fix: stop leaking a JNI global ref per ArrayBuffer passed to Java

test-app/app/src/main/assets/app/tests/byte-buffer-test.js

@@ -80,4 +80,31 @@ describe("Tests mapped ByteBuffer conversion", function () {
 		}
 		expect(exceptionCaught).toBe(true);
 	});
-});
+});
+
+describe("Tests JNI references of ArrayBuffers passed to Java", function () {
+	// ART aborts the process once its JNI global reference table holds 51200
+	// entries. Each ArrayBuffer or typed array crossing to Java for the first
+	// time used to take a global reference that was never deleted, so these
+	// loops cross more distinct buffers than the table can hold.
+	var MORE_THAN_THE_GLOBAL_REF_TABLE = 60000;
+
+	it("should not keep a global reference per buffer passed as a method argument", function () {
+		var holder = new com.tns.tests.ByteBufferHolder();
+		for (var i = 0; i < MORE_THAN_THE_GLOBAL_REF_TABLE; i++) {
+			var buffer = i % 2 ? new ArrayBuffer(1) : new Uint8Array(1);
+			new Uint8Array(buffer.buffer || buffer)[0] = i & 0x7f;
+			holder.hold(buffer);
+		}
+		expect(holder.get(0)).toBe((MORE_THAN_THE_GLOBAL_REF_TABLE - 1) & 0x7f);
+	});
+
+	it("should not keep a global reference per buffer stored in a Java array", function () {
+		var array = Array.create(java.nio.ByteBuffer, 1);
+		for (var i = 0; i < MORE_THAN_THE_GLOBAL_REF_TABLE; i++) {
+			array[0] = new ArrayBuffer(1);
+		}
+		// reaching here without the runtime aborting is the real assertion
+		expect(array[0]).toBeTruthy();
+	});
+});

test-app/runtime/src/main/cpp/JsArgConverter.cpp

@@ -331,8 +331,11 @@ bool JsArgConverter::ConvertArg(const Local<Value> &arg, int index) {
                         buffer = directBuffer;
                     }
 
-                    buffer = env.NewGlobalRef(buffer);
-
+                    // The buffer needs no global ref of its own: GetOrCreateObjectId keeps
+                    // it strongly reachable from Java until the JS object is collected.
+                    // One taken here would never be deleted, pinning the buffer (and, via
+                    // JSObjectFinalizer, its ArrayBuffer) and filling the JNI global
+                    // reference table.
                     int id = objectManager->GetOrCreateObjectId(buffer);
                     auto clazz = env.GetObjectClass(buffer);
 

test-app/runtime/src/main/cpp/JsArgToArrayConverter.cpp

@@ -334,8 +334,11 @@ bool JsArgToArrayConverter::ConvertArg(Local<Context> context, const Local<Value
                         buffer = directBuffer;
                     }
 
-                    buffer = env.NewGlobalRef(buffer);
-
+                    // The buffer needs no global ref of its own: GetOrCreateObjectId keeps
+                    // it strongly reachable from Java until the JS object is collected.
+                    // One taken here would never be deleted, pinning the buffer (and, via
+                    // JSObjectFinalizer, its ArrayBuffer) and filling the JNI global
+                    // reference table.
                     int id = objectManager->GetOrCreateObjectId(buffer);
                     auto clazz = env.GetObjectClass(buffer);
                     objectManager->Link(jsObj, id, clazz);