Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!brutus.cs.uiuc.edu!apple!usc!ucsd!ucbvax!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.sys.mac.programmer
Subject: Re: ARRGH (Strings and things)
Message-ID: <8852@hoptoad.uucp>
Date: 31 Oct 89 02:33:32 GMT
References: <16004@netnews.upenn.edu> <8835@hoptoad.uucp> <16420@dartvax.Dartmouth.EDU>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Organization: Eclectic Software, San Francisco
Lines: 26

In article <8835@hoptoad.uucp>, tim@hoptoad.uucp (Tim Maroney) writes:
> BlockMove doesn't touch the heap so it's safe to use this dereference
> even when mystringhandle is unlocked or purgeable (but not purged!)

In article <16420@dartvax.Dartmouth.EDU> Jim.Matthews@dartmouth.edu writes:
>A paranoid note: BlockMove doesn't move memory, but since it's an OS trap
>most compilers get to it through glue. If that glue is in an unloaded
>segment, then the act of *calling* BlockMove will move memory.

Excellent point.

>The moral: watch out for traps that require glue or put the glue in a 
>segment that is never unloaded.

I get a different moral out of this -- don't unload segments.  I use so
many function pointers in my code that it's impossible anyway, so I
don't have this problem.  As far as I'm concerned, UnloadSeg was
relevant only to the Mac 128K....

Another moral -- if you *do* unload segments, then link your glue
routines into the main code segment, so they will never be unloaded.
-- 
Tim Maroney, Mac Software Consultant, sun!hoptoad!tim, tim@toad.com

These are not my opinions, those of my ex-employers, my old schools, my
relatives, my friends, or really any rational person whatsoever.