The tetrahedral voids formed by ccp arrangement of ${\mathrm{Cl}}^{-}$ ions ill rock salt structure are:

The tetrahedral holes created by the ${\mathrm{Cl}}^{-}$-ccp ion's arrangement in the rock salt structure are empty.
${\mathrm{Cl}}^{+}$ ions form a face-centered cube in the rock salt structure, whereas ${\mathrm{Na}}^{+}$ions are found in octahedral gaps.
NaCl is present in 4 formula units per unit cell.