COMMENT ONLY change to add some warnings about ParcelFileDescriptor

behavior with Parcel.writeValue().

Change-Id: If55fcce29559379855735ff5297cf4f46d5d6be6
Bug: 2847738

Author: egnor

core/java/android/os/Parcel.java

@@ -437,6 +437,12 @@ public final void writeStrongInterface(IInterface val) {
     /**
      * Write a FileDescriptor into the parcel at the current dataPosition(),
      * growing dataCapacity() if needed.
+     *
+     * <p class="caution">The file descriptor will not be closed, which may
+     * result in file descriptor leaks when objects are returned from Binder
+     * calls.  Use {@link ParcelFileDescriptor#writeToParcel} instead, which
+     * accepts contextual flags and will close the original file descriptor
+     * if {@link Parcelable#PARCELABLE_WRITE_RETURN_VALUE} is set.</p>
      */
     public final native void writeFileDescriptor(FileDescriptor val);
 
@@ -1000,7 +1006,7 @@ public final <T extends Parcelable> void writeTypedArray(T[] val,
     /**
      * Flatten a generic object in to a parcel.  The given Object value may
      * currently be one of the following types:
-     * 
+     *
      * <ul>
      * <li> null
      * <li> String
@@ -1023,7 +1029,7 @@ public final <T extends Parcelable> void writeTypedArray(T[] val,
      * <li> Parcelable[]
      * <li> CharSequence (as supported by {@link TextUtils#writeToParcel}).
      * <li> List (as supported by {@link #writeList}).
-     * <li> {@link SparseArray} (as supported by {@link #writeSparseArray}).
+     * <li> {@link SparseArray} (as supported by {@link #writeSparseArray(SparseArray)}).
      * <li> {@link IBinder}
      * <li> Any object that implements Serializable (but see
      *      {@link #writeSerializable} for caveats).  Note that all of the
@@ -1032,6 +1038,13 @@ public final <T extends Parcelable> void writeTypedArray(T[] val,
      *      approach is much less efficient and should be avoided whenever
      *      possible.
      * </ul>
+     *
+     * <p class="caution">{@link Parcelable} objects are written with
+     * {@link Parcelable#writeToParcel} using contextual flags of 0.  When
+     * serializing objects containing {@link ParcelFileDescriptor}s,
+     * this may result in file descriptor leaks when they are returned from
+     * Binder calls (where {@link Parcelable#PARCELABLE_WRITE_RETURN_VALUE}
+     * should be used).</p>
      */
     public final void writeValue(Object v) {
         if (v == null) {
@@ -1120,7 +1133,7 @@ public final void writeValue(Object v) {
     /**
      * Flatten the name of the class of the Parcelable and its contents
      * into the parcel.
-     * 
+     *
      * @param p The Parcelable object to be written.
      * @param parcelableFlags Contextual flags as per
      * {@link Parcelable#writeToParcel(Parcel, int) Parcelable.writeToParcel()}.

core/java/android/os/ParcelFileDescriptor.java

@@ -250,6 +250,11 @@ public int describeContents() {
         return Parcelable.CONTENTS_FILE_DESCRIPTOR;
     }
 
+    /**
+     * {@inheritDoc}
+     * If {@link Parcelable#PARCELABLE_WRITE_RETURN_VALUE} is set in flags,
+     * the file descriptor will be closed after a copy is written to the Parcel.
+     */
     public void writeToParcel(Parcel out, int flags) {
         out.writeFileDescriptor(mFileDescriptor);
         if ((flags&PARCELABLE_WRITE_RETURN_VALUE) != 0 && !mClosed) {