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 <mach-o/loader.h>
  45 #include <dispatch/dispatch.h>
  46
  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
  58 __BEGIN_DECLS
  59
  60 // In-place construction of an Objective-C class.
  61 // cls and metacls must each be OBJC_MAX_CLASS_SIZE bytes.
  62 // Returns nil if a class with the same name already exists.
  63 // Returns nil if the superclass is under construction.
  64 // Call objc_registerClassPair() when you are done.
  65 OBJC_EXPORT Class _Nullable
  66 objc_initializeClassPair(Class _Nullable superclass, const char * _Nonnull name,
  67                          Class _Nonnull cls, Class _Nonnull metacls)
  68     OBJC_AVAILABLE(10.6, 3.0, 9.0, 1.0, 2.0);
  69
  70 // Class and metaclass construction from a compiler-generated memory image.
  71 // cls and cls->isa must each be OBJC_MAX_CLASS_SIZE bytes.
  72 // Extra bytes not used the the metadata must be zero.
  73 // info is the same objc_image_info that would be emitted by a static compiler.
  74 // Returns nil if a class with the same name already exists.
  75 // Returns nil if the superclass is nil and the class is not marked as a root.
  76 // Returns nil if the superclass is under construction.
  77 // Do not call objc_registerClassPair().
  78 #if __OBJC2__
  79 struct objc_image_info;
  80 OBJC_EXPORT Class _Nullable
  81 objc_readClassPair(Class _Nonnull cls,
  82                    const struct objc_image_info * _Nonnull info)
  83     OBJC_AVAILABLE(10.10, 8.0, 9.0, 1.0, 2.0);
  84 #endif
  85
  86 // Batch object allocation using malloc_zone_batch_malloc().
  87 OBJC_EXPORT unsigned
  88 class_createInstances(Class _Nullable cls, size_t extraBytes,
  89                       id _Nonnull * _Nonnull results, unsigned num_requested)
  90     OBJC_AVAILABLE(10.7, 4.3, 9.0, 1.0, 2.0)
  91     OBJC_ARC_UNAVAILABLE;
  92
  93 // Get the isa pointer written into objects just before being freed.
  94 OBJC_EXPORT Class _Nonnull
  95 _objc_getFreedObjectClass(void)
  96     OBJC_AVAILABLE(10.0, 2.0, 9.0, 1.0, 2.0);
  97
  98 // env NSObjCMessageLoggingEnabled
  99 OBJC_EXPORT void
 100 instrumentObjcMessageSends(BOOL flag)
 101     OBJC_AVAILABLE(10.0, 2.0, 9.0, 1.0, 2.0);
 102
 103 // Initializer called by libSystem
 104 OBJC_EXPORT void
 105 _objc_init(void)
 106 #if __OBJC2__
 107     OBJC_AVAILABLE(10.8, 6.0, 9.0, 1.0, 2.0);
 108 #else
 109     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0, 2.0);
 110 #endif
 111
 112 // fork() safety called by libSystem
 113 OBJC_EXPORT void
 114 _objc_atfork_prepare(void)
 115     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0, 2.0);
 116
 117 OBJC_EXPORT void
 118 _objc_atfork_parent(void)
 119     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0, 2.0);
 120
 121 OBJC_EXPORT void
 122 _objc_atfork_child(void)
 123     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0, 2.0);
 124
 125 // Return YES if GC is on and `object` is a GC allocation.
 126 OBJC_EXPORT BOOL
 127 objc_isAuto(id _Nullable object)
 128     __OSX_DEPRECATED(10.4, 10.8, "it always returns NO")
 129     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE
 130     __WATCHOS_UNAVAILABLE __BRIDGEOS_UNAVAILABLE;
 131
 132 // GC debugging
 133 OBJC_EXPORT BOOL
 134 objc_dumpHeap(char * _Nonnull filename, unsigned long length)
 135     __OSX_DEPRECATED(10.4, 10.8, "it always returns NO")
 136     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE
 137     __WATCHOS_UNAVAILABLE __BRIDGEOS_UNAVAILABLE;
 138
 139 // GC startup callback from Foundation
 140 OBJC_EXPORT malloc_zone_t * _Nullable
 141 objc_collect_init(int (* _Nonnull callback)(void))
 142     __OSX_DEPRECATED(10.4, 10.8, "it does nothing")
 143     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE
 144     __WATCHOS_UNAVAILABLE __BRIDGEOS_UNAVAILABLE;
 145
 146 // Plainly-implemented GC barriers. Rosetta used to use these.
 147 OBJC_EXPORT id _Nullable
 148 objc_assign_strongCast_generic(id _Nullable value, id _Nullable * _Nonnull dest)
 149     UNAVAILABLE_ATTRIBUTE;
 150
 151 OBJC_EXPORT id _Nullable
 152 objc_assign_global_generic(id _Nullable value, id _Nullable * _Nonnull dest)
 153     UNAVAILABLE_ATTRIBUTE;
 154
 155 OBJC_EXPORT id _Nullable
 156 objc_assign_threadlocal_generic(id _Nullable value,
 157                                 id _Nullable * _Nonnull dest)
 158     UNAVAILABLE_ATTRIBUTE;
 159
 160 OBJC_EXPORT id _Nullable
 161 objc_assign_ivar_generic(id _Nullable value, id _Nonnull dest, ptrdiff_t offset)
 162     UNAVAILABLE_ATTRIBUTE;
 163
 164 // GC preflight for an app executable.
 165 // 1: some slice requires GC
 166 // 0: no slice requires GC
 167 // -1: I/O or file format error
 168 OBJC_EXPORT int
 169 objc_appRequiresGC(int fd)
 170     __OSX_AVAILABLE(10.11)
 171     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE
 172     __WATCHOS_UNAVAILABLE __BRIDGEOS_UNAVAILABLE;
 173
 174 // Install missing-class callback. Used by the late unlamented ZeroLink.
 175 OBJC_EXPORT void
 176 _objc_setClassLoader(BOOL (* _Nonnull newClassLoader)(const char * _Nonnull))
 177     OBJC2_UNAVAILABLE;
 178
 179 #if !(TARGET_OS_OSX && !TARGET_OS_IOSMAC && __i386__)
 180 OBJC_EXPORT void
 181 _objc_setClassCopyFixupHandler(void (* _Nonnull newFixupHandler)
 182     (Class _Nonnull oldClass, Class _Nonnull newClass));
 183 // fixme work around bug in Swift
 184 //    OBJC_AVAILABLE(10.14, 12.0, 12.0, 5.0, 3.0)
 185 #endif
 186
 187 // Install handler for allocation failures.
 188 // Handler may abort, or throw, or provide an object to return.
 189 OBJC_EXPORT void
 190 _objc_setBadAllocHandler(id _Nullable (* _Nonnull newHandler)
 191                            (Class _Nullable isa))
 192     OBJC_AVAILABLE(10.8, 6.0, 9.0, 1.0, 2.0);
 193
 194 // Used by ExceptionHandling.framework
 195 #if !__OBJC2__
 196 OBJC_EXPORT void
 197 _objc_error(id _Nullable rcv, const char * _Nonnull fmt, va_list args)
 198     __attribute__((noreturn))
 199     __OSX_DEPRECATED(10.0, 10.5, "use other logging facilities instead")
 200     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE
 201     __WATCHOS_UNAVAILABLE __BRIDGEOS_UNAVAILABLE;
 202
 203 #endif
 204
 205
 206 /**
 207  * Returns the names of all the classes within a library.
 208  *
 209  * @param image The mach header for library or framework you are inquiring about.
 210  * @param outCount The number of class names returned.
 211  *
 212  * @return An array of C strings representing the class names.
 213  */
 214 OBJC_EXPORT const char * _Nonnull * _Nullable
 215 objc_copyClassNamesForImageHeader(const struct mach_header * _Nonnull mh,
 216                                   unsigned int * _Nullable outCount)
 217     OBJC_AVAILABLE(10.14, 12.0, 12.0, 5.0, 3.0);
 218
 219 // Tagged pointer objects.
 220
 221 #if __LP64__
 222 #define OBJC_HAVE_TAGGED_POINTERS 1
 223 #endif
 224
 225 #if OBJC_HAVE_TAGGED_POINTERS
 226
 227 // Tagged pointer layout and usage is subject to change on different OS versions.
 228
 229 // Tag indexes 0..<7 have a 60-bit payload.
 230 // Tag index 7 is reserved.
 231 // Tag indexes 8..<264 have a 52-bit payload.
 232 // Tag index 264 is reserved.
 233
 234 #if __has_feature(objc_fixed_enum)  ||  __cplusplus >= 201103L
 235 enum objc_tag_index_t : uint16_t
 236 #else
 237 typedef uint16_t objc_tag_index_t;
 238 enum
 239 #endif
 240 {
 241     // 60-bit payloads
 242     OBJC_TAG_NSAtom            = 0,
 243     OBJC_TAG_1                 = 1,
 244     OBJC_TAG_NSString          = 2,
 245     OBJC_TAG_NSNumber          = 3,
 246     OBJC_TAG_NSIndexPath       = 4,
 247     OBJC_TAG_NSManagedObjectID = 5,
 248     OBJC_TAG_NSDate            = 6,
 249
 250     // 60-bit reserved
 251     OBJC_TAG_RESERVED_7        = 7,
 252
 253     // 52-bit payloads
 254     OBJC_TAG_Photos_1          = 8,
 255     OBJC_TAG_Photos_2          = 9,
 256     OBJC_TAG_Photos_3          = 10,
 257     OBJC_TAG_Photos_4          = 11,
 258     OBJC_TAG_XPC_1             = 12,
 259     OBJC_TAG_XPC_2             = 13,
 260     OBJC_TAG_XPC_3             = 14,
 261     OBJC_TAG_XPC_4             = 15,
 262
 263     OBJC_TAG_First60BitPayload = 0,
 264     OBJC_TAG_Last60BitPayload  = 6,
 265     OBJC_TAG_First52BitPayload = 8,
 266     OBJC_TAG_Last52BitPayload  = 263,
 267
 268     OBJC_TAG_RESERVED_264      = 264
 269 };
 270 #if __has_feature(objc_fixed_enum)  &&  !defined(__cplusplus)
 271 typedef enum objc_tag_index_t objc_tag_index_t;
 272 #endif
 273
 274
 275 // Returns true if tagged pointers are enabled.
 276 // The other functions below must not be called if tagged pointers are disabled.
 277 static inline bool
 278 _objc_taggedPointersEnabled(void);
 279
 280 // Register a class for a tagged pointer tag.
 281 // Aborts if the tag is invalid or already in use.
 282 OBJC_EXPORT void
 283 _objc_registerTaggedPointerClass(objc_tag_index_t tag, Class _Nonnull cls)
 284     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0);
 285
 286 // Returns the registered class for the given tag.
 287 // Returns nil if the tag is valid but has no registered class.
 288 // Aborts if the tag is invalid.
 289 OBJC_EXPORT Class _Nullable
 290 _objc_getClassForTag(objc_tag_index_t tag)
 291     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0);
 292
 293 // Create a tagged pointer object with the given tag and payload.
 294 // Assumes the tag is valid.
 295 // Assumes tagged pointers are enabled.
 296 // The payload will be silently truncated to fit.
 297 static inline void * _Nonnull
 298 _objc_makeTaggedPointer(objc_tag_index_t tag, uintptr_t payload);
 299
 300 // Return true if ptr is a tagged pointer object.
 301 // Does not check the validity of ptr's class.
 302 static inline bool
 303 _objc_isTaggedPointer(const void * _Nullable ptr);
 304
 305 // Extract the tag value from the given tagged pointer object.
 306 // Assumes ptr is a valid tagged pointer object.
 307 // Does not check the validity of ptr's tag.
 308 static inline objc_tag_index_t
 309 _objc_getTaggedPointerTag(const void * _Nullable ptr);
 310
 311 // Extract the payload from the given tagged pointer object.
 312 // Assumes ptr is a valid tagged pointer object.
 313 // The payload value is zero-extended.
 314 static inline uintptr_t
 315 _objc_getTaggedPointerValue(const void * _Nullable ptr);
 316
 317 // Extract the payload from the given tagged pointer object.
 318 // Assumes ptr is a valid tagged pointer object.
 319 // The payload value is sign-extended.
 320 static inline intptr_t
 321 _objc_getTaggedPointerSignedValue(const void * _Nullable ptr);
 322
 323 // Don't use the values below. Use the declarations above.
 324
 325 #if (TARGET_OS_OSX || TARGET_OS_IOSMAC) && __x86_64__
 326     // 64-bit Mac - tag bit is LSB
 327 #   define OBJC_MSB_TAGGED_POINTERS 0
 328 #else
 329     // Everything else - tag bit is MSB
 330 #   define OBJC_MSB_TAGGED_POINTERS 1
 331 #endif
 332
 333 #define _OBJC_TAG_INDEX_MASK 0x7
 334 // array slot includes the tag bit itself
 335 #define _OBJC_TAG_SLOT_COUNT 16
 336 #define _OBJC_TAG_SLOT_MASK 0xf
 337
 338 #define _OBJC_TAG_EXT_INDEX_MASK 0xff
 339 // array slot has no extra bits
 340 #define _OBJC_TAG_EXT_SLOT_COUNT 256
 341 #define _OBJC_TAG_EXT_SLOT_MASK 0xff
 342
 343 #if OBJC_MSB_TAGGED_POINTERS
 344 #   define _OBJC_TAG_MASK (1UL<<63)
 345 #   define _OBJC_TAG_INDEX_SHIFT 60
 346 #   define _OBJC_TAG_SLOT_SHIFT 60
 347 #   define _OBJC_TAG_PAYLOAD_LSHIFT 4
 348 #   define _OBJC_TAG_PAYLOAD_RSHIFT 4
 349 #   define _OBJC_TAG_EXT_MASK (0xfUL<<60)
 350 #   define _OBJC_TAG_EXT_INDEX_SHIFT 52
 351 #   define _OBJC_TAG_EXT_SLOT_SHIFT 52
 352 #   define _OBJC_TAG_EXT_PAYLOAD_LSHIFT 12
 353 #   define _OBJC_TAG_EXT_PAYLOAD_RSHIFT 12
 354 #else
 355 #   define _OBJC_TAG_MASK 1UL
 356 #   define _OBJC_TAG_INDEX_SHIFT 1
 357 #   define _OBJC_TAG_SLOT_SHIFT 0
 358 #   define _OBJC_TAG_PAYLOAD_LSHIFT 0
 359 #   define _OBJC_TAG_PAYLOAD_RSHIFT 4
 360 #   define _OBJC_TAG_EXT_MASK 0xfUL
 361 #   define _OBJC_TAG_EXT_INDEX_SHIFT 4
 362 #   define _OBJC_TAG_EXT_SLOT_SHIFT 4
 363 #   define _OBJC_TAG_EXT_PAYLOAD_LSHIFT 0
 364 #   define _OBJC_TAG_EXT_PAYLOAD_RSHIFT 12
 365 #endif
 366
 367 extern uintptr_t objc_debug_taggedpointer_obfuscator;
 368
 369 static inline void * _Nonnull
 370 _objc_encodeTaggedPointer(uintptr_t ptr)
 371 {
 372     return (void *)(objc_debug_taggedpointer_obfuscator ^ ptr);
 373 }
 374
 375 static inline uintptr_t
 376 _objc_decodeTaggedPointer(const void * _Nullable ptr)
 377 {
 378     return (uintptr_t)ptr ^ objc_debug_taggedpointer_obfuscator;
 379 }
 380
 381 static inline bool
 382 _objc_taggedPointersEnabled(void)
 383 {
 384     extern uintptr_t objc_debug_taggedpointer_mask;
 385     return (objc_debug_taggedpointer_mask != 0);
 386 }
 387
 388 static inline void * _Nonnull
 389 _objc_makeTaggedPointer(objc_tag_index_t tag, uintptr_t value)
 390 {
 391     // PAYLOAD_LSHIFT and PAYLOAD_RSHIFT are the payload extraction shifts.
 392     // They are reversed here for payload insertion.
 393
 394     // assert(_objc_taggedPointersEnabled());
 395     if (tag <= OBJC_TAG_Last60BitPayload) {
 396         // assert(((value << _OBJC_TAG_PAYLOAD_RSHIFT) >> _OBJC_TAG_PAYLOAD_LSHIFT) == value);
 397         uintptr_t result =
 398             (_OBJC_TAG_MASK |
 399              ((uintptr_t)tag << _OBJC_TAG_INDEX_SHIFT) |
 400              ((value << _OBJC_TAG_PAYLOAD_RSHIFT) >> _OBJC_TAG_PAYLOAD_LSHIFT));
 401         return _objc_encodeTaggedPointer(result);
 402     } else {
 403         // assert(tag >= OBJC_TAG_First52BitPayload);
 404         // assert(tag <= OBJC_TAG_Last52BitPayload);
 405         // assert(((value << _OBJC_TAG_EXT_PAYLOAD_RSHIFT) >> _OBJC_TAG_EXT_PAYLOAD_LSHIFT) == value);
 406         uintptr_t result =
 407             (_OBJC_TAG_EXT_MASK |
 408              ((uintptr_t)(tag - OBJC_TAG_First52BitPayload) << _OBJC_TAG_EXT_INDEX_SHIFT) |
 409              ((value << _OBJC_TAG_EXT_PAYLOAD_RSHIFT) >> _OBJC_TAG_EXT_PAYLOAD_LSHIFT));
 410         return _objc_encodeTaggedPointer(result);
 411     }
 412 }
 413
 414 static inline bool
 415 _objc_isTaggedPointer(const void * _Nullable ptr)
 416 {
 417     return ((uintptr_t)ptr & _OBJC_TAG_MASK) == _OBJC_TAG_MASK;
 418 }
 419
 420 static inline objc_tag_index_t
 421 _objc_getTaggedPointerTag(const void * _Nullable ptr)
 422 {
 423     // assert(_objc_isTaggedPointer(ptr));
 424     uintptr_t value = _objc_decodeTaggedPointer(ptr);
 425     uintptr_t basicTag = (value >> _OBJC_TAG_INDEX_SHIFT) & _OBJC_TAG_INDEX_MASK;
 426     uintptr_t extTag =   (value >> _OBJC_TAG_EXT_INDEX_SHIFT) & _OBJC_TAG_EXT_INDEX_MASK;
 427     if (basicTag == _OBJC_TAG_INDEX_MASK) {
 428         return (objc_tag_index_t)(extTag + OBJC_TAG_First52BitPayload);
 429     } else {
 430         return (objc_tag_index_t)basicTag;
 431     }
 432 }
 433
 434 static inline uintptr_t
 435 _objc_getTaggedPointerValue(const void * _Nullable ptr)
 436 {
 437     // assert(_objc_isTaggedPointer(ptr));
 438     uintptr_t value = _objc_decodeTaggedPointer(ptr);
 439     uintptr_t basicTag = (value >> _OBJC_TAG_INDEX_SHIFT) & _OBJC_TAG_INDEX_MASK;
 440     if (basicTag == _OBJC_TAG_INDEX_MASK) {
 441         return (value << _OBJC_TAG_EXT_PAYLOAD_LSHIFT) >> _OBJC_TAG_EXT_PAYLOAD_RSHIFT;
 442     } else {
 443         return (value << _OBJC_TAG_PAYLOAD_LSHIFT) >> _OBJC_TAG_PAYLOAD_RSHIFT;
 444     }
 445 }
 446
 447 static inline intptr_t
 448 _objc_getTaggedPointerSignedValue(const void * _Nullable ptr)
 449 {
 450     // assert(_objc_isTaggedPointer(ptr));
 451     uintptr_t value = _objc_decodeTaggedPointer(ptr);
 452     uintptr_t basicTag = (value >> _OBJC_TAG_INDEX_SHIFT) & _OBJC_TAG_INDEX_MASK;
 453     if (basicTag == _OBJC_TAG_INDEX_MASK) {
 454         return ((intptr_t)value << _OBJC_TAG_EXT_PAYLOAD_LSHIFT) >> _OBJC_TAG_EXT_PAYLOAD_RSHIFT;
 455     } else {
 456         return ((intptr_t)value << _OBJC_TAG_PAYLOAD_LSHIFT) >> _OBJC_TAG_PAYLOAD_RSHIFT;
 457     }
 458 }
 459
 460 // OBJC_HAVE_TAGGED_POINTERS
 461 #endif
 462
 463
 464 /**
 465  * Returns the method implementation of an object.
 466  *
 467  * @param obj An Objective-C object.
 468  * @param name An Objective-C selector.
 469  *
 470  * @return The IMP corresponding to the instance method implemented by
 471  * the class of \e obj.
 472  *
 473  * @note Equivalent to:
 474  *
 475  * class_getMethodImplementation(object_getClass(obj), name);
 476  */
 477 OBJC_EXPORT IMP _Nonnull
 478 object_getMethodImplementation(id _Nullable obj, SEL _Nonnull name)
 479     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0);
 480
 481 OBJC_EXPORT IMP _Nonnull
 482 object_getMethodImplementation_stret(id _Nullable obj, SEL _Nonnull name)
 483     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0)
 484     OBJC_ARM64_UNAVAILABLE;
 485
 486
 487 /**
 488  * Adds multiple methods to a class in bulk. This amortizes overhead that can be
 489  * expensive when adding methods one by one with class_addMethod.
 490  *
 491  * @param cls The class to which to add the methods.
 492  * @param names An array of selectors for the methods to add.
 493  * @param imps An array of functions which implement the new methods.
 494  * @param types An array of strings that describe the types of each method's
 495  *              arguments.
 496  * @param count The number of items in the names, imps, and types arrays.
 497  * @param outFiledCount Upon return, contains the number of failed selectors in
 498  *                      the returned array.
 499  *
 500  * @return A NULL-terminated C array of selectors which could not be added. A
 501  * method cannot be added when a method of that name already exists on that
 502  * class. When no failures occur, the return value is \c NULL. When a non-NULL
 503  * value is returned, the caller must free the array with \c free().
 504  *
 505  */
 506 #if __OBJC2__
 507 OBJC_EXPORT _Nullable SEL * _Nullable
 508 class_addMethodsBulk(_Nullable Class cls, _Nonnull const SEL * _Nonnull names,
 509                      _Nonnull const IMP * _Nonnull imps,
 510                      const char * _Nonnull * _Nonnull types, uint32_t count,
 511                      uint32_t * _Nullable outFailedCount)
 512         OBJC_AVAILABLE(10.14, 12.0, 12.0, 5.0, 3.0);
 513 #endif
 514
 515 /**
 516  * Replaces multiple methods in a class in bulk. This amortizes overhead that
 517  * can be expensive when adding methods one by one with class_replaceMethod.
 518  *
 519  * @param cls The class to modify.
 520  * @param names An array of selectors for the methods to replace.
 521  * @param imps An array of functions will be the new method implementantations.
 522  * @param types An array of strings that describe the types of each method's
 523  *              arguments.
 524  * @param count The number of items in the names, imps, and types arrays.
 525  */
 526 #if __OBJC2__
 527 OBJC_EXPORT void
 528 class_replaceMethodsBulk(_Nullable Class cls,
 529                          _Nonnull const SEL * _Nonnull names,
 530                          _Nonnull const IMP * _Nonnull imps,
 531                          const char * _Nonnull * _Nonnull types,
 532                          uint32_t count)
 533         OBJC_AVAILABLE(10.14, 12.0, 12.0, 5.0, 3.0);
 534 #endif
 535
 536
 537 // Instance-specific instance variable layout. This is no longer implemented.
 538
 539 OBJC_EXPORT void
 540 _class_setIvarLayoutAccessor(Class _Nullable cls,
 541                              const uint8_t* _Nullable (* _Nonnull accessor)
 542                                (id _Nullable object))
 543     UNAVAILABLE_ATTRIBUTE;
 544
 545 OBJC_EXPORT const uint8_t * _Nullable
 546 _object_getIvarLayout(Class _Nullable cls, id _Nullable object)
 547     UNAVAILABLE_ATTRIBUTE;
 548
 549
 550 /*
 551   "Unknown" includes non-object ivars and non-ARC non-__weak ivars
 552   "Strong" includes ARC __strong ivars
 553   "Weak" includes ARC and new MRC __weak ivars
 554   "Unretained" includes ARC __unsafe_unretained and old GC+MRC __weak ivars
 555 */
 556 typedef enum {
 557     objc_ivar_memoryUnknown,     // unknown / unknown
 558     objc_ivar_memoryStrong,      // direct access / objc_storeStrong
 559     objc_ivar_memoryWeak,        // objc_loadWeak[Retained] / objc_storeWeak
 560     objc_ivar_memoryUnretained   // direct access / direct access
 561 } objc_ivar_memory_management_t;
 562
 563 OBJC_EXPORT objc_ivar_memory_management_t
 564 _class_getIvarMemoryManagement(Class _Nullable cls, Ivar _Nonnull ivar)
 565     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0, 2.0);
 566
 567 OBJC_EXPORT BOOL _class_isFutureClass(Class _Nullable cls)
 568     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0);
 569
 570
 571 // API to only be called by root classes like NSObject or NSProxy
 572
 573 OBJC_EXPORT
 574 id _Nonnull
 575 _objc_rootRetain(id _Nonnull obj)
 576     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 577
 578 OBJC_EXPORT
 579 void
 580 _objc_rootRelease(id _Nonnull obj)
 581     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 582
 583 OBJC_EXPORT
 584 bool
 585 _objc_rootReleaseWasZero(id _Nonnull obj)
 586     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 587
 588 OBJC_EXPORT
 589 bool
 590 _objc_rootTryRetain(id _Nonnull obj)
 591     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 592
 593 OBJC_EXPORT
 594 bool
 595 _objc_rootIsDeallocating(id _Nonnull obj)
 596     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 597
 598 OBJC_EXPORT
 599 id _Nonnull
 600 _objc_rootAutorelease(id _Nonnull obj)
 601     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 602
 603 OBJC_EXPORT
 604 uintptr_t
 605 _objc_rootRetainCount(id _Nonnull obj)
 606     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 607
 608 OBJC_EXPORT
 609 id _Nonnull
 610 _objc_rootInit(id _Nonnull obj)
 611     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 612
 613 OBJC_EXPORT
 614 id _Nullable
 615 _objc_rootAllocWithZone(Class _Nonnull cls, malloc_zone_t * _Nullable zone)
 616     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 617
 618 OBJC_EXPORT
 619 id _Nullable
 620 _objc_rootAlloc(Class _Nonnull cls)
 621     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 622
 623 OBJC_EXPORT
 624 void
 625 _objc_rootDealloc(id _Nonnull obj)
 626     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 627
 628 OBJC_EXPORT
 629 void
 630 _objc_rootFinalize(id _Nonnull obj)
 631     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 632
 633 OBJC_EXPORT
 634 malloc_zone_t * _Nonnull
 635 _objc_rootZone(id _Nonnull obj)
 636     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 637
 638 OBJC_EXPORT
 639 uintptr_t
 640 _objc_rootHash(id _Nonnull obj)
 641     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 642
 643 OBJC_EXPORT
 644 void * _Nonnull
 645 objc_autoreleasePoolPush(void)
 646     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 647
 648 OBJC_EXPORT
 649 void
 650 objc_autoreleasePoolPop(void * _Nonnull context)
 651     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 652
 653
 654 OBJC_EXPORT id _Nullable
 655 objc_alloc(Class _Nullable cls)
 656     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0);
 657
 658 OBJC_EXPORT id _Nullable
 659 objc_allocWithZone(Class _Nullable cls)
 660     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0);
 661
 662 OBJC_EXPORT id _Nullable
 663 objc_retain(id _Nullable obj)
 664     __asm__("_objc_retain")
 665     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 666
 667 OBJC_EXPORT void
 668 objc_release(id _Nullable obj)
 669     __asm__("_objc_release")
 670     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 671
 672 OBJC_EXPORT id _Nullable
 673 objc_autorelease(id _Nullable obj)
 674     __asm__("_objc_autorelease")
 675     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 676
 677 // Prepare a value at +1 for return through a +0 autoreleasing convention.
 678 OBJC_EXPORT id _Nullable
 679 objc_autoreleaseReturnValue(id _Nullable obj)
 680     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 681
 682 // Prepare a value at +0 for return through a +0 autoreleasing convention.
 683 OBJC_EXPORT id _Nullable
 684 objc_retainAutoreleaseReturnValue(id _Nullable obj)
 685     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 686
 687 // Accept a value returned through a +0 autoreleasing convention for use at +1.
 688 OBJC_EXPORT id _Nullable
 689 objc_retainAutoreleasedReturnValue(id _Nullable obj)
 690     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 691
 692 // Accept a value returned through a +0 autoreleasing convention for use at +0.
 693 OBJC_EXPORT id _Nullable
 694 objc_unsafeClaimAutoreleasedReturnValue(id _Nullable obj)
 695     OBJC_AVAILABLE(10.11, 9.0, 9.0, 1.0, 2.0);
 696
 697 OBJC_EXPORT void
 698 objc_storeStrong(id _Nullable * _Nonnull location, id _Nullable obj)
 699     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 700
 701 OBJC_EXPORT id _Nullable
 702 objc_retainAutorelease(id _Nullable obj)
 703     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 704
 705 // obsolete.
 706 OBJC_EXPORT id _Nullable
 707 objc_retain_autorelease(id _Nullable obj)
 708     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 709
 710 OBJC_EXPORT id _Nullable
 711 objc_loadWeakRetained(id _Nullable * _Nonnull location)
 712     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 713
 714 OBJC_EXPORT id _Nullable
 715 objc_initWeak(id _Nullable * _Nonnull location, id _Nullable val)
 716     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 717
 718 // Like objc_storeWeak, but stores nil if the new object is deallocating
 719 // or the new object's class does not support weak references.
 720 // Returns the value stored (either the new object or nil).
 721 OBJC_EXPORT id _Nullable
 722 objc_storeWeakOrNil(id _Nullable * _Nonnull location, id _Nullable obj)
 723     OBJC_AVAILABLE(10.11, 9.0, 9.0, 1.0, 2.0);
 724
 725 // Like objc_initWeak, but stores nil if the new object is deallocating
 726 // or the new object's class does not support weak references.
 727 // Returns the value stored (either the new object or nil).
 728 OBJC_EXPORT id _Nullable
 729 objc_initWeakOrNil(id _Nullable * _Nonnull location, id _Nullable val)
 730     OBJC_AVAILABLE(10.11, 9.0, 9.0, 1.0, 2.0);
 731
 732 OBJC_EXPORT void
 733 objc_destroyWeak(id _Nullable * _Nonnull location)
 734     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 735
 736 OBJC_EXPORT void
 737 objc_copyWeak(id _Nullable * _Nonnull to, id _Nullable * _Nonnull from)
 738     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 739
 740 OBJC_EXPORT void
 741 objc_moveWeak(id _Nullable * _Nonnull to, id _Nullable * _Nonnull from)
 742     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 743
 744
 745 OBJC_EXPORT void
 746 _objc_autoreleasePoolPrint(void)
 747     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 748
 749 OBJC_EXPORT BOOL
 750 objc_should_deallocate(id _Nonnull object)
 751     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 752
 753 OBJC_EXPORT void
 754 objc_clear_deallocating(id _Nonnull object)
 755     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 756
 757
 758 // to make CF link for now
 759
 760 OBJC_EXPORT void * _Nonnull
 761 _objc_autoreleasePoolPush(void)
 762     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 763
 764 OBJC_EXPORT void
 765 _objc_autoreleasePoolPop(void * _Nonnull context)
 766     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 767
 768
 769 // Extra @encode data for XPC, or NULL
 770 OBJC_EXPORT const char * _Nullable
 771 _protocol_getMethodTypeEncoding(Protocol * _Nonnull proto, SEL _Nonnull sel,
 772                                 BOOL isRequiredMethod, BOOL isInstanceMethod)
 773     OBJC_AVAILABLE(10.8, 6.0, 9.0, 1.0, 2.0);
 774
 775
 776 // API to only be called by classes that provide their own reference count storage
 777
 778 OBJC_EXPORT void
 779 _objc_deallocOnMainThreadHelper(void * _Nullable context)
 780     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 781
 782 // On async versus sync deallocation and the _dealloc2main flag
 783 //
 784 // Theory:
 785 //
 786 // If order matters, then code must always: [self dealloc].
 787 // If order doesn't matter, then always async should be safe.
 788 //
 789 // Practice:
 790 //
 791 // The _dealloc2main bit is set for GUI objects that may be retained by other
 792 // threads. Once deallocation begins on the main thread, doing more async
 793 // deallocation will at best cause extra UI latency and at worst cause
 794 // use-after-free bugs in unretained delegate style patterns. Yes, this is
 795 // extremely fragile. Yes, in the long run, developers should switch to weak
 796 // references.
 797 //
 798 // Note is NOT safe to do any equality check against the result of
 799 // dispatch_get_current_queue(). The main thread can and does drain more than
 800 // one dispatch queue. That is why we call pthread_main_np().
 801 //
 802
 803 typedef enum {
 804     _OBJC_RESURRECT_OBJECT = -1,        /* _logicBlock has called -retain, and scheduled a -release for later. */
 805     _OBJC_DEALLOC_OBJECT_NOW = 1,       /* call [self dealloc] immediately. */
 806     _OBJC_DEALLOC_OBJECT_LATER = 2      /* call [self dealloc] on the main queue. */
 807 } _objc_object_disposition_t;
 808
 809 #define _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC_BLOCK(_rc_ivar, _logicBlock)        \
 810     -(id)retain {                                                               \
 811         /* this will fail to compile if _rc_ivar is an unsigned type */         \
 812         int _retain_count_ivar_must_not_be_unsigned[0L - (__typeof__(_rc_ivar))-1] __attribute__((unused)); \
 813         __typeof__(_rc_ivar) _prev = __sync_fetch_and_add(&_rc_ivar, 2);        \
 814         if (_prev < -2) { /* specifically allow resurrection from logical 0. */ \
 815             __builtin_trap(); /* BUG: retain of over-released ref */            \
 816         }                                                                       \
 817         return self;                                                            \
 818     }                                                                           \
 819     -(oneway void)release {                                                     \
 820         __typeof__(_rc_ivar) _prev = __sync_fetch_and_sub(&_rc_ivar, 2);        \
 821         if (_prev > 0) {                                                        \
 822             return;                                                             \
 823         } else if (_prev < 0) {                                                 \
 824             __builtin_trap(); /* BUG: over-release */                           \
 825         }                                                                       \
 826         _objc_object_disposition_t fate = _logicBlock(self);                    \
 827         if (fate == _OBJC_RESURRECT_OBJECT) {                                   \
 828             return;                                                             \
 829         }                                                                       \
 830         /* mark the object as deallocating. */                                  \
 831         if (!__sync_bool_compare_and_swap(&_rc_ivar, -2, 1)) {                  \
 832             __builtin_trap(); /* BUG: dangling ref did a retain */              \
 833         }                                                                       \
 834         if (fate == _OBJC_DEALLOC_OBJECT_NOW) {                                 \
 835             [self dealloc];                                                     \
 836         } else if (fate == _OBJC_DEALLOC_OBJECT_LATER) {                        \
 837             dispatch_barrier_async_f(dispatch_get_main_queue(), self,           \
 838                 _objc_deallocOnMainThreadHelper);                               \
 839         } else {                                                                \
 840             __builtin_trap(); /* BUG: bogus fate value */                       \
 841         }                                                                       \
 842     }                                                                           \
 843     -(NSUInteger)retainCount {                                                  \
 844         return (_rc_ivar + 2) >> 1;                                             \
 845     }                                                                           \
 846     -(BOOL)_tryRetain {                                                         \
 847         __typeof__(_rc_ivar) _prev;                                             \
 848         do {                                                                    \
 849             _prev = _rc_ivar;                                                   \
 850             if (_prev & 1) {                                                    \
 851                 return 0;                                                       \
 852             } else if (_prev == -2) {                                           \
 853                 return 0;                                                       \
 854             } else if (_prev < -2) {                                            \
 855                 __builtin_trap(); /* BUG: over-release elsewhere */             \
 856             }                                                                   \
 857         } while ( ! __sync_bool_compare_and_swap(&_rc_ivar, _prev, _prev + 2)); \
 858         return 1;                                                               \
 859     }                                                                           \
 860     -(BOOL)_isDeallocating {                                                    \
 861         if (_rc_ivar == -2) {                                                   \
 862             return 1;                                                           \
 863         } else if (_rc_ivar < -2) {                                             \
 864             __builtin_trap(); /* BUG: over-release elsewhere */                 \
 865         }                                                                       \
 866         return _rc_ivar & 1;                                                    \
 867     }
 868
 869 #define _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC(_rc_ivar, _dealloc2main)            \
 870     _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC_BLOCK(_rc_ivar, (^(id _self_ __attribute__((unused))) { \
 871         if (_dealloc2main && !pthread_main_np()) {                              \
 872             return _OBJC_DEALLOC_OBJECT_LATER;                                  \
 873         } else {                                                                \
 874             return _OBJC_DEALLOC_OBJECT_NOW;                                    \
 875         }                                                                       \
 876     }))
 877
 878 #define _OBJC_SUPPORTED_INLINE_REFCNT(_rc_ivar) _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC(_rc_ivar, 0)
 879 #define _OBJC_SUPPORTED_INLINE_REFCNT_WITH_DEALLOC2MAIN(_rc_ivar) _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC(_rc_ivar, 1)
 880
 881 __END_DECLS
 882
 883 #endif