[Cfp-interest 2141] Re: (SC22WG14.18377) Comments on N2561 (TS 18661-3 as Annex update)

[Jim Thomas]

Joseph,

Thank you for catching this.

Not removing the promotions in N2601 was an oversight. CFP will submit a paper requesting a correction, effectively the removal of X.6 #3 from N2601.

- Jim

> On Sep 17, 2021, at 7:08 AM, Joseph Myers <joseph at codesourcery.com> wrote:
> 
> On Sat, 26 Sep 2020, Jim Thomas wrote:
> 
>> Here is a link to an N2561 update which is awaiting an N-number. Changes 
>> are in response to Joseph Myers’s comments below. The link is into the 
>> CFP wiki. Contact me if you need login information.
> 
>>>> On Sep 10, 2020, at 4:30 PM, Joseph Myers <joseph at codesourcery.com> wrote:
>>>> 
>>>> Some comments on N2561 (TS 18661-3 as Annex update - note that 
>>>> http://www.open-std.org/jtc1/sc22/wg14/www/wg14_document_log.htm has the 
>>>> descriptions for N2558 and N2561 swapped), where it deviates from the 
>>>> original TS and subsequent CR resolutions:
>>>> 
>>>> * This version introduces changes to default argument promotions for 
>>>> _Float16, _Float32 and _Float64.  This is a bad idea.  To quote again the 
>>>> response to DR#206: "real float promotion to double is in Standard C 
>>>> purely for compatibility with K&R. Since complex is new, that 
>>>> compatibility is not an issue, and having it behave like real float would 
>>>> introduce undesired overhead".  Exactly the same reasoning as for _Complex 
>>>> float applies for these new types: they didn't exist in K&R C, so there is 
>>>> no need for promotion when passed in variable arguments, and it's more 
>>>> efficient not to promote them (as well as allowing for the possibility of 
>>>> a signaling NaN being passed as-is by a copy operation, which cannot 
>>>> happen when promoted).
> 
> I'd like to check on the status of the fix for this.  A discussion on the 
> liaison list drew my attention to the fact that N2601, the most recent 
> version of TS 18661-3 as Annex, still included those promotions, and I'm 
> not aware of any subsequent paper removing them from the Annex.
> 
> The September 2020 CFP minutes 
> http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2584.pdf and the October 
> 2020 CFP minutes http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2615.pdf 
> included an action item to remove those promotions.  As far as I can see, 
> while the slide deck 
> http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2578.pdf has those 
> promotions struck out on the last slide, the actual proposed Annex text 
> http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2579.pdf and the 
> subsequent version 
> http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2601.pdf don't reflect 
> that.  Did CFP change their mind (I don't see anything relevant in 
> subsequent minutes), or should this be handled through a subsequent paper?
> 
> -- 
> Joseph S. Myers
> joseph at codesourcery.com