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Date: Fri, 30 Dec 2022 18:50:24 +0000
From: Joseph Myers <joseph@codesourcery.com>
To: Alejandro Colomar <alx.manpages@gmail.com>
CC: =?ISO-8859-15?Q?Cristian_Rodr=EDguez?= <crrodriguez@opensuse.org>, "G.
 Branden Robinson" <g.branden.robinson@gmail.com>, Jonny Grant <jg@jguk.org>,
	Florian Weimer <fweimer@redhat.com>, Michael Kerrisk
	<mtk.manpages@gmail.com>, linux-man <linux-man@vger.kernel.org>, GNU C
 Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH] Add example to rand.3
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On Fri, 30 Dec 2022, Alejandro Colomar via Libc-alpha wrote:

> > I expect to implement these functions in due course for glibc (not GCC,
> > since these are library functions, with the usual requirements for
> > definitions with external linkage, though most would also have inline
> > header implementations based on existing longstanding built-in functions).
> 
> Is there any builtin for stdc_bit_ceil()?  I've tried to search for it, but
> didn't find it.  I came to the conclusion that I need to write the ugly code
> around __builtin_clz().

I don't think there's such a built-in function, so yes, the inline 
function would need to use __builtin_clz.  (Even the stdc_leading_zeros 
inline functions will need to do more than just call __builtin_clz - they 
need to check for zero, since the standard functions have a defined result 
for a zero argument whereas __builtin_clz doesn't.)

-- 
Joseph S. Myers
joseph@codesourcery.com