It's now 2019, and as far as I know, MSVC still doesn't have full support for the 20-year-old C99 standard. So either you restrict yourself to the subset of C9

It's now 2019, and as far as I know, MSVC still doesn't have full support for the 20-year-old C99 standard. So either you restrict yourself to the subset of C99 which MSVC understands (AFAIK, newer MSVC releases understand more and more of the C99 standard), or just decide MSVC is no longer relevant (which is easier now that clang-cl exists; some big projects like Firefox and Chrome went this way, see for instance https://blog.mozilla.org/nfroyd/2019/04/25/an-unexpected-benefit-of-standardizing-on-clang-cl/ https://blog.mozilla.org/nfroyd/2019/04/25/an-unexpected-ben...).