NetNews Usenet Archive 1993 #3/NN_1993_3.iso/spool/comp/sys/mac/programm/21939

Text File | 1993-01-22 | 1.7 KB | 36 lines

Newsgroups: comp.sys.mac.programmer
Path: sparky!uunet!elroy.jpl.nasa.gov!sdd.hp.com!nigel.msen.com!fmsrl7!destroyer!sol.ctr.columbia.edu!fnal.fnal.gov!gwatts
From: [e-mail]
Subject: Verifying valid handles, how to?
Sender: [e-mail]
Organization: Fermi National Accelerator Lab
Date: Fri, 22 Jan 1993 07:55:20 GMT
Message-ID: <[e-mail]>
Lines: 23
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NNTP-Posting-Host: sol.ctr.columbia.edu

Hi all,
  The first part is an amusing story.  The second request for help is aimed
at anyone who is good at the memory manager. :)  Everyone, right? :)
  I spent about 4 hours tracking down a but in my Think C 5.0.3 program
yesterday.  It was crazy.  My color table kept getting corrupted.  I would
never bomb in the same place.  Sometimes the "rb" command in MacsBug wouldn't
even work!  I had icons explode into little dots.
  Turns out (sheepish grin) I was deleteing an object twice. :)
  At any rate, I was thinking.  I've got only indirect objects in my project.
This means every object is a handle, right?  Well, why not, in the debug
version of the message dispatcher (oopDebug library) put a little code that
will check the object is infact allocated as a handle?
  I checked out the routine in msg.c (in the oops Libraries folder), and
the handle is stored in register a1.  I don't know, however, how to check
if it is a valid handle without causing an error (bus or otherwise) of
somesort.  Especially if it is a random number!  Anyone know?  Is there
some memory manager routine, given a suspected handle, will tell me this?
  By the way -- I do zero all objects after I delete them.  This case was
a little more subtle than that (so don't yell at me :)).

    Cheers,
        Gordon.