CompareObjects hangs on valid input

[pteichman]

I found a pair of valid JSON inputs that cause Differ.CompareObjects to hang indefinitely.

[Edit: changing the link to a branch rather than specific commit]

I've added sanitized versions of those files and a hanging unit test over here: https://github.com/pteichman/gojsondiff/tree/infinite-hang

As an API request, would it be useful to be able to disable the substring diffing? For my use case it's enough to know that the values fail string equality checks. Or alternatively, should LCS calculation be part of the display logic rather than in the differ itself?

[pteichman]

And here's a goroutine dump while it's hanging. At least this time it was in reflect.DeepEqual, though that function itself runs fine on my two inputs. Maybe an infinite loop in the string similarity code?

SIGQUIT: quit
PC=0x5f50b m=0

goroutine 0 [idle]:
runtime.mach_semaphore_wait(0x7fff00000d03, 0x1, 0x55310, 0x7fff5fbff404, 0xffffffffffffffff, 0x5139e0, 0x7fff5fbff450, 0x55343, 0xffffffffffffffff, 0x513120, ...)
/usr/local/go/src/runtime/sys_darwin_amd64.s:418 +0xb
runtime.semasleep1(0xffffffffffffffff, 0x513120)
/usr/local/go/src/runtime/os_darwin.go:435 +0x4b
runtime.semasleep.func1()
/usr/local/go/src/runtime/os_darwin.go:451 +0x33
runtime.systemstack(0x7fff5fbff478)
/usr/local/go/src/runtime/asm_amd64.s:314 +0xab
runtime.semasleep(0xffffffffffffffff, 0x0)
/usr/local/go/src/runtime/os_darwin.go:452 +0x44
runtime.notesleep(0x514330)
/usr/local/go/src/runtime/lock_sema.go:166 +0x9f
runtime.stopm()
/usr/local/go/src/runtime/proc.go:1594 +0xad
runtime.findrunnable(0xc42001c000, 0x0)
/usr/local/go/src/runtime/proc.go:2021 +0x228
runtime.schedule()
/usr/local/go/src/runtime/proc.go:2120 +0x14c
runtime.park_m(0xc420001040)
/usr/local/go/src/runtime/proc.go:2183 +0x123
runtime.mcall(0x7fff5fbff670)
/usr/local/go/src/runtime/asm_amd64.s:240 +0x5b

goroutine 1 [chan receive]:
testing.(*T).Run(0xc420092300, 0x37c0d8, 0xe, 0x3a6ba8, 0x5f215)
/usr/local/go/src/testing/testing.go:647 +0x316
testing.RunTests.func1(0xc420092300)
/usr/local/go/src/testing/testing.go:793 +0x6d
testing.tRunner(0xc420092300, 0xc42003ce30)
/usr/local/go/src/testing/testing.go:610 +0x81
testing.RunTests(0x3a6c28, 0x50b020, 0x1, 0x1, 0xf9ab)
/usr/local/go/src/testing/testing.go:799 +0x2f5
testing.(*M).Run(0xc42003cef8, 0x43)
/usr/local/go/src/testing/testing.go:743 +0x85
main.main()
github.com/yudai/gojsondiff/_test/_testmain.go:56 +0xc6

goroutine 17 [syscall, locked to thread]:
runtime.goexit()
/usr/local/go/src/runtime/asm_amd64.s:2086 +0x1

goroutine 5 [syscall]:
os/signal.signal_recv(0x0)
/usr/local/go/src/runtime/sigqueue.go:116 +0x157
os/signal.loop()
/usr/local/go/src/os/signal/signal_unix.go:22 +0x22
created by os/signal.init.1
/usr/local/go/src/os/signal/signal_unix.go:28 +0x41

goroutine 6 [runnable]:
reflect.DeepEqual(0x302bc0, 0xc420376a24, 0x302bc0, 0xc4200987f0, 0x38d)
/usr/local/go/src/reflect/deepequal.go:176
github.com/yudai/golcs.(*lcs).Table(0xc4200dc300, 0x34fee0, 0x1, 0xc4200dc300)
/Users/peter/go/src/github.com/yudai/golcs/golcs.go:55 +0x1e6
github.com/yudai/golcs.(*lcs).Length(0xc4200dc300, 0xc4200dc300)
/Users/peter/go/src/github.com/yudai/golcs/golcs.go:67 +0x2b
github.com/yudai/gojsondiff.stringSimilarity(0xc420336000, 0xe3f9, 0xc420368000, 0xa247, 0x119101)
/Users/peter/go/src/github.com/yudai/gojsondiff/gojsondiff.go:394 +0x157
github.com/yudai/gojsondiff.(*Modified).similarity(0xc4200168c0, 0xc4202c1170)
/Users/peter/go/src/github.com/yudai/gojsondiff/deltas.go:290 +0x1b8
github.com/yudai/gojsondiff.similarityCache.Similarity(0x4f1f80, 0xc4200168c0, 0xbff0000000000000, 0xc420324a48)
/Users/peter/go/src/github.com/yudai/gojsondiff/deltas.go:36 +0x50
github.com/yudai/gojsondiff.(*TextDiff).Similarity(0xc420278060, 0x10)
:68 +0x59
github.com/yudai/gojsondiff.deltasSimilarity(0xc420366060, 0x1, 0x1, 0xc42030e780)
/Users/peter/go/src/github.com/yudai/gojsondiff/gojsondiff.go:383 +0x56
github.com/yudai/gojsondiff.(*Object).similarity(0xc420014240, 0x31e7e0)
/Users/peter/go/src/github.com/yudai/gojsondiff/deltas.go:170 +0x41
github.com/yudai/gojsondiff.similarityCache.Similarity(0x4f2080, 0xc420014240, 0xbff0000000000000, 0x4f55c0)
/Users/peter/go/src/github.com/yudai/gojsondiff/deltas.go:36 +0x50
github.com/yudai/gojsondiff.(*Object).Similarity(0xc420014240, 0x4)
:35 +0x59
github.com/yudai/gojsondiff.deltasSimilarity(0xc42010f6e0, 0x2, 0x2, 0x0)
/Users/peter/go/src/github.com/yudai/gojsondiff/gojsondiff.go:383 +0x56
github.com/yudai/gojsondiff.(*Object).similarity(0xc420015640, 0x1121e)
/Users/peter/go/src/github.com/yudai/gojsondiff/deltas.go:170 +0x41
github.com/yudai/gojsondiff.similarityCache.Similarity(0x4f2080, 0xc420015640, 0xbff0000000000000, 0x100000000000000)
/Users/peter/go/src/github.com/yudai/gojsondiff/deltas.go:36 +0x50
github.com/yudai/gojsondiff.(*Object).Similarity(0xc420015640, 0x0)
:35 +0x59
github.com/yudai/gojsondiff.deltasSimilarity(0xc42019bb30, 0x1, 0x1, 0xc4202c88b0)
/Users/peter/go/src/github.com/yudai/gojsondiff/gojsondiff.go:383 +0x56
github.com/yudai/gojsondiff.(*Object).similarity(0xc420015680, 0xc420377601)
/Users/peter/go/src/github.com/yudai/gojsondiff/deltas.go:170 +0x41
github.com/yudai/gojsondiff.similarityCache.Similarity(0x4f2080, 0xc420015680, 0xbff0000000000000, 0x3204e0)
/Users/peter/go/src/github.com/yudai/gojsondiff/deltas.go:36 +0x50
github.com/yudai/gojsondiff.(*Object).Similarity(0xc420015680, 0x2)
:35 +0x59
github.com/yudai/gojsondiff.(*Differ).maximizeSimilarities(0xc420312040, 0xc42025d9c0, 0x1, 0x1, 0xc42025d9e0, 0x1, 0x1, 0xc42030eb58, 0x131078, 0xc420110780, ...)
/Users/peter/go/src/github.com/yudai/gojsondiff/gojsondiff.go:334 +0x522
github.com/yudai/gojsondiff.(*Differ).compareArrays(0xc420312040, 0xc420312830, 0x1, 0x1, 0xc420366830, 0x1, 0x1, 0x101, 0x198, 0xc4203249c8)
/Users/peter/go/src/github.com/yudai/gojsondiff/gojsondiff.go:218 +0x17d4
github.com/yudai/gojsondiff.(*Differ).compareValues(0xc420312040, 0x4f5600, 0xc420366870, 0x2fcbc0, 0xc42025d560, 0x2fcbc0, 0xc42025d8c0, 0x217, 0xc42030f340, 0x12b1ac)
/Users/peter/go/src/github.com/yudai/gojsondiff/gojsondiff.go:255 +0xcf1
github.com/yudai/gojsondiff.(*Differ).compareMaps(0xc420312040, 0xc4202c0a80, 0xc4202c10e0, 0x8, 0xc420312040, 0x0)
/Users/peter/go/src/github.com/yudai/gojsondiff/gojsondiff.go:95 +0x214
github.com/yudai/gojsondiff.(*Differ).CompareObjects(0xc420312040, 0xc4202c0a80, 0xc4202c10e0, 0xc42030f4d0, 0x23912a)
/Users/peter/go/src/github.com/yudai/gojsondiff/gojsondiff.go:72 +0x43
github.com/yudai/gojsondiff_test.glob..func1.1.1.3.1()
/Users/peter/go/src/github.com/yudai/gojsondiff/gojsondiff_test.go:41 +0xce
github.com/onsi/ginkgo/internal/leafnodes.(*runner).runSync(0xc42001ae40, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
/Users/peter/go/src/github.com/onsi/ginkgo/internal/leafnodes/runner.go:109 +0x9c
github.com/onsi/ginkgo/internal/leafnodes.(*runner).run(0xc42001ae40, 0x3, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
/Users/peter/go/src/github.com/onsi/ginkgo/internal/leafnodes/runner.go:63 +0xe1
github.com/onsi/ginkgo/internal/leafnodes.(*ItNode).Run(0xc42010f320, 0x4f1e00, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
/Users/peter/go/src/github.com/onsi/ginkgo/internal/leafnodes/it_node.go:25 +0x64
github.com/onsi/ginkgo/internal/spec.(*Spec).runSample(0xc4201124e0, 0x0, 0x4f1e00, 0xc4200111d0)
/Users/peter/go/src/github.com/onsi/ginkgo/internal/spec/spec.go:176 +0x4fd
github.com/onsi/ginkgo/internal/spec.(*Spec).Run(0xc4201124e0, 0x4f1e00, 0xc4200111d0)
/Users/peter/go/src/github.com/onsi/ginkgo/internal/spec/spec.go:127 +0xd4
github.com/onsi/ginkgo/internal/specrunner.(*SpecRunner).runSpec(0xc4201a79e0, 0xc4201124e0, 0xc420041b01)
/Users/peter/go/src/github.com/onsi/ginkgo/internal/specrunner/spec_runner.go:172 +0xed
github.com/onsi/ginkgo/internal/specrunner.(*SpecRunner).runSpecs(0xc4201a79e0, 0x3a6b01)
/Users/peter/go/src/github.com/onsi/ginkgo/internal/specrunner/spec_runner.go:142 +0x2b3
github.com/onsi/ginkgo/internal/specrunner.(*SpecRunner).Run(0xc4201a79e0, 0x10)
/Users/peter/go/src/github.com/onsi/ginkgo/internal/specrunner/spec_runner.go:61 +0xf0
github.com/onsi/ginkgo/internal/suite.(*Suite).Run(0xc420016fa0, 0x1148348, 0xc4200923c0, 0x37ce84, 0x10, 0xc42019b530, 0x1, 0x1, 0x4f6d40, 0xc4200111d0, ...)
/Users/peter/go/src/github.com/onsi/ginkgo/internal/suite/suite.go:59 +0x23b
github.com/onsi/ginkgo.RunSpecsWithCustomReporters(0x4f2c40, 0xc4200923c0, 0x37ce84, 0x10, 0xc42030bf00, 0x1, 0x1, 0x0)
/Users/peter/go/src/github.com/onsi/ginkgo/ginkgo_dsl.go:218 +0x27b
github.com/onsi/ginkgo.RunSpecs(0x4f2c40, 0xc4200923c0, 0x37ce84, 0x10, 0xc42c529adc)
/Users/peter/go/src/github.com/onsi/ginkgo/ginkgo_dsl.go:199 +0x208
github.com/yudai/gojsondiff_test.TestGojsondiff(0xc4200923c0)
/Users/peter/go/src/github.com/yudai/gojsondiff/gojsondiff_suite_test.go:12 +0x64
testing.tRunner(0xc4200923c0, 0x3a6ba8)
/usr/local/go/src/testing/testing.go:610 +0x81
created by testing.(*T).Run
/usr/local/go/src/testing/testing.go:646 +0x2ec

goroutine 7 [chan receive]:
github.com/onsi/ginkgo/internal/specrunner.(*SpecRunner).registerForInterrupts(0xc4201a79e0)
/Users/peter/go/src/github.com/onsi/ginkgo/internal/specrunner/spec_runner.go:194 +0x13f
created by github.com/onsi/ginkgo/internal/specrunner.(*SpecRunner).Run
/Users/peter/go/src/github.com/onsi/ginkgo/internal/specrunner/spec_runner.go:56 +0x74

goroutine 18 [select, locked to thread]:
runtime.gopark(0x3a7358, 0x0, 0x3778ec, 0x6, 0x18, 0x2)
/usr/local/go/src/runtime/proc.go:259 +0x13a
runtime.selectgoImpl(0xc420028730, 0x0, 0x18)
/usr/local/go/src/runtime/select.go:423 +0x11d9
runtime.selectgo(0xc420028730)
/usr/local/go/src/runtime/select.go:238 +0x1c
runtime.ensureSigM.func1()
/usr/local/go/src/runtime/signal1_unix.go:304 +0x2d1
runtime.goexit()
/usr/local/go/src/runtime/asm_amd64.s:2086 +0x1

rax 0xe
rbx 0x514220
rcx 0x7fff5fbff3f0
rdx 0x7fff5fbff478
rdi 0xd03
rsi 0xc420025500
rbp 0x7fff5fbff428
rsp 0x7fff5fbff3f0
r8 0xc420001040
r9 0x1
r10 0x223abe0
r11 0x286
r12 0x1
r13 0x1
r14 0x1
r15 0x406ce8
rip 0x5f50b
rflags 0x286
cs 0x7
fs 0x0
gs 0x0
exit status 2
FAIL github.com/yudai/gojsondiff 15.962s

[pteichman]

This may be a bug / pathological input in golcs instead.