Snacc function declaration syntax

I am now trying to use Snacc (Sample Neufeld ASN.1 to C/C++ Compiler) v.1.4 and I cannot run it to get the transfer (encoded) syntax. The errors have shown that the following PROTO syntaxs are the ones cause the problems.

-- void FreeAsnAny PROTO ((AsnAny *v));

--typedef AsnLen (* EncodeFcn) PROTO ((BUF_TYPE b, void *value));


Could anyone please explain how these syntax work and what is PROTO used for?

Thanks,