Runtime: Use metadata accessor functions in Reflection.mm and make sure they're public

Correct behavior with resilience requires calling accessors instead
of using the metadata symbols directly.

For some reason this file gets linked in with SwiftRuntimeTests too,
so make the types @_versioned in the stdlib.

Fixes <rdar://problem/29213794>.

Author: slavapestov

stdlib/public/core/ReflectionLegacy.swift

@@ -118,6 +118,7 @@ public struct _MagicMirrorData {
   }
 }
 
+@_versioned
 struct _OpaqueMirror : _Mirror {
   let data: _MagicMirrorData
 
@@ -147,6 +148,7 @@ func _getTupleCount(_: _MagicMirrorData) -> Int
 @_silgen_name("swift_TupleMirror_subscript")
 func _getTupleChild<T>(_: Int, _: _MagicMirrorData) -> (T, _Mirror)
 
+@_versioned
 internal struct _TupleMirror : _Mirror {
   let data: _MagicMirrorData
 
@@ -170,6 +172,7 @@ func _getStructCount(_: _MagicMirrorData) -> Int
 @_silgen_name("swift_StructMirror_subscript")
 func _getStructChild<T>(_: Int, _: _MagicMirrorData) -> (T, _Mirror)
 
+@_versioned
 struct _StructMirror : _Mirror {
   let data: _MagicMirrorData
 
@@ -200,6 +203,7 @@ func _getEnumChild<T>(_: Int, _: _MagicMirrorData) -> (T, _Mirror)
 func _swift_EnumMirror_caseName(
     _ data: _MagicMirrorData) -> UnsafePointer<CChar>
 
+@_versioned
 struct _EnumMirror : _Mirror {
   let data: _MagicMirrorData
 
@@ -282,6 +286,7 @@ func _getClassPlaygroundQuickLook(_ object: AnyObject) -> PlaygroundQuickLook? {
 
 #endif
 
+@_versioned
 struct _ClassMirror : _Mirror {
   let data: _MagicMirrorData
 
@@ -310,6 +315,7 @@ struct _ClassMirror : _Mirror {
   var disposition: _MirrorDisposition { return .`class` }
 }
 
+@_versioned
 struct _ClassSuperMirror : _Mirror {
   let data: _MagicMirrorData
 
@@ -333,6 +339,7 @@ struct _ClassSuperMirror : _Mirror {
   var disposition: _MirrorDisposition { return .`class` }
 }
 
+@_versioned
 struct _MetatypeMirror : _Mirror {
   let data: _MagicMirrorData
 

stdlib/public/runtime/Reflection.mm

@@ -943,47 +943,49 @@ void swift_ObjCMirror_subscript(String *outString,
 
 // Addresses of the type metadata and Mirror witness tables for the primitive
 // mirrors.
-extern "C" const Metadata OpaqueMirrorMetadata
-  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMVs13_OpaqueMirror));
+typedef const Metadata *(*MetadataFn)();
+
+extern "C" Metadata *OpaqueMirrorMetadata()
+  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMaVs13_OpaqueMirror));
 extern "C" const MirrorWitnessTable OpaqueMirrorWitnessTable
   __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TWPVs13_OpaqueMirrors7_Mirrors));
-extern "C" const Metadata TupleMirrorMetadata
-  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMVs12_TupleMirror));
+extern "C" Metadata *TupleMirrorMetadata()
+  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMaVs12_TupleMirror));
 extern "C" const MirrorWitnessTable TupleMirrorWitnessTable
   __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TWPVs12_TupleMirrors7_Mirrors));
 
-extern "C" const Metadata StructMirrorMetadata
-  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMVs13_StructMirror));
+extern "C" Metadata *StructMirrorMetadata()
+  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMaVs13_StructMirror));
 extern "C" const MirrorWitnessTable StructMirrorWitnessTable
   __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TWPVs13_StructMirrors7_Mirrors));
 
-extern "C" const Metadata EnumMirrorMetadata
-  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMVs11_EnumMirror));
+extern "C" Metadata *EnumMirrorMetadata()
+  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMaVs11_EnumMirror));
 extern "C" const MirrorWitnessTable EnumMirrorWitnessTable
   __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TWPVs11_EnumMirrors7_Mirrors));
 
-extern "C" const Metadata ClassMirrorMetadata
-  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMVs12_ClassMirror));
+extern "C" Metadata *ClassMirrorMetadata()
+  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMaVs12_ClassMirror));
 extern "C" const MirrorWitnessTable ClassMirrorWitnessTable
   __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TWPVs12_ClassMirrors7_Mirrors));
 
-extern "C" const Metadata ClassSuperMirrorMetadata
-  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMVs17_ClassSuperMirror));
+extern "C" Metadata *ClassSuperMirrorMetadata()
+  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMaVs17_ClassSuperMirror));
 extern "C" const MirrorWitnessTable ClassSuperMirrorWitnessTable
   __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TWPVs17_ClassSuperMirrors7_Mirrors));
 
-extern "C" const Metadata MetatypeMirrorMetadata
-  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMVs15_MetatypeMirror));
+extern "C" Metadata *MetatypeMirrorMetadata()
+  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMaVs15_MetatypeMirror));
 extern "C" const MirrorWitnessTable MetatypeMirrorWitnessTable
   __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TWPVs15_MetatypeMirrors7_Mirrors));
 
 #if SWIFT_OBJC_INTEROP
-extern "C" const Metadata ObjCMirrorMetadata
-  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMVs11_ObjCMirror));
+extern "C" Metadata *ObjCMirrorMetadata()
+  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMaVs11_ObjCMirror));
 extern "C" const MirrorWitnessTable ObjCMirrorWitnessTable
   __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TWPVs11_ObjCMirrors7_Mirrors));
-extern "C" const Metadata ObjCSuperMirrorMetadata
-  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMVs16_ObjCSuperMirror));
+extern "C" Metadata *ObjCSuperMirrorMetadata()
+  __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TMaVs16_ObjCSuperMirror));
 extern "C" const MirrorWitnessTable ObjCSuperMirrorWitnessTable
   __asm__(SWIFT_QUOTED_SYMBOL_NAME(_TWPVs16_ObjCSuperMirrors7_Mirrors));
 #endif
@@ -1004,7 +1006,7 @@ static Mirror getMirrorForSuperclass(const ClassMetadata *sup,
   Mirror resultBuf;
   MagicMirror *result = ::new (&resultBuf) MagicMirror;
 
-  result->Self = &ClassSuperMirrorMetadata;
+  result->Self = ClassSuperMirrorMetadata();
   result->MirrorWitness = &ClassSuperMirrorWitnessTable;
   result->Data.Owner = owner;
   result->Data.Type = sup;
@@ -1023,7 +1025,7 @@ static Mirror ObjC_getMirrorForSuperclass(Class sup,
   Mirror resultBuf;
   MagicMirror *result = ::new (&resultBuf) MagicMirror;
 
-  result->Self = &ObjCSuperMirrorMetadata;
+  result->Self = ObjCSuperMirrorMetadata();
   result->MirrorWitness = &ObjCSuperMirrorWitnessTable;
   result->Data.Owner = owner;
   result->Data.Type = reinterpret_cast<ClassMetadata*>(sup);
@@ -1050,12 +1052,12 @@ static Mirror ObjC_getMirrorForSuperclass(Class sup,
 #if SWIFT_OBJC_INTEROP
   // If this is a pure ObjC class, reflect it using ObjC's runtime facilities.
   if (!isa->isTypeMetadata())
-    return {isa, &ObjCMirrorMetadata, &ObjCMirrorWitnessTable};
+    return {isa, ObjCMirrorMetadata(), &ObjCMirrorWitnessTable};
 #endif
 
   // Otherwise, use the native Swift facilities.
   return std::make_tuple(
-      isa, &ClassMirrorMetadata, &ClassMirrorWitnessTable);
+      isa, ClassMirrorMetadata(), &ClassMirrorWitnessTable);
 }
 
 /// Get the magic mirror witnesses appropriate to a particular type.
@@ -1064,16 +1066,16 @@ static Mirror ObjC_getMirrorForSuperclass(Class sup,
   switch (T->getKind()) {
   case MetadataKind::Tuple:
     return std::make_tuple(
-        T, &TupleMirrorMetadata, &TupleMirrorWitnessTable);
+        T, TupleMirrorMetadata(), &TupleMirrorWitnessTable);
 
   case MetadataKind::Struct:
     return std::make_tuple(
-        T, &StructMirrorMetadata, &StructMirrorWitnessTable);
+        T, StructMirrorMetadata(), &StructMirrorWitnessTable);
 
   case MetadataKind::Enum:
   case MetadataKind::Optional:
     return std::make_tuple(
-        T, &EnumMirrorMetadata, &EnumMirrorWitnessTable);
+        T, EnumMirrorMetadata(), &EnumMirrorWitnessTable);
 
   case MetadataKind::ObjCClassWrapper:
   case MetadataKind::ForeignClass:
@@ -1083,7 +1085,7 @@ static Mirror ObjC_getMirrorForSuperclass(Class sup,
 
   case MetadataKind::Metatype:
   case MetadataKind::ExistentialMetatype: {
-    return std::make_tuple(T, &MetatypeMirrorMetadata,
+    return std::make_tuple(T, MetatypeMirrorMetadata(),
                            &MetatypeMirrorWitnessTable);
   }
 
@@ -1110,7 +1112,7 @@ static Mirror ObjC_getMirrorForSuperclass(Class sup,
   case MetadataKind::Function:
   case MetadataKind::Existential:
     return std::make_tuple(
-        T, &OpaqueMirrorMetadata, &OpaqueMirrorWitnessTable);
+        T, OpaqueMirrorMetadata(), &OpaqueMirrorWitnessTable);
 
   // Types can't have these kinds.
   case MetadataKind::HeapLocalVariable: