[Cfp-interest 2145] Re: scheduling message

[Jim Thomas]

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> 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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