Re: wrong SHA-256 result with optimized assembly on i386 ([pycryptopp] #24: SHA256 failure on NetBSD with multiple segments)

Hey that's wonderful! I really appreciate the explanation. I love
hearing about these sorts of fixes.

On Jul 5, 11:14 am, "Wei Dai" <wei...@...> wrote:
> Thanks for the sample program. I've checked in the fix to sha.cpp.
>
> The cause of the bug, if anyone is curious, was that I assumed a certain
> pointer would be word-aligned, and used its least significant bit to store
> whether or not the CPU supports SSE2. It turns out that I forgot that
> pointer isn't necessarily word-aligned, so when that happens, the code would
> incorrectly use the SSE2 code path. And for some reason, the SSE2
> instructions didn't cause an exception on non-SSE2 CPUs.

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