Re: [PATCH 4/9] repository: add repo reference to index_state
From: Elijah Newren <hidden>
Date: 2021-01-20 17:48:12
On Wed, Jan 20, 2021 at 8:54 AM Derrick Stolee via GitGitGadget [off-list ref] wrote:
From: Derrick Stolee <redacted> It will be helpful to add behavior to index opertations that might
s/opertations/operations/
quoted hunk ↗ jump to hunk
trigger an object lookup. Since each index belongs to a specific repository, add a 'repo' pointer to struct index_state that allows access to this repository. This will prevent future changes from needing to pass an additional 'struct repository *repo' parameter and instead rely only on the 'struct index_state *istate' parameter. Signed-off-by: Derrick Stolee <redacted> --- cache.h | 1 + repository.c | 4 ++++ 2 files changed, 5 insertions(+)diff --git a/cache.h b/cache.h index 71097657489..f9c7a603841 100644 --- a/cache.h +++ b/cache.h@@ -328,6 +328,7 @@ struct index_state { struct ewah_bitmap *fsmonitor_dirty; struct mem_pool *ce_mem_pool; struct progress *progress; + struct repository *repo; }; /* Name hashing */diff --git a/repository.c b/repository.c index a4174ddb062..67a4c1da2d9 100644 --- a/repository.c +++ b/repository.c@@ -264,6 +264,10 @@ int repo_read_index(struct repository *repo) if (!repo->index) repo->index = xcalloc(1, sizeof(*repo->index)); + /* Complete the double-reference */ + if (!repo->index->repo) + repo->index->repo = repo; + return read_index_from(repo->index, repo->index_file, repo->gitdir); } --gitgitgadget
Since we have repo->index and we have index->repo, which are intended to be circular...what if they aren't? Do we want or need to add assertions anywhere that repo == repo->index->repo or that index == index->repo->index ? My initial implementations of --remerge-diff[1] played around with creating a second repo, with a different primary object store but everything else the same. The index for the two repository objects was thus the same, and thus clearly would have violated this assumed invariant for one of the two repos. I discarded that initial implementation (which I didn't quite have working) because I discovered tmp-objdir.h and was able to add some tmp_objdir_make_primary() and tmp_objdir_remove_as_primary() functions that merely altered the existing repo's primary object store, but I'm curious if there might be other cases of folks doing stuff that might have weird failures with this new invariant. It's entirely possible that --remerge-diff was just so different, and I was so unfamiliar with repo objects (and still kind of am) that I was just doing weird stuff no one has done before, so perhaps no additional checks are needed -- I'm just throwing my gut question out there as food for thought. [1] I have not yet submitted `--remerge-diff` to the list; you haven't missed anything. I'm waiting for merge-ort to be submitted, reviewed, and merged first. It's the remerge-diff branch in my fork on GitHub if anyone is curious, though.