From: Alejandro Colomar <alx@kernel.org>
Date: Sun, 31 Mar 2024 20:38:39 +0000 (+0200)
Subject: manual: logb(x) is floor(log2(fabs(x)))
X-Git-Tag: glibc-2.40~306
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b7d15bd1f00ae3f941150c9e49e65fbc6595adda;p=thirdparty%2Fglibc.git

manual: logb(x) is floor(log2(fabs(x)))

log2(3) doesn't accept negative input, but it seems logb(3) does accept
it.

Link: <https://lore.kernel.org/linux-man/ZeYKUOKYS7G90SaV@debian/T/#u>
Reported-by: Morten Welinder <mwelinder@gmail.com>
Reviewed-by: DJ Delorie <dj@redhat.com>
Cc: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Cc: Vincent Lefevre <vincent@vinc17.net>
Cc: Paul Zimmermann <Paul.Zimmermann@inria.fr>
Cc: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
---

diff --git a/manual/math.texi b/manual/math.texi
index 2f6ee253b9..c54eaebb65 100644
--- a/manual/math.texi
+++ b/manual/math.texi
@@ -561,7 +561,7 @@ These functions return the base-2 logarithm of @var{x}.
 @safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
 These functions extract the exponent of @var{x} and return it as a
 floating-point value.  If @code{FLT_RADIX} is two, @code{logb} is equal
-to @code{floor (log2 (x))}, except it's probably faster.
+to @code{floor (log2 (fabs (x)))}, except it's probably faster.
 
 If @var{x} is de-normalized, @code{logb} returns the exponent @var{x}
 would have if it were normalized.  If @var{x} is infinity (positive or