linux-kernel - Re: [PATCH] Avoid that check_shl_overflow() triggers a compiler warning when building with W=1

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Date:   Fri, 8 Mar 2019 07:01:10 +0000
From:   Leon Romanovsky <leonro@...lanox.com>
To:     Bart Van Assche <bvanassche@....org>
CC:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Kees Cook <keescook@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
Subject: Re: [PATCH] Avoid that check_shl_overflow() triggers a compiler
 warning when building with W=1

On Thu, Mar 07, 2019 at 04:08:23PM -0800, Bart Van Assche wrote:
> On Thu, 2019-03-07 at 08:18 +0100, Rasmus Villemoes wrote:
> > On 07/03/2019 03.14, Bart Van Assche wrote:
> > > On 3/6/19 5:24 PM, Jason Gunthorpe wrote:
> > > > >
> > > > > diff --git a/include/linux/overflow.h b/include/linux/overflow.h
> > > > > index 40b48e2133cb..8afe0c0ada6f 100644
> > > > > +++ b/include/linux/overflow.h
> > > > > @@ -202,6 +202,24 @@
> > > > >     #endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */
> > > > >   +/*
> > > > > + * Evaluate a >= 0 without triggering a compiler warning if the type
> > > > > of a
> > > > > + * is an unsigned type.
> > > > > + */
> > > > > +#define is_positive(a) ({                    \
> >
> > is_non_negative, please! positive means > 0. And perhaps it's better to
> > move these utility macros closer to the top of the file, together with
> > the other type/range helpers.
>
> Hi Rasmus,
>
> Thank you for the feedback. But according to what I found online opinions
> about whether or not zero is a positive number seem to vary. From
> https://en.wikipedia.org/wiki/Sign_(mathematics):

Mathematical therm for discrete numbers greater or equal to zero is
"normal numbers".

Thanks

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