On Wed, 19 Mar 2014, Michael Kerrisk (man-pages) wrote:
> On Wed, Mar 19, 2014 at 2:48 PM, Robert P. J. Day <rpjday@xxxxxxxxxxxxxx> wrote:
> >
> > last quibble for the day ... perusing the feature test macros
> > related to XPG and XPG XSI in features.h, starting with the comment:
> >
> > _XOPEN_SOURCE Includes POSIX and XPG things. Set to 500 if
> > Single Unix conformance is wanted, to 600 for the
> > sixth revision, to 700 for the seventh revision.
> >
> > ok, fair enough, and if we read further, we see the explanation of the
> > associated __USE macros:
> >
> > __USE_XOPEN2K Define XPG6 things.
> > __USE_XOPEN2KXSI Define XPG6 XSI things.
> > __USE_XOPEN2K8 Define XPG7 things.
> > __USE_XOPEN2K8XSI Define XPG7 XSI things.
> >
> > which *suggests* that those represent distinct use definitions.
>
> Yes, they are. Translate the above parlance as follows
>
> XPG == POSIX Base specification
> XSI == POSIX base specification + XSI extension
> (Since I know you have it, see also TLPI pages 14, 15, and 61ff)
>
> > but
> > reading further:
> >
> > #ifdef _XOPEN_SOURCE
> > # define __USE_XOPEN 1
> > # if (_XOPEN_SOURCE - 0) >= 500
> > # define __USE_XOPEN_EXTENDED 1
> > # define __USE_UNIX98 1
> > # undef _LARGEFILE_SOURCE
> > # define _LARGEFILE_SOURCE 1
> > # if (_XOPEN_SOURCE - 0) >= 600
> > # if (_XOPEN_SOURCE - 0) >= 700
> > # define __USE_XOPEN2K8 1
> > # define __USE_XOPEN2K8XSI 1
> > # endif
> > # define __USE_XOPEN2K 1
> > # define __USE_XOPEN2KXSI 1
> >
> > it seems clear that, based on the value of _XOPEN_SOURCE, you get
> > either both of the related __USE macros, or neither of them. as in,
> > based on _XOPEN_SOURCE, you'll get both of these defined:
> >
> > # define __USE_XOPEN2K 1
> > # define __USE_XOPEN2KXSI 1
>
> But note that there is also:
>
> #if (_POSIX_C_SOURCE - 0) >= 200112L
> # define __USE_XOPEN2K 1
> ...
> #endif
>
> So, __USE_XOPEN2K might be set when __USE_XOPEN2KXSI is not.
ah, that's that bit i missed, thanks. so many variables ...
rday
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Robert P. J. Day Ottawa, Ontario, CANADA
http://crashcourse.ca
Twitter: http://twitter.com/rpjday
LinkedIn: http://ca.linkedin.com/in/rpjday
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