Delitifier broken (Re: diff-core segfault)

From: Junio C Hamano <junkio@cox.net>
Date: Dec 12, 2005, 18:59 UTC
Message-ID: <7virtui1kj.fsf_-_@assigned-by-dhcp.cox.net>
In-Reply-To: <7vmzj6i206.fsf@assigned-by-dhcp.cox.net>

Junio C Hamano <junkio@cox.net> writes:

Show 7 quoted lines

> Darrin Thompson <darrint@progeny.com> writes:
>
>> Could someone confirm that this exists on more recent git heads and fix
>> if needed?
>
> (1) Yup.  I can reproduce it.
> (2) Will look into it when able.

This is not just "diff". Our deltify code is half-broken, and in the worst case this can corrupt our packs if an empty blob is involved.

The problem is if from_size or to_size is empty, it does not produce any.

        if (!from_size || !to_size || delta_prepare(from_buf, from_size, &bdf))
                return NULL;

I think either we need to make the users more careful or fix deltifier to produce trivial delta. I'd vote for the latter; let me rig up something.