Remove copy constructors and assignment operators from RelativeDirectPointerImpl.

There were places were RelativeDirectPointers were copied using bitwise copies, which is semantically wrong. This patch makes sure it cannot happen anymore.

Author: swiftix

include/swift/Basic/RelativePointer.h

@@ -276,6 +276,15 @@ class RelativeDirectPointerImpl {
   /// RelativePointers should appear in statically-generated metadata. They
   /// shouldn't be constructed or copied.
   RelativeDirectPointerImpl() = delete;
+  /// RelativePointers should appear in statically-generated metadata. They
+  /// shouldn't be constructed or copied.
+  RelativeDirectPointerImpl(RelativeDirectPointerImpl &&) = delete;
+  RelativeDirectPointerImpl(const RelativeDirectPointerImpl &) = delete;
+  RelativeDirectPointerImpl &operator=(RelativeDirectPointerImpl &&)
+    = delete;
+  RelativeDirectPointerImpl &operator=(const RelativeDirectPointerImpl &)
+    = delete;
+
 
 public:
   using ValueTy = T;
@@ -305,12 +314,6 @@ class RelativeDirectPointerImpl {
       : detail::measureRelativeOffset<Offset>(absolute, this);
     return *this;
   }
-  
-  // Can copy-construct by recalculating the relative offset at the new
-  // position.
-  RelativeDirectPointerImpl(const RelativeDirectPointerImpl &p) {
-    *this = p.get();
-  }
 
   PointerTy get() const & {
     // Check for null.

include/swift/Runtime/Metadata.h

@@ -25,6 +25,7 @@
 #include <string>
 #include <type_traits>
 #include <utility>
+#include <string.h>
 #include "swift/Runtime/Config.h"
 #include "swift/ABI/MetadataValues.h"
 #include "swift/ABI/System.h"
@@ -1089,6 +1090,13 @@ template <typename Runtime> struct TargetOpaqueMetadata;
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Winvalid-offsetof"
 
+extern uint64_t RelativeDirectPointerNullPtr;
+
+#define RelativeDirectPointerNullPtrRef                                        \
+  *reinterpret_cast<ConstTargetFarRelativeDirectPointer<                       \
+      Runtime, TargetNominalTypeDescriptor, /*nullable*/ true> *>(             \
+      &RelativeDirectPointerNullPtr)
+
 /// The common structure of all type metadata.
 template <typename Runtime>
 struct TargetMetadata {
@@ -1221,16 +1229,17 @@ struct TargetMetadata {
 
   /// Get the nominal type descriptor if this metadata describes a nominal type,
   /// or return null if it does not.
-  ConstTargetFarRelativeDirectPointer<Runtime, TargetNominalTypeDescriptor,
-                                      /*nullable*/ true>
+  const ConstTargetFarRelativeDirectPointer<Runtime,
+                                            TargetNominalTypeDescriptor,
+                                            /*nullable*/ true> &
   getNominalTypeDescriptor() const {
     switch (getKind()) {
     case MetadataKind::Class: {
       const auto cls = static_cast<const TargetClassMetadata<Runtime> *>(this);
       if (!cls->isTypeMetadata())
-        return 0;
+        return RelativeDirectPointerNullPtrRef;
       if (cls->isArtificialSubclass())
-        return 0;
+        return RelativeDirectPointerNullPtrRef;
       return cls->getDescription();
     }
     case MetadataKind::Struct:
@@ -1248,7 +1257,7 @@ struct TargetMetadata {
     case MetadataKind::HeapLocalVariable:
     case MetadataKind::HeapGenericLocalVariable:
     case MetadataKind::ErrorObject:
-      return 0;
+      return RelativeDirectPointerNullPtrRef;
     }
   }
 
@@ -1559,6 +1568,11 @@ struct TargetClassMetadata : public TargetHeapMetadata<Runtime> {
       Reserved(0), ClassSize(classSize), ClassAddressPoint(classAddressPoint),
       Description(nullptr), IVarDestroyer(ivarDestroyer) {}
 
+  TargetClassMetadata(const TargetClassMetadata& other): Description(other.getDescription().get()) {
+    memcpy(this, &other, sizeof(*this));
+    setDescription(other.getDescription().get());
+  }
+
   /// The metadata for the superclass.  This is null for the root class.
   ConstTargetMetadataPointer<Runtime, swift::TargetClassMetadata> SuperClass;
 
@@ -1634,8 +1648,10 @@ struct TargetClassMetadata : public TargetHeapMetadata<Runtime> {
   //   - "tabulated" virtual methods
 
 public:
-  ConstTargetFarRelativeDirectPointer<Runtime, TargetNominalTypeDescriptor,
-  /*nullable*/ true> getDescription() const {
+  const ConstTargetFarRelativeDirectPointer<Runtime,
+                                            TargetNominalTypeDescriptor,
+                                            /*nullable*/ true> &
+  getDescription() const {
     assert(isTypeMetadata());
     assert(!isArtificialSubclass());
     return Description;

stdlib/public/runtime/Metadata.cpp

@@ -1576,7 +1576,7 @@ static ClassMetadata *_swift_initializeSuperclass(ClassMetadata *theClass,
   auto *classWords = reinterpret_cast<uintptr_t *>(theClass);
   auto *superWords = reinterpret_cast<const uintptr_t *>(theSuperclass);
   while (ancestor && ancestor->isTypeMetadata()) {
-    auto description = ancestor->getDescription();
+    auto &description = ancestor->getDescription();
     auto &genericParams = description->GenericParams;
 
     // Copy the parent type.
@@ -2486,7 +2486,7 @@ swift::swift_getForeignTypeMetadata(ForeignTypeMetadata *nonUnique) {
 
 template<> const GenericMetadata *
 Metadata::getGenericPattern() const {
-  auto ntd = getNominalTypeDescriptor();
+  auto &ntd = getNominalTypeDescriptor();
   if (!ntd)
     return nullptr;
   return ntd->getGenericMetadataPattern();
@@ -2713,3 +2713,5 @@ swift::swift_getGenericWitnessTable(GenericWitnessTable *genericTable,
 
   return entry->get(genericTable);
 }
+
+uint64_t swift::RelativeDirectPointerNullPtr = 0;

stdlib/public/runtime/ProtocolConformance.cpp

@@ -65,7 +65,7 @@ template<> void ProtocolConformanceRecord::dump() const {
       printf("%s direct type ",
              kind == TypeMetadataRecordKind::UniqueDirectType
              ? "unique" : "nonunique");
-      if (auto ntd = getDirectType()->getNominalTypeDescriptor()) {
+      if (auto &ntd = getDirectType()->getNominalTypeDescriptor()) {
         printf("%s", ntd->Name.get());
       } else {
         printf("<structural type>");