Re: Extending C with GC?

From	Tim Rentsch <txr@alumni.caltech.edu>
Newsgroups	comp.lang.c
Subject	Re: Extending C with GC?
Date	2016-08-05 08:11 -0700
Organization	A noiseless patient Spider
Message-ID	<kfneg63i73i.fsf@x-alumni2.alumni.caltech.edu> (permalink)
References	<60b33d17-71b7-4ecf-a821-dc641e2673ba@googlegroups.com> <lninvl5sjx.fsf@kst-u.example.com> <lnwpjx1obh.fsf@kst-u.example.com> <kfnvazgil16.fsf@x-alumni2.alumni.caltech.edu> <no03cf$560$1@dont-email.me>

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jacobnavia <jacob@jacob.remcomp.fr> writes:

> Le 04/08/2016 at 17:57, Tim Rentsch wrote :
>> To avoid dealing with ambiguous roots, the language needs to
>> operate in an environment where:  one, the type of every memory
>> cell is known (so the collector knows whether it's a pointer or
>> not);  two, pointers cannot be "disguised" so that they are
>> stored in places that the collector doesn't know about.  I think
>> it would be very hard for a C implementation to satisfy the first
>> property, and essentially impossible to satisfy the second
>> property, assuming full C is allowed.
>
> That environment can be provided by the compiler.  At each line of code
> there is the Current scope.  That scope and all other above it, contain
> data that has types, of course, and all pointers are known.  The
> compiler can generate a table of locations within the function, that
> points to the table of all valid pointers in the program and their
> addresses.
>
> Note that only the pointers marked as GC-pointers will be included in
> the tables.  All other pointers are not concerned by the GC.  The
> malloc/free system continues to work as always and you can write
> 0xdeadbeef into any of those pointers with a simple cast.
>
> GC-pointers however, are not allowed to be cast into anything else but
> a GC-pointer of (maybe) a different type.
>
> GC:
> 1) From the current frame, mark as used all pointers in the current
> function.
>
> 2) Use the stack unwind info to retrieve the calling function, mark
> those until the global scope is reached and mark all that one too.
>
> 3) Do this for each thread.
>
> 4) Unmarked memory is free.
>
> Note that the info can also be used by a debugger or the user itself
> if the language provides a run time interface.  A stack trace of the
> program
> becomes easy to do...
>
> Note that this doesn't imply ANY change to the language besides the
> introduction of the GC-interface names.

My comments were meant to be understood in the context of
standard C, ie, without any language extensions.  Any compiler
that differentiates between "GC pointers" and "non-GC pointers",
by whatever extension, is not standard C.  That is not to say
such an extension is not worth discussing, it may very well be,
but it isn't what I was talking about.

Thread

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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