[PATCH] Initialize the entire obstack struct [BZ #17919]

[pinskia@gmail.com]

> On Feb 3, 2015, at 9:05 AM, Siddhesh Poyarekar <siddhesh@redhat.com> wrote:
> 
>> On Tue, Feb 03, 2015 at 11:49:26AM -0500, Carlos O'Donell wrote:
>> IMO zero-initialized padding, for this case, isn't something you can
>> expect. Therefore I think it's a compiler bug.
> 
> Thanks, I've filed a bug now:
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64923

It is not a glibc or a gcc bug but rather a valgrind one. We are comparing against zero since this is the sign bit. Valgrind does not realize that and gives a warning. 

Thanks,
Andrew

> 
>> I think it's OK to work around this in glibc, but it needs a comment
>> with a reference to the filed gcc bug. I do not think it is valid
>> for gcc on s390x to use the entire bit field along with padding and
>> I believe it could result in incorrect operation.
> 
> Nothing is breaking due to this right now, so we could probably wait
> and see what the gcc folks think of this.
> 
> Siddhesh