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Runtime ABI

Canonical source: docs/runtime_abi.md

Goals

  • Performance-first data layouts
  • Stable, versioned ABI
  • Zero-copy slices
  • Clear interop boundaries for FFI

Core Data Layouts

String

{ u8* data, i64 len }   // UTF-8, not NUL-terminated

Array (Owned)

{ T* data, i64 len, i64 cap }

Slice (Borrowed)

{ T* data, i64 len }    // Non-resizable view

Dynamic Value

{ i64 tag, union{...} payload }   // Tagged union

Ownership Model (v0)

Hybrid approach: reference counting + arenas.

  • Arenas for short-lived allocations (within a scope)
  • Reference counting for values that escape their scope
  • Explicit retain/release for RC-managed values

Exception / Unwind ABI

Structured frames with deterministic unwind. Currently implemented via C runtime’s setjmp/longjmp, planned to move to native structured exceptions.

The runtime is actively migrating from C to Sailfin. See the runtime audit for current status.