fix RefBase so it retains binary-compatibility with gingerbread

Bug: 4595257
Change-Id: I0d5e10f497e3f39868bff58f6ded510c38b44b12

include/utils/RefBase.h

@@ -116,17 +116,23 @@ public:
 
     typedef RefBase basetype;
 
+    // used to override the RefBase destruction.
+    class Destroyer {
+        friend class RefBase;
+    public:
+        virtual ~Destroyer();
+    private:
+        virtual void destroy(RefBase const* base) = 0;
+    };
+
+    // Make sure to never acquire a strong reference from this function. The
+    // same restrictions than for destructors apply.
+    void setDestroyer(Destroyer* destroyer);
+
 protected:
                             RefBase();
     virtual                 ~RefBase();
 
-    // called when the last reference goes away. this is responsible for
-    // calling the destructor. The default implementation just does
-    // "delete this;".
-    // Make sure to never acquire a strong reference from this function. The
-    // same restrictions than for destructors apply.
-    virtual void            destroy() const;
-
     //! Flags for extendObjectLifetime()
     enum {
         OBJECT_LIFETIME_WEAK    = 0x0001,

libs/utils/RefBase.cpp

@@ -49,6 +49,11 @@ namespace android {
 
 // ---------------------------------------------------------------------------
 
+RefBase::Destroyer::~Destroyer() {
+}
+
+// ---------------------------------------------------------------------------
+
 class RefBase::weakref_impl : public RefBase::weakref_type
 {
 public:
@@ -56,7 +61,7 @@ public:
     volatile int32_t    mWeak;
     RefBase* const      mBase;
     volatile int32_t    mFlags;
-
+    Destroyer*          mDestroyer;
 
 #if !DEBUG_REFS
 
@@ -65,6 +70,7 @@ public:
         , mWeak(0)
         , mBase(base)
         , mFlags(0)
+        , mDestroyer(0)
     {
     }
 
@@ -345,10 +351,6 @@ void RefBase::incStrong(const void* id) const
     const_cast<RefBase*>(this)->onFirstRef();
 }
 
-void RefBase::destroy() const {
-    delete this;
-}
-
 void RefBase::decStrong(const void* id) const
 {
     weakref_impl* const refs = mRefs;
@@ -361,7 +363,11 @@ void RefBase::decStrong(const void* id) const
     if (c == 1) {
         const_cast<RefBase*>(this)->onLastStrongRef(id);
         if ((refs->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
-            destroy();
+            if (refs->mDestroyer) {
+                refs->mDestroyer->destroy(this);
+            } else {
+                delete this;
+            }
         }
     }
     refs->decWeak(id);
@@ -394,7 +400,9 @@ int32_t RefBase::getStrongCount() const
     return mRefs->mStrong;
 }
 
-
+void RefBase::setDestroyer(RefBase::Destroyer* destroyer) {
+    mRefs->mDestroyer = destroyer;
+}
 
 RefBase* RefBase::weakref_type::refBase() const
 {
@@ -420,7 +428,11 @@ void RefBase::weakref_type::decWeak(const void* id)
     if ((impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
         if (impl->mStrong == INITIAL_STRONG_VALUE) {
             if (impl->mBase) {
-                impl->mBase->destroy();
+                if (impl->mDestroyer) {
+                    impl->mDestroyer->destroy(impl->mBase);
+                } else {
+                    delete impl->mBase;
+                }
             }
         } else {
             // LOGV("Freeing refs %p of old RefBase %p\n", this, impl->mBase);
@@ -430,7 +442,11 @@ void RefBase::weakref_type::decWeak(const void* id)
         impl->mBase->onLastWeakRef(id);
         if ((impl->mFlags&OBJECT_LIFETIME_FOREVER) != OBJECT_LIFETIME_FOREVER) {
             if (impl->mBase) {
-                impl->mBase->destroy();
+                if (impl->mDestroyer) {
+                    impl->mDestroyer->destroy(impl->mBase);
+                } else {
+                    delete impl->mBase;
+                }
             }
         }
     }

services/surfaceflinger/Layer.cpp

@@ -69,13 +69,15 @@ Layer::Layer(SurfaceFlinger* flinger,
     glGenTextures(1, &mTextureName);
 }
 
-void Layer::destroy() const {
-    mFlinger->destroyLayer(this);
+void Layer::destroy(RefBase const* base) {
+    mFlinger->destroyLayer(static_cast<LayerBase const*>(base));
 }
 
 void Layer::onFirstRef()
 {
     LayerBaseClient::onFirstRef();
+    setDestroyer(this);
+
     struct FrameQueuedListener : public SurfaceTexture::FrameAvailableListener {
         FrameQueuedListener(Layer* layer) : mLayer(layer) { }
     private:

services/surfaceflinger/Layer.h

@@ -45,7 +45,7 @@ class GLExtensions;
 
 // ---------------------------------------------------------------------------
 
-class Layer : public LayerBaseClient
+class Layer : public LayerBaseClient, private RefBase::Destroyer
 {
 public:
             Layer(SurfaceFlinger* flinger, DisplayID display,
@@ -79,7 +79,7 @@ public:
     inline const sp<FreezeLock>&  getFreezeLock() const { return mFreezeLock; }
 
 protected:
-    virtual void destroy() const;
+    virtual void destroy(RefBase const* base);
     virtual void onFirstRef();
     virtual void dump(String8& result, char* scratch, size_t size) const;