Runtime: Tweak Mirrors for resilience

Make _MagicMirrorData @_fixed_layout, but not the concrete mirror
implementations.

To make the calling convention work in resilient builds, make the
runtime entry points into top-level functions that take a
_MagicMirrorData, instead of adding @_silgen_name attributes on
methods.

This involves changing the convention on the 'owner' parameter
from +0 to +1.

Also, there was a memory leak in the old enum code that I noticed
by inspection. We would copy the enum value into a box, strip
the enum tag bits, take the box contents but never free the box
itself.

The fix isn't very satisfying either -- we have to modify the
source enum in-place to strip tag bits, then we copy it into a
box having the right payload type, and add the tag bits back.
At least this way, we can free the box after.

Author: slavapestov

stdlib/public/core/ObjCMirrors.swift

@@ -42,7 +42,9 @@ struct _ObjCMirror : _Mirror {
     return _getObjCSummary(data)
   }
   public var quickLookObject: PlaygroundQuickLook? {
-    return _getClassPlaygroundQuickLook(data)
+    var result: PlaygroundQuickLook? = nil
+    _getClassPlaygroundQuickLook(&result, data)
+    return result
   }
   public var disposition: _MirrorDisposition { return .objCObject }
 }
@@ -68,7 +70,9 @@ struct _ObjCSuperMirror : _Mirror {
     return _getObjCSummary(data)
   }
   public var quickLookObject: PlaygroundQuickLook? {
-    return _getClassPlaygroundQuickLook(data)
+    var result: PlaygroundQuickLook? = nil
+    _getClassPlaygroundQuickLook(&result, data)
+    return result
   }
   public var disposition: _MirrorDisposition { return .objCObject }
 }

stdlib/public/core/Reflection.swift

@@ -361,6 +361,7 @@ func _swift_MagicMirrorData_summaryImpl(
   metadata: Any.Type, _ result: UnsafeMutablePointer<String>
 )
 
+@_fixed_layout
 public struct _MagicMirrorData {
   let owner: Builtin.NativeObject
   let ptr: Builtin.RawPointer
@@ -407,40 +408,59 @@ struct _OpaqueMirror : _Mirror {
   var disposition: _MirrorDisposition { return .aggregate }
 }
 
+@warn_unused_result
+@_silgen_name("swift_TupleMirror_count")
+func _getTupleCount(_: _MagicMirrorData) -> Int
+
+// Like the other swift_*Mirror_subscript functions declared here and
+// elsewhere, this is implemented in the runtime.  The Swift CC would
+// normally require the String to be returned directly and the _Mirror
+// indirectly.  However, Clang isn't currently capable of doing that
+// reliably because the size of String exceeds the normal direct-return
+// ABI rules on most platforms.  Therefore, we make this function generic,
+// which has the disadvantage of passing the String type metadata as an
+// extra argument, but does force the string to be returned indirectly.
+@warn_unused_result
+@_silgen_name("swift_TupleMirror_subscript")
+func _getTupleChild<T>(_: Int, _: _MagicMirrorData) -> (T, _Mirror)
+
 internal struct _TupleMirror : _Mirror {
   let data: _MagicMirrorData
 
   var value: Any { return data.value }
   var valueType: Any.Type { return data.valueType }
   var objectIdentifier: ObjectIdentifier? { return nil }
   var count: Int {
-    @_silgen_name("swift_TupleMirror_count")get
+    return _getTupleCount(data)
   }
   subscript(i: Int) -> (String, _Mirror) {
-    return _subscript_get(i)
+    return _getTupleChild(i, data)
   }
-  @_silgen_name("swift_TupleMirror_subscript")
-  func _subscript_get<T>(i: Int) -> (T, _Mirror)
-
   var summary: String { return "(\(count) elements)" }
   var quickLookObject: PlaygroundQuickLook? { return nil }
   var disposition: _MirrorDisposition { return .tuple }
 }
 
+@warn_unused_result
+@_silgen_name("swift_StructMirror_count")
+func _getStructCount(_: _MagicMirrorData) -> Int
+
+@warn_unused_result
+@_silgen_name("swift_StructMirror_subscript")
+func _getStructChild<T>(_: Int, _: _MagicMirrorData) -> (T, _Mirror)
+
 struct _StructMirror : _Mirror {
   let data: _MagicMirrorData
 
   var value: Any { return data.value }
   var valueType: Any.Type { return data.valueType }
   var objectIdentifier: ObjectIdentifier? { return nil }
   var count: Int {
-    @_silgen_name("swift_StructMirror_count")get
+    return _getStructCount(data)
   }
   subscript(i: Int) -> (String, _Mirror) {
-    return _subscript_get(i)
+    return _getStructChild(i, data)
   }
-  @_silgen_name("swift_StructMirror_subscript")
-  func _subscript_get<T>(i: Int) -> (T, _Mirror)
 
   var summary: String {
     return _typeName(valueType)
@@ -449,23 +469,34 @@ struct _StructMirror : _Mirror {
   var disposition: _MirrorDisposition { return .`struct` }
 }
 
+@warn_unused_result
+@_silgen_name("swift_EnumMirror_count")
+func _getEnumCount(_: _MagicMirrorData) -> Int
+
+@warn_unused_result
+@_silgen_name("swift_EnumMirror_subscript")
+func _getEnumChild<T>(_: Int, _: _MagicMirrorData) -> (T, _Mirror)
+
+@warn_unused_result
+@_silgen_name("swift_EnumMirror_caseName")
+func _swift_EnumMirror_caseName(
+    data: _MagicMirrorData) -> UnsafePointer<CChar>
+
 struct _EnumMirror : _Mirror {
   let data: _MagicMirrorData
 
   var value: Any { return data.value }
   var valueType: Any.Type { return data.valueType }
   var objectIdentifier: ObjectIdentifier? { return nil }
   var count: Int {
-    @_silgen_name("swift_EnumMirror_count")get
+    return _getEnumCount(data)
   }
   var caseName: UnsafePointer<CChar> {
-    @_silgen_name("swift_EnumMirror_caseName")get
+    return _swift_EnumMirror_caseName(data)
   }
   subscript(i: Int) -> (String, _Mirror) {
-    return _subscript_get(i)
+    return _getEnumChild(i, data)
   }
-  @_silgen_name("swift_EnumMirror_subscript")
-  func _subscript_get<T>(i: Int) -> (T, _Mirror)
 
   var summary: String {
     let maybeCaseName = String(validatingUTF8: self.caseName)
@@ -483,24 +514,16 @@ struct _EnumMirror : _Mirror {
 @_silgen_name("swift_ClassMirror_count")
 func _getClassCount(_: _MagicMirrorData) -> Int
 
-// Like the other swift_*Mirror_subscript functions declared here and
-// elsewhere, this is implemented in the runtime.  The Swift CC would
-// normally require the String to be returned directly and the _Mirror
-// indirectly.  However, Clang isn't currently capable of doing that
-// reliably because the size of String exceeds the normal direct-return
-// ABI rules on most platforms.  Therefore, we make this function generic,
-// which has the disadvantage of passing the String type metadata as an
-// extra argument, but does force the string to be returned indirectly.
 @warn_unused_result
 @_silgen_name("swift_ClassMirror_subscript")
 func _getClassChild<T>(_: Int, _: _MagicMirrorData) -> (T, _Mirror)
 
 #if _runtime(_ObjC)
-@warn_unused_result
 @_silgen_name("swift_ClassMirror_quickLookObject")
 public func _getClassPlaygroundQuickLook(
-  data: _MagicMirrorData
-) -> PlaygroundQuickLook?
+  _: inout PlaygroundQuickLook?,
+  _: _MagicMirrorData
+)
 #endif
 
 struct _ClassMirror : _Mirror {
@@ -522,7 +545,9 @@ struct _ClassMirror : _Mirror {
   }
   var quickLookObject: PlaygroundQuickLook? {
 #if _runtime(_ObjC)
-    return _getClassPlaygroundQuickLook(data)
+    var result: PlaygroundQuickLook? = nil
+    _getClassPlaygroundQuickLook(&result, data)
+    return result
 #else
     return nil
 #endif

stdlib/public/runtime/Reflection.mm

@@ -495,6 +495,7 @@ intptr_t swift_TupleMirror_count(HeapObject *owner,
                                  const OpaqueValue *value,
                                  const Metadata *type) {
   auto Tuple = static_cast<const TupleTypeMetadata *>(type);
+  swift_release(owner);
   return Tuple->NumElements;
 }
 
@@ -524,9 +525,6 @@ void swift_TupleMirror_subscript(String *outString,
   auto bytes = reinterpret_cast<const char*>(value);
   auto eltData = reinterpret_cast<const OpaqueValue *>(bytes + elt.Offset);
 
-  // This retain matches the -1 in reflect.
-  swift_retain(owner);
-
   // 'owner' is consumed by this call.
   new (outMirror) Mirror(reflect(owner, eltData, elt.Type));
 }
@@ -551,6 +549,7 @@ intptr_t swift_StructMirror_count(HeapObject *owner,
                                   const OpaqueValue *value,
                                   const Metadata *type) {
   auto Struct = static_cast<const StructMetadata *>(type);
+  swift_release(owner);
   return Struct->Description->Struct.NumFields;
 }
 
@@ -576,9 +575,6 @@ void swift_StructMirror_subscript(String *outString,
 
   new (outString) String(getFieldName(Struct->Description->Struct.FieldNames, i));
 
-  // This matches the -1 in reflect.
-  swift_retain(owner);
-
   // 'owner' is consumed by this call.
   assert(!fieldType.isIndirect() && "indirect struct fields not implemented");
   new (outMirror) Mirror(reflect(owner, fieldData, fieldType.getType()));
@@ -635,14 +631,19 @@ static void getEnumMirrorInfo(const OpaqueValue *value,
 const char *swift_EnumMirror_caseName(HeapObject *owner,
                                       const OpaqueValue *value,
                                       const Metadata *type) {
-  if (!isEnumReflectable(type))
+  if (!isEnumReflectable(type)) {
+    swift_release(owner);
     return nullptr;
+  }
 
   const auto Enum = static_cast<const EnumMetadata *>(type);
   const auto &Description = Enum->Description->Enum;
 
   unsigned tag;
   getEnumMirrorInfo(value, type, &tag, nullptr, nullptr);
+
+  swift_release(owner);
+
   return getFieldName(Description.CaseNames, tag);
 }
 
@@ -667,6 +668,7 @@ static void getEnumMirrorInfo(const OpaqueValue *value,
 
   MagicMirror *theMirror = reinterpret_cast<MagicMirror *>(&mirror);
   MagicMirrorData data = theMirror->Data;
+  swift_retain(data.Owner);
   const char *result = swift_EnumMirror_caseName(data.Owner, data.Value, data.Type);
   type->vw_destroy(value);
   return result;
@@ -677,11 +679,14 @@ static void getEnumMirrorInfo(const OpaqueValue *value,
 intptr_t swift_EnumMirror_count(HeapObject *owner,
                                 const OpaqueValue *value,
                                 const Metadata *type) {
-  if (!isEnumReflectable(type))
+  if (!isEnumReflectable(type)) {
+    swift_release(owner);
     return 0;
+  }
 
   const Metadata *payloadType;
   getEnumMirrorInfo(value, type, nullptr, &payloadType, nullptr);
+  swift_release(owner);
   return (payloadType != nullptr) ? 1 : 0;
 }
 
@@ -702,23 +707,28 @@ void swift_EnumMirror_subscript(String *outString,
 
   getEnumMirrorInfo(value, type, &tag, &payloadType, &indirect);
 
-  // Copy the payload since the projection is destructive.
-  BoxPair pair = swift_allocBox(type);
+  // Copy the enum payload into a box
+  const Metadata *boxType = (indirect ? &_TMBo.base : payloadType);
+  BoxPair pair = swift_allocBox(boxType);
+
+  type->vw_destructiveProjectEnumData(const_cast<OpaqueValue *>(value));
+  boxType->vw_initializeWithCopy(pair.second, const_cast<OpaqueValue *>(value));
+  type->vw_destructiveInjectEnumTag(const_cast<OpaqueValue *>(value),
+                                    (int) (tag - Description.getNumPayloadCases()));
+
+  swift_release(owner);
 
   owner = pair.first;
-  type->vw_initializeWithTake(pair.second, const_cast<OpaqueValue *>(value));
-  type->vw_destructiveProjectEnumData(pair.second);
   value = pair.second;
 
   // If the payload is indirect, we need to jump through the box to get it.
   if (indirect) {
     owner = *reinterpret_cast<HeapObject * const *>(value);
     value = swift_projectBox(const_cast<HeapObject *>(owner));
+    swift_retain(owner);
+    swift_release(pair.first);
   }
 
-  // This matches the -1 in reflect.
-  swift_retain(owner);
-
   new (outString) String(getFieldName(Description.CaseNames, tag));
   new (outMirror) Mirror(reflect(owner, value, payloadType));
 }
@@ -970,10 +980,10 @@ void swift_ObjCMirror_subscript(String *outString,
 }
 
 SWIFT_RUNTIME_STDLIB_INTERFACE
-extern "C" OptionalPlaygroundQuickLook
-swift_ClassMirror_quickLookObject(HeapObject *owner, const OpaqueValue *value,
+extern "C" void
+swift_ClassMirror_quickLookObject(OptionalPlaygroundQuickLook &result,
+                                  HeapObject *owner, const OpaqueValue *value,
                                   const Metadata *type) {
-  OptionalPlaygroundQuickLook result;
   memset(&result, 0, sizeof(result));
 
   id object = [*reinterpret_cast<const id *>(value) retain];
@@ -1013,7 +1023,7 @@ void swift_ObjCMirror_subscript(String *outString,
 
     [object release];
     result.optional.isNone = false;
-    return result;
+    return;
   }
 
   // Various other framework types are used for rich representations.
@@ -1028,7 +1038,7 @@ void swift_ObjCMirror_subscript(String *outString,
     initializeAnyWithTakeOfObject(result.payload.Any, object);
     result.payload.Kind = PlaygroundQuickLook::Tag::AttributedString;
     result.optional.isNone = false;
-    return result;
+    return;
   } else if ([object isKindOfClass:NSClassFromString(@"NSImage")]
       || [object isKindOfClass:NSClassFromString(@"UIImage")]
       || [object isKindOfClass:NSClassFromString(@"NSImageView")]
@@ -1038,31 +1048,30 @@ void swift_ObjCMirror_subscript(String *outString,
     initializeAnyWithTakeOfObject(result.payload.Any, object);
     result.payload.Kind = PlaygroundQuickLook::Tag::Image;
     result.optional.isNone = false;
-    return result;
+    return;
   } else if ([object isKindOfClass:NSClassFromString(@"NSColor")]
              || [object isKindOfClass:NSClassFromString(@"UIColor")]) {
     initializeAnyWithTakeOfObject(result.payload.Any, object);
     result.payload.Kind = PlaygroundQuickLook::Tag::Color;
     result.optional.isNone = false;
-    return result;
+    return;
   } else if ([object isKindOfClass:NSClassFromString(@"NSBezierPath")]
              || [object isKindOfClass:NSClassFromString(@"UIBezierPath")]) {
     initializeAnyWithTakeOfObject(result.payload.Any, object);
     result.payload.Kind = PlaygroundQuickLook::Tag::BezierPath;
     result.optional.isNone = false;
-    return result;
+    return;
   } else if ([object isKindOfClass:[NSString class]]) {
     result.payload.TextOrURL = String((NSString*)object);
     [object release];
     result.payload.Kind = PlaygroundQuickLook::Tag::Text;
     result.optional.isNone = false;
-    return result;
+    return;
   }
 
   // Return none if we didn't get a suitable object.
   [object release];
   result.optional.isNone = true;
-  return result;
 }
 #endif