I’m trying to understand why some of my tests are ...

# kotlin-native

[saket]

I’m trying to understand why some of my tests are failing with InvalidMutabilityException on native platforms because they use lazy{} values. My code is single threaded and does not freeze objects anywhere. Are test graphs frozen by default on native platforms?

update: TIL objects are frozen by default!

[Dominaezzz]

lazy iirc, freezes it's values by default.

[saket]

that’s what I was suspecting, but this code doesn’t use freezing anywhere:

[Dominaezzz]

That's the unsafe one. The safe one it the one I'm referring to.

[saket]

The stacktrace mentions this unsafe variant:

kotlin.native.concurrent.InvalidMutabilityException: mutation attempt of frozen kotlin.UnsafeLazyImpl@a9615c98

am I looking at the wrong place?

[Dominaezzz]

Ah. You didn't share stacktrace.

[Dominaezzz]

Are you using this lazy property in an object ?

[saket]

Yea sorry, here’s the stacktrace if it’s useful:

Untitled

[saket]

Yes, it’s an object !

[Dominaezzz]

Have you annotated the object with @ThreadLocal ?

[Dominaezzz]

If you haven't, then you have your answer.

[saket]

Whoaa TIL objects are frozen by default!

[saket]

Thanks again @Dominaezzz!

[mbonnin]

I've been bitten by that as well. It feels weird that objects are not lazy attached to the first thread that accesses them

[mbonnin]

I found this post interesting about testing these kind of behaviours: https://jakewharton.com/litmus-testing-kotlins-many-memory-models/

[saket]

Yea I understand why objects are frozen automatically, but I wish the reason was easily discoverable.

[mbonnin]

Yep, some kind of lint warning on objects without an annotation would be helpfull

[saket]

fwiw I ended up replacing lazy with atomicLazy