Merge pull request #75394 from swiftlang/revert-75148-dangerous-forbidden-technique

Revert "Use associated objects to attach contiguous array buffers to lazy ones"

Author: shahmishal

stdlib/public/SwiftShims/swift/shims/CMakeLists.txt

@@ -9,7 +9,6 @@ set(sources
   LibcOverlayShims.h
   LibcShims.h
   MetadataSections.h
-  ObjCShims.h
   Random.h
   RefCount.h
   Reflection.h

stdlib/public/SwiftShims/swift/shims/CoreFoundationShims.h

@@ -30,11 +30,9 @@ extern "C" {
 #if __LLP64__
 typedef unsigned long long _swift_shims_CFHashCode;
 typedef signed long long _swift_shims_CFIndex;
-
 #else
 typedef unsigned long _swift_shims_CFHashCode;
 typedef signed long _swift_shims_CFIndex;
-
 #endif
 
 // Consider creating SwiftMacTypes.h for these
@@ -76,7 +74,7 @@ _swift_stdlib_NSStringGetCStringTrampoline(id _Nonnull obj,
 SWIFT_RUNTIME_STDLIB_API
 __swift_uint8_t
 _swift_stdlib_dyld_is_objc_constant_string(const void * _Nonnull addr);
-
+  
 #endif // __OBJC2__
 
 #ifdef __cplusplus

stdlib/public/SwiftShims/swift/shims/ObjCShims.h

@@ -1,7 +1,6 @@
 module SwiftShims {
   header "AssertionReporting.h"
   header "CoreFoundationShims.h"
-  header "ObjCShims.h"
   header "EmbeddedShims.h"
   header "FoundationShims.h"
   header "GlobalObjects.h"

stdlib/public/SwiftShims/swift/shims/module.modulemap

@@ -567,81 +567,6 @@ extension _ArrayBuffer {
     }
   }
 
-  @inlinable @_alwaysEmitIntoClient
-  static var associationKey: UnsafeRawPointer {
-    //We never dereference this, we just need an address to use as a unique key
-    UnsafeRawPointer(Builtin.addressof(&_swiftEmptyArrayStorage))
-  }
-  
-  @inlinable @_alwaysEmitIntoClient
-  internal func getAssociatedBuffer() -> _ContiguousArrayBuffer<Element>? {
-    let getter = unsafeBitCast(
-      getGetAssociatedObjectPtr(),
-      to: (@convention(c)(
-        AnyObject,
-        UnsafeRawPointer
-      ) -> UnsafeRawPointer?).self
-    )
-    if let assocPtr = getter(
-      _storage.objCInstance,
-      _ArrayBuffer.associationKey
-    ) {
-      let buffer = assocPtr.loadUnaligned(
-        as: _ContiguousArrayStorage<Element>.self
-      )
-      return _ContiguousArrayBuffer(buffer)
-    }
-    return nil
-  }
-  
-  @inlinable @_alwaysEmitIntoClient
-  internal func setAssociatedBuffer(_ buffer: _ContiguousArrayBuffer<Element>) {
-    let setter = unsafeBitCast(getSetAssociatedObjectPtr(), to: (@convention(c)(
-      AnyObject,
-      UnsafeRawPointer,
-      AnyObject?,
-      UInt
-    ) -> Void).self)
-    setter(
-      _storage.objCInstance,
-      _ArrayBuffer.associationKey,
-      buffer._storage,
-      1 //OBJC_ASSOCIATION_RETAIN_NONATOMIC
-    )
-  }
-  
-  @_alwaysEmitIntoClient @inline(never)
-  internal func withUnsafeBufferPointer_nonNative<R>(
-    _ body: (UnsafeBufferPointer<Element>) throws -> R
-  ) rethrows -> R {
-    let unwrapped: _ContiguousArrayBuffer<Element>
-    // libobjc already provides the necessary memory barriers for
-    // double checked locking to be safe, per comments on
-    // https://github.com/swiftlang/swift/pull/75148
-    if let associatedBuffer = getAssociatedBuffer() {
-      unwrapped = associatedBuffer
-    } else {
-      let lock = _storage.objCInstance
-      objc_sync_enter(lock)
-      var associatedBuffer = getAssociatedBuffer()
-      if let associatedBuffer {
-        unwrapped = associatedBuffer
-      } else {
-        associatedBuffer = ContiguousArray(self)._buffer
-        unwrapped = associatedBuffer.unsafelyUnwrapped
-        setAssociatedBuffer(unwrapped)
-      }
-      defer { _fixLifetime(unwrapped) }
-      objc_sync_exit(lock)
-    }
-    return try body(
-      UnsafeBufferPointer(
-        start: unwrapped.firstElementAddress,
-        count: unwrapped.count
-      )
-    )
-  }
-  
   /// Call `body(p)`, where `p` is an `UnsafeBufferPointer` over the
   /// underlying contiguous storage.  If no such storage exists, it is
   /// created on-demand.
@@ -654,7 +579,7 @@ extension _ArrayBuffer {
       return try body(
         UnsafeBufferPointer(start: firstElementAddress, count: count))
     }
-    return try withUnsafeBufferPointer_nonNative(body)
+    return try ContiguousArray(self).withUnsafeBufferPointer(body)
   }
 
   /// Call `body(p)`, where `p` is an `UnsafeMutableBufferPointer`

stdlib/public/core/ArrayBuffer.swift

@@ -51,16 +51,12 @@ internal struct _CocoaArrayWrapper: RandomAccessCollection {
 
   @usableFromInline
   internal var endIndex: Int {
-    @_effects(releasenone) get {
-      core.count
-    }
+    return core.count
   }
 
   @usableFromInline
   internal subscript(i: Int) -> AnyObject {
-    @_effects(releasenone) get {
-      core.objectAt(i)
-    }
+    return core.objectAt(i)
   }
 
   @usableFromInline

stdlib/public/core/CocoaArray.swift

@@ -112,6 +112,5 @@ typedef __swift_uint8_t (*getCStringImplPtr)(id,
           && SWIFT_RUNTIME_WEAK_USE(_dyld_is_objc_constant(dyld_objc_string_kind, addr))) ? 1 : 0;
 }
 
-
 #endif