Re: problems compiling with glibc-2.8

[Russ Allbery <rra@stanford.edu>]

Hallvard B Furuseth <h.b.furuseth@usit.uio.no> writes:

> Should _BSD_SOURCE or _SVID_SOURCE provide struct ucred?  If so the
> problem this time is hopefully only that he didn't know the struct is
> not a Gnu invention.

Pure System V does this a different way, so I doubt _SVID_SOURCE should.
Not sure about _BSD_SOURCE; that would be the most likely one.  Note that
_GNU_SOURCE isn't only used for GNU extensions; it's basically used for
anything that doesn't fall into a clear standard.

So protecting with _GNU_SOURCE doesn't mean that glibc maintainers think
it's a uniquely GNU extension, just that they don't think it falls into
one of the other standard feature-test macros.

> Well, headers in several OSes broke at least some years ago when one
> #defined feature test macros like _POSIX_SOURCE.  IIRC including some
> glibc headers.  Still, they've all had decades to clean up now.

These days, I basically always use the AC_GNU_SOURCE Autoconf macro to
define _GNU_SOURCE, since I almost always run into something that glibc
hides unless you define _GNU_SOURCE.  Unless you're trying to maintain
tight control over what enters your namespace, fighting with the
standardized feature-test macros is often more trouble than it's worth.

-- 
Russ Allbery (rra@stanford.edu)             <http://www.eyrie.org/~eagle/>