POSIX, ANSI C, and __STDC__

[Doug Gwyn]

In article <915 at sfmin.UUCP> dfp at attunix.att.com (Dave Prosser) writes:
>On another point, it was stated that __STDC__ cannot be undefined or
>its value be changed.

A strictly conforming program cannot #undef either __STDC__ or
_POSIX_SOURCE.  (I think someone suggested #undefing the latter
to obtain a strictly conforming C environment within a POSIX
implementation.)

Thanks very much for the comments.  They clear up some confusion about
what is going on.  If you want vendors to "follow AT&T's lead" in the
use of __STDC__==0, AT&T had better work with them NOW, because it's
already starting to happen in what appears to be an uncoordinated way.