2011/4/28 Ingo Molnar <mingo@xxxxxxx>:
>
> If unsigned char arrays are allocated unaligned then that's another bug i
> suspect that should be fixed. Unaligned access on x86 is not free either -
> there's cycle penalties.
Unsigned char arrays can be stored unaligned. Basically, it depends on
the context in what they were declared. If a preceding field in some
structure ended unaligned then the byte array will start unaligned.
For example:
struct foo
{
char ch;
unsigned char sha1[20];
};
The same on the stack, except the compiler may pack them as it wishes.
So, you have no guarantee here. If you want to make sure all SHA-1 are
aligned properly, sha1 should be declared as ui32: 'uint32_t sha1[5]'.
Dmitry
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