The problem is that embedded compilers are not known for keeping up with the standards. The only hope is that the moves to GCC and Clang continue.
So, presumably, RISC-V will also get it at the same time.
Every compiler you have used operates at a bare minimum on the C standard. That’s why they are often advertised (if not GCC/Clang which are assumed to be up to date) as “C(89|99|11|17) compliant.” “Code that works” is code which is operates under constraints and guarantees specified by a standard, anything else is undefined or unportable.