CPython, C standards, and IEEE 754

C11 anon union support has been supported for a long time via "ms-extensions" on all three major compilers. That flag turns on just the ms-extensions that were probably good ideas in hindsight, not the really horrible ones. There's a gcc only variant called plan9-extensions that's even cooler, and you can absolutely see the seeds of some Go features in that extension.

Sidenote: while msvc is pretty unlikely to ever support them I actually don't think VLAs are that horrible of a feature. Compilers just have to emit stack probes! which they were all really bad about doing initially (and some even still don't with default settings!). IMO the standard should have required them to emit them unconditionally (unless the compiler can prove the size is actually < 1 page, for sure). I should write a paper, tbh.