[PATCH 2/2] unpack_trees(): protect the handcrafted in-core index from read_cache()
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Aug 23, 2008, 19:57 UTC
- Message-ID
- <7vbpzjy05x.fsf_-_@gitster.siamese.dyndns.org>
- In-Reply-To
- <7vk5e7y0a0.fsf@gitster.siamese.dyndns.org>
unpack_trees() rebuilds the in-core index from scratch by allocating a new structure and finishing it off by copying the built one to the final index.
The resulting in-core index is Ok for most use, but read_cache() does not recognize it as such. The function is meant to be no-op if you already have loaded the index, until you call discard_cache().
This change the way read_cache() detects an already initialized in-core index, by introducing an extra bit, and marks the handcrafted in-core index as initialized, to avoid this problem.
A better fix in the longer term would be to change the read_cache() API so that it will always discard and re-read from the on-disk index to avoid confusion. But there are higher level API that have relied on the current semantics, and they and their users all need to get converted, which is outside the scope of 'maint' track.
An example of such a higher level API is write_cache_as_tree(), which is used by git-write-tree as well as later Porcelains like git-merge, revert and cherry-pick. In the longer term, we should remove read_cache() from there and add one to cmd_write_tree(); other callers expect that the in-core index they prepared is what gets written as a tree so no other change is necessary for this particular codepath.
The original version of this patch marked the index by pointing an otherwise wasted malloc'ed memory with o->result.alloc, but this version uses Linus's idea to use a new "initialized" bit, which is conceptually much cleaner.
Signed-off-by: Junio C Hamano <gitster@pobox.com> --- cache.h | 3 ++- read-cache.c | 4 +++- t/t7605-merge-resolve.sh | 2 +- unpack-trees.c | 1 + 4 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/cache.h b/cache.h index 2475de9..884fae8 100644 --- a/cache.h +++ b/cache.h @@ -222,7 +222,8 @@ struct index_state { struct cache_tree *cache_tree; time_t timestamp; void *alloc; - unsigned name_hash_initialized : 1; + unsigned name_hash_initialized : 1, + initialized : 1; struct hash_table name_hash; }; diff --git a/read-cache.c b/read-cache.c index 2c03ec3..35fec46 100644 --- a/read-cache.c +++ b/read-cache.c @@ -1155,7 +1155,7 @@ int read_index_from(struct index_state *istate, const char *path) size_t mmap_size; errno = EBUSY; - if (istate->alloc) + if (istate->initialized) return istate->cache_nr; errno = ENOENT; @@ -1195,6 +1195,7 @@ int read_index_from(struct index_state *istate, const char *path) * index size */ istate->alloc = xmalloc(estimate_cache_size(mmap_size, istate->cache_nr)); + istate->initialized = 1; src_offset = sizeof(*hdr); dst_offset = 0; @@ -1247,6 +1248,7 @@ int discard_index(struct index_state *istate) cache_tree_free(&(istate->cache_tree)); free(istate->alloc); istate->alloc = NULL; + istate->initialized = 0; /* no need to throw away allocated active_cache */ return 0; diff --git a/t/t7605-merge-resolve.sh b/t/t7605-merge-resolve.sh index 5c53608..f1f86dd 100755 --- a/t/t7605-merge-resolve.sh +++ b/t/t7605-merge-resolve.sh @@ -27,7 +27,7 @@ test_expect_success 'setup' ' git tag c3 ' -test_expect_failure 'merge c1 to c2' ' +test_expect_success 'merge c1 to c2' ' git reset --hard c1 && git merge -s resolve c2 && test "$(git rev-parse c1)" != "$(git rev-parse HEAD)" && diff --git a/unpack-trees.c b/unpack-trees.c index cba0aca..ef21c62 100644 --- a/unpack-trees.c +++ b/unpack-trees.c @@ -376,6 +376,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options state.refresh_cache = 1; memset(&o->result, 0, sizeof(o->result)); + o->result.initialized = 1; if (o->src_index) o->result.timestamp = o->src_index->timestamp; o->merge_size = len;
-- 1.6.0.51.g078ae