Help with an intermittent invalid memory address error

[Todd_Nine]

Hi all,
I’m at a loss. I’m running an integration test with google cloud datastore, and occasionally I will receive this error.

Search User By Email [It]
  /Users/toddnine/develop/go/src/github.com/cradlekiwi/api/dataaccess/user_test.go:157

  Test Panicked
  runtime error: invalid memory address or nil pointer dereference
  /usr/local/Cellar/go/1.7.4_2/libexec/src/runtime/panic.go:458

  Full Stack Trace
  	  /usr/local/Cellar/go/1.7.4_2/libexec/src/runtime/panic.go:458 +0x243

github.com/cradlekiwi/api/dataaccess_test.(*userAssert).assertSameUser(0x95a380, 0xc420017080, 0x0)
/Users/toddnine/develop/go/src/github.com/cradlekiwi/api/dataaccess/user_test.go:258 +0x19f

What’s odd, is the code in the test from the trace above has an explicit nil check before it’s assertion on actual.ID, which is the line 258 from the trace.

func (u *userAssert) assertSameUser(expected *model.User, actual *model.User) {
Expect(expected).ShouldNot(BeNil())
Expect(actual).ShouldNot(BeNil())
Expect(actual.ID).ShouldNot(BeNil())
}

If I’ve asserted the field “actual” is not nil the line before I check it’s field ID, how can I possibly be getting an invalid memory address or a nil pointer? This error is completely intermittent. I see it in 1 out of around 14 test runs. What’s very odd is I can reproduce it in both a docker container and on my OSX laptop. All envs are go 1.7.4. I’ve noticed this since 1.6, and I’m making it a priority to track it down. Any help would be greatly appreciated!

Thanks,
Todd

[christophberger]

According to the stack trace output, actual is indeed nil:

github.com/cradlekiwi/api/dataaccess_test.(*userAssert).assertSameUser(0x95a380, 0xc420017080, 0x0)

(First parameter is the method receiver u, second is expected, and third is actual.)
Seems the test library fails to detect this nil value.

[Tamas_Gulacsi (Tamás Gulácsi)]

I assume the test lib uses an interface{} which won’t be nil, though the boxed value is nil.
Use plain old “if actual == nil” to detect it.