Change [1] to [] for variable length structure elements (C99 - silences array out of bounds errors).

Added fields to the end of the class structure for strong / weak ivar bitmaps (not yet generated by any compiler).

Fixed definition of __sync_swap() so that it works on GCC again.

class.h

@@ -1,5 +1,22 @@
 #ifndef __OBJC_CLASS_H_INCLUDED
 #define __OBJC_CLASS_H_INCLUDED
+
+/**
+ * Overflow bitfield.  Used for bitfields that are more than 63 bits.
+ */
+struct objc_bitfield
+{
+	/**
+	 * The number of elements in the values array.
+	 */
+	int32_t  length;
+	/**
+	 * An array of values.  Each 32 bits is stored in the native endian for the
+	 * platform.
+	 */
+	int32_t values[0];
+};
+
 struct objc_class
 {
 	/**
@@ -83,7 +100,9 @@ struct objc_class
 	*/
 
 	/**
-	* The version of the ABI used for this class.  This is currently always zero.  
+	* The version of the ABI used for this class.  Zero indicates the ABI first
+	* implemented by clang 1.0.  One indicates the presence of bitmaps
+	* indicating the offsets of strong, weak, and unretained ivars.
 	*/
 	long                       abi_version;
 
@@ -108,6 +127,26 @@ struct objc_class
 	* the accessor methods for each property.
 	*/
 	struct objc_property_list *properties;
+
+	/**
+	 * GC / ARC ABI: Fields below this point only exist if abi_version is >= 1.
+	 */
+
+	/**
+	 * The location of all strong pointer ivars declared by this class.  
+	 *
+	 * If the low bit of this field is 0, then this is a pointer to an
+	 * objc_bitfield structure.  If the low bit is 1, then the remaining 63
+	 * bits are set, from low to high, for each ivar in the object that is a
+	 * strong pointer.
+	 */
+	int64_t                    strong_pointers;
+	/**
+	 * The location of all zeroing weak pointer ivars declared by this class.
+	 * The format of this field is the same as the format of the
+	 * strong_pointers field.
+	 */
+	int64_t                    weak_pointers;
 };
 
 /**

encoding2.c

@@ -130,7 +130,7 @@ static void parse_struct(const char **type, type_parser callback, void *context)
 
 inline static void round_up(size_t *v, size_t b)
 {
-        if (0 == b)
+	if (0 == b)
 	{
 		return;
 	}

gc_boehm.c

@@ -61,7 +61,7 @@ struct objc_slot* objc_get_slot(Class cls, SEL selector);
 #ifndef __has_builtin
 #	define __has_builtin(x) 0
 #endif
-#if __has_builtin(__sync_swap)
+#if !__has_builtin(__sync_swap)
 #define __sync_swap __sync_lock_test_and_set
 #endif
 

ivar.h

@@ -41,7 +41,7 @@ struct objc_ivar_list
 	int              count;
 	/**
 	 * An array of instance variable metadata structures.  Note that this array
-	 * has count elements, not 1.
+	 * has count elements.
 	 */
-	struct objc_ivar ivar_list[1];
+	struct objc_ivar ivar_list[];
 };

method_list.h

@@ -37,7 +37,7 @@ struct objc_method_list
 	 */
 	int                       count;
 	/**
-	 * An array of methods.  Note that the actual size of this is count, not 1.
+	 * An array of methods.  Note that the actual size of this is count.
 	 */
-	struct objc_method        methods[1];
+	struct objc_method        methods[];
 };

module.h

@@ -37,7 +37,7 @@ struct objc_symbol_table_abi_8
 	 * Current compilers only use this for constant strings.  The runtime
 	 * permits other types.
 	 */
-	void           *definitions[1];
+	void           *definitions[];
 };
 
 /**
@@ -98,5 +98,5 @@ struct objc_static_instance_list
 	/**
 	 * NULL-terminated array of statically-allocated instances.
 	 */
-	id    instances[1];
+	id    instances[];
 };

properties.h

@@ -95,6 +95,6 @@ struct objc_property_list
 	/**
 	 * List of properties.
 	 */
-	struct objc_property properties[1];
+	struct objc_property properties[];
 };
 

protocol.h

@@ -12,7 +12,7 @@ struct objc_method_description_list
 	 * field points to the name, not to the index of the uniqued version of the
 	 * name.  You must not use them for dispatch.
 	 */
-	struct objc_selector methods[1];
+	struct objc_selector methods[];
 };
 
 
@@ -116,6 +116,6 @@ struct objc_protocol_list
 	 *
 	 * The instances in this array may be any version of protocols.
 	 */
-	Protocol2                 *list[1];
+	Protocol2                 *list[];
 };