Re: [Qemu-devel] [PATCH 23/25] fdc: Move floppy geometry guessing back from block.c

[Eric Blake]

On 07/09/2012 10:07 AM, Markus Armbruster wrote:

>>> This is an unconditional use of fd_type[0].  If floppy == NULL, this is 
>>> dereferencing an uninitialized value.
>>>
>>> I'm not sure why the explicit initialization was removed...
> 
> Brain fart on my part, sorry.  The old loop assigns only if the drive
> exists.  The new loop assigns unconditionally.  Except the whole loop is
> still conditional.
> 
> Testing can't flag this, because floppy is never null.
> 
>> Looks broken indeed. I just wonder why my gcc (or the buildbots) didn't
>> complain.
> 
> Me too.  Looks like I should upgrade to a more recent gcc.

It's probably not the version of the gcc you used, but whether or not
your CFLAGS include -O2.  Gcc has the (IMO very annoying) limitation
that uninitialized-use analysis can only be performed if you are also
doing optimization.  You have to use a tool like clang or Coverity if
you want more reliable uninitialized-use analysis even while building
-O0 debug images.

-- 
Eric Blake   address@hidden    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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