FFI and Interoperability — Middle¶

Use C-compatible layouts only where promised. Pin or copy objects when a moving collector could relocate them. Translate error codes at the boundary, and specify whether callbacks may arrive on foreign threads. Batch work to amortize crossing and marshalling costs.

Test yourself¶

1. When must memory be pinned?
2. Why are coarse FFI calls preferable?
3. How do callbacks affect thread safety?

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