Uninitialized scalar field

The field will contain an arbitrary value left over from earlier computations. A scalar field is not initialized by the constructor
/src/mongo/db/repl_index_build_state.h:281: UNINIT_CTOR 114677 Class member declaration for "opId".
/src/mongo/db/repl_index_build_state.h:252: UNINIT_CTOR 114677 Non-static class member "opId" is not initialized in this constructor nor in any functions that it calls.