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| From | Keith Thompson <kst-u@mib.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Extending C with GC? |
| Date | 2016-08-01 15:03 -0700 |
| Organization | None to speak of |
| Message-ID | <ln1t284065.fsf@kst-u.example.com> (permalink) |
| References | <60b33d17-71b7-4ecf-a821-dc641e2673ba@googlegroups.com> <lninvl5sjx.fsf@kst-u.example.com> <87bn1cxrqp.fsf@news.bourguet.org> <lnlh0g46hk.fsf@kst-u.example.com> <8737moxj9o.fsf@news.bourguet.org> |
Jean-Marc Bourguet <jm@bourguet.org> writes:
> Keith Thompson <kst-u@mib.org> writes:
[...]
>> Offsetting by a negative value is perfectly valid if the result still
>> points into the same object.
>
> In the context of a GC, I was thinking of negatively offsetting the result
> of malloc() or equivalent. It will confuse even the GC which can keep
> alive a block with any pointer pointing inside it.
That has undefined behavior as far as the C standard is concerned (just
computing `ptr-1`, for example, even if it's not used or dereferenced).
Once you've done that, even assuming nothing crashes, you no longer have
a pointer to the allocated memory and it's perfectly reasonable for a GC
system to relcaim it.
On the other hand, it might be reasonable in system-specific code to
peek at memory before the beginning of a malloc()ed block -- but then
you should still keep a copy of the original pointer returned by
malloc().
>> As for positive offsets, I can imagine
>> that something like:
>>
>> unsigned char *ptr = malloc(1024);
>> assert(ptr != NULL);
>> ptr += 32;
>>
>> might cause headaches for a GC system. (I don't know whether it does so
>> in practice.)
>
> I've seen both cases. Obviously p += 2048 confuse everything I've heard
> of.
Again, that has undefined behavior.
--
Keith Thompson (The_Other_Keith) kst-u@mib.org <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
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Extending C with GC? luser droog <luser.droog@gmail.com> - 2016-07-31 15:31 -0700
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-07-31 15:52 -0700
Re: Extending C with GC? Tim Rentsch <txr@alumni.caltech.edu> - 2016-07-31 17:21 -0700
Re: Extending C with GC? Jean-Marc Bourguet <jm@bourguet.org> - 2016-08-01 20:34 +0200
Re: Extending C with GC? supercat@casperkitty.com - 2016-08-01 12:14 -0700
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-01 12:46 -0700
Re: Extending C with GC? "James R. Kuyper" <jameskuyper@verizon.net> - 2016-08-01 15:56 -0400
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-01 14:28 -0700
Re: Extending C with GC? Jean-Marc Bourguet <jm@bourguet.org> - 2016-08-01 23:37 +0200
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-01 15:03 -0700
Re: Extending C with GC? jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-02 00:11 +0200
Re: Extending C with GC? "James R. Kuyper" <jameskuyper@verizon.net> - 2016-08-01 18:19 -0400
Re: Extending C with GC? BGB <cr88192@hotmail.com> - 2016-08-02 12:46 -0500
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-03 15:26 -0700
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-03 15:49 -0700
Re: Extending C with GC? Ian Collins <ian-news@hotmail.com> - 2016-08-04 14:07 +1200
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-03 19:26 -0700
Re: Extending C with GC? Ian Collins <ian-news@hotmail.com> - 2016-08-04 14:55 +1200
Re: Extending C with GC? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-03 20:38 -0700
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-04 05:10 -0700
Re: Extending C with GC? Siri Cruise <chine.bleu@yahoo.com> - 2016-08-04 05:57 -0700
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-04 06:13 -0700
Re: Extending C with GC? Ian Collins <ian-news@hotmail.com> - 2016-08-05 07:24 +1200
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-04 12:47 -0700
Re: Extending C with GC? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-04 23:32 -0700
Re: Extending C with GC? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-05 10:09 +0100
Re: Extending C with GC? Ian Collins <ian-news@hotmail.com> - 2016-08-05 20:32 +1200
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-05 06:14 -0700
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-06 04:14 -0700
Re: Extending C with GC? Melzzzzz <mel@zzzzz.com> - 2016-08-06 13:23 +0200
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-06 04:38 -0700
Re: Extending C with GC? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-06 04:34 -0700
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-06 05:28 -0700
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-06 06:05 -0700
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-06 06:12 -0700
Re: Extending C with GC? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-06 14:02 +0100
Re: Extending C with GC? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-06 06:11 -0700
Re: Extending C with GC? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-06 14:50 +0100
Re: Extending C with GC? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-06 07:57 -0700
Re: Extending C with GC? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-06 17:02 +0100
Re: Extending C with GC? jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-06 19:20 +0200
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-06 14:27 +0100
Re: Extending C with GC? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-06 14:45 +0100
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-06 09:59 -0700
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-06 19:38 +0100
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-06 17:03 -0700
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-07 09:54 +0100
Re: Extending C with GC? Ian Collins <ian-news@hotmail.com> - 2016-08-07 21:53 +1200
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-07 11:34 +0100
Re: Extending C with GC? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-08-07 12:06 +0000
Re: Extending C with GC? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-07 14:10 +0100
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-07 15:38 +0100
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-07 14:32 -0700
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-07 23:44 +0100
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-07 16:12 -0700
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-08 01:42 +0100
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-07 18:56 -0700
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-08 10:20 +0100
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-08 09:39 -0700
Re: Extending C with GC? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-08 02:30 +0100
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-07 20:15 +0100
Re: Extending C with GC? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-08 01:24 +0100
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-08 02:08 +0100
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-07 18:49 -0700
Re: Extending C with GC? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-08 03:28 +0100
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-08 12:14 +0100
Re: Extending C with GC? Ian Collins <ian-news@hotmail.com> - 2016-08-08 07:37 +1200
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-07 20:56 +0100
Re: Extending C with GC? Ian Collins <ian-news@hotmail.com> - 2016-08-08 08:11 +1200
Re: Extending C with GC? Melzzzzz <mel@zzzzz.com> - 2016-08-07 22:19 +0200
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-07 22:23 +0100
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-07 14:29 -0700
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-07 22:36 +0100
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-07 15:04 -0700
Re: Extending C with GC? jameskuyper@verizon.net - 2016-08-07 15:19 -0700
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-08 00:04 +0100
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-07 16:20 -0700
Re: Extending C with GC? Ian Collins <ian-news@hotmail.com> - 2016-08-08 15:21 +1200
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-08 10:35 +0100
Re: Extending C with GC? Gareth Owen <gwowen@gmail.com> - 2016-08-08 18:13 +0100
Re: Extending C with GC? supercat@casperkitty.com - 2016-08-08 11:53 -0700
Re: Extending C with GC? raltbos@xs4all.nl (Richard Bos) - 2016-08-10 12:58 +0000
Re: Extending C with GC? supercat@casperkitty.com - 2016-08-10 07:05 -0700
Re: Extending C with GC? Ken Brody <kenbrody@spamcop.net> - 2016-08-10 12:29 -0400
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-08 21:15 +0100
Re: Extending C with GC? supercat@casperkitty.com - 2016-08-08 08:57 -0700
Re: Extending C with GC? luser droog <luser.droog@gmail.com> - 2016-08-07 15:37 -0700
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-07 14:58 -0700
Re: Extending C with GC? Ian Collins <ian-news@hotmail.com> - 2016-08-08 15:26 +1200
Re: Extending C with GC? jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-08 10:26 +0200
Re: Extending C with GC? Ian Collins <ian-news@hotmail.com> - 2016-08-08 21:13 +1200
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-08 10:41 +0100
Re: Extending C with GC? jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-08 12:00 +0200
Re: Extending C with GC? Ian Collins <ian-news@hotmail.com> - 2016-08-08 22:07 +1200
Re: Extending C with GC? David Brown <david.brown@hesbynett.no> - 2016-08-08 12:57 +0200
Re: Extending C with GC? Gareth Owen <gwowen@gmail.com> - 2016-08-08 18:12 +0100
Re: Extending C with GC? Ian Collins <ian-news@hotmail.com> - 2016-08-08 21:25 +1200
Re: Extending C with GC? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-08 02:57 -0700
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-07 13:28 -0700
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-07 05:42 -0700
Re: Extending C with GC? Florian Weimer <fw@deneb.enyo.de> - 2016-08-07 11:49 +0200
Re: Extending C with GC? jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-06 19:18 +0200
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-06 12:35 -0700
Re: Extending C with GC? jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-06 19:27 +0200
Re: Extending C with GC? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-06 10:55 -0700
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-06 12:31 -0700
Re: Extending C with GC? James Kuyper <jameskuyper@verizon.net> - 2016-08-03 22:36 -0400
Re: Extending C with GC? David Brown <david.brown@hesbynett.no> - 2016-08-04 10:57 +0200
Re: Extending C with GC? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-04 04:09 -0700
Re: Extending C with GC? David Brown <david.brown@hesbynett.no> - 2016-08-04 14:01 +0200
Re: Extending C with GC? supercat@casperkitty.com - 2016-08-04 07:52 -0700
Re: Extending C with GC? Tim Rentsch <txr@alumni.caltech.edu> - 2016-08-04 08:57 -0700
Re: Extending C with GC? supercat@casperkitty.com - 2016-08-04 09:19 -0700
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-04 12:30 -0700
Re: Extending C with GC? supercat@casperkitty.com - 2016-08-04 15:21 -0700
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-04 16:50 -0700
Re: Extending C with GC? supercat@casperkitty.com - 2016-08-05 07:31 -0700
Re: Extending C with GC? Tim Rentsch <txr@alumni.caltech.edu> - 2016-08-05 16:01 -0700
Re: Extending C with GC? jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-04 21:00 +0200
Re: Extending C with GC? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-04 20:26 +0100
Re: Extending C with GC? jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-05 10:37 +0200
Re: Extending C with GC? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-05 15:52 +0100
Re: Extending C with GC? antispam@math.uni.wroc.pl - 2016-08-21 00:09 +0000
Re: Extending C with GC? Gareth Owen <gwowen@gmail.com> - 2016-08-21 08:58 +0100
Re: Extending C with GC? jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-21 10:48 +0200
Re: Extending C with GC? "Pascal J. Bourguignon" <pjb@informatimago.com> - 2016-08-21 19:58 +0200
Re: Extending C with GC? supercat@casperkitty.com - 2016-08-22 08:46 -0700
Re: Extending C with GC? Öö Tiib <ootiib@hot.ee> - 2016-08-26 02:24 -0700
Re: Extending C with GC? supercat@casperkitty.com - 2016-08-26 13:37 -0700
Re: Extending C with GC? Melzzzzz <mel@zzzzz.com> - 2016-08-27 00:41 +0200
Re: Extending C with GC? Öö Tiib <ootiib@hot.ee> - 2016-08-28 06:12 -0700
Re: Extending C with GC? BartC <bc@freeuk.com> - 2016-08-05 10:06 +0100
Re: Extending C with GC? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-05 15:26 +0100
Re: Extending C with GC? Tim Rentsch <txr@alumni.caltech.edu> - 2016-08-05 08:11 -0700
Re: Extending C with GC? jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-05 17:43 +0200
Re: Extending C with GC? Tim Rentsch <txr@alumni.caltech.edu> - 2016-08-05 15:28 -0700
Re: Extending C with GC? BGB <cr88192@hotmail.com> - 2016-08-04 17:11 -0500
Re: Extending C with GC? Tim Rentsch <txr@alumni.caltech.edu> - 2016-07-31 17:35 -0700
Re: Extending C with GC? jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-01 07:45 +0200
Re: Extending C with GC? Keith Thompson <kst-u@mib.org> - 2016-08-01 08:49 -0700
Re: Extending C with GC? supercat@casperkitty.com - 2016-08-01 09:06 -0700
Re: Extending C with GC? Aleksandar Kuktin <akuktin@gmail.com> - 2016-08-05 18:11 +0000
Re: Extending C with GC? luser droog <luser.droog@gmail.com> - 2016-08-05 11:24 -0700
Re: Extending C with GC? "Chris M. Thomasson" <invalid@invalid.invalid> - 2016-08-08 22:12 -0700
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