[thealistra]

It's similiar to how clang tries to be a gcc replacement. I think clang got started in ~2008 and now you can build most of the open source projects with it. But still some packages use GNU extensions or they depend on some gcc-only features.

I think the reason it works for clang is because they're really trying hard to be drop-in compatible with gcc. I remember reporting some minor thing like: command line flag -- in gcc generated a warning, but it didn't return an error code on exit and it did in clang, so they've changed it, because it caused crashes some project builds.

Not sure how pypy handles the compatibility now, because I couldn't compile it yet, tried like 4 times already and it always crashes randomly or it gets out of memory or something.