libobjc/objc/objc.h

   1 /* Basic data types for Objective C.
   2    Copyright (C) 1993, 1995, 1996, 2004, 2009,
   3    2010 Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 3, or (at your option)
  10 any later version.
  11
  12 GCC is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 Under Section 7 of GPL version 3, you are granted additional
  18 permissions described in the GCC Runtime Library Exception, version
  19 3.1, as published by the Free Software Foundation.
  20
  21 You should have received a copy of the GNU General Public License and
  22 a copy of the GCC Runtime Library Exception along with this program;
  23 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24 <http://www.gnu.org/licenses/>.  */
  25
  26 #ifndef __objc_INCLUDE_GNU
  27 #define __objc_INCLUDE_GNU
  28
  29 /* This file contains the definition of the basic types used by the
  30    Objective-C language.  It needs to be included to do almost
  31    anything with Objective-C.
  32 */
  33
  34 #ifdef __cplusplus
  35 extern "C" {
  36 #endif
  37
  38 #include <stddef.h>
  39
  40 /* The current version of the GNU Objective-C Runtime library in
  41    compressed ISO date format.  This should be updated any time a new
  42    version is released with changes to the public API (there is no
  43    need to update it if there were no API changes since the previous
  44    release).  This macro is only defined starting with the GNU
  45    Objective-C Runtime shipped with GCC 4.6.0.  If it is not defined,
  46    it is either an older version of the runtime, or another runtime.
  47 */
  48 #define __GNU_LIBOBJC__ 20100911
  49
  50 /*
  51   Definition of the boolean type.
  52
  53   Compatibility note: the Apple/NeXT runtime defines a BOOL as a
  54   'signed char'.  The GNU runtime uses an 'unsigned char'.
  55
  56   Important: this could change and we could switch to 'typedef bool
  57   BOOL' in the future.  Do not depend on the type of BOOL.
  58 */
  59 #undef BOOL
  60 typedef unsigned char  BOOL;
  61
  62 #define YES   (BOOL)1
  63 #define NO    (BOOL)0
  64
  65 /* The basic Objective-C types (SEL, Class, id) are defined as pointer
  66    to opaque structures.  The details of the structures are private to
  67    the runtime and may potentially change from one version to the
  68    other.
  69 */
  70
  71 /* A SEL (selector) represents an abstract method (in the
  72    object-oriented sense) and includes all the details of how to
  73    invoke the method (which means its name, arguments and return
  74    types) but provides no implementation of its own.  You can check
  75    whether a class implements a selector or not, and if you have a
  76    selector and know that the class implements it, you can use it to
  77    call the method for an object in the class.
  78  */
  79 typedef const struct objc_selector *SEL;
  80 #include "deprecated/struct_objc_selector.h"
  81
  82 /* A Class is a class (in the object-oriented sense).  In Objective-C
  83    there is the complication that each Class is an object itself, and
  84    so belongs to a class too.  This class that a class belongs to is
  85    called its 'meta class'.
  86 */
  87 typedef struct objc_class *Class;
  88 #include "deprecated/MetaClass.h"
  89 #include "deprecated/struct_objc_class.h"
  90
  91 /* An 'id' is an object of an unknown class.  The struct objc_object
  92    is private and what you see here is only the beginning of the
  93    struct.  In theory, the fact that 'class_pointer' is public means
  94    that if you have any object 'object', you can immediately get its
  95    class by using '((id)object)->class_pointer', but this is not
  96    recommended; you should use object_get_class(object) instead.
  97 */
  98 typedef struct objc_object
  99 {
 100   /* 'class_pointer' is the Class that the object belongs to.  In case
 101      of a Class object, this pointer points to the meta class.  */
 102   /* Note that the Apple/NeXT runtime calls this variable 'isa'.
 103      TODO: Decide if we want to call it 'isa' too.  TODO: Why not
 104      simply hide this pointer and force users to use the proper API to
 105      get it ?
 106   */
 107   Class class_pointer;
 108 } *id;
 109
 110 /*
 111   'IMP' is a C function that implements a method.  When retrieving the
 112   implementation of a method from the runtime, this is the type of the
 113   pointer returned.  The idea of the definition of IMP is to represent
 114   a 'pointer to a general function taking an id, a SEL, followed by
 115   other unspecified arguments'.  You must always cast an IMP to a
 116   pointer to a function taking the appropriate, specific types for
 117   that function, before calling it - to make sure the appropriate
 118   arguments are passed to it.  The code generated by the compiler to
 119   perform method calls automatically does this cast inside method
 120   calls.
 121 */
 122 typedef id (*IMP)(id, SEL, ...);
 123
 124 /* 'nil' is the null object.  Messages to nil do nothing and always
 125    return 0.  */
 126 #define nil (id)0
 127
 128 /* 'Nil' is the null class.  Since classes are objects too, this is
 129    actually the same object as 'nil' (and behaves in the same way),
 130    but it has a type of Class, so it is good to use it instead of
 131    'nil' if you are comparing a Class object to nil as it enables the
 132    compiler to do some type-checking.  */
 133 #define Nil (Class)0
 134
 135 #include "deprecated/STR.h"
 136
 137 /* TODO: Move the 'Protocol' declaration into objc/runtime.h.  A
 138    Protocol is simply an object, not a basic Objective-C type.  The
 139    Apple runtime defines Protocol in objc/runtime.h too, so it's good
 140    to move it there for API compatibility.
 141 */
 142
 143 /* A 'Protocol' is a formally defined list of selectors (normally
 144    created using the @protocol Objective-C syntax).  It is mostly used
 145    at compile-time to check that classes implement all the methods
 146    that they are supposed to.  Protocols are also available in the
 147    runtime system as Protocol objects.
 148  */
 149 #ifndef __OBJC__
 150   /* Once we stop including the deprecated struct_objc_protocol.h
 151      there is no reason to even define a 'struct objc_protocol'.  As
 152      all the structure details will be hidden, a Protocol basically is
 153      simply an object (as it should be).
 154    */
 155   /* typedef struct objc_object Protocol; */
 156   #include "deprecated/struct_objc_protocol.h"
 157 #else /* __OBJC__ */
 158   @class Protocol;
 159 #endif
 160
 161 /* Deprecated include - here temporarily, for backwards-compatibility
 162    as reval_t, apply_t, arglist_t and objc_msg_lookup() used to be
 163    defined here.  */
 164 #include "message.h"
 165
 166 /* Compatibility note: the Apple/NeXT runtime defines sel_getName(),
 167    sel_registerName(), object_getClassName(), object_getIndexedIvars()
 168    in this file while the GNU runtime defines them in runtime.h.
 169
 170    The reason the GNU runtime does not define them here is that they
 171    are not basic Objective-C types (defined in this file), but are
 172    part of the runtime API (defined in runtime.h).
 173 */
 174
 175 #ifdef __cplusplus
 176 }
 177 #endif
 178
 179 #endif /* not __objc_INCLUDE_GNU */