Actual "standard C" (along with most of the C stdlib) is pretty much useless for writing real-world applications, any non-trivial C code base will almost certainly use at least a handful non-standard extensions (sometimes even without knowing it) and both compiler- and platform-specific conditional code paths (just try how many libraries would compile with gcc's "-pedantic" flag, I bet it's not all that many).

This pragmatism by compiler vendors to just ignore the C standard where it doesn't make much sense, and to extend the language where it helps to solve real-world problems is actually a pretty powerful argument for C.