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Date: Tue, 16 Apr 2013 21:32:15 +0200
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: Segfaults probably caused by DEBUG code in memory.c (was: Segfault for linux-x86-native with -DDEBUG added)

Not the same thing. In the normal non-debug code we obviously must do it, because we are re-using one large memory block for many smaller blocks. That is one of mem_alloc_tiny's two reasons to exist.

I attribute Frank's segfaults to a bug in his malloc() but the fix should definitely be there anyway (we might want MEM_ALIGN_CACHE or something else, for other reasons than strict requirements) and it should have been there in the first place.

magnum


On 16 Apr, 2013, at 20:49 , "jfoug" <jfoug@....net> wrote:

> I read the man pages myself, prior to posting that email.  I had started on
> the email, then read the dox.  I almost stopped, to allow others to find the
> 'real' problem.  But I then spotted the bottom of the mem_alloc_tiny
> function (where a huge block is allocated and used).  Since it had the
> alignment 'fix' there, I figured that no matter what the dox list, this is
> something that REALLY must happen, to assure proper alignment.  I had not
> tested the code I posted in the email, I am not where I can do so right now.
> However, it really looked like that code was added to the bottom of the
> function on purpose, so likely it is really a requirement, and the dox are
> misleading, or worse, simply wrong.
> 
> From: magnum [mailto:john.magnum@...hmail.com] 
>> 
>> I can't recall now but to my defense, I may have been misled by the man
> page. The OSX one explicitly says "The >allocated memory is aligned such
> that it can be used for any data type, including AltiVec- and SSE-related
>> types". The Linux one states "...suitably aligned for any kind of variable"
> which apparently is not really true.
> 
> 


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