hi, I'm looking at the docs and am not fully sure ...

# kotlin-native

[Bernhard]

hi, I'm looking at the docs and am not fully sure how Kotlin native works in the memory department; what values require manual management and which ones are handled by a GC?

[ephemient]

Kotlin objects are all GC'able (except when pinned). C interop requires manual management

[Bernhard]

let's say you read in values from C and put them into a dataclass,what do you need to do

[Bernhard]

same vice versa

[Bernhard]

do you need to copy those?

[ephemient]

it depends*

[ephemient]

read in values from C

sounds like a copy to begin with though

[ephemient]

and exposing Kotlin objects to C always involves copying or pinning

[Bernhard]

pinning is basically once it goes out of scope it gets cleaned up? similar to Rust's Drop?

[ephemient]

no

[ephemient]

think like JNI

[Bernhard]

no experience with that unfortunately

[ephemient]

when an object is pinned, you are telling the garbage collector: "there is some reference to this object that you do not know about, do not touch this object"

[ephemient]

it is up to you to unpin the object when you're done or else it is a leak

[Bernhard]

I see

[Bernhard]

as for getting values from C; let's assume that you read in a jpg file using some C lib and it passes you a byte array

[Bernhard]

the array is malloced ofc

[Bernhard]

how would you transfer that into a kotlin data class

[Bernhard]

I suppose you don't want to copy that

[ephemient]

in most situations I would make a full copy to a Kotlin ByteArray or similar, so that it will work with all other existing Kotlin functions and types