expr_print_help
expr_print_help, &stream, E_NONE);
expr_print(sym->rev_dep.expr, expr_print_help, &stream, E_NONE);
expr_print(prop->expr, expr_print_help,
expr_print(prop->visible.expr, expr_print_help,
static void expr_print_help(void *data, struct symbol *sym, const char *str);