encoding/gob: oom on doubly linked list about go

[Septrum101]

Below is the demo code. It cannot work.

package main

import (
	"encoding/gob"
	"fmt"
	"log"
	"os"
)

type Node struct {
	Val  int
	Prev *Node
	Next *Node
}

func main() {
	// Creating doubly linked list
	head := &Node{Val: 1}
	head.Next = &Node{Val: 2, Prev: head}
	head.Next.Next = &Node{Val: 3, Prev: head.Next}

	// Create and open file to store data
	file, err := os.Create("store.gob")
	if err != nil {
		log.Fatal("create file error:", err)
	}
	defer file.Close()

	// Create encoder and encode structure to file
	enc := gob.NewEncoder(file)
	if err = enc.Encode(head); err != nil {
		log.Fatal("encode error:", err)
	}

	// Close the file
	file.Close()

	// Open file to be ready for decoding
	file, err = os.Open("store.gob")
	if err != nil {
		log.Fatal("open file error:", err)
	}
	defer file.Close()

	// Create decoder and decode structure from file
	var decodedHead Node
	dec := gob.NewDecoder(file)
	if err = dec.Decode(&decodedHead); err != nil {
		log.Fatal("decode error:", err)
	}

	// Printing decoded data
	for node := &decodedHead; node != nil; node = node.Next {
		fmt.Println(node.Val)
	}
}

[Septrum101]

The singly linked list works perfect.

package main

import (
	"encoding/gob"
	"fmt"
	"log"
	"os"
)

type Node struct {
	Val  int
	Next *Node
}

func main() {
	// Creating singly linked list
	head := &Node{Val: 1}
	head.Next = &Node{Val: 2}
	head.Next.Next = &Node{Val: 3}

	// Create and open file to store data
	file, err := os.Create("store.gob")
	if err != nil {
		log.Fatal("creation file error:", err)
	}
	defer file.Close()

	// Create encoder and encode structure to file
	enc := gob.NewEncoder(file)
	if err = enc.Encode(head); err != nil {
		log.Fatal("encoding error:", err)
	}

	// Close the file
	file.Close()

	// Open file for decoding
	file, err = os.Open("store.gob")
	if err != nil {
		log.Fatal("opening file error:", err)
	}
	defer file.Close()

	// Create decoder and decode structure from file
	var decodedHead Node
	dec := gob.NewDecoder(file)
	if err = dec.Decode(&decodedHead); err != nil {
		log.Fatal("decoding error:", err)
	}

	// Printing the decoded list
	for node := &decodedHead; node != nil; node = node.Next {
		fmt.Println(node.Val)
	}
}

[seankhliao]

from the package docs

recursive values (data with cycles) are problematic.

[Septrum101]

thanks for your reply.