Re: [Xen-devel] [PATCH] xen/arm: fix build after 2e35cdf

[Julien Grall <julien.grall@xxxxxxx>]

On 6/19/19 10:47 PM, Stefano Stabellini wrote:
> On Wed, 19 Jun 2019, Julien Grall wrote:
> > Hi Stefano,
> >
> > Title: You should at least mention this is for op-tee.
> >
> > Also, mostly likely the sha1 is too small and likely to match multiple commit
> > in the future. So you want to specify the title of the commit.
> >
> > On 6/19/19 10:24 PM, Stefano Stabellini wrote:
> > > Optee breaks the build with:
> > >
> > > optee.c: In function ‘translate_noncontig.isra.4’:
> > > optee.c:743:38: error: ‘xen_data’ may be used uninitialized in this function
> > > [-Werror=maybe-uninitialized]
> > >                xen_data->next_page_data = page_to_maddr(xen_pgs + 1);
> > >                                         ^
> > > optee.c:732:71: error: ‘guest_data’ may be used uninitialized in this
> > > function [-Werror=maybe-uninitialized]
> > >            page =
> > > get_domain_ram_page(gaddr_to_gfn(guest_data->pages_list[idx]));
> > >                                                                          ^
> > > optee.c:750:21: error: ‘guest_pg’ may be used uninitialized in this function
> > > [-Werror=maybe-uninitialized]
> > >                put_page(guest_pg);
> > >                        ^
> > > cc1: all warnings being treated as errors
> > >
> > > Fix it by initializing xen_data, guest_data, guest_pg to NULL. Also set
> > > xen_pgs to NULL for consistency.
> > Without more explanation I think this is an unwise choice. If GCC thinks it is
> > going to be used unitialized, then mostly likely you silent an error that
> > could end up to dereference NULL.
> >
> > Also, setting xen_pgs for consistency will only defeat the compiler. Leading
> > to dereferencing NULL and crash Xen...
> >
> > For xen_pgs, this should definitely not be NULL. For the two others, you need
> > to explain why this is fine (if this is just because the compiler can't find
> > the reason, then you should add a comment in the code to explain it).
> I was only trying to unblock the build. 
So? We don't silence a compiler warning just for unblocking the build 
without any proper investigation. Didn't you do that before adding the NULL?
Cheers,

--
Julien Grall

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