Also 8 and 16 bit embedded toolchains are certainly not on C11 / C17, they can hardly afford full C89.
https://sdcc.sourceforge.net/
That's the nice thing with C: it's much easier for small teams to fully support than the latest C++ standards.
Also 8 and 16 bit embedded toolchains are certainly not on C11 / C17, they can hardly afford full C89.