Name: Darwin
URL: http://www.opensource.apple.com/
Version: 371.2
License: Apple Public Source License 2.0

Two files are excerpted here:

objc-sync.h from:
http://opensource.apple.com/source/objc4/objc4-371.2/runtime/objc-sync.h

Modifications:
- None

objc-sync.m from:
http://opensource.apple.com/source/objc4/objc4-371.2/runtime/objc-sync.m

Modifications:
- Replaced internal API references with private implementations.
- Renamed objc_pthread_key, objc_pthread_data, and functions referencing
  them to "j2objc_*", to make it more obvious which data is used.
- Used NSLog instead internal logging function in objc_sync_enter().
- Fixed assertion in objc_sync_wait() so valid time-outs don't fail.
- Used NSSpinLock functions instead of private _spin_lock functions.