[ping] [patch 4/5] fix bugs with -fstrict-volatile-bitfields and packed structures

[Sandra Loosemore]

On 06/24/2013 06:31 AM, Richard Biener wrote:
> On Sun, Jun 23, 2013 at 6:17 PM, Sandra Loosemore
> <sandra@codesourcery.com> wrote:
>> On 06/16/2013 01:08 PM, Sandra Loosemore wrote:
>>>
>>> This part of the patch series fixes problems with bad code being emitted
>>> for unaligned bitfield accesses, as reported in PRs 48784, 56341, and
>>> 56997.  A secondary goal of this patch was making the bitfield store and
>>> extract code follow similar logic, at least for the parts relating to
>>> -fstrict-volatile-bitfield handling.
>>
>>
>> Is it possible to get this part of the patch series reviewed?  Except for
>> the documentation change, it is independent of the controversy surrounding
>> part 3 regarding whether the target ABI or C/C++ standard should take
>> precedence when they conflict, and is independent of any further patches to
>> change the default -fstrict-volatile-bitfields setting.  If the rest of the
>> patch is approved, I'll take care to fix up invoke.texi to accurately
>> reflect the behavior of the approved patches before checking anything in.
>>
>> http://gcc.gnu.org/ml/gcc-patches/2013-06/msg00911.html
>
> It looks sensible to me but I'd like to have Eric have a 2nd look as he is most
> familiar with this code.

OK.  Meanwhile there have been some comments in PR56997 indicating that 
this patch still isn't quite right, so I am going to have to tinker with 
it a bit more.

To tell the truth, I've also been somewhat unhappy with the current 
version; I'd much rather restructure the code further so that we check 
for the -fstrict-volatile-bitfields case once at the top instead of 
having to special-case 3 or 4 places deep down in the code to do 
something different.  The current version seemed like a more 
conservative incremental change, but if it's still not correct it might 
be better to bite the bullet on the refactoring.  Anyway, I will spend a 
few more days on it and post a revised patch for review.

-Sandra