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Re: Broken isnan(3) and/or DQNAN on Tru64


From: Ludovic Courtès
Subject: Re: Broken isnan(3) and/or DQNAN on Tru64
Date: Sat, 02 May 2009 11:33:13 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.0.90 (gnu/linux)

Hi Bruno,

Bruno Haible <address@hidden> writes:

> What's the result when you compile it with cc?
>   $ cc foo.c -lm
>   $ ./a.out
>   $ echo $?

1

That's with "Compaq C V6.5-303 (dtk) on Compaq Tru64 UNIX V5.1B
(Rev. 2650)".

Should we conclude that this is a GCC bug?  I'll try with different
versions.

> What's the result for a program that uses a quiet NaN, computed
> differently?
>
>   #include <math.h>
>   double zero = 0.0;
>   int main()
>   {
>     return isnan (zero / zero);
>   };

SIGFPE with both `cc' and GCC 4.0.2.

> And finally, what's the hexdump of that DQNAN constant?
>
>   #include <math.h>
>   #include <stdio.h>
>   int main()
>   {
>     printf("%04X%04X\n", DQNAN[1], DQNAN[0]);
>     return 0;
>   }

FFF800000000

Quite different from what we have on GNU in <bits/nan.h>...

Thanks,
Ludo'.




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