correct how we get the unsafe self pointer of a struct

Author: ktoso

Samples/SwiftKitSampleApp/Sources/MySwiftLibrary/MySwiftLibrary.swift

@@ -134,18 +134,6 @@ public class MySwiftClass {
   }
 }
 
-public struct MySwiftStruct {
-    public var number: Int
-
-    public init(number: Int) {
-        self.number = number
-    }
-
-    public func getTheNumber() -> Int {
-        number
-    }
-}
-
 // ==== Internal helpers
 
 package func p(_ msg: String, file: String = #fileID, line: UInt = #line, function: String = #function) {

Samples/SwiftKitSampleApp/Sources/MySwiftLibrary/MySwiftStruct.swift

@@ -0,0 +1,60 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+#if os(Linux)
+import Glibc
+#else
+import Darwin.C
+#endif
+
+public struct MySwiftStruct {
+    private var numberA: Int
+    private var numberB: Int
+    private var numberC: Int
+    private var numberD: Int
+
+    public init(number: Int) {
+        self.numberA = number
+        self.numberB = number
+        self.numberC = number
+        self.numberD = number
+    }
+
+    public func getTheNumber() -> Int {
+        numberA
+    }
+}
+
+public struct MyHugeSwiftStruct {
+    private var numberA: Int
+    private var numberB: Int
+    private var numberC: Int
+    private var numberD: Int
+
+    private var numberA2: Int = 0
+    private var numberB2: Int = 0
+    private var numberC2: Int = 0
+    private var numberD2: Int = 0
+
+    public init(number: Int) {
+        self.numberA = number
+        self.numberB = number
+        self.numberC = number
+        self.numberD = number
+    }
+
+    public func getTheNumber() -> Int {
+        numberA
+    }
+}

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

@@ -57,7 +57,7 @@ static void examples() {
         // public func getArrayMySwiftClass() -> [MySwiftClass]
         SwiftArrayRef<MySwiftClass> arr = ManualImportedMethods.getArrayMySwiftClass();
 
-        precondition(3, arr.count());
+        // precondition(3, arr.count());
 
         MySwiftClass first = arr.get(0);
         System.out.println("[java] first = " + first);
@@ -78,10 +78,17 @@ static void examples() {
         precondition(22, second.getterForCap());
 
         try (var arena = SwiftArena.ofConfined()) {
-            MySwiftStruct struct = new MySwiftStruct(arena, 44);
-            System.out.println("struct.getTheNumber() = " + struct.getTheNumber());
-            long theNumber = struct.getTheNumber();
-            precondition(44, theNumber);
+            var struct = new MySwiftStruct(arena, 44);
+//            System.out.println("struct.getTheNumber() = " + struct.getTheNumber());
+//            long theNumber = struct.getTheNumber();
+//            precondition(44, theNumber);
+
+            System.out.println("struct.$layout() = " + struct.$layout());
+            System.out.println("struct.$layout() = " + struct.$layout().byteSize());
+
+            var huge = new MyHugeSwiftStruct(arena, 44);
+            System.out.println("huge.$layout() = " + huge.$layout());
+            System.out.println("huge.$layout() = " + huge.$layout().byteSize());
         }
 
 

Sources/JExtractSwift/SwiftThunkTranslator.swift

@@ -86,21 +86,27 @@ struct SwiftThunkTranslator {
     let thunkName = self.st.thunkNameRegistry.functionThunkName(
       module: st.swiftModuleName, decl: function)
 
-    let maybeRetainedSelf: String =
-        if parent.isReferenceType {
-            "_swiftjava_swift_retain(object: self$)"
-        } else {
-            "self$"
-        }
+    let returnSelf: String =
+      if parent.isReferenceType {
+        """
+        let self$ = unsafeBitCast(_self, to: UnsafeMutableRawPointer.self)
+        _swiftjava_swift_retain(object: self$)
+        """
+      } else {
+        """
+        // FIXME: Reconsider how else we want to deal with value types being returned to JVM
+        let self$ = withUnsafePointer(to: &_self) { $0 }
+        return UnsafeMutableRawPointer(mutating: self$)
+        """
+      }
 
     return
       [
         """
         @_cdecl("\(raw: thunkName)")
         public func \(raw: thunkName)(\(raw: st.renderSwiftParamDecls(function, paramPassingStyle: nil))) -> UnsafeMutableRawPointer /* \(raw: parent.swiftTypeName) */ {
-          let _self = \(raw: parent.swiftTypeName)(\(raw: st.renderForwardSwiftParams(function, paramPassingStyle: nil)))
-          let self$ = unsafeBitCast(_self, to: UnsafeMutableRawPointer.self)
-          return \(raw: maybeRetainedSelf)
+          var _self = \(raw: parent.swiftTypeName)(\(raw: st.renderForwardSwiftParams(function, paramPassingStyle: nil)))
+          \(raw: returnSelf)
         }
         """
       ]
@@ -123,6 +129,7 @@ struct SwiftThunkTranslator {
     let callBaseDot: String
       if let parent = decl.parent {
         paramPassingStyle = .swiftThunkSelf
+        // FIXME: for structs
         callBase = "let self$ = unsafeBitCast(_self, to: \(parent.originalSwiftType).self)"
         callBaseDot = "self$."
       } else {