Re: [PATCH][4.15] gnttab: work around "may be used uninitialized" warning

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Mar 11, 2021 at 09:09:22AM +0100, Jan Beulich wrote:
> On 10.03.2021 18:52, Julien Grall wrote:
> > On 10/03/2021 16:21, Jan Beulich wrote:
> >> On 10.03.2021 15:58, Julien Grall wrote:
> >>> On 10/03/2021 10:13, Jan Beulich wrote:
> >>>     2) A compiler will not be able to help us if we are adding code
> >>> without initialized vaddrs.
> >>>
> >>> It also feels wrong to me to try to write Xen in a way that will make a
> >>> 10 years compiler happy...
> >>
> >> As said above - we've worked around limitations quite a few times
> >> in the past. This is just one more instance.
> > 
> > I find amusing you wrote that when you complained multiple time when 
> > someone was re-using existing bad pattern. :)
> 
> Well, thing is - I don't view this as a bad pattern. The only question
> really is whether NULL is a good initializer here. As per above a non-
> canonical pointer may be better, but then we have quite a few places
> elsewhere to fix.

Sorry for jumping in the middle but I think that would be a very
dangerous move for Xen to do. We have been using implicit conversions
of pointers to booleans all over the place, assuming that NULL ==
false, hence NULL no longer mapping to false would break a lot of our
code.  ie:

if ( foo )
        free(foo);

Would no longer work as expected.

Thanks, Roger.