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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
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+
+GNU Objective C notes
+*********************
+
+This document is to explain what has been done, and a little about how
+specific features differ from other implementations. The runtime has
+been completely rewritten in gcc 2.4. The earlier runtime had several
+severe bugs and was rather incomplete. The compiler has had several
+new features added as well.
+
+This is not documentation for Objective C, it is usable to someone
+who knows Objective C from somewhere else.
+
+
+Runtime API functions
+=====================
+
+The runtime is modeled after the NeXT Objective C runtime. That is,
+most functions have semantics as it is known from the NeXT. The
+names, however, have changed. All runtime API functions have names
+of lowercase letters and underscores as opposed to the
+`traditional' mixed case names.
+ The runtime api functions are not documented as of now.
+Someone offered to write it, and did it, but we were not allowed to
+use it by his university (Very sad story). We have started writing
+the documentation over again. This will be announced in appropriate
+places when it becomes available.
+
+
+Protocols
+=========
+
+Protocols are now fully supported. The semantics is exactly as on the
+NeXT. There is a flag to specify how protocols should be typechecked
+when adopted to classes. The normal typechecker requires that all
+methods in a given protocol must be implemented in the class that
+adopts it -- it is not enough to inherit them. The flag
+`-Wno-protocol' causes it to allow inherited methods, while
+`-Wprotocols' is the default which requires them defined.
+
+
++load
+===========
+This method, if defined, is called for each class and category
+implementation when the class is loaded into the runtime. This method
+is not inherited, and is thus not called for a subclass that doesn't
+define it itself. Thus, each +load method is called exactly once by
+the runtime. The runtime invocation of this method is thread safe.
+
+
++initialize
+===========
+
+This method, if defined, is called before any other instance or class
+methods of that particular class. For the GNU runtime, this method is
+not inherited, and is thus not called as initializer for a subclass that
+doesn't define it itself. Thus, each +initialize method is called exactly
+once by the runtime (or never if no methods of that particular class is
+never called). It is wise to guard against multiple invocations anyway
+to remain portable with the NeXT runtime. The runtime invocation of
+this method is thread safe.
+
+
+Passivation/Activation/Typedstreams
+===================================
+
+This is supported in the style of NeXT TypedStream's. Consult the
+headerfile Typedstreams.h for api functions. I (Kresten) have
+rewritten it in Objective C, but this implementation is not part of
+2.4, it is available from the GNU Objective C prerelease archive.
+ There is one difference worth noting concerning objects stored with
+objc_write_object_reference (aka NXWriteObjectReference). When these
+are read back in, their object is not guaranteed to be available until
+the `-awake' method is called in the object that requests that object.
+To objc_read_object you must pass a pointer to an id, which is valid
+after exit from the function calling it (like e.g. an instance
+variable). In general, you should not use objects read in until the
+-awake method is called.
+
+
+Acknowledgements
+================
+
+The GNU Objective C team: Geoffrey Knauth <gsk@marble.com> (manager),
+Tom Wood <wood@next.com> (compiler) and Kresten Krab Thorup
+<krab@iesd.auc.dk> (runtime) would like to thank a some people for
+participating in the development of the present GNU Objective C.
+
+Paul Burchard <burchard@geom.umn.edu> and Andrew McCallum
+<mccallum@cs.rochester.edu> has been very helpful debugging the
+runtime. Eric Herring <herring@iesd.auc.dk> has been very helpful
+cleaning up after the documentation-copyright disaster and is now
+helping with the new documentation.
+
+Steve Naroff <snaroff@next.com> and Richard Stallman
+<rms@gnu.ai.mit.edu> has been very helpful with implementation details
+in the compiler.
+
+
+Bug Reports
+===========
+
+Please read the section `Submitting Bugreports' of the gcc manual
+before you submit any bugs.