pass the self pointer through another pointer indirectly to destroy

Author: ktoso

Samples/SwiftKitSampleApp/src/main/java/com/example/swift/HelloJava2Swift.java

@@ -53,11 +53,13 @@ static void examples() {
 
             var num = instance.makeIntMethod();
 
+            SwiftKit.retain(instance);
+            SwiftKit.retain(instance);
+            SwiftKit.retain(instance);
+
             System.out.println("MySwiftClass.TYPE_MANGLED_NAME = " + MySwiftClass.TYPE_MANGLED_NAME);
            MemorySegment typeMetadata = SwiftValueWitnessTable.fullTypeMetadata(MySwiftClass.TYPE_METADATA.$memorySegment());
            System.out.println("typeMetadata = " + typeMetadata);
-
-           SwiftKit.release(instance);
         } // instance should be deallocated
 
         var num = unsafelyEscaped.makeIntMethod();

SwiftKit/src/main/java/org/swift/swiftkit/SwiftValueLayout.java

@@ -19,6 +19,7 @@
 import java.lang.foreign.ValueLayout;
 
 import static java.lang.foreign.ValueLayout.JAVA_BYTE;
+import static java.lang.foreign.ValueLayout.JAVA_LONG;
 
 /**
  * Similar to {@link java.lang.foreign.ValueLayout} however with some Swift specifics.
@@ -32,9 +33,6 @@ public static long addressByteSize() {
         return ValueLayout.ADDRESS.byteSize();
     }
 
-    public static final AddressLayout SWIFT_POINTER = ValueLayout.ADDRESS
-            .withTargetLayout(MemoryLayout.sequenceLayout(Long.MAX_VALUE, JAVA_BYTE));
-
     /**
      * The value layout for Swift's {@code Int} type, which is a signed type that follows
      * the size of a pointer (aka C's {@code ptrdiff_t}).
@@ -52,4 +50,7 @@ public static long addressByteSize() {
     public static ValueLayout SWIFT_UINT = SWIFT_INT;
 
 
+    public static final AddressLayout SWIFT_POINTER = ValueLayout.ADDRESS
+            .withTargetLayout(MemoryLayout.sequenceLayout(Long.MAX_VALUE, JAVA_BYTE));
+
 }

SwiftKit/src/main/java/org/swift/swiftkit/SwiftValueWitnessTable.java

@@ -16,10 +16,11 @@
 
 import java.lang.foreign.*;
 import java.lang.invoke.MethodHandle;
-import org.swift.swiftkit.util.StringUtils;
 
+import static java.lang.foreign.ValueLayout.ADDRESS;
 import static java.lang.foreign.ValueLayout.JAVA_BYTE;
 import static org.swift.swiftkit.SwiftKit.getSwiftInt;
+import static org.swift.swiftkit.util.StringUtils.hexString;
 
 public abstract class SwiftValueWitnessTable {
 
@@ -162,7 +163,7 @@ public static MemoryLayout layoutOfSwiftType(MemorySegment typeMetadata) {
             $LAYOUT.byteOffset(MemoryLayout.PathElement.groupElement("flags"));
 
     /**
-     * {@snippet lang=C :
+     * {@snippet lang = C:
      * ///void(*destroy)(T *object, witness_t *self);
      * ///
      * /// Given a valid object of this type, destroy it, leaving it as an
@@ -173,23 +174,24 @@ public static MemoryLayout layoutOfSwiftType(MemorySegment typeMetadata) {
      *   Destroy,
      *   VOID_TYPE,
      *   (MUTABLE_VALUE_TYPE, TYPE_TYPE))
-     * }
+     *}
      */
     private static class destroy {
 
         static final long $offset =
                 $LAYOUT.byteOffset(MemoryLayout.PathElement.groupElement("destroy"));
 
         static final FunctionDescriptor DESC = FunctionDescriptor.ofVoid(
-                SwiftValueLayout.SWIFT_POINTER
+                ValueLayout.ADDRESS
+                // SwiftValueLayout.SWIFT_POINTER // should be a "pointer to the self pointer"
 //                , // the object
 //                SwiftValueLayout.SWIFT_POINTER // the type
         );
 
         /**
          * Function pointer for the destroy operation
          */
-        static MemorySegment addr(SwiftAnyType ty, MemorySegment memory) {
+        static MemorySegment addr(SwiftAnyType ty) {
             // Get the value witness table of the type
             final var vwt = SwiftValueWitnessTable.valueWitnessTable(ty.$memorySegment());
 
@@ -198,8 +200,8 @@ static MemorySegment addr(SwiftAnyType ty, MemorySegment memory) {
             return MemorySegment.ofAddress(funcAddress);
         }
 
-        static MethodHandle handle(SwiftAnyType ty, MemorySegment memory) {
-            return Linker.nativeLinker().downcallHandle(addr(ty, memory), DESC);
+        static MethodHandle handle(SwiftAnyType ty) {
+            return Linker.nativeLinker().downcallHandle(addr(ty), DESC);
         }
     }
 
@@ -213,14 +215,32 @@ public static void destroy(SwiftAnyType type, MemorySegment object) {
         System.out.println("Destroy object: " + object);
         System.out.println("Destroy object type: " + type);
 
-        var handle = destroy.handle(type, object);
+        var handle = destroy.handle(type);
         System.out.println("Destroy object handle: " + handle);
 
-        try {
-             handle.invokeExact(object);
-//            handle.invokeExact(object, type.$memorySegment());
+        try (var arena = Arena.ofConfined()) {
+            // we need to make a pointer to the self pointer when calling witness table functions:
+            MemorySegment indirect = arena.allocate(SwiftValueLayout.SWIFT_POINTER);
+
+            // Write the address of as the value of the newly created pointer.
+            // We need to type-safely set the pointer value which may be 64 or 32-bit.
+            if (SwiftValueLayout.SWIFT_INT == ValueLayout.JAVA_LONG) {
+                indirect.set(ValueLayout.JAVA_LONG, /*offset=*/0, object.address());
+            } else {
+                indirect.set(ValueLayout.JAVA_INT, /*offset=*/0, (int) object.address());
+            }
+
+            System.out.println("indirect = " + indirect);
+            if (SwiftValueLayout.SWIFT_INT == ValueLayout.JAVA_LONG) {
+                System.out.println("indirect.get(ValueLayout.JAVA_LONG, 0) = " + hexString(indirect.get(ValueLayout.JAVA_LONG, 0)));
+            } else {
+                System.out.println("indirect.get(ValueLayout.JAVA_INT, 0) = " + hexString(indirect.get(ValueLayout.JAVA_INT, 0)));
+            }
+
+//             handle.invokeExact(object); // NOTE: This does "nothing"
+            handle.invokeExact(indirect);
         } catch (Throwable th) {
-            throw new AssertionError("Failed to destroy '"+type+"' at " + object, th);
+            throw new AssertionError("Failed to destroy '" + type + "' at " + object, th);
         }
     }