20 years ago was 2003, four years after C99. First x86-64 CPUs were released 20 years ago. Compiling 20 year old C codebase should not be an issue at all if it

20 years ago was 2003, four years after C99. First x86-64 CPUs were released 20 years ago. Compiling 20 year old C codebase should not be an issue at all if it was half-decent to begin with. Compiling pre-ANSI-C and pre-POSIX codebases might have challenges, but standardization has really gotten us lot of stability here. I'd expect conservatively written C99/POSIX code to be usable certainly for another 20 years, there is just so much inertia there https://en.wikipedia.org/wiki/Lindy_effect https://en.wikipedia.org/wiki/Lindy_effect