GNUstep Objective-C Runtime 2.2
===============================

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