[fuhsnn]

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]

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!

[fuhsnn]

Examples from this article[1] frequently yield inconsistent result across implementations, particularly the ones that put parenthesis in macros, it is indeed a very corner-case-y thing to do though.

[1] https://www.scs.stanford.edu/~dm/blog/va-opt.html#c-macro-ov...

[viega]

From my read, that article doesn't have anything in it that isn't standards compliant C. My memory is getting worse as I get older, but I'd say by C17 all that was standard, and definitely in C23.

I've noticed many people are still building on systems where the compiler is a bit older, and defaults to C11, even if it has support for C17, so perhaps that's the problem?