Re: Sequencing guarantees for macro versions of standard functions

Path	csiph.com!eternal-september.org!reader02.eternal-september.org!.POSTED!not-for-mail
From	Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups	comp.lang.c
Subject	Re: Sequencing guarantees for macro versions of standard functions
Date	Sun, 23 Jan 2022 23:50:33 -0800
Organization	None to speak of
Lines	34
Message-ID	<87mtjlo9me.fsf@nosuchdomain.example.com> (permalink)
References	<ssct1k$651$1@dont-email.me> <86k0euq62t.fsf@linuxsc.com> <87lez6xeld.fsf@nosuchdomain.example.com> <868rv5oldy.fsf@linuxsc.com> <ssl80r$h8r$1@dont-email.me> <ssl84t$h8r$2@dont-email.me>
Mime-Version	1.0
Content-Type	text/plain; charset=utf-8
Content-Transfer-Encoding	8bit
Injection-Info	reader02.eternal-september.org; posting-host="94b3a3008f708f7b40cdf3a125e51cf3"; logging-data="11858"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX186kmzQFum/mYRFtxRIdGU3"
User-Agent	Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux)
Cancel-Lock	sha1:I2WAIBsmeBEtR8fchKi3nK99ky8= sha1:OqLrbskuvYCLcxiYRlbX1azCwLI=
Xref	csiph.com comp.lang.c:164571

Show key headers only | View raw

Andrey Tarasevich <andreytarasevich@hotmail.com> writes:
> On 1/23/2022 7:56 PM, Andrey Tarasevich wrote:
>> On 1/23/2022 7:36 PM, Tim Rentsch wrote:
>>>
>>> However, the suggested rewrite has different semantics than the
>>> previous single assignment with function call.  If we want to
>>> keep the same semantics but still be able to use the macro
>>> form (but without any sequencing issues), a different writing
>>> is needed, as for example
>>>
>>>      x = modf( x, (double[]){ 0 } );
>>>
>>> Writing the call this way should make it obvious that the value
>>> stored in/through the second argument is ignored and discarded.
>> That would be
>>        x = modf( x, &(double[]){ 0 } );
>> 
>
> Opps, my sitake. Sorry, I missed the `[]` part.
>
> Of course, your original variant is correct. Although I don't see the
> point of bringing arrays into the picture. One can just do
>
>   x = modf( x, &(double){ 0 } );

My preference would be:

    double ignored;
    x = modf(x, &ignored);

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Philips
void Void(void) { Void(); } /* The recursive call of the void */

Thread

Sequencing guarantees for macro versions of standard functions Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-20 15:59 -0800
  Re: Sequencing guarantees for macro versions of standard functions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-20 16:35 -0800
    Re: Sequencing guarantees for macro versions of standard functions Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-23 14:38 -0800
      Re: Sequencing guarantees for macro versions of standard functions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-23 19:36 -0800
        Re: Sequencing guarantees for macro versions of standard functions Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-23 19:56 -0800
          Re: Sequencing guarantees for macro versions of standard functions Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-23 19:58 -0800
            Re: Sequencing guarantees for macro versions of standard functions Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-23 23:50 -0800
            Re: Sequencing guarantees for macro versions of standard functions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-24 07:27 -0800
        Re: Sequencing guarantees for macro versions of standard functions Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-23 23:49 -0800
          Re: Sequencing guarantees for macro versions of standard functions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-24 07:31 -0800
            Re: Sequencing guarantees for macro versions of standard functions Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-24 13:18 -0800
              Re: Sequencing guarantees for macro versions of standard functions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-29 03:36 -0800

csiph-web