As someone who loves and enjoys writing Plan 9 c, all I can say is "standard c", whatever that means these days, is a mess. Too many things to name ranging from the only two oss compilers being bloated monsters, post c99 additions being pointless, in-line asm ruining portability*, and POSIX can die in a fire (along with typewriter terminals.)

I have a friend who is currently on the C committee and is likely going to leave because of all the bad ideas which have both been implemented and going to be implemented.

* No, spamming a million ugly #ifdefs all over the source files is gross and hard to read. Split up the code dammit.

> gcc, however, always defines FLT_ROUNDS to 1

Well, considering that gcc doesn't support the FENV_ACCESS pragma, and as such all fesetround calls are always UB, it is valid for it to act as if the rounding mode never changes from the default :)