This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: Add uninitialized attribute?
* Andrew Haley:
> On 08/21/2010 10:43 AM, Florian Weimer wrote:
>> * H. J. Lu:
>>
>>> Sometime I have to do
>>>
>>> int x = 0;
>>>
>>> to silence gcc from uninitialized warnings when I know it is
>>> unnecessary.
>>
>> I guess the official idiom is
>>
>> int x = x;
>>
>> and it is somewhat used in the GNU project although it is not
>> portable.
>
> Ewww, yuck. I think this'll get a read from uninitialized message from
> Valgrind. It's undefined behaviour too.
GCC has specific code to deal with this construct. I don't think the
undefined load will actually end up in machine code, so valgrind won't
see it. And while it is undefined according to the standard (that's
why I called it not portable), it appears to be a supported GCC
extension. (This is based on the existance of the -Wself-init option,
it's not explicitly documented as an extension AFAICT.)
That being said, I don't like it, either.