[RFC, MIPS] Relax NaN rules

[Joseph S. Myers]

On Tue, 25 Mar 2014, Matthew Fortune wrote:

> Can you envisage any way of us raising a warning/error if INVALID 
> exceptions get enabled in this hybrid NaN world? I believe that is the 
> only major problem area with mixing NaNs. I.e. It should be possible to 
> introduce a magic symbol if LD merged opposing NaN modules and have 
> fesetexcept check for it but I can't think up a way to indicate to 
> fesetexcept if LDSO linked opposing NaN modules (I'm not sufficiently 
> experienced with dynamic linkers to know what is possible though).

fesetexcept - a new function in TS 18661-1, not implemented in glibc - has 
nothing to do with this; the issue is about exceptions from arithmetic 
rather than those from functions explicitly setting them.  And to a first 
approximation you can ignore exceptions being "enabled" (i.e. traps being 
enabled) and presume they are tested for by C99 facilities such as 
fetestexcept - which has no way to return any sort of error status.

-- 
Joseph S. Myers
joseph@codesourcery.com