Preliminary code for emulation of the objc2 runtime weak reference fe…

…ature

Headers/GNUstepBase/GSIMap.h

@@ -132,6 +132,11 @@ extern "C" {
  *      GSI_MAP_ZEROED()
  *              Define this macro to check whether a map uses keys which may
  *              be zeroed weak pointers.  
+ *
+ *	GSI_MAP_NODE_CLASS
+ *		If defined, each node in the map has an 'isa' field at the
+ *		start which is initialised to be the specified class so that
+ *		the node looks like an instance of that class.
  */
 
 #ifndef	GSI_MAP_HAS_VALUE
@@ -384,6 +389,9 @@ typedef GSIMapNode_t *GSIMapNode;
 #endif
 
 struct	_GSIMapNode {
+#if	defined(GSI_MAP_NODE_CLASS)
+  void		*isa;		/* Node pretends to be instance of class */
+#endif
   GSIMapNode	nextInBucket;	/* Linked list of bucket.	*/
   GSIMapKey	key;
 #if	GSI_MAP_HAS_VALUE
@@ -1078,9 +1086,8 @@ GSIMapCountByEnumeratingWithStateObjectsCount(GSIMapTable map,
   return count;
 }
 
-#if	GSI_MAP_HAS_VALUE
 GS_STATIC_INLINE GSIMapNode
-GSIMapAddPairNoRetain(GSIMapTable map, GSIMapKey key, GSIMapVal value)
+GSIMapGetNode(GSIMapTable map)
 {
   GSIMapNode	node = map->freeNodes;
 
@@ -1090,11 +1097,24 @@ GSIMapAddPairNoRetain(GSIMapTable map, GSIMapKey key, GSIMapVal value)
       node = map->freeNodes;
     }
   map->freeNodes = node->nextInBucket;
+#if	defined(GSI_MAP_NODE_CLASS)
+  node->isa = (void*)(GSI_MAP_NODE_CLASS);
+#endif
+  node->nextInBucket = 0;
+  return node;
+}
+
+
+#if	GSI_MAP_HAS_VALUE
+GS_STATIC_INLINE GSIMapNode
+GSIMapAddPairNoRetain(GSIMapTable map, GSIMapKey key, GSIMapVal value)
+{
+  GSIMapNode	node = GSIMapGetNode(map);
+
   node->key = key;
   node->value = value;
   GSI_MAP_STORE_KEY(map, &node->key, key);
   GSI_MAP_STORE_VALUE(map, &node->value, value);
-  node->nextInBucket = 0;
   GSIMapRightSizeMap(map, map->nodeCount);
   GSIMapAddNodeToMap(map, node);
   return node;
@@ -1103,19 +1123,12 @@ GSIMapAddPairNoRetain(GSIMapTable map, GSIMapKey key, GSIMapVal value)
 GS_STATIC_INLINE GSIMapNode
 GSIMapAddPair(GSIMapTable map, GSIMapKey key, GSIMapVal value)
 {
-  GSIMapNode	node = map->freeNodes;
+  GSIMapNode	node = GSIMapGetNode(map);
 
-  if (node == 0)
-    {
-      GSIMapMoreNodes(map, map->nodeCount < map->increment ? 0: map->increment);
-      node = map->freeNodes;
-    }
-  map->freeNodes = node->nextInBucket;
   GSI_MAP_STORE_KEY(map, &node->key, key);
   GSI_MAP_RETAIN_KEY(map, node->key);
   GSI_MAP_STORE_VALUE(map, &node->value, value);
   GSI_MAP_RETAIN_VALUE(map, node->value);
-  node->nextInBucket = 0;
   GSIMapRightSizeMap(map, map->nodeCount);
   GSIMapAddNodeToMap(map, node);
   return node;
@@ -1124,16 +1137,9 @@ GSIMapAddPair(GSIMapTable map, GSIMapKey key, GSIMapVal value)
 GS_STATIC_INLINE GSIMapNode
 GSIMapAddKeyNoRetain(GSIMapTable map, GSIMapKey key)
 {
-  GSIMapNode	node = map->freeNodes;
+  GSIMapNode	node = GSIMapGetNode(map);
 
-  if (node == 0)
-    {
-      GSIMapMoreNodes(map, map->nodeCount < map->increment ? 0: map->increment);
-      node = map->freeNodes;
-    }
-  map->freeNodes = node->nextInBucket;
   GSI_MAP_STORE_KEY(map, &node->key, key);
-  node->nextInBucket = 0;
   GSIMapRightSizeMap(map, map->nodeCount);
   GSIMapAddNodeToMap(map, node);
   return node;
@@ -1142,17 +1148,10 @@ GSIMapAddKeyNoRetain(GSIMapTable map, GSIMapKey key)
 GS_STATIC_INLINE GSIMapNode
 GSIMapAddKey(GSIMapTable map, GSIMapKey key)
 {
-  GSIMapNode	node = map->freeNodes;
+  GSIMapNode	node = GSIMapGetNode(map);
 
-  if (node == 0)
-    {
-      GSIMapMoreNodes(map, map->nodeCount < map->increment ? 0: map->increment);
-      node = map->freeNodes;
-    }
-  map->freeNodes = node->nextInBucket;
   GSI_MAP_STORE_KEY(map, &node->key, key);
   GSI_MAP_RETAIN_KEY(map, node->key);
-  node->nextInBucket = 0;
   GSIMapRightSizeMap(map, map->nodeCount);
   GSIMapAddNodeToMap(map, node);
   return node;

Source/GSPrivate.h

@@ -637,5 +637,13 @@ void
 GSPrivateEncodeBase64(const uint8_t *src, NSUInteger length, uint8_t *dst)
   GS_ATTRIB_PRIVATE;
 
+#ifndef OBJC_CAP_ARC
+/* When we don't have a runtime with ARC to support weak references, we
+ * use our own version.
+ */
+void GSWeakInit() GS_ATTRIB_PRIVATE;
+BOOL objc_delete_weak_refs(id obj);
+#endif
+
 #endif /* _GSPrivate_h_ */
 

Source/NSConcreteHashTable.m

@@ -105,8 +105,8 @@ @interface	NSConcreteHashTable : NSHashTable
     pointerFunctionsReplace(&M->cb.pf, (void**)addr, (x).obj);
 
 #define GSI_MAP_READ_KEY(M,addr) \
-	(M->legacy ? *(addr) :\
-	 (__typeof__(*addr))pointerFunctionsRead(&M->cb.pf, (void**)addr))
+   (M->legacy ? *(addr) :\
+   (__typeof__(*addr))pointerFunctionsRead(&M->cb.pf, (void**)addr))
 
 #define	GSI_MAP_ENUMERATOR	NSHashEnumerator
 

Source/NSConcretePointerFunctions.h

@@ -29,14 +29,16 @@
 #endif
 
 #if defined(OBJC_CAP_ARC)
-#    include <objc/objc-arc.h>
-#    define WEAK_READ(x) objc_loadWeak((id*)x)
-#    define WEAK_WRITE(addr, x) objc_storeWeak((id*)addr, (id)x)
-#    define STRONG_WRITE(addr, x) objc_storeStrong((id*)addr, (id)x)
-#    define STRONG_ACQUIRE(x) objc_retain(x)
+#  include <objc/objc-arc.h>
+#  define WEAK_READ(x) objc_loadWeak((id*)x)
+#  define WEAK_WRITE(addr, x) objc_storeWeak((id*)addr, (id)x)
+#  define STRONG_WRITE(addr, x) objc_storeStrong((id*)addr, (id)x)
+#  define STRONG_ACQUIRE(x) objc_retain(x)
 #else
-#  define WEAK_READ(x) (*x)
-#  define WEAK_WRITE(addr, x) (*(addr) =  x)
+extern id objc_loadWeak(id *object);
+extern id objc_storeWeak(id *addr, id obj);
+#  define WEAK_READ(x) objc_loadWeak((id*)x)
+#  define WEAK_WRITE(addr, x) objc_storeWeak((id*)addr, (id)x)
 #  define STRONG_WRITE(addr, x) ASSIGN(*((id*)addr), ((id)x))
 #  define STRONG_ACQUIRE(x) RETAIN(((id)x))
 #endif

Source/NSObject.m

@@ -493,9 +493,7 @@ static BOOL objc_release_fast_no_destroy_internal(id anObject)
          * have been greater than zero)
          */
         (((obj)anObject)[-1].retained) = 0;
-#  ifdef OBJC_CAP_ARC
         objc_delete_weak_refs(anObject);
-#  endif
         return YES;
       }
 #else	/* GSATOMICREAD */
@@ -504,9 +502,7 @@ static BOOL objc_release_fast_no_destroy_internal(id anObject)
     pthread_mutex_lock(theLock);
     if (((obj)anObject)[-1].retained == 0)
       {
-#  ifdef OBJC_CAP_ARC
         objc_delete_weak_refs(anObject);
-#  endif
         pthread_mutex_unlock(theLock);
         return YES;
       }
@@ -947,6 +943,8 @@ + (void) load
 {
 #ifdef OBJC_CAP_ARC
   _objc_weak_load = gs_weak_load;
+#else
+  GSWeakInit();
 #endif
   objc_create_block_classes_as_subclasses_of(self);
 }

Source/ObjectiveC2/GNUmakefile

@@ -56,7 +56,11 @@ ObjectiveC2_OBJC_FILES += \
 endif
 
 ifeq ($(CC), clang)
+  # We need the flag for blocks support and we have ARC built in.
   ADDITIONAL_OBJCFLAGS = -fblocks
+else
+  # We need to emulated the weak reference API from the ARC runtime.
+  ObjectiveC2_OBJC_FILES += weak.m
 endif
 
 -include Makefile.preamble

Source/ObjectiveC2/README

@@ -1,6 +1,6 @@
 ObjectiveC2 framework implements the new Apple runtime APIs, introduced with
-OS X 10.5 on top of the GCC Objective-C runtime.  Its use is now discouraged.
-This code has been merged into the GNUstep Objective-C-2.0 runtime, which can
-act as a drop-in replacement for GCC libobjc.  You can find the code here:
-
-svn://svn.gna.org/svn/gnustep/libs/libobjc2/trunk
+OS X 10.5 (and later) on top of the GCC Objective-C runtime.  Much code has
+been merged into the GNUstep Objective-C-2.0 runtime, which is used when 
+compiling with clang (svn://svn.gna.org/svn/gnustep/libs/libobjc2/trunk).
+Somewhat recent versions of the GNU runtime implement much of the newer Apple
+APIs.