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Date: Mon, 31 Dec 2001 12:39:12 -0800 (PST)
From: John Baldwin <jhb@FreeBSD.org>
To: Poul-Henning Kamp <phk@critter.freebsd.dk>
Subject: Re: cvs commit: src/share/man/man3 queue.3
Cc: cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org,
	Julian Elischer <julian@FreeBSD.org>, Greg Lehey <grog@FreeBSD.org>
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On 30-Dec-01 Poul-Henning Kamp wrote:
> In message <20011230094936.K90696@monorchid.lemis.com>, Greg Lehey writes:
>>On Saturday, 29 December 2001 at  8:55:05 +0100, Poul-Henning Kamp wrote:
>>> In message <200112282200.fBSM0Rw61760@freefall.freebsd.org>, Julian
>>> Elischer wr
>>> ites:
>>>> julian      2001/12/28 14:00:27 PST
>>>>
>>>>  Modified files:
>>>>    share/man/man3       queue.3
>>>>  Log:
>>>>  Document some behaviour I'm depending on.
>>>>  (TAILQ_FOREACH leaves the variable NULL if there were no more to do)
>>>
>>> I don't like this.
>>
>>Do you have a reason for not liking it?
> 
> Yes, I don't like statements with weird sideeffects.  If julian
> wants the sideeffect, he should not use a _FOREACH() macro to hide
> the internals of the loop.
> 
> _FOREACH() is for the plain & simple traversal of a queue(3) stucture,
> anything more should explicitly state intent.

I would agree except for code like this:

        TAILQ_FOREACH(p, &list, p_next)
                if (some_test_on(p))
                        break;
        if (p != NULL) {
                /* Found one, now do something. */
        }

You could work around this via a goto instead I suppose:

        TAILQ_FOREACH(p, &list, p_next)
                if (some_test_on(p))
                        goto found;
        goto not_found
found:
        /* Do something */
not_found:

But that's uglier IMO.

-- 

John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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