It’s still C though, and rust is not an option. What else would you call it? Lots of c libraries for embedded target C89 syntax for exactly these reasons. Also for what it’s worth, SDCC seems to support very modern versions of C (up to C23), so I also don’t think that critique is very valid for the 8051 or stm8. I would argue that c was built with targets like this in mind and it is where many of its quirks that seem so anachronistic today come from (for example int being different sizes on different targets)