Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!think.com!hsdndev!husc6!endor!siegel
From: siegel@endor.uucp (Rich Siegel)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Another THINK Pascal gotcha - "With" instance vars
Message-ID: <5479@husc6.harvard.edu>
Date: 26 Jan 91 01:58:52 GMT
References: <1991Jan25.233122.2825@fennel.cc.uwa.oz.au>
Sender: news@husc6.harvard.edu
Reply-To: siegel@endor.UUCP (Rich Siegel)
Organization: Symantec Language Products Group
Lines: 30

In article <1991Jan25.233122.2825@fennel.cc.uwa.oz.au> a_dent@fennel.cc.uwa.oz.au writes:
>I found another way to crash Think Object Pascal applications!!!
>
>In the manual, they warn against passing instance variables by reference, as
>they may move by the time the called routine returns.  This is a very easy trap
>to fall into, despite the warning.
>
>They DIDN'T extend the warning to cover the "with" statement.

	Sorry. :-) I'll see that it gets into the doc.

	Also, calling New( ) for an instance variable is a good way to
crash, since it involves taking the address of the instance variable. This
will be fixed in the next version of the compiler...

>I suspect that the THINK environment does a lot of locking of objects behind
>the scenes so this one probably also qualifies as a "only crashes compiled
>applications" scenario.

	In fact, the debugger does absolutely nothing "behind the scenes";
crashes like this are usually purely random.

R.



 Rich Siegel	Symantec Languages Group  Internet: siegel@endor.harvard.edu

"...she's dressed in yellow, she says 'Hello, come sit next to me, you
fine fellow..."