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 // This symbol is exported only from debug builds of libobjc itself.
  61 #if defined(OBJC_IS_DEBUG_BUILD)
  62 OBJC_EXPORT void _objc_isDebugBuild(void);
  63 #endif
  64
  65 // In-place construction of an Objective-C class.
  66 // cls and metacls must each be OBJC_MAX_CLASS_SIZE bytes.
  67 // Returns nil if a class with the same name already exists.
  68 // Returns nil if the superclass is under construction.
  69 // Call objc_registerClassPair() when you are done.
  70 OBJC_EXPORT Class _Nullable
  71 objc_initializeClassPair(Class _Nullable superclass, const char * _Nonnull name,
  72                          Class _Nonnull cls, Class _Nonnull metacls)
  73     OBJC_AVAILABLE(10.6, 3.0, 9.0, 1.0, 2.0);
  74
  75 // Class and metaclass construction from a compiler-generated memory image.
  76 // cls and cls->isa must each be OBJC_MAX_CLASS_SIZE bytes.
  77 // Extra bytes not used the the metadata must be zero.
  78 // info is the same objc_image_info that would be emitted by a static compiler.
  79 // Returns nil if a class with the same name already exists.
  80 // Returns nil if the superclass is nil and the class is not marked as a root.
  81 // Returns nil if the superclass is under construction.
  82 // Do not call objc_registerClassPair().
  83 #if __OBJC2__
  84 struct objc_image_info;
  85 OBJC_EXPORT Class _Nullable
  86 objc_readClassPair(Class _Nonnull cls,
  87                    const struct objc_image_info * _Nonnull info)
  88     OBJC_AVAILABLE(10.10, 8.0, 9.0, 1.0, 2.0);
  89 #endif
  90
  91 // Batch object allocation using malloc_zone_batch_malloc().
  92 OBJC_EXPORT unsigned
  93 class_createInstances(Class _Nullable cls, size_t extraBytes,
  94                       id _Nonnull * _Nonnull results, unsigned num_requested)
  95     OBJC_AVAILABLE(10.7, 4.3, 9.0, 1.0, 2.0)
  96     OBJC_ARC_UNAVAILABLE;
  97
  98 // Get the isa pointer written into objects just before being freed.
  99 OBJC_EXPORT Class _Nonnull
 100 _objc_getFreedObjectClass(void)
 101     OBJC_AVAILABLE(10.0, 2.0, 9.0, 1.0, 2.0);
 102
 103 // env NSObjCMessageLoggingEnabled
 104 OBJC_EXPORT void
 105 instrumentObjcMessageSends(BOOL flag)
 106     OBJC_AVAILABLE(10.0, 2.0, 9.0, 1.0, 2.0);
 107
 108 // Initializer called by libSystem
 109 OBJC_EXPORT void
 110 _objc_init(void)
 111 #if __OBJC2__
 112     OBJC_AVAILABLE(10.8, 6.0, 9.0, 1.0, 2.0);
 113 #else
 114     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0, 2.0);
 115 #endif
 116
 117 // fork() safety called by libSystem
 118 OBJC_EXPORT void
 119 _objc_atfork_prepare(void)
 120     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0, 2.0);
 121
 122 OBJC_EXPORT void
 123 _objc_atfork_parent(void)
 124     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0, 2.0);
 125
 126 OBJC_EXPORT void
 127 _objc_atfork_child(void)
 128     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0, 2.0);
 129
 130 // Return YES if GC is on and `object` is a GC allocation.
 131 OBJC_EXPORT BOOL
 132 objc_isAuto(id _Nullable object)
 133     __OSX_DEPRECATED(10.4, 10.8, "it always returns NO")
 134     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE
 135     __WATCHOS_UNAVAILABLE __BRIDGEOS_UNAVAILABLE;
 136
 137 // GC debugging
 138 OBJC_EXPORT BOOL
 139 objc_dumpHeap(char * _Nonnull filename, unsigned long length)
 140     __OSX_DEPRECATED(10.4, 10.8, "it always returns NO")
 141     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE
 142     __WATCHOS_UNAVAILABLE __BRIDGEOS_UNAVAILABLE;
 143
 144 // GC startup callback from Foundation
 145 OBJC_EXPORT malloc_zone_t * _Nullable
 146 objc_collect_init(int (* _Nonnull callback)(void))
 147     __OSX_DEPRECATED(10.4, 10.8, "it does nothing")
 148     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE
 149     __WATCHOS_UNAVAILABLE __BRIDGEOS_UNAVAILABLE;
 150
 151 // Plainly-implemented GC barriers. Rosetta used to use these.
 152 OBJC_EXPORT id _Nullable
 153 objc_assign_strongCast_generic(id _Nullable value, id _Nullable * _Nonnull dest)
 154     UNAVAILABLE_ATTRIBUTE;
 155
 156 OBJC_EXPORT id _Nullable
 157 objc_assign_global_generic(id _Nullable value, id _Nullable * _Nonnull dest)
 158     UNAVAILABLE_ATTRIBUTE;
 159
 160 OBJC_EXPORT id _Nullable
 161 objc_assign_threadlocal_generic(id _Nullable value,
 162                                 id _Nullable * _Nonnull dest)
 163     UNAVAILABLE_ATTRIBUTE;
 164
 165 OBJC_EXPORT id _Nullable
 166 objc_assign_ivar_generic(id _Nullable value, id _Nonnull dest, ptrdiff_t offset)
 167     UNAVAILABLE_ATTRIBUTE;
 168
 169 // GC preflight for an app executable.
 170 // 1: some slice requires GC
 171 // 0: no slice requires GC
 172 // -1: I/O or file format error
 173 OBJC_EXPORT int
 174 objc_appRequiresGC(int fd)
 175     __OSX_AVAILABLE(10.11)
 176     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE
 177     __WATCHOS_UNAVAILABLE __BRIDGEOS_UNAVAILABLE;
 178
 179 // Install missing-class callback. Used by the late unlamented ZeroLink.
 180 OBJC_EXPORT void
 181 _objc_setClassLoader(BOOL (* _Nonnull newClassLoader)(const char * _Nonnull))
 182     OBJC2_UNAVAILABLE;
 183
 184 #if !(TARGET_OS_OSX && !TARGET_OS_IOSMAC && __i386__)
 185 OBJC_EXPORT void
 186 _objc_setClassCopyFixupHandler(void (* _Nonnull newFixupHandler)
 187     (Class _Nonnull oldClass, Class _Nonnull newClass));
 188 // fixme work around bug in Swift
 189 //    OBJC_AVAILABLE(10.14, 12.0, 12.0, 5.0, 3.0)
 190 #endif
 191
 192 // Install handler for allocation failures.
 193 // Handler may abort, or throw, or provide an object to return.
 194 OBJC_EXPORT void
 195 _objc_setBadAllocHandler(id _Nullable (* _Nonnull newHandler)
 196                            (Class _Nullable isa))
 197     OBJC_AVAILABLE(10.8, 6.0, 9.0, 1.0, 2.0);
 198
 199 // Used by ExceptionHandling.framework
 200 #if !__OBJC2__
 201 OBJC_EXPORT void
 202 _objc_error(id _Nullable rcv, const char * _Nonnull fmt, va_list args)
 203     __attribute__((noreturn))
 204     __OSX_DEPRECATED(10.0, 10.5, "use other logging facilities instead")
 205     __IOS_UNAVAILABLE __TVOS_UNAVAILABLE
 206     __WATCHOS_UNAVAILABLE __BRIDGEOS_UNAVAILABLE;
 207
 208 #endif
 209
 210
 211 /**
 212  * Returns the names of all the classes within a library.
 213  *
 214  * @param image The mach header for library or framework you are inquiring about.
 215  * @param outCount The number of class names returned.
 216  *
 217  * @return An array of C strings representing the class names.
 218  */
 219 OBJC_EXPORT const char * _Nonnull * _Nullable
 220 objc_copyClassNamesForImageHeader(const struct mach_header * _Nonnull mh,
 221                                   unsigned int * _Nullable outCount)
 222     OBJC_AVAILABLE(10.14, 12.0, 12.0, 5.0, 3.0);
 223
 224 // Tagged pointer objects.
 225
 226 #if __LP64__
 227 #define OBJC_HAVE_TAGGED_POINTERS 1
 228 #endif
 229
 230 #if OBJC_HAVE_TAGGED_POINTERS
 231
 232 // Tagged pointer layout and usage is subject to change on different OS versions.
 233
 234 // Tag indexes 0..<7 have a 60-bit payload.
 235 // Tag index 7 is reserved.
 236 // Tag indexes 8..<264 have a 52-bit payload.
 237 // Tag index 264 is reserved.
 238
 239 #if __has_feature(objc_fixed_enum)  ||  __cplusplus >= 201103L
 240 enum objc_tag_index_t : uint16_t
 241 #else
 242 typedef uint16_t objc_tag_index_t;
 243 enum
 244 #endif
 245 {
 246     // 60-bit payloads
 247     OBJC_TAG_NSAtom            = 0,
 248     OBJC_TAG_1                 = 1,
 249     OBJC_TAG_NSString          = 2,
 250     OBJC_TAG_NSNumber          = 3,
 251     OBJC_TAG_NSIndexPath       = 4,
 252     OBJC_TAG_NSManagedObjectID = 5,
 253     OBJC_TAG_NSDate            = 6,
 254
 255     // 60-bit reserved
 256     OBJC_TAG_RESERVED_7        = 7,
 257
 258     // 52-bit payloads
 259     OBJC_TAG_Photos_1          = 8,
 260     OBJC_TAG_Photos_2          = 9,
 261     OBJC_TAG_Photos_3          = 10,
 262     OBJC_TAG_Photos_4          = 11,
 263     OBJC_TAG_XPC_1             = 12,
 264     OBJC_TAG_XPC_2             = 13,
 265     OBJC_TAG_XPC_3             = 14,
 266     OBJC_TAG_XPC_4             = 15,
 267
 268     OBJC_TAG_First60BitPayload = 0,
 269     OBJC_TAG_Last60BitPayload  = 6,
 270     OBJC_TAG_First52BitPayload = 8,
 271     OBJC_TAG_Last52BitPayload  = 263,
 272
 273     OBJC_TAG_RESERVED_264      = 264
 274 };
 275 #if __has_feature(objc_fixed_enum)  &&  !defined(__cplusplus)
 276 typedef enum objc_tag_index_t objc_tag_index_t;
 277 #endif
 278
 279
 280 // Returns true if tagged pointers are enabled.
 281 // The other functions below must not be called if tagged pointers are disabled.
 282 static inline bool
 283 _objc_taggedPointersEnabled(void);
 284
 285 // Register a class for a tagged pointer tag.
 286 // Aborts if the tag is invalid or already in use.
 287 OBJC_EXPORT void
 288 _objc_registerTaggedPointerClass(objc_tag_index_t tag, Class _Nonnull cls)
 289     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0);
 290
 291 // Returns the registered class for the given tag.
 292 // Returns nil if the tag is valid but has no registered class.
 293 // Aborts if the tag is invalid.
 294 OBJC_EXPORT Class _Nullable
 295 _objc_getClassForTag(objc_tag_index_t tag)
 296     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0);
 297
 298 // Create a tagged pointer object with the given tag and payload.
 299 // Assumes the tag is valid.
 300 // Assumes tagged pointers are enabled.
 301 // The payload will be silently truncated to fit.
 302 static inline void * _Nonnull
 303 _objc_makeTaggedPointer(objc_tag_index_t tag, uintptr_t payload);
 304
 305 // Return true if ptr is a tagged pointer object.
 306 // Does not check the validity of ptr's class.
 307 static inline bool
 308 _objc_isTaggedPointer(const void * _Nullable ptr);
 309
 310 // Extract the tag value from the given tagged pointer object.
 311 // Assumes ptr is a valid tagged pointer object.
 312 // Does not check the validity of ptr's tag.
 313 static inline objc_tag_index_t
 314 _objc_getTaggedPointerTag(const void * _Nullable ptr);
 315
 316 // Extract the payload from the given tagged pointer object.
 317 // Assumes ptr is a valid tagged pointer object.
 318 // The payload value is zero-extended.
 319 static inline uintptr_t
 320 _objc_getTaggedPointerValue(const void * _Nullable ptr);
 321
 322 // Extract the payload from the given tagged pointer object.
 323 // Assumes ptr is a valid tagged pointer object.
 324 // The payload value is sign-extended.
 325 static inline intptr_t
 326 _objc_getTaggedPointerSignedValue(const void * _Nullable ptr);
 327
 328 // Don't use the values below. Use the declarations above.
 329
 330 #if (TARGET_OS_OSX || TARGET_OS_IOSMAC) && __x86_64__
 331     // 64-bit Mac - tag bit is LSB
 332 #   define OBJC_MSB_TAGGED_POINTERS 0
 333 #else
 334     // Everything else - tag bit is MSB
 335 #   define OBJC_MSB_TAGGED_POINTERS 1
 336 #endif
 337
 338 #define _OBJC_TAG_INDEX_MASK 0x7
 339 // array slot includes the tag bit itself
 340 #define _OBJC_TAG_SLOT_COUNT 16
 341 #define _OBJC_TAG_SLOT_MASK 0xf
 342
 343 #define _OBJC_TAG_EXT_INDEX_MASK 0xff
 344 // array slot has no extra bits
 345 #define _OBJC_TAG_EXT_SLOT_COUNT 256
 346 #define _OBJC_TAG_EXT_SLOT_MASK 0xff
 347
 348 #if OBJC_MSB_TAGGED_POINTERS
 349 #   define _OBJC_TAG_MASK (1UL<<63)
 350 #   define _OBJC_TAG_INDEX_SHIFT 60
 351 #   define _OBJC_TAG_SLOT_SHIFT 60
 352 #   define _OBJC_TAG_PAYLOAD_LSHIFT 4
 353 #   define _OBJC_TAG_PAYLOAD_RSHIFT 4
 354 #   define _OBJC_TAG_EXT_MASK (0xfUL<<60)
 355 #   define _OBJC_TAG_EXT_INDEX_SHIFT 52
 356 #   define _OBJC_TAG_EXT_SLOT_SHIFT 52
 357 #   define _OBJC_TAG_EXT_PAYLOAD_LSHIFT 12
 358 #   define _OBJC_TAG_EXT_PAYLOAD_RSHIFT 12
 359 #else
 360 #   define _OBJC_TAG_MASK 1UL
 361 #   define _OBJC_TAG_INDEX_SHIFT 1
 362 #   define _OBJC_TAG_SLOT_SHIFT 0
 363 #   define _OBJC_TAG_PAYLOAD_LSHIFT 0
 364 #   define _OBJC_TAG_PAYLOAD_RSHIFT 4
 365 #   define _OBJC_TAG_EXT_MASK 0xfUL
 366 #   define _OBJC_TAG_EXT_INDEX_SHIFT 4
 367 #   define _OBJC_TAG_EXT_SLOT_SHIFT 4
 368 #   define _OBJC_TAG_EXT_PAYLOAD_LSHIFT 0
 369 #   define _OBJC_TAG_EXT_PAYLOAD_RSHIFT 12
 370 #endif
 371
 372 extern uintptr_t objc_debug_taggedpointer_obfuscator;
 373
 374 static inline void * _Nonnull
 375 _objc_encodeTaggedPointer(uintptr_t ptr)
 376 {
 377     return (void *)(objc_debug_taggedpointer_obfuscator ^ ptr);
 378 }
 379
 380 static inline uintptr_t
 381 _objc_decodeTaggedPointer(const void * _Nullable ptr)
 382 {
 383     return (uintptr_t)ptr ^ objc_debug_taggedpointer_obfuscator;
 384 }
 385
 386 static inline bool
 387 _objc_taggedPointersEnabled(void)
 388 {
 389     extern uintptr_t objc_debug_taggedpointer_mask;
 390     return (objc_debug_taggedpointer_mask != 0);
 391 }
 392
 393 static inline void * _Nonnull
 394 _objc_makeTaggedPointer(objc_tag_index_t tag, uintptr_t value)
 395 {
 396     // PAYLOAD_LSHIFT and PAYLOAD_RSHIFT are the payload extraction shifts.
 397     // They are reversed here for payload insertion.
 398
 399     // assert(_objc_taggedPointersEnabled());
 400     if (tag <= OBJC_TAG_Last60BitPayload) {
 401         // assert(((value << _OBJC_TAG_PAYLOAD_RSHIFT) >> _OBJC_TAG_PAYLOAD_LSHIFT) == value);
 402         uintptr_t result =
 403             (_OBJC_TAG_MASK |
 404              ((uintptr_t)tag << _OBJC_TAG_INDEX_SHIFT) |
 405              ((value << _OBJC_TAG_PAYLOAD_RSHIFT) >> _OBJC_TAG_PAYLOAD_LSHIFT));
 406         return _objc_encodeTaggedPointer(result);
 407     } else {
 408         // assert(tag >= OBJC_TAG_First52BitPayload);
 409         // assert(tag <= OBJC_TAG_Last52BitPayload);
 410         // assert(((value << _OBJC_TAG_EXT_PAYLOAD_RSHIFT) >> _OBJC_TAG_EXT_PAYLOAD_LSHIFT) == value);
 411         uintptr_t result =
 412             (_OBJC_TAG_EXT_MASK |
 413              ((uintptr_t)(tag - OBJC_TAG_First52BitPayload) << _OBJC_TAG_EXT_INDEX_SHIFT) |
 414              ((value << _OBJC_TAG_EXT_PAYLOAD_RSHIFT) >> _OBJC_TAG_EXT_PAYLOAD_LSHIFT));
 415         return _objc_encodeTaggedPointer(result);
 416     }
 417 }
 418
 419 static inline bool
 420 _objc_isTaggedPointer(const void * _Nullable ptr)
 421 {
 422     return ((uintptr_t)ptr & _OBJC_TAG_MASK) == _OBJC_TAG_MASK;
 423 }
 424
 425 static inline objc_tag_index_t
 426 _objc_getTaggedPointerTag(const void * _Nullable ptr)
 427 {
 428     // assert(_objc_isTaggedPointer(ptr));
 429     uintptr_t value = _objc_decodeTaggedPointer(ptr);
 430     uintptr_t basicTag = (value >> _OBJC_TAG_INDEX_SHIFT) & _OBJC_TAG_INDEX_MASK;
 431     uintptr_t extTag =   (value >> _OBJC_TAG_EXT_INDEX_SHIFT) & _OBJC_TAG_EXT_INDEX_MASK;
 432     if (basicTag == _OBJC_TAG_INDEX_MASK) {
 433         return (objc_tag_index_t)(extTag + OBJC_TAG_First52BitPayload);
 434     } else {
 435         return (objc_tag_index_t)basicTag;
 436     }
 437 }
 438
 439 static inline uintptr_t
 440 _objc_getTaggedPointerValue(const void * _Nullable ptr)
 441 {
 442     // assert(_objc_isTaggedPointer(ptr));
 443     uintptr_t value = _objc_decodeTaggedPointer(ptr);
 444     uintptr_t basicTag = (value >> _OBJC_TAG_INDEX_SHIFT) & _OBJC_TAG_INDEX_MASK;
 445     if (basicTag == _OBJC_TAG_INDEX_MASK) {
 446         return (value << _OBJC_TAG_EXT_PAYLOAD_LSHIFT) >> _OBJC_TAG_EXT_PAYLOAD_RSHIFT;
 447     } else {
 448         return (value << _OBJC_TAG_PAYLOAD_LSHIFT) >> _OBJC_TAG_PAYLOAD_RSHIFT;
 449     }
 450 }
 451
 452 static inline intptr_t
 453 _objc_getTaggedPointerSignedValue(const void * _Nullable ptr)
 454 {
 455     // assert(_objc_isTaggedPointer(ptr));
 456     uintptr_t value = _objc_decodeTaggedPointer(ptr);
 457     uintptr_t basicTag = (value >> _OBJC_TAG_INDEX_SHIFT) & _OBJC_TAG_INDEX_MASK;
 458     if (basicTag == _OBJC_TAG_INDEX_MASK) {
 459         return ((intptr_t)value << _OBJC_TAG_EXT_PAYLOAD_LSHIFT) >> _OBJC_TAG_EXT_PAYLOAD_RSHIFT;
 460     } else {
 461         return ((intptr_t)value << _OBJC_TAG_PAYLOAD_LSHIFT) >> _OBJC_TAG_PAYLOAD_RSHIFT;
 462     }
 463 }
 464
 465 // OBJC_HAVE_TAGGED_POINTERS
 466 #endif
 467
 468
 469 /**
 470  * Returns the method implementation of an object.
 471  *
 472  * @param obj An Objective-C object.
 473  * @param name An Objective-C selector.
 474  *
 475  * @return The IMP corresponding to the instance method implemented by
 476  * the class of \e obj.
 477  *
 478  * @note Equivalent to:
 479  *
 480  * class_getMethodImplementation(object_getClass(obj), name);
 481  */
 482 OBJC_EXPORT IMP _Nonnull
 483 object_getMethodImplementation(id _Nullable obj, SEL _Nonnull name)
 484     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0);
 485
 486 OBJC_EXPORT IMP _Nonnull
 487 object_getMethodImplementation_stret(id _Nullable obj, SEL _Nonnull name)
 488     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0)
 489     OBJC_ARM64_UNAVAILABLE;
 490
 491
 492 /**
 493  * Adds multiple methods to a class in bulk. This amortizes overhead that can be
 494  * expensive when adding methods one by one with class_addMethod.
 495  *
 496  * @param cls The class to which to add the methods.
 497  * @param names An array of selectors for the methods to add.
 498  * @param imps An array of functions which implement the new methods.
 499  * @param types An array of strings that describe the types of each method's
 500  *              arguments.
 501  * @param count The number of items in the names, imps, and types arrays.
 502  * @param outFiledCount Upon return, contains the number of failed selectors in
 503  *                      the returned array.
 504  *
 505  * @return A NULL-terminated C array of selectors which could not be added. A
 506  * method cannot be added when a method of that name already exists on that
 507  * class. When no failures occur, the return value is \c NULL. When a non-NULL
 508  * value is returned, the caller must free the array with \c free().
 509  *
 510  */
 511 #if __OBJC2__
 512 OBJC_EXPORT _Nullable SEL * _Nullable
 513 class_addMethodsBulk(_Nullable Class cls, _Nonnull const SEL * _Nonnull names,
 514                      _Nonnull const IMP * _Nonnull imps,
 515                      const char * _Nonnull * _Nonnull types, uint32_t count,
 516                      uint32_t * _Nullable outFailedCount)
 517         OBJC_AVAILABLE(10.14, 12.0, 12.0, 5.0, 3.0);
 518 #endif
 519
 520 /**
 521  * Replaces multiple methods in a class in bulk. This amortizes overhead that
 522  * can be expensive when adding methods one by one with class_replaceMethod.
 523  *
 524  * @param cls The class to modify.
 525  * @param names An array of selectors for the methods to replace.
 526  * @param imps An array of functions will be the new method implementantations.
 527  * @param types An array of strings that describe the types of each method's
 528  *              arguments.
 529  * @param count The number of items in the names, imps, and types arrays.
 530  */
 531 #if __OBJC2__
 532 OBJC_EXPORT void
 533 class_replaceMethodsBulk(_Nullable Class cls,
 534                          _Nonnull const SEL * _Nonnull names,
 535                          _Nonnull const IMP * _Nonnull imps,
 536                          const char * _Nonnull * _Nonnull types,
 537                          uint32_t count)
 538         OBJC_AVAILABLE(10.14, 12.0, 12.0, 5.0, 3.0);
 539 #endif
 540
 541
 542 // Instance-specific instance variable layout. This is no longer implemented.
 543
 544 OBJC_EXPORT void
 545 _class_setIvarLayoutAccessor(Class _Nullable cls,
 546                              const uint8_t* _Nullable (* _Nonnull accessor)
 547                                (id _Nullable object))
 548     UNAVAILABLE_ATTRIBUTE;
 549
 550 OBJC_EXPORT const uint8_t * _Nullable
 551 _object_getIvarLayout(Class _Nullable cls, id _Nullable object)
 552     UNAVAILABLE_ATTRIBUTE;
 553
 554
 555 /*
 556   "Unknown" includes non-object ivars and non-ARC non-__weak ivars
 557   "Strong" includes ARC __strong ivars
 558   "Weak" includes ARC and new MRC __weak ivars
 559   "Unretained" includes ARC __unsafe_unretained and old GC+MRC __weak ivars
 560 */
 561 typedef enum {
 562     objc_ivar_memoryUnknown,     // unknown / unknown
 563     objc_ivar_memoryStrong,      // direct access / objc_storeStrong
 564     objc_ivar_memoryWeak,        // objc_loadWeak[Retained] / objc_storeWeak
 565     objc_ivar_memoryUnretained   // direct access / direct access
 566 } objc_ivar_memory_management_t;
 567
 568 OBJC_EXPORT objc_ivar_memory_management_t
 569 _class_getIvarMemoryManagement(Class _Nullable cls, Ivar _Nonnull ivar)
 570     OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0, 2.0);
 571
 572 OBJC_EXPORT BOOL _class_isFutureClass(Class _Nullable cls)
 573     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0);
 574
 575
 576 // API to only be called by root classes like NSObject or NSProxy
 577
 578 OBJC_EXPORT
 579 id _Nonnull
 580 _objc_rootRetain(id _Nonnull obj)
 581     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 582
 583 OBJC_EXPORT
 584 void
 585 _objc_rootRelease(id _Nonnull obj)
 586     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 587
 588 OBJC_EXPORT
 589 bool
 590 _objc_rootReleaseWasZero(id _Nonnull obj)
 591     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 592
 593 OBJC_EXPORT
 594 bool
 595 _objc_rootTryRetain(id _Nonnull obj)
 596     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 597
 598 OBJC_EXPORT
 599 bool
 600 _objc_rootIsDeallocating(id _Nonnull obj)
 601     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 602
 603 OBJC_EXPORT
 604 id _Nonnull
 605 _objc_rootAutorelease(id _Nonnull obj)
 606     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 607
 608 OBJC_EXPORT
 609 uintptr_t
 610 _objc_rootRetainCount(id _Nonnull obj)
 611     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 612
 613 OBJC_EXPORT
 614 id _Nonnull
 615 _objc_rootInit(id _Nonnull obj)
 616     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 617
 618 OBJC_EXPORT
 619 id _Nullable
 620 _objc_rootAllocWithZone(Class _Nonnull cls, malloc_zone_t * _Nullable zone)
 621     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 622
 623 OBJC_EXPORT
 624 id _Nullable
 625 _objc_rootAlloc(Class _Nonnull cls)
 626     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 627
 628 OBJC_EXPORT
 629 void
 630 _objc_rootDealloc(id _Nonnull obj)
 631     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 632
 633 OBJC_EXPORT
 634 void
 635 _objc_rootFinalize(id _Nonnull obj)
 636     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 637
 638 OBJC_EXPORT
 639 malloc_zone_t * _Nonnull
 640 _objc_rootZone(id _Nonnull obj)
 641     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 642
 643 OBJC_EXPORT
 644 uintptr_t
 645 _objc_rootHash(id _Nonnull obj)
 646     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 647
 648 OBJC_EXPORT
 649 void * _Nonnull
 650 objc_autoreleasePoolPush(void)
 651     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 652
 653 OBJC_EXPORT
 654 void
 655 objc_autoreleasePoolPop(void * _Nonnull context)
 656     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 657
 658
 659 OBJC_EXPORT id _Nullable
 660 objc_alloc(Class _Nullable cls)
 661     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0);
 662
 663 OBJC_EXPORT id _Nullable
 664 objc_allocWithZone(Class _Nullable cls)
 665     OBJC_AVAILABLE(10.9, 7.0, 9.0, 1.0, 2.0);
 666
 667 OBJC_EXPORT id _Nullable
 668 objc_alloc_init(Class _Nullable cls)
 669     OBJC_AVAILABLE(10.14, 12.0, 12.0, 5.0, 3.0);
 670 // rdar://44986431 fixme correct availability for objc_alloc_init()
 671
 672 OBJC_EXPORT id _Nullable
 673 objc_retain(id _Nullable obj)
 674     __asm__("_objc_retain")
 675     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 676
 677 OBJC_EXPORT void
 678 objc_release(id _Nullable obj)
 679     __asm__("_objc_release")
 680     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 681
 682 OBJC_EXPORT id _Nullable
 683 objc_autorelease(id _Nullable obj)
 684     __asm__("_objc_autorelease")
 685     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 686
 687 // Prepare a value at +1 for return through a +0 autoreleasing convention.
 688 OBJC_EXPORT id _Nullable
 689 objc_autoreleaseReturnValue(id _Nullable obj)
 690     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 691
 692 // Prepare a value at +0 for return through a +0 autoreleasing convention.
 693 OBJC_EXPORT id _Nullable
 694 objc_retainAutoreleaseReturnValue(id _Nullable obj)
 695     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 696
 697 // Accept a value returned through a +0 autoreleasing convention for use at +1.
 698 OBJC_EXPORT id _Nullable
 699 objc_retainAutoreleasedReturnValue(id _Nullable obj)
 700     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 701
 702 // Accept a value returned through a +0 autoreleasing convention for use at +0.
 703 OBJC_EXPORT id _Nullable
 704 objc_unsafeClaimAutoreleasedReturnValue(id _Nullable obj)
 705     OBJC_AVAILABLE(10.11, 9.0, 9.0, 1.0, 2.0);
 706
 707 OBJC_EXPORT void
 708 objc_storeStrong(id _Nullable * _Nonnull location, id _Nullable obj)
 709     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 710
 711 OBJC_EXPORT id _Nullable
 712 objc_retainAutorelease(id _Nullable obj)
 713     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 714
 715 // obsolete.
 716 OBJC_EXPORT id _Nullable
 717 objc_retain_autorelease(id _Nullable obj)
 718     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 719
 720 OBJC_EXPORT id _Nullable
 721 objc_loadWeakRetained(id _Nullable * _Nonnull location)
 722     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 723
 724 OBJC_EXPORT id _Nullable
 725 objc_initWeak(id _Nullable * _Nonnull location, id _Nullable val)
 726     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 727
 728 // Like objc_storeWeak, but stores nil if the new object is deallocating
 729 // or the new object's class does not support weak references.
 730 // Returns the value stored (either the new object or nil).
 731 OBJC_EXPORT id _Nullable
 732 objc_storeWeakOrNil(id _Nullable * _Nonnull location, id _Nullable obj)
 733     OBJC_AVAILABLE(10.11, 9.0, 9.0, 1.0, 2.0);
 734
 735 // Like objc_initWeak, but stores nil if the new object is deallocating
 736 // or the new object's class does not support weak references.
 737 // Returns the value stored (either the new object or nil).
 738 OBJC_EXPORT id _Nullable
 739 objc_initWeakOrNil(id _Nullable * _Nonnull location, id _Nullable val)
 740     OBJC_AVAILABLE(10.11, 9.0, 9.0, 1.0, 2.0);
 741
 742 OBJC_EXPORT void
 743 objc_destroyWeak(id _Nullable * _Nonnull location)
 744     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 745
 746 OBJC_EXPORT void
 747 objc_copyWeak(id _Nullable * _Nonnull to, id _Nullable * _Nonnull from)
 748     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 749
 750 OBJC_EXPORT void
 751 objc_moveWeak(id _Nullable * _Nonnull to, id _Nullable * _Nonnull from)
 752     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 753
 754
 755 OBJC_EXPORT void
 756 _objc_autoreleasePoolPrint(void)
 757     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 758
 759 OBJC_EXPORT BOOL
 760 objc_should_deallocate(id _Nonnull object)
 761     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 762
 763 OBJC_EXPORT void
 764 objc_clear_deallocating(id _Nonnull object)
 765     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 766
 767
 768 // to make CF link for now
 769
 770 OBJC_EXPORT void * _Nonnull
 771 _objc_autoreleasePoolPush(void)
 772     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 773
 774 OBJC_EXPORT void
 775 _objc_autoreleasePoolPop(void * _Nonnull context)
 776     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 777
 778
 779 // Extra @encode data for XPC, or NULL
 780 OBJC_EXPORT const char * _Nullable
 781 _protocol_getMethodTypeEncoding(Protocol * _Nonnull proto, SEL _Nonnull sel,
 782                                 BOOL isRequiredMethod, BOOL isInstanceMethod)
 783     OBJC_AVAILABLE(10.8, 6.0, 9.0, 1.0, 2.0);
 784
 785
 786 // API to only be called by classes that provide their own reference count storage
 787
 788 OBJC_EXPORT void
 789 _objc_deallocOnMainThreadHelper(void * _Nullable context)
 790     OBJC_AVAILABLE(10.7, 5.0, 9.0, 1.0, 2.0);
 791
 792 // On async versus sync deallocation and the _dealloc2main flag
 793 //
 794 // Theory:
 795 //
 796 // If order matters, then code must always: [self dealloc].
 797 // If order doesn't matter, then always async should be safe.
 798 //
 799 // Practice:
 800 //
 801 // The _dealloc2main bit is set for GUI objects that may be retained by other
 802 // threads. Once deallocation begins on the main thread, doing more async
 803 // deallocation will at best cause extra UI latency and at worst cause
 804 // use-after-free bugs in unretained delegate style patterns. Yes, this is
 805 // extremely fragile. Yes, in the long run, developers should switch to weak
 806 // references.
 807 //
 808 // Note is NOT safe to do any equality check against the result of
 809 // dispatch_get_current_queue(). The main thread can and does drain more than
 810 // one dispatch queue. That is why we call pthread_main_np().
 811 //
 812
 813 typedef enum {
 814     _OBJC_RESURRECT_OBJECT = -1,        /* _logicBlock has called -retain, and scheduled a -release for later. */
 815     _OBJC_DEALLOC_OBJECT_NOW = 1,       /* call [self dealloc] immediately. */
 816     _OBJC_DEALLOC_OBJECT_LATER = 2      /* call [self dealloc] on the main queue. */
 817 } _objc_object_disposition_t;
 818
 819 #define _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC_BLOCK(_rc_ivar, _logicBlock)        \
 820     -(id)retain {                                                               \
 821         /* this will fail to compile if _rc_ivar is an unsigned type */         \
 822         int _retain_count_ivar_must_not_be_unsigned[0L - (__typeof__(_rc_ivar))-1] __attribute__((unused)); \
 823         __typeof__(_rc_ivar) _prev = __sync_fetch_and_add(&_rc_ivar, 2);        \
 824         if (_prev < -2) { /* specifically allow resurrection from logical 0. */ \
 825             __builtin_trap(); /* BUG: retain of over-released ref */            \
 826         }                                                                       \
 827         return self;                                                            \
 828     }                                                                           \
 829     -(oneway void)release {                                                     \
 830         __typeof__(_rc_ivar) _prev = __sync_fetch_and_sub(&_rc_ivar, 2);        \
 831         if (_prev > 0) {                                                        \
 832             return;                                                             \
 833         } else if (_prev < 0) {                                                 \
 834             __builtin_trap(); /* BUG: over-release */                           \
 835         }                                                                       \
 836         _objc_object_disposition_t fate = _logicBlock(self);                    \
 837         if (fate == _OBJC_RESURRECT_OBJECT) {                                   \
 838             return;                                                             \
 839         }                                                                       \
 840         /* mark the object as deallocating. */                                  \
 841         if (!__sync_bool_compare_and_swap(&_rc_ivar, -2, 1)) {                  \
 842             __builtin_trap(); /* BUG: dangling ref did a retain */              \
 843         }                                                                       \
 844         if (fate == _OBJC_DEALLOC_OBJECT_NOW) {                                 \
 845             [self dealloc];                                                     \
 846         } else if (fate == _OBJC_DEALLOC_OBJECT_LATER) {                        \
 847             dispatch_barrier_async_f(dispatch_get_main_queue(), self,           \
 848                 _objc_deallocOnMainThreadHelper);                               \
 849         } else {                                                                \
 850             __builtin_trap(); /* BUG: bogus fate value */                       \
 851         }                                                                       \
 852     }                                                                           \
 853     -(NSUInteger)retainCount {                                                  \
 854         return (_rc_ivar + 2) >> 1;                                             \
 855     }                                                                           \
 856     -(BOOL)_tryRetain {                                                         \
 857         __typeof__(_rc_ivar) _prev;                                             \
 858         do {                                                                    \
 859             _prev = _rc_ivar;                                                   \
 860             if (_prev & 1) {                                                    \
 861                 return 0;                                                       \
 862             } else if (_prev == -2) {                                           \
 863                 return 0;                                                       \
 864             } else if (_prev < -2) {                                            \
 865                 __builtin_trap(); /* BUG: over-release elsewhere */             \
 866             }                                                                   \
 867         } while ( ! __sync_bool_compare_and_swap(&_rc_ivar, _prev, _prev + 2)); \
 868         return 1;                                                               \
 869     }                                                                           \
 870     -(BOOL)_isDeallocating {                                                    \
 871         if (_rc_ivar == -2) {                                                   \
 872             return 1;                                                           \
 873         } else if (_rc_ivar < -2) {                                             \
 874             __builtin_trap(); /* BUG: over-release elsewhere */                 \
 875         }                                                                       \
 876         return _rc_ivar & 1;                                                    \
 877     }
 878
 879 #define _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC(_rc_ivar, _dealloc2main)            \
 880     _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC_BLOCK(_rc_ivar, (^(id _self_ __attribute__((unused))) { \
 881         if (_dealloc2main && !pthread_main_np()) {                              \
 882             return _OBJC_DEALLOC_OBJECT_LATER;                                  \
 883         } else {                                                                \
 884             return _OBJC_DEALLOC_OBJECT_NOW;                                    \
 885         }                                                                       \
 886     }))
 887
 888 #define _OBJC_SUPPORTED_INLINE_REFCNT(_rc_ivar) _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC(_rc_ivar, 0)
 889 #define _OBJC_SUPPORTED_INLINE_REFCNT_WITH_DEALLOC2MAIN(_rc_ivar) _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC(_rc_ivar, 1)
 890
 891 __END_DECLS
 892
 893 #endif