[Cfp-interest 2151] Re: scheduling message

Sun Sep 26 09:57:18 PDT 2021

Aaron Ballman will be hosting the Zoom meeting for WG21 and CFP members to discuss issues with extension floating-point types. Information for joining the meeting is contained in the invitation (below) which Aaron sent to the C++ Numerics and WG14 reflectors.

-  Jim Thomas

---

Hello! I would like to invite everyone to attend an SG22-hosted
special discussion on Wed Oct 6 at 15:00 UTC
(https://www.timeanddate.com/worldclock/converter.html?iso=20211006T150000&p1=tz_pt&p2=tz_mt&p3=tz_ct&p4=tz_et&p5=1440&p6=tz_cest <https://www.timeanddate.com/worldclock/converter.html?iso=20211006T150000&p1=tz_pt&p2=tz_mt&p3=tz_ct&p4=tz_et&p5=1440&p6=tz_cest>).

P1467R4 (https://wg21.link/P1467R4 <https://wg21.link/P1467R4>) Extended floating-point types and
standard names
This will be a joint discussion with the C Floating Point Study Group.
The paper proposes allowing implementations to provide new extended
floating-point types in C++. C already allows such types through the
integration of TS18661 into C23. The authors would like to have a
discussion around the names of the types and the header where the
names are defined, and a discussion of where the behavior of these
types differ between languages, including implicit conversions and
usual arithmetic conversions. We expect to take preference polls on
naming decisions.

Topic: Joint Discussion of P1467R4
Time: Oct 6, 2021 11:00 AM Eastern Time (US and Canada)

Join from PC, Mac, Linux, iOS or Android:
https://iso.zoom.us/j/5513145100?pwd=SnhxSmJiV2tsemtxbS9HSTl0cUtLZz09 <https://iso.zoom.us/j/5513145100?pwd=SnhxSmJiV2tsemtxbS9HSTl0cUtLZz09>
   Password: please contact Aaron Ballman or Jim Thomas for the password

Or iPhone one-tap :
   US: +16027530140,,5513145100#  or +12532158782,,5513145100#
Or Telephone:
   Dial(for higher quality, dial a number based on your current location):
       US: +1 602 753 0140  or +1 253 215 8782  or +1 346 248 7799
or +1 408 638 0968  or +1 669 219 2599  or +1 669 900 6833  or +1 720
928 9299  or +1 971 247 1195  or +1 206 337 9723  or +1 213 338 8477
or +1 312 626 6799  or +1 470 250 9358  or +1 470 381 2552  or +1 646
518 9805  or +1 646 876 9923  or +1 651 372 8299  or +1 786 635 1003
or +1 267 831 0333  or +1 301 715 8592  or 877 853 5247 (Toll Free) or
888 788 0099 (Toll Free)
   Meeting ID: 551 314 5100
   Password: 89239314
   International numbers available: https://iso.zoom.us/u/aQsAgOF5z <https://iso.zoom.us/u/aQsAgOF5z>

Or Skype for Business (Lync):
   https://iso.zoom.us/skype/5513145100 <https://iso.zoom.us/skype/5513145100>

> On Sep 22, 2021, at 11:49 AM, Jim Thomas <jaswthomas at sbcglobal.net> wrote:
> 
> It looks like the best time for the meeting, for attendance from WG21 and CFP, will be Wednesday, October 6, at 8 AM PDT / 11 AM EDT  / 3 PM UTC.
> 
> - Jim Thomas
> 
>> On Sep 21, 2021, at 2:01 PM, Jim Thomas <jaswthomas at sbcglobal.net <mailto:jaswthomas at sbcglobal.net>> wrote:
>> 
>> Please also let me know if you could attend on Tuesday, October 5, same time.
>> 
>> - Jim Thomas
>> 
>>> On Sep 20, 2021, at 5:45 PM, Jim Thomas <jaswthomas at sbcglobal.net <mailto:jaswthomas at sbcglobal.net>> wrote:
>>> 
>>> The C/C++ liaison group has been discussing at some length possible conflicts (see below) with the WG21 proposal for extension floating-point types and the new C23 annex for TS-3.  Aaron Ballman, as SC22 chair, suggested a joint 1-hour meeting with CFP and interested WG21 members as a forum to deal with the concerns. After email discussion, Aaron, Rajan, and I decided to propose Wednesday, October 6, at 8 AM PDT / 11 AM EDT  / 3 PM UTC. Would you be able to attend a zoom meeting at that time? Please respond if possible by end of Tuesday, September 21.
>>> 
>>> - Jim Thomas
>>> 
>>> Aaron wrote:
>>> 
>>>> Here's the summary of topics I've pulled together from the various
>>>> reflector discussions:
>>>> 
>>>> * Currently, the new types are exclusively available in the
>>>> _Reserved_name spelling (like "_Bool" was in C99), there is no set of
>>>> "pretty" macros (like "bool" was in <stdbool.h>) -- that means that if
>>>> C++ decides to introduce new pretty names like (std::)float16_t, we
>>>> have no immediately interoperable name (like "float16_t") that would
>>>> be valid C, since there is no macro "#define float16_t _Float_16",
>>>> say.
>>>> 
>>>> * The proposed rules for C and C++ have different arithmetic conversion rules:
>>>>   float + _Float32 -> _Float32
>>>>   float + std::float32 -> float
>>>> 
>>>> * The above point is observable in that you get UB when passing a
>>>> _Float32 vs a float as a vararg parameter due to the promotion rules
>>>> (float promotes to double, _Float32 does not).
>>> 
>>>> It's possible I've missed some points (there are a few threads going
>>>> with a lot of messages on each of them), but Fred Tydeman and Joseph
>>>> Myers have both weighed in on the thread, which is helpful! ...
>> 
> 

> On Sep 22, 2021, at 11:49 AM, Jim Thomas <jaswthomas at sbcglobal.net> wrote:
> 
> It looks like the best time for the meeting, for attendance from WG21 and CFP, will be Wednesday, October 6, at 8 AM PDT / 11 AM EDT  / 3 PM UTC.
> 
> - Jim Thomas
> 
>> On Sep 21, 2021, at 2:01 PM, Jim Thomas <jaswthomas at sbcglobal.net <mailto:jaswthomas at sbcglobal.net>> wrote:
>> 
>> Please also let me know if you could attend on Tuesday, October 5, same time.
>> 
>> - Jim Thomas
>> 
>>> On Sep 20, 2021, at 5:45 PM, Jim Thomas <jaswthomas at sbcglobal.net <mailto:jaswthomas at sbcglobal.net>> wrote:
>>> 
>>> The C/C++ liaison group has been discussing at some length possible conflicts (see below) with the WG21 proposal for extension floating-point types and the new C23 annex for TS-3.  Aaron Ballman, as SC22 chair, suggested a joint 1-hour meeting with CFP and interested WG21 members as a forum to deal with the concerns. After email discussion, Aaron, Rajan, and I decided to propose Wednesday, October 6, at 8 AM PDT / 11 AM EDT  / 3 PM UTC. Would you be able to attend a zoom meeting at that time? Please respond if possible by end of Tuesday, September 21.
>>> 
>>> - Jim Thomas
>>> 
>>> Aaron wrote:
>>> 
>>>> Here's the summary of topics I've pulled together from the various
>>>> reflector discussions:
>>>> 
>>>> * Currently, the new types are exclusively available in the
>>>> _Reserved_name spelling (like "_Bool" was in C99), there is no set of
>>>> "pretty" macros (like "bool" was in <stdbool.h>) -- that means that if
>>>> C++ decides to introduce new pretty names like (std::)float16_t, we
>>>> have no immediately interoperable name (like "float16_t") that would
>>>> be valid C, since there is no macro "#define float16_t _Float_16",
>>>> say.
>>>> 
>>>> * The proposed rules for C and C++ have different arithmetic conversion rules:
>>>>   float + _Float32 -> _Float32
>>>>   float + std::float32 -> float
>>>> 
>>>> * The above point is observable in that you get UB when passing a
>>>> _Float32 vs a float as a vararg parameter due to the promotion rules
>>>> (float promotes to double, _Float32 does not).
>>> 
>>>> It's possible I've missed some points (there are a few threads going
>>>> with a lot of messages on each of them), but Fred Tydeman and Joseph
>>>> Myers have both weighed in on the thread, which is helpful! ...
>> 
> 

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