On 2012-10-12 12:40:35 +0000, Jacob Carlborg <[email protected]> said:
On 2012-10-11 20:19, Michel Fortin wrote:
Most likely, the object objc_msgSend is called on has been deallocated,
which would mean that windowSendEvent is called with a deallocated
NSWindow object as its first argument.
I have done some investigation and I can call other methods on the
NSWindow object, but regular methods and super methods. This would
indicate that it's something wrong with the NSEvent object, but I can
call methods on that as well.
That's not a very good proof. You might just be calling a method on the
object before it gets released. Often, Objective-C objects are
autoreleased, which means that deallocation is postponed until the end
of the current event loop iteration (unless someone increase the
reference counter again), so you might be having a valid pointer to it
right now, but it might already be in the queue for deallocation.
If you want to test for the deallocated object theory, just call retain
via objc_msgSend on any object you suspect might be deallocated too
early, one by one, until you find the one that is causing the trouble.
Once you find the problematic object, print its address on the console
and use Instrument…
Since you're on OS X, I'd suggest you try using Instruments to track the
reference counters of all Objective-C objects within your program until
it crashes, then search back the history for all
retain/release/autorelease calls made to the address the EXEC_BAD_ACCESS
happens on.
I don't know how to use Instruments for this.
It's the Allocations profile you need. It'll record logs of every
allocation, deallocation, and optionally every change to reference
counters (click the (i) icon next to Allocations and check "Record
reference counts"). Each log entry has a stack trace.
To see the raw log, you should open the Object List pane at the bottom
(click the Statistics button, it's a menu). There'll be a lot of
unrelated allocations, which is why you should output the pointer
address to the object to the console (available under the same menu),
and then search it in the log (or filter on it). Then look at the call
stack for each entry, and hopefully you'll understand what's happening.
I hope this helps.
--
Michel Fortin
[email protected]
http://michelf.ca/
