Re: [PATCH maint-1.6.5] block-sha1: avoid unaligned accesses on some big-endian systems

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Jul 14, 2012, 19:55 UTC
Message-ID: <CA+55aFwKYhUtXfaRcbOmMsvQW8p+h8N9PKpxW_y1kj6L=FQQNw@mail.gmail.com>
In-Reply-To: <20120714195022.GB23242@burratino>

On Sat, Jul 14, 2012 at 12:50 PM, Jonathan Nieder <jrnieder@gmail.com> wrote:

> After the patch, what reason does gcc have to expect that 'block' is
> 32-bit aligned except when it is?  The code (including the code I
> didn't touch) never casts from char * to int * except in get/put_be32
> on arches that don't mind unaligned accesses.

Ahh. I was looking at the cast you added:

    blk_SHA1_Block(ctx, (const unsigned char *) ctx->W);

but I guess that if gcc inlines that and sees the original int type, it doesn't matter, because that *is* aligned.

So it's ok, but please just make blk_SHA1_Block() take a "const void *" instead and that cast can go away.

               Linus