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Date: Wed, 9 Sep 2015 07:55:57 -0500
From: JimF <jfoug@....net>
To: john-dev@...ts.openwall.com
Subject: Re: Large stack alignment



On 9/9/2015 5:03 AM, magnum wrote:
> On 2015-09-08 21:45, magnum wrote:
>
>> /*
>> * I had to place this in a separate function to avoid having the 
>> unaligned
>> * branch optimized away (even using -O0), since gcc is totally 
>> convinced it
>> * simply can't be unaligned!
>> */
>> void out(char *pt)
>> {
>>     if ((size_t)pt & 31)
>>         printf("%s unaligned!\n", pt);
>>     else
>>         puts(pt);
>> }
>
> Come to think of it, this is troubling: It suggests that the macro 
> form of mem_align() might also be optimized away, doesn't it?!
>
> Also, I'm puzzled anything is optimized away at -O0. But it was - 
> there wasn't even any "%s unaligned!\n" string in the assembly output.
>
I believe this is going to be 2 different cases, but I honestly can not 
say for 100% sure.  In the macro case, we have an lparam expression 
which sets an undefined variable. It must be run.

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