Use @RetainedLocalRef to keep J2ObjC from deallocating objects when the fields they were stored in are nulled out.

I put together this CL by looking for `@LazyInit` annotations, but I skipped `ExecutionSequencer` and `SequentialExecutor`, honestly mostly because they are complicated and not directly implicated in the problems we've heard about. I don't know if they're used much under J2ObjC.

RELNOTES=n/a
PiperOrigin-RevId: 689762804

Author: cpovirk

android/guava/src/com/google/common/util/concurrent/AbstractCatchingFuture.java

@@ -27,6 +27,7 @@
 import com.google.common.util.concurrent.internal.InternalFutures;
 import com.google.errorprone.annotations.ForOverride;
 import com.google.errorprone.annotations.concurrent.LazyInit;
+import com.google.j2objc.annotations.RetainedLocalRef;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
 import javax.annotation.CheckForNull;
@@ -80,9 +81,9 @@ abstract class AbstractCatchingFuture<
 
   @Override
   public final void run() {
-    ListenableFuture<? extends V> localInputFuture = inputFuture;
-    Class<X> localExceptionType = exceptionType;
-    F localFallback = fallback;
+    @RetainedLocalRef ListenableFuture<? extends V> localInputFuture = inputFuture;
+    @RetainedLocalRef Class<X> localExceptionType = exceptionType;
+    @RetainedLocalRef F localFallback = fallback;
     if (localInputFuture == null | localExceptionType == null | localFallback == null
         // This check, unlike all the others, is a volatile read
         || isCancelled()) {
@@ -152,9 +153,9 @@ public final void run() {
   @Override
   @CheckForNull
   protected String pendingToString() {
-    ListenableFuture<? extends V> localInputFuture = inputFuture;
-    Class<X> localExceptionType = exceptionType;
-    F localFallback = fallback;
+    @RetainedLocalRef ListenableFuture<? extends V> localInputFuture = inputFuture;
+    @RetainedLocalRef Class<X> localExceptionType = exceptionType;
+    @RetainedLocalRef F localFallback = fallback;
     String superString = super.pendingToString();
     String resultString = "";
     if (localInputFuture != null) {
@@ -184,7 +185,8 @@ protected String pendingToString() {
 
   @Override
   protected final void afterDone() {
-    maybePropagateCancellationTo(inputFuture);
+    @RetainedLocalRef ListenableFuture<? extends V> localInputFuture = inputFuture;
+    maybePropagateCancellationTo(localInputFuture);
     this.inputFuture = null;
     this.exceptionType = null;
     this.fallback = null;

android/guava/src/com/google/common/util/concurrent/AbstractTransformFuture.java

@@ -23,6 +23,7 @@
 import com.google.common.base.Function;
 import com.google.errorprone.annotations.ForOverride;
 import com.google.errorprone.annotations.concurrent.LazyInit;
+import com.google.j2objc.annotations.RetainedLocalRef;
 import java.util.concurrent.CancellationException;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
@@ -73,8 +74,8 @@ abstract class AbstractTransformFuture<
   @Override
   @SuppressWarnings("CatchingUnchecked") // sneaky checked exception
   public final void run() {
-    ListenableFuture<? extends I> localInputFuture = inputFuture;
-    F localFunction = function;
+    @RetainedLocalRef ListenableFuture<? extends I> localInputFuture = inputFuture;
+    @RetainedLocalRef F localFunction = function;
     if (isCancelled() | localInputFuture == null | localFunction == null) {
       return;
     }
@@ -186,16 +187,17 @@ public final void run() {
 
   @Override
   protected final void afterDone() {
-    maybePropagateCancellationTo(inputFuture);
+    @RetainedLocalRef ListenableFuture<? extends I> localInputFuture = inputFuture;
+    maybePropagateCancellationTo(localInputFuture);
     this.inputFuture = null;
     this.function = null;
   }
 
   @Override
   @CheckForNull
   protected String pendingToString() {
-    ListenableFuture<? extends I> localInputFuture = inputFuture;
-    F localFunction = function;
+    @RetainedLocalRef ListenableFuture<? extends I> localInputFuture = inputFuture;
+    @RetainedLocalRef F localFunction = function;
     String superString = super.pendingToString();
     String resultString = "";
     if (localInputFuture != null) {

android/guava/src/com/google/common/util/concurrent/AggregateFuture.java

@@ -28,6 +28,7 @@
 import com.google.errorprone.annotations.ForOverride;
 import com.google.errorprone.annotations.OverridingMethodsMustInvokeSuper;
 import com.google.errorprone.annotations.concurrent.LazyInit;
+import com.google.j2objc.annotations.RetainedLocalRef;
 import java.util.Set;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Future;
@@ -80,7 +81,7 @@ abstract class AggregateFuture<InputT extends @Nullable Object, OutputT extends
   protected final void afterDone() {
     super.afterDone();
 
-    ImmutableCollection<? extends Future<?>> localFutures = futures;
+    @RetainedLocalRef ImmutableCollection<? extends Future<?>> localFutures = futures;
     releaseResources(OUTPUT_FUTURE_DONE); // nulls out `futures`
 
     if (isCancelled() & localFutures != null) {
@@ -98,7 +99,7 @@ protected final void afterDone() {
   @Override
   @CheckForNull
   protected final String pendingToString() {
-    ImmutableCollection<? extends Future<?>> localFutures = futures;
+    @RetainedLocalRef ImmutableCollection<? extends Future<?>> localFutures = futures;
     if (localFutures != null) {
       return "futures=" + localFutures;
     }
@@ -156,22 +157,24 @@ final void init() {
        * Future.get() when we don't need to (specifically, for whenAllComplete().call*()), and it
        * lets all futures share the same listener.
        *
-       * We store `localFutures` inside the listener because `this.futures` might be nulled out by
-       * the time the listener runs for the final future -- at which point we need to check all
-       * inputs for exceptions *if* we're collecting values. If we're not, then the listener doesn't
-       * need access to the futures again, so we can just pass `null`.
+       * We store `localFuturesOrNull` inside the listener because `this.futures` might be nulled
+       * out by the time the listener runs for the final future -- at which point we need to check
+       * all inputs for exceptions *if* we're collecting values. If we're not, then the listener
+       * doesn't need access to the futures again, so we can just pass `null`.
        *
        * TODO(b/112550045): Allocating a single, cheaper listener is (I think) only an optimization.
        * If we make some other optimizations, this one will no longer be necessary. The optimization
        * could actually hurt in some cases, as it forces us to keep all inputs in memory until the
        * final input completes.
        */
-      ImmutableCollection<? extends Future<? extends InputT>> localFutures =
-          collectsValues ? futures : null;
-      Runnable listener = () -> decrementCountAndMaybeComplete(localFutures);
-      for (ListenableFuture<? extends InputT> future : futures) {
+      @RetainedLocalRef
+      ImmutableCollection<? extends ListenableFuture<? extends InputT>> localFutures = futures;
+      ImmutableCollection<? extends Future<? extends InputT>> localFuturesOrNull =
+          collectsValues ? localFutures : null;
+      Runnable listener = () -> decrementCountAndMaybeComplete(localFuturesOrNull);
+      for (ListenableFuture<? extends InputT> future : localFutures) {
         if (future.isDone()) {
-          decrementCountAndMaybeComplete(localFutures);
+          decrementCountAndMaybeComplete(localFuturesOrNull);
         } else {
           future.addListener(listener, directExecutor());
         }

android/guava/src/com/google/common/util/concurrent/CollectionFuture.java

@@ -21,6 +21,7 @@
 import com.google.common.collect.ImmutableCollection;
 import com.google.common.collect.Lists;
 import com.google.errorprone.annotations.concurrent.LazyInit;
+import com.google.j2objc.annotations.RetainedLocalRef;
 import java.util.Collections;
 import java.util.List;
 import javax.annotation.CheckForNull;
@@ -59,15 +60,15 @@ abstract class CollectionFuture<V extends @Nullable Object, C extends @Nullable
 
   @Override
   final void collectOneValue(int index, @ParametricNullness V returnValue) {
-    List<@Nullable Present<V>> localValues = values;
+    @RetainedLocalRef List<@Nullable Present<V>> localValues = values;
     if (localValues != null) {
       localValues.set(index, new Present<>(returnValue));
     }
   }
 
   @Override
   final void handleAllCompleted() {
-    List<@Nullable Present<V>> localValues = values;
+    @RetainedLocalRef List<@Nullable Present<V>> localValues = values;
     if (localValues != null) {
       set(combine(localValues));
     }

android/guava/src/com/google/common/util/concurrent/CombinedFuture.java

@@ -20,6 +20,7 @@
 import com.google.common.annotations.GwtCompatible;
 import com.google.common.collect.ImmutableCollection;
 import com.google.errorprone.annotations.concurrent.LazyInit;
+import com.google.j2objc.annotations.RetainedLocalRef;
 import com.google.j2objc.annotations.WeakOuter;
 import java.util.concurrent.Callable;
 import java.util.concurrent.CancellationException;
@@ -61,7 +62,7 @@ void collectOneValue(int index, @CheckForNull Object returnValue) {}
 
   @Override
   void handleAllCompleted() {
-    CombinedFutureInterruptibleTask<?> localTask = task;
+    @RetainedLocalRef CombinedFutureInterruptibleTask<?> localTask = task;
     if (localTask != null) {
       localTask.execute();
     }
@@ -84,7 +85,7 @@ void releaseResources(ReleaseResourcesReason reason) {
 
   @Override
   protected void interruptTask() {
-    CombinedFutureInterruptibleTask<?> localTask = task;
+    @RetainedLocalRef CombinedFutureInterruptibleTask<?> localTask = task;
     if (localTask != null) {
       localTask.interruptTask();
     }

android/guava/src/com/google/common/util/concurrent/Futures.java

@@ -35,6 +35,7 @@
 import com.google.common.util.concurrent.internal.InternalFutures;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.errorprone.annotations.concurrent.LazyInit;
+import com.google.j2objc.annotations.RetainedLocalRef;
 import java.time.Duration;
 import java.util.Collection;
 import java.util.List;
@@ -811,7 +812,7 @@ private static final class NonCancellationPropagatingFuture<V extends @Nullable
     public void run() {
       // This prevents cancellation from propagating because we don't call setFuture(delegate) until
       // delegate is already done, so calling cancel() on this future won't affect it.
-      ListenableFuture<V> localDelegate = delegate;
+      @RetainedLocalRef ListenableFuture<V> localDelegate = delegate;
       if (localDelegate != null) {
         setFuture(localDelegate);
       }
@@ -820,7 +821,7 @@ public void run() {
     @Override
     @CheckForNull
     protected String pendingToString() {
-      ListenableFuture<V> localDelegate = delegate;
+      @RetainedLocalRef ListenableFuture<V> localDelegate = delegate;
       if (localDelegate != null) {
         return "delegate=[" + localDelegate + "]";
       }

android/guava/src/com/google/common/util/concurrent/TimeoutFuture.java

@@ -21,6 +21,7 @@
 import com.google.common.annotations.J2ktIncompatible;
 import com.google.common.base.Preconditions;
 import com.google.errorprone.annotations.concurrent.LazyInit;
+import com.google.j2objc.annotations.RetainedLocalRef;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Future;
 import java.util.concurrent.ScheduledExecutorService;
@@ -102,7 +103,7 @@ public void run() {
       if (timeoutFuture == null) {
         return;
       }
-      ListenableFuture<V> delegate = timeoutFuture.delegateRef;
+      @RetainedLocalRef ListenableFuture<V> delegate = timeoutFuture.delegateRef;
       if (delegate == null) {
         return;
       }
@@ -124,7 +125,7 @@ public void run() {
         timeoutFuture.setFuture(delegate);
       } else {
         try {
-          ScheduledFuture<?> timer = timeoutFuture.timer;
+          @RetainedLocalRef ScheduledFuture<?> timer = timeoutFuture.timer;
           timeoutFuture.timer = null; // Don't include already elapsed delay in delegate.toString()
           String message = "Timed out";
           // This try-finally block ensures that we complete the timeout future, even if attempting
@@ -162,8 +163,8 @@ public synchronized Throwable fillInStackTrace() {
   @Override
   @CheckForNull
   protected String pendingToString() {
-    ListenableFuture<? extends V> localInputFuture = delegateRef;
-    ScheduledFuture<?> localTimer = timer;
+    @RetainedLocalRef ListenableFuture<? extends V> localInputFuture = delegateRef;
+    @RetainedLocalRef ScheduledFuture<?> localTimer = timer;
     if (localInputFuture != null) {
       String message = "inputFuture=[" + localInputFuture + "]";
       if (localTimer != null) {
@@ -180,9 +181,10 @@ protected String pendingToString() {
 
   @Override
   protected void afterDone() {
-    maybePropagateCancellationTo(delegateRef);
+    @RetainedLocalRef ListenableFuture<? extends V> delegate = delegateRef;
+    maybePropagateCancellationTo(delegate);
 
-    Future<?> localTimer = timer;
+    @RetainedLocalRef Future<?> localTimer = timer;
     // Try to cancel the timer as an optimization.
     // timer may be null if this call to run was by the timer task since there is no happens-before
     // edge between the assignment to timer and an execution of the timer task.

guava/src/com/google/common/util/concurrent/AbstractCatchingFuture.java

@@ -27,6 +27,7 @@
 import com.google.common.util.concurrent.internal.InternalFutures;
 import com.google.errorprone.annotations.ForOverride;
 import com.google.errorprone.annotations.concurrent.LazyInit;
+import com.google.j2objc.annotations.RetainedLocalRef;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
 import javax.annotation.CheckForNull;
@@ -80,9 +81,9 @@ abstract class AbstractCatchingFuture<
 
   @Override
   public final void run() {
-    ListenableFuture<? extends V> localInputFuture = inputFuture;
-    Class<X> localExceptionType = exceptionType;
-    F localFallback = fallback;
+    @RetainedLocalRef ListenableFuture<? extends V> localInputFuture = inputFuture;
+    @RetainedLocalRef Class<X> localExceptionType = exceptionType;
+    @RetainedLocalRef F localFallback = fallback;
     if (localInputFuture == null | localExceptionType == null | localFallback == null
         // This check, unlike all the others, is a volatile read
         || isCancelled()) {
@@ -152,9 +153,9 @@ public final void run() {
   @Override
   @CheckForNull
   protected String pendingToString() {
-    ListenableFuture<? extends V> localInputFuture = inputFuture;
-    Class<X> localExceptionType = exceptionType;
-    F localFallback = fallback;
+    @RetainedLocalRef ListenableFuture<? extends V> localInputFuture = inputFuture;
+    @RetainedLocalRef Class<X> localExceptionType = exceptionType;
+    @RetainedLocalRef F localFallback = fallback;
     String superString = super.pendingToString();
     String resultString = "";
     if (localInputFuture != null) {
@@ -184,7 +185,8 @@ protected String pendingToString() {
 
   @Override
   protected final void afterDone() {
-    maybePropagateCancellationTo(inputFuture);
+    @RetainedLocalRef ListenableFuture<? extends V> localInputFuture = inputFuture;
+    maybePropagateCancellationTo(localInputFuture);
     this.inputFuture = null;
     this.exceptionType = null;
     this.fallback = null;

guava/src/com/google/common/util/concurrent/AbstractTransformFuture.java

@@ -23,6 +23,7 @@
 import com.google.common.base.Function;
 import com.google.errorprone.annotations.ForOverride;
 import com.google.errorprone.annotations.concurrent.LazyInit;
+import com.google.j2objc.annotations.RetainedLocalRef;
 import java.util.concurrent.CancellationException;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
@@ -73,8 +74,8 @@ abstract class AbstractTransformFuture<
   @Override
   @SuppressWarnings("CatchingUnchecked") // sneaky checked exception
   public final void run() {
-    ListenableFuture<? extends I> localInputFuture = inputFuture;
-    F localFunction = function;
+    @RetainedLocalRef ListenableFuture<? extends I> localInputFuture = inputFuture;
+    @RetainedLocalRef F localFunction = function;
     if (isCancelled() | localInputFuture == null | localFunction == null) {
       return;
     }
@@ -186,16 +187,17 @@ public final void run() {
 
   @Override
   protected final void afterDone() {
-    maybePropagateCancellationTo(inputFuture);
+    @RetainedLocalRef ListenableFuture<? extends I> localInputFuture = inputFuture;
+    maybePropagateCancellationTo(localInputFuture);
     this.inputFuture = null;
     this.function = null;
   }
 
   @Override
   @CheckForNull
   protected String pendingToString() {
-    ListenableFuture<? extends I> localInputFuture = inputFuture;
-    F localFunction = function;
+    @RetainedLocalRef ListenableFuture<? extends I> localInputFuture = inputFuture;
+    @RetainedLocalRef F localFunction = function;
     String superString = super.pendingToString();
     String resultString = "";
     if (localInputFuture != null) {