Re: [ANNOUNCEMENT] Uploads for 12 August

[Ken Brown <kbrown@cornell.edu>]

On 8/14/2013 7:59 AM, Corinna Vinschen wrote:
> On Aug 14 13:33, Corinna Vinschen wrote:
>> On Aug 14 12:53, Corinna Vinschen wrote:
>>> On Aug 14 06:28, Ken Brown wrote:
>>>> On 8/14/2013 5:16 AM, Corinna Vinschen wrote:
>>>>> On Aug 14 10:10, Corinna Vinschen wrote:
>>>>>> On Aug 13 18:00, Ken Brown wrote:
>>>>>>> On 8/13/2013 2:26 PM, Corinna Vinschen wrote:
>>>>>>>> What function is not implemented?  Is that something we can fix,
>>>>>>>> perhaps in the Cygwin DLL?
>>>>>>>
>>>>>>> It's memalign, or at least that's what it was in 2007.  See
>>>>>>>
>>>>>>>    http://cygwin.com/ml/cygwin/2007-02/msg00678.html
>>>>>>
>>>>>> So it's using its own malloc but we don't support overriding other
>>>>>> functions besides malloc/realloc/calloc/free.
>>>>>>
>>>>>> In theory we could do that in future.  We still have room for 10 (x86)
>>>>>> resp. 12 (x86_64) pointers in the per_process structure, which could be
>>>>>> used for this purpose.  This would only require applications which need
>>>>>> this feature to be rebuilt with the next Cygwin version providing these
>>>>>> pointers.
>>>>>
>>>>> More precisely, they have to be rebuild using crt0.o from the next
>>>>> Cygwin release, and they would have to run under the next Cygwin
>>>>> release.  If you omit one step, you're back to the current behaviour.
>>>>>
>>>>>> But we shouldn't waste those unused slots either, so the number of
>>>>>> overridable functions should be kept small.  In theory we have mallopt,
>>>>>> mallinfo, posix_memalign, memalign, and valloc.
>>>>>>
>>>>>> I guess we can skip mallopt and mallinfo since they are pretty
>>>>>> seldomly used in user-provided malloc implementations.
>>>>>>
>>>>>> Memalign is an old, deprecated function, so I wonder why it's used at
>>>>>> all.  GSlice should use posix_memalign instead.  Yaakov, is there an
>>>>>> option to use posix_memalign rather than memalign?
>>>>
>>>> I just checked the glib source, and it does use posix_memalign if
>>>> it's available.  I was quoting a 2007 discussion when I said it was
>>>> memalign that GSlice wanted to use.
>>>
>>> Given that, we should perhaps skip the memalign override.
>>
>> On second (third? fourth?) thought, I think we should do this with
>> posix_memalign only.  valloc is just as obsolete as posix_memalign.
>
> I applied the patch to allow overriding posix_memalloc only, and I'm
> building snapshots right now.  For testing, this requires to rebuild
> either emacs, or glib, or both, I'm not sure.  Make sure to link against
> the new crt0.o/libcygwin.a and use the new Cygwin DLL for testing.

Thanks.  It should only be emacs that needs rebuilding; glib doesn't 
supply its own malloc, but emacs does.  I'll test it and report back.

Ken

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