Bug#237373: libc6-dev: support for fegetprec / fesetprec to control the dynamic precision modes

[GOTO Masanori <gotom@debian.or.jp>]

At Thu, 11 Mar 2004 11:19:15 +0100,
Vincent Lefevre wrote:
> The WG14 N752 C9X revision proposal contained functions for
> controlling the dynamic precision modes:
> 
>        The fegetprec and fesetprec functions provide control of
>        dynamic precision modes.
> 
>        Each macro
> 
>            FE_FLTPREC
>            FE_DBLPREC
>            FE_LDBLPREC
> 
>        is defined if and only if the implementation supports the
>        dynamic precision by means of the functions in 7.6.z.  The
>        defined macros expand to integral constant expressions whose
>        values are distinct.
> 
> You can see http://anubis.dkuug.dk/jtc1/sc22/wg14/www/docs/n752.htm
> for more information. Unfortunately, this was dropped. But some
> vendors implement them anyway. I'd like them to be implemented in
> glibc too. If these functions and macros became a de facto standard,
> this would be very useful when one wants double-precision rounding
> on x86 processors. The problem with fpu_control.h features is that
> they are specific to glibc.

Could you provide me more information?

 - Which merit should we use them?
 - n752.htm has only above explanation.  Where can I get more info?
 - Do x86 processors have this kind of functions?
 - Why was this dropped?

Regards,
-- gotom