This is the second update to the second major release of the GNUstep Objective-C runtime (a.k.a. libobjc2). This runtime was designed to support the features of modern dialects of Objective-C for use with GNUstep and other Objective-C programs.

Highlights of this release include:

• Initial support for RISC-V 64-bit (rv64) including an architecture-specific objc_msgSend, and block trampoline implementation. Please note that double-precision floating-point support (rv64d) is required for the objc_msgSend implementation.
• Initial support for Windows on ARM64 with fast-path objc_msgSend.
• Numerous improvements to the Objective-C++ exception interoperation code. The runtime now dynamically detects whether the libcxxrt, libsupc++, or libc++abi variant of the Itanium C++ Exception ABI is being used. This is the first version to support exception interoperability with libc++abi.
• Because we no longer need to identify the specific C++ runtime, we can link to it indirectly via the C++ standard library, which enables more C++ to be used in the Objective-C runtime.
• The minimum CMake version has been bumped to 3.16, which supports Objective-C. This support is now used, simplifying the build.
• Support for GC mode is gone. Apple dropped support for this a long time ago.
• objc_setUncaughtExceptionHandler is added, which avoids consuming code needing to access a library-owned global.
• The selector-table code has been rewritten in C++, improving performance of adding selectors. This is unlikely to have a measurable impact on performance outside of contrived test cases, but the new code is more maintainable.
• Several bug fixes in the ARC code, especially in corner cases surrounding weak references.
• Support for fast-path allocation / initialisation functions. Root classes that opt into this should implement +_TrivialAllocInit (this can be an empty method, it is not called). Clang 18 or later will emit calls to the fast-path functions for +alloc, +allocWithZone: and +alloc + -init calls. This should improve code density as well as performance.

You may obtain the code for this release from git and use the 2.2 branch:

https://github.com/gnustep/libobjc2.git

Alternatively, a tarball is available from:

https://github.com/gnustep/libobjc2/archive/v2.2.zip https://github.com/gnustep/libobjc2/archive/v2.2.tar.gz

The runtime library is responsible for implementing the core features of the object model, as well as exposing introspection features to the user. The GNUstep runtime implements a superset of Apple's Objective-C Runtime APIs.

If you come across any problems, please file them in the issue tracker:

https://github.com/gnustep/libobjc2/issues