Re: unistd.h first?

[Paul Eggert]

address@hidden (Karl Berry) writes:

> I was under the impression that <unistd.h> should be included before
> just about any other system header, because it's <unistd.h> that defines
> _POSIX_VERSION, which can affect just about anything.

But _POSIX_VERSION isn't supposed to affect anything: it's supposed to
be imported from the system headers to user code.

Perhaps you're thinking of _POSIX_C_SOURCE (formerly _POSIX_SOURCE)?
That feature-test macro is exported from user code into system
headers; it's the sort of thing that might need to be defined first on
weird platforms.  I've never need of _POSIX_C_SOURCE being needed, and
the only time I know that _POSIX_SOURCE was needed was on Minix.