Re: Prevent compiler warning on block.c

[Thomas Huth <thuth@redhat.com>]

On 05/05/2021 10.05, Vladimir Sementsov-Ogievskiy wrote:
> 05.05.2021 10:59, Miroslav Rezanina wrote:
>> Commit 3108a15cf (block: introduce bdrv_drop_filter()) introduced 
>> uninitialized
>> variable to_cow_parent in bdrv_replace_node_common function that is used 
>> only when
>> detach_subchain is true. It is used in two places. First if block properly 
>> initialize
>> the variable and second block use it.
>>
>> However, compiler treats this two blocks as two independent cases so it 
>> thinks first
>> block can fail test and second one pass (although both use same 
>> condition). This cause
>> warning that variable can be uninitialized in second block.
>>
>> To prevent this warning, initialize the variable with NULL.
>>
>> Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
>> ---
>> diff --git a/block.c b/block.c
>> index 874c22c43e..3ca27bd2d9 100644
>> --- a/block.c
>> +++ b/block.c
>> @@ -4851,7 +4851,7 @@ static int bdrv_replace_node_common(BlockDriverState 
>> *from,
>>       Transaction *tran = tran_new();
>>       g_autoptr(GHashTable) found = NULL;
>>       g_autoptr(GSList) refresh_list = NULL;
>> -    BlockDriverState *to_cow_parent;
>> +    BlockDriverState *to_cow_parent = NULL;
>>       int ret;
>>
>>       if (detach_subchain) {
>>
> 
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

This just popped up again here:

  https://lists.gnu.org/archive/html/qemu-devel/2021-06/msg02067.html

Kevin, Max, could you please pick it up to get this problem fixed?

  Thomas