all_vars = xnmalloc (n_all_vars, sizeof (*all_vars));
fill_all_vars (all_vars, cmd);
vars = xnmalloc (n_variables, sizeof (*vars));
all_vars = xnmalloc (n_all_vars, sizeof (*all_vars));
fill_all_vars (all_vars, cmd);
vars = xnmalloc (n_variables, sizeof (*vars));