Re: Sugestions for runtime polymorphism

From	David Brown <david.brown@hesbynett.no>
Newsgroups	comp.lang.c
Subject	Re: Sugestions for runtime polymorphism
Date	2016-09-28 21:29 +0200
Organization	A noiseless patient Spider
Message-ID	<nsh5lu$il5$1@dont-email.me> (permalink)
References	(17 earlier) <ns67c3$25n$1@dont-email.me> <87h995f4lm.fsf@bsb.me.uk> <ns89ok$lj2$1@dont-email.me> <87lgyfepnc.fsf@bsb.me.uk> <kfnvaxgaz66.fsf@x-alumni2.alumni.caltech.edu>

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On 28/09/16 16:15, Tim Rentsch wrote:
> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
>
>> David Brown <david.brown@hesbynett.no> writes:
>> [discussing a particular case of gcc behavior w.r.t. effective
>>   type rules]
>>
>>> Maybe it's time to pass this on to the gcc mailing lists, and ask
>>> how they interpret it?
>>
>> That would be interesting.  It's obviously a long-standing
>> optimisation, but I don't see on what basis it is being done.

I posted to the gcc help mailing list.  I hope people here can have a 
look at the answers from the gcc community and developers, and consider 
the matter.  Maybe a defect report is the right way to go, or perhaps 
others (such as you, Tim) would like to add to the gcc thread.  The 
mailing list is on gmane as gmane.comp.gcc.help for those that prefer a 
Usenet interface to a mailing list.  You can also post to 
gcc-help@gcc.gnu.org without joining the list (the traffic is not too high).

<https://gcc.gnu.org/ml/gcc-help/2016-09/msg00087.html>


>
> I am hoping not to be involved in this discussion too deeply, but
> would like to make a few remarks.
>
> I agree with your conclusion that the example code conforms to
> the letter of the Standard.  AFAICT that code satisfies the
> requirements of effective type rules (but let me emphasize,
> as I read what the words say, which may not be the same as
> what is meant).
>
> I too would like to see this case (perhaps with simpler code)
> submitted as a gcc bug report (and maybe also mailing lists,
> but IMO an official response is important).
>
> A response to a bug report might be either "yes this is a bug and
> we will fix it", or might be "this isn't a bug because what the
> Standard means is X".  The second possibility occurring would
> not surprise me greatly.
>
> IMO this example also deserves filing a Defect Report.  I call it
> a defect because either the Standard doesn't mean what it says,
> which is obviously a defect, or it produces a conclusion that
> is highly surprising and probably not what some implementors
> expect.  Either way, a clarification is warranted.
>
> I wouldn't be surprised if an official committee response to a
> Defect Report reached a different conclusion about whether the
> behavior in the example code is undefined behavior.  I'm sure
> many people remember the earlier discussions, before C11 was
> done, about the phrase "may be read only to determine the value
> to be stored" (or something like that).  We now know that the
> "literal meaning" of that phrase is not what was intended.  A
> similar situation may apply in this case.  At the end of the
> day the only thing that matters is what WG14 intended, and
> the only way to be sure here is to ask them.
>

Thread

Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-14 12:01 -0700
  Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-14 13:15 -0700
  Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-14 13:27 -0700
    Re: Sugestions for runtime polymorphism Richard Heathfield <rjh@cpax.org.uk> - 2016-09-14 21:50 +0100
      Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-14 14:20 -0700
        Re: Sugestions for runtime polymorphism "James R. Kuyper" <jameskuyper@verizon.net> - 2016-09-14 17:32 -0400
          Re: Sugestions for runtime polymorphism Keith Thompson <kst-u@mib.org> - 2016-09-14 16:30 -0700
            Re: Sugestions for runtime polymorphism "James R. Kuyper" <jameskuyper@verizon.net> - 2016-09-14 17:54 -0400
          Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-14 17:34 -0700
            Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-14 17:58 -0700
              Re: Sugestions for runtime polymorphism Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-14 19:50 -0700
                Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-15 05:03 -0700
              Re: Sugestions for runtime polymorphism BartC <bc@freeuk.com> - 2016-09-15 10:43 +0100
                Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-15 05:29 -0700
                Re: Sugestions for runtime polymorphism BartC <bc@freeuk.com> - 2016-09-15 19:49 +0100
                Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-15 11:58 -0700
                Re: Sugestions for runtime polymorphism BartC <bc@freeuk.com> - 2016-09-15 20:29 +0100
                Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-15 14:00 -0700
                Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-16 07:27 -0700
                Re: Sugestions for runtime polymorphism BartC <bc@freeuk.com> - 2016-09-16 16:34 +0100
                Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-16 09:36 -0700
                Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-20 12:59 -0700
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-20 14:08 -0700
                Re: Sugestions for runtime polymorphism Ian Collins <ian-news@hotmail.com> - 2016-09-21 15:53 +1200
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-21 07:38 -0700
                Re: Sugestions for runtime polymorphism Ian Collins <ian-news@hotmail.com> - 2016-09-23 09:12 +1200
                Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-21 05:26 -0700
                Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-21 05:35 -0700
                Re: Sugestions for runtime polymorphism Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-21 06:01 -0700
                Re: Sugestions for runtime polymorphism Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-22 01:44 -0700
                Re: Sugestions for runtime polymorphism BartC <bc@freeuk.com> - 2016-09-22 13:16 +0100
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-22 08:02 -0700
                Re: Sugestions for runtime polymorphism Keith Thompson <kst-u@mib.org> - 2016-09-22 11:44 -0700
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-22 09:52 -0700
                Re: Sugestions for runtime polymorphism David Brown <david.brown@hesbynett.no> - 2016-09-23 09:49 +0200
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-23 07:55 -0700
                Re: Sugestions for runtime polymorphism David Brown <david.brown@hesbynett.no> - 2016-09-24 16:29 +0200
                Re: Sugestions for runtime polymorphism Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-24 15:56 +0100
                Re: Sugestions for runtime polymorphism David Brown <david.brown@hesbynett.no> - 2016-09-24 17:50 +0200
                Re: Sugestions for runtime polymorphism "James R. Kuyper" <jameskuyper@verizon.net> - 2016-09-24 13:45 -0400
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-24 11:26 -0700
                Re: Sugestions for runtime polymorphism Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-28 10:38 -0700
                Re: Sugestions for runtime polymorphism Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-24 21:03 +0100
                Re: Sugestions for runtime polymorphism David Brown <david.brown@hesbynett.no> - 2016-09-25 12:43 +0200
                Re: Sugestions for runtime polymorphism "James R. Kuyper" <jameskuyper@verizon.net> - 2016-09-25 11:48 -0400
                Re: Sugestions for runtime polymorphism David Brown <david.brown@hesbynett.no> - 2016-09-25 18:39 +0200
                Re: Sugestions for runtime polymorphism "James R. Kuyper" <jameskuyper@verizon.net> - 2016-09-25 13:14 -0400
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-25 13:47 -0700
                Re: Sugestions for runtime polymorphism Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-28 10:39 -0700
                Re: Sugestions for runtime polymorphism David Brown <david.brown@hesbynett.no> - 2016-09-25 23:25 +0200
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-25 13:10 -0700
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-25 12:55 -0700
                Re: Sugestions for runtime polymorphism Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-25 20:38 +0100
                Re: Sugestions for runtime polymorphism David Brown <david.brown@hesbynett.no> - 2016-09-25 23:20 +0200
                Re: Sugestions for runtime polymorphism Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-28 07:15 -0700
                Re: Sugestions for runtime polymorphism David Brown <david.brown@hesbynett.no> - 2016-09-28 21:29 +0200
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-24 10:52 -0700
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-24 10:33 -0700
                Re: Sugestions for runtime polymorphism David Brown <david.brown@hesbynett.no> - 2016-09-25 12:46 +0200
                Re: Sugestions for runtime polymorphism Keith Thompson <kst-u@mib.org> - 2016-09-24 13:58 -0700
                Re: Sugestions for runtime polymorphism Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-28 04:46 -0700
                Re: Sugestions for runtime polymorphism Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-24 00:07 -0700
                Re: Sugestions for runtime polymorphism Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-23 08:52 -0700
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-23 09:56 -0700
                Re: Sugestions for runtime polymorphism Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-23 12:00 -0700
                Re: Sugestions for runtime polymorphism Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-22 08:45 -0700
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-22 09:36 -0700
                Re: Sugestions for runtime polymorphism Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-23 12:06 -0700
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-23 15:29 -0700
                Re: Sugestions for runtime polymorphism Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-29 07:56 -0700
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-30 10:54 -0700
                Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-30 11:18 -0700
                Re: Sugestions for runtime polymorphism BartC <bc@freeuk.com> - 2016-09-30 19:26 +0100
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-30 12:41 -0700
                Re: Sugestions for runtime polymorphism Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-30 21:07 +0100
                Re: Sugestions for runtime polymorphism Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-30 23:30 -0700
                Re: Sugestions for runtime polymorphism Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-10-01 11:35 +0100
                Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-10-01 14:44 -0700
        Re: Sugestions for runtime polymorphism Richard Heathfield <rjh@cpax.org.uk> - 2016-09-14 22:56 +0100
          Re: Sugestions for runtime polymorphism David Brown <david.brown@hesbynett.no> - 2016-09-15 13:19 +0200
            Re: Sugestions for runtime polymorphism James Kuyper <jameskuyper@verizon.net> - 2016-09-15 08:07 -0400
              Re: Sugestions for runtime polymorphism David Brown <david.brown@hesbynett.no> - 2016-09-15 14:24 +0200
                Re: Sugestions for runtime polymorphism Richard Heathfield <rjh@cpax.org.uk> - 2016-09-15 15:34 +0100
            Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-15 05:10 -0700
          Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-15 09:12 -0700
        Re: Sugestions for runtime polymorphism BartC <bc@freeuk.com> - 2016-09-14 23:32 +0100
        Re: Sugestions for runtime polymorphism "Chris M. Thomasson" <invalid@invalid.invalid> - 2016-09-14 17:35 -0700
        Re: Sugestions for runtime polymorphism Ian Collins <ian-news@hotmail.com> - 2016-09-15 16:24 +1200
          Re: Sugestions for runtime polymorphism Keith Thompson <kst-u@mib.org> - 2016-09-15 10:31 -0700
    Re: Sugestions for runtime polymorphism BartC <bc@freeuk.com> - 2016-09-14 22:53 +0100
      Re: Sugestions for runtime polymorphism Keith Thompson <kst-u@mib.org> - 2016-09-14 16:56 -0700
        Re: Sugestions for runtime polymorphism supercat@casperkitty.com - 2016-09-14 15:58 -0700
          Re: Sugestions for runtime polymorphism Keith Thompson <kst-u@mib.org> - 2016-09-14 18:49 -0700
  Re: Sugestions for runtime polymorphism luser droog <luser.droog@gmail.com> - 2016-09-14 14:17 -0700
    Re: Sugestions for runtime polymorphism Thiago Adams <thiago.adams@gmail.com> - 2016-09-14 14:25 -0700
      Re: Sugestions for runtime polymorphism luser droog <luser.droog@gmail.com> - 2016-09-14 14:40 -0700
      Re: Sugestions for runtime polymorphism luser droog <luser.droog@gmail.com> - 2016-09-14 14:57 -0700
      Re: Sugestions for runtime polymorphism BartC <bc@freeuk.com> - 2016-09-14 23:10 +0100
  Re: Sugestions for runtime polymorphism Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-15 11:23 -0700

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