Re: [PATCH 2/6] loader/i386/bsd: Initialize ptr variable in grub_bsd_add_meta()

[Glenn Washburn]

On Fri, 18 Mar 2022 08:57:27 +0100
Paul Menzel <pmenzel@molgen.mpg.de> wrote:

> Dear Daniel,
> 
> 
> Am 11.03.22 um 00:35 schrieb Daniel Kiper:
> > Latest GCC may complain in that way:
> 
> Just for the record, what is the latest GCC for you? 12?

I reported this issue on Debian 11 GCC version 10.2.1[1].

> 
> >    In file included from ../include/grub/disk.h:31,
> >                     from ../include/grub/file.h:26,
> >                     from ../include/grub/loader.h:23,
> >                     from loader/i386/bsd.c:19:
> >    loader/i386/bsd.c: In function ‘grub_cmd_openbsd’:
> >    ../include/grub/misc.h:71:10: error: ‘ptr’ may be used uninitialized in 
> > this function [-Werror=maybe-uninitialized]
> >       71 |   return grub_memmove (dest, src, n);
> >          |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> >    loader/i386/bsd.c:266:9: note: ‘ptr’ was declared here
> >      266 |   void *ptr;
> >          |         ^~~
> > 
> > So, let's fix it by assigning NULL to ptr in grub_bsd_add_meta().
> > 
> > Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
> > ---
> >   grub-core/loader/i386/bsd.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/grub-core/loader/i386/bsd.c b/grub-core/loader/i386/bsd.c
> > index 5f3290ce1..346c4f14a 100644
> > --- a/grub-core/loader/i386/bsd.c
> > +++ b/grub-core/loader/i386/bsd.c
> > @@ -263,7 +263,7 @@ grub_err_t
> >   grub_bsd_add_meta (grub_uint32_t type, const void *data, grub_uint32_t 
> > len)
> >   {
> >     grub_err_t err;
> > -  void *ptr;
> > +  void *ptr = NULL;
> >   
> >     err = grub_bsd_add_meta_ptr (type, &ptr, len);
> >     if (err)
> 
> It’s a bogus warning though, as `grub_bsd_add_meta_ptr()` return an 
> error when ptr wasn’t initialized yet, right?

Yes, as far as I can tell this is bogus and noted that this seems to be
a GCC issue[1]. I was only able to trigger this when using -O2, which
seems odd to me.

Glenn

[1] https://lists.gnu.org/archive/html/grub-devel/2022-03/msg00073.html

> 
> 
> Kind regards,
> 
> Paul