Groups > comp.lang.c++ > #119531

Re: is "x = ++f ++f" a valid statement ?

From	Richard Damon <richard@damon-family.org>
Newsgroups	comp.lang.c++
Subject	Re: is "x = ++f ++f" a valid statement ?
Date	2024-06-23 16:23 -0400
Organization	i2pn2 (i2pn.org)
Message-ID	<v5a086$smd5$5@i2pn2.org> (permalink)
References	(1 earlier) <v582jb$5hcq$1@dont-email.me> <v5914l$rmf0$4@i2pn2.org> <v59677$bko6$1@dont-email.me> <v59pb5$smd4$1@i2pn2.org> <v59sdl$fmkv$1@dont-email.me>

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On 6/23/24 3:18 PM, olcott wrote:
> On 6/23/2024 1:25 PM, Richard Damon wrote:
>> On 6/23/24 8:59 AM, olcott wrote:
>>> On 6/23/2024 6:32 AM, Richard Damon wrote:
>>>> On 6/22/24 10:51 PM, olcott wrote:
>>>>> On 5/23/2024 9:14 AM, Bonita Montero wrote:
>>>>>> Is "x *= ++f * ++f" a valid statement ?
>>>>>> Or is there implementation defined behaviour ?
>>>>>
>>>>> For that specific case the result would seem to be identical
>>>>> no matter the sequence of the incrementations for int type: f.
>>>>> I might not understand this fully.
>>>>>
>>>>
>>>> Nope, the issue is that increment isn't an atomic operation, but the 
>>>> storing of the incremented result is allowed to happen at any point 
>>>> prior to the end expression it is part of. (In older terms, the 
>>>> sequence point);
>>>>
>>>> If f was a user defined type, with a user define operator++ then 
>>>> yes, it is bracketed with sequencing and the two will not overlap, 
>>>> but not for primative types.
>>>
>>> It is not f++, it is ++f meaning the the operation must occur before
>>> the value is accessed.
>>>
>>
>> But the writing back of the result does not.
>>
>> The ++ and -- operators are NOT defined to be in any way "atomic".
> 
> In other words it is not a direct memory increment?
> 

Not required to be, since not all computers have one.

It CAN be, (and may well be on many processors) but isn't required to be.

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is "x *= ++f * ++f" a valid statement ? Bonita Montero <Bonita.Montero@gmail.com> - 2024-05-23 16:14 +0200
  Re: is "x *= ++f * ++f" a valid statement ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2024-06-18 18:53 -0700
    Re: is "x *= ++f * ++f" a valid statement ? Bonita Montero <Bonita.Montero@gmail.com> - 2024-06-19 17:40 +0200
    Re: is "x *= ++f * ++f" a valid statement ? PLO olcott <polcott333@gmail.com> - 2024-06-21 16:55 -0500
      Re: is "x *= ++f * ++f" a valid statement ? PLO Richard Damon <richard@damon-family.org> - 2024-06-21 18:10 -0400
        Re: is "x *= ++f * ++f" a valid statement ? PLO olcott <polcott333@gmail.com> - 2024-06-21 18:06 -0500
          Re: is "x *= ++f * ++f" a valid statement ? PLO Richard Damon <richard@damon-family.org> - 2024-06-21 20:14 -0400
          Re: is "x *= ++f * ++f" a valid statement ? PLO Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-21 17:35 -0700
            Re: is "x *= ++f * ++f" a valid statement ? PLO olcott <polcott333@gmail.com> - 2024-06-21 22:58 -0500
              Re: is "x *= ++f * ++f" a valid statement ? PLO Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-21 23:18 -0700
                Re: is "x *= ++f * ++f" a valid statement ? PLO olcott <polcott333@gmail.com> - 2024-06-22 07:38 -0500
                Re: is "x *= ++f * ++f" a valid statement ? PLO Richard Damon <richard@damon-family.org> - 2024-06-22 09:45 -0400
                Re: is "x *= ++f * ++f" a valid statement ? PLO olcott <polcott333@gmail.com> - 2024-06-22 09:13 -0500
                Re: is "x *= ++f * ++f" a valid statement ? PLO Richard Damon <richard@damon-family.org> - 2024-06-22 10:23 -0400
                Re: is "x *= ++f * ++f" a valid statement ? PLO Mikko <mikko.levanto@iki.fi> - 2024-06-23 11:48 +0300
                Re: is "x *= ++f * ++f" a valid statement ? PLO Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-22 17:54 -0700
          Re: is "x *= ++f * ++f" a valid statement ? PLO James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-06-21 23:42 -0400
            Re: is "x *= ++f * ++f" a valid statement ? PLO olcott <polcott333@gmail.com> - 2024-06-21 23:02 -0500
              Re: is "x *= ++f * ++f" a valid statement ? PLO David Brown <david.brown@hesbynett.no> - 2024-06-22 13:09 +0200
                Re: is "x *= ++f * ++f" a valid statement ? PLO olcott <polcott333@gmail.com> - 2024-06-22 07:40 -0500
                Re: is "x *= ++f * ++f" a valid statement ? PLO Richard Damon <richard@damon-family.org> - 2024-06-22 09:56 -0400
                Re: is "x *= ++f * ++f" a valid statement ? PLO "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2024-06-22 12:14 -0700
                Re: is "x *= ++f * ++f" a valid statement ? PLO David Brown <david.brown@hesbynett.no> - 2024-06-22 16:52 +0200
                Re: is "x *= ++f * ++f" a valid statement ? PLO olcott <polcott333@gmail.com> - 2024-06-22 11:27 -0500
                Re: is "x *= ++f * ++f" a valid statement ? PLO Richard Damon <richard@damon-family.org> - 2024-06-22 13:20 -0400
                Re: is "x *= ++f * ++f" a valid statement ? PLO Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-22 17:55 -0700
                Re: is "x *= ++f * ++f" a valid statement ? PLO David Brown <david.brown@hesbynett.no> - 2024-06-23 14:46 +0200
              Re: is "x *= ++f * ++f" a valid statement ? PLO James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-06-22 15:48 -0400
  Re: is "x *= ++f * ++f" a valid statement ? Richard Damon <richard@damon-family.org> - 2024-06-18 22:27 -0400
  Re: is "x *= ++f * ++f" a valid statement ? olcott <polcott333@gmail.com> - 2024-06-22 21:51 -0500
    Re: is "x *= ++f * ++f" a valid statement ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-06-22 21:51 -0700
    Re: is "x *= ++f * ++f" a valid statement ? Richard Damon <richard@damon-family.org> - 2024-06-23 07:32 -0400
      Re: is "x *= ++f * ++f" a valid statement ? olcott <polcott333@gmail.com> - 2024-06-23 07:59 -0500
        Re: is "x *= ++f * ++f" a valid statement ? Richard Damon <richard@damon-family.org> - 2024-06-23 14:25 -0400
          Re: is "x *= ++f * ++f" a valid statement ? olcott <polcott333@gmail.com> - 2024-06-23 14:18 -0500
            Re: is "x *= ++f * ++f" a valid statement ? Richard Damon <richard@damon-family.org> - 2024-06-23 16:23 -0400
              Re: is "x *= ++f * ++f" a valid statement ? David Brown <david.brown@hesbynett.no> - 2024-06-24 09:11 +0200
  Re: is "x *= ++f * ++f" a valid statement ? what@tf.com (testuseri2p) - 2024-07-22 17:51 +0000
    Re: is "x *= ++f * ++f" a valid statement ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-07-22 14:58 -0700
    Re: is "x *= ++f * ++f" a valid statement ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-07-22 21:57 -0400
      Re: is "x *= ++f * ++f" a valid statement ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-07-22 20:40 -0700
        Re: is "x *= ++f * ++f" a valid statement ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-07-23 10:15 -0400
        Re: is "x *= ++f * ++f" a valid statement ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-07-23 07:28 -0700
          Re: is "x *= ++f * ++f" a valid statement ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-07-23 14:42 -0700
            Re: is "x *= ++f * ++f" a valid statement ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-07-23 15:05 -0700
              Re: is "x *= ++f * ++f" a valid statement ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-11 06:22 -0700
                Re: is "x *= ++f * ++f" a valid statement ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-11 14:09 -0700
            Re: is "x *= ++f * ++f" a valid statement ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-11 06:11 -0700
              Re: is "x *= ++f * ++f" a valid statement ? Chris Ahlstrom <OFeem1987@teleworm.us> - 2024-08-11 09:25 -0400
              Re: is "x *= ++f * ++f" a valid statement ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-08-11 14:17 -0400
      Re: is "x *= ++f * ++f" a valid statement ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-07-23 07:32 -0700
    Re: is "x *= ++f * ++f" a valid statement ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2024-07-22 19:53 -0700
    Re: is "x *= ++f * ++f" a valid statement ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-07-23 10:01 -0400

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