Take a look at https://www.kermitproject.org/ckupdates.html . These quotes come from the last few years:

> [fixes] specific to VMS (a.k.a. OpenVMS),

> For conformity with DECSYSTEM-20 Kermit ...

> running on a real Sun3, compiled with a non-ANSII compiler (Sun cc 1.22)

> this is fatal in HP-UX 10 with the bundled compiler

> OpenWatcom 1.9 compiler

> OS/2 builds

> making sure that all functions are declared in both ANSI format and K&R format (so C-Kermit can built on both new and old computers)

Oooooh! A clang complaint: 'Clang also complains about perfectly legal compound IF statements and/or complex IF conditions, and wants to have parens and/or brackets galore added for clarity. These statements were written by programmers who understood the rules of precedence of arithmetic and logical operators, and the code has been working correctly for decades.'