nil指针判断

secguide/Go安全指南.md at main · Tencent/secguide · GitHub https://github.com/Tencent/secguide/blob/main/Go%E5%AE%89%E5%85%A8%E6%8C%87%E5%8D%97.md#112%E5%BF%85%E9%A1%BBnil%E6%8C%87%E9%92%88%E5%88%A4%E6%96%AD

1.1.2【必须】nil指针判断

• 进行指针操作时，必须判断该指针是否为nil，防止程序panic，尤其在进行结构体Unmarshal时

type Packet struct {
	PackeyType    uint8
	PackeyVersion uint8
	Data          *Data
}

type Data struct {
	Stat uint8
	Len  uint8
	Buf  [8]byte
}

func (p *Packet) UnmarshalBinary(b []byte) error {
	if len(b) < 2 {
		return io.EOF
	}

	p.PackeyType = b[0]
	p.PackeyVersion = b[1]

	// 若长度等于2，那么不会new Data
	if len(b) > 2 {
		p.Data = new(Data)
	}
	return nil
}

// bad: 未判断指针是否为nil
func main() {
	packet := new(Packet)
	data := make([]byte, 2)
	if err := packet.UnmarshalBinary(data); err != nil {
		fmt.Println("Failed to unmarshal packet")
		return
	}

	fmt.Printf("Stat: %v\n", packet.Data.Stat)
}

// good: 判断Data指针是否为nil
func main() {
	packet := new(Packet)
	data := make([]byte, 2)

	if err := packet.UnmarshalBinary(data); err != nil {
		fmt.Println("Failed to unmarshal packet")
		return
	}

	if packet.Data == nil {
		return
	}

	fmt.Printf("Stat: %v\n", packet.Data.Stat)
}