Changeset 115534 in webkit for trunk/Source/JavaScriptCore/heap/PassWeak.h

Timestamp:

Apr 27, 2012, 8:43:29 PM (13 years ago)

Author:

[email protected]

Message:

Only allow non-null pointers in the WeakSet
​https://bugs.webkit.org/show_bug.cgi?id=85119

Reviewed by Darin Adler.

../JavaScriptCore:

This is a step toward more efficient finalization.

No clients put non-pointers (JSValues) into Weak<T> and PassWeak<T>.

Some clients put null pointers into Weak<T> and PassWeak<T>, but this is
more efficient and straight-forward to model with a null in the Weak<T>
or PassWeak<T> instead of allocating a WeakImpl just to hold null.

• heap/PassWeak.h:

(JSC): Removed the Unknown (JSValue) type of weak pointer because it's
unused now.

(PassWeak): Don't provide a default initializer for our JSCell* argument.
This feature was only used in one place, and it was a bug.

(JSC::::get): Don't check for a null stored inside our WeakImpl: that's
not allowed anymore.

(JSC::PassWeak::PassWeak): Handle null as a null WeakImpl instead of
allocating a WeakImpl and storing null into it.

• heap/Weak.h:

(Weak):
(JSC::::Weak): Same changes as in PassWeak<T>.

• heap/WeakBlock.cpp:

(JSC::WeakBlock::visitLiveWeakImpls):
(JSC::WeakBlock::visitDeadWeakImpls): Only non-null cells are valid in
the WeakSet now, so no need to check for non-cells and null cell pointers.

• heap/WeakImpl.h:

(JSC::WeakImpl::WeakImpl): Only non-null cells are valid in the WeakSet
now, so ASSERT that.

../WebCore:

• bridge/jsc/BridgeJSC.cpp:

(JSC::Bindings::Instance::Instance): Don't allocate a WeakImpl just to
store null. This was needless, and is now a compile error. Instead,
rely on the default constructor, which will produce a cheap null.

File:

• trunk/Source/JavaScriptCore/heap/PassWeak.h (modified) (5 diffs)

trunk/Source/JavaScriptCore/heap/PassWeak.h

@@ -51 +51 @@
 };
 
-template<typename Base> class WeakImplAccessor<Base, Unknown> {
-public:
-    typedef JSValue GetType;
-
-    const JSValue* operator->() const;
-    const JSValue& operator*() const;
-    GetType get() const;
-};
-
 template<typename T> class PassWeak : public WeakImplAccessor<PassWeak<T>, T> {
 public:
@@ -67 +58 @@
     PassWeak();
     PassWeak(std::nullptr_t);
-    PassWeak(JSGlobalData&, GetType = GetType(), WeakHandleOwner* = 0, void* context = 0);
+    PassWeak(JSGlobalData&, GetType, WeakHandleOwner* = 0, void* context = 0);
 
     // It somewhat breaks the type system to allow transfer of ownership out of
@@ -106 +97 @@
 template<typename Base, typename T> inline typename WeakImplAccessor<Base, T>::GetType WeakImplAccessor<Base, T>::get() const
 {
-    if (!static_cast<const Base*>(this)->m_impl || static_cast<const Base*>(this)->m_impl->state() != WeakImpl::Live || !static_cast<const Base*>(this)->m_impl->jsValue())
+    if (!static_cast<const Base*>(this)->m_impl || static_cast<const Base*>(this)->m_impl->state() != WeakImpl::Live)
         return GetType();
     return jsCast<T*>(static_cast<const Base*>(this)->m_impl->jsValue().asCell());
@@ -118 +109 @@
 #endif
 
-template<typename Base> inline const JSValue* WeakImplAccessor<Base, Unknown>::operator->() const
-{
-    ASSERT(static_cast<const Base*>(this)->m_impl && static_cast<const Base*>(this)->m_impl->state() == WeakImpl::Live);
-    return &static_cast<const Base*>(this)->m_impl->jsValue();
-}
-
-template<typename Base> inline const JSValue& WeakImplAccessor<Base, Unknown>::operator*() const
-{
-    ASSERT(static_cast<const Base*>(this)->m_impl && static_cast<const Base*>(this)->m_impl->state() == WeakImpl::Live);
-    return static_cast<const Base*>(this)->m_impl->jsValue();
-}
-
-template<typename Base> inline typename WeakImplAccessor<Base, Unknown>::GetType WeakImplAccessor<Base, Unknown>::get() const
-{
-    if (!static_cast<const Base*>(this)->m_impl || static_cast<const Base*>(this)->m_impl->state() != WeakImpl::Live)
-        return GetType();
-    return static_cast<const Base*>(this)->m_impl->jsValue();
-}
-
 template<typename T> inline PassWeak<T>::PassWeak()
     : m_impl(0)
@@ -148 +120 @@
 
 template<typename T> inline PassWeak<T>::PassWeak(JSGlobalData& globalData, typename PassWeak<T>::GetType getType, WeakHandleOwner* weakOwner, void* context)
-    : m_impl(globalData.heap.weakSet()->allocate(getType, weakOwner, context))
+    : m_impl(getType ? globalData.heap.weakSet()->allocate(getType, weakOwner, context) : 0)
 {
 }