[JonChesterfield]

There's fifty year old simulation software in use today. I ported some to semi-modern x64 and learned things I've gratefully forgotten about floating point in the process. Also that "VAX" and "SUN" Unix behaved differently, for whatever that's worth.

I would say that was viable because it had zero dependencies and could be built with the equivalent of gfortran *.f77, provided one changed the source in plausible looking ways first.

If your software relies on fetching things from the Internet it is probably doomed within a year or so and surely within a decade.

Wouldn't bet on today's up and coming language still existing either. C89? Will probably still build fine with some compiler passing appropriate flags.

Hardcoding x64 or aarch64 assumptions likely bad for longevity too, as both are surely gone before 2075 ticks around, though equally I couldn't find a VAX and still got that code running. So that's more about minimising the cost of porting rather than anything fundamental.

[phkahler]

>> I would say that was viable because it had zero dependencies and could be built with the equivalent of gfortran *.f77, provided one changed the source in plausible looking ways first.

Came to say this. Minimize your dependencies. Software can last forever, but everything around it changes and can break or otherwise cause incompatibilities.