Re: [PATCH] IB/mlx4: Avoid implicit enumerated type conversion
From: Nick Desaulniers
Date: Thu Sep 27 2018 - 18:42:39 EST
On Thu, Sep 27, 2018 at 3:33 PM Bart Van Assche <bvanassche@xxxxxxx> wrote:
> On Thu, 2018-09-27 at 16:28 -0600, Jason Gunthorpe wrote:
> > On Thu, Sep 27, 2018 at 01:34:16PM -0700, Nick Desaulniers wrote:
> > > > Neither ib_qp_create_flags nor mlx4_ib_qp_flags have negative values, is
> > > > signedness necessary?
> > >
> > > enums are by default restricted to the range of ints.
> > That's not quite right, the compiler sizes the enum to be able to fit
> > the largest value contained within, today that is int, but if we added
> > 1<<31, then it would become larger.
> Hi Jason,
> Are you perhaps confusing C and C++? For C++, an enumeration whose underlying
> type is not fixed, the underlying type is an integral type that can represent
> all the enumerator values defined in the enumeration. For C however I think
> that enumeration values are restricted to what fits in an int.
To quote the sacred texts (ANSIIISO9899-1990):
22.214.171.124 Enumeration specifiers
The expression that defines the value of an enumeration constant shall
be an integral constant
expression that has a value representable as an int.