linux-kernel - Re: [PATCH] IB/mlx4: Avoid implicit enumerated type conversion

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Message-ID: <CAKwvOdnvXDtBAw_6_MSOEst3DBjbr8w6Pv6b4i=pC50s=gcq3Q@mail.gmail.com>
Date:   Wed, 3 Oct 2018 15:53:58 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     jgg@...pe.ca
Cc:     Nathan Chancellor <natechancellor@...il.com>, dledford@...hat.com,
        linux-rdma@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] IB/mlx4: Avoid implicit enumerated type conversion

On Wed, Oct 3, 2018 at 3:35 PM Jason Gunthorpe <jgg@...pe.ca> wrote:
>
> On Mon, Sep 24, 2018 at 12:57:16PM -0700, Nathan Chancellor wrote:
> > Clang warns when one enumerated type is implicitly converted to another.
> >
> > drivers/infiniband/hw/mlx4/mad.c:1811:41: warning: implicit conversion
> > from enumeration type 'enum mlx4_ib_qp_flags' to different enumeration
> > type 'enum ib_qp_create_flags' [-Wenum-conversion]
> >                 qp_init_attr.init_attr.create_flags = MLX4_IB_SRIOV_TUNNEL_QP;
> >                                                     ~ ^~~~~~~~~~~~~~~~~~~~~~~
> >
> > drivers/infiniband/hw/mlx4/mad.c:1819:41: warning: implicit conversion
> > from enumeration type 'enum mlx4_ib_qp_flags' to different enumeration
> > type 'enum ib_qp_create_flags' [-Wenum-conversion]
> >                 qp_init_attr.init_attr.create_flags = MLX4_IB_SRIOV_SQP;
> >                                                     ~ ^~~~~~~~~~~~~~~~~
> >
> > The type mlx4_ib_qp_flags explicitly provides supplemental values to the
> > type ib_qp_create_flags. Make that clear to Clang by changing the
> > create_flags type to u32.
> >
> > Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> > ---
> >  include/rdma/ib_verbs.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
>
> Applied to for-next, thanks
>
> BTW, how are you compiling with clang?

https://github.com/ClangBuiltLinux/linux/wiki/Steps-for-compiling-the-kernel-with-Clang
try it out, let us know bugs you find here:
https://github.com/ClangBuiltLinux/linux/issues

Still looking into the case you pointed out earlier.  I suspect the
signedness of enums was undefined in c90, then defined as
implementation specific in c99 (though I'm still researching that book
report).  Thanks for your insights!

>
> Jason



-- 
Thanks,
~Nick Desaulniers