glibc 2.21 - Machine maintainers, please test your machines.

[Carlos O'Donell]

On 01/25/2015 06:05 PM, H.J. Lu wrote:
> On Sun, Jan 25, 2015 at 2:10 PM, Chris Metcalf <cmetcalf@ezchip.com> wrote:
>> On 1/25/2015 4:51 PM, H.J. Lu wrote:
>>
>>> This is for x86.  Each target can do something like it if needed.
>>
>>
>> This does change the ABI for existing code, however, which may legitimately
>> have sem_t objects that are only aligned to 4-byte boundaries.  Your change
>> is a good idea for new platforms.  I suppose we could also do something
>> with symbol versioning to use it for existing 32-bit platforms with
>> 64-bit atomics, too.  So there seem to be multiple fixes we can consider.
>>
> 
> It doesn't change the size, only increases alignment from 4 bytes to 8 bytes.
> It may not work on all targets.  It works for x32.

How can you change the alignment?

That will break applications that embedded a sem_t in other structures by
changing the size of those structures as they expand to account for the
changed object alignment?

Cheers,
Carlos.