Re: GCC hasn't even gotten around to sequencing argument evaluation

From	James Kuyper <jameskuyper@alumni.caltech.edu>
Newsgroups	comp.lang.c++
Subject	Re: GCC hasn't even gotten around to sequencing argument evaluation
Date	2022-04-05 14:36 -0400
Organization	A noiseless patient Spider
Message-ID	<t2i26o$efi$3@dont-email.me> (permalink)
References	(7 earlier) <t2e9qb$q6l$1@gioia.aioe.org> <t2efo4$jqc$1@dont-email.me> <t2f03t$kt$1@gioia.aioe.org> <t2f420$q7p$1@dont-email.me> <t2hmk6$1nno$1@gioia.aioe.org>

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On 4/5/22 11:18, Muttley@dastardlyhq.com wrote:
> On Mon, 4 Apr 2022 08:49:18 -0700
> Andrey Tarasevich <andreytarasevich@hotmail.com> wrote:
>> On 4/4/2022 7:42 AM, Muttley@dastardlyhq.com wrote:
>>> On Mon, 4 Apr 2022 12:02:44 +0200
>>> David Brown <david.brown@hesbynett.no> wrote:
>>>> On 04/04/2022 10:21, Muttley@dastardlyhq.com wrote:
>>>>> Perhaps it should be defined as it looks reasonable to me. What does the
>>>>> standard say about i = (++i) + (++i) ?
>>>>>
>>>>
>>>> The same thing - undefined behaviour.  Parentheses do not affect the
>>>> order of evaluation.
>>>
>>> I don't understand why it should be undefined. It should evaluate both sides
>>> of the argument in order they're defined - and it has to be in order or
>>> precedance checks, lazy evaluation and function calls could fail - and then
>> do
>>> the addition. So if i = 1 at the start then at the end it should be 2 + 3.
>>
>> That's a lot of "should" and "has to be" with no connection to reality.
>>
>> C and C++ don't work that way. Precedence in C and C++ has no relation 
>> to order of evaluation for built-in operators.
> 
> Really? So if I write a + b * c it might evaluate a + b first? You sure 
> about that?
> 

In order to explain sequencing, it's generally best to replace more
complicated expressions into and equivalent set of smaller
expression-statements, with unnamed temporaries in the expression
replaced by named temporaries in the expression statements:

temp1 = a;	// A
temp2 = b; 	// B
temp3 = c;	// C
temp4 = temp2*temp3;	// D
temp5 = temp1 + temp4;	// E

There are two relevant clauses in the standard, both from 6.9.1p10:

"The value computations of the operands of an operator are sequenced
before the value computation of the result of the operator."

Because of that clause, statements B and C must be evaluated before
statement D, statements C and D must be evaluated before statement E.

That's what you're talking about.

"Except where noted, evaluations of operands of individual operators and
of subexpressions of individual expressions are unsequenced."

Because of that clause, there are no other constraints on the order in
which those statements are evaluated. The following are all legal orders
of evaluation:

ABCDE
ACBDE
BACDE
BCADE
CABDE
CBADE
BCDAE
CBDAE

Now, the order in which statements A, B, and C occur does not matter in
this case. However, if we replaced a, b, and c with expressions that had
side effects (such as a(), b() and c()), the order in which those side
effects happened could matter, and all of the above orders are permitted.
That's what we're talking about.

Thread

GCC hasn't even gotten around to sequencing argument evaluation yet??? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-01 20:34 -0700
  Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-04-02 10:19 +0200
    Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Bo Persson <bo@bo-persson.se> - 2022-04-02 12:19 +0200
    Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Bonita Montero <Bonita.Montero@gmail.com> - 2022-04-02 14:18 +0200
  Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Christian Gollwitzer <auriocus@gmx.de> - 2022-04-02 12:30 +0200
    Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? David Brown <david.brown@hesbynett.no> - 2022-04-02 14:12 +0200
      Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Bonita Montero <Bonita.Montero@gmail.com> - 2022-04-02 14:20 +0200
      Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-02 14:28 +0000
        Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-02 17:27 +0200
          Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-02 15:39 +0000
            Re: GCC hasn't even gotten around to sequencing argument evaluation Barry Schwarz <schwarzb@delq.com> - 2022-04-02 09:15 -0700
              Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-04 08:21 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-04 12:02 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-04 14:42 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-04 08:49 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-05 15:18 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-05 08:37 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-05 15:54 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-06 11:24 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation Juha Nieminen <nospam@thanks.invalid> - 2022-04-06 10:49 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-06 18:21 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2022-04-06 15:40 +0100
                Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-06 15:00 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2022-04-06 17:03 +0100
                Re: GCC hasn't even gotten around to sequencing argument evaluation Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2022-04-06 17:18 +0100
                Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-07 08:58 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-04-07 11:01 -0400
                Re: GCC hasn't even gotten around to sequencing argument evaluation "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-04-06 23:13 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-07 09:11 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-06 10:53 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-04-06 14:50 -0400
                Re: GCC hasn't even gotten around to sequencing argument evaluation Sams Lara <samlara622@gmail.com> - 2022-04-06 22:27 +0100
                Re: GCC hasn't even gotten around to sequencing argument evaluation Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-04-06 14:51 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation Sams Lara <samlara622@gmail.com> - 2022-04-06 22:59 +0100
                Re: GCC hasn't even gotten around to sequencing argument evaluation Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-04-06 15:54 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation Öö Tiib <ootiib@hot.ee> - 2022-04-06 15:11 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-04-09 09:38 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-04-06 23:48 -0400
                Re: GCC hasn't even gotten around to sequencing argument evaluation Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-06 18:39 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-04-06 23:49 -0400
                Re: GCC hasn't even gotten around to sequencing argument evaluation Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-04-05 08:55 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-05 10:23 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-04-05 14:36 -0400
                Re: GCC hasn't even gotten around to sequencing argument evaluation James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-04-04 12:27 -0400
                Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-05 15:21 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-05 08:41 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-05 15:50 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-05 10:19 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-04-05 14:33 -0400
                Re: GCC hasn't even gotten around to sequencing argument evaluation James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-04-05 14:28 -0400
                Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-04 18:29 +0200
            Re: GCC hasn't even gotten around to sequencing argument evaluation Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-02 11:27 -0700
              Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-04 08:23 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-04 12:15 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-04 14:43 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-04 18:34 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-05 15:23 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-05 08:38 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-05 15:49 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-04-05 11:31 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation scott@slp53.sl.home (Scott Lurndal) - 2022-04-05 22:45 +0000
            Re: GCC hasn't even gotten around to sequencing argument evaluation James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-04-02 23:34 -0400
              Re: GCC hasn't even gotten around to sequencing argument evaluation Manfred <noname@add.invalid> - 2022-04-03 17:43 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-04-03 15:40 -0400
              Re: GCC hasn't even gotten around to sequencing argument evaluation Muttley@dastardlyhq.com - 2022-04-04 08:24 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-04-04 12:01 -0400
            Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-03 13:02 +0200
              Re: GCC hasn't even gotten around to sequencing argument evaluation Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-04-03 04:46 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation Öö Tiib <ootiib@hot.ee> - 2022-04-03 07:02 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-04-03 11:30 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-03 21:20 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-04-03 12:49 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation Paavo Helde <eesnimi@osa.pri.ee> - 2022-04-04 00:40 +0300
                Re: GCC hasn't even gotten around to sequencing argument evaluation Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-04-03 15:40 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-04 09:13 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-04 09:02 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-04-04 02:07 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-04 13:28 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-04-04 06:01 -0700
                Re: GCC hasn't even gotten around to sequencing argument evaluation David Brown <david.brown@hesbynett.no> - 2022-04-04 19:11 +0200
                Re: GCC hasn't even gotten around to sequencing argument evaluation scott@slp53.sl.home (Scott Lurndal) - 2022-04-04 17:59 +0000
                Re: GCC hasn't even gotten around to sequencing argument evaluation Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-04-05 06:55 -0700
              Re: GCC hasn't even gotten around to sequencing argument evaluation Manfred <noname@add.invalid> - 2022-04-03 18:39 +0200
        Re: GCC hasn't even gotten around to sequencing argument evaluation Paavo Helde <eesnimi@osa.pri.ee> - 2022-04-03 09:09 +0300
      Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Manfred <noname@add.invalid> - 2022-04-02 19:53 +0200
        Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? David Brown <david.brown@hesbynett.no> - 2022-04-03 13:45 +0200
          Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Manfred <noname@add.invalid> - 2022-04-03 17:27 +0200
      Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-04-02 21:17 +0100
        Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Manfred <noname@invalid.add> - 2022-04-02 23:04 +0200
          Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-04-03 00:22 +0100
        Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-02 17:33 -0700
          Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-04-03 14:23 +0100
          Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-04-06 08:31 -0700
            Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-06 11:05 -0700
              Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-04-25 03:32 -0700
    Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-02 11:18 -0700
  Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? David Brown <david.brown@hesbynett.no> - 2022-04-02 13:11 +0200
  Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Manu Raju <MR@invalid.invalid> - 2022-04-02 18:26 +0100
  Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Manu Raju <MR@invalid.invalid> - 2022-04-02 21:46 +0100
    Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-02 17:35 -0700
  Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Language Lawyer <language.lawyer@gmail.com> - 2022-04-04 02:28 -0700
    Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-04 05:52 -0700
      Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Language Lawyer <language.lawyer@gmail.com> - 2022-06-21 03:36 -0700
  Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Juha Nieminen <nospam@thanks.invalid> - 2022-04-04 10:48 +0000
    Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-04 05:49 -0700
      Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Juha Nieminen <nospam@thanks.invalid> - 2022-04-05 06:34 +0000
        Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-04-05 10:20 +0100
        Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-05 07:51 -0700
          Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Manfred <noname@add.invalid> - 2022-04-05 17:53 +0200
  Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Christian Hanné <the.hanne@gmail.com> - 2022-04-10 06:06 +0200
    Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-09 21:20 -0700
    Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2022-04-09 21:39 -0700
      Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-04-09 22:34 -0700
        Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Christian Hanné <the.hanne@gmail.com> - 2022-04-10 09:19 +0200
          Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? David Brown <david.brown@hesbynett.no> - 2022-04-10 12:21 +0200
            Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Christian Hanné <the.hanne@gmail.com> - 2022-04-10 12:47 +0200
          Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2022-04-11 12:18 -0700
            Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-04-11 12:33 -0700
      Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Christian Hanné <the.hanne@gmail.com> - 2022-04-10 09:20 +0200
        Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2022-04-11 12:32 -0700
          Re: GCC hasn't even gotten around to sequencing argument evaluation yet??? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-04-11 15:11 -0700

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