Bluetooth: host: refactor bt_gatt_is_subscribed

Refactors `bt_gatt_is_subscribed` by changing a CHECKIF to an if
statement to avoid undefined behavior if CHECKIFs are "disabled".
Uses sizeof(a uint8_t) instead of 1 to avoid magic numbers.
Initializes `properties` to 0 to avoid undefined behavior.

Signed-off-by: Håvard Reierstad <[email protected]>

Author: HaavardRei

subsys/bluetooth/host/gatt.c

@@ -3484,19 +3484,19 @@ bool bt_gatt_is_subscribed(struct bt_conn *conn,
 
 	/* Check if attribute is a characteristic declaration */
 	if (!bt_uuid_cmp(attr->uuid, BT_UUID_GATT_CHRC)) {
-		uint8_t properties;
+		uint8_t properties = 0;
 		ssize_t len;
 
-		CHECKIF(!attr->read) {
+		if (!attr->read) {
 			LOG_ERR("Read method not set");
 			return false;
 		}
 		/* The charactestic properties is the first byte of the attribute value */
-		len = attr->read(NULL, attr, &properties, 1, 0);
+		len = attr->read(NULL, attr, &properties, sizeof(properties), 0);
 		if (len < 0) {
 			LOG_ERR("Failed to read attribute (err %zd)", len);
 			return false;
-		} else if (len != 1) {
+		} else if (len != sizeof(properties)) {
 			LOG_ERR("Invalid read length: %zd", len);
 			return false;
 		}