Changeset 115534 in webkit for trunk/Source/JavaScriptCore/heap/Weak.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/Weak.h (modified) (2 diffs)

trunk/Source/JavaScriptCore/heap/Weak.h

@@ -41 +41 @@
     Weak();
     Weak(std::nullptr_t);
-    Weak(JSGlobalData&, GetType = GetType(), WeakHandleOwner* = 0, void* context = 0);
+    Weak(JSGlobalData&, GetType, WeakHandleOwner* = 0, void* context = 0);
 
     enum HashTableDeletedValueTag { HashTableDeletedValue };
@@ -80 +80 @@
 
 template<typename T> inline Weak<T>::Weak(JSGlobalData& globalData, typename Weak<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)
 {
 }