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Preparation for SHA-256 migration continues.
* bc/hash-independent-tests-part-8: (21 commits)
t6024: update for SHA-256
t6006: make hash size independent
t6000: abstract away SHA-1-specific constants
t5703: make test work with SHA-256
t5607: make hash size independent
t5318: update for SHA-256
t5515: make test hash independent
t5321: make test hash independent
t5313: make test hash independent
t5309: make test hash independent
t5302: make hash size independent
t4060: make test work with SHA-256
t4211: add test cases for SHA-256
t4211: move SHA-1-specific test cases into a directory
t4013: make test hash independent
t3311: make test work with SHA-256
t3310: make test work with SHA-256
t3309: make test work with SHA-256
t3308: make test work with SHA-256
t3206: make hash size independent
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Use the proper pack constants defined in lib-pack.sh to make this test
work with SHA-256.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When we're resolving a REF_DELTA, we compare-and-swap its type from
REF_DELTA to whatever real type the base object has, as discussed in
ab791dd138 (index-pack: fix race condition with duplicate bases,
2014-08-29). If the old type wasn't a REF_DELTA, we consider that a
BUG(). But as discussed in that commit, we might see this case whenever
we try to resolve an object twice, which may happen because we have
multiple copies of the base object.
So this isn't a bug at all, but rather a sign that the input pack is
broken. And indeed, this case is triggered already in t5309.5 and
t5309.6, which create packs with delta cycles and duplicate bases. But
we never noticed because those tests are marked expect_failure.
Those tests were added by b2ef3d9ebb (test index-pack on packs with
recoverable delta cycles, 2013-08-23), which was leaving the door open
for cases that we theoretically _could_ handle. And when we see an
already-resolved object like this, in theory we could keep going after
confirming that the previously resolved child->real_type matches
base->obj->real_type. But:
- enforcing the "only resolve once" rule here saves us from an
infinite loop in other parts of the code. If we keep going, then the
delta cycle in t5309.5 causes us to loop infinitely, as
find_ref_delta_children() doesn't realize which objects have already
been resolved. So there would be more changes needed to make this
case work, and in the meantime we'd be worse off.
- any pack that triggers this is broken anyway. It either has a
duplicate base object, or it has a cycle which causes us to bring in
a duplicate via --fix-thin. In either case, we'd end up rejecting
the pack in write_idx_file(), which also detects duplicates.
So the tests have little value in documenting what we _could_ be doing
(and have been neglected for 6+ years). Let's switch them to confirming
that we handle this case cleanly (and switch out the BUG() for a more
informative die() so that we do so).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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These tests rely on creating packs with specially named objects which
are necessarily dependent on the hash used. Skip these tests if we're
not using SHA-1.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The previous commit added tests to show that index-pack
correctly bails in unrecoverable situations. There are some
situations where the data could be recovered, but it is not
currently:
1. If we can break the cycle using an object from another
pack via --fix-thin.
2. If we can break the cycle using a duplicate of one of
the objects found in the same pack.
Note that neither of these is particularly high priority; a
delta cycle within a pack should never occur, and we have no
record of even a buggy git implementation creating such a
pack.
However, it's worth adding these tests for two reasons. One,
to document that we do not currently handle the situation,
even though it is possible. And two, to exercise the code
that runs in this situation; even though it fails, by
running it we can confirm that index-pack detects the
situation and aborts, and does not misbehave (e.g., by
following the cycle in an infinite loop).
In both cases, we hit an assert that aborts index-pack.
Signed-off-by: Jeff King <peff@peff.net>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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If we receive a broken or malicious pack from a remote, we
will feed it to index-pack. As index-pack processes the
objects as a stream, reconstructing and hashing each object
to get its name, it is not very susceptible to doing the
wrong with bad data (it simply notices that the data is
bogus and aborts).
However, one question raised on the list is whether it could
be susceptible to problems during the delta-resolution
phase. In particular, can a cycle in the packfile deltas
cause us to go into an infinite loop or cause any other
problem?
The answer is no.
We cannot have a cycle of delta-base offsets, because they
go only in one direction (the OFS_DELTA object mentions its
base by an offset towards the beginning of the file, and we
explicitly reject negative offsets).
We can have a cycle of REF_DELTA objects, which refer to
base objects by sha1 name. However, index-pack does not know
these sha1 names ahead of time; it has to reconstruct the
objects to get their names, and it cannot do so if there is
a delta cycle (in other words, it does not even realize
there is a cycle, but only that there are items that cannot
be resolved).
Even though we can reason out that index-pack should handle
this fine, let's add a few tests to make sure it behaves
correctly.
Signed-off-by: Jeff King <peff@peff.net>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Junio C Hamano
brian m. carlson
Jeff King