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>

diff --git a/alloc.c b/alloc.c
index e7aa81b7aa48c14f2a98894eb6e8c2e28998945e..1c64c4dd1629c63a8bb2fff6e580ee0c648a0730 100644 (file)
--- a/alloc.c
+++ b/alloc.c
@@ -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;
        c->generation = GENERATION_NUMBER_INFINITY;
+}
+
+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;
 }
 

diff --git a/alloc.h b/alloc.h
index ba356ed8478d13f05f49efd5bacccaac3e69dfd7..ed1071c11ea3a6d0f7d55da46df4acf524a32565 100644 (file)
--- a/alloc.h
+++ b/alloc.h
@@ -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);

diff --git a/object.c b/object.c
index 51c45945156c421ada403139faefdf145918f4f7..675cb8902b0c7289397f3a51e71b1ca2ce3dd2b6 100644 (file)
--- a/object.c
+++ b/object.c
@@ -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);
+               else
+                       obj->type = type;
                return obj;
        }
        else {