char * f_name = "read_map_cells()";
free(world.map.cells);
world.map.cells = try_malloc(world.map.size.y * world.map.size.x, f_name);
char * f_name = "read_map_cells()";
free(world.map.cells);
world.map.cells = try_malloc(world.map.size.y * world.map.size.x, f_name);