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	Sun, 24 Nov 2013 18:42:46 +0200 (EET)
From: Tomi Ollila <tomi.ollila@iki.fi>
To: David Bremner <david@tethera.net>, notmuch@notmuchmail.org
Subject: Re: notmuch sha1 implementation broken on (some) big-endian
	architectures
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Date: Sun, 24 Nov 2013 18:42:46 +0200
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On Sun, Nov 24 2013, David Bremner <david@tethera.net> wrote:

> The following code, when linked with libnotmuch.a and libutil.a does a
> passable imitation of sha1sum on amd64 (and I guess also i386) but
> computes a different digest on powerpc and probably sparc and s390x.
>
> In the long run we should maybe outsource hash computations to
> e.g. librhash, but I'd like a simpler fix for 0.17, if possible
>
> P.S. I blame Austin for adding the "missing-headers" test which found
> this bug ;).

This is interesting problem, I would have guessed that this would
fails on LITTLE_ENDIAN machines easier, if ever...

... especially as there is line

lib/libsha1.c:52:#if (PLATFORM_BYTE_ORDER == IS_LITTLE_ENDIAN)

... but...

I could not find any (other) matches for PLATFORM_BYTE_ORDER nor
IS_LITTLE_ENDIAN in source code or in /usr/include/**/*.h or
in /usr/lib/gcc/**/*.h

I did some testing and it seems that 
#if (FOOOO == BBBAAARRR)
<code>
#endif

will have <code> in output file in case neither of the above are
defined... :/

So, this could work:

#if <endian.h>  // for BYTE_ORDER && LITTLE_ENDIAN

and then

#if (BYTE_ORDER == LITTLE_ENDIAN)
...

to replace lib/libsha1.c:53 (53 now after endian.h added)


Please test on BIG_ENDIAN machine...


In case this works, then we'd need to inform users that their
long/missing Message ID:s are now coded differently in their
databases...


Tomi