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Re: [PATCH] i386: Increase MALLOC_ALIGNMENT to 16 [BZ #21120]


On Thu, Jun 29, 2017 at 1:03 PM, Carlos O'Donell <carlos@redhat.com> wrote:
> On 06/29/2017 02:43 PM, H.J. Lu wrote:
>> On Thu, Jun 29, 2017 at 11:11 AM, Carlos O'Donell <carlos@redhat.com> wrote:
>>> On 06/29/2017 02:06 PM, H.J. Lu wrote:
>>>> On Thu, Jun 29, 2017 at 10:55 AM, Carlos O'Donell <carlos@redhat.com> wrote:
>>>>> On 06/29/2017 01:30 PM, H.J. Lu wrote:
>>>>>> GCC 7 changed the definition of max_align_t on i386:
>>>>>>
>>>>>> https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=9b5c49ef97e63cc63f1ffa13baf771368105ebe2
>>>>>>
>>>>>> As a result, glibc malloc no longer returns memory blocks which are as
>>>>>> aligned as max_align_t requires.
>>>>>>
>>>>>> This causes malloc/tst-malloc-thread-fail to fail with an error like this
>>>>>> one:
>>>>>>
>>>>>> error: allocation function 0, size 144 not aligned to 16
>>>>>>
>>>>>> This patch increases the malloc alignment to 16 for i386.
>>>>>>
>>>>>> Tested on i386 with GCC 7 and on x86-64.  OK for master?
>>>>>>
>>>>>> H.J.
>>>>>> ---
>>>>>>       [BZ #21120]
>>>>>>       * sysdeps/generic/malloc-alignment.h: New file.
>>>>>>       * sysdeps/i386/malloc-alignment.h: Likewise.
>>>>>>       * sysdeps/generic/malloc-machine.h: Include <malloc-alignment.h>.
>>>>>
>>>>> Please use malloc-machine.h which was the previous header that provided
>>>>> machine-dependent malloc definitions. That way we remain consistent across
>>>>> releases and make it easier to backport such changes without adding a new
>>>>> header.
>>>>
>>>> It won't work too well for Hurd since we have
>>>>
>>>> ./sysdeps/generic/malloc-machine.h
>>>> ./sysdeps/mach/hurd/malloc-machine.h
>>>> ./sysdeps/nptl/malloc-machine.h
>>>>
>>>> What will Hurd/i386 get?   malloc-alignment.h handles it automatically.
>>>
>>> If your patch made Hurd/i386 use MALLOC_ALIGNMENT of 16 then a new patch
>>> using malloc-machine.h would set MALLOC_ALIGNMENT to 16 in
>>> systeps/mach/hurd/malloc-machine.h?
>>>
>>
>> This assumes that mach/hurd == i386.  Also I don't like define
>> MALLOC_ALIGNMENT to 16 for i386 in 2 different places.
>> Since
>>
>> ./sysdeps/generic/malloc-machine.h
>> ./sysdeps/mach/hurd/malloc-machine.h
>> ./sysdeps/nptl/malloc-machine.h
>>
>> malloc-machine.h is not pure processor specific. It is also OS
>> specific.  I prefer to define MALLOC_ALIGNMENT to 16 for i386
>> in a processor specific header file.
>
> Add a sysdeps/mach/hurd/i386, which is an os/machine directory.
>
> Similarly for i386?
>

Are you suggesting 3 i386 header files to define MALLOC_ALIGNMENT?

1. generic i386.
2. nptl i386.
3. hurd i386.

That is very weird.


-- 
H.J.


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