1 2 GNU Objective C notes 3 ********************* 4 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. 10 11 This is not documentation for Objective C, it is usable to someone 12 who knows Objective C from somewhere else. 13 14 15 Runtime API functions 16 ===================== 17 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. 28 29 30 Protocols 31 ========= 32 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. 40 41 42 +load 43 =========== 44 This method, if defined, is called for each class and category 45 implementation when the class is loaded into the runtime. This method 46 is not inherited, and is thus not called for a subclass that doesn't 47 define it itself. Thus, each +load method is called exactly once by 48 the runtime. The runtime invocation of this method is thread safe. 49 50 51 +initialize 52 =========== 53 54 This method, if defined, is called before any other instance or class 55 methods of that particular class. For the GNU runtime, this method is 56 not inherited, and is thus not called as initializer for a subclass that 57 doesn't define it itself. Thus, each +initialize method is called exactly 58 once by the runtime (or never if no methods of that particular class is 59 never called). It is wise to guard against multiple invocations anyway 60 to remain portable with the NeXT runtime. The runtime invocation of 61 this method is thread safe. 62 63 64 Passivation/Activation/Typedstreams 65 =================================== 66 67 This is supported in the style of NeXT TypedStream's. Consult the 68 headerfile Typedstreams.h for api functions. I (Kresten) have 69 rewritten it in Objective C, but this implementation is not part of 70 2.4, it is available from the GNU Objective C prerelease archive. 71 There is one difference worth noting concerning objects stored with 72 objc_write_object_reference (aka NXWriteObjectReference). When these 73 are read back in, their object is not guaranteed to be available until 74 the `-awake' method is called in the object that requests that object. 75 To objc_read_object you must pass a pointer to an id, which is valid 76 after exit from the function calling it (like e.g. an instance 77 variable). In general, you should not use objects read in until the 78 -awake method is called. 79 80 81 Acknowledgements 82 ================ 83 84 The GNU Objective C team: Geoffrey Knauth <gsk (a] marble.com> (manager), 85 Tom Wood <wood (a] next.com> (compiler) and Kresten Krab Thorup 86 <krab (a] iesd.auc.dk> (runtime) would like to thank a some people for 87 participating in the development of the present GNU Objective C. 88 89 Paul Burchard <burchard (a] geom.umn.edu> and Andrew McCallum 90 <mccallum (a] cs.rochester.edu> has been very helpful debugging the 91 runtime. Eric Herring <herring (a] iesd.auc.dk> has been very helpful 92 cleaning up after the documentation-copyright disaster and is now 93 helping with the new documentation. 94 95 Steve Naroff <snaroff (a] next.com> and Richard Stallman 96 <rms (a] gnu.ai.mit.edu> has been very helpful with implementation details 97 in the compiler. 98 99 100 Bug Reports 101 =========== 102 103 Please read the section `Submitting Bugreports' of the gcc manual 104 before you submit any bugs. 105
Indexes created Fri Jun 05 00:26:10 UTC 2026