Date: Fri, 20 Oct 2006 00:00:44 GMT From: Bruce Evans <bde@zeta.org.au> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/104436: [PATCH] sys/sem.h should include sys/types.h Message-ID: <200610200000.k9K00ib7099403@freefall.freebsd.org>
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The following reply was made to PR kern/104436; it has been noted by GNATS.
From: Bruce Evans <bde@zeta.org.au>
To: John Baldwin <jhb@FreeBSD.org>
Cc: Cheng-Lung Sung <clsung@FreeBSD.org>, FreeBSD-gnats-submit@FreeBSD.org
Subject: Re: kern/104436: [PATCH] sys/sem.h should include sys/types.h
Date: Fri, 20 Oct 2006 09:54:11 +1000 (EST)
On Thu, 19 Oct 2006, John Baldwin wrote:
> On Tuesday 17 October 2006 20:09, Bruce Evans wrote:
>> I did a quick review of symbols in sys/sem.h:
>> - POSIX seems to overspecify the representation: "A semaphore shall be
>> respresented by an anonymous struct containing the following members:"
>> [semval, sempid, semncnt, semzcnt]". FreeBSD doesn't declare any of
>> these struct members.
>
> It does, but 'struct sem' is private to kern/sysv_sem.c:
>
> struct sem {
> u_short semval; /* semaphore value */
> pid_t sempid; /* pid of last operation */
> u_short semncnt; /* # awaiting semval > cval */
> u_short semzcnt; /* # awaiting semval = 0 */
> };
This is kernel-only (but only has semval and sempid) in Linux-2.6.10
too, so its visibility in FreeBSD seems to be OK.
>> - FreeBSD declares several things that aren't required by POSIX and uses
>> bad names for most of these. The worst ones are the struct member
>> names `val', `buf' and `array'. POSIX cannot reserve these, and sem.h
>> mostly uses a `sem' prefix to avoid such pollution. These seem to be
>> implementation details that don't belong in the header anyway.
>
> Hmm the 'semun' union is actually passed as an arg to semctl() and the names
> it uses seem to be standard as Linux, etc. use the same name.
It is actually in POSIX, but at least in the old 2001 draft 7 that I
looked at, it is only described under semctl() and is not mentioned under
sem.h.
Bruce
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