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Document the difference of embedded swift's swift_allocBox

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Arnold Schwaighofer
2025-11-17 08:09:05 -08:00
parent 84501bd6e2
commit 02d7fe5110
1 changed files with 9 additions and 0 deletions
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9
stdlib/public/core/EmbeddedRuntime.swift
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@@ -261,6 +261,15 @@ public func swift_allocEmptyBox() -> Builtin.RawPointer {
return box
}
/// The embedded swift_allocBox version is different to the standad one in that
/// we want to avoid building metadata for the box type. Instead we store the
/// metadata of the contained type in the heap object. To make this work when
/// destroying the box the release needs to be special i.e `swift_releaseBox`.
/// It does not call the the heap object metadata's destroy function. Rather, it
/// knows that the allocBox's metadata is the contained objects and calls an
/// appropriate implementation: `_swift_embedded_invoke_box_destroy`.
/// Therefore, one cannot not use `swift_release` but rather must use
/// `swift_releaseBox` to implement the "release" function of a box object.
@_silgen_name("swift_allocBox")
public func swift_allocBox(_ metadata: Builtin.RawPointer) -> (Builtin.RawPointer, Builtin.RawPointer) {