[Cfp-interest 2661] Re: floating constants issue

[Vincent Lefevre]

On 2023-01-30 15:19:52 -0800, Jim Thomas wrote:
> 6.4.4.2 #8 says:
> 
> All floating constants of the same source form 83) shall convert to the same internal format with the same value.
> 
> With the FENV_ROUND and FENV_DEC_ROUND pragmas this is no longer true. For example, 7.6.2 #4 for FENV_ROUND says "Floating constants (6.4.4.2) of a standard floating type that occur in the scope of a constant rounding mode shall be interpreted according to that mode."
> 
> This was pointed out in a recent email which I was unable to find. Thanks to the sender.

I posted the remark about 6.4.4.2 #8 in Cfp-interest 2634:
  http://mailman.oakapple.net/pipermail/cfp-interest/2023-January/002648.html

But I hadn't noticed the issue with FENV_ROUND.

> A fix would be to replace the sentence with something like:
> 
> All floating constants of the same source form shall convert to the same internal format. All floating constants of the same source form that are subject to the same translation-time rounding direction (either the default or a rounding direction set by an FENV_ROUND or FENV_DEC_ROUND pragma) shall convert to the same internal format with the same value.
> 
> or
> 
> All floating constants of the same source form shall convert to the same internal format and, provided they are subject to the same translation-time rounding direction (either the default or a rounding direction set by an FENV_ROUND or FENV_DEC_ROUND pragma), to the same value.

Both are unclear. What if it is set to FE_DYNAMIC?

BTW, is there a way to restore the static rounding mode when
outside external declarations? This would be important if one
wants to use this pragma in a header file.

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Vincent Lefèvre <vincent at vinc17.net> - Web: <https://www.vinc17.net/>
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