This is more something for a wrapper of the library.
But in some cases, there legitimately may not be a unique signature for a function.
I ran across this in Orcs Must Die 3 today, an Unreal game.
[I don't have experience with unreal whatsoever, it seems I'm doing the Unreal reflection stuff by hand from scratch]
In any case, sometimes only way you can uniquely identify a function is to check if a masked out part of the signature is a certain constant.