object_as_type: initialize commit-graph-related fields of 'struct commit'

When the commit graph and generation numbers were introduced in
commits 177722b344 (commit: integrate commit graph with commit
parsing, 2018-04-10) and 83073cc994 (commit: add generation number to
struct commit, 2018-04-25), they tried to make sure that the
corresponding 'graph_pos' and 'generation' fields of 'struct commit'
are initialized conservatively, as if the commit were not included in
the commit-graph file.

Alas, initializing those fields only in alloc_commit_node() missed the
case when an object that happens to be a commit is first looked up via
lookup_unknown_object(), and is then later converted to a 'struct
commit' via the object_as_type() helper function (either calling it
directly, or as part of a subsequent lookup_commit() call).
Consequently, both of those fields incorrectly remain set to zero,
which means e.g. that the commit is present in and is the first entry
of the commit-graph file.  This will result in wrong timestamp, parent
and root tree hashes, if such a 'struct commit' instance is later
filled from the commit-graph.

Extract the initialization of 'struct commit's fields from
alloc_commit_node() into a helper function, and call it from
object_as_type() as well, to make sure that it properly initializes
the two commit-graph-related fields, too.  With this helper function
it is hopefully less likely that any new fields added to 'struct
commit' in the future would remain uninitialized.

With this change alloc_commit_index() won't have any remaining callers
outside of 'alloc.c', so mark it as static.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
SZEDER Gábor 4 years ago committed by Junio C Hamano
parent 98cdfbb84a
commit 4468d4435c
  1. 11
  2. 2
  3. 5

@ -99,18 +99,23 @@ void *alloc_object_node(struct repository *r)
return obj;
unsigned int alloc_commit_index(struct repository *r)
static unsigned int alloc_commit_index(struct repository *r)
return r->parsed_objects->commit_count++;
void *alloc_commit_node(struct repository *r)
void init_commit_node(struct repository *r, struct commit *c)
struct commit *c = alloc_node(r->parsed_objects->commit_state, sizeof(struct commit));
c->object.type = OBJ_COMMIT;
c->index = alloc_commit_index(r);
c->graph_pos = COMMIT_NOT_FROM_GRAPH;
void *alloc_commit_node(struct repository *r)
struct commit *c = alloc_node(r->parsed_objects->commit_state, sizeof(struct commit));
init_commit_node(r, c);
return c;

@ -9,11 +9,11 @@ struct repository;
void *alloc_blob_node(struct repository *r);
void *alloc_tree_node(struct repository *r);
void init_commit_node(struct repository *r, struct commit *c);
void *alloc_commit_node(struct repository *r);
void *alloc_tag_node(struct repository *r);
void *alloc_object_node(struct repository *r);
void alloc_report(struct repository *r);
unsigned int alloc_commit_index(struct repository *r);
struct alloc_state *allocate_alloc_state(void);
void clear_alloc_state(struct alloc_state *s);

@ -164,8 +164,9 @@ void *object_as_type(struct repository *r, struct object *obj, enum object_type
return obj;
else if (obj->type == OBJ_NONE) {
if (type == OBJ_COMMIT)
((struct commit *)obj)->index = alloc_commit_index(r);
obj->type = type;
init_commit_node(r, (struct commit *) obj);
obj->type = type;
return obj;
else {