Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #78193

Re: Objective C

Path csiph.com!news.swapon.de!eternal-september.org!feeder.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail
From Keith Thompson <kst-u@mib.org>
Newsgroups comp.lang.c
Subject Re: Objective C
Date Tue, 08 Dec 2015 10:40:01 -0800
Organization None to speak of
Lines 46
Message-ID <lna8pkokce.fsf@kst-u.example.com> (permalink)
References <e5eccc3a-f834-45ad-9839-9e02a6d39a93@googlegroups.com> <n2b23d$2n1$1@dont-email.me> <d692da84-f162-4273-9cbd-a9a543c35869@googlegroups.com> <n2c2ut$o6n$1@dont-email.me> <fff2ac89-757c-4d72-8307-9f48cd8327a6@googlegroups.com> <n2ero5$e51$1@dont-email.me> <1837148f-594b-4ffa-a0f3-bdce65277f5f@googlegroups.com> <n2fhmo$vpi$1@dont-email.me> <0g2o4bpcd5ofn5a1rab2vftn0sivi8ssk9@4ax.com> <kfnpoz48hpl.fsf@x-alumni2.alumni.caltech.edu> <8nj05bha7qo58upepjqipdds0fgjkl8umb@4ax.com> <m4k05bdossoe7criehdedlhgfpv1lml9rp@4ax.com> <ln7flb8u7t.fsf@kst-u.example.com> <n2qvdu$gqi$1@dont-email.me> <56510709.8000908@verizon.net> <n2rs8j$mpf$1@dont-email.me> <5651E4F7.3060208@verizon.net> <n2ttfv$6l9$1@dont-email.me> <kfn610s45z3.fsf@x-alumni2.alumni.caltech.edu> <e39b4cf1-fff2-414a-819c-0adadc58267b@googlegroups.com> <kfn4mfsyji3.fsf@x-alumni2.alumni.caltech.edu>
Mime-Version 1.0
Content-Type text/plain; charset=us-ascii
Injection-Info mx02.eternal-september.org; posting-host="945944de09706c9b4e29b53c9d2efdc2"; logging-data="5846"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+67WBFDUBF5Ls8IJwQ+rE3"
User-Agent Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux)
Cancel-Lock sha1:EXQI2A1cpr/UPvKGxrjSjpIXEKs= sha1:Q+TAvDiMCbIRpvMwghLr/8Ptk48=
Xref csiph.com comp.lang.c:78193

Show key headers only | View raw

Tim Rentsch <txr@alumni.caltech.edu> writes:
> supercat@casperkitty.com writes:
>> On Monday, November 23, 2015 at 6:05:39 PM UTC-6, Tim Rentsch wrote:
>>> Fourth:  As regards the statement in J.2, it is IMO misleading,
>>> or at the very least an oversimplification.  Despite that, I
>>> wouldn't suggest you write a defect report (and see below for why
>>> not).
>>
>> There exist implementations where an uninitialized automatic
>> variable may behave in a fashion inconsistent with its type even
>> when that type would otherwise have no trap representations.
>> [...]
>
> If there are such implementations then they are not conforming.
> There really isn't much else to say about them.

How so?

N1570 6.3.2.1p2:

    Except when it is the operand of [...], an lvalue that does
    not have array type is converted to the value stored in the
    designated object (and is no longer an lvalue); this is called
    *lvalue conversion*.  [...]  If the lvalue designates an object
    of automatic storage duration that could have been declared with
    the register storage class (never had its address taken), and
    that object is uninitialized (not declared with an initializer
    and no assignment to it has been performed prior to use),
    the behavior is undefined.

So this:

    #include <stdio.h>
    int main(void) {
        unsigned char c;
        printf("%u\n", (unsigned)c);
    }

has undefined behavior, even though unsigned char has no trap
representations.

-- 
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"

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Objective C Alla _ <modelling.data@gmail.com> - 2015-11-10 09:10 -0800
  Re: Objective C "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-11-10 09:16 -0800
  Re: Objective C Richard Heathfield <rjh@cpax.org.uk> - 2015-11-10 17:17 +0000
  Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-10 09:32 -0800
    Re: Objective C Mark Storkamp <mstorkamp@yahoo.com> - 2015-11-10 11:38 -0600
  Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-10 12:36 -0500
    Re: Objective C Alla _ <modelling.data@gmail.com> - 2015-11-10 11:15 -0800
      Re: Objective C Richard Heathfield <rjh@cpax.org.uk> - 2015-11-10 21:51 +0000
        Re: Objective C Alla _ <modelling.data@gmail.com> - 2015-11-10 23:13 -0800
      Re: Objective C supercat@casperkitty.com - 2015-11-13 16:01 -0800
        Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-14 01:07 +0000
          Re: Objective C supercat@casperkitty.com - 2015-11-14 06:26 -0800
            Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-14 22:22 +0000
              Re: Objective C supercat@casperkitty.com - 2015-11-14 15:46 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-15 01:47 +0000
                Re: Objective C BartC <bc@freeuk.com> - 2015-11-15 10:43 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-15 13:19 -0800
            Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-14 15:43 -0800
            Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-15 23:50 +0100
              Re: Objective C gazelle@shell.xmission.com (Kenny McCormack) - 2015-11-16 00:05 +0000
              Re: Objective C supercat@casperkitty.com - 2015-11-15 19:10 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-16 09:11 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-16 11:57 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-16 20:38 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-16 13:20 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-16 22:28 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-16 15:33 -0800
                Re: Objective C supercat@casperkitty.com - 2015-11-16 15:56 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-17 01:43 +0000
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-17 01:21 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-16 18:11 -0800
                Re: Objective C supercat@casperkitty.com - 2015-11-16 20:12 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-19 00:59 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-18 22:46 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-19 14:25 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-19 07:58 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-19 22:13 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-19 15:29 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-27 08:44 -0800
                Re: Objective C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-17 01:26 +0000
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-16 21:48 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-16 20:27 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-17 13:58 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-17 12:28 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-18 13:00 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-18 12:31 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-18 16:43 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-18 15:57 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-19 19:09 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-19 19:05 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-20 15:00 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-20 15:30 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-22 17:11 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-22 15:53 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-23 13:51 -0600
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-11-24 12:00 +0000
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-17 10:26 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-17 06:20 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-17 16:41 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-17 12:08 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-17 16:27 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-17 14:55 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-18 13:59 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-18 13:06 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-24 14:24 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-24 15:11 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-26 17:02 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-27 07:26 -0800
                Re: Objective C supercat@casperkitty.com - 2015-11-18 21:56 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-22 02:17 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-22 07:16 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-26 17:11 -0600
                Re: Objective C Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-11-22 19:09 +0000
                Re: Objective C Robert Wessel <robertwessel2@yahoo.com> - 2015-11-17 23:28 -0600
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-18 15:33 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-18 23:06 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-19 09:12 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-19 09:25 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-19 21:06 +0100
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-20 13:49 -0800
                Re: Objective C Robert Wessel <robertwessel2@yahoo.com> - 2015-11-21 05:01 -0600
                Re: Objective C Robert Wessel <robertwessel2@yahoo.com> - 2015-11-21 05:09 -0600
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-21 03:31 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-21 17:43 -0600
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-21 16:00 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-22 01:12 -0600
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-11-27 16:42 +0000
                Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-27 12:38 -0500
                Re: Objective C supercat@casperkitty.com - 2015-11-27 11:09 -0800
                Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-21 19:06 -0500
                Re: Objective C supercat@casperkitty.com - 2015-11-21 17:00 -0800
                Re: Objective C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-22 14:44 +0000
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-22 01:55 -0600
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-22 00:03 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-22 10:18 +0000
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-23 03:21 -0800
                Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-22 10:53 -0500
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-22 20:28 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-22 18:52 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-23 11:58 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-23 15:24 -0800
                Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-23 09:46 -0500
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-23 08:13 -0800
                Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-23 12:04 -0500
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-23 11:52 -0600
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-23 16:05 -0800
                Re: Objective C supercat@casperkitty.com - 2015-11-24 09:09 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-12-08 08:48 -0800
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-12-08 10:40 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-12-09 12:34 -0800
                Re: Objective C supercat@casperkitty.com - 2015-12-08 10:50 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-12-09 12:42 -0800
                Re: Objective C supercat@casperkitty.com - 2015-12-09 13:38 -0800
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-12-10 19:54 +0000
                Re: Objective C David Thompson <dave.thompson2@verizon.net> - 2015-12-06 08:02 -0500
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-22 14:36 -0800
                Re: Objective C Robert Wessel <robertwessel2@yahoo.com> - 2015-11-23 00:41 -0600
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-23 07:39 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-22 14:23 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-17 10:24 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-18 15:40 +0100
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-20 16:02 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-21 15:53 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-21 08:58 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-22 22:14 +0100
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-23 03:39 -0800
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-11-23 13:24 +0000
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-26 09:39 -0800
                Re: Objective C Robert Wessel <robertwessel2@yahoo.com> - 2015-11-26 13:16 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-26 12:25 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-27 14:34 -0800
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-26 12:39 -0800
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-11-27 16:43 +0000
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-27 09:29 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-27 14:18 -0800
                Re: Objective C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-23 22:35 +0000
                Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-23 17:40 -0500
                Re: Objective C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-24 05:35 +0000
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-25 12:15 -0800
                Re: Objective C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-25 22:49 +0000
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-11-27 16:44 +0000
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-27 14:03 -0800
                Re: Objective C Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-11-29 09:29 +0000
                Re: Objective C Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-11-22 19:01 +0000
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-23 07:31 -0800
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-23 07:43 -0800
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-23 08:17 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-23 17:34 +0100
                Re: Objective C Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-11-23 22:02 +0000
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-24 10:12 +0100
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-27 08:39 -0800
          Re: Objective C Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-11-14 18:24 +0000
        Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-14 12:23 -0800
          Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-14 12:36 -0800
            Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-14 13:13 -0800
              Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-14 14:04 -0800
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-14 14:15 -0800
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-14 14:29 -0800
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-14 15:39 -0800
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-14 16:37 -0800
                Re: Objective C Ian Collins <ian-news@hotmail.com> - 2015-11-15 13:46 +1300
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-15 02:06 +0000
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-15 03:25 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-15 12:56 +0000
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-15 07:53 -0600
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-15 07:19 -0600
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-15 13:29 +0000
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-15 10:56 -0800
                Re: Objective C supercat@casperkitty.com - 2015-11-15 14:35 -0800
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-15 16:52 -0800
                Re: Objective C supercat@casperkitty.com - 2015-11-15 19:49 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-16 11:02 +0000
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-16 10:36 -0800
                Re: Objective C David Thompson <dave.thompson2@verizon.net> - 2015-12-06 08:03 -0500
                Re: Objective C Melzzzzz <mel@zzzzz.com> - 2015-11-16 02:01 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-15 19:34 -0800
                Re: Objective C Chad <cdalten@gmail.com> - 2015-11-15 19:54 -0800
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-11-17 22:36 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-17 15:27 -0800
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-17 21:15 -0800
          Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-14 22:08 +0000
      Re: Objective C fir <profesor.fir@gmail.com> - 2015-11-27 14:36 -0800
  Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-10 19:03 +0100
    Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-10 10:50 -0800

csiph-web