Re: New features added into C23 standard

From	Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups	comp.lang.c
Subject	Re: New features added into C23 standard
Date	2022-08-23 13:40 -0700
Organization	A noiseless patient Spider
Message-ID	<864jy2u20e.fsf@linuxsc.com> (permalink)
References	(7 earlier) <GStFK.601320$J0r9.21383@fx11.iad> <86y1vou2yp.fsf@linuxsc.com> <IsfLK.155213$El2.102395@fx45.iad> <86czcqud05.fsf@linuxsc.com> <871qt6zvm2.fsf@nosuchdomain.example.com>

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Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>
>> Richard Damon <Richard@Damon-Family.org> writes:
>
> [...]
>
>>> The implementation can define ANYTHING it wants (as an extension), as
>>> long as it doesn't violate a requirement of the Standard, and the
>>> Standard explicitly provides no requirement on things it declares to
>>> be Undefined Behavior, so an Implementation is free to define that
>>> behavior as anything.
>>
>> Any construct that an implementation compiles, it defines.  The behavior
>> can be defined explicitly by documenting an extension, or it can be
>> defined implicitly by what the generated code actually does.  Either
>> way, the implementation defines the behavior, but the point you are
>> trying to make is not that.
>
> You can put it that way if you like, but the standard uses the
> term "implementation-defined" specifically to refer to things that must
> be documented, and "unspecified" to refer to things that may or may not
> have to be documented.

Yes, the C standard uses the terms "implementation-defined behavior"
and "unspecified behavior" with very specific meanings, along with
the corresponding shortenings "implementation-defined" and
"unspecified".  My point is to distinguish the usage of words
"define" and "document" as they occur in ordinary English, and also
to avoid using phrases that might be confused with how similar
phrases are used in the C standard.

> For unspecified and not implementation-defined behavior, the
> choice of actual behavior might not even be deliberate.

Sure.  What behavior results might be an accidental, unconscious,
unaware, unknowing, or even unexpected and unintended consequence of
how the compiler is written.  It is still the case that the compiler
implicitly defines the behavior, by virtue of what choices are made
to produce the compiled code.

>>> [from a later posting]
>>> Yes, unfortunately, the language of the Standard doesn't give a good
>>> term for things the Implementation chooses to define but wasn't
>>> required to define.
>>
>> Yes, it does.  An implementation can document an extension that
>> specifies the behavior of the construct in question.
>
> An implementation might, for example, document the order of evaluation
> of the operands to "+".  I don't think that would be considered an
> extension (though the standard doesn't define the term "extension"
> precisely).

To my way of thinking any specification of behavior that goes beyond
what the C standard mandates counts as an extension (provided of
course it is documented), regardless of whether the additional
semantics falls into the realm of unspecified behavior, undefined
behavior, or even contradicts what the C standard says (assuming of
course the change has no effect on any strictly conforming program).
If the implementation wants to say that some additional semantic
rules are in effect then that needs to be documented somewhere, and
the only kinds of such documentation mentioned in the C standard are
for implementation-defined behavior, and for extensions.

Thread

New features added into C23 standard Thiago Adams <thiago.adams@gmail.com> - 2022-07-22 12:32 -0700
  Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-22 23:15 +0100
  Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-23 01:31 -0700
    Re: New features added into C23 standard gazelle@shell.xmission.com (Kenny McCormack) - 2022-07-23 10:10 +0000
  Re: New features added into C23 standard Thiago Adams <thiago.adams@gmail.com> - 2022-07-25 13:49 -0700
    Re: New features added into C23 standard Thiago Adams <thiago.adams@gmail.com> - 2022-07-25 13:57 -0700
      Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-25 14:50 -0700
        Re: New features added into C23 standard Thiago Adams <thiago.adams@gmail.com> - 2022-07-25 15:51 -0700
          Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-25 18:04 -0700
            Re: New features added into C23 standard Thiago Adams <thiago.adams@gmail.com> - 2022-07-25 19:23 -0700
              Re: New features added into C23 standard Opus <ifonly@youknew.org> - 2022-07-26 05:13 +0200
                Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-25 23:36 -0400
                Re: New features added into C23 standard Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-07-25 21:52 -0700
                Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-26 11:44 -0700
              Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-26 11:39 -0700
          Re: New features added into C23 standard David Brown <david.brown@hesbynett.no> - 2022-07-30 14:42 +0200
            Re: New features added into C23 standard scott@slp53.sl.home (Scott Lurndal) - 2022-07-30 15:18 +0000
              Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-30 09:13 -0700
            Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-30 17:31 +0100
              Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-30 16:46 -0700
            Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-30 14:36 -0700
              Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-30 18:15 -0400
                Re: New features added into C23 standard Kaz Kylheku <480-992-1380@kylheku.com> - 2022-07-30 23:28 +0000
                Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-31 16:48 -0700
                Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-31 22:42 -0700
                Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-31 23:25 -0700
                Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-08-01 00:10 -0700
                Re: New features added into C23 standard David Brown <david.brown@hesbynett.no> - 2022-08-01 09:55 +0200
                Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-08-01 20:17 +0100
              Re: New features added into C23 standard Kaz Kylheku <480-992-1380@kylheku.com> - 2022-07-30 23:21 +0000
        Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-25 22:59 -0700
          Re: New features added into C23 standard Öö Tiib <ootiib@hot.ee> - 2022-07-26 00:48 -0700
            Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-26 02:08 -0700
              Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-26 06:59 -0400
              Re: New features added into C23 standard Öö Tiib <ootiib@hot.ee> - 2022-07-26 04:02 -0700
                Re: New features added into C23 standard Vir Campestris <vir.campestris@invalid.invalid> - 2022-07-29 21:18 +0100
                Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-29 16:55 -0700
              Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-26 11:51 -0700
            Re: New features added into C23 standard David Brown <david.brown@hesbynett.no> - 2022-07-31 11:12 +0200
              Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-31 07:40 -0400
                Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-31 17:40 +0100
                Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-31 12:56 -0400
                Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-31 19:28 +0100
                Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-31 14:52 -0400
                Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-31 21:35 +0100
                Re: New features added into C23 standard Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-15 23:24 -0700
                Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-31 16:57 -0700
                Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-31 16:55 -0700
                Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-31 20:09 -0400
                Re: New features added into C23 standard Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-15 22:52 -0700
                Re: New features added into C23 standard David Brown <david.brown@hesbynett.no> - 2022-08-16 09:21 +0200
                Re: New features added into C23 standard Philipp Klaus Krause <pkk@spth.de> - 2022-08-16 09:32 +0200
                Re: New features added into C23 standard David Brown <david.brown@hesbynett.no> - 2022-08-16 11:06 +0200
                Re: New features added into C23 standard Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-15 23:17 -0700
                Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-08-17 20:11 -0400
                Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-08-17 20:08 -0700
                Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-08-17 23:19 -0400
                Re: New features added into C23 standard Kaz Kylheku <480-992-1380@kylheku.com> - 2022-08-18 07:03 +0000
                Re: New features added into C23 standard Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-23 09:43 -0700
                Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-08-23 11:02 -0700
                Re: New features added into C23 standard Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-23 13:40 -0700
          Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-26 07:04 -0400
            Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-26 05:24 -0700
              Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-26 22:30 -0400
                Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-29 00:02 +0100
                Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-28 21:20 -0400
                Re: New features added into C23 standard William Ahern <william@25thandClement.com> - 2022-07-28 19:36 -0700
                Re: New features added into C23 standard scott@slp53.sl.home (Scott Lurndal) - 2022-07-29 16:39 +0000
                Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-29 18:55 -0400
                Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-29 15:17 +0100
          Re: New features added into C23 standard scott@slp53.sl.home (Scott Lurndal) - 2022-07-26 13:27 +0000
          Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-26 11:47 -0700
            Re: New features added into C23 standard Kaz Kylheku <480-992-1380@kylheku.com> - 2022-07-26 20:27 +0000
              Re: New features added into C23 standard Philipp Klaus Krause <pkk@spth.de> - 2022-08-16 08:42 +0200
  Re: New features added into C23 standard Bonita Montero <Bonita.Montero@gmail.com> - 2022-07-26 05:37 +0200
    Re: New features added into C23 standard Lynn McGuire <lynnmcguire5@gmail.com> - 2022-07-28 16:47 -0500
      Re: New features added into C23 standard Bonita Montero <Bonita.Montero@gmail.com> - 2022-07-29 07:14 +0200
        Re: New features added into C23 standard Vir Campestris <vir.campestris@invalid.invalid> - 2022-07-29 21:21 +0100
  Re: New features added into C23 standard Grant Mulholland <grantlmul@gmail.com> - 2022-08-13 22:21 -0700
    Re: New features added into C23 standard Lynn McGuire <lynnmcguire5@gmail.com> - 2022-08-15 21:21 -0500
      Re: New features added into C23 standard Bonita Montero <Bonita.Montero@gmail.com> - 2022-08-16 08:39 +0200
    Re: New features added into C23 standard Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-15 22:54 -0700
    Re: New features added into C23 standard Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-08-18 12:03 -0700
      Re: New features added into C23 standard "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-08-18 12:56 -0700
      Re: New features added into C23 standard William Ahern <william@25thandClement.com> - 2022-08-18 16:07 -0700
        Re: New features added into C23 standard Thiago Adams <thiago.adams@gmail.com> - 2022-08-18 18:47 -0700
          Re: New features added into C23 standard Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-08-18 20:23 -0700

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