Correct reference counting in init thunk

Author: ktoso

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

@@ -24,16 +24,16 @@
 import org.swift.swiftkit.SwiftKit;
 import org.swift.swiftkit.SwiftValueWitnessTable;
 
+import java.util.Arrays;
+
 public class HelloJava2Swift {
 
     public static void main(String[] args) {
         boolean traceDowncalls = Boolean.getBoolean("jextract.trace.downcalls");
         System.out.println("Property: jextract.trace.downcalls = " + traceDowncalls);
 
-        System.out.print("java.library.path = \n");
-        for (var path : SwiftKit.getJavaLibraryPath().split(":")) {
-            System.out.println("  " + path);
-        }
+        System.out.print("Property: java.library.path = \n");
+        System.out.println(SwiftKit.getJavaLibraryPath());
 
         examples();
 
@@ -44,13 +44,17 @@ static void examples() {
 
         MySwiftLibrary.globalTakeInt(1337);
 
-        MySwiftClass obj = new MySwiftClass(2222, 7777);
+        // Example of using an arena; MyClass.deinit is run at end of scope
+        try (var arena = SwiftArena.ofConfined()) {
+            MySwiftClass obj = new MySwiftClass(arena, 2222, 7777);
 
-//        SwiftKit.retain(obj.$memorySegment());
-//        System.out.println("[java] obj ref count = " + SwiftKit.retainCount(obj.$memorySegment()));
+            // just checking retains/releases work
+            SwiftKit.retain(obj.$memorySegment());
+            SwiftKit.release(obj.$memorySegment());
 
-        obj.voidMethod();
-//        obj.takeIntMethod(42);
+            obj.voidMethod();
+            obj.takeIntMethod(42);
+        }
 
         System.out.println("DONE.");
     }

Sources/JExtractSwift/Swift2JavaTranslator+Printing.swift

@@ -112,6 +112,15 @@ extension Swift2JavaTranslator {
   public func printSwiftThunkSources(_ printer: inout CodePrinter, ty: ImportedNominalType) throws {
     let stt = SwiftThunkTranslator(self)
 
+    printer.print(
+        """
+        // Generated by swift-java
+
+        import SwiftKitSwift
+
+        """
+    )
+
     for thunk in stt.renderThunks(forType: ty) {
       printer.print("\(thunk)")
       printer.print("")

Sources/JExtractSwift/SwiftThunkTranslator.swift

@@ -72,7 +72,7 @@ struct SwiftThunkTranslator {
       """
       @_cdecl("\(raw: funcName)")
       public func \(raw: funcName)() -> UnsafeMutableRawPointer /* Any.Type */ {
-        unsafeBitCast(\(raw: nominal.swiftTypeName).self, to: UnsafeMutableRawPointer.self)
+        return unsafeBitCast(\(raw: nominal.swiftTypeName).self, to: UnsafeMutableRawPointer.self)
       }
       """
   }
@@ -90,9 +90,9 @@ struct SwiftThunkTranslator {
         """
         @_cdecl("\(raw: thunkName)")
         public func \(raw: thunkName)(\(raw: st.renderSwiftParamDecls(function, paramPassingStyle: nil))) -> UnsafeMutableRawPointer /* \(raw: parent.swiftTypeName) */ {
-          print("[swift] init class \(raw: parent.swiftTypeName)")
           let _self = \(raw: parent.swiftTypeName)(\(raw: st.renderForwardSwiftParams(function, paramPassingStyle: nil)))
-          return unsafeBitCast(_self, to: UnsafeMutableRawPointer.self)
+          let self$ = unsafeBitCast(_self, to: UnsafeMutableRawPointer.self)
+          return _swiftjava_swift_retain(object: self$)
         }
         """
       ]
@@ -128,7 +128,7 @@ struct SwiftThunkTranslator {
         """
         @_cdecl("\(raw: thunkName)")
         public func \(raw: thunkName)(\(raw: st.renderSwiftParamDecls(decl, paramPassingStyle: paramPassingStyle))) \(raw: returnArrowTy) {
-          \(raw: callBaseDot)\(raw: decl.baseIdentifier)(\(raw: st.renderForwardSwiftParams(decl, paramPassingStyle: paramPassingStyle)))
+          return \(raw: callBaseDot)\(raw: decl.baseIdentifier)(\(raw: st.renderForwardSwiftParams(decl, paramPassingStyle: paramPassingStyle)))
         }
         """
       ]

Sources/SwiftKitSwift/SwiftKit.swift

@@ -12,12 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// This is a "plain Swift" file containing various types of declarations,
-// that is exported to Java by using the `jextract-swift` tool.
-//
-// No annotations are necessary on the Swift side to perform the export.
-
-// FIXME: this is a workaround until we can pass String to Swift directly
 @_silgen_name("getTypeByStringByteArray")
 public func getTypeByStringByteArray(_ name: UnsafePointer<UInt8>) -> Any.Type? {
   let string = String(cString: name)
@@ -26,9 +20,25 @@ public func getTypeByStringByteArray(_ name: UnsafePointer<UInt8>) -> Any.Type?
   return type
 }
 
-//// FIXME: this is internal in stdlib, it would make things easier here
-//@_silgen_name("swift_stdlib_getTypeByMangledNameUntrusted")
-//public func _getTypeByMangledNameUntrusted(
-//  _ name: UnsafePointer<UInt8>,
-//  _ nameLength: UInt)
-//  -> Any.Type?
+@_silgen_name("swift_retain")
+public func _swiftjava_swift_retain(object: UnsafeMutableRawPointer) -> UnsafeMutableRawPointer
+
+@_silgen_name("swift_release")
+public func _swiftjava_swift_release(object: UnsafeMutableRawPointer) -> UnsafeMutableRawPointer
+
+@_silgen_name("swift_retainCount")
+public func _swiftjava_swift_retainCount(object: UnsafeMutableRawPointer) -> Int
+
+@_silgen_name("swift_isUniquelyReferenced")
+public func _swiftjava_swift_isUniquelyReferenced(object: UnsafeMutableRawPointer) -> Bool
+
+
+ @_alwaysEmitIntoClient @_transparent
+ internal func _swiftjava_withHeapObject<R>(
+   of object: AnyObject,
+   _ body: (UnsafeMutableRawPointer) -> R
+ ) -> R {
+   defer { _fixLifetime(object) }
+   let unmanaged = Unmanaged.passUnretained(object)
+   return body(unmanaged.toOpaque())
+ }