libkern/os/base.h

   1 /*
   2  * Copyright (c) 2008-2013 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_APACHE_LICENSE_HEADER_START@
   5  *
   6  * Licensed under the Apache License, Version 2.0 (the "License");
   7  * you may not use this file except in compliance with the License.
   8  * You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  *
  18  * @APPLE_APACHE_LICENSE_HEADER_END@
  19  */
  20
  21 #ifndef __OS_BASE__
  22 #define __OS_BASE__
  23
  24 #include <sys/cdefs.h>
  25
  26 #ifndef __has_builtin
  27 #define __has_builtin(x) 0
  28 #endif
  29 #ifndef __has_include
  30 #define __has_include(x) 0
  31 #endif
  32 #ifndef __has_feature
  33 #define __has_feature(x) 0
  34 #endif
  35 #ifndef __has_attribute
  36 #define __has_attribute(x) 0
  37 #endif
  38 #ifndef __has_extension
  39 #define __has_extension(x) 0
  40 #endif
  41
  42 #undef OS_INLINE // <sys/_types/_os_inline.h>
  43 #if __GNUC__
  44 #define OS_NORETURN __attribute__((__noreturn__))
  45 #define OS_NOTHROW __attribute__((__nothrow__))
  46 #define OS_NONNULL1 __attribute__((__nonnull__(1)))
  47 #define OS_NONNULL2 __attribute__((__nonnull__(2)))
  48 #define OS_NONNULL3 __attribute__((__nonnull__(3)))
  49 #define OS_NONNULL4 __attribute__((__nonnull__(4)))
  50 #define OS_NONNULL5 __attribute__((__nonnull__(5)))
  51 #define OS_NONNULL6 __attribute__((__nonnull__(6)))
  52 #define OS_NONNULL7 __attribute__((__nonnull__(7)))
  53 #define OS_NONNULL8 __attribute__((__nonnull__(8)))
  54 #define OS_NONNULL9 __attribute__((__nonnull__(9)))
  55 #define OS_NONNULL10 __attribute__((__nonnull__(10)))
  56 #define OS_NONNULL11 __attribute__((__nonnull__(11)))
  57 #define OS_NONNULL12 __attribute__((__nonnull__(12)))
  58 #define OS_NONNULL13 __attribute__((__nonnull__(13)))
  59 #define OS_NONNULL14 __attribute__((__nonnull__(14)))
  60 #define OS_NONNULL15 __attribute__((__nonnull__(15)))
  61 #define OS_NONNULL_ALL __attribute__((__nonnull__))
  62 #define OS_SENTINEL __attribute__((__sentinel__))
  63 #define OS_PURE __attribute__((__pure__))
  64 #define OS_CONST __attribute__((__const__))
  65 #define OS_WARN_RESULT __attribute__((__warn_unused_result__))
  66 #define OS_MALLOC __attribute__((__malloc__))
  67 #define OS_USED __attribute__((__used__))
  68 #define OS_UNUSED __attribute__((__unused__))
  69 #define OS_COLD __attribute__((__cold__))
  70 #define OS_WEAK __attribute__((__weak__))
  71 #define OS_WEAK_IMPORT __attribute__((__weak_import__))
  72 #define OS_NOINLINE __attribute__((__noinline__))
  73 #define OS_ALWAYS_INLINE __attribute__((__always_inline__))
  74 #define OS_TRANSPARENT_UNION __attribute__((__transparent_union__))
  75 #define OS_ALIGNED(n) __attribute__((__aligned__((n))))
  76 #define OS_FORMAT_PRINTF(x, y) __attribute__((__format__(printf,x,y)))
  77 #define OS_EXPORT extern __attribute__((__visibility__("default")))
  78 #define OS_INLINE static __inline__
  79 #define OS_EXPECT(x, v) __builtin_expect((x), (v))
  80 #else
  81 #define OS_NORETURN
  82 #define OS_NOTHROW
  83 #define OS_NONNULL1
  84 #define OS_NONNULL2
  85 #define OS_NONNULL3
  86 #define OS_NONNULL4
  87 #define OS_NONNULL5
  88 #define OS_NONNULL6
  89 #define OS_NONNULL7
  90 #define OS_NONNULL8
  91 #define OS_NONNULL9
  92 #define OS_NONNULL10
  93 #define OS_NONNULL11
  94 #define OS_NONNULL12
  95 #define OS_NONNULL13
  96 #define OS_NONNULL14
  97 #define OS_NONNULL15
  98 #define OS_NONNULL_ALL
  99 #define OS_SENTINEL
 100 #define OS_PURE
 101 #define OS_CONST
 102 #define OS_WARN_RESULT
 103 #define OS_MALLOC
 104 #define OS_USED
 105 #define OS_UNUSED
 106 #define OS_COLD
 107 #define OS_WEAK
 108 #define OS_WEAK_IMPORT
 109 #define OS_NOINLINE
 110 #define OS_ALWAYS_INLINE
 111 #define OS_TRANSPARENT_UNION
 112 #define OS_ALIGNED(n)
 113 #define OS_FORMAT_PRINTF(x, y)
 114 #define OS_EXPORT extern
 115 #define OS_INLINE static inline
 116 #define OS_EXPECT(x, v) (x)
 117 #endif
 118
 119 #if __has_attribute(noescape)
 120 #define OS_NOESCAPE __attribute__((__noescape__))
 121 #else
 122 #define OS_NOESCAPE
 123 #endif
 124
 125 #if defined(__cplusplus) && defined(__clang__)
 126 #define OS_FALLTHROUGH [[clang::fallthrough]]
 127 #else
 128 #define OS_FALLTHROUGH
 129 #endif
 130
 131 #if __has_feature(assume_nonnull)
 132 #define OS_ASSUME_NONNULL_BEGIN _Pragma("clang assume_nonnull begin")
 133 #define OS_ASSUME_NONNULL_END   _Pragma("clang assume_nonnull end")
 134 #else
 135 #define OS_ASSUME_NONNULL_BEGIN
 136 #define OS_ASSUME_NONNULL_END
 137 #endif
 138
 139 #if __has_builtin(__builtin_assume)
 140 #define OS_COMPILER_CAN_ASSUME(expr) __builtin_assume(expr)
 141 #else
 142 #define OS_COMPILER_CAN_ASSUME(expr) ((void)(expr))
 143 #endif
 144
 145 #if __has_extension(attribute_overloadable)
 146 #define OS_OVERLOADABLE __attribute__((__overloadable__))
 147 #else
 148 #define OS_OVERLOADABLE
 149 #endif
 150
 151 #if __has_attribute(enum_extensibility)
 152 #define __OS_ENUM_ATTR __attribute__((enum_extensibility(open)))
 153 #define __OS_ENUM_ATTR_CLOSED __attribute__((enum_extensibility(closed)))
 154 #else
 155 #define __OS_ENUM_ATTR
 156 #define __OS_ENUM_ATTR_CLOSED
 157 #endif // __has_attribute(enum_extensibility)
 158
 159 #if __has_attribute(flag_enum)
 160 /*!
 161  * Compile with -Wflag-enum and -Wassign-enum to enforce at definition and
 162  * assignment, respectively, i.e. -Wflag-enum prevents you from creating new
 163  * enumeration values from illegal values within the enum definition, and
 164  * -Wassign-enum prevents you from assigning illegal values to a variable of the
 165  * enum type.
 166  */
 167 #define __OS_OPTIONS_ATTR __attribute__((flag_enum))
 168 #else
 169 #define __OS_OPTIONS_ATTR
 170 #endif // __has_attribute(flag_enum)
 171
 172 #if __has_feature(objc_fixed_enum) || __has_extension(cxx_fixed_enum) || \
 173         __has_extension(cxx_strong_enums)
 174 #define OS_ENUM(_name, _type, ...) \
 175                 typedef enum : _type { __VA_ARGS__ } _name##_t
 176 #define OS_CLOSED_ENUM(_name, _type, ...) \
 177                 typedef enum : _type { __VA_ARGS__ } \
 178                         __OS_ENUM_ATTR_CLOSED _name##_t
 179 #define OS_OPTIONS(_name, _type, ...) \
 180                 typedef enum : _type { __VA_ARGS__ } \
 181                         __OS_ENUM_ATTR __OS_OPTIONS_ATTR _name##_t
 182 #define OS_CLOSED_OPTIONS(_name, _type, ...) \
 183                 typedef enum : _type { __VA_ARGS__ } \
 184                         __OS_ENUM_ATTR_CLOSED __OS_OPTIONS_ATTR _name##_t
 185 #else
 186 /*!
 187  * There is unfortunately no good way in plain C to have both fixed-type enums
 188  * and enforcement for clang's enum_extensibility extensions. The primary goal
 189  * of these macros is to allow you to define an enum and specify its width in a
 190  * single statement, and for plain C that is accomplished by defining an
 191  * anonymous enum and then separately typedef'ing the requested type name to the
 192  * requested underlying integer type. So the type emitted actually has no
 193  * relationship at all to the enum, and therefore while the compiler could
 194  * enforce enum extensibility if you used the enum type, it cannot do so if you
 195  * use the "_t" type resulting from this expression.
 196  *
 197  * But we still define a named enum type and decorate it appropriately for you,
 198  * so if you really want the enum extensibility enforcement, you can use the
 199  * enum type yourself, i.e. when compiling with a C compiler:
 200  *
 201  *     OS_CLOSED_ENUM(my_type, uint64_t,
 202  *         FOO,
 203  *         BAR,
 204  *         BAZ,
 205  *     );
 206  *
 207  *     my_type_t mt = 98; // legal
 208  *     enum my_type emt = 98; // illegal
 209  *
 210  * But be aware that the underlying enum type's width is subject only to the C
 211  * language's guarantees -- namely that it will be compatible with int, char,
 212  * and unsigned char. It is not safe to rely on the size of this type.
 213  *
 214  * When compiling in ObjC or C++, both of the above assignments are illegal.
 215  */
 216 #define __OS_ENUM_C_FALLBACK(_name, _type, ...) \
 217                 typedef _type _name##_t; enum _name { __VA_ARGS__ }
 218
 219 #define OS_ENUM(_name, _type, ...) \
 220                 typedef _type _name##_t; enum { __VA_ARGS__ }
 221 #define OS_CLOSED_ENUM(_name, _type, ...) \
 222                 __OS_ENUM_C_FALLBACK(_name, _type, ## __VA_ARGS__) \
 223                 __OS_ENUM_ATTR_CLOSED
 224 #define OS_OPTIONS(_name, _type, ...) \
 225                 __OS_ENUM_C_FALLBACK(_name, _type, ## __VA_ARGS__) \
 226                 __OS_ENUM_ATTR __OS_OPTIONS_ATTR
 227 #define OS_CLOSED_OPTIONS(_name, _type, ...) \
 228                 __OS_ENUM_C_FALLBACK(_name, _type, ## __VA_ARGS__) \
 229                 __OS_ENUM_ATTR_CLOSED __OS_OPTIONS_ATTR
 230 #endif // __has_feature(objc_fixed_enum) || __has_extension(cxx_strong_enums)
 231
 232 #if __has_feature(attribute_availability_swift)
 233 // equivalent to __SWIFT_UNAVAILABLE from Availability.h
 234 #define OS_SWIFT_UNAVAILABLE(_msg) \
 235                 __attribute__((__availability__(swift, unavailable, message=_msg)))
 236 #else
 237 #define OS_SWIFT_UNAVAILABLE(_msg)
 238 #endif
 239
 240 #if __has_attribute(swift_private)
 241 # define OS_REFINED_FOR_SWIFT __attribute__((__swift_private__))
 242 #else
 243 # define OS_REFINED_FOR_SWIFT
 244 #endif
 245
 246 #if __has_attribute(swift_name)
 247 # define OS_SWIFT_NAME(_name) __attribute__((__swift_name__(#_name)))
 248 #else
 249 # define OS_SWIFT_NAME(_name)
 250 #endif
 251
 252 #define __OS_STRINGIFY(s) #s
 253 #define OS_STRINGIFY(s) __OS_STRINGIFY(s)
 254 #define __OS_CONCAT(x, y) x ## y
 255 #define OS_CONCAT(x, y) __OS_CONCAT(x, y)
 256
 257 #ifdef __GNUC__
 258 #define os_prevent_tail_call_optimization()  __asm__("")
 259 #define os_is_compile_time_constant(expr)  __builtin_constant_p(expr)
 260 #ifndef KERNEL
 261 #define os_compiler_barrier()  __asm__ __volatile__("" ::: "memory")
 262 #endif
 263 #else
 264 #define os_prevent_tail_call_optimization()  do { } while (0)
 265 #define os_is_compile_time_constant(expr)  0
 266 #ifndef KERNEL
 267 #define os_compiler_barrier()  do { } while (0)
 268 #endif
 269 #endif
 270
 271 #if __has_attribute(not_tail_called)
 272 #define OS_NOT_TAIL_CALLED __attribute__((__not_tail_called__))
 273 #else
 274 #define OS_NOT_TAIL_CALLED
 275 #endif
 276
 277 /*
 278  * LIBKERN_ALWAYS_DESTROY attribute can be applied to global variables with
 279  * destructors. It specifies that and object should have its exit-time
 280  * destructor run. This attribute is the default unless clang was invoked with
 281  * -fno-c++-static-destructors.
 282  */
 283 #if __has_attribute(always_destroy)
 284 #define LIBKERN_ALWAYS_DESTROY __attribute__((always_destroy))
 285 #else
 286 #define LIBKERN_ALWAYS_DESTROY
 287 #endif
 288
 289 typedef void (*os_function_t)(void *_Nullable);
 290
 291 #ifdef __BLOCKS__
 292 /*!
 293  * @typedef os_block_t
 294  *
 295  * @abstract
 296  * Generic type for a block taking no arguments and returning no value.
 297  *
 298  * @discussion
 299  * When not building with Objective-C ARC, a block object allocated on or
 300  * copied to the heap must be released with a -[release] message or the
 301  * Block_release() function.
 302  *
 303  * The declaration of a block literal allocates storage on the stack.
 304  * Therefore, this is an invalid construct:
 305  * <code>
 306  * os_block_t block;
 307  * if (x) {
 308  *     block = ^{ printf("true\n"); };
 309  * } else {
 310  *     block = ^{ printf("false\n"); };
 311  * }
 312  * block(); // unsafe!!!
 313  * </code>
 314  *
 315  * What is happening behind the scenes:
 316  * <code>
 317  * if (x) {
 318  *     struct Block __tmp_1 = ...; // setup details
 319  *     block = &__tmp_1;
 320  * } else {
 321  *     struct Block __tmp_2 = ...; // setup details
 322  *     block = &__tmp_2;
 323  * }
 324  * </code>
 325  *
 326  * As the example demonstrates, the address of a stack variable is escaping the
 327  * scope in which it is allocated. That is a classic C bug.
 328  *
 329  * Instead, the block literal must be copied to the heap with the Block_copy()
 330  * function or by sending it a -[copy] message.
 331  */
 332 typedef void (^os_block_t)(void);
 333 #endif
 334
 335 #endif // __OS_BASE__