int handle_revision_arg(const char *arg_, struct rev_info *revs, int flags, unsigned revarg_opt)
{
	struct object_context oc;
	char *dotdot;
	struct object *object;
	unsigned char sha1[20];
	int local_flags;
	const char *arg = arg_;
	int cant_be_filename = revarg_opt & REVARG_CANNOT_BE_FILENAME;
	unsigned get_sha1_flags = 0;

	flags = flags & UNINTERESTING ? flags | BOTTOM : flags & ~BOTTOM;

	dotdot = strstr(arg, "..");
	if (dotdot) {
		unsigned char from_sha1[20];
		const char *next = dotdot + 2;
		const char *this = arg;
		int symmetric = *next == '.';
		unsigned int flags_exclude = flags ^ (UNINTERESTING | BOTTOM);
		static const char head_by_default[] = "HEAD";
		unsigned int a_flags;

		*dotdot = 0;
		next += symmetric;

		if (!*next)
			next = head_by_default;
		if (dotdot == arg)
			this = head_by_default;
		if (this == head_by_default && next == head_by_default &&
		    !symmetric) {
			/*
			 * Just ".."?  That is not a range but the
			 * pathspec for the parent directory.
			 */
			if (!cant_be_filename) {
				*dotdot = '.';
				return -1;
			}
		}
		if (!get_sha1_committish(this, from_sha1) &&
		    !get_sha1_committish(next, sha1)) {
			struct object *a_obj, *b_obj;

			if (!cant_be_filename) {
				*dotdot = '.';
				verify_non_filename(revs->prefix, arg);
			}

			a_obj = parse_object(from_sha1);
			b_obj = parse_object(sha1);
			if (!a_obj || !b_obj) {
			missing:
				if (revs->ignore_missing)
					return 0;
				die(symmetric
				    ? "Invalid symmetric difference expression %s"
				    : "Invalid revision range %s", arg);
			}

			if (!symmetric) {
				/* just A..B */
				a_flags = flags_exclude;
			} else {
				/* A...B -- find merge bases between the two */
				struct commit *a, *b;
				struct commit_list *exclude;

				a = (a_obj->type == OBJ_COMMIT
				     ? (struct commit *)a_obj
				     : lookup_commit_reference(a_obj->sha1));
				b = (b_obj->type == OBJ_COMMIT
				     ? (struct commit *)b_obj
				     : lookup_commit_reference(b_obj->sha1));
				if (!a || !b)
					goto missing;
				exclude = get_merge_bases(a, b);
				add_rev_cmdline_list(revs, exclude,
						     REV_CMD_MERGE_BASE,
						     flags_exclude);
				add_pending_commit_list(revs, exclude,
							flags_exclude);
				free_commit_list(exclude);

				a_flags = flags | SYMMETRIC_LEFT;
			}

			a_obj->flags |= a_flags;
			b_obj->flags |= flags;
			add_rev_cmdline(revs, a_obj, this,
					REV_CMD_LEFT, a_flags);
			add_rev_cmdline(revs, b_obj, next,
					REV_CMD_RIGHT, flags);
			add_pending_object(revs, a_obj, this);
			add_pending_object(revs, b_obj, next);
			return 0;
		}
		*dotdot = '.';
	}
	dotdot = strstr(arg, "^@");
	if (dotdot && !dotdot[2]) {
		*dotdot = 0;
		if (add_parents_only(revs, arg, flags))
			return 0;
		*dotdot = '^';
	}
	dotdot = strstr(arg, "^!");
	if (dotdot && !dotdot[2]) {
		*dotdot = 0;
		if (!add_parents_only(revs, arg, flags ^ (UNINTERESTING | BOTTOM)))
			*dotdot = '^';
	}

	local_flags = 0;
	if (*arg == '^') {
		local_flags = UNINTERESTING | BOTTOM;
		arg++;
	}

	if (revarg_opt & REVARG_COMMITTISH)
		get_sha1_flags = GET_SHA1_COMMITTISH;

	if (get_sha1_with_context(arg, get_sha1_flags, sha1, &oc))
		return revs->ignore_missing ? 0 : -1;
	if (!cant_be_filename)
		verify_non_filename(revs->prefix, arg);
	object = get_reference(revs, arg, sha1, flags ^ local_flags);
	add_rev_cmdline(revs, object, arg_, REV_CMD_REV, flags ^ local_flags);
	add_pending_object_with_mode(revs, object, arg, oc.mode);
	return 0;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.