Freeciv

int api_methods_tile_latitude(lua_State *L, Tile *ptile)
{
+ LUASCRIPT_CHECK_STATE(L, -1);
+ LUASCRIPT_CHECK_SELF(L, ptile, -1);

return map_signed_latitude(ptile);
+}

Since it normally returns signed latitude -> negative values are valid, it makes no sense to return specifically -1 on error.

Had to think about this one, it has to return something because the function isn't void. Best I can come up with is MAP_MAX_LATITUDE + 1.