[Rubycocoa-talk] GC + NSNotifications

[Brian M. <ma...@ex...>]

Here's a program that shows a core dump when posting an NSNotification  
after Ruby GC. I suspect I'm doing something stupid, possibly with a  
selector.

--------------------------------------
#!/usr/bin/env ruby

require 'osx/cocoa'
include OSX

Center = NSNotificationCenter.defaultCenter

class Receiver < NSObject

   def init
     Center.addObserver_selector_name_object(self, :handle_,
                                             "notification name", nil)
   end

   def handle(notification)
     puts notification
   end
end

class Sender < NSObject
   def announce
     Center.postNotificationName_object("notification name", self)
   end
end

if $0 == __FILE__
   r = Receiver.alloc.init
   # Center.postNotificationName_object("notification name", self)
   Sender.alloc.init.announce    # removable
   GC.start                      # removable
   puts "About to post"
   Sender.alloc.init.announce
   # Center.postNotificationName_object("notification name", self)
   puts "I survived!"
end

--------------------------------------


Here's the result with stock Leopard RubyCocoa  
(OSX::RUBYCOCOA_VERSION=> "0.13.1"):

563 $ ruby x.rb
NSConcreteNotification 0x57a8f0 {name = notification name; object =  
<Sender: 0x2a9a30>}
x.rb:30: [BUG] Segmentation fault
ruby 1.8.6 (2007-09-24) [universal-darwin9.0]

Abort trap

Most any change you make to the code prevents the core dump:
- remove either of the lines marked removable.
- remove the assignment to the global (but keep the alloc.init).
- change the first use of Sender to post the notification directly.  
(Changing the second does not prevent the core dump.)

I tried using addRubyMethod_withType (per http://www.rubycocoa.com/appleremote/2 
  ), but got all the same behavior.

Here's the backtrace:

#0  0x941300ea in kill$UNIX2003 ()
(gdb) bt
#0  0x941300ea in kill$UNIX2003 ()
#1  0x941a73f2 in raise ()
#2  0x941b69af in abort ()
#3  0x000cdc50 in rb_bug ()
#4  0x0013464f in rb_gc_mark_trap_list ()
#5  0x9412e5eb in _sigtramp ()
#6  0xffffffff in ?? ()
#7  0x000cfe3c in rb_clear_cache_by_class ()
#8  0x000db695 in rb_obj_respond_to ()
#9  0x000db721 in rb_respond_to ()
#10 0x0018a3d4 in rbobj_call_ruby ()
#11 0x0018689a in sel_to_rbobj ()
#12 0x96ba8424 in ffi_prep_cif_machdep ()
#13 0x94345bda in NSZoneMalloc ()
#14 0x936e19da in _CFXNotificationResetSessionForTask ()
#15 0x936e1cb3 in _CFXNotificationPostNotification ()
#16 0x94342fd0 in NSPopAutoreleasePool ()
#17 0x9434c668 in _NSDescriptionWithLocaleFunc ()
#18 0x96ba81dd in ffi_call_SYSV ()
#19 0x96ba8771 in ffi_call ()
#20 0x00196a6c in rb_ffi_dispatch ()
#21 0x00181b65 in objcptr_s_new_with_cptr ()
#22 0x00182e44 in init_mdl_OCObjWrapper ()
#23 0x96ba8424 in ffi_prep_cif_machdep ()
#24 0x000da18c in rb_eval_string_wrap ()
#25 0x000dad6a in rb_eval_string_wrap ()
#26 0x000d80da in rb_eval_string_wrap ()
#27 0x000e706e in rb_load_protect ()
#28 0x000e709f in ruby_exec ()
#29 0x000e70cb in ruby_run ()
#30 0x00001fff in main ()

-----
Brian Marick, independent consultant
Mostly on agile methods with a testing slant
www.exampler.com, www.exampler.com/blog, www.twitter.com/marick