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From: harald.mueller@siemenscom.com
Subject: Re: Why C++ is successful
Date: 1998/08/07
Message-ID: <6qfhri$gs7$1@nnrp1.dejanews.com>#1/1
X-Deja-AN: 378901334
References: <dewar.902415458@merv>
Organization: Deja News - The Leader in Internet Discussion
X-Article-Creation-Date: Fri Aug 07 18:42:58 1998 GMT
Newsgroups: comp.lang.eiffel,comp.object,comp.software-eng,comp.lang.ada
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Date: 1998-08-07T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <dewar.902415458@merv>,
  dewar@merv.cs.nyu.edu (Robert Dewar) wrote:
>
> Lars says
>
> <<Are you saying tht GC would introduce a larger risk for incorrect
> programs than exceptions? If so, why?
> >>
>
> Most certainly! GC introduces a huge risk for incorrect programs. Garbage
> collectors assume that the pointer structure of a program is correct. If
> it is corruptede, garbage collectors can cause horrible havoc. Indeed this
> havoc often only shows up after several mark-and-sweep type cycles of the
> GC, and it can be almost impossible to track them down
>
> (said from horrible experiences in implementing general GC!)
>

Now that's interesting. I did never write a GC, but I wrote a heap management
system, which had bugs in it for the first few weeks, and you wouldn't
believe it: A correct GC would have been MUCH BETTER than my wrong heap
management. So?

Actually, the problem with new/delete schemes is that the *user*(!!) can
corrupt the heap, e.g. by deleting stack variables:

f(C* p) {
   C defaultC;
   C* c;
   if (p == null) c = &defaultC;
   else c = p;
   ...
   ...
   ...
   delete c;
}

Similar with static class variables etc. You wouldn't believe how many heaps
silently and very late crash after such errors (which are mostly introduced
innocently during maintenance - "we dont have to create a new C all the time -
just let's have a single static one").

HMMueller

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