Re: [PATCH v4 08/23] ewah: compressed bitmap implementation

Jeff King wrote:

Here's a patch series (on top of jk/pack-bitmap, naturally) that lets
t5310 pass there. I assume the ARM problem is the same, though seeing
the failure in realloc() is unexpected. Can you try it on both your
platforms with these patches?

Thanks.  Trying it out now.

[...]

quoted

Hopefully it's possible to get the alignment right in the caller
and tweak the signature to require that instead of using unaligned
reads like this.  There's still something wrong after this patch ---
the new result is a NULL pointer dereference in t5310.7 "enumerate
--objects (full bitmap)".

After my patches, t5310 runs fine for me. I didn't try your patch, but
mine are similar. Let me know if you still see the problem (there may
simply be a bug in yours, but I didn't see it).

I had left out a cast to unsigned, producing an overflow.

My main worry about the patches is that they will probably run into
an analagous problem to the one that v1.7.12-rc0~1^2~2 (block-sha1:
avoid pointer conversion that violates alignment constraints,
2012-07-22) solved.  By casting the pointer to (uint32_t *) we are
telling the compiler it is 32-bit aligned (C99 section 6.3.2.3).

Thanks,
Jonathan