Serious __fpclassify bug

[J. Johnston]

Good catch Joe.  Patch checked in, thanks.

-- Jeff J.

Joseph E. Vornehm, Jr. wrote:
> There is an apparent typo with serious consequences in 
> newlib/libm/common/s_fpclassify.c.  I've attached a patch for newlib 
> 1.11.0.  (cvsweb seems to indicate there haven't been any changes to 
> that file recently.)
> 
> I first noticed the problem when fmax(-12.0, 0.0) returned -12.0.  I 
> looked through the code, and since the values in question in 
> __fpclassify{f,d} are unsigned ints, some of the comparisons are always 
> false (e.g., (w >= a && w <= b) where a > b).  As a result, negative 
> numbers were being classified as FP_NAN and thence being returned 
> without comparison by fmax().  I tried the patched version, and now 
> fmax(-12.0, 0.0) returns 0.0 like it should.
> 
> I was only concerned about fmax() and fmin(); I'm not sure what else is 
> affected by this, though I would guess it's a fair bit.
> 
> Joe Vornehm
> The MITRE Corporation
> 
> 
> 
> ------------------------------------------------------------------------
> 
> --- newlib/libm/common/s_fpclassify.c.orig	2002-06-07 17:59:56.000000000 -0400
> +++ newlib/libm/common/s_fpclassify.c	2003-06-27 14:30:23.000000000 -0400
> @@ -16,10 +16,10 @@
>    if (w == 0x00000000 || w == 0x80000000)
>      return FP_ZERO;
>    else if ((w >= 0x00800000 && w <= 0x7f7fffff) ||
> -           (w >= 0xff7fffff && w <= 0x80800000))
> +           (w >= 0x80800000 && w <= 0xff7fffff))
>      return FP_NORMAL;
>    else if ((w >= 0x00000001 && w <= 0x007fffff) ||
> -           (w >= 0x807fffff && w <= 0x80000001))
> +           (w >= 0x80000001 && w <= 0x807fffff))
>      return FP_SUBNORMAL;
>    else if (w == 0x7f800000 || w == 0xff800000)
>      return FP_INFINITE;
> @@ -38,10 +38,10 @@
>        (msw == 0x80000000 && lsw == 0x00000000))
>      return FP_ZERO;
>    else if ((msw >= 0x00100000 && msw <= 0x7fefffff) ||
> -           (msw >= 0xffefffff && msw <= 0x80100000))
> +           (msw >= 0x80100000 && msw <= 0xffefffff))
>      return FP_NORMAL;
>    else if ((msw >= 0x00000000 && msw <= 0x000fffff) ||
> -           (msw >= 0x800fffff && msw <= 0x80000000))
> +           (msw >= 0x80000000 && msw <= 0x800fffff))
>      /* zero is already handled above */
>      return FP_SUBNORMAL;
>    else if ((msw == 0x7ff00000 && lsw == 0x00000000) ||