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Date: Mon, 30 Jul 2001 13:20:01 -0700 (PDT)
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From: Jeroen Ruigrok/Asmodai <asmodai@wxs.nl>
Subject: Re: docs/26003: getgroups(2) lists NGROUPS_MAX but not syslimits.h
Reply-To: Jeroen Ruigrok/Asmodai <asmodai@wxs.nl>
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The following reply was made to PR docs/26003; it has been noted by GNATS.

From: Jeroen Ruigrok/Asmodai <asmodai@wxs.nl>
To: Bruce Evans <bde@zeta.org.au>
Cc: Robert Watson <rwatson@FreeBSD.org>, dd@FreeBSD.org,
	freebsd-doc@FreeBSD.org, bde@FreeBSD.org,
	FreeBSD Gnats <freebsd-gnats-submit@freebsd.org>
Subject: Re: docs/26003: getgroups(2) lists NGROUPS_MAX but not syslimits.h
Date: Mon, 30 Jul 2001 22:01:47 +0200

 -On [20010401 13:00], Bruce Evans (bde@zeta.org.au) wrote:
 >On Sat, 31 Mar 2001, Robert Watson wrote:
 >
 >> Dunno -- I guess this leads to a number of questions of specification-land
 >> -- is NGROUPS_MAX supposed to be exposed to the application, if so, how
 >> should the application go about including things to get the value, etc. 
 >> Bruce might have a good answer, if not a correct one, so I've CC'd him
 >> :-). 
 >
 >In POSIX.1-1996:
 >
 >1) NGROUPS_MAX is defined in <limits.h>.  (<sys/syslimits.h> is BSD
 >   implementation detail, so it shouldn't be documented.)
 >
 >2) NGROUPS_MAX is a "Run-Time Increasable Value".  This means that
 >   applications may find that the actual maximum number of groups is
 >   larger than their compile time value of NGROUPS_MAX.  The run time
 >   maximum is given by sysconf(_SC_NGROUPS_MAX).
 >
 >3) Unlike some other POSIX limits, NGROUPS_MAX must be defined at
 >   compile time, although its value is almost useless if its run time
 >   value is larger.  A footnote says that future revisions of POSIX.1
 >   are expected to permit omitting the definition of NGROUPS_MAX from
 >   <limits.h> to indicate that its value is variable.
 
 Latest POSIX draft specifies:
 
 SYNOPSIS
 	#include <unistd.h>
 
 	int getgroups(int gidsetsize, gid_t grouplist[]);
 
 [...]
 
 Applications writers should note that {NGROUPS_MAX} is not
 necessarily a constant on all implementations.
 
 [...]
 
 Issue 6
 	In the SYNOPSIS, the optional include of the <sys/types.h>
 	header is removed.
 
 	The following new requirements on POSIX implementations derive
 	from alignment with the Single UNIX Specification:
 
 	  · The requirement to include <sys/types.h> has been removed.
 	    Although <sys/types.h> was required for conforming
 	    implementations of previous POSIX specifications, it was not
 	    required for UNIX applications.
 	  · A return value of 0 is not permitted, because {NGROUPS_MAX}
 	    cannot be 0. This is a FIPS requirement.
 
 -- 
 Jeroen Ruigrok van der Werven/Asmodai asmodai@[wxs.nl|freebsd.org|xmach.org]
 Documentation nutter/C-rated Coder, finger asmodai@ninth-circle.dnsalias.net
 http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/
 The human race is challenged more than ever before to demonstrate our
 mastery -- not over nature but of ourselves...
 

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