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Re: Why does this work on Xcode ???

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On 8/23/19 1:22 AM, Alf P. Steinbach wrote:
> On 23.08.2019 00:45, Ben Bacarisse wrote:
>> "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> writes:
>> <cut>
>>> And I don't think you think you're smarter than everybody else in this
>>> group just for holding an opinion on UB that nobody else here shares.
>>
>> Why do you think no one else shares Tim's opinion?
> 
> Because he's been arguing his view for a very long time and nobody's 
> supported him.

I normally try (and often fail) to avoid paying attention to his posts,
because I've found discussions with him to be unproductive - when I
discuss my disagreements with him, we usually both end up wasting a lot
of time failing to convince each other. He's a lot like you in that regard.

He has a strong tendency to elevate what he believes to be the
committee's intent to play a larger role in the interpretation of the
standard than I think appropriate. This can be particularly annoying if
I disagree with him about what that intent was.
If the standard's wording is in conflict with (or even simply fails to
clearly express) the committee's intent, then that wording should be
corrected to clearly express that intent - but that discrepancy doesn't
change the meaning of the words that they actually wrote.

However, he is very knowledgeable about the standard, and he is correct
about the pre-eminence of a program's observable behavior. The
standard's definition of "observable behavior" is not "behavior which
can be observed" - it's far more specific than that:

"The least requirements on a conforming implementation are:
— Accesses through volatile glvalues are evaluated strictly according to
the rules of the abstract machine.
— At program termination, all data written into files shall be identical
to one of the possible results that
execution of the program according to the abstract semantics would have
produced.
— The input and output dynamics of interactive devices shall take place
in such a fashion that prompting
output is actually delivered before a program waits for input. What
constitutes an interactive device is
implementation-defined.
These collectively are referred to as the observable behavior of the
program. ..." (4.6p7).

The term "observable behavior" is in italics, an ISO convention
indicating that this sentence is the official definition of that term.
In the context of the C++ standard, that definition overrides any
alternative interpretation that might otherwise seem appropriate.

Note that the amount of stack space taken up by a program does not
qualify as "observable behavior".

The standard very explicitly says "The semantic descriptions in this
International Standard define a parameterized nondeterministic abstract
machine. This International Standard places no requirement on the
structure of conforming implementations. In particular, they need not
copy or emulate the structure of the abstract machine. Rather,
conforming implementations are required to emulate (only) the observable
behavior of the abstract machine as explained below." (4.6p1).

So if the same observable behavior can be achieved by using either an
iterative or a recursive algorithm, an implementation is free to use
either of those algorithms to achieve it, regardless of which algorithm
you actually expressed in your code. The fact that one algorithm runs a
higher risk of running out of stack space than the other imposes no
requirement on the implementation to avoid that risk (or to embrace it,
for that matter).

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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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