commit-slab: clarify slabname##_peek()'s return value

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> Signed-off-by: Junio C Hamano <gitster@pobox.com>

SZEDER Gábor committed Mar 10, 2020 at 16:30 UTC 7422b2a0a11749942db71d59e3e1221ccba5e7ce

1 file changed +6 -1

commit-slab.h

+6 -1

@@ -24,7 +24,12 @@

24 * - int *indegree_peek(struct indegree *, struct commit *);

25 *

26 * This function is similar to indegree_at(), but it will return NULL

27 - * until a call to indegree_at() was made for the commit.

27 + * if the location to store the data associated with the given commit

28 + * has not been allocated yet.

29 + * Note that the location to store the data might have already been

30 + * allocated even if no indegree_at() call has been made for that commit

31 + * yet; in this case this function returns a pointer to a

32 + * zero-initialized location.

33 *

34 * - void init_indegree(struct indegree *);

35 * void init_indegree_with_stride(struct indegree *, int);