Panic when inspecting double linked datastructures

[DavidGamba]

If I inspect the double linked datastructure described below:

type CLITree struct {
	Type     argType
	Name     string
	Children []*CLITree
	Parent   *CLITree
}

For a trivial datastructure I get the following error:

$ go test
runtime: goroutine stack exceeds 1000000000-byte limit
runtime: sp=0xc020160358 stack=[0xc020160000, 0xc040160000]
fatal error: stack overflow

runtime stack:
runtime.throw(0x595c2b, 0xe)
        /home/david/opt/go/src/runtime/panic.go:1117 +0x72
runtime.newstack()
        /home/david/opt/go/src/runtime/stack.go:1069 +0x7ed
runtime.morestack()
        /home/david/opt/go/src/runtime/asm_amd64.s:458 +0x8f

goroutine 18 [running]:
fmt.(*pp).printArg(0xc0000a41a0, 0x5632e0, 0x68b5a0, 0x64)
        /home/david/opt/go/src/fmt/print.go:634 +0x9e5 fp=0xc020160368 sp=0xc020160360 pc=0x4ddb85
fmt.(*pp).doPrintf(0xc0000a41a0, 0x594bc5, 0x9, 0xc020160660, 0x1, 0x1)
        /home/david/opt/go/src/fmt/print.go:1026 +0x168 fp=0xc020160458 sp=0xc020160368 pc=0x4e0aa8
fmt.Sprintf(0x594bc5, 0x9, 0xc020160660, 0x1, 0x1, 0x0, 0x0)
        /home/david/opt/go/src/fmt/print.go:219 +0x66 fp=0xc0201604b0 sp=0xc020160458 pc=0x4d9de6
github.com/go-test/deep.(*cmp).equals(0xc04015fe50, 0x55ffa0, 0xc0000b0758, 0x197, 0x55ffa0, 0xc0000b0658, 0x197, 0xcccc9)
        /home/david/go/pkg/mod/github.com/go-test/deep@v1.0.7/deep.go:341 +0x183c fp=0xc020160730 sp=0xc0201604b0 pc=0x54c13c
github.com/go-test/deep.(*cmp).equals(0xc04015fe50, 0x57fb00, 0xc0000b0740, 0x199, 0x57fb00, 0xc0000b0640, 0x199, 0xcccc8)
        /home/david/go/pkg/mod/github.com/go-test/deep@v1.0.7/deep.go:223 +0x242d fp=0xc0201609b0 sp=0xc020160730 pc=0x54cd2d
github.com/go-test/deep.(*cmp).equals(0xc04015fe50, 0x57fb00, 0xc0000b0740, 0x199, 0x55c700, 0xc0000b06b0, 0x196, 0xcccc7)
        /home/david/go/pkg/mod/github.com/go-test/deep@v1.0.7/deep.go:162 +0x31d9 fp=0xc020160c30 sp=0xc0201609b0 pc=0x54dad9
github.com/go-test/deep.(*cmp).equals(0xc04015fe50, 0x57fb00, 0xc0000b0780, 0x199, 0x57fb00, 0xc0000b0680, 0x199, 0xcccc6)
        /home/david/go/pkg/mod/github.com/go-test/deep@v1.0.7/deep.go:223 +0x242d fp=0xc020160eb0 sp=0xc020160c30 pc=0x54cd2d
github.com/go-test/deep.(*cmp).equals(0xc04015fe50, 0x57fb00, 0xc0000b0780, 0x199, 0x55c700, 0xc00009e590, 0x196, 0xcccc5)
        /home/david/go/pkg/mod/github.com/go-test/deep@v1.0.7/deep.go:162 +0x31d9 fp=0xc020161130 sp=0xc020160eb0 pc=0x54dad9
github.com/go-test/deep.(*cmp).equals(0xc04015fe50, 0x55ffa0, 0xc0000b0758, 0x197, 0x55ffa0, 0xc0000b0658, 0x197, 0xcccc4)
        /home/david/go/pkg/mod/github.com/go-test/deep@v1.0.7/deep.go:343 +0x1b78 fp=0xc0201613b0 sp=0xc020161130 pc=0x54c478

...

...additional frames elided...
created by testing.(*T).Run
        /home/david/opt/go/src/testing/testing.go:1238 +0x2b3

goroutine 1 [chan receive]:
testing.(*T).Run(0xc000082600, 0x5957ed, 0xd, 0x59e868, 0x489fe6)
        /home/david/opt/go/src/testing/testing.go:1239 +0x2da
testing.runTests.func1(0xc000082480)
        /home/david/opt/go/src/testing/testing.go:1511 +0x78
testing.tRunner(0xc000082480, 0xc000093de0)
        /home/david/opt/go/src/testing/testing.go:1193 +0xef
testing.runTests(0xc0000bc048, 0x693580, 0x1, 0x1, 0xc01514bef2b74a44, 0x8bb2cc5311, 0x69bc40, 0x595925)
        /home/david/opt/go/src/testing/testing.go:1509 +0x2fe
testing.(*M).Run(0xc0000f0000, 0x0)
        /home/david/opt/go/src/testing/testing.go:1417 +0x1eb
main.main()
        _testmain.go:43 +0x138
exit status 2

NOTE: go-spew handles them properly by displaying already shown:

(*getoptions.CLITree)({
          Type: (getoptions.argType) 0,
          Name: (string) (len=46) "/tmp/go-build309650026/b001/go-getoptions.test",
          Children: ([]*getoptions.CLITree) (len=2) {
            (*getoptions.CLITree)({
              Type: (getoptions.argType) 2,
              Name: (string) (len=4) "opt1",
              Children: ([]*getoptions.CLITree) {
              },
              Parent: (*getoptions.CLITree)(<already shown>)
            }),
            (*getoptions.CLITree)({
              Type: (getoptions.argType) 3,
              Name: (string) (len=3) "cmd",
              Children: ([]*getoptions.CLITree) (len=1) {
                (*getoptions.CLITree)({
                  Type: (getoptions.argType) 2,
                  Name: (string) (len=4) "opt2",
                  Children: ([]*getoptions.CLITree) {
                  },
                  Parent: (*getoptions.CLITree)(<already shown>)
                })
              },
              Parent: (*getoptions.CLITree)(<already shown>)
            })
          },
          Parent: (*getoptions.CLITree)(<nil>)
        })

[olavfosse]

I got the same panic when comparing to *html.Nodes, which also are doubly linked lists + links to parent and children.