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Date: Tue, 26 Oct 2021 09:45:20 +0200
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Thread-Topic: [dpdk-dev] [PATCH v2] doc: propose correction rte_{bsf,
 fls} inline functions type use
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From: =?iso-8859-1?Q?Morten_Br=F8rup?= <mb@smartsharesystems.com>
To: "Thomas Monjalon" <thomas@monjalon.net>, <stephen@networkplumber.org>,
 "Tyler Retzlaff" <roretzla@linux.microsoft.com>
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 <mdr@ashroe.eu>, <david.marchand@redhat.com>, <dmitry.kozliuk@gmail.com>,
 <bruce.richardson@intel.com>
Subject: Re: [dpdk-dev] [PATCH v2] doc: propose correction rte_{bsf,
 fls} inline functions type use
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> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Thomas Monjalon
> Sent: Monday, 25 October 2021 21.14
>=20
> 15/03/2021 20:34, Tyler Retzlaff:
> > The proposal has resulted from request to review [1] the following
> > functions where there appeared to be inconsistency in return type
> > or parameter type selections for the following inline functions.
> >
> > rte_bsf32()
> > rte_bsf32_safe()
> > rte_bsf64()
> > rte_bsf64_safe()
> > rte_fls_u32()
> > rte_fls_u64()
> > rte_log2_u32()
> > rte_log2_u64()
> >
> > [1] http://mails.dpdk.org/archives/dev/2021-March/201590.html
> >
> > Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
> > ---
> > --- a/doc/guides/rel_notes/deprecation.rst
> > +++ b/doc/guides/rel_notes/deprecation.rst
> > +* eal: Fix inline function return and parameter types for
> rte_{bsf,fls}
> > +  inline functions to be consistent.
> > +  Change ``rte_bsf32_safe`` parameter ``v`` from ``uint64_t`` to
> ``uint32_t``.
> > +  Change ``rte_bsf64`` return type to  ``uint32_t`` instead of
> ``int``.
> > +  Change ``rte_fls_u32`` return type to ``uint32_t`` instead of
> ``int``.
> > +  Change ``rte_fls_u64`` return type to ``uint32_t`` instead of
> ``int``.
>=20
> It seems we completely forgot this.
> How critical is it?

Not updating has near zero effect on bug probability: Incorrectly =
returning signed int instead of unsigned int is extremely unlikely to =
cause problems.

Updating has near zero performance improvement: The unnecessary =
expansion of a parameter value from 32 to 64 bits is cheap.

The update's only tangible benefit is API consistency. :-)

-Morten