From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
To: Alejandro Colomar <alx@kernel.org>,
Morten Welinder <mwelinder@gmail.com>
Cc: linux-man@vger.kernel.org, libc-help@sourceware.org
Subject: Re: logb() vs floor(log2())
Date: Mon, 4 Mar 2024 15:47:26 -0300 [thread overview]
Message-ID: <bddcd00f-7adf-4558-9733-6a71906b46ed@linaro.org> (raw)
In-Reply-To: <ZeYKUOKYS7G90SaV@debian>
On 04/03/24 14:52, Alejandro Colomar wrote:
> Hi Morten,
>
> On Thu, Feb 29, 2024 at 07:28:10PM -0500, Morten Welinder wrote:
>> I came across some minor issues in some math man pages.
>>
>> M.
>>
>>
>>
>> logb:
>> The formula "floor(log2(x))" should be "floor(log2(fabs(x)))". (Or
>> ...abs(...) if it's meant to be math and not C.)
>
> Confirmed. This is a bug in glibc too, BTW. That text seems to be
> copied from their manual.
>
> ISO C says this function is specified in ANSI/IEEE 854, but I don't have
> access to that document, so I'm not sure what's the specification of the
> function. I'm not sure if it should fail for negative values (like
> log2(3)) or not; although the standard mentions the behavior for
> negative infinity, so it probably is specified to work for negative
> values too.
>
> So, the behavior of the function seems to be correct, and it's just the
> manual that needs to be fixed.
>
> I've CCed glibc, in case they want to comment. But yeah, your
> suggestion seems correct.
It does seems to be an error on manual, could you send a patch to fix it?
next prev parent reply other threads:[~2024-03-04 18:47 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CANv4PNkVv_0eLgiSP3L_KfC-eZJaVLZ5AP1AGfD0GNrR5M4Hrg@mail.gmail.com>
2024-03-04 17:52 ` logb() vs floor(log2()) (was: Man page issues: logb, significand, cbrt, log2, log10, exp10) Alejandro Colomar
2024-03-04 18:47 ` Adhemerval Zanella Netto [this message]
2024-03-04 22:16 ` logb() vs floor(log2()) Alejandro Colomar
2024-03-04 23:23 ` logb() vs floor(log2()) (was: Man page issues: logb, significand, cbrt, log2, log10, exp10) Alejandro Colomar
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