Null tuple cause panic

[supar]

Please answer these questions before submitting your issue. Thanks!

What version of Cassandra are you using?

cqlsh 5.0.1 | Cassandra 3.11.4 | CQL spec 3.4.4 | Native protocol v4

What version of Gocql are you using?

f6df828

What did you do?

CREATE TABLE products (
            id timeuuid PRIMARY KEY,
            name text,
            category frozen<tuple<timeuuid, varchar>>
 );

INSERT INTO products(id, name) VALUES (cb403e20-ce63-11e9-b49a-d99f577eb025, 'Without category');

SELECT * FROM products;

 id                                   | name       | category
--------------------------------------+------------+----------
 cb403e20-ce63-11e9-b49a-d99f577eb025 | Without category |     null

What did you expect to see?

no panic

What did you see instead?

http: panic serving 172.17.0.1:57798: runtime error: index out of range
goroutine 61 [running]:
net/http.(*conn).serve.func1(0xc000348140)
	/usr/local/go/src/net/http/server.go:1769 +0x139
panic(0xa2b360, 0x11f5160)
	/usr/local/go/src/runtime/panic.go:522 +0x1b5
github.com/gocql/gocql.readInt(...)
	/go/src/github.com/gocql/gocql/frame.go:322
github.com/gocql/gocql.readBytes(...)
	/go/src/github.com/gocql/gocql/marshal.go:1788
github.com/gocql/gocql.unmarshalTuple(0xbcfd20, 0xc000372540, 0x0, 0x0, 0x0, 0x9e5280, 0xc000380420, 0x0, 0x0)
	/go/src/github.com/gocql/gocql/marshal.go:1810 +0x11a7
github.com/gocql/gocql.Unmarshal(0xbcfd20, 0xc000372540, 0x0, 0x0, 0x0, 0x9e5280, 0xc000380420, 0xc0000c6d68, 0x69a3c5)
	/go/src/github.com/gocql/gocql/marshal.go:162 +0xdaa
github.com/gocql/gocql.scanColumn(0x0, 0x0, 0x0, 0xc000024ff0, 0x3, 0xc000024ff8, 0x8, 0xc000025028, 0x8, 0xbcfd20, ...)
	/go/src/github.com/gocql/gocql/session.go:1292 +0x1b3
github.com/gocql/gocql.(*Iter).Scan(0xc0002dcab0, 0xc00031e1c0, 0x7, 0x7, 0xc00031e1c0)
	/go/src/github.com/gocql/gocql/session.go:1397 +0x2e5

---

It happens while readInt function retrieves size from empty []byte

frame.go

func readInt(p []byte) int32 {
    return int32(p[0])<<24 | int32(p[1])<<16 | int32(p[2])<<8 | int32(p[3])
}

marshal.go

func readBytes(p []byte) ([]byte, []byte) {
    // TODO: really should use a framer
    size := readInt(p)
    p = p[4:]
    if size < 0 {
        return nil, p
    }
    return p[:size], p[size:]
}

There is comment on

// currently only support unmarshal into a list of values, this makes it possible
// to support tuples without changing the query API. In the future this can be extend
// to allow unmarshalling into custom tuple types.
func unmarshalTuple(info TypeInfo, data []byte, value interface{}) error {

Maybe this means that field should be category list<frozen<tuple<timeuuid, varchar>>>, but it's not panic case