dalvik/src/main/java/dalvik/system/CloseGuard.java - platform/libcore - Git at Google

 /*
  * Copyright (C) 2010 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package dalvik.system;

 import static android.annotation.SystemApi.Client.MODULE_LIBRARIES;

 import android.annotation.SystemApi;
 import android.compat.annotation.UnsupportedAppUsage;

 /**
  * CloseGuard is a mechanism for flagging implicit finalizer cleanup of
  * resources that should have been cleaned up by explicit close
  * methods (aka "explicit termination methods" in Effective Java).
  * <p>
  * A simple example: <pre>   {@code
  *   class Foo {
  *
  *       {@literal @}ReachabilitySensitive
  *       private final CloseGuard guard = CloseGuard.get();
  *
  *       ...
  *
  *       public Foo() {
  *           ...;
  *           guard.open("cleanup");
  *       }
  *
  *       public void cleanup() {
  *          guard.close();
  *          ...;
  *       }
  *
  *       protected void finalize() throws Throwable {
  *           try {
  *               // Note that guard could be null if the constructor threw.
  *               if (guard != null) {
  *                   guard.warnIfOpen();
  *               }
  *               cleanup();
  *           } finally {
  *               super.finalize();
  *           }
  *       }
  *   }
  * }</pre>
  *
  * In usage where the resource to be explicitly cleaned up is
  * allocated after object construction, CloseGuard protection can
  * be deferred. For example: <pre>   {@code
  *   class Bar {
  *
  *       {@literal @}ReachabilitySensitive
  *       private final CloseGuard guard = CloseGuard.get();
  *
  *       ...
  *
  *       public Bar() {
  *           ...;
  *       }
  *
  *       public void connect() {
  *          ...;
  *          guard.open("cleanup");
  *       }
  *
  *       public void cleanup() {
  *          guard.close();
  *          ...;
  *       }
  *
  *       protected void finalize() throws Throwable {
  *           try {
  *               // Note that guard could be null if the constructor threw.
  *               if (guard != null) {
  *                   guard.warnIfOpen();
  *               }
  *               cleanup();
  *           } finally {
  *               super.finalize();
  *           }
  *       }
  *   }
  * }</pre>
  *
  * When used in a constructor, calls to {@code open} should occur at
  * the end of the constructor since an exception that would cause
  * abrupt termination of the constructor will mean that the user will
  * not have a reference to the object to cleanup explicitly. When used
  * in a method, the call to {@code open} should occur just after
  * resource acquisition.
  *
  * The @ReachabilitySensitive annotation ensures that finalize() cannot be
  * called during the explicit call to cleanup(), prior to the guard.close call.
  * There is an extremely small chance that, for code that neglects to call
  * cleanup(), finalize() and thus cleanup() will be called while a method on
  * the object is still active, but the "this" reference is no longer required.
  * If missing cleanup() calls are expected, additional @ReachabilitySensitive
  * annotations or reachabilityFence() calls may be required.
  *
  * @hide
  */
 @SystemApi(client = MODULE_LIBRARIES)
 @libcore.api.IntraCoreApi
 public final class CloseGuard {

     /**
      * True if collection of call-site information (the expensive operation
      * here)  and tracking via a Tracker (see below) are enabled.
      * Enabled by default so we can diagnose issues early in VM startup.
      * Note, however, that Android disables this early in its startup,
      * but enables it with DropBoxing for system apps on debug builds.
      */
     private static volatile boolean stackAndTrackingEnabled = true;

     /**
      * Hook for customizing how CloseGuard issues are reported.
      * Bypassed if stackAndTrackingEnabled was false when open was called.
      */
     private static volatile Reporter reporter = new DefaultReporter();

     /**
      * Hook for customizing how CloseGuard issues are tracked.
      */
     private static volatile Tracker currentTracker = null; // Disabled by default.

     private static final String MESSAGE = "A resource was acquired at attached stack trace but never released. " +
             "See java.io.Closeable for information on avoiding resource leaks.";

     /**
      * Returns a CloseGuard instance. {@code #open(String)} can be used to set
      * up the instance to warn on failure to close.
      *
      * @return {@link CloseGuard} instance.
      *
      * @hide
      */
     @UnsupportedAppUsage(trackingBug=111170242)
     @SystemApi(client = MODULE_LIBRARIES)
     @libcore.api.IntraCoreApi
     public static CloseGuard get() {
         return new CloseGuard();
     }

     /**
      * Enables/disables stack capture and tracking. A call stack is captured
      * during open(), and open/close events are reported to the Tracker, only
      * if enabled is true. If a stack trace was captured, the {@link
      * #getReporter() reporter} is informed of unclosed resources; otherwise a
      * one-line warning is logged.
      *
      * @param enabled whether stack capture and tracking is enabled.
      *
      * @hide
      */
     @UnsupportedAppUsage
     @SystemApi(client = MODULE_LIBRARIES)
     public static void setEnabled(boolean enabled) {
         CloseGuard.stackAndTrackingEnabled = enabled;
     }

     /**
      * True if CloseGuard stack capture and tracking are enabled.
      *
      * @hide
      */
     public static boolean isEnabled() {
         return stackAndTrackingEnabled;
     }

     /**
      * Used to replace default Reporter used to warn of CloseGuard
      * violations when stack tracking is enabled. Must be non-null.
      *
      * @param rep replacement for default Reporter.
      *
      * @hide
      */
     @UnsupportedAppUsage
     @SystemApi(client = MODULE_LIBRARIES)
     public static void setReporter(Reporter rep) {
         if (rep == null) {
             throw new NullPointerException("reporter == null");
         }
         CloseGuard.reporter = rep;
     }

     /**
      * Returns non-null CloseGuard.Reporter.
      *
      * @return CloseGuard's Reporter.
      *
      * @hide
      */
     @SystemApi(client = MODULE_LIBRARIES)
     public static Reporter getReporter() {
         return reporter;
     }

     /**
      * Sets the {@link Tracker} that is notified when resources are allocated and released.
      * The Tracker is invoked only if CloseGuard {@link #isEnabled()} held when {@link #open()}
      * was called. A null argument disables tracking.
      *
      * <p>This is only intended for use by {@code dalvik.system.CloseGuardSupport} class and so
      * MUST NOT be used for any other purposes.
      *
      * @hide
      */
     public static void setTracker(Tracker tracker) {
         currentTracker = tracker;
     }

     /**
      * Returns {@link #setTracker(Tracker) last Tracker that was set}, or null to indicate
      * there is none.
      *
      * <p>This is only intended for use by {@code dalvik.system.CloseGuardSupport} class and so
      * MUST NOT be used for any other purposes.
      *
      * @hide
      */
     public static Tracker getTracker() {
         return currentTracker;
     }

     @UnsupportedAppUsage
     private CloseGuard() {}

     /**
      * {@code open} initializes the instance with a warning that the caller
      * should have explicitly called the {@code closer} method instead of
      * relying on finalization.
      *
      * @param closer non-null name of explicit termination method. Printed by warnIfOpen.
      * @throws NullPointerException if closer is null.
      *
      * @hide
      */
     @UnsupportedAppUsage(trackingBug=111170242)
     @SystemApi(client = MODULE_LIBRARIES)
     @libcore.api.IntraCoreApi
     public void open(String closer) {
         openWithCallSite(closer, null /* callsite */);
     }

     /**
      * Like {@link #open(String)}, but with explicit callsite string being passed in for better
      * performance.
      * <p>
      * This only has better performance than {@link #open(String)} if {@link #isEnabled()} returns {@code true}, which
      * usually shouldn't happen on release builds.
      *
      * @param closer Non-null name of explicit termination method. Printed by warnIfOpen.
      * @param callsite Non-null string uniquely identifying the callsite.
      *
      * @hide
      */
     @SystemApi(client = MODULE_LIBRARIES)
     public void openWithCallSite(String closer, String callsite) {
         // always perform the check for valid API usage...
         if (closer == null) {
             throw new NullPointerException("closer == null");
         }
         // ...but avoid allocating an allocation stack if "disabled"
         if (!stackAndTrackingEnabled) {
             closerNameOrAllocationInfo = closer;
             return;
         }
         // Always record stack trace when tracker installed, which only happens in tests. Otherwise, skip expensive
         // stack trace creation when explicit callsite is passed in for better performance.
         Tracker tracker = currentTracker;
         if (callsite == null || tracker != null) {
             String message = "Explicit termination method '" + closer + "' not called";
             Throwable stack = new Throwable(message);
             closerNameOrAllocationInfo = stack;
             if (tracker != null) {
                 tracker.open(stack);
             }
         } else {
             closerNameOrAllocationInfo = callsite;
         }
     }

     // We keep either an allocation stack containing the closer String or, when
     // in disabled state, just the closer String.
     // We keep them in a single field only to minimize overhead.
     private Object /* String or Throwable */ closerNameOrAllocationInfo;

     /**
      * Marks this CloseGuard instance as closed to avoid warnings on
      * finalization.
      *
      * @hide
      */
     @UnsupportedAppUsage
     @SystemApi(client = MODULE_LIBRARIES)
     @libcore.api.IntraCoreApi
     public void close() {
         Tracker tracker = currentTracker;
         if (tracker != null && closerNameOrAllocationInfo instanceof Throwable) {
             // Invoke tracker on close only if we invoked it on open. Tracker may have changed.
             tracker.close((Throwable) closerNameOrAllocationInfo);
         }
         closerNameOrAllocationInfo = null;
     }

     /**
      * Logs a warning if the caller did not properly cleanup by calling an
      * explicit close method before finalization. If CloseGuard was enabled
      * when the CloseGuard was created, passes the stacktrace associated with
      * the allocation to the current reporter. If it was not enabled, it just
      * directly logs a brief message.
      *
      * @hide
      */
     @UnsupportedAppUsage(trackingBug=111170242)
     @SystemApi(client = MODULE_LIBRARIES)
     @libcore.api.IntraCoreApi
     public void warnIfOpen() {
         if (closerNameOrAllocationInfo != null) {
             if (closerNameOrAllocationInfo instanceof Throwable) {
                 reporter.report(MESSAGE, (Throwable) closerNameOrAllocationInfo);
             } else if (stackAndTrackingEnabled) {
                 reporter.report(MESSAGE + " Callsite: " + closerNameOrAllocationInfo);
             } else {
                 System.logW("A resource failed to call "
                         + (String) closerNameOrAllocationInfo + ". ");
             }
         }
     }


     /**
      * Interface to allow customization of tracking behaviour.
      *
      * <p>This is only intended for use by {@code dalvik.system.CloseGuardSupport} class and so
      * MUST NOT be used for any other purposes.
      *
      * @hide
      */
     public interface Tracker {
         void open(Throwable allocationSite);
         void close(Throwable allocationSite);
     }

     /**
      * Interface to allow customization of reporting behavior.
      * @hide
      */
     @SystemApi(client = MODULE_LIBRARIES)
     public interface Reporter {
         /**
          *
          * @hide
          */
         @UnsupportedAppUsage
         @SystemApi(client = MODULE_LIBRARIES)
         void report(String message, Throwable allocationSite);

         /**
          *
          * @hide
          */
         @SystemApi(client = MODULE_LIBRARIES)
         default void report(String message) {}
     }

     /**
      * Default Reporter which reports CloseGuard violations to the log.
      */
     private static final class DefaultReporter implements Reporter {
         @UnsupportedAppUsage
         private DefaultReporter() {}

         @Override public void report (String message, Throwable allocationSite) {
             System.logW(message, allocationSite);
         }

         @Override
         public void report(String message) {
             System.logW(message);
         }
     }
 }
	/*
	* Copyright (C) 2010 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package dalvik.system;

	import static android.annotation.SystemApi.Client.MODULE_LIBRARIES;

	import android.annotation.SystemApi;
	import android.compat.annotation.UnsupportedAppUsage;

	/**
	* CloseGuard is a mechanism for flagging implicit finalizer cleanup of
	* resources that should have been cleaned up by explicit close
	* methods (aka "explicit termination methods" in Effective Java).
	* <p>
	* A simple example: <pre> {@code
	* class Foo {
	*
	* {@literal @}ReachabilitySensitive
	* private final CloseGuard guard = CloseGuard.get();
	*
	* ...
	*
	* public Foo() {
	* ...;
	* guard.open("cleanup");
	* }
	*
	* public void cleanup() {
	* guard.close();
	* ...;
	* }
	*
	* protected void finalize() throws Throwable {
	* try {
	* // Note that guard could be null if the constructor threw.
	* if (guard != null) {
	* guard.warnIfOpen();
	* }
	* cleanup();
	* } finally {
	* super.finalize();
	* }
	* }
	* }
	* }</pre>
	*
	* In usage where the resource to be explicitly cleaned up is
	* allocated after object construction, CloseGuard protection can
	* be deferred. For example: <pre> {@code
	* class Bar {
	*
	* {@literal @}ReachabilitySensitive
	* private final CloseGuard guard = CloseGuard.get();
	*
	* ...
	*
	* public Bar() {
	* ...;
	* }
	*
	* public void connect() {
	* ...;
	* guard.open("cleanup");
	* }
	*
	* public void cleanup() {
	* guard.close();
	* ...;
	* }
	*
	* protected void finalize() throws Throwable {
	* try {
	* // Note that guard could be null if the constructor threw.
	* if (guard != null) {
	* guard.warnIfOpen();
	* }
	* cleanup();
	* } finally {
	* super.finalize();
	* }
	* }
	* }
	* }</pre>
	*
	* When used in a constructor, calls to {@code open} should occur at
	* the end of the constructor since an exception that would cause
	* abrupt termination of the constructor will mean that the user will
	* not have a reference to the object to cleanup explicitly. When used
	* in a method, the call to {@code open} should occur just after
	* resource acquisition.
	*
	* The @ReachabilitySensitive annotation ensures that finalize() cannot be
	* called during the explicit call to cleanup(), prior to the guard.close call.
	* There is an extremely small chance that, for code that neglects to call
	* cleanup(), finalize() and thus cleanup() will be called while a method on
	* the object is still active, but the "this" reference is no longer required.
	* If missing cleanup() calls are expected, additional @ReachabilitySensitive
	* annotations or reachabilityFence() calls may be required.
	*
	* @hide
	*/
	@SystemApi(client = MODULE_LIBRARIES)
	@libcore.api.IntraCoreApi
	public final class CloseGuard {

	/**
	* True if collection of call-site information (the expensive operation
	* here) and tracking via a Tracker (see below) are enabled.
	* Enabled by default so we can diagnose issues early in VM startup.
	* Note, however, that Android disables this early in its startup,
	* but enables it with DropBoxing for system apps on debug builds.
	*/
	private static volatile boolean stackAndTrackingEnabled = true;

	/**
	* Hook for customizing how CloseGuard issues are reported.
	* Bypassed if stackAndTrackingEnabled was false when open was called.
	*/
	private static volatile Reporter reporter = new DefaultReporter();

	/**
	* Hook for customizing how CloseGuard issues are tracked.
	*/
	private static volatile Tracker currentTracker = null; // Disabled by default.

	private static final String MESSAGE = "A resource was acquired at attached stack trace but never released. " +
	"See java.io.Closeable for information on avoiding resource leaks.";

	/**
	* Returns a CloseGuard instance. {@code #open(String)} can be used to set
	* up the instance to warn on failure to close.
	*
	* @return {@link CloseGuard} instance.
	*
	* @hide
	*/
	@UnsupportedAppUsage(trackingBug=111170242)
	@SystemApi(client = MODULE_LIBRARIES)
	@libcore.api.IntraCoreApi
	public static CloseGuard get() {
	return new CloseGuard();
	}

	/**
	* Enables/disables stack capture and tracking. A call stack is captured
	* during open(), and open/close events are reported to the Tracker, only
	* if enabled is true. If a stack trace was captured, the {@link
	* #getReporter() reporter} is informed of unclosed resources; otherwise a
	* one-line warning is logged.
	*
	* @param enabled whether stack capture and tracking is enabled.
	*
	* @hide
	*/
	@UnsupportedAppUsage
	@SystemApi(client = MODULE_LIBRARIES)
	public static void setEnabled(boolean enabled) {
	CloseGuard.stackAndTrackingEnabled = enabled;
	}

	/**
	* True if CloseGuard stack capture and tracking are enabled.
	*
	* @hide
	*/
	public static boolean isEnabled() {
	return stackAndTrackingEnabled;
	}

	/**
	* Used to replace default Reporter used to warn of CloseGuard
	* violations when stack tracking is enabled. Must be non-null.
	*
	* @param rep replacement for default Reporter.
	*
	* @hide
	*/
	@UnsupportedAppUsage
	@SystemApi(client = MODULE_LIBRARIES)
	public static void setReporter(Reporter rep) {
	if (rep == null) {
	throw new NullPointerException("reporter == null");
	}
	CloseGuard.reporter = rep;
	}

	/**
	* Returns non-null CloseGuard.Reporter.
	*
	* @return CloseGuard's Reporter.
	*
	* @hide
	*/
	@SystemApi(client = MODULE_LIBRARIES)
	public static Reporter getReporter() {
	return reporter;
	}

	/**
	* Sets the {@link Tracker} that is notified when resources are allocated and released.
	* The Tracker is invoked only if CloseGuard {@link #isEnabled()} held when {@link #open()}
	* was called. A null argument disables tracking.
	*
	* <p>This is only intended for use by {@code dalvik.system.CloseGuardSupport} class and so
	* MUST NOT be used for any other purposes.
	*
	* @hide
	*/
	public static void setTracker(Tracker tracker) {
	currentTracker = tracker;
	}

	/**
	* Returns {@link #setTracker(Tracker) last Tracker that was set}, or null to indicate
	* there is none.
	*
	* <p>This is only intended for use by {@code dalvik.system.CloseGuardSupport} class and so
	* MUST NOT be used for any other purposes.
	*
	* @hide
	*/
	public static Tracker getTracker() {
	return currentTracker;
	}

	@UnsupportedAppUsage
	private CloseGuard() {}

	/**
	* {@code open} initializes the instance with a warning that the caller
	* should have explicitly called the {@code closer} method instead of
	* relying on finalization.
	*
	* @param closer non-null name of explicit termination method. Printed by warnIfOpen.
	* @throws NullPointerException if closer is null.
	*
	* @hide
	*/
	@UnsupportedAppUsage(trackingBug=111170242)
	@SystemApi(client = MODULE_LIBRARIES)
	@libcore.api.IntraCoreApi
	public void open(String closer) {
	openWithCallSite(closer, null /* callsite */);
	}

	/**
	* Like {@link #open(String)}, but with explicit callsite string being passed in for better
	* performance.
	* <p>
	* This only has better performance than {@link #open(String)} if {@link #isEnabled()} returns {@code true}, which
	* usually shouldn't happen on release builds.
	*
	* @param closer Non-null name of explicit termination method. Printed by warnIfOpen.
	* @param callsite Non-null string uniquely identifying the callsite.
	*
	* @hide
	*/
	@SystemApi(client = MODULE_LIBRARIES)
	public void openWithCallSite(String closer, String callsite) {
	// always perform the check for valid API usage...
	if (closer == null) {
	throw new NullPointerException("closer == null");
	}
	// ...but avoid allocating an allocation stack if "disabled"
	if (!stackAndTrackingEnabled) {
	closerNameOrAllocationInfo = closer;
	return;
	}
	// Always record stack trace when tracker installed, which only happens in tests. Otherwise, skip expensive
	// stack trace creation when explicit callsite is passed in for better performance.
	Tracker tracker = currentTracker;
	if (callsite == null \|\| tracker != null) {
	String message = "Explicit termination method '" + closer + "' not called";
	Throwable stack = new Throwable(message);
	closerNameOrAllocationInfo = stack;
	if (tracker != null) {
	tracker.open(stack);
	}
	} else {
	closerNameOrAllocationInfo = callsite;
	}
	}

	// We keep either an allocation stack containing the closer String or, when
	// in disabled state, just the closer String.
	// We keep them in a single field only to minimize overhead.
	private Object /* String or Throwable */ closerNameOrAllocationInfo;

	/**
	* Marks this CloseGuard instance as closed to avoid warnings on
	* finalization.
	*
	* @hide
	*/
	@UnsupportedAppUsage
	@SystemApi(client = MODULE_LIBRARIES)
	@libcore.api.IntraCoreApi
	public void close() {
	Tracker tracker = currentTracker;
	if (tracker != null && closerNameOrAllocationInfo instanceof Throwable) {
	// Invoke tracker on close only if we invoked it on open. Tracker may have changed.
	tracker.close((Throwable) closerNameOrAllocationInfo);
	}
	closerNameOrAllocationInfo = null;
	}

	/**
	* Logs a warning if the caller did not properly cleanup by calling an
	* explicit close method before finalization. If CloseGuard was enabled
	* when the CloseGuard was created, passes the stacktrace associated with
	* the allocation to the current reporter. If it was not enabled, it just
	* directly logs a brief message.
	*
	* @hide
	*/
	@UnsupportedAppUsage(trackingBug=111170242)
	@SystemApi(client = MODULE_LIBRARIES)
	@libcore.api.IntraCoreApi
	public void warnIfOpen() {
	if (closerNameOrAllocationInfo != null) {
	if (closerNameOrAllocationInfo instanceof Throwable) {
	reporter.report(MESSAGE, (Throwable) closerNameOrAllocationInfo);
	} else if (stackAndTrackingEnabled) {
	reporter.report(MESSAGE + " Callsite: " + closerNameOrAllocationInfo);
	} else {
	System.logW("A resource failed to call "
	+ (String) closerNameOrAllocationInfo + ". ");
	}
	}
	}


	/**
	* Interface to allow customization of tracking behaviour.
	*
	* <p>This is only intended for use by {@code dalvik.system.CloseGuardSupport} class and so
	* MUST NOT be used for any other purposes.
	*
	* @hide
	*/
	public interface Tracker {
	void open(Throwable allocationSite);
	void close(Throwable allocationSite);
	}

	/**
	* Interface to allow customization of reporting behavior.
	* @hide
	*/
	@SystemApi(client = MODULE_LIBRARIES)
	public interface Reporter {
	/**
	*
	* @hide
	*/
	@UnsupportedAppUsage
	@SystemApi(client = MODULE_LIBRARIES)
	void report(String message, Throwable allocationSite);

	/**
	*
	* @hide
	*/
	@SystemApi(client = MODULE_LIBRARIES)
	default void report(String message) {}
	}

	/**
	* Default Reporter which reports CloseGuard violations to the log.
	*/
	private static final class DefaultReporter implements Reporter {
	@UnsupportedAppUsage
	private DefaultReporter() {}

	@Override public void report (String message, Throwable allocationSite) {
	System.logW(message, allocationSite);
	}

	@Override
	public void report(String message) {
	System.logW(message);
	}
	}
	}