1 /* Basic data types for Objective C. 2 Copyright (C) 1993-2021 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 */ 152