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@davidchisnall davidchisnall released this Apr 26, 2019 · 53 commits to master since this release

This 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.

This release introduces a new Objective-C ABI, which is designed to be forward
compatible with future changes and removes a large number of hacks that were
required for compatibility with the prior ABI that included features introduced
in the 1980s. Highlights include:

  • The linker now removes duplicate selectors within a library.

  • The linker will remove duplicate protocol definitions within a library.

  • Protocols and classes are now always accessed via an indirection layer, so
    they can be extended by future versions of the ABI without breaking
    compatibility.

  • Categories can include property metadata and both categories.

  • Constant strings are now emitted with a richer structure, which provides
    faster hashing and better unicode support.

  • Instance variable metadata includes size and alignment, allowing better object
    layout and more accurate introspection. Instance variable metadata now
    includes more accurate information about ARC ownership semantics.

  • Method metadata now includes extended type information, allowing bridged
    languages to understand the class that methods expect and not just the fact
    that they take an object. This was previously an obstacle to supporting
    JavaScriptCore's Objective-C bridge with GNUstep.

In addition to the new ABI, there are several improvements on Windows:

  • The runtime now uses SEH-based exception handling on Windows. This
    interoperates with C++ exceptions in libraries compiled with MSVC or
    MSVC-compatible compilers.

  • All of the assembly code paths now fully support i386 and x64 Windows.

  • Object allocations on 32-bit Windows now use _aligned_malloc to guarantee
    sufficient alignment for AVX vectors in instance variables.

  • The runtime now uses fibre-local storage and critical sections on Windows,
    improving performance in multithreaded workloads on Windows.

  • Public runtime functions are now marked dllexport, so the runtime can be built
    as objc.dll on Windows.

WARNING: The new ABI is currently incompatible with incremental linking on
Windows, so projects built with Microsoft's linker must disable incremental
linking.

Note: Microsoft's WinObjC project contains a friendly fork of this library that
includes a work around for the incremental linking issue. If you wish to use
incremental linking on Windows, please use that version. A subsequent version
of clang and link.exe should include a fix that will make it possible to use
this version with incremental linking.

The runtime will now use the new ABI's data structures internally and will
automatically upgrade on-disk structures from old ABIs when used with the old
ABI. As a result, memory usage will be higher when using the old ABI and users
who are unable to recompile their code may prefer to stick with the 1.9.x
release series. Mixing libraries compiled with the old and new ABIs is not
supported and will abort at run time.

The new ABI provides better run-time introspection metadata and smaller
binaries. When used with the new ABI, this version of the runtime will consume
less memory than the previous release.

You may obtain the code for this release from git and use the 2.0 branch:

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

Alternatively, a tarball is available from:

https://github.com/gnustep/libobjc2/archive/v2.0.zip
https://github.com/gnustep/libobjc2/archive/v2.0.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

Assets 4

@davidchisnall davidchisnall released this Apr 26, 2019 · 260 commits to master since this release

This the ninth official 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:

  • Support for 64-bit ARM (AArch64) processors, including assembly fast paths
    for message sending.

  • Improved the dispatch table representation to improve performance and cache
    usage on the fast path.

  • The implementation of imp_implementationWithBlock, the function that allows
    blocks to be used as methods, no longer requires physical pages to be mapped
    both writeable and executable.

  • Numerous improvements to the interaction between runtime functions and ARC.

  • Support for Thumb-2 interworking on ARM. Note that the library must be
    compiled for ARMv7 or ARMv6T2 for this code to be enabled. Once it has been,
    other Objective-C binaries linked with the library can be compiled as ARM or
    Thumb-2 code. This will also generate Thumb-2 message send functions,
    improving instruction cache usage.

  • Significant improvements to ARC, including

    • The runtime no longer acquires a global lock on every object deallocation (a
      global lock is still used for objects that have weak references). NOTE:
      This is incompatible with other code directly inspecting the reference
      count and will break with older versions of GNUstep Base!

    • Weak references use a scheme closer to C++ std::weak_pointer and are
      lazily zeroed on access. This reduces the space overheads for weak
      references.

    • Some additional helper functions are added for use in NSObject and other
      root classes, which simplifies the layering between the runtime and the
      Foundation (or equivalent) implementation.

  • Improvements to how the runtime handles layout of ivars with strong alignment
    requirements, which should fix issues relating to using vector types in
    Objective-C objects.

  • The option to build a separate libobjcxx has been removed. The runtime will
    now depend on the C++ standard library implementation if no useable C++
    runtime is available. Note that C++ exception interworking does not work
    because LLVM's libc++abi (shipped by Apple) does not provide GNU-compatible
    hooks and so Objective-C++ exception support will be automatically disabled
    on this platform. Any other platforms shipping libc++abi should consider
    either GNU libsupc++ or libcxxrt as an alternative.

You may obtain the code for this release from git and use the 1.9 branch:

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

Alternatively, a tarball is available from:

https://github.com/gnustep/libobjc2/archive/v1.9.zip
https://github.com/gnustep/libobjc2/archive/v1.9.tar.gz

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

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

Assets 2

@davidchisnall davidchisnall released this Aug 7, 2015 · 4 commits to 1.8.1 since this release

This a bugfix release for the ninth official 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:

  • Better build system detection of LLVM not being present
  • Fix for a bug causing corruption of runtime state when hidden classes are
    deallocated.

You may obtain the code for this release from git and use the 1.8 branch:

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

Alternatively, a tarball is available from:

https://github.com/gnustep/libobjc2/archive/v1.8.zip
https://github.com/gnustep/libobjc2/archive/v1.8.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 Apple's Objective-C Runtime APIs, and a small number
of GCC APIs for legacy compatibility.

This library is based on the Étoilé Objective-C Runtime, an earlier research
prototype, and includes support for non-fragile instance variables,
type-dependent dispatch, and object planes. It is fully backwards compatible
with the FSF's GCC 4.2.1 Objective-C ABI and also implements a new ABI that is
supported by Clang and Étoilé's LanguageKit and is required for some of the
newer features.

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

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

Assets 2

@davidchisnall davidchisnall released this Jul 12, 2015 · 5 commits to 1.8 since this release

This the ninth official 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:

  • Added API for tracing, allowing interposition on all message sends matching a
    given selector.
  • Numerous bug fixes and stability improvements.

You may obtain the code for this release from git and use the 1.8 branch:

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

Alternatively, a tarball is available from:

https://github.com/gnustep/libobjc2/archive/v1.8.zip
https://github.com/gnustep/libobjc2/archive/v1.8.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 Apple's Objective-C Runtime APIs, and a small number
of GCC APIs for legacy compatibility.

This library is based on the Étoilé Objective-C Runtime, an earlier research
prototype, and includes support for non-fragile instance variables,
type-dependent dispatch, and object planes. It is fully backwards compatible
with the FSF's GCC 4.2.1 Objective-C ABI and also implements a new ABI that is
supported by Clang and Étoilé's LanguageKit and is required for some of the
newer features.

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

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

Assets 2
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