Re: Fw: Useless sNaNs... or useful?
> Subject: Fw: Useless sNaNs... or useful?
> To: stds-1788@xxxxxxxxxxxxxxxxx
> From: Ian McIntosh <ianm@xxxxxxxxxx>
> Date: Fri, 15 Oct 2010 14:25:31 -0400
>
>
>
> . . .
>
> One important use is to initialize all floating point variables to
> signaling NaNs. If they are inadvertently not properly initialized lat=
> er,
> you will be told if the program attempts to use them. I used to use a
> pre-754 system that had an option to initialize everything to their
> equivalent of a negative signaling NaN with the payload containing that=
>
> particular memory address and a few other bits to make it likely to fai=
> l if
> used as a pointer or subscript. That found bugs even in some carefully=
>
> written programs that "worked" on other systems (just not correctly). =
> I
> know of companies doing this themselves today. It would be a worthwhil=
> e
> feature in every system, and doesn't depend much on NaN portability. I=
> t is
> affected by the second imperfect portability - whether the payload is o=
> r is
> not preserved.
>
> . . .
>
> - Ian McIntosh IBM Canada Lab Compiler Back End Suppor=
>
I know of no companies doing this today.
Please name them.
Dan