Writing compilers for fun is not relevant to HN? Get off your high horse, this project is really cool!

You are joking right? This is the most HN sounding title I've seen in a while.

It's (1) a side project that involves (2) writing code to implement (3) a compiler for a subset of C.

I don't really see where your issue is, but I do see 3 reasons for it being on HN.

It is called "HackerNews", not "PracticalAndEfficientNews

Why not? Have you never coded something for fun and wanted to show it off? HN seems like just the place to do that, full of like minded people who just code for the sake of coding.

> SubC is a simple subset of C originally written by Nils Holms for teaching newcomers how to write a compiler.

I assume it's for fun and to learn

You can do a lot more with compiler infrastructure than simply building programs. C89 is a useful starting point.

It would have been even more fun(and useful) to write a safer C.