With Xcode 4.4.1 under OS 10.7.4, I have an app targeting either 10.6 or 10.7 (I've tried both).
This app creates one subtask (not thread) for each effective CPU (in my case, 8). The subtasks do a lengthy SIMD computation. [Note: Threads do not work here due to excessive malloc contention.]
When I run the Release target from within Xcode then Quit the app (or just try Quit Xcode), the subtasks all quit but the main app that created them does not. Activity Monitor shows one thread for this app using 4 kb of memory. The Stop Tasks button
in Xcode does not go off (and no longer works) and, even worse, Xcode itself will not Quit unless I use Force Quit. Strangely, the app thread showing in Activity Monitor will not terminate even with Force Quit. [I have to Restart the computer to get rid
of it.]
None of this happens with the Debug target. There, all is OK. Likewise, all of this worked fine in Snow Leopard.
I'm a bit out of my depth here and would appreciate any hints.
Thanks.