Infinite Loop Caused by Self-Referencing Struct in Map

[omarsy]

Infinite Loop Caused by Self-Referencing Struct in Map

Description

During panic situations in our application realm, we've encountered an issue related to a self-referencing struct within a map. When attempting to print the state of the machine during a panic using machine.String(), the application enters an infinite loop.

Steps to reproduce

1. Go to https://play.gno.land/
2. Paste this code and run

package main

type Test struct {
    next map[string]*Test
}

func getNewTest() *Test {
    curr := Test{
        next: map[string]*Test{
            "test": {},
        },
    }

    // Assigning a reference to the struct itself within the map
    curr.next["test"] = &curr

    return &curr
}

func main() {
    test := getNewTest()
    panic("here")
}

Logs

runtime: goroutine stack exceeds 1000000000-byte limit
runtime: sp=0x1402c708380 stack=[0x1402c708000, 0x1404c708000]
fatal error: stack overflow

runtime stack:
runtime.throw({0x10300471d?, 0x51001?})
        /usr/local/go/src/runtime/panic.go:1023 +0x40 fp=0x16d56ed70 sp=0x16d56ed40 pc=0x1028cc2d0
runtime.newstack()
        /usr/local/go/src/runtime/stack.go:1103 +0x460 fp=0x16d56ef20 sp=0x16d56ed70 pc=0x1028e9730
runtime.morestack()
        /usr/local/go/src/runtime/asm_arm64.s:341 +0x70 fp=0x16d56ef20 sp=0x16d56ef20 pc=0x102906220

goroutine 1 gp=0x140000021c0 m=0 mp=0x103951d40 [running]:
fmt.(*fmt).padString(0x14014feda40?, {0x140000362e8, 0x14})
        /usr/local/go/src/fmt/format.go:108 +0x29c fp=0x1402c708380 sp=0x1402c708380 pc=0x102988f3c
fmt.(*fmt).fmtS(0x0?, {0x140000362e8?, 0xd0?})
        /usr/local/go/src/fmt/format.go:359 +0x40 fp=0x1402c7083c0 sp=0x1402c708380 pc=0x102989a20
fmt.(*pp).fmtString(0x1402c708448?, {0x140000362e8?, 0x0?}, 0x0?)
        /usr/local/go/src/fmt/print.go:497 +0xe4 fp=0x1402c708410 sp=0x1402c7083c0 pc=0x10298c6f4
fmt.(*pp).printArg(0x14014feda00, {0x103268da0, 0x14014ff5910}, 0x73)
        /usr/local/go/src/fmt/print.go:741 +0x2fc fp=0x1402c7084b0 sp=0x1402c708410 pc=0x10298e1cc
fmt.(*pp).doPrintf(0x14014feda00, {0x102ffbb98, 0x5}, {0x1402c708648, 0x2, 0x2})
        /usr/local/go/src/fmt/print.go:1075 +0x2d8 fp=0x1402c7085b0 sp=0x1402c7084b0 pc=0x102990af8
fmt.Sprintf({0x102ffbb98, 0x5}, {0x1402c708648, 0x2, 0x2})
        /usr/local/go/src/fmt/print.go:239 +0x4c fp=0x1402c708610 sp=0x1402c7085b0 pc=0x10298b00c
github.com/gnolang/gno/gnovm/pkg/gnolang.(*DeclaredType).String(0x1400038ecc0)
        /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/types.go:1442 +0x80 fp=0x1402c708670 sp=0x1402c708610 pc=0x102f50ab0
fmt.(*pp).handleMethods(0x14014fed930, 0x0?)
        /usr/local/go/src/fmt/print.go:673 +0x29c fp=0x1402c708840 sp=0x1402c708670 pc=0x10298da1c
fmt.(*pp).printArg(0x14014fed930, {0x10336fd60, 0x1400038ecc0}, 0x76)
        /usr/local/go/src/fmt/print.go:756 +0x3e0 fp=0x1402c7088e0 sp=0x1402c708840 pc=0x10298e2b0
fmt.(*pp).doPrintf(0x14014fed930, {0x102ffac14, 0x3}, {0x1402c708a78, 0x1, 0x1})
        /usr/local/go/src/fmt/print.go:1075 +0x2d8 fp=0x1402c7089e0 sp=0x1402c7088e0 pc=0x102990af8
fmt.Sprintf({0x102ffac14, 0x3}, {0x1402c708a78, 0x1, 0x1})
        /usr/local/go/src/fmt/print.go:239 +0x4c fp=0x1402c708a40 sp=0x1402c7089e0 pc=0x10298b00c
github.com/gnolang/gno/gnovm/pkg/gnolang.(*PointerType).String(0x1402c708ad8?)
        /Users/ghost/Documents/projects/teritori/gno/gnovm/pkg/gnolang/types.go:603 +0x5c fp=0x14

Proposed solution

I will open a PR with a solution