Cleanup local refs

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+NativeTranslation.swift

@@ -1293,6 +1293,7 @@ extension JNISwift2JavaGenerator {
           """
           let class$ = environment.interface.GetObjectClass(environment, \(placeholder))
           let methodID$ = environment.interface.GetMethodID(environment, class$, "apply", "\(methodSignature.mangledName)")!
+          environment.interface.DeleteLocalRef(environment, class$)
           let arguments$: [jvalue] = [\(arguments.joined(separator: ", "))]
           """
         )

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+SwiftThunkPrinting.swift

@@ -171,6 +171,19 @@ extension JNISwift2JavaGenerator {
     }
 
     printer.printBraceBlock(function.swiftDecl.signatureString) { printer in
+      // Push a local JNI frame so refs created during this upcall are freed on exit.
+      // When called from a Swift async context (e.g. cooperative thread pool) there is
+      // no enclosing JNI frame, so refs would otherwise accumulate indefinitely. When
+      // called from a Java-initiated native call there is already a frame, but pushing
+      // a sub-frame still frees refs earlier and prevents overflow within a single call.
+      let paramCount = function.originalFunctionSignature.parameters.count
+      printer.print(
+        """
+        let environment$ = try! JavaVirtualMachine.shared().environment()
+        environment$.interface.PushLocalFrame(environment$, \(paramCount * 2 + 4))
+        defer { environment$.interface.PopLocalFrame(environment$, nil) }
+        """
+      )
       var upcallArguments = zip(
         function.originalFunctionSignature.parameters,
         function.parameterConversions

Sources/JavaKit/Helpers/_JNIMethodIDCache.swift

@@ -46,6 +46,8 @@ public final class _JNIMethodIDCache: Sendable {
         fatalError("Method \(method.signature) with signature \(method.signature) not found in class \(className)")
       }
     }
+    // clazz is still needed by GetMethodID above; delete the local ref only after reduce completes.
+    environment.interface.DeleteLocalRef(environment, clazz)
   }
 
   public subscript(_ method: Method) -> jmethodID? {

Sources/SwiftJava/Exceptions/ExceptionHandling.swift

@@ -54,6 +54,7 @@ extension JNIEnvironment {
       }
       return
     }
+    defer { self.interface.DeleteLocalRef(self, exceptionClass) }
 
     _ = interface.ThrowNew(self, exceptionClass, javaException.message ?? "")
   }

Sources/SwiftJava/JavaObject+MethodCalls.swift

@@ -108,6 +108,7 @@ extension AnyJavaObject {
     let thisClass = try environment.translatingJNIExceptions {
       environment.interface.GetObjectClass(environment, javaThis)
     }!
+    defer { environment.interface.DeleteLocalRef(environment, thisClass) }
 
     return try environment.translatingJNIExceptions {
       try Self.javaMethodLookup(
@@ -131,6 +132,7 @@ extension AnyJavaObject {
     let thisClass = try environment.translatingJNIExceptions {
       environment.interface.GetObjectClass(environment, javaThis)
     }!
+    defer { environment.interface.DeleteLocalRef(environment, thisClass) }
 
     return try environment.translatingJNIExceptions {
       try Self.javaMethodLookup(
@@ -153,7 +155,11 @@ extension AnyJavaObject {
   ) throws -> Result {
     // Retrieve the method that performs this call, then package the values and
     // call it.
+    // Size the frame to 1 ref per argument (strings/objects each need 1;
+    // primitives need 0, so this slightly over-estimates) plus 1 for the result ref.
     let jniMethod = Result.jniMethodCall(in: environment)
+    environment.interface.PushLocalFrame(environment, Int32(countArgs(repeat each args) + 2))
+    defer { environment.interface.PopLocalFrame(environment, nil) }
     let jniArgs = getJValues(repeat each args, in: environment)
     let jniResult = try environment.translatingJNIExceptions {
       jniMethod(environment, this, method, jniArgs)
@@ -219,7 +225,10 @@ extension AnyJavaObject {
   ) throws {
     // Retrieve the method that performs this call, then package the arguments
     // and call it.
+    // Size the frame to 1 ref per argument; no result ref needed for void calls.
     let jniMethod = environment.interface.CallVoidMethodA!
+    environment.interface.PushLocalFrame(environment, Int32(countArgs(repeat each args) + 1))
+    defer { environment.interface.PopLocalFrame(environment, nil) }
     let jniArgs = getJValues(repeat each args, in: environment)
     try environment.translatingJNIExceptions {
       jniMethod(environment, this, method, jniArgs)
@@ -269,11 +278,16 @@ extension AnyJavaObject {
         in: environment
       )
 
-      // Retrieve the constructor, then map the arguments and call it.
+      // Retrieve the constructor, then map the arguments and call it. Use a local
+      // frame so args are freed; promote the new object to the outer frame
+      // via PopLocalFrame(result).
+      // Size the frame to 1 ref per argument; result is promoted via PopLocalFrame(newObj).
+      environment.interface.PushLocalFrame(environment, Int32(countArgs(repeat each arguments) + 1))
       let jniArgs = getJValues(repeat each arguments, in: environment)
-      return try environment.translatingJNIExceptions {
+      let newObj = try environment.translatingJNIExceptions {
         environment.interface.NewObjectA!(environment, thisClass, methodID, jniArgs)
       }!
+      return environment.interface.PopLocalFrame(environment, newObj)!
     }
   }
 
@@ -285,6 +299,7 @@ extension AnyJavaObject {
 
     // Retrieve the Java class instance from the object.
     let thisClass = environment.interface.GetObjectClass(environment, this)!
+    defer { environment.interface.DeleteLocalRef(environment, thisClass) }
 
     return environment.interface.GetFieldID(environment, thisClass, fieldName, FieldType.jniMangling)
   }
@@ -306,6 +321,9 @@ extension AnyJavaObject {
 
       let fieldID = getJNIFieldID(fieldName, fieldType: fieldType)!
       let jniMethod = FieldType.jniFieldSet(in: environment)
+      // Frame of 2: 1 for the field value's local ref, 1 buffer.
+      environment.interface.PushLocalFrame(environment, 2)
+      defer { environment.interface.PopLocalFrame(environment, nil) }
       jniMethod(environment, javaThis, fieldID, newValue.getJNIValue(in: environment))
     }
   }
@@ -337,8 +355,12 @@ extension JavaClass {
       )
     }!
 
-    // Retrieve the method that performs this call, then
+    // Retrieve the method that performs this call, then package the values and
+    // call it.
+    // Size the frame to 1 ref per argument plus 1 for the result ref.
     let jniMethod = Result.jniStaticMethodCall(in: environment)
+    environment.interface.PushLocalFrame(environment, Int32(countArgs(repeat each arguments) + 2))
+    defer { environment.interface.PopLocalFrame(environment, nil) }
     let jniArgs = getJValues(repeat each arguments, in: environment)
     let jniResult = try environment.translatingJNIExceptions {
       jniMethod(environment, thisClass, methodID, jniArgs)
@@ -371,8 +393,11 @@ extension JavaClass {
       )
     }!
 
-    // Retrieve the method that performs this call, then
+    // Retrieve the method that performs this call
+    // Size the frame to 1 ref per argument; no result ref needed for void calls.
     let jniMethod = environment.interface.CallStaticVoidMethodA
+    environment.interface.PushLocalFrame(environment, Int32(countArgs(repeat each arguments) + 1))
+    defer { environment.interface.PopLocalFrame(environment, nil) }
     let jniArgs = getJValues(repeat each arguments, in: environment)
     try environment.translatingJNIExceptions {
       jniMethod!(environment, thisClass, methodID, jniArgs)

Sources/SwiftJava/JavaObjectHolder.swift

@@ -26,6 +26,12 @@ public final class JavaObjectHolder {
   public init(object: jobject, environment: JNIEnvironment) {
     self.object = environment.interface.NewGlobalRef(environment, object)
     self.environment = environment
+
+    // If we are taking over a local ref, let's delete that.
+    let refType = environment.interface.GetObjectRefType(environment, object)
+    if refType == JNILocalRefType {
+      environment.interface.DeleteLocalRef(environment, object)
+    }
   }
 
   /// Forget this Java object, meaning that it is no longer used from anywhere

Sources/SwiftJavaRuntimeSupport/_JNIMethodIDCache.swift

@@ -63,6 +63,7 @@ public final class _JNIMethodIDCache: Sendable {
     let clazz: jobject
     if let jniClass = environment.interface.FindClass(environment, className) {
       clazz = environment.interface.NewGlobalRef(environment, jniClass)!
+      environment.interface.DeleteLocalRef(environment, jniClass)
       self.javaObjectHolder = nil
     } else {
       // Clear any ClassNotFound exceptions from FindClass

Tests/JExtractSwiftTests/JNI/JNIClosureTests.swift

@@ -70,6 +70,7 @@ struct JNIClosureTests {
           SwiftModule.emptyClosure(closure: {
             let class$ = environment.interface.GetObjectClass(environment, closure)
             let methodID$ = environment.interface.GetMethodID(environment, class$, "apply", "()V")!
+            environment.interface.DeleteLocalRef(environment, class$)
             let arguments$: [jvalue] = []
             environment.interface.CallVoidMethodA(environment, closure, methodID$, arguments$)
           }
@@ -127,6 +128,7 @@ struct JNIClosureTests {
           SwiftModule.closureWithArgumentsAndReturn(closure: { _0, _1 in
             let class$ = environment.interface.GetObjectClass(environment, closure)
             let methodID$ = environment.interface.GetMethodID(environment, class$, "apply", "(JZ)J")!
+            environment.interface.DeleteLocalRef(environment, class$)
             let arguments$: [jvalue] = [_0.getJValue(in: environment), _1.getJValue(in: environment)]
             return Int64(fromJNI: environment.interface.CallLongMethodA(environment, closure, methodID$, arguments$), in: environment)
           }

Tests/JExtractSwiftTests/JNI/JNIProtocolTests.swift

@@ -315,9 +315,15 @@ struct JNIProtocolTests {
         """
         extension SwiftJavaSomeProtocolWrapper {
           public func method() {
+            let environment$ = try! JavaVirtualMachine.shared().environment()
+            environment$.interface.PushLocalFrame(environment$, 4)
+            defer { environment$.interface.PopLocalFrame(environment$, nil) }
             _javaSomeProtocolInterface.method()
           }
           public func withObject(c: SomeClass) -> SomeClass {
+            let environment$ = try! JavaVirtualMachine.shared().environment()
+            environment$.interface.PushLocalFrame(environment$, 6)
+            defer { environment$.interface.PopLocalFrame(environment$, nil) }
             let cClass = try! JavaClass<JavaSomeClass>(environment: JavaVirtualMachine.shared().environment())
             let cPointer = UnsafeMutablePointer<SomeClass>.allocate(capacity: 1)
             cPointer.initialize(to: c)