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80 lines
4.0 KiB
Groff
80 lines
4.0 KiB
Groff
GNUstep Objective-C Runtime 1.4
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===============================
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This is the fifth official release of the GNUstep Objective-C runtime (a.k.a.
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libobjc2). This runtime was designed to support the features of Objective-C 2
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for use with GNUstep and other Objective-C programs. Highlights of this
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release include:
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- Support for the associated reference APIs introduced with OS X 10.6. This
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allows storing arbitrary objects associated with another object.
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- Concurrent, thread-safe, +initialize. The runtime will now send +initialize
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messages to different classes concurrently in multiple threads, but still
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ensures that no class receives another message until it has returned from
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+initialize. This mirrors OS X behaviour. Care must be taken that
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+initialize methods do not deadlock - if two classes are simultaneously
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initialised from two different threads, and there +initialize methods call
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methods in the other class, then deadlock will result.
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- Exceptions can now safely propagate out of +initialize methods.
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- Better hiding of local symbols. Now the internal runtime functions are not
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visible from outside of the runtime. This may break code that attempts to
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use private APIs, but means that it is now impossible to accidentally use
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private APIs.
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- Dispatch table updates have been improved. Category loading now longer
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triggers dtable creation and partial dtable updates are faster.
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- Improvements to the low memory profile. Uses 5-10% less (total) memory
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running Gorm, and now passes the entire GNUstep and EtoileFoundation test
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suites. Build with [g]make low_memory=yes to enable this mode. Note that
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the low memory profile trades some CPU time for memory usage, so don't use it
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for CPU-bound tasks.
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- The class lookup cache optimisation (LLVM) now caches lookups irrespective of
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the ABI. It will insert direct references to the class structures if
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possible (i.e. if the symbol is visible). If not, then it will cache the
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result of objc_class_lookup(). The cache is shared across the module (the
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library, if run as a link-time optimisation), so the lookup only needs to be
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run once. This eliminates the need for explicit class lookup caching in the
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source code (when using LLVM-based compilers, such as Clang, LanguageKit, or
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DragonEgg).
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- Added some missing runtime API functions, such as those for setting and
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getting instance variables. These are required by some language bridges,
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although using them safely is not actually possible with the non-fragile ABI
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(also true on OS X), since instance variables are no longer uniquely
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identified by name.
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- Added support for accessing property type encodings. These are extended type
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encodings, allowing code introspecting the properties to learn if they are
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read-only, their assignment policy, the methods used to implement them, and
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so on.
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You may obtain the code for this release from subversion at the following
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subversion branch:
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svn://svn.gna.org/svn/gnustep/libs/libobjc2/1.4
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Alternatively, a tarball is available from:
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http://download.gna.org/gnustep/libobjc2-1.4.tar.bz2
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The runtime library is responsible for implementing the core features of the
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object model, as well as exposing introspection features to the user. The
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GNUstep runtime implements Apple's Objective-C Runtime APIs, and a small number
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of GCC APIs for legacy compatibility.
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This library is based on the Étoilé Objective-C Runtime, an earlier research
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prototype, and includes support for non-fragile instance variables,
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type-dependent dispatch, and object planes. It is fully compatible with the
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FSF's GCC Objective-C ABI and also implements a new ABI that is supported by
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Clang and Étoilé's LanguageKit and is required for some of the newer features.
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Although the runtime has been tested by several people, and is being used
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extensively by the Étoilé project, it is entirely new (MIT licensed) code and
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may still contain bugs. If you come across any problems, please report them to
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the GNUstep Developer mailing list <gnustep-dev@gnu.org>.
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