5 This document is to explain what has been done, and a little about how
6 specific features differ from other implementations. The runtime has
7 been completely rewritten in gcc 2.4. The earlier runtime had several
8 severe bugs and was rather incomplete. The compiler has had several
9 new features added as well.
11 This is not documentation for Objective C, it is usable to someone
12 who knows Objective C from somewhere else.
18 The runtime is modeled after the NeXT Objective C runtime. That is,
19 most functions have semantics as it is known from the NeXT. The
20 names, however, have changed. All runtime API functions have names
21 of lowercase letters and underscores as opposed to the
22 `traditional' mixed case names.
23 The runtime api functions are not documented as of now.
24 Someone offered to write it, and did it, but we were not allowed to
25 use it by his university (Very sad story). We have started writing
26 the documentation over again. This will be announced in appropriate
27 places when it becomes available.
33 Protocols are now fully supported. The semantics is exactly as on the
34 NeXT. There is a flag to specify how protocols should be typechecked
35 when adopted to classes. The normal typechecker requires that all
36 methods in a given protocol must be implemented in the class that
37 adopts it -- it is not enough to inherit them. The flag
38 `-Wno-protocol' causes it to allow inherited methods, while
39 `-Wprotocols' is the default which requires them defined.
45 This method, if defined, is called before any other instance or class
46 methods of that particular class. This method is not inherited, and
47 is thus not called as initializer for a subclass that doesn't define
48 it itself. Thus, each +initialize method is called exactly once (or
49 never if no methods of that particular class is never called).
50 Besides this, it is allowed to have several +initialize methods, one
51 for each category. The order in which these (multiple methods) are
52 called is not well defined. I am not completely certain what the
53 semantics of this method is for other implementations, but this is
54 how it works for GNU Objective C.
57 Passivation/Activation/Typedstreams
58 ===================================
60 This is supported in the style of NeXT TypedStream's. Consult the
61 headerfile Typedstreams.h for api functions. I (Kresten) have
62 rewritten it in Objective C, but this implementation is not part of
63 2.4, it is available from the GNU Objective C prerelease archive.
64 There is one difference worth noting concerning objects stored with
65 objc_write_object_reference (aka NXWriteObjectReference). When these
66 are read back in, their object is not guaranteed to be available until
67 the `-awake' method is called in the object that requests that object.
68 To objc_read_object you must pass a pointer to an id, which is valid
69 after exit from the function calling it (like e.g. an instance
70 variable). In general, you should not use objects read in until the
71 -awake method is called.
77 The GNU Objective C team: Geoffrey Knauth <gsk@marble.com> (manager),
78 Tom Wood <wood@next.com> (compiler) and Kresten Krab Thorup
79 <krab@iesd.auc.dk> (runtime) would like to thank a some people for
80 participating in the development of the present GNU Objective C.
82 Paul Burchard <burchard@geom.umn.edu> and Andrew McCallum
83 <mccallum@cs.rochester.edu> has been very helpful debugging the
84 runtime. Eric Herring <herring@iesd.auc.dk> has been very helpful
85 cleaning up after the documentation-copyright disaster and is now
86 helping with the new documentation.
88 Steve Naroff <snaroff@next.com> and Richard Stallman
89 <rms@gnu.ai.mit.edu> has been very helpful with implementation details
96 Please read the section `Submitting Bugreports' of the gcc manual
97 before you submit any bugs.
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