From 5ded13c8dd29a936f2bb4e6188b7c1e8d5c42173 Mon Sep 17 00:00:00 2001
From: Slava Pestov <spestov@apple.com>
Date: Tue, 1 Nov 2016 23:36:11 -0600
Subject: [PATCH] stdlib: Make Unsafe{Mutable,}BufferPointer @_fixed_layout to
 work around rdar://18157434

---
 stdlib/public/core/UnsafeBufferPointer.swift.gyb | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/stdlib/public/core/UnsafeBufferPointer.swift.gyb b/stdlib/public/core/UnsafeBufferPointer.swift.gyb
index 8cab8155833a3..2719e0b0fae19 100644
--- a/stdlib/public/core/UnsafeBufferPointer.swift.gyb
+++ b/stdlib/public/core/UnsafeBufferPointer.swift.gyb
@@ -36,6 +36,11 @@ public struct UnsafeBufferPointerIterator<Element>
 /// underlying elements.
 ///
 /// The pointer should be aligned to `MemoryLayout<Element>.alignment`.
+
+// FIXME: rdar://18157434 - until this is fixed, this has to be fixed layout
+// to avoid a hang in Foundation, which has the following setup:
+// struct A { struct B { let x: UnsafeMutableBufferPointer<...> } let b: B }
+@_fixed_layout
 public struct Unsafe${Mutable}BufferPointer<Element>
   : _${Mutable}Indexable, ${Mutable}Collection, RandomAccessCollection {