I have - although POSIX covered a fair number of them and POSIX-ish or pretend-to-be-POSIX made up some more. That could all usually be covered with a pretty th

I have - although POSIX covered a fair number of them and POSIX-ish or pretend-to-be-POSIX made up some more. That could all usually be covered with a pretty thin utility layer, and the compiler-of-the-day for whatever the platform was. (and, sometimes, a whole lotta #IFDEFs!) You must be talking about something more extreme, maybe in embedded land? Do you happen to have a small number of f'rinstances?