fatal error: sweep increased allocation count

[tonyghita]

Hi, running this library on go 1.8.3 and seeing occasional crashes with fatal error: sweep increased allocation count.

I think this may be related to the usage of reflect.Call() but so far have not been able to reproduce locally. (Relevant issue: golang/go#21717).

Has anyone else observed this error?

[tonyghita]

I found the issue.

type Alphabet {
 a: String!
 b: String!
 c: String!
}

type Query {
  alphabet: Alphabet!
}

type AlphabetResolver struct {}
func (r AlphabetResolver) A() string {
  return "a"
}
func (r AlphabetResolver) B() string {
  return "b"
}
func (r AlphabetResolver) C() string {
  return "c"
}

type QueryResolver struct {}

func (r  *QueryResolver) Alphabet() AlphabetResolver {
  return AlphabetResolver{}
}

This causes the reflect.Value.Call() invocation to corrupt memory in go1.8.3 and go1.9.01.
Changing to the below fixes the zero-length return issue.

func (r  *QueryResolver) Alphabet() (*AlphabetResolver, error) {
  return &AlphabetResolver{}, nil
}

[dmitshur]

This causes the reflect.Value.Call() invocation to corrupt memory in go1.8.3 and go1.9.1.

Did you mean Go 1.9.0 or 1.9.1? If the latter, is this a different issue than golang/go#21717? Is it already reported?

[tonyghita]

Ah sorry, I meant go1.9.0. The fix looks slated for the 1.9.1 milestone.

If you wanted to be safe in the meantime, you can build go from source and cherry-pick 0a48185b4383fac8d260112efa261112f3d41ee2 onto the release you're using.

[dmitshur]

Thanks for confirming that it's not an issue in 1.9.1.