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

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 22/02/2019 10:27, 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 was about to ask the same. There are quite a few cases where this series is 
going to make more difficult extending enum.
Furthermore, using BUG() is a pretty bad idea in switch. A guest would be able 
to crash the whole platform if there was a coding mistake. Instead we should use 
ASSERT_UNREACHABLE() and provide proper fallback whenever it is possible.
Cheers,

--
Julien Grall

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