2010-02-11 Craig Howland <howland@LGSInnovations.com>

        * libm/common/s_ilogb.c:  Adjust documentation to reflect new returns
        (see next items) and that ilogb() and ilogbf() are C99/POSIX.
        * libm/common/s_ilogb.c (ilogb):  Use C99/POSIX FP_ILOGB0 and
        FP_ILOGBNAN returns for 0 and NAN arguments, respectively, instead of
        the prior -INT_MAX and INT_MAX.  The FP_ILOGBx defines in math.h
        presently match the prior hard-codes, so no functional change is
        actually introduced.  (Not at this time, nor planned, but the values
        are permitted to be different, so subsequent edits of math.h could
        possibly cause a functional change.)
        * libm/common/sf_ilogb.c (ilogbf):  Ditto.

2 files changed, 27 insertions, 10 deletions

diff --git a/newlib/libm/common/s_ilogb.c b/newlib/libm/common/s_ilogb.c
index 00dfef633..67558f748 100644
--- a/newlib/libm/common/s_ilogb.c
+++ b/newlib/libm/common/s_ilogb.c
@@ -44,13 +44,24 @@ DESCRIPTION
 RETURNS
 
 <<ilogb>> and <<ilogbf>> return the power of two used to form the
-floating-point argument.  If <[val]> is <<0>>, they return <<-
-INT_MAX>> (<<INT_MAX>> is defined in limits.h).  If <[val]> is
-infinite, or NaN, they return <<INT_MAX>>.
+floating-point argument.
+If <[val]> is <<0>>, they return <<FP_ILOGB0>>.
+If <[val]> is infinite, they return <<INT_MAX>>.
+If <[val]> is NaN, they return <<FP_ILOGBNAN>>.
+(<<FP_ILOGB0>> and <<FP_ILOGBNAN>> are defined in math.h, but in turn are
+defined as INT_MIN or INT_MAX from limits.h.  The value of FP_ILOGB0 may be
+either INT_MIN or -INT_MAX.  The value of FP_ILOGBNAN may be either INT_MAX or
+INT_MIN.)
+
+@comment The bugs might not be worth noting, given the mass non-C99/POSIX
+@comment behavior of much of the Newlib math library.
+@commentBUGS
+@commentOn errors, errno is not set per C99 and POSIX requirements even if
+@comment(math_errhandling & MATH_ERRNO) is non-zero.
 
 PORTABILITY
-	Neither <<ilogb>> nor <<ilogbf>> is required by ANSI C or by
-	the System V Interface Definition (Issue 2).  */
+C99, POSIX
+*/
 
 /* ilogb(double x)
  * return the binary exponent of non-zero x
@@ -58,8 +69,8 @@ PORTABILITY
  * ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
  */
 
-#include "fdlibm.h"
 #include <limits.h>
+#include "fdlibm.h"
 
 #ifndef _DOUBLE_IS_32BITS
 
@@ -76,7 +87,7 @@ PORTABILITY
 	hx &= 0x7fffffff;
 	if(hx<0x00100000) {
 	    if((hx|lx)==0) 
-		return - INT_MAX;	/* ilogb(0) = 0x80000001 */
+		return FP_ILOGB0;	/* ilogb(0) = special case error */
 	    else			/* subnormal x */
 		if(hx==0) {
 		    for (ix = -1043; lx>0; lx<<=1) ix -=1;
@@ -86,7 +97,10 @@ PORTABILITY
 	    return ix;
 	}
 	else if (hx<0x7ff00000) return (hx>>20)-1023;
-	else return INT_MAX;
+	#if FP_ILOGBNAN != INT_MAX
+	else if (hx>0x7ff00000) return FP_ILOGBNAN;	/* NAN */
+	#endif
+	else return INT_MAX;	/* infinite (or, possibly, NAN) */
 }
 
 #endif /* _DOUBLE_IS_32BITS */
diff --git a/newlib/libm/common/sf_ilogb.c b/newlib/libm/common/sf_ilogb.c
index ec59406e1..28191c2c6 100644
--- a/newlib/libm/common/sf_ilogb.c
+++ b/newlib/libm/common/sf_ilogb.c
@@ -13,8 +13,8 @@
  * ====================================================
  */
 
-#include "fdlibm.h"
 #include <limits.h>
+#include "fdlibm.h"
 
 #ifdef __STDC__
 	int ilogbf(float x)
@@ -28,11 +28,14 @@
 	GET_FLOAT_WORD(hx,x);
 	hx &= 0x7fffffff;
 	if(FLT_UWORD_IS_ZERO(hx))
-	    return - INT_MAX;	/* ilogb(0) = 0x80000001 */
+	    return FP_ILOGB0;	/* ilogb(0) = special case error */
 	if(FLT_UWORD_IS_SUBNORMAL(hx)) {
 	    for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;
 	    return ix;
 	}
+	#if FP_ILOGBNAN != INT_MAX
+	else if (FLT_UWORD_IS_NAN(hx)) return FP_ILOGBNAN;	/* NAN */
+	#endif
 	else if (!FLT_UWORD_IS_FINITE(hx)) return INT_MAX;
 	else return (hx>>23)-127;
 }