ast_for_for_stmt(struct compiling *c, const node *n, int is_async)
{
    asdl_seq *_target, *seq = NULL, *suite_seq;
    expr_ty expression;
    expr_ty target, first;
    const node *node_target;
    int has_type_comment;
    string type_comment;

    if (is_async && c->c_feature_version < 5) {
        ast_error(c, n,
                "Async for loops are only supported in Python 3.5 and greater");
        return NULL;
    }

    /* for_stmt: 'for' exprlist 'in' testlist ':' [TYPE_COMMENT] suite ['else' ':' suite] */
    REQ(n, for_stmt);

    has_type_comment = TYPE(CHILD(n, 5)) == TYPE_COMMENT;

    if (NCH(n) == 9 + has_type_comment) {
        seq = ast_for_suite(c, CHILD(n, 8 + has_type_comment));
        if (!seq)
            return NULL;
    }

    node_target = CHILD(n, 1);
    _target = ast_for_exprlist(c, node_target, Store);
    if (!_target)
        return NULL;
    /* Check the # of children rather than the length of _target, since
       for x, in ... has 1 element in _target, but still requires a Tuple. */
    first = (expr_ty)asdl_seq_GET(_target, 0);
    if (NCH(node_target) == 1)
        target = first;
    else
        target = Tuple(_target, Store, first->lineno, first->col_offset, c->c_arena);

    expression = ast_for_testlist(c, CHILD(n, 3));
    if (!expression)
        return NULL;
    suite_seq = ast_for_suite(c, CHILD(n, 5 + has_type_comment));
    if (!suite_seq)
        return NULL;

    if (has_type_comment)
        type_comment = NEW_TYPE_COMMENT(CHILD(n, 5));
    else
        type_comment = NULL;

    if (is_async)
        return AsyncFor(target, expression, suite_seq, seq,
                        type_comment, LINENO(n), n->n_col_offset,
                        c->c_arena);
    else
        return For(target, expression, suite_seq, seq,
                   type_comment, LINENO(n), n->n_col_offset,
                   c->c_arena);
}
The software reads data past the end, or before the beginning, of the intended buffer.