Re: [PATCH 2/4] nbd: silence maybe-uninitialized warnings

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 30.09.20 19:19, Eric Blake wrote:
> On 9/30/20 10:58 AM, Christian Borntraeger wrote:
>> gcc 10 from Fedora 32 gives me:
>>
>> Compiling C object libblock.fa.p/nbd_server.c.o
>> ../nbd/server.c: In function ‘nbd_co_client_start’:
>> ../nbd/server.c:625:14: error: ‘namelen’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>>   625 |         rc = nbd_negotiate_send_info(client, NBD_INFO_NAME, namelen, name,
>>       |              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>   626 |                                      errp);
>>       |                                      ~~~~~
>> ../nbd/server.c:564:14: note: ‘namelen’ was declared here
>>   564 |     uint32_t namelen;
>>       |              ^~~~~~~
>> cc1: all warnings being treated as errors
>>
>> As I cannot see how this can happen, let uns silence the warning.
> 
> gcc is smart enough to see that nbd_opt_read_name(... &namelen), which
> is the only use of namelen between declaration and use, does not always
> initialize namelen; but fails to see we also exit this function early in
> the same conditions when nbd_opt_read_name left namelen uninit.  The
> workaround is fine.
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>
> 
> I'm happy for this to go in through the trivial tree, but I'll also
> queue it on my NBD tree if that is ready first.

Just in case cc qemu-trival.