Re: [RFC PATCH 2/4] xen/arm64: bitops: justify uninitialized variable inside a macro

[Julien Grall <julien@xxxxxxx>]

Hi,

On 16/07/2023 10:20, Luca Fancellu wrote:
> > On 14 Jul 2023, at 14:05, Julien Grall <julien@xxxxxxx> wrote:
> >
> > Hi,
> >
> > On 14/07/2023 12:49, Nicola Vetrini wrote:
> > > The macro 'testop' expands to a function that declares the local
> > > variable 'oldbit', which is written before being set, but is such a
> > > way that is not amenable to automatic checking.
> > The code is pretty straightforward. So I am not entirely sure why Eclair is not 
> > happy. Is it because the value is set by assembly code?
> Hi Julien,
>
> Yes I agree that it’s strange, do you think that that if at line 97 we 
> initialize oldbit to zero, it would solve the issue?
At the moment, I am not entirely happy to zero oldbit because we have 
other places in Xen where we need assembly instructions to read a value 
(e.g. READ_SYSREG()).
So I would first like to understand why Eclair can't cope with it.

Cheers,

--
Julien Grall