From: Johannes Schindelin <johannes.schindelin@xxxxxx> In 03267e8656c (commit: discard partial cache before (re-)reading it, 2022-11-08), a memory leak was plugged by discarding any partial index before re-reading it. The problem with this memory leak fix is that it was based on an incomplete understanding of the logic introduced in 7168624c353 (Do not generate full commit log message if it is not going to be used, 2007-11-28). That logic was introduced to add a shortcut when committing without editing the commit message interactively. A part of that logic was to ensure that the index was read into memory: if (!active_nr && read_cache() < 0) die(...) Translation to English: If the index has not yet been read, read it, and if that fails, error out. That logic was incorrect, though: It used `!active_nr` as an indicator that the index was not yet read. Usually this is not a problem because in the vast majority of instances, the index contains at least one entry. And it was natural to do it this way because at the time that condition was introduced, the `index_state` structure had no explicit flag to indicate that it was initialized: This flag was only introduced in 913e0e99b6a (unpack_trees(): protect the handcrafted in-core index from read_cache(), 2008-08-23), but that commit did not adjust the code path where no index file was found and a new, pristine index was initialized. Now, when the index does not contain any entry (which is quite common in Git's test suite because it starts quite a many repositories from scratch), subsequent calls to `do_read_index()` will mistake the index not to be initialized, and read it again unnecessarily. This is a problem because after initializing the empty index e.g. the `cache_tree` in that index could have been initialized before a subsequent call to `do_read_index()` wants to ensure an initialized index. And if that subsequent call mistakes the index not to have been initialized, it would lead to leaked memory. The correct fix for that memory leak is to adjust the condition so that it does not mistake `active_nr == 0` to mean that the index has not yet been read. Using the `initialized` flag instead, we avoid that mistake, and as a bonus we can fix a bug at the same time that was introduced by the memory leak fix: When deleting all tracked files and then asking `git commit -a -m ...` to commit the result, Git would internally update the index, then discard and re-read the index undoing the update, and fail to commit anything. This fixes https://github.com/git-for-windows/git/issues/4462 Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx> --- builtin/commit.c | 7 ++----- t/t2200-add-update.sh | 11 +++++++++++ 2 files changed, 13 insertions(+), 5 deletions(-) diff --git a/builtin/commit.c b/builtin/commit.c index 65a5c0e29d5..4cf2baaf943 100644 --- a/builtin/commit.c +++ b/builtin/commit.c @@ -998,11 +998,8 @@ static int prepare_to_commit(const char *index_file, const char *prefix, struct object_id oid; const char *parent = "HEAD"; - if (!the_index.cache_nr) { - discard_index(&the_index); - if (repo_read_index(the_repository) < 0) - die(_("Cannot read index")); - } + if (!the_index.initialized && repo_read_index(the_repository) < 0) + die(_("Cannot read index")); if (amend) parent = "HEAD^1"; diff --git a/t/t2200-add-update.sh b/t/t2200-add-update.sh index be394f1131a..c01492f33f8 100755 --- a/t/t2200-add-update.sh +++ b/t/t2200-add-update.sh @@ -197,4 +197,15 @@ test_expect_success '"add -u non-existent" should fail' ' ! grep "non-existent" actual ' +test_expect_success '"commit -a" implies "add -u" if index becomes empty' ' + git rm -rf \* && + git commit -m clean-slate && + test_commit file1 && + rm file1.t && + test_tick && + git commit -a -m remove && + git ls-tree HEAD: >out && + test_must_be_empty out +' + test_done -- gitgitgadget
