There you can find a recursive macro expansion implementation (as a gcc hack) that fits on a slide:

  #2""3
  
  #define PRAGMA(...) _Pragma(#__VA_ARGS__)
  #define REVIVE(m) PRAGMA(push_macro(#m))PRAGMA(pop_macro(#m))
  #define DEC(n,...) (__VA_ARGS__)
  #define FX(f,x) REVIVE(FX) f x
  #define HOW_MANY_ARGS(...) REVIVE(HOW_MANY_ARGS) \
      __VA_OPT__(+1 FX(HOW_MANY_ARGS, DEC(__VA_ARGS__)))
  
  int main () {
      printf("%i", HOW_MANY_ARGS(1,2,3,4,5)); // 5
  }

It sounds like the one in the article works for more compilers, but there doesn't seem to be a copy-pasteable example anywhere to check for myself. Also, the "Our GitHub Org" link on the site just links to github.com.

▲ viega 6 hours ago | parent | next [-]

Author of the article here.

Absolutely, the code box under the ascii art is a complete implementation, just paste that in a C file, and then use `H4X0R_VA_COUNT(...)`.

Or, you could follow the link the my typed variadic arguments article (from which this post forked off). The repo there is: https://codeberg.org/h4x0r/vargs

▲

viega 5 hours ago | parent [-]

And yes, GCC extensions are often going to be adopted in clang, but generally not the broader world of C and C++ compilers. Everything in my article conforms to the standard.

▲

fuhsnn 5 hours ago | parent [-]

I played with a lot of preprocessor implementations and did my own (redesigned chibicc's expansion algorithm), not many of them even have paint-blue behavior exactly right (the standard text is vague, to me it was more "matching GCC's" than "conforming to standard").

	▲	viega 5 hours ago \| parent [-]
		That's interesting. I agree with you that the standards text is pretty vague. I think that's why other attempts to show how to do this kind of thing don't get deep enough on the semantics, and why I adopted a "try it and see" strategy. I do try to avoid this kind of thing unless necessary, so I don't have experience as to where the different compilers will fall down on different corner cases. I'd find it very interesting though, so please do share if you kept any record or have any memory!

▲ lifthrasiir 6 hours ago | parent | prev [-]

Ask and you'll get: https://c.godbolt.org/z/rKsWT5E9T

It seems that MSVC doesn't like those macros, though.

	▲	david2ndaccount 5 hours ago \| parent [-]
		Works with MSVC if you add /Zc:preprocessor (to get a standard compliant preprocessor instead of the legacy one).