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Groups > comp.lang.c++ > #44726
| From | David Brown <david.brown@hesbynett.no> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Re: This will work or not? |
| Date | 2016-09-02 09:35 +0200 |
| Organization | A noiseless patient Spider |
| Message-ID | <nqba4f$cp8$1@dont-email.me> (permalink) |
| References | (5 earlier) <nq86jq$676$1@jstuckle.eternal-september.org> <nq8lod$9l9$1@dont-email.me> <nq9vrk$qrv$1@jstuckle.eternal-september.org> <nqa5n8$g2f$1@dont-email.me> <nqaj3f$mv2$2@jstuckle.eternal-september.org> |
On 02/09/16 03:02, Jerry Stuckle wrote: > On 9/1/2016 5:14 PM, David Brown wrote: >> On 01/09/16 21:34, Jerry Stuckle wrote: >>> On 9/1/2016 3:35 AM, David Brown wrote: >>>> On 01/09/16 05:17, Jerry Stuckle wrote: >> >>>>> >>>>> Incorrect. Order of data members in the struct must be as they are >>>>> declared in the struct. There may be padding between the members, but >>>>> the order cannot change. >>>>> >>>>> Compilers cannot "generate anything they want as long as the runs as >>>>> if". They are bound by other rules. >>>> >>>> No, to a very large extent they /can/ generate anything they want - as >>>> long as the code runs "as if" it followed the rules strictly. This is >>>> one of the key points for an optimising compiler. >>>> >>> >>> They can "to a very large extent". But this does NOT include reordering >>> members of a struct. The most they can do is add padding between >>> members. That is not reordering. >>> >> >> Read up a bit about the "as if" rule. >> >> You might also want to look up the "-fipa-struct-reorg" flag to gcc, >> which existed between versions 4.4 and 4.8. >> >> Here's a link so that you don't have to google: >> >> <http://stackoverflow.com/questions/14671253/is-there-a-gcc-keyword-to-allow-structure-reordering> >> >> >> And here's a paper discussing it on the Pathscale compiler: >> >> <http://www.capsl.udel.edu/conferences/open64/2008/Papers/111.pdf> >> >> Of course, it is conceivable that /you/ understand C and C++ far better >> than the people writing these compilers - but I think it is unlikely. >> >> > > And it is conceivable the quote I got from the standard shows how wrong > you are. But you never read that quote, did you? > Yes, I read the quotation. And note here that I referenced compiler writers opinions on applying the as-if rule to struct layout - not just my own. Are you telling me that you know better than they do? And I see from your other posts that you believe "the as-if rule applies to execution, not memory layout". If that belief were true, then you would be correct that struct layout is exempt from as-if optimisation. However, it is /not/ true. There are two reasons for me saying this. First, there is nowhere in the standards (C standards at least - I haven't read as much of the C++ standards) that makes this distinction. Secondly, as long as we are talking about memory that can only be seen from within the program (while following the rules of C), memory layout is nothing more than an effect of execution. The way a struct is laid out is not observable behaviour in itself, and thus the compiler is free to change it. It is /not/ free to change struct layout when that data is passed to external functions, written to files, or has volatile behaviour - those are observable effects. But if the data stays within the program as known to the compiler, the compiler is free to do as it wants.
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This will work or not? Melzzzzz <mel@zzzzz.com> - 2016-08-31 14:59 +0200
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-08-31 15:20 +0200
Re: This will work or not? mark <mark@invalid.invalid> - 2016-08-31 16:05 +0200
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-08-31 16:19 +0200
Re: This will work or not? scott@slp53.sl.home (Scott Lurndal) - 2016-08-31 14:20 +0000
Re: This will work or not? Bo Persson <bop@gmb.dk> - 2016-08-31 18:53 +0200
Re: This will work or not? Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-01 09:03 -0700
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-01 22:45 +0200
Re: This will work or not? Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-01 18:08 -0700
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-02 09:24 +0200
Re: This will work or not? Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-04 06:31 -0700
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-04 20:19 +0200
Re: This will work or not? Manfred <noname@invalid.add> - 2016-08-31 15:45 +0200
Re: This will work or not? Melzzzzz <mel@zzzzz.com> - 2016-08-31 15:59 +0200
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-08-31 16:22 +0200
Re: This will work or not? Manfred <noname@invalid.add> - 2016-08-31 17:06 +0200
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-08-31 19:29 +0200
Re: This will work or not? Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2016-08-31 21:52 +0100
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-01 09:07 +0200
Re: This will work or not? Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2016-09-01 12:30 +0100
Re: This will work or not? Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-01 09:01 -0700
Re: This will work or not? Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2016-09-01 18:16 +0100
Re: This will work or not? Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-01 18:37 -0700
Re: This will work or not? Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2016-09-02 10:42 +0100
Re: This will work or not? Tim Rentsch <txr@alumni.caltech.edu> - 2016-09-04 06:59 -0700
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-31 23:17 -0400
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-01 09:35 +0200
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-01 15:34 -0400
Re: This will work or not? me <crisdunbar@gmail.com> - 2016-09-01 13:50 -0700
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-01 21:01 -0400
Re: This will work or not? me <crisdunbar@gmail.com> - 2016-09-01 19:02 -0700
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-01 22:17 -0400
Re: This will work or not? me <crisdunbar@gmail.com> - 2016-09-02 08:19 -0700
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-02 12:39 -0400
Re: This will work or not? me <crisdunbar@gmail.com> - 2016-09-02 12:26 -0700
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-02 16:38 -0400
Re: This will work or not? me <crisdunbar@gmail.com> - 2016-09-02 13:51 -0700
Re: This will work or not? me <crisdunbar@gmail.com> - 2016-09-02 14:16 -0700
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-02 19:58 -0400
Re: This will work or not? Paavo Helde <myfirstname@osa.pri.ee> - 2016-09-02 23:56 +0300
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-03 17:58 +0200
Re: This will work or not? Manfred <noname@invalid.add> - 2016-09-02 11:41 +0200
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-02 12:27 +0200
Re: This will work or not? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-02 12:37 +0100
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-02 17:39 +0200
Re: This will work or not? Melzzzzz <mel@zzzzz.com> - 2016-09-02 17:40 +0200
Re: This will work or not? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-02 16:54 +0100
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-02 20:22 +0200
Re: This will work or not? Richard Damon <Richard@Damon-Family.org> - 2016-09-02 08:04 -0400
Re: This will work or not? BartC <bc@freeuk.com> - 2016-09-02 13:51 +0100
Re: This will work or not? Richard Damon <Richard@Damon-Family.org> - 2016-09-02 21:48 -0400
Re: This will work or not? Manfred <noname@invalid.add> - 2016-09-02 15:17 +0200
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-02 17:46 +0200
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-01 23:14 +0200
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-01 21:02 -0400
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-02 09:35 +0200
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-02 08:50 -0400
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-02 17:59 +0200
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-02 12:49 -0400
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-02 20:36 +0200
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-02 16:32 -0400
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-03 18:08 +0200
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-03 18:25 -0400
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-03 23:51 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-03 21:48 -0400
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-04 03:48 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-03 23:05 -0400
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-04 05:02 +0100
Re: This will work or not? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-04 10:57 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 09:40 -0400
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-04 16:39 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 12:46 -0400
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-04 17:51 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 13:07 -0400
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-04 18:37 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 17:16 -0400
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-04 22:23 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 18:54 -0400
Re: This will work or not? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-09-04 09:58 -0700
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 13:08 -0400
Re: This will work or not? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-09-04 10:21 -0700
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 17:18 -0400
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-04 22:24 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 18:56 -0400
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-05 00:27 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 22:53 -0400
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-05 18:18 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-05 15:27 -0400
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-05 20:32 +0100
Re: This will work or not? woodbrian77@gmail.com - 2016-09-05 14:07 -0700
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-05 18:15 -0400
Re: This will work or not? Ike Naar <ike@iceland.freeshell.org> - 2016-09-05 20:12 +0000
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-05 22:05 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-05 18:16 -0400
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-06 08:47 +0200
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-06 09:12 -0400
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-06 16:31 +0200
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-06 11:20 -0400
Re: This will work or not? bighe.trole@gmail.com - 2016-09-04 18:55 -0700
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 22:55 -0400
Re: This will work or not? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-09-04 17:17 -0700
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 22:57 -0400
Re: This will work or not? "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-09-05 11:20 -0700
Re: This will work or not? Luuk <luuk@invalid.lan> - 2016-09-04 18:54 +0200
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-04 17:59 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 13:08 -0400
Re: This will work or not? David Brown <david.brown@hesbynett.no> - 2016-09-04 20:25 +0200
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 17:20 -0400
Re: This will work or not? Öö Tiib <ootiib@hot.ee> - 2016-09-04 02:36 -0700
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-04 09:41 -0400
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-03 21:49 -0400
Re: This will work or not? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2016-09-04 03:49 +0100
Re: This will work or not? Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-03 23:06 -0400
Re: This will work or not? woodbrian77@gmail.com - 2016-09-03 21:16 -0700
Re: This will work or not? Vir Campestris <vir.campestris@invalid.invalid> - 2016-08-31 21:08 +0100
Re: This will work or not? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2016-09-01 02:28 +0200
Re: This will work or not? Öö Tiib <ootiib@hot.ee> - 2016-09-01 01:28 -0700
Re: This will work or not? "Chris M. Thomasson" <invalid@invalid.invalid> - 2016-09-02 12:06 -0700
Re: This will work or not? Öö Tiib <ootiib@hot.ee> - 2016-09-05 02:21 -0700
Re: This will work or not? Melzzzzz <mel@zzzzz.com> - 2016-09-05 13:38 +0200
Re: This will work or not? Juha Nieminen <nospam@thanks.invalid> - 2016-09-05 11:34 +0000
Re: This will work or not? Melzzzzz <mel@zzzzz.com> - 2016-09-05 13:36 +0200
Re: This will work or not? Vir Campestris <vir.campestris@invalid.invalid> - 2016-09-05 21:25 +0100
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