Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!nrl-cmf!ames!amdahl!uunet!hodge!pnet06!thecloud
From: thecloud@pnet06.cts.com (Ken Mcleod)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Question on Handle locking example
Message-ID: <5972@hodge.UUCP>
Date: 28 Jan 89 10:17:19 GMT
Sender: root@hodge.UUCP
Organization: People-Net [pnet06], Orange, CA
Lines: 25


 uucibg@sw1e.UUCP ([5-3929] Brian Gilstrap) writes:
>
>I'm not clear on why function 'a' below would die.  This was posted recently
>as an example of how not to code.  I'm sure I'm missing something extremely
>obvious (it's late...), but please explain....

>a()
>{
>       HLock(h);
>       b(h);
>       *h->x = ...     /* this would not survive a heap scramble */
>       HUnlock(h);
>}

  The 'obvious' portion was in function 'b', which unlocked the handle 'h'
before returning. Therefore, at the time h is dereferenced, the handle
is unlocked! There's nothing wrong with function 'a' as posted above,
which was the whole moral of this story: watch your HLock's and HUnlock's
very carefully!

==========    .......    ===================================   ============
Ken McLeod   :.     .:   UUCP: {crash uunet}!pnet06!thecloud   "They mean
----------  :::.. ..:::  InterNet: thecloud@pnet06.cts.com      to win
!(C)1988       ////            or thecloud@dhw68k.cts.com       Wimbledon!"