Re: Git v2.13.1 SHA1 very broken

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Jun 5, 2017, 21:05 UTC
Message-ID: <CACBZZX6vOr+ZjUaAf8i1xdjEFfY_Exj+_Xn2-1u0RcWoLy+X1g@mail.gmail.com>
In-Reply-To: <20170605203409.GB25777@dinwoodie.org>

On Mon, Jun 5, 2017 at 10:34 PM, Adam Dinwoodie <adam@dinwoodie.org> wrote:

Show 25 quoted lines

> I'm trying to compile Git v2.13.1 to release for Cygwin, but it appears
> a010391 ("sha1dc: update from upstream", 2017-05-20) is breaking a very
> significant number of test cases in both 32-bit and 64-bit Cygwin
> builds.
>
> The first failure is t0000.46 "validate object ID of a known tree"; output with
> -x and -v is below, although it's not very interesting:
>
>     expecting success:
>             test "$tree" = 7bb943559a305bdd6bdee2cef6e5df2413c3d30a
>
>     ++ test ceb282701536fe61bea01075664405caa7d6343f = 7bb943559a305bdd6bdee2cef6e5df2413c3d30a
>     + test_eval_ret_=1
>     + want_trace
>     + test t = t
>     + test t = t
>     + set +x
>     error: last command exited with $?=1
>     not ok 46 - validate object ID of a known tree
>     #
>     #               test "$tree" = 7bb943559a305bdd6bdee2cef6e5df2413c3d30a
>     #
>
> I have no idea where to even begin debugging this, but I'm happy to take
> pointers / try things out on my box.

That looks scary, can you please comment out this:

    #define SHA1DC_ALLOW_UNALIGNED_ACCESS

In sha1dc/sha1.c and see if that helps, alternatively comment out the ifdefs guarded by "#ifdef _MSC_VER" calls in sha1dc/sha1.c

The functional differences between 2.13.0 and 2.13.1 on that platform should be none aside from possibly those changes, unless I've missed something.