I know but I don't think the risks justify using this, as demonstrated here. "It's fine when it's used correctly" except it's so hard to use correctly. It completely messes up any analysis of codepaths because you have this "time travel" footgun that can bypass everything.

Exceptions aren't great for that either, but languages that feature them at least have the tooling and support features to make them work. C has no destructors or anything to handle exception unwinding cleanly. Scheme has call/cc, but scheme has a big runtime and garbage collector to deal with the fallout.

Let the branch predictor do its job and implement error checking properly, I say. If performance matters so much that you worry about pipeline flushes and icache thrashing, surely you wouldn't be using PHP anyway.

setjmp, longjmp and gets are 3 function I would absolutely ban in any C codebase I would be responsible for. Maybe strncpy too. and strtok. C is fun.