Each petitioner signing such petition shall write, or cause to be written, opposite to his name on said petition, the name of the city and ward in which he then resides, if he resides in a city; or, if he does not reside in a city, then the name of the precinct in which he resides at the time of signing such petition; and no person shall sign such petition unless he shall be, at the time, a legal voter at general elections.