See https://mci.10gen.com/task_log_raw/mongodb_mongo_master_sanitize_ubuntu1404_debug_asan_e0f8376cf7e3496af394df5ce6132f9b0cfb3af3_14_11_07_23_31_08_jsCore_small_oplog_ubuntu1404_debug_asan/1?type=T
and
http://buildlogs.mongodb.org/MCI_asan_ubuntu1404-debug-asan/builds/626/test/jsCore_small_oplog_1/write_result.js