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