[swift-evolution] [Pitch] deprecating ManagedBufferPointer

Erik Eckstein eeckstein at apple.com
Mon Oct 10 17:12:28 CDT 2016

The purpose of ManagedBufferPointer is to create a buffer with a custom class-metadata to be able to implement a custom deinit (e.g. to destroy the tail allocated elements).
It was used in Array (before I replaced it with the new tail-allocated-array-built-ins). But now it’s not used anymore in the standard library.

As a replacement for ManagedBufferPointer one can just derive a class from ManagedBuffer and implement the deinit in the derived class.

final class MyBuffer : ManagedBuffer<MyHeader, MyElements> {
  deinit {
    // do whatever needs to be done

// creating MyBuffer:
let b = MyBuffer.create(minimumCapacity: 27, makingHeaderWith: { myb in return MyHeader(...) })

IMO ManagedBuffer is much cleaner than ManagedBufferPointer (it doesn’t need this custom bufferClass to be passed to the constructor). Also ManagedBufferPointer doesn’t use SIL tail-allocated arrays internally. Although this is not something visible to the programmer, it makes life easier for the compiler.

So I suggest that we deprecate ManagedBufferPointer.

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