From: "SZEDER Gábor" <szeder.dev@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org, "SZEDER Gábor" <szeder.dev@gmail.com>
Subject: [PATCH] commit-slab: clarify slabname##_peek()'s return value
Date: Tue, 10 Mar 2020 16:30:49 +0100 [thread overview]
Message-ID: <20200310153049.3482-1-szeder.dev@gmail.com> (raw)
Ever since 862e730ec1 (commit-slab: introduce slabname##_peek()
function, 2015-05-14) the slabname##_peek() function is documented as:
This function is similar to indegree_at(), but it will return NULL
until a call to indegree_at() was made for the commit.
This, however, is usually not the case. If indegree_at() allocates
memory, then it will do so not only for the single commit it got as
parameter, but it will allocate a whole new, ~512kB slab. Later on,
if any other commit's 'index' field happens to point into an already
allocated slab, then indegree_peek() for such a commit will return a
valid non-NULL pointer, pointing to a zero-initialized location in the
slab, even if no indegree_at() call has been made for that commit yet.
Update slabname##_peek()'s documentation to clarify this.
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
---
commit-slab.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/commit-slab.h b/commit-slab.h
index 69bf0c807c..05b3f2804e 100644
--- a/commit-slab.h
+++ b/commit-slab.h
@@ -24,7 +24,12 @@
* - int *indegree_peek(struct indegree *, struct commit *);
*
* This function is similar to indegree_at(), but it will return NULL
- * until a call to indegree_at() was made for the commit.
+ * if the location to store the data associated with the given commit
+ * has not been allocated yet.
+ * Note that the location to store the data might have already been
+ * allocated even if no indegree_at() call has been made for that commit
+ * yet; in this case this function returns a pointer to a
+ * zero-initialized location.
*
* - void init_indegree(struct indegree *);
* void init_indegree_with_stride(struct indegree *, int);
--
2.26.0.rc0.366.gb2d359bb99
next reply other threads:[~2020-03-10 15:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-10 15:30 SZEDER Gábor [this message]
2020-03-10 17:54 ` [PATCH] commit-slab: clarify slabname##_peek()'s return value Jeff King
2020-03-10 18:07 ` Jeff King
2020-03-11 16:07 ` Jeff King
2020-03-10 18:19 ` Junio C Hamano
2020-03-10 18:26 ` Junio C Hamano
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