runtime/objc-internal.h

   1 /*
   2  * Copyright (c) 2009 Apple Inc.  All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24
  25 #ifndef _OBJC_INTERNAL_H
  26 #define _OBJC_INTERNAL_H
  27
  28 /*
  29  * WARNING  DANGER  HAZARD  BEWARE  EEK
  30  *
  31  * Everything in this file is for Apple Internal use only.
  32  * These will change in arbitrary OS updates and in unpredictable ways.
  33  * When your program breaks, you get to keep both pieces.
  34  */
  35
  36 /*
  37  * objc-internal.h: Private SPI for use by other system frameworks.
  38  */
  39
  40 #include <objc/objc.h>
  41 #include <objc/runtime.h>
  42 #include <Availability.h>
  43 #include <malloc/malloc.h>
  44 #include <dispatch/dispatch.h>
  45
  46 __BEGIN_DECLS
  47
  48 // Termination reasons in the OS_REASON_OBJC namespace.
  49 #define OBJC_EXIT_REASON_UNSPECIFIED 1
  50 #define OBJC_EXIT_REASON_GC_NOT_SUPPORTED 2
  51
  52 // This is the allocation size required for each of the class and the metaclass
  53 // with objc_initializeClassPair() and objc_readClassPair().
  54 // The runtime's class structure will never grow beyond this.
  55 #define OBJC_MAX_CLASS_SIZE (32*sizeof(void*))
  56
  57 // In-place construction of an Objective-C class.
  58 // cls and metacls must each be OBJC_MAX_CLASS_SIZE bytes.
  59 // Returns nil if a class with the same name already exists.
  60 // Returns nil if the superclass is under construction.
  61 // Call objc_registerClassPair() when you are done.
  62 OBJC_EXPORT Class objc_initializeClassPair(Class superclass, const char *name, Class cls, Class metacls)
  63     OBJC_AVAILABLE(10.6, 3.0, 9.0, 1.0);
  64
  65 // Class and metaclass construction from a compiler-generated memory image.
  66 // cls and cls->isa must each be OBJC_MAX_CLASS_SIZE bytes.
  67 // Extra bytes not used the the metadata must be zero.
  68 // info is the same objc_image_info that would be emitted by a static compiler.
  69 // Returns nil if a class with the same name already exists.
  70 // Returns nil if the superclass is nil and the class is not marked as a root.
  71 // Returns nil if the superclass is under construction.
  72 // Do not call objc_registerClassPair().
  73 #if __OBJC2__
  74 struct objc_image_info;
  75 OBJC_EXPORT Class objc_readClassPair(Class cls,
  76                                      const struct objc_image_info *info)
  77     OBJC_AVAILABLE(10.10, 8.0, 9.0, 1.0);
  78 #endif
  79
  80 // Batch object allocation using malloc_zone_batch_malloc().
  81 OBJC_EXPORT unsigned class_createInstances(Class cls, size_t extraBytes,
  82                                            id *results, unsigned num_requested)
  83     OBJC_AVAILABLE(10.7, 4.3, 9.0, 1.0)
  84     OBJC_ARC_UNAVAILABLE;
  85
  86 // Get the isa pointer written into objects just before being freed.
  87 OBJC_EXPORT Class _objc_getFreedObjectClass(void)
  88     OBJC_AVAILABLE(10.0, 2.0, 9.0, 1.0);
  89
  90 // env NSObjCMessageLoggingEnabled
  91 OBJC_EXPORT void instrumentObjcMessageSends(BOOL flag)
  92     OBJC_AVAILABLE(10.0, 2.0, 9.0, 1.0);
  93
  94 // Initializer called by libSystem
  95 OBJC_EXPORT void _objc_init(void)
  96 #if __OBJC2__
  97     OBJC_AVAILABLE(10.8, 6.0, 9.0, 1.0);
  98 #else
  99     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0);
 100 #endif
 101
 102 // fork() safety called by libSystem
 103 OBJC_EXPORT void _objc_atfork_prepare(void)
 104     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0);
 105 OBJC_EXPORT void _objc_atfork_parent(void)
 106     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0);
 107 OBJC_EXPORT void _objc_atfork_child(void)
 108     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0);
 109
 110 // Return YES if GC is on and `object` is a GC allocation.
 111 OBJC_EXPORT BOOL objc_isAuto(id object)
 112     __OSX_DEPRECATED(10.4, 10.8, "it always returns NO")
 113     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE __WATCHOS_UNAVAILABLE;
 114
 115 // GC startup callback from Foundation
 116 OBJC_EXPORT malloc_zone_t *objc_collect_init(int (*callback)(void))
 117     __OSX_DEPRECATED(10.4, 10.8, "it does nothing")
 118     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE __WATCHOS_UNAVAILABLE;
 119
 120 // Plainly-implemented GC barriers. Rosetta used to use these.
 121 OBJC_EXPORT id objc_assign_strongCast_generic(id value, id *dest)
 122     UNAVAILABLE_ATTRIBUTE;
 123 OBJC_EXPORT id objc_assign_global_generic(id value, id *dest)
 124     UNAVAILABLE_ATTRIBUTE;
 125 OBJC_EXPORT id objc_assign_threadlocal_generic(id value, id *dest)
 126     UNAVAILABLE_ATTRIBUTE;
 127 OBJC_EXPORT id objc_assign_ivar_generic(id value, id dest, ptrdiff_t offset)
 128     UNAVAILABLE_ATTRIBUTE;
 129
 130 // GC preflight for an app executable.
 131 // 1: some slice requires GC
 132 // 0: no slice requires GC
 133 // -1: I/O or file format error
 134 OBJC_EXPORT int objc_appRequiresGC(int fd)
 135     __OSX_AVAILABLE(10.11)
 136     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE __WATCHOS_UNAVAILABLE;
 137
 138 // Install missing-class callback. Used by the late unlamented ZeroLink.
 139 OBJC_EXPORT void _objc_setClassLoader(BOOL (*newClassLoader)(const char *))  OBJC2_UNAVAILABLE;
 140
 141 // Install handler for allocation failures.
 142 // Handler may abort, or throw, or provide an object to return.
 143 OBJC_EXPORT void _objc_setBadAllocHandler(id (*newHandler)(Class isa))
 144     OBJC_AVAILABLE(10.8, 6.0, 9.0, 1.0);
 145
 146 // This can go away when AppKit stops calling it (rdar://7811851)
 147 #if __OBJC2__
 148 OBJC_EXPORT void objc_setMultithreaded (BOOL flag)
 149     __OSX_DEPRECATED(10.0, 10.5, "multithreading is always available")
 150     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE __WATCHOS_UNAVAILABLE;
 151 #endif
 152
 153 // Used by ExceptionHandling.framework
 154 #if !__OBJC2__
 155 OBJC_EXPORT void _objc_error(id rcv, const char *fmt, va_list args)
 156     __attribute__((noreturn))
 157     __OSX_DEPRECATED(10.0, 10.5, "use other logging facilities instead")
 158     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE __WATCHOS_UNAVAILABLE;
 159
 160 #endif
 161
 162
 163 // Tagged pointer objects.
 164
 165 #if __LP64__
 166 #define OBJC_HAVE_TAGGED_POINTERS 1
 167 #endif
 168
 169 #if OBJC_HAVE_TAGGED_POINTERS
 170
 171 // Tagged pointer layout and usage is subject to change on different OS versions.
 172
 173 // Tag indexes 0..<7 have a 60-bit payload.
 174 // Tag index 7 is reserved.
 175 // Tag indexes 8..<264 have a 52-bit payload.
 176 // Tag index 264 is reserved.
 177
 178 #if __has_feature(objc_fixed_enum)  ||  __cplusplus >= 201103L
 179 enum objc_tag_index_t : uint16_t
 180 #else
 181 typedef uint16_t objc_tag_index_t;
 182 enum
 183 #endif
 184 {
 185     OBJC_TAG_NSAtom            = 0,
 186     OBJC_TAG_1                 = 1,
 187     OBJC_TAG_NSString          = 2,
 188     OBJC_TAG_NSNumber          = 3,
 189     OBJC_TAG_NSIndexPath       = 4,
 190     OBJC_TAG_NSManagedObjectID = 5,
 191     OBJC_TAG_NSDate            = 6,
 192     OBJC_TAG_RESERVED_7        = 7,
 193
 194     OBJC_TAG_First60BitPayload = 0,
 195     OBJC_TAG_Last60BitPayload  = 6,
 196     OBJC_TAG_First52BitPayload = 8,
 197     OBJC_TAG_Last52BitPayload  = 263,
 198
 199     OBJC_TAG_RESERVED_264      = 264
 200 };
 201 #if __has_feature(objc_fixed_enum)  &&  !defined(__cplusplus)
 202 typedef enum objc_tag_index_t objc_tag_index_t;
 203 #endif
 204
 205
 206 // Returns true if tagged pointers are enabled.
 207 // The other functions below must not be called if tagged pointers are disabled.
 208 static inline bool
 209 _objc_taggedPointersEnabled(void);
 210
 211 // Register a class for a tagged pointer tag.
 212 // Aborts if the tag is invalid or already in use.
 213 OBJC_EXPORT void _objc_registerTaggedPointerClass(objc_tag_index_t tag, Class cls)
 214     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0);
 215
 216 // Returns the registered class for the given tag.
 217 // Returns nil if the tag is valid but has no registered class.
 218 // Aborts if the tag is invalid.
 219 OBJC_EXPORT Class _objc_getClassForTag(objc_tag_index_t tag)
 220     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0);
 221
 222 // Create a tagged pointer object with the given tag and payload.
 223 // Assumes the tag is valid.
 224 // Assumes tagged pointers are enabled.
 225 // The payload will be silently truncated to fit.
 226 static inline void *
 227 _objc_makeTaggedPointer(objc_tag_index_t tag, uintptr_t payload);
 228
 229 // Return true if ptr is a tagged pointer object.
 230 // Does not check the validity of ptr's class.
 231 static inline bool
 232 _objc_isTaggedPointer(const void *ptr);
 233
 234 // Extract the tag value from the given tagged pointer object.
 235 // Assumes ptr is a valid tagged pointer object.
 236 // Does not check the validity of ptr's tag.
 237 static inline objc_tag_index_t
 238 _objc_getTaggedPointerTag(const void *ptr);
 239
 240 // Extract the payload from the given tagged pointer object.
 241 // Assumes ptr is a valid tagged pointer object.
 242 // The payload value is zero-extended.
 243 static inline uintptr_t
 244 _objc_getTaggedPointerValue(const void *ptr);
 245
 246 // Extract the payload from the given tagged pointer object.
 247 // Assumes ptr is a valid tagged pointer object.
 248 // The payload value is sign-extended.
 249 static inline intptr_t
 250 _objc_getTaggedPointerSignedValue(const void *ptr);
 251
 252 // Don't use the values below. Use the declarations above.
 253
 254 #if TARGET_OS_OSX && __x86_64__
 255     // 64-bit Mac - tag bit is LSB
 256 #   define OBJC_MSB_TAGGED_POINTERS 0
 257 #else
 258     // Everything else - tag bit is MSB
 259 #   define OBJC_MSB_TAGGED_POINTERS 1
 260 #endif
 261
 262 #define _OBJC_TAG_INDEX_MASK 0x7
 263 // array slot includes the tag bit itself
 264 #define _OBJC_TAG_SLOT_COUNT 16
 265 #define _OBJC_TAG_SLOT_MASK 0xf
 266
 267 #define _OBJC_TAG_EXT_INDEX_MASK 0xff
 268 // array slot has no extra bits
 269 #define _OBJC_TAG_EXT_SLOT_COUNT 256
 270 #define _OBJC_TAG_EXT_SLOT_MASK 0xff
 271
 272 #if OBJC_MSB_TAGGED_POINTERS
 273 #   define _OBJC_TAG_MASK (1ULL<<63)
 274 #   define _OBJC_TAG_INDEX_SHIFT 60
 275 #   define _OBJC_TAG_SLOT_SHIFT 60
 276 #   define _OBJC_TAG_PAYLOAD_LSHIFT 4
 277 #   define _OBJC_TAG_PAYLOAD_RSHIFT 4
 278 #   define _OBJC_TAG_EXT_MASK (0xfULL<<60)
 279 #   define _OBJC_TAG_EXT_INDEX_SHIFT 52
 280 #   define _OBJC_TAG_EXT_SLOT_SHIFT 52
 281 #   define _OBJC_TAG_EXT_PAYLOAD_LSHIFT 12
 282 #   define _OBJC_TAG_EXT_PAYLOAD_RSHIFT 12
 283 #else
 284 #   define _OBJC_TAG_MASK 1
 285 #   define _OBJC_TAG_INDEX_SHIFT 1
 286 #   define _OBJC_TAG_SLOT_SHIFT 0
 287 #   define _OBJC_TAG_PAYLOAD_LSHIFT 0
 288 #   define _OBJC_TAG_PAYLOAD_RSHIFT 4
 289 #   define _OBJC_TAG_EXT_MASK 0xfULL
 290 #   define _OBJC_TAG_EXT_INDEX_SHIFT 4
 291 #   define _OBJC_TAG_EXT_SLOT_SHIFT 4
 292 #   define _OBJC_TAG_EXT_PAYLOAD_LSHIFT 0
 293 #   define _OBJC_TAG_EXT_PAYLOAD_RSHIFT 12
 294 #endif
 295
 296 static inline bool
 297 _objc_taggedPointersEnabled(void)
 298 {
 299     extern uintptr_t objc_debug_taggedpointer_mask;
 300     return (objc_debug_taggedpointer_mask != 0);
 301 }
 302
 303 static inline void *
 304 _objc_makeTaggedPointer(objc_tag_index_t tag, uintptr_t value)
 305 {
 306     // PAYLOAD_LSHIFT and PAYLOAD_RSHIFT are the payload extraction shifts.
 307     // They are reversed here for payload insertion.
 308
 309     // assert(_objc_taggedPointersEnabled());
 310     if (tag <= OBJC_TAG_Last60BitPayload) {
 311         // assert(((value << _OBJC_TAG_PAYLOAD_RSHIFT) >> _OBJC_TAG_PAYLOAD_LSHIFT) == value);
 312         return (void*)
 313             (_OBJC_TAG_MASK |
 314              ((uintptr_t)tag << _OBJC_TAG_INDEX_SHIFT) |
 315              ((value << _OBJC_TAG_PAYLOAD_RSHIFT) >> _OBJC_TAG_PAYLOAD_LSHIFT));
 316     } else {
 317         // assert(tag >= OBJC_TAG_First52BitPayload);
 318         // assert(tag <= OBJC_TAG_Last52BitPayload);
 319         // assert(((value << _OBJC_TAG_EXT_PAYLOAD_RSHIFT) >> _OBJC_TAG_EXT_PAYLOAD_LSHIFT) == value);
 320         return (void*)
 321             (_OBJC_TAG_EXT_MASK |
 322              ((uintptr_t)(tag - OBJC_TAG_First52BitPayload) << _OBJC_TAG_EXT_INDEX_SHIFT) |
 323              ((value << _OBJC_TAG_EXT_PAYLOAD_RSHIFT) >> _OBJC_TAG_EXT_PAYLOAD_LSHIFT));
 324     }
 325 }
 326
 327 static inline bool
 328 _objc_isTaggedPointer(const void *ptr)
 329 {
 330     return ((intptr_t)ptr & _OBJC_TAG_MASK) == _OBJC_TAG_MASK;
 331 }
 332
 333 static inline objc_tag_index_t
 334 _objc_getTaggedPointerTag(const void *ptr)
 335 {
 336     // assert(_objc_isTaggedPointer(ptr));
 337     uintptr_t basicTag = ((uintptr_t)ptr >> _OBJC_TAG_INDEX_SHIFT) & _OBJC_TAG_INDEX_MASK;
 338     uintptr_t extTag =   ((uintptr_t)ptr >> _OBJC_TAG_EXT_INDEX_SHIFT) & _OBJC_TAG_EXT_INDEX_MASK;
 339     if (basicTag == _OBJC_TAG_INDEX_MASK) {
 340         return (objc_tag_index_t)(extTag + OBJC_TAG_First52BitPayload);
 341     } else {
 342         return (objc_tag_index_t)basicTag;
 343     }
 344 }
 345
 346 static inline uintptr_t
 347 _objc_getTaggedPointerValue(const void *ptr)
 348 {
 349     // assert(_objc_isTaggedPointer(ptr));
 350     uintptr_t basicTag = ((uintptr_t)ptr >> _OBJC_TAG_INDEX_SHIFT) & _OBJC_TAG_INDEX_MASK;
 351     if (basicTag == _OBJC_TAG_INDEX_MASK) {
 352         return ((uintptr_t)ptr << _OBJC_TAG_EXT_PAYLOAD_LSHIFT) >> _OBJC_TAG_EXT_PAYLOAD_RSHIFT;
 353     } else {
 354         return ((uintptr_t)ptr << _OBJC_TAG_PAYLOAD_LSHIFT) >> _OBJC_TAG_PAYLOAD_RSHIFT;
 355     }
 356 }
 357
 358 static inline intptr_t
 359 _objc_getTaggedPointerSignedValue(const void *ptr)
 360 {
 361     // assert(_objc_isTaggedPointer(ptr));
 362     uintptr_t basicTag = ((uintptr_t)ptr >> _OBJC_TAG_INDEX_SHIFT) & _OBJC_TAG_INDEX_MASK;
 363     if (basicTag == _OBJC_TAG_INDEX_MASK) {
 364         return ((intptr_t)ptr << _OBJC_TAG_EXT_PAYLOAD_LSHIFT) >> _OBJC_TAG_EXT_PAYLOAD_RSHIFT;
 365     } else {
 366         return ((intptr_t)ptr << _OBJC_TAG_PAYLOAD_LSHIFT) >> _OBJC_TAG_PAYLOAD_RSHIFT;
 367     }
 368 }
 369
 370 // OBJC_HAVE_TAGGED_POINTERS
 371 #endif
 372
 373
 374 /**
 375  * Returns the method implementation of an object.
 376  *
 377  * @param obj An Objective-C object.
 378  * @param name An Objective-C selector.
 379  *
 380  * @return The IMP corresponding to the instance method implemented by
 381  * the class of \e obj.
 382  *
 383  * @note Equivalent to:
 384  *
 385  * class_getMethodImplementation(object_getClass(obj), name);
 386  */
 387 OBJC_EXPORT IMP object_getMethodImplementation(id obj, SEL name)
 388     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0);
 389
 390 OBJC_EXPORT IMP object_getMethodImplementation_stret(id obj, SEL name)
 391     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0)
 392     OBJC_ARM64_UNAVAILABLE;
 393
 394
 395 // Instance-specific instance variable layout.
 396
 397 OBJC_EXPORT void _class_setIvarLayoutAccessor(Class cls_gen, const uint8_t* (*accessor) (id object))
 398     __OSX_AVAILABLE(10.7)
 399     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE __WATCHOS_UNAVAILABLE;
 400 OBJC_EXPORT const uint8_t *_object_getIvarLayout(Class cls_gen, id object)
 401     __OSX_AVAILABLE(10.7)
 402     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE __WATCHOS_UNAVAILABLE;
 403
 404 /*
 405   "Unknown" includes non-object ivars and non-ARC non-__weak ivars
 406   "Strong" includes ARC __strong ivars
 407   "Weak" includes ARC and new MRC __weak ivars
 408   "Unretained" includes ARC __unsafe_unretained and old GC+MRC __weak ivars
 409 */
 410 typedef enum {
 411     objc_ivar_memoryUnknown,     // unknown / unknown
 412     objc_ivar_memoryStrong,      // direct access / objc_storeStrong
 413     objc_ivar_memoryWeak,        // objc_loadWeak[Retained] / objc_storeWeak
 414     objc_ivar_memoryUnretained   // direct access / direct access
 415 } objc_ivar_memory_management_t;
 416
 417 OBJC_EXPORT objc_ivar_memory_management_t _class_getIvarMemoryManagement(Class cls, Ivar ivar)
 418     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0);
 419
 420 OBJC_EXPORT BOOL _class_isFutureClass(Class cls)
 421     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0);
 422
 423
 424 // API to only be called by root classes like NSObject or NSProxy
 425
 426 OBJC_EXPORT
 427 id
 428 _objc_rootRetain(id obj)
 429     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 430
 431 OBJC_EXPORT
 432 void
 433 _objc_rootRelease(id obj)
 434     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 435
 436 OBJC_EXPORT
 437 bool
 438 _objc_rootReleaseWasZero(id obj)
 439     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 440
 441 OBJC_EXPORT
 442 bool
 443 _objc_rootTryRetain(id obj)
 444     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 445
 446 OBJC_EXPORT
 447 bool
 448 _objc_rootIsDeallocating(id obj)
 449     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 450
 451 OBJC_EXPORT
 452 id
 453 _objc_rootAutorelease(id obj)
 454     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 455
 456 OBJC_EXPORT
 457 uintptr_t
 458 _objc_rootRetainCount(id obj)
 459     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 460
 461 OBJC_EXPORT
 462 id
 463 _objc_rootInit(id obj)
 464     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 465
 466 OBJC_EXPORT
 467 id
 468 _objc_rootAllocWithZone(Class cls, malloc_zone_t *zone)
 469     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 470
 471 OBJC_EXPORT
 472 id
 473 _objc_rootAlloc(Class cls)
 474     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 475
 476 OBJC_EXPORT
 477 void
 478 _objc_rootDealloc(id obj)
 479     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 480
 481 OBJC_EXPORT
 482 void
 483 _objc_rootFinalize(id obj)
 484     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 485
 486 OBJC_EXPORT
 487 malloc_zone_t *
 488 _objc_rootZone(id obj)
 489     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 490
 491 OBJC_EXPORT
 492 uintptr_t
 493 _objc_rootHash(id obj)
 494     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 495
 496 OBJC_EXPORT
 497 void *
 498 objc_autoreleasePoolPush(void)
 499     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 500
 501 OBJC_EXPORT
 502 void
 503 objc_autoreleasePoolPop(void *context)
 504     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 505
 506
 507 OBJC_EXPORT id objc_alloc(Class cls)
 508     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0);
 509
 510 OBJC_EXPORT id objc_allocWithZone(Class cls)
 511     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0);
 512
 513 OBJC_EXPORT id objc_retain(id obj)
 514     __asm__("_objc_retain")
 515     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 516
 517 OBJC_EXPORT void objc_release(id obj)
 518     __asm__("_objc_release")
 519     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 520
 521 OBJC_EXPORT id objc_autorelease(id obj)
 522     __asm__("_objc_autorelease")
 523     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 524
 525 // Prepare a value at +1 for return through a +0 autoreleasing convention.
 526 OBJC_EXPORT
 527 id
 528 objc_autoreleaseReturnValue(id obj)
 529     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 530
 531 // Prepare a value at +0 for return through a +0 autoreleasing convention.
 532 OBJC_EXPORT
 533 id
 534 objc_retainAutoreleaseReturnValue(id obj)
 535     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 536
 537 // Accept a value returned through a +0 autoreleasing convention for use at +1.
 538 OBJC_EXPORT
 539 id
 540 objc_retainAutoreleasedReturnValue(id obj)
 541     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 542
 543 // Accept a value returned through a +0 autoreleasing convention for use at +0.
 544 OBJC_EXPORT
 545 id
 546 objc_unsafeClaimAutoreleasedReturnValue(id obj)
 547     OBJC_AVAILABLE(10.11, 9.0, 9.0, 1.0);
 548
 549 OBJC_EXPORT
 550 void
 551 objc_storeStrong(id *location, id obj)
 552     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 553
 554 OBJC_EXPORT
 555 id
 556 objc_retainAutorelease(id obj)
 557     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 558
 559 // obsolete.
 560 OBJC_EXPORT id objc_retain_autorelease(id obj)
 561     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 562
 563 OBJC_EXPORT
 564 id
 565 objc_loadWeakRetained(id *location)
 566     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 567
 568 OBJC_EXPORT
 569 id
 570 objc_initWeak(id *location, id val)
 571     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 572
 573 // Like objc_storeWeak, but stores nil if the new object is deallocating
 574 // or the new object's class does not support weak references.
 575 // Returns the value stored (either the new object or nil).
 576 OBJC_EXPORT
 577 id
 578 objc_storeWeakOrNil(id *location, id obj)
 579     OBJC_AVAILABLE(10.11, 9.0, 9.0, 1.0);
 580
 581 // Like objc_initWeak, but stores nil if the new object is deallocating
 582 // or the new object's class does not support weak references.
 583 // Returns the value stored (either the new object or nil).
 584 OBJC_EXPORT
 585 id
 586 objc_initWeakOrNil(id *location, id val)
 587     OBJC_AVAILABLE(10.11, 9.0, 9.0, 1.0);
 588
 589 OBJC_EXPORT
 590 void
 591 objc_destroyWeak(id *location)
 592     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 593
 594 OBJC_EXPORT
 595 void
 596 objc_copyWeak(id *to, id *from)
 597     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 598
 599 OBJC_EXPORT
 600 void
 601 objc_moveWeak(id *to, id *from)
 602     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 603
 604
 605 OBJC_EXPORT
 606 void
 607 _objc_autoreleasePoolPrint(void)
 608     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 609
 610 OBJC_EXPORT BOOL objc_should_deallocate(id object)
 611     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 612
 613 OBJC_EXPORT void objc_clear_deallocating(id object)
 614     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 615
 616
 617 // to make CF link for now
 618
 619 OBJC_EXPORT
 620 void *
 621 _objc_autoreleasePoolPush(void)
 622     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 623
 624 OBJC_EXPORT
 625 void
 626 _objc_autoreleasePoolPop(void *context)
 627     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 628
 629
 630 // Extra @encode data for XPC, or NULL
 631 OBJC_EXPORT const char *_protocol_getMethodTypeEncoding(Protocol *p, SEL sel, BOOL isRequiredMethod, BOOL isInstanceMethod)
 632     OBJC_AVAILABLE(10.8, 6.0, 9.0, 1.0);
 633
 634
 635 // API to only be called by classes that provide their own reference count storage
 636
 637 OBJC_EXPORT
 638 void
 639 _objc_deallocOnMainThreadHelper(void *context)
 640     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0);
 641
 642 // On async versus sync deallocation and the _dealloc2main flag
 643 //
 644 // Theory:
 645 //
 646 // If order matters, then code must always: [self dealloc].
 647 // If order doesn't matter, then always async should be safe.
 648 //
 649 // Practice:
 650 //
 651 // The _dealloc2main bit is set for GUI objects that may be retained by other
 652 // threads. Once deallocation begins on the main thread, doing more async
 653 // deallocation will at best cause extra UI latency and at worst cause
 654 // use-after-free bugs in unretained delegate style patterns. Yes, this is
 655 // extremely fragile. Yes, in the long run, developers should switch to weak
 656 // references.
 657 //
 658 // Note is NOT safe to do any equality check against the result of
 659 // dispatch_get_current_queue(). The main thread can and does drain more than
 660 // one dispatch queue. That is why we call pthread_main_np().
 661 //
 662
 663 typedef enum {
 664     _OBJC_RESURRECT_OBJECT = -1,        /* _logicBlock has called -retain, and scheduled a -release for later. */
 665     _OBJC_DEALLOC_OBJECT_NOW = 1,       /* call [self dealloc] immediately. */
 666     _OBJC_DEALLOC_OBJECT_LATER = 2      /* call [self dealloc] on the main queue. */
 667 } _objc_object_disposition_t;
 668
 669 #define _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC_BLOCK(_rc_ivar, _logicBlock)        \
 670     -(id)retain {                                                               \
 671         /* this will fail to compile if _rc_ivar is an unsigned type */         \
 672         int _retain_count_ivar_must_not_be_unsigned[0L - (__typeof__(_rc_ivar))-1] __attribute__((unused)); \
 673         __typeof__(_rc_ivar) _prev = __sync_fetch_and_add(&_rc_ivar, 2);        \
 674         if (_prev < -2) { /* specifically allow resurrection from logical 0. */ \
 675             __builtin_trap(); /* BUG: retain of over-released ref */            \
 676         }                                                                       \
 677         return self;                                                            \
 678     }                                                                           \
 679     -(oneway void)release {                                                     \
 680         __typeof__(_rc_ivar) _prev = __sync_fetch_and_sub(&_rc_ivar, 2);        \
 681         if (_prev > 0) {                                                        \
 682             return;                                                             \
 683         } else if (_prev < 0) {                                                 \
 684             __builtin_trap(); /* BUG: over-release */                           \
 685         }                                                                       \
 686         _objc_object_disposition_t fate = _logicBlock(self);                    \
 687         if (fate == _OBJC_RESURRECT_OBJECT) {                                   \
 688             return;                                                             \
 689         }                                                                       \
 690         /* mark the object as deallocating. */                                  \
 691         if (!__sync_bool_compare_and_swap(&_rc_ivar, -2, 1)) {                  \
 692             __builtin_trap(); /* BUG: dangling ref did a retain */              \
 693         }                                                                       \
 694         if (fate == _OBJC_DEALLOC_OBJECT_NOW) {                                 \
 695             [self dealloc];                                                     \
 696         } else if (fate == _OBJC_DEALLOC_OBJECT_LATER) {                        \
 697             dispatch_barrier_async_f(dispatch_get_main_queue(), self,           \
 698                 _objc_deallocOnMainThreadHelper);                               \
 699         } else {                                                                \
 700             __builtin_trap(); /* BUG: bogus fate value */                       \
 701         }                                                                       \
 702     }                                                                           \
 703     -(NSUInteger)retainCount {                                                  \
 704         return (_rc_ivar + 2) >> 1;                                             \
 705     }                                                                           \
 706     -(BOOL)_tryRetain {                                                         \
 707         __typeof__(_rc_ivar) _prev;                                             \
 708         do {                                                                    \
 709             _prev = _rc_ivar;                                                   \
 710             if (_prev & 1) {                                                    \
 711                 return 0;                                                       \
 712             } else if (_prev == -2) {                                           \
 713                 return 0;                                                       \
 714             } else if (_prev < -2) {                                            \
 715                 __builtin_trap(); /* BUG: over-release elsewhere */             \
 716             }                                                                   \
 717         } while ( ! __sync_bool_compare_and_swap(&_rc_ivar, _prev, _prev + 2)); \
 718         return 1;                                                               \
 719     }                                                                           \
 720     -(BOOL)_isDeallocating {                                                    \
 721         if (_rc_ivar == -2) {                                                   \
 722             return 1;                                                           \
 723         } else if (_rc_ivar < -2) {                                             \
 724             __builtin_trap(); /* BUG: over-release elsewhere */                 \
 725         }                                                                       \
 726         return _rc_ivar & 1;                                                    \
 727     }
 728
 729 #define _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC(_rc_ivar, _dealloc2main)            \
 730     _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC_BLOCK(_rc_ivar, (^(id _self_ __attribute__((unused))) { \
 731         if (_dealloc2main && !pthread_main_np()) {                              \
 732             return _OBJC_DEALLOC_OBJECT_LATER;                                  \
 733         } else {                                                                \
 734             return _OBJC_DEALLOC_OBJECT_NOW;                                    \
 735         }                                                                       \
 736     }))
 737
 738 #define _OBJC_SUPPORTED_INLINE_REFCNT(_rc_ivar) _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC(_rc_ivar, 0)
 739 #define _OBJC_SUPPORTED_INLINE_REFCNT_WITH_DEALLOC2MAIN(_rc_ivar) _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC(_rc_ivar, 1)
 740
 741 __END_DECLS
 742
 743 #endif