1 /* Basic data types for Objective C.
2 Copyright (C) 1993-2023 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
9 any later version.
10
11 GCC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 Under Section 7 of GPL version 3, you are granted additional
17 permissions described in the GCC Runtime Library Exception, version
18 3.1, as published by the Free Software Foundation.
19
20 You should have received a copy of the GNU General Public License and
21 a copy of the GCC Runtime Library Exception along with this program;
22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 <http://www.gnu.org/licenses/>. */
24
25 #ifndef __objc_INCLUDE_GNU
26 #define __objc_INCLUDE_GNU
27
28 /* This file contains the definition of the basic types used by the
29 Objective-C language. It needs to be included to do almost
30 anything with Objective-C. */
31
32 #ifdef __cplusplus
33 extern "C" {
34 #endif
35
36 #include <stddef.h>
37
38 /* The current version of the GNU Objective-C Runtime library in
39 compressed ISO date format. This should be updated any time a new
40 version is released with changes to the public API (there is no
41 need to update it if there were no API changes since the previous
42 release). This macro is only defined starting with the GNU
43 Objective-C Runtime shipped with GCC 4.6.0. If it is not defined,
44 it is either an older version of the runtime, or another runtime. */
45 #define __GNU_LIBOBJC__ 20110608
46
47 /* Definition of the boolean type.
48
49 Compatibility note: the Apple/NeXT runtime defines a BOOL as a
50 'signed char'. The GNU runtime uses an 'unsigned char'.
51
52 Important: this could change and we could switch to 'typedef bool
53 BOOL' in the future. Do not depend on the type of BOOL. */
54 #undef BOOL
55 typedef unsigned char BOOL;
56
57 #define YES (BOOL)1
58 #define NO (BOOL)0
59
60 /* The basic Objective-C types (SEL, Class, id) are defined as pointer
61 to opaque structures. The details of the structures are private to
62 the runtime and may potentially change from one version to the
63 other. */
64
65 /* A SEL (selector) represents an abstract method (in the
66 object-oriented sense) and includes all the details of how to
67 invoke the method (which means its name, arguments and return
68 types) but provides no implementation of its own. You can check
69 whether a class implements a selector or not, and if you have a
70 selector and know that the class implements it, you can use it to
71 call the method for an object in the class. */
72 typedef const struct objc_selector *SEL;
73
74 /* A Class is a class (in the object-oriented sense). In Objective-C
75 there is the complication that each Class is an object itself, and
76 so belongs to a class too. This class that a class belongs to is
77 called its 'meta class'. */
78 typedef struct objc_class *Class;
79
80 /* An 'id' is an object of an unknown class. The way the object data
81 is stored inside the object is private and what you see here is
82 only the beginning of the actual struct. The first field is always
83 a pointer to the Class that the object belongs to. */
84 typedef struct objc_object
85 {
86 /* 'class_pointer' is the Class that the object belongs to. In case
87 of a Class object, this pointer points to the meta class.
88
89 Compatibility Note: The Apple/NeXT runtime calls this field
90 'isa'. To access this field, use object_getClass() from
91 runtime.h, which is an inline function so does not add any
92 overhead and is also portable to other runtimes. */
93 Class class_pointer;
94 } *id;
95
96 /* 'IMP' is a C function that implements a method. When retrieving
97 the implementation of a method from the runtime, this is the type
98 of the pointer returned. The idea of the definition of IMP is to
99 represent a 'pointer to a general function taking an id, a SEL,
100 followed by other unspecified arguments'. You must always cast an
101 IMP to a pointer to a function taking the appropriate, specific
102 types for that function, before calling it - to make sure the
103 appropriate arguments are passed to it. The code generated by the
104 compiler to perform method calls automatically does this cast
105 inside method calls. */
106 typedef id (*IMP)(id, SEL, ...);
107
108 /* 'nil' is the null object. Messages to nil do nothing and always
109 return 0. */
110 #define nil (id)0
111
112 /* 'Nil' is the null class. Since classes are objects too, this is
113 actually the same object as 'nil' (and behaves in the same way),
114 but it has a type of Class, so it is good to use it instead of
115 'nil' if you are comparing a Class object to nil as it enables the
116 compiler to do some type-checking. */
117 #define Nil (Class)0
118
119 /* TODO: Move the 'Protocol' declaration into objc/runtime.h. A
120 Protocol is simply an object, not a basic Objective-C type. The
121 Apple runtime defines Protocol in objc/runtime.h too, so it's good
122 to move it there for API compatibility. */
123
124 /* A 'Protocol' is a formally defined list of selectors (normally
125 created using the @protocol Objective-C syntax). It is mostly used
126 at compile-time to check that classes implement all the methods
127 that they are supposed to. Protocols are also available in the
128 runtime system as Protocol objects. */
129 #ifndef __OBJC__
130 /* Once we stop including the deprecated struct_objc_protocol.h
131 there is no reason to even define a 'struct objc_protocol'. As
132 all the structure details will be hidden, a Protocol basically is
133 simply an object (as it should be). */
134 typedef struct objc_object Protocol;
135 #else /* __OBJC__ */
136 @class Protocol;
137 #endif
138
139 /* Compatibility note: the Apple/NeXT runtime defines sel_getName(),
140 sel_registerName(), object_getClassName(), object_getIndexedIvars()
141 in this file while the GNU runtime defines them in runtime.h.
142
143 The reason the GNU runtime does not define them here is that they
144 are not basic Objective-C types (defined in this file), but are
145 part of the runtime API (defined in runtime.h). */
146
147 #ifdef __cplusplus
148 }
149 #endif
150
151 #endif /* not __objc_INCLUDE_GNU */