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

[Ian Jackson <iwj@xenproject.org>]

Jan Beulich writes ("Re: [PATCH][4.15] gnttab: work around "may be used uninitialized" warning"):
> On 12.03.2021 11:04, Ian Jackson wrote:
> > Julien Grall writes ("Re: [PATCH][4.15] gnttab: work around "may be used uninitialized" warning"):
> >> This is pretty much what we are already doing slowly by initializing 
> >> values to shut up older compilers. I agree this is more limited, but we 
> >> also waive off diagnostics from every single compiler in that code 
> >> rather than just one version.
> >>
> >> Hence why I suggested dropping -Werror for older compiler. This is not 
> >> ideal but it would give us the ability to keep support for dinausor 
> >> compiler and not hamper our ability to take advantage of newer compiler 
> >> diagnostics.
> > 
> > I agree with Julien.  I think we should avoid adding these redundant
> > initialisers for the reasons he gives.
> 
> I find this odd, not only because it is contrary to what we've done so
> far. What if more modern gcc issues a false-positive warning? If we'd
> fix it there, where would you suggest to draw the line? Imo our tree
> should build without issues on all compiler versions which we state we
> permit to be used.
> 
> Of course in the case here I could add a "default:" to the switch(),
> but this would still only work around the compiler issue. Would the
> two of you consider this any better?
> 
> Also, Ian - do you have any alternative suggestion towards making the
> build work again (in the more general case, i.e. irrespective of the
> alternative suggestion for this specific case just above)? Not using
> -Werror on old compilers (again - where would we draw the line) was
> already objected to by me.

I read your objection to not using -Werror for such old compilers but
I did not agree with it.

I am sympathetic to Julien's desire to try to limit the set of
supported compilers.

Ian.