Use of _XOPEN_SOURCE?

[Jeff Johnston]

Patch applied.  Thanks Craig.

-- Jeff J.

On 01/03/10 04:04 PM, Howland Craig D (Craig) wrote:
> I have put it into sys/features.h and included sys/features.h at the
> beginning of sys/config.h, as you suggest.  The patch is attached.  I
> built it under Cygwin and Linux and nothing failed.
>
> I noticed one thing that makes me wonder slightly as to whether it
> would need addressing is that in sys/unistd.h, line 260 includes
> sys/features.h, but this is after a check for _POSIX_SOURCE, the
> old (1990) form of _POSIX_C_SOURCE (line 196).  It's only gating one
> function prototype (vfork()).  IF we were to later try to attempt to
> do something with _POSIX_SOURCE, the prior inclusion of sys/features.h
> (due to being pulled in at the top) MIGHT make a difference.  I'm
> thinking that this is not worth worrying about.
>
> Speaking of _POSIX_SOURCE, it appears in 19 files under libc, all of
> which are just checks for it.  Something to do later.  (A note for
> the mailing list archive as a reminder for when we might:  2001 says
> "Since _POSIX_SOURCE specified by the POSIX.1-1990 standard did not have
> a value associated with it, the _POSIX_C_SOURCE macro replaces it,
> allowing an application to inform the system of the revision of the
> standard to which it conforms. This symbol will allow implementations to
> support various revisions of IEEE Std 1003.1-2001 simultaneously. For
> instance, when either _POSIX_SOURCE is defined or _POSIX_C_SOURCE is
> defined as 1, the system should make visible the same name space as
> permitted and required by the POSIX.1-1990 standard. When
> _POSIX_C_SOURCE is defined, the state of _POSIX_SOURCE is completely
> irrelevant.")
>
> A secondary question:  given that this change now makes anything that
> includes any system header end up with sys/features.h, should a cleanup
> be done to take out all #include<sys/features.h>  to avoid confusion?
> Or would it be worse for them to not have it and be assumed?  (It's
> obviously easier to do nothing.)
>
> Craig
>
>
> -----Original Message-----
> From: Jeff Johnston [mailto:jjohnstn@redhat.com]
> Sent: Thursday, February 25, 2010 12:44 PM
> To: Howland Craig D (Craig)
> Cc: Newlib
> Subject: Re: Use of _XOPEN_SOURCE?
>
> I'm thinking this might be better situated in sys/features.h at the
> bottom and then have sys/config.h include sys/features.h or
> alternatively still have sys/config.h include sys/features.h before this
>
> check.  This would be along the lines of glibc where features.h is used
> everywhere.
>
> -- Jeff J.