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

I came up with the following workaround for PP_NARG:

#define PP_NARG(...)     (sizeof(#__VA_ARGS__) - 1 ?       \
    PP_NARG_(__VA_ARGS__, PP_RSEQ_N()) : 0)

It stringifies __VA_ARGS__, so if it's empty its length equals 1 (because #__VA_ARGS__ == '\0').
It works with -std=c99 -pedantic.

I still have problems with wrapping the variadic function though. When __VA_ARGS__ is empty, my_func expands to func(0, ) which triggers a compilation error.