Re: [Xen-devel] [RFC PATCH 0/4] Add missing default labels to switch statements

[Julien Grall <julien.grall@xxxxxxx>]

On 22/02/2019 11:30, Julien Grall wrote:
> On 22/02/2019 11:21, Andrii Anisov wrote:
> > On 22.02.19 12:27, Andrew Cooper wrote:
> > > On 22/02/2019 09:57, Oleksandr Andrushchenko wrote:
> > > > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> > > >
> > > > Hello, everybody!
> > > >
> > > > We at EPAM Systems would like to present first series of patches targeting Xen
> > > > on ARM Functional Safety certification (ISO61508 based): implementation of
> > > > MISRA [1] C:2012 Rule 16.4 which requires that every switch statement has a
> > > > default label as a measure of defensive programming technique.
> > > Hang on - what?
> > >
> > > Can someone attempt to justify why actively breaking -Wswitch is going
> > > to result in safer/better code?
> > I would express my vision of that MISRA rule requirement:
> > It requires handling (in any meaning) all possible incoming values explicitly.
> > Switching through enum still could be guarded by BUG/ASSERT_UNREACHABLE under 
> > default label. Though at runtime, not compilation time.
> While review tend to be very thorough, it is sometimes hard to spot when we miss 
> a case. This is where -Wswitch comes into place to spot missing how.
s/how/case/

> How the BUG/ASSERT_UNREACHABLE solution is going to help us here?
>
> Cheers,
--
Julien Grall

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