Macro to count number of arguments

Question

I have a variadic function from a third-party C library:

int func(int argc, ...);

argc indicates the number of passed optional

Answer 1

The full example on Mehrwolf's answer unfortunately doesn't compile on VS2010 nor it does on VS2015 (i tried it also on this online VS compiler). A different approach on this problem that allows to produce cross-platform code that compiles on a wide range of compilers is using non-standard extensions that are also available in MS compilers as in my answer to a similar question. Also, differently form the cited answer, the result of PP_NARG((a, b, c)) using the extensions (in both MS and gcc/clang compilers) is 1 and not 0.