1/* Basic data types for Objective C.
2   Copyright (C) 1993-2020 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify
7it under the terms of the GNU General Public License as published by
8the Free Software Foundation; either version 3, or (at your option)
9any later version.
10
11GCC is distributed in the hope that it will be useful,
12but WITHOUT ANY WARRANTY; without even the implied warranty of
13MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14GNU General Public License for more details.
15
16Under Section 7 of GPL version 3, you are granted additional
17permissions described in the GCC Runtime Library Exception, version
183.1, as published by the Free Software Foundation.
19
20You should have received a copy of the GNU General Public License and
21a copy of the GCC Runtime Library Exception along with this program;
22see 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
33extern "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
55typedef 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.  */
72typedef 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'.  */
78typedef 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.  */
84typedef 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.  */
106typedef 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 */
152