On Thu, Jan 23, 2014 at 11:41:18AM -0800, Jonathan Nieder wrote:
> Jeff King wrote:
> > Commit d60c49c (read-cache.c: allow unaligned mapping of the
> > index file, 2012-04-03) introduced helpers to access
> > unaligned data. Let's factor them out to make them more
> > widely available.
> > While we're at it, we'll give the helpers more readable
> > names, add a helper for the "ntohll" form, and add the
> > appropriate Makefile knob.
> Weird. Why wasn't git broken on the relevant platforms before (given
> that no one has been setting NEEDS_ALIGNED_ACCESS for them)?
Because most of our data structures support aligned access. Thomas
mentioned this as a potential issue earlier, and I said in a re-roll
I did not include the NEEDS_ALIGNED_ACCESS patch. I note that we do
not even have a Makefile knob for this, and the code in read-cache.c
has probably never actually been used. Are there real systems that
have a problem? The read-cache code was in support of the index v4
experiment, which did away with the 8-byte padding. So it could be
that we simply don't see it, because everything is currently aligned.
I think it was a bug waiting to surface if index v4 ever got wide use.
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