Changeset 24059 in webkit for trunk/JavaScriptCore/wtf/HashTraits.h

Timestamp:

Jul 6, 2007, 5:09:08 AM (18 years ago)

Author:

mjs

Message:

JavaScriptCore:

Reviewed by Antti.

• <rdar://problem/5311093> JavaScriptCore fails to build with strict-aliasing warnings

• Configurations/Base.xcconfig: Re-enable -Wstrict-aliasing
• bindings/jni/jni_utility.cpp: (KJS::Bindings::getJNIEnv): Type-pun via a union instead of a pointer cast.
• wtf/HashMap.h: (WTF::): Instead of doing type-punned assignments via pointer cast, do one of three things: (1) assign directly w/o cast if storage type matches real type; (2) assign using cast via union if type does not need reffing; (3) copy with memcpy and ref/deref manually if type needs reffing. This is ok peref-wise because memcpy of a constant length gets optomized. HashTraits are now expected to make ref()/deref() take the storage type, not the true type.
• wtf/HashSet.h: (WTF::): Same basic idea.
• wtf/HashTable.h: (WTF::): Added Assigner template for use by HashMap/HashSet. Change RefCounter to call ref() and deref() via storage type, avoiding the need to type-pun. (WTF::RefCounter::ref): ditto (WTF::RefCounter::deref): ditto
• wtf/HashTraits.h: (WTF::): Change ref() and deref() for RefPtr HashTraits to take the storage type; cast via union to pointer type.
• wtf/FastMalloc.cpp: (WTF::TCMalloc_PageHeap::init): Changed from constructor to init function so this can go in a union. (WTF::): redefine pageheap macro in terms of getPageHeap(). (WTF::getPageHeap): new inline function, helper for pageheap macro. This hides the cast in a union. (WTF::TCMalloc_ThreadCache::InitModule): Call init() instead of using placement new to initialize page heap.
• wtf/TCPageMap.h: (TCMalloc_PageMap1::init): Changed from constructor to init function. (TCMalloc_PageMap2::init): ditto (TCMalloc_PageMap3::init): ditto

WebCore:

Reviewed by Antti.

• <rdar://problem/5311093> JavaScriptCore fails to build with strict-aliasing warnings

• platform/StringHash.h: (WTF::): Adapt to newer way to do storage types.

File:

• trunk/JavaScriptCore/wtf/HashTraits.h (modified) (1 diff)

trunk/JavaScriptCore/wtf/HashTraits.h

@@ -104 +104 @@
     template<typename P> struct HashTraits<RefPtr<P> > : GenericHashTraits<RefPtr<P> > {
         typedef HashTraits<typename IntTypes<sizeof(P*)>::SignedType> StorageTraits;
+        typedef typename StorageTraits::TraitType StorageType;
         static const bool emptyValueIsZero = true;
         static const bool needsRef = true;
-        static void ref(const RefPtr<P>& p) { if (p) p->ref(); }
-        static void deref(const RefPtr<P>& p) { if (p) p->deref(); }
+
+        typedef union { 
+            P* m_p; 
+            StorageType m_s; 
+        } UnionType;
+
+        static void ref(const StorageType& s) 
+        { 
+            if (const P* p = reinterpret_cast<const UnionType*>(&s)->m_p) 
+                const_cast<P*>(p)->ref(); 
+        }
+        static void deref(const StorageType& s) 
+        { 
+            if (const P* p = reinterpret_cast<const UnionType*>(&s)->m_p) 
+                const_cast<P*>(p)->deref(); 
+        }
     };