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Re: [PATCH] i386: Increase MALLOC_ALIGNMENT to 16 [BZ #21120]
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.
--
H.J.