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From: egw%weaks@lanl.gov (Eric Wasserman)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Think C Objects in motion???
Message-ID: <63234@lanl.gov>
Date: 18 Sep 90 01:23:17 GMT
Sender: news@lanl.gov
Organization: LANL
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References:<1990Sep14.105646.23614@cunixf.cc.columbia.edu> <6988@dog.ee.lbl.gov>

In article <6988@dog.ee.lbl.gov> beard@ux5.lbl.gov (Patrick C Beard) 
writes:

With regard to objects in Think C:

> 2.  Objects are handles, not pointers, and therefore have to be treated
> with kindness.  The rule is, don't assign into an object's fields if
> the rhs of the assignment can move memory.

Actually this is not the case in which instance variables are a problem.  
Page 192 of the Think C manual states:  "It is OK to assign values to
instance variables, even when the expression on the right hand side may
move memory."  In Think C the rhs is evaluated first (including any 
memory shuffling) and THEN the handle reference on the lhs is evaluated.

The real problem is passing the address of an instance variable to a
routine which may move memory.  There is an example of this in the same
page in the Think C manual.

I hope this helps.

Eric Wasserman