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Groups > comp.lang.c++ > #67908
| From | "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Re: Why does this work on Xcode ??? |
| Date | 2019-08-23 16:02 +0200 |
| Organization | A noiseless patient Spider |
| Message-ID | <qjorma$d2b$1@dont-email.me> (permalink) |
| References | (8 earlier) <86v9upglek.fsf@mailhub.linuxsc.com> <qjmkm4$84q$1@dont-email.me> <87pnkwakex.fsf@bsb.me.uk> <qjnt6f$e14$1@dont-email.me> <8736hsdqsv.fsf@bsb.me.uk> |
On 23.08.2019 14:12, Ben Bacarisse wrote: > If it is so clearly settled (in > C++, I presume -- maybe C is different here), just cite the unequivocal > text that settles the matter. If anyone disagrees, cite the text > again. That's what's been done, by others and by me. And evidently that's not enough, but I've run out of ideas about what would help. Anyway, yet again, but for your convenience, first consider C++17 §1.4/2.1: [quote] If a program contains no violations of the rules in this International Standard, a conforming implementation shall, within its resource limits, accept and correctly execute that program. [/quote] There are no requirements, here or anywhere else in the standard, about what should happen or not if the program is not executable within the implementation's resource limits. There is a requirement, the quoted text, if the the execution is within the resource limits. There are no requirements otherwise. And "no requirements" is the definition of Undefined Behavior. C++17 §1.3.27 [quote] 1.3.27 [defns.undefined] undefined behavior behavior for which this International Standard imposes no requirements [/quote] One argument that has been made against this very clear and indisputable (really) wording, is that it doesn't mean that the defined term is equivalent to the stated definition, but rather that it just implies the apparent definition. Thus, in that distorted view, UB would imply no requirements, but no requirements would not necessarily imply UB. A common example of the conventional view, the equivalence of "UB" and "no requirements", is a `*p` dereferencing of a nullpointer outside of a `typeid` expression. Everybody (well, almost everybody!) agree that `*p` is Undefined Behavior because the standard imposes no requirements about it. If the one-way implication view was adopted, dereferencing that nullpointer would no longer be UB. The same goes for use of the referenced non-object, if any: in the conventional view it's UB because there are no requirements. With the one way implication view it's... what? I don't know, it just doesn't make sense to me. So, that view appears to be entirely silly, impractical, but the discussion continues, at least for me, i.e. this is my personal reason, because it's generally a good idea to flesh out what a so long standing disagreement is about. One can learn things from that. Still I'm as far as ever from understanding what it's really about. Cheers, - Alf
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Why does this work on Xcode ??? Bob Langelaan <bobl0456@gmail.com> - 2019-07-16 22:03 -0700
Re: Why does this work on Xcode ??? Paavo Helde <myfirstname@osa.pri.ee> - 2019-07-17 08:46 +0300
Re: Why does this work on Xcode ??? Öö Tiib <ootiib@hot.ee> - 2019-07-17 00:06 -0700
Re: Why does this work on Xcode ??? Öö Tiib <ootiib@hot.ee> - 2019-07-17 01:44 -0700
Re: Why does this work on Xcode ??? Juha Nieminen <nospam@thanks.invalid> - 2019-07-17 07:46 +0000
Re: Why does this work on Xcode ??? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-07-17 09:12 -0400
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-07-17 17:01 +0200
Re: Why does this work on Xcode ??? Mr Flibble <flibbleREMOVETHISBIT@i42.co.uk> - 2019-07-17 22:15 +0100
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-07-17 23:29 +0200
Re: Why does this work on Xcode ??? Christian Gollwitzer <auriocus@gmx.de> - 2019-07-19 08:27 +0200
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-07-19 09:09 +0200
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-07-19 09:24 +0200
Re: Why does this work on Xcode ??? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-08-10 11:18 -0700
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-10 21:05 +0200
Re: Why does this work on Xcode ??? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-08-22 10:28 -0700
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-22 19:50 +0200
Re: Why does this work on Xcode ??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-08-22 23:45 +0100
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-23 07:22 +0200
Re: Why does this work on Xcode ??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-08-23 13:12 +0100
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-23 16:02 +0200
Re: Why does this work on Xcode ??? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-09-18 08:50 -0700
Re: Why does this work on Xcode ??? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-23 09:28 -0400
Re: Why does this work on Xcode ??? David Brown <david.brown@hesbynett.no> - 2019-08-23 16:37 +0200
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-23 23:07 +0200
Re: Why does this work on Xcode ??? Richard Damon <Richard@Damon-Family.org> - 2019-08-23 19:10 -0400
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-24 06:49 +0200
Re: Why does this work on Xcode ??? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-23 19:49 -0400
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-24 06:45 +0200
Re: Why does this work on Xcode ??? David Brown <david.brown@hesbynett.no> - 2019-08-25 12:06 +0200
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-25 13:25 +0200
Re: Why does this work on Xcode ??? David Brown <david.brown@hesbynett.no> - 2019-08-25 15:11 +0200
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-25 17:12 +0200
Re: Why does this work on Xcode ??? David Brown <david.brown@hesbynett.no> - 2019-08-25 23:32 +0200
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-26 11:51 +0200
Re: Why does this work on Xcode ??? David Brown <david.brown@hesbynett.no> - 2019-08-26 13:26 +0200
Re: Why does this work on Xcode ??? David Brown <david.brown@hesbynett.no> - 2019-08-25 11:36 +0200
Re: Why does this work on Xcode ??? "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-25 13:27 +0200
Re: Why does this work on Xcode ??? David Brown <david.brown@hesbynett.no> - 2019-08-25 15:15 +0200
Re: Why does this work on Xcode ??? James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-26 00:43 -0400
Re: Why does this work on Xcode ??? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-08-24 04:58 -0700
Re: Why does this work on Xcode ??? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-08-26 09:53 -0700
Re: Why does this work on Xcode ??? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-08-28 18:03 -0700
Re: Why does this work on Xcode ??? Öö Tiib <ootiib@hot.ee> - 2019-07-19 00:20 -0700
Re: Why does this work on Xcode ??? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-08-09 07:41 -0700
Re: Why does this work on Xcode ??? Bonita Montero <Bonita.Montero@gmail.com> - 2019-08-24 19:49 +0200
Re: Why does this work on Xcode ??? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-07-21 11:41 +0000
Re: Why does this work on Xcode ??? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-08-10 09:29 -0700
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