Fix UncaughtExceptionHandlerIntegration Memory Leak

CHANGELOG.md

@@ -10,6 +10,7 @@
 
 - Fix Frame measurements in app start transactions ([#3382](https://github.com/getsentry/sentry-java/pull/3382))
 - Fix timing metric value different from span duration ([#3368](https://github.com/getsentry/sentry-java/pull/3368))
+- Fix UncaughtExceptionHandlerIntegration Memory Leak ([#3398](https://github.com/getsentry/sentry-java/pull/3398))
 
 ## 7.8.0
 

sentry/api/sentry.api

@@ -2978,7 +2978,7 @@ public final class io/sentry/TypeCheckHint {
 public final class io/sentry/UncaughtExceptionHandlerIntegration : io/sentry/Integration, java/io/Closeable, java/lang/Thread$UncaughtExceptionHandler {
 	public fun <init> ()V
 	public fun close ()V
-	public final fun register (Lio/sentry/IHub;Lio/sentry/SentryOptions;)V
+	public fun register (Lio/sentry/IHub;Lio/sentry/SentryOptions;)V
 	public fun uncaughtException (Ljava/lang/Thread;Ljava/lang/Throwable;)V
 }
 

sentry/src/main/java/io/sentry/UncaughtExceptionHandlerIntegration.java

@@ -43,7 +43,7 @@ public UncaughtExceptionHandlerIntegration() {
   }
 
   @Override
-  public final void register(final @NotNull IHub hub, final @NotNull SentryOptions options) {
+  public void register(final @NotNull IHub hub, final @NotNull SentryOptions options) {
     if (registered) {
       options
           .getLogger()
@@ -75,7 +75,16 @@ public final void register(final @NotNull IHub hub, final @NotNull SentryOptions
                 "default UncaughtExceptionHandler class='"
                     + currentHandler.getClass().getName()
                     + "'");
-        defaultExceptionHandler = currentHandler;
+
+        if (currentHandler instanceof UncaughtExceptionHandlerIntegration) {
+          final UncaughtExceptionHandlerIntegration currentHandlerIntegration =
+              (UncaughtExceptionHandlerIntegration) currentHandler;
+          defaultExceptionHandler = currentHandlerIntegration.defaultExceptionHandler;
+        } else {
+          defaultExceptionHandler = currentHandler;
+        }
+
+        //        defaultExceptionHandler = currentHandler;
       }
 
       threadAdapter.setDefaultUncaughtExceptionHandler(this);

sentry/src/test/java/io/sentry/UncaughtExceptionHandlerIntegrationTest.kt

@@ -7,6 +7,7 @@ import io.sentry.hints.EventDropReason.MULTITHREADED_DEDUPLICATION
 import io.sentry.protocol.SentryId
 import io.sentry.util.HintUtils
 import org.mockito.kotlin.any
+import org.mockito.kotlin.anyOrNull
 import org.mockito.kotlin.argThat
 import org.mockito.kotlin.argWhere
 import org.mockito.kotlin.argumentCaptor
@@ -19,6 +20,7 @@ import java.io.PrintStream
 import java.nio.file.Files
 import kotlin.concurrent.thread
 import kotlin.test.Test
+import kotlin.test.assertEquals
 import kotlin.test.assertNotNull
 import kotlin.test.assertTrue
 
@@ -291,4 +293,54 @@ class UncaughtExceptionHandlerIntegrationTest {
             }
         )
     }
+
+    @Test
+    fun `multiple registrations do not cause the build-up of a tree of UncaughtExceptionHandlerIntegrations`() {
+        var currentDefaultHandler: Thread.UncaughtExceptionHandler? = null
+
+        val handler = mock<UncaughtExceptionHandler>()
+        whenever(handler.defaultUncaughtExceptionHandler).thenAnswer { currentDefaultHandler }
+
+        whenever(handler.setDefaultUncaughtExceptionHandler(anyOrNull<Thread.UncaughtExceptionHandler>())).then {
+            currentDefaultHandler = it.getArgument(0)
+            null
+        }
+
+        val integration1 = UncaughtExceptionHandlerIntegration(handler)
+        integration1.register(fixture.hub, fixture.options)
+
+        val integration2 = UncaughtExceptionHandlerIntegration(handler)
+        integration2.register(fixture.hub, fixture.options)
+
+        assertEquals(currentDefaultHandler, integration2)
+        integration2.close()
+
+        assertEquals(null, currentDefaultHandler)
+    }
+
+    @Test
+    fun `multiple registrations do not cause the build-up of a tree of UncaughtExceptionHandlerIntegrations, reset to inital`() {
+        val initialUncaughtExceptionHandler = Thread.UncaughtExceptionHandler { _, _ -> }
+
+        var currentDefaultHandler: Thread.UncaughtExceptionHandler? = initialUncaughtExceptionHandler
+
+        val handler = mock<UncaughtExceptionHandler>()
+        whenever(handler.defaultUncaughtExceptionHandler).thenAnswer { currentDefaultHandler }
+
+        whenever(handler.setDefaultUncaughtExceptionHandler(anyOrNull<Thread.UncaughtExceptionHandler>())).then {
+            currentDefaultHandler = it.getArgument(0)
+            null
+        }
+
+        val integration1 = UncaughtExceptionHandlerIntegration(handler)
+        integration1.register(fixture.hub, fixture.options)
+
+        val integration2 = UncaughtExceptionHandlerIntegration(handler)
+        integration2.register(fixture.hub, fixture.options)
+
+        assertEquals(currentDefaultHandler, integration2)
+        integration2.close()
+
+        assertEquals(initialUncaughtExceptionHandler, currentDefaultHandler)
+    }
 }