Fix os_transaction and make bools and nulls into globals

XPC bools and nulls were made into global to match their behavior in Apple's libxpc; users are allowed to compare XPC object pointers with the global XPC_BOOL_{TRUE,FALSE} constants, which are pointers to global variables, so this now allows that to work as expected.

CMakeLists.txt

@@ -32,7 +32,7 @@ set(xpc_sources
 	subr_sbuf.c
 	xpc_pipe.c
 	reboot3.c
-	transaction_private.c
+	transaction.m
 )
 
 set(DYLIB_INSTALL_NAME "/usr/lib/system/libxpc.dylib")
@@ -49,6 +49,12 @@ add_circular(xpc FAT
 		launch
 		system_info
 		system_dyld
+	UPWARD
+		# break an upward dependency on libobjc
+		# ---
+		# note that we don't actually need to intialize it ourselves by calling `objc_init`;
+		# libSystem guarantees that we'll be initialized after libdispatch, and libdispatch already initializes libobjc
+		objc
 )
 #target_link_libraries(xpc system)
 install(TARGETS xpc DESTINATION libexec/darling/usr/lib/system)

transaction.m

@@ -4,17 +4,11 @@
 struct os_transaction_s;
 struct os_transaction_extra_vtable_s {};
 struct os_transaction_vtable_s {
-	void (*_os_obj_xref_dispose)(_os_object_t);
-	void (*_os_obj_dispose)(_os_object_t);
+	_OS_OBJECT_CLASS_HEADER();
 	struct os_transaction_extra_vtable_s _os_obj_vtable;
 };
-extern const struct os_transaction_vtable_s OS_OBJECT_CLASS_SYMBOL(os_transaction) __asm__(OS_OBJC_CLASS_RAW_SYMBOL_NAME(OS_OBJECT_CLASS(os_transaction)));
 
-const struct os_transaction_vtable_s OS_OBJECT_CLASS_SYMBOL(os_transaction) = {
-	._os_obj_xref_dispose = NULL,
-	._os_obj_dispose = NULL,
-	._os_obj_vtable = {},
-};
+extern const struct os_transaction_vtable_s OS_OBJECT_CLASS_SYMBOL(os_transaction) __asm__(OS_OBJC_CLASS_RAW_SYMBOL_NAME(OS_OBJECT_CLASS(os_transaction)));
 
 #define OS_TRANSACTION_CLASS (&OS_OBJECT_CLASS_SYMBOL(os_transaction))
 
@@ -29,3 +23,9 @@ struct os_transaction_s {
 os_transaction_t os_transaction_create(const char* transaction_name) {
 	return (os_transaction_t)_os_object_alloc_realized(OS_TRANSACTION_CLASS, sizeof(struct os_transaction_s));
 };
+
+OS_OBJECT_NONLAZY_CLASS
+@implementation OS_OBJECT_CLASS(os_transaction)
+OS_OBJECT_NONLAZY_CLASS_LOAD
+
+@end

xpc_internal.h

@@ -120,6 +120,8 @@ typedef union {
 } xpc_u;	
 
 
+// indicates that the object should never be released
+#define _XPC_KEEP_ALIVE UINT32_MAX
 #define _XPC_FROM_WIRE 0x1
 struct xpc_object {
 	uint8_t			xo_xpc_type;
@@ -164,6 +166,18 @@ struct xpc_service {
 #define xo_activity xo_u.activity
 #define xo_connection xo_u.connection
 
+#define _XPC_GLOBAL_OBJECT_INITIALIZER(type, extra_size, union_value) { \
+	.xo_xpc_type = type, \
+	.xo_flags = 0, \
+	.xo_refcnt = _XPC_KEEP_ALIVE, \
+	.xo_size = extra_size, \
+	.xo_u = { \
+		union_value, \
+	}, \
+	.xo_audit_token = NULL, \
+	.xo_link = NULL, \
+}
+
 __private_extern__ struct xpc_object *_xpc_prim_create(int type, xpc_u value,
     size_t size);
 __private_extern__ struct xpc_object *_xpc_prim_create_flags(int type,

xpc_misc.c

@@ -568,6 +568,9 @@ XPC_INLINE struct xpc_object* xpc_unpack(const void* buf, size_t size, size_t* p
 void
 xpc_object_destroy(struct xpc_object *xo)
 {
+	if (xo->xo_refcnt == _XPC_KEEP_ALIVE)
+		return;
+
 	if (xo->xo_xpc_type == _XPC_TYPE_DICTIONARY)
 		xpc_dictionary_destroy(xo);
 
@@ -589,9 +592,10 @@ xpc_object_destroy(struct xpc_object *xo)
 xpc_object_t
 xpc_retain(xpc_object_t obj)
 {
-	struct xpc_object *xo;
+	struct xpc_object *xo = obj;
+	if (xo->xo_refcnt == _XPC_KEEP_ALIVE)
+		return obj;
 
-	xo = obj;
 	OSAtomicIncrement32(&xo->xo_refcnt);
 	return (obj);
 }
@@ -599,9 +603,10 @@ xpc_retain(xpc_object_t obj)
 void
 xpc_release(xpc_object_t obj)
 {
-	struct xpc_object *xo;
+	struct xpc_object *xo = obj;
+	if (xo->xo_refcnt == _XPC_KEEP_ALIVE)
+		return;
 
-	xo = obj;
 	if (OSAtomicDecrement32(&xo->xo_refcnt) > 0)
 		return;
 
@@ -787,8 +792,7 @@ ld2xpc(launch_data_t ld)
 		memcpy(__DECONST(void *, val.str), ld->string, ld->string_len);
 		xo = _xpc_prim_create(ld_to_xpc_type[ld->type], val, ld->string_len);
 	} else if (ld->type == LAUNCH_DATA_BOOL) {
-		val.b = (bool)ld->boolean;
-		xo = _xpc_prim_create(ld_to_xpc_type[ld->type], val, 0);
+		xo = xpc_bool_create((bool)ld->boolean);
 	} else if (ld->type == LAUNCH_DATA_ARRAY) {
 		xo = xpc_array_create(NULL, 0);
 		for (uint64_t i = 0; i < ld->_array_cnt; i++)
@@ -803,19 +807,13 @@ ld2xpc(launch_data_t ld)
 xpc_object_t
 xpc_copy_entitlement_for_token(const char *key __unused, audit_token_t *token __unused)
 {
-	xpc_u val;
-
-	val.b = true;
-	return (_xpc_prim_create(_XPC_TYPE_BOOL, val,0));
+	return xpc_bool_create(true);
 }
 
 xpc_object_t
 xpc_copy_entitlements_for_pid(pid_t pid)
 {
-    xpc_u val;
-
-    val.b = true;
-    return (_xpc_prim_create(_XPC_TYPE_BOOL, val,0));
+	return xpc_bool_create(true);
 }
 
 

xpc_type.c

@@ -54,14 +54,19 @@ xt _xpc_type_uuid;
 xt _xpc_type_double;
 xt _xpc_type_pointer;
 
-
 struct _xpc_bool_s {
+	// we have to wrap it in `_xpc_bool_s` because the header defines the variable with that type
+	struct xpc_object xo;
 };
 
-typedef const struct _xpc_bool_s xb;
+const struct _xpc_bool_s _xpc_bool_true = {
+	.xo = _XPC_GLOBAL_OBJECT_INITIALIZER(_XPC_TYPE_BOOL, 0, .b = true),
+};
+const struct _xpc_bool_s _xpc_bool_false = {
+	.xo = _XPC_GLOBAL_OBJECT_INITIALIZER(_XPC_TYPE_BOOL, 0, .b = false),
+};
 
-xb _xpc_bool_true;
-xb _xpc_bool_false;
+const struct xpc_object _xpc_null = _XPC_GLOBAL_OBJECT_INITIALIZER(_XPC_TYPE_NULL, 0, .b = false); // requires a union value, so just set the boolean
 
 static size_t xpc_data_hash(const uint8_t *data, size_t length);
 
@@ -146,32 +151,19 @@ _xpc_prim_create_flags(int type, xpc_u value, size_t size, uint16_t flags)
 xpc_object_t
 xpc_null_create(void)
 {
-	xpc_u val = {0};
-	return _xpc_prim_create(_XPC_TYPE_NULL, val, 0);
+	return &_xpc_null;
 }
 
 xpc_object_t
 xpc_bool_create(bool value)
 {
-	xpc_u val;
-
-	val.b = value;
-	return _xpc_prim_create(_XPC_TYPE_BOOL, val, 1);
+	return value ? XPC_BOOL_TRUE : XPC_BOOL_FALSE;
 }
 
 bool
 xpc_bool_get_value(xpc_object_t xbool)
 {
-	struct xpc_object *xo;
-
-	xo = xbool;
-	if (xo == NULL)
-		return (0);
-
-	if (xo->xo_xpc_type == _XPC_TYPE_BOOL)
-		return (xo->xo_bool);
-
-	return (false);
+	return xbool == XPC_BOOL_FALSE ? false : true;
 }
 
 xpc_object_t