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Date: Tue, 16 Apr 2013 19:40:13 +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)
Yeah, this is it. My bad. The rationale was to make memory debugging a lot easier under -DDEBUG but it was really *supposed* to still maintain requested alignment. Sometimes I amaze myself :-(
magnum
On 16 Apr, 2013, at 18:34 , jfoug <jfoug@....net> wrote:
> From: Frank Dittrich [mailto:frank_dittrich@...mail.com]
>>
>> No segfaults.
>> So I guess the -DDEBUG code in memory.c causes memory locations to be not aligned as expected.
>
> void *mem_alloc_tiny(size_t size, size_t align)
> {
> #ifdef DEBUG
> void *res;
>
> +++ res = mem_alloc(size);
> add_memory_link(res);
> return res;
> #else
>
> The line with +++. There is there assurance of alignment? Or do we need to allocate size+align, use that pointer in the add_memory_link, and then 'fix' the pointer?
>
>
> void *mem_alloc_tiny(size_t size, size_t align)
> {
> #ifdef DEBUG
> void *res;
>
> res = mem_alloc(size+align);
> add_memory_link(res);
> res += (align-1);
> res -= (size_t)(res & (align-1));
> return res;
> #else
>
> Look at the bottom of the mem_alloc_tiny. IT does not use the return from mem_alloc (which is return from malloc), but fixes it up.
>
> p = mem_alloc(size + mask);
> add_memory_link((void*)p);
> p += mask;
> p -= (size_t)p & mask;
> return p;
>
>
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