Hi Peff,
On Mon, 8 Dec 2014, Jeff King wrote:
> On Mon, Dec 08, 2014 at 12:35:27PM +0100, Johannes Schindelin wrote:
>
> > On Mon, 8 Dec 2014, Duy Nguyen wrote:
> >
> > > On Mon, Dec 08, 2014 at 12:57:06AM -0500, Jeff King wrote:
> > > > I do admit that I am tempted to teach index-pack to always NUL-terminate
> > > > objects in memory that we feed to fsck, just to be on the safe side. It
> > > > doesn't cost much, and could prevent a silly mistake (either in the
> > > > future, or one that I missed in my analysis).
> > >
> > > I think I'm missing a "but.." here.
> >
> > The "but..."s I have are:
> >
> > 1) we potentially waste space, and
>
> I think this can be ignored. It's 1 byte per object, and only while we
> keep the object in RAM. Also, we already do it for buffers read from
> read_sha1_file, so when you run "git log" every commit buffer we keep in
> RAM is already doing this (and has been since basically day one).
Fine with me.
> > 2) I would like to make really certain, preferably with static analysis,
> > that fsck_object() only receives buffers that are NUL terminated, and
> > that no call path is missed.
>
> I know this is not as good as a real static analysis, but I was
> concerned about this exact thing about a year ago (I think in relation
> to commit parsing for pretty-printing) and traced all of the paths
> through which you can get an object; they all end up in the same few
> code paths that all xmallocz: unpack_sha1_file for loose objects,
> unpack_compressed_entry for pack bases, and patch_delta for deltas.
Thank you for sharing the analysis. This is exactly what I was looking
for.
> Index-pack and unpack-objects are the odd men out here because they are
> processing objects that are not actually in the repository yet. I think
> the spots Duy pointed out probably cover index-pack. It looks like
> builtin/unpack-objects.c:get_data needs the same treatment.
I just started working on that. To see the progress, please have a look
here:
https://github.com/dscho/git/pull/5
Ciao,
Dscho
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