Open Radar

 
Summary:
I'm trying to share a IOSurface object between an OS X app and a bundled XPC service. I'm targeting Mavericks and I'd like to use the Cocoa interface to XPC, rather than the low-level C API. Unfortunately, there doesn't seem to be a way to pass the raw xpc_object_t I get from IOSurfaceCreateXPCObject() over an NSXPConnection, nor to wrap that xpc_object_t in a Cocoa object that NSXPConnection can marshal.

Ideally, I'd like to be able to define a protocol like this:

@protocol LibremonProtocol <NSObject>

- (oneway void)openFile:(NSString*)filename
	surface:(xpc_object_t)surface
	completion:(void(^)(id ebook, NSError * error))completion;

@end

associate it with an NSXPCInterface, and then call openFile:surface:completion on the NSXPCConnection's remoteObjectProxy, passing the return value from IOSurfaceCreateXPCObject() in the surface: parameter.

Steps to Reproduce:
1. Set up an Xcode project with an OS X app main target and an ancillary XPC service target;

2. Write boilerplate client/server code to set up and accept an NSXPCConnection;

3. Define an Objective-C protocol with a single method that takes an xpc_object_t parameter;

4. Create an IOSurfaceRef object and obtain an xpc_object_t from it using IOSurfaceCreateXPCObject();

5. Attempt to invoke the protocol method on the remote object proxy;

Expected Results:
The XPC server receives the call, getting an xpc_object_t that can be passed to IOSurfaceLookupFromXPCObject() to get a usable, shared IOSurface.

Actual Results:
Attempting to call the remote object proxy throws an exception:

*** -[NSXPCEncoder _checkObject:]: This coder only encodes objects that adopt NSSecureCoding (object is of class 'OS_xpc_mach_send').