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| From | Eric Sosman <esosman@ieee-dot-org.invalid> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Q: Local variables initialization shortcut. |
| Date | 2012-06-02 15:27 -0400 |
| Organization | A noiseless patient Spider |
| Message-ID | <jqdpf2$pn4$1@dont-email.me> (permalink) |
| References | (3 earlier) <a2uda9F4vcU1@mid.uni-berlin.de> <0ecf3c52-be95-4a37-a6f0-42469d378f1e@m3g2000vbl.googlegroups.com> <a2uj5rFvv1U1@mid.uni-berlin.de> <0e159ddf-1c62-4bc2-bb70-a8369dec0c00@a16g2000vby.googlegroups.com> <a2v1eeFru9U1@mid.uni-berlin.de> |
On 6/2/2012 1:39 PM, Jens Thoms Toerring wrote:
>[...]
> So the the order of the positions of the variables in memory
> (at least on my machine and using gcc 4.6.1) is different for
> local and global variables. While not terribly interesting it
> could serve as an example that making assumption about the
> memory layout of variables the compiler will use is at least
> tricky;-)
One implementation *alphabetized* global variables, apparently
during the link phase. I discovered this while trying to port
some code that assumed `double trouble, bubble;' would imply
`&trouble < &bubble', which turned out not to be the case ...
Specifically, the code was doing things like (paraphrased):
int checksum_start;
... data to be checksum-protected ...
int checksum_end;
for (int *p = &checksum_start; ++p < checksum_end; ) {
... accumulate checksum ...
}
When alphabetization put `checksum_end' *before* `checksum_start',
the fan was hit by the fertilizer.
--
Eric Sosman
esosman@ieee-dot-org.invalid
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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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