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Groups > comp.lang.c > #21664

Re: Q: Local variables initialization shortcut.

Message-ID <4FCA0128.435E@mindspring.com> (permalink)
Date 2012-06-02 08:03 -0400
From pete <pfiland@mindspring.com>
Organization PF
Newsgroups comp.lang.c
Subject Re: Q: Local variables initialization shortcut.
References <5835baa1-db3f-4b81-a9e9-3ea20a632ba8@w24g2000vby.googlegroups.com> <a2u8bhF5u8U1@mid.uni-berlin.de> <4f89a691-f680-4dbc-bdbc-363450ccc001@b26g2000vbt.googlegroups.com>

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Jean-Christophe wrote:
> 
> On 2 juin, 12:31, j...@toerring.de :
 
> > '&z - &a' isn't legal - you can only subtract addresses
> > of locations within a single object (e.g. an array),
> 
> I've done it many times and it always worked fine :

If you beieve that something which works once,
will always work again, 
then why ask questions 
instead of just testing your code?

> &a is the address of 'a' so it's its memory location.

The C standard characterizes that operation as being undefined.

N1570
6.5.6 Additive operators

9 When two pointers are subtracted,
  both shall point to elements of the same array object,
  or one past the last element of the array object; 
  the result is the difference of the
  subscripts of the two array elements.

-- 
pete

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Thread

Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 02:49 -0700
  Re: Q: Local variables initialization shortcut. China Blue Max <chine.bleu@yahoo.com> - 2012-06-02 03:03 -0700
    Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 03:17 -0700
  Re: Q: Local variables initialization shortcut. jacob navia <jacob@spamsink.net> - 2012-06-02 12:06 +0200
    Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 03:25 -0700
      Re: Q: Local variables initialization shortcut. James Kuyper <jameskuyper@verizon.net> - 2012-06-02 10:59 -0400
        Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 13:02 -0700
          Re: Q: Local variables initialization shortcut. Keith Thompson <kst-u@mib.org> - 2012-06-02 14:51 -0700
  Re: Q: Local variables initialization shortcut. Ian Collins <ian-news@hotmail.com> - 2012-06-02 22:10 +1200
  Re: Q: Local variables initialization shortcut. jt@toerring.de (Jens Thoms Toerring) - 2012-06-02 10:31 +0000
    Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 03:59 -0700
      Re: Q: Local variables initialization shortcut. jt@toerring.de (Jens Thoms Toerring) - 2012-06-02 11:55 +0000
        Re: Q: Local variables initialization shortcut. pete <pfiland@mindspring.com> - 2012-06-02 08:15 -0400
        Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 05:37 -0700
          Re: Q: Local variables initialization shortcut. jt@toerring.de (Jens Thoms Toerring) - 2012-06-02 13:35 +0000
            Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 06:47 -0700
              Re: Q: Local variables initialization shortcut. "BartC" <bc@freeuk.com> - 2012-06-02 15:08 +0100
                Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 07:37 -0700
                Re: Q: Local variables initialization shortcut. "BartC" <bc@freeuk.com> - 2012-06-02 16:17 +0100
                Re: Q: Local variables initialization shortcut. "BartC" <bc@freeuk.com> - 2012-06-02 19:02 +0100
              Re: Q: Local variables initialization shortcut. jt@toerring.de (Jens Thoms Toerring) - 2012-06-02 17:39 +0000
                Re: Q: Local variables initialization shortcut. Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-06-02 15:27 -0400
                Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 12:58 -0700
                Re: Q: Local variables initialization shortcut. Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-06-02 16:15 -0400
                Re: Q: Local variables initialization shortcut. David Brown <david.brown@hesbynett.no> - 2012-06-03 15:27 -0500
                Re: Q: Local variables initialization shortcut. Noob <root@localhost> - 2012-06-05 09:12 +0200
                Re: Q: Local variables initialization shortcut. David Brown <david@westcontrol.removethisbit.com> - 2012-06-05 09:21 +0200
                Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 12:53 -0700
                Re: Q: Local variables initialization shortcut. "BartC" <bc@freeuk.com> - 2012-06-02 21:16 +0100
                Re: Q: Local variables initialization shortcut. jt@toerring.de (Jens Thoms Toerring) - 2012-06-02 21:18 +0000
                Re: Q: Local variables initialization shortcut. Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-06-02 17:38 -0400
                Re: Q: Local variables initialization shortcut. jt@toerring.de (Jens Thoms Toerring) - 2012-06-02 22:15 +0000
                Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-03 00:51 -0700
                Re: Q: Local variables initialization shortcut. Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-03 11:46 -0700
                Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-03 00:13 -0700
                Re: Q: Local variables initialization shortcut. Keith Thompson <kst-u@mib.org> - 2012-06-02 14:50 -0700
                Re: Q: Local variables initialization shortcut. David Brown <david.brown@hesbynett.no> - 2012-06-03 15:34 -0500
          Re: Q: Local variables initialization shortcut. David Brown <david.brown@hesbynett.no> - 2012-06-03 15:25 -0500
        Re: Q: Local variables initialization shortcut. Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-06-02 08:46 -0400
        Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 05:46 -0700
          Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 05:53 -0700
            Re: Q: Local variables initialization shortcut. Ike Naar <ike@sverige.freeshell.org> - 2012-06-02 17:08 +0000
            Re: Q: Local variables initialization shortcut. "io_x" <a@b.c.invalid> - 2012-06-03 10:33 +0200
              Re: Q: Local variables initialization shortcut. "io_x" <a@b.c.invalid> - 2012-06-03 11:32 +0200
      Re: Q: Local variables initialization shortcut. pete <pfiland@mindspring.com> - 2012-06-02 08:03 -0400
        Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 05:18 -0700
    Re: Q: Local variables initialization shortcut. "io_x" <a@b.c.invalid> - 2012-06-03 10:32 +0200
  Re: Q: Local variables initialization shortcut. "BartC" <bc@freeuk.com> - 2012-06-02 11:45 +0100
    Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 04:17 -0700
      Re: Q: Local variables initialization shortcut. "BartC" <bc@freeuk.com> - 2012-06-02 12:40 +0100
        Re: Q: Local variables initialization shortcut. "BartC" <bc@freeuk.com> - 2012-06-02 12:51 +0100
        Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 04:57 -0700
          Re: Q: Local variables initialization shortcut. "BartC" <bc@freeuk.com> - 2012-06-02 14:00 +0100
            Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 06:12 -0700
              Re: Q: Local variables initialization shortcut. Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-06-02 09:58 -0400
                Re: Q: Local variables initialization shortcut. David Brown <david.brown@hesbynett.no> - 2012-06-03 15:41 -0500
              Re: Q: Local variables initialization shortcut. Robert Wessel <robertwessel2@yahoo.com> - 2012-06-02 11:45 -0500
  Re: Q: Local variables initialization shortcut. Noob <root@localhost> - 2012-06-02 16:05 +0200
    Re: Q: Local variables initialization shortcut. Jean-Christophe <5.d@free.fr> - 2012-06-02 07:48 -0700
      Re: Q: Local variables initialization shortcut. "BartC" <bc@freeuk.com> - 2012-06-02 18:31 +0100
      Re: Q: Local variables initialization shortcut. jt@toerring.de (Jens Thoms Toerring) - 2012-06-02 17:50 +0000

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