgeby]

The AddToForward function documentation states that it returns true on success and false otherwise.

Which extra checks do I have to do to prevent it from returning false? I want to avoid delegating this check to the caller of my function.

[Cookies.net]

Have a look at these 2 functions here and here.

It'll only return false if you're currently having some parameters pushed to the forward, that's it.
So as long as you remember to Call_Finish or Call_Cancel after all your Call_Push* you're good to go.

Also, aren't problems usually better dealt with after they happen? This seems to be a question that's asked in advance, for something that could theoretically happen, but hasn't seemingly been a problem for anyone ever before.

[rhelgeby]

Thank you. It's used in an API I'm working on, and I need to be clear on every outcome of its functions. I don't want to make assumptions.

It sounds like it should throw an error instead of returning false. On the other hand I can't see any reason it should fail. I guess it's not reading the list of callbacks until the call is finished, so it could be fine to add forwards late too.