> Jonathan Tan <jonathantanmy@xxxxxxxxxx> writes:
>
> > object = get_reference(revs, arg, &oid, flags ^ local_flags);
> > if (!object)
> > - return revs->ignore_missing ? 0 : -1;
> > + /*
> > + * Either this object is missing and ignore_missing is true, or
> > + * this object is a (missing) promisor object and
> > + * exclude_promisor_objects is true.
>
> I had to guess and dig where these assertions are coming from; we
> should not force future readers of the code to.
>
> At least this comment must say why these assertions hold. Say
> something like "get_reference() yields NULL on only such and such
> cases" before concluding with "and in any of these cases, we can
> safely ignore it because ...".
OK, will do.
> I think the two cases the comment covers are safe for this caller to
> silently return 0. Another case get_reference() yields NULL is when
> oid_object_info() says it is a commit but it turns out that the
> object is found by repo_parse_commit() to be a non-commit, isn't it?
> I am not sure if it is safe for this caller to just return 0. There
> may be some other "unusual-but-not-fatal" cases where get_reference()
> does not hit a die() but returns NULL.
I don't think there is any other case where get_reference() yields NULL,
at least where I based my patch (99c33bed56 ("Git 2.25-rc0",
2019-12-25)). Quoting the entire get_reference():
> static struct object *get_reference(struct rev_info *revs, const char *name,
> const struct object_id *oid,
> unsigned int flags)
> {
> struct object *object;
>
> /*
> * If the repository has commit graphs, repo_parse_commit() avoids
> * reading the object buffer, so use it whenever possible.
> */
> if (oid_object_info(revs->repo, oid, NULL) == OBJ_COMMIT) {
> struct commit *c = lookup_commit(revs->repo, oid);
> if (!repo_parse_commit(revs->repo, c))
> object = (struct object *) c;
> else
> object = NULL;
> } else {
> object = parse_object(revs->repo, oid);
> }
No return statements at all prior to this line.
> if (!object) {
> if (revs->ignore_missing)
> return object;
Return NULL (the value of object).
> if (revs->exclude_promisor_objects && is_promisor_object(oid))
> return NULL;
Return NULL.
> die("bad object %s", name);
Die (so this function invocation never returns). In conclusion, if
object is NULL at this point in time, get_reference() either returns
NULL or dies.
> }
Since get_reference() did not return NULL or die, object is non-NULL
here.
> object->flags |= flags;
> return object;
Nothing has overridden object since, so we're returning non-NULL here.
> }
So I think get_reference() only returns NULL in those two safe cases.
(Or did I miss something?)
