This runtime was designed to support the features of Objective-C 2 for use with GNUstep and other Objective-C programs. Highlights of this release include:
- Support for Apple-compatible garbage collection APIs, along with extensions to support CoreFoundation-style explicit reference counting in a garbage collected environment. This uses the Boehm garbage collector and is enabled by specifying boehm_gc=yes when building. This requires version 7.1 or later of libgc. Code compiled with -fobjc-gc can be mixed with code that implements normal reference counting and with code compiled with -fobjc-gc-only. The runtime supports both GC and non-GC code when compiled with GC support and will automatically select the correct behavior depending on the loaded code.
- The runtime will now use Boehm GC for several internal data structures, if it is built with GC enabled. This avoids the need for defensive programming with respect to thread safety in several places.
- This is the first release to provide a superset of the functionality provided by the Mac Objective-C runtime, as shipped with OS X 10.6.
- Full support for Automatic Reference Counting (ARC), compatible with OS X 10.7 and iOS 5, including support for __weak references.
- The LLVM optimisation passes have been improved and better tested. Code compiled with them now passes the EtoileFoundation test suite.