Re: [PATCH] migration/qemu-file: Fix maybe uninitialized on qemu_get_buffer_in_place()

[Wainer dos Santos Moschetta <wainersm@redhat.com>]

Hi,

On 1/28/21 3:07 PM, Philippe Mathieu-Daudé wrote:
> On 1/28/21 6:16 PM, Dr. David Alan Gilbert wrote:
>> * Wainer dos Santos Moschetta (wainersm@redhat.com) wrote:
>>> Fixed error when compiling migration/qemu-file.c with -Werror=maybe-uninitialized
>>> as shown here:
>>>
>>> ../migration/qemu-file.c: In function 'qemu_get_buffer_in_place':
>>> ../migration/qemu-file.c:604:18: error: 'src' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>>>    604 |             *buf = src;
>>>        |             ~~~~~^~~~~
>>> cc1: all warnings being treated as errors
>>>
>>> Signed-off-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
>> Yes, I think I had a discussion with someone about this recently but
>> can't find it;
> Maybe with Thomas, he reported that 2 years ago when building with -O3:
> https://www.mail-archive.com/qemu-devel@nongnu.org/msg599522.html


I saw that error when compiling QEMU with -O3 as well.


>
>> the compiler is technically correct, but the only time
>> it's unitialised is the case where it's result doesn't matter.
>>
>> Still, to shut the compiler up:
>>
>>
>> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>


Thanks David!


>>
>>> ---
>>> Passed on CI: https://gitlab.com/wainersm/qemu/-/pipelines/247801576
>>>
>>>   migration/qemu-file.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/migration/qemu-file.c b/migration/qemu-file.c
>>> index be21518c57..d6e03dbc0e 100644
>>> --- a/migration/qemu-file.c
>>> +++ b/migration/qemu-file.c
>>> @@ -595,7 +595,7 @@ size_t qemu_get_buffer_in_place(QEMUFile *f, uint8_t **buf, size_t size)
>>>   {
>>>       if (size < IO_BUF_SIZE) {
>>>           size_t res;
>>> -        uint8_t *src;
>>> +        uint8_t *src = NULL;
>>>   
>>>           res = qemu_peek_buffer(f, &src, size, 0);
>>>   
>>> -- 
>>> 2.28.0
>>>