From owner-freebsd-hackers  Wed Sep 20 14:59:24 1995
Return-Path: owner-hackers
Received: (from root@localhost)
          by freefall.freebsd.org (8.6.12/8.6.6) id OAA01377
          for hackers-outgoing; Wed, 20 Sep 1995 14:59:24 -0700
Received: from mpp.minn.net (mpp.Minn.Net [204.157.201.242])
          by freefall.freebsd.org (8.6.12/8.6.6) with ESMTP id OAA01360
          for <hackers@freefall.freebsd.org>; Wed, 20 Sep 1995 14:59:17 -0700
Received: (from mpp@localhost) by mpp.minn.net (8.6.11/8.6.9) id QAA12896; Wed, 20 Sep 1995 16:58:45 -0500
From: Mike Pritchard <mpp@mpp.minn.net>
Message-Id: <199509202158.QAA12896@mpp.minn.net>
Subject: Re: Coding style ( was Re: why is this not a bug in namei?)
To: terry@lambert.org (Terry Lambert)
Date: Wed, 20 Sep 1995 16:58:44 -0500 (CDT)
Cc: terry@lambert.org, nate@rocky.sri.MT.net, davidg@root.com,
        hackers@freefall.freebsd.org
In-Reply-To: <199509201711.KAA01075@phaeton.artisoft.com> from "Terry Lambert" at Sep 20, 95 10:11:52 am
X-Mailer: ELM [version 2.4 PL24 ME7a]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Content-Length: 1243      
Sender: owner-hackers@FreeBSD.org
Precedence: bulk

Terry Lambert wrote:
> 
> Why not:
> 
> 		XXX_LOCK();
> 		...
> 		if (error_condition) {
> 			error = EWHATEVER;
> 			goto err_with_lock_held;
> 		}
> 		...
> 	err_with_lock_held:
> 		XXX_UNLOCK():
> 	err:
> 		return (error);
> 
> Or better yet:
> 
> 		XXX_LOCK();
> 		...
> 		if (error_condition) {
> 			error = EWHATEVER;
> 		} else {
> 			...
> 		}
> 		XXX_UNLOCK():
> 	err:
> 		return (error);
> 
> I don't understand the need for the local lock state variable in your
> second example.

My previous example was very simplistic.  Having to lock multiple objects 
during a function wasn't not uncommon.
E.g.

	XXX_LOCK();
	...
	if (error_condition) {
		XXX_UNLOCK();
		return (EWHATEVER);
	}
	...
	XXX_UNLOCK();
	...
	if (error_condition2)
		return (EHWATEVER);
	...
	YYY_LOCK();
	...
	if (error_condition2) {
		YYY_UNLOCK();
		return (EWHATEVER);
	}
	...
	YYY_UNLOCK();
	return (0);

In the above example, with gotos you would need 4 exit points:  1 for 
an exit without any error.  And one each for each of the 3 error 
conditions, since they all have different requirements.  2 of them have
different locks, and 1 has no locks at all.
-- 
Mike Pritchard
mpp@mpp.minn.net
"Go that way.  Really fast.  If something gets in your way, turn"