Struct ClosureCtx 

pub struct ClosureCtx { /* private fields */ }

Context for a Swift () -> T closure implemented in Rust.

Swift treats a closure context as a reference-counted heap object. A non-escaping closure never touches the count, but an escaping one — a Button’s action, say — is stored by the receiver, which retains it now and releases it later. Handing Swift a plain Box means it eventually calls swift_release on memory that is not a Swift object, and the process dies with SIGBUS long after the call that caused it.

So the first two words mirror a Swift object header and carry the refcount pattern of a known immortal object, which makes retain and release no-ops.

Implementations

impl ClosureCtx

pub fn new( body: unsafe extern "C" fn(*mut u8, *mut c_void), payload: *mut c_void, ) -> Self

body receives (out_ptr, payload) and must initialise *out_ptr with a +1 value (or ignore it, for a closure returning Void).