The proposals for Boring C or "Friendly Dialect of C" or whatever has been around for a while. None went beyond the early design stages because, it turns out, no two experienced C programmers could agree on what parts of C are reasonable/unreasonable (and should be kept/left out), see [0] for the first-hand recount.

[0] https://blog.regehr.org/archives/1287

> In contrast, we want old code to just keep working, with latent bugs remaining latent.

Well, just keep compiling it with the old compilers. "But we'd like to use new compilers for some 'free' gains!" Well, sucks, you can't. "But we have to use new compilers because the old ones just plain don't work on the newer systems!" Well, that sucks, and this here is why "technical debt" is called "debt" and you've managed to hold paying it off until now the repo team is here and knocking at your door.