From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Thread: 103376,80bc3e0698be468f
X-Google-Attributes: gid103376,public
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!news1.google.com!news4.google.com!border1.nntp.dca.giganews.com!nntp.giganews.com!newsfeed00.sul.t-online.de!newsfeed01.sul.t-online.de!t-online.de!newsfeed.vmunix.org!peer-uk.news.demon.net!kibo.news.demon.net!mutlu.news.demon.net!news.demon.co.uk!demon!not-for-mail
From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Type safety on wikipedia
Date: Fri, 27 Jan 2006 19:50:49 +0000
Organization: Pushface
Message-ID: <m2y811fo12.fsf@grendel.local>
References: <1138260496.230283.147640@g43g2000cwa.googlegroups.com>
 <1138283608.433842.76060@z14g2000cwz.googlegroups.com>
 <43D8E85C.6020805@mailinator.com> <1535741.yb0A0MsH1D@linux1.krischik.com>
 <43D912A3.2030201@mailinator.com> <m2bqxyhgi5.fsf@grendel.local>
 <11271924.245PKaY7qe@linux1.krischik.com>
NNTP-Posting-Host: pogner.demon.co.uk
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
X-Trace: news.demon.co.uk 1138391450 3117 62.49.19.209 (27 Jan 2006 19:50:50
 GMT)
X-Complaints-To: abuse@demon.net
NNTP-Posting-Date: Fri, 27 Jan 2006 19:50:50 +0000 (UTC)
Cancel-Lock: sha1:gQn8BxbHCqma9BR8hTIbno3zISo=
User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.0.50 (darwin)
Xref: g2news1.google.com comp.lang.ada:2688
Date: 2006-01-27T19:50:49+00:00
List-Id: <comp.lang.ada>

Martin Krischik <krischik@users.sourceforge.net> writes:

> Simon Wright wrote:
>
>> "Alex R. Mosteo" <devnull@mailinator.com> writes:
>> 
>>> This is something I've mused about sometimes: Let's suppose some Ada
>>> compiler goes ahead and provides a GC. What happens with programs
>>> written without taking this into account?
>> 
>> 13.11.2(17) only says that Free _should_ reclaim the storage. I
>> suppose for a GC implementation there could be at least 2
>> implementation strategies:
>> 
>>  * don't actually reclaim, just remove local reference and deal with
>>    tasks if necessary
>>
>>  * check that the reference count is in fact 1 and raise *_Error if
>>    not! That would be useful!
>
> That is indeed interesting. Up until now I have implemented the interface to
> the bohem-weiser collector as such that memory is reclaimed. Being German I
> did not spot the true meaning of should. I might reconsider the
> implementation.

I was imagining that GC and Free might be independent, so that (modulo
tasks and finalization) Free would only have to null the pointer and
GC would magically see later that the memory was no longer
referenced. I think the collector you're working on s more
cooperative?

I think that a dangling pointer is only a _potential_ deathtrap, so my
second suggestion is perhaps a bit over the top. On the other hand, in
safety-related systems one would prefer to avoid even the possibility
...