Path: utzoo!mnetor!uunet!husc6!tut.cis.ohio-state.edu!morganucodon.cis.ohio-state.edu!paul
From: paul@morganucodon.cis.ohio-state.edu (Paul Placeway)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Pointer arithmetic in C w/ or w/o locked handles
Message-ID: <10897@tut.cis.ohio-state.edu>
Date: 18 Apr 88 19:43:37 GMT
References: <1988Apr15.125337.100@mntgfx.mentor.com>
Sender: news@tut.cis.ohio-state.edu
Organization: The Ohio State University Dept of Computer and Information Science
Lines: 24
Keywords: pointer C arithmetic handles

In article <1988Apr15.125337.100@mntgfx.mentor.com> tomc@mntgfx.mentor.com (Tom Carstensen) writes:
<     ...

<     HUnlock(hdl);
<     length = (long) (ptr - *hdl);
< ...
< If I move the length calculation before I unlock the 
< handle, then length becomes 8, and I'm ok.

I would be _really_ supprised if something like this continued to work
correctly (assuming that it does allready; which it seems not to).

Personally, I wouldn't HUnlock the handle until you are done with it
(ie. _after_ the length calculation).  It is possible (although currently
unlikely) that the block that the handle points to could be moved
between the HUnlock and the last derefrence.  Race conditions like this
should be avoided -- they create bugs without adding any benifit.

		-- Paul Placeway
-=-
Existence is beyond the power of words
To define:
Terms may be used
But are none of them absolute.