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.