Re: [PATCH][next] io_uring: ensure variable ret is initialized to zero

[Jens Axboe]

On 9/26/19 1:33 PM, Dan Carpenter wrote:
> On Thu, Sep 26, 2019 at 11:56:30AM +0200, Jens Axboe wrote:
>> On 9/26/19 11:50 AM, Colin King wrote:
>>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>>>
>>> In the case where sig is NULL the error variable ret is not initialized
>>> and may contain a garbage value on the final checks to see if ret is
>>> -ERESTARTSYS.  Best to initialize ret to zero before the do loop to
>>> ensure the ret does not accidentially contain -ERESTARTSYS before the
>>> loop.
>>
>> Oops, weird it didn't complain. I've folded in this fix, as that commit
>> isn't upstream yet. Thanks!
> 
> There is a bug in GCC where at certain optimization levels, instead of
> complaining, it initializes it to zero.

That's awfully nice of it ;-)

Tried with -O0 and still didn't complain for me.

$ gcc --version
gcc (Ubuntu 9.1.0-2ubuntu2~18.04) 9.1.0

Tried gcc 5/6/7/8 as well. Might have to go look at what code it's
generating.

-- 
Jens Axboe