[ATsch]

That should work perfectly with multiple structs. Define

    #[repr("C")]
    struct MyThing {
        length: usize,
        data: MaybeUninit<MyInner>
    }

Then initialize with sizeof(data) and MaybeUninit::uninitialized(). When the call is complete, assume_init() and access the fields of the result struct as normal.

[pjmlp]

I see, thanks.