Re: Effect of CPP tags

From	Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups	comp.lang.c
Subject	Re: Effect of CPP tags
Date	2024-01-20 14:29 -0800
Organization	A noiseless patient Spider
Message-ID	<86y1cjiqpu.fsf@linuxsc.com> (permalink)
References	(1 earlier) <umk836$ehn5$1@dont-email.me> <4434vmp2fl.fsf@be-well.ilk.org> <87wmsyuj1l.fsf@nosuchdomain.example.com> <20231228134234.49@kylheku.com> <87sf3lvs43.fsf@nosuchdomain.example.com>

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Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

> [...]  Just including <unistd.h> has undefined behavior as far as
> ISO C is concerned, [...]

Not true.  The behavior of #include <unistd.h> is defined in
section 6.10.2 p2.  One of two things is true:  either the header
named is part of the implementation, or it isn't.  If the named
header is part of the implementation, then it constitutes a
language extension, and so it must be documented (and defined).
If the named header is not part of the implementation, it still
must be a header that the implementation can process (because of
the constraint in 6.10.2 p1), and it must be processed the same
way as a header that is part of the implementation (because of
how the behavior is defined in 6.10.2 p2).  Implementations are
not at liberty to do anything they want just because the header
named is not part of the implementation;  such headers must be
processed in just the same way as standard or extension headers,
no matter how it is that they happen to be in the set of places
the implementation has defined (and documented) to hold headers.

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Re: Effect of CPP tags Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-01-20 14:29 -0800
  Re: Effect of CPP tags Kaz Kylheku <433-929-6894@kylheku.com> - 2024-01-21 04:46 +0000
    Re: Effect of CPP tags James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-01-21 10:56 -0500
    Re: Effect of CPP tags James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-01-21 12:11 -0500
      Re: Effect of CPP tags Kaz Kylheku <433-929-6894@kylheku.com> - 2024-01-21 17:55 +0000
        Re: Effect of CPP tags James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-01-21 21:57 -0500
          Re: Effect of CPP tags Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-01-24 07:42 -0800

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