runtime/NSObject-internal.h

   1 /*
   2  * Copyright (c) 2019 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 #ifndef _NSOBJECT_INTERNAL_H
  25 #define _NSOBJECT_INTERNAL_H
  26
  27 /*
  28  * WARNING  DANGER  HAZARD  BEWARE  EEK
  29  *
  30  * Everything in this file is for Apple Internal use only.
  31  * These will change in arbitrary OS updates and in unpredictable ways.
  32  * When your program breaks, you get to keep both pieces.
  33  */
  34
  35 /*
  36  * NSObject-internal.h: Private SPI for use by other system frameworks.
  37  */
  38
  39 /***********************************************************************
  40    Autorelease pool implementation
  41
  42    A thread's autorelease pool is a stack of pointers.
  43    Each pointer is either an object to release, or POOL_BOUNDARY which is
  44          an autorelease pool boundary.
  45    A pool token is a pointer to the POOL_BOUNDARY for that pool. When
  46          the pool is popped, every object hotter than the sentinel is released.
  47    The stack is divided into a doubly-linked list of pages. Pages are added
  48          and deleted as necessary.
  49    Thread-local storage points to the hot page, where newly autoreleased
  50          objects are stored.
  51 **********************************************************************/
  52
  53 // structure version number. Only bump if ABI compatability is broken
  54 #define AUTORELEASEPOOL_VERSION 1
  55
  56 // Set this to 1 to mprotect() autorelease pool contents
  57 #define PROTECT_AUTORELEASEPOOL 0
  58
  59 // Set this to 1 to validate the entire autorelease pool header all the time
  60 // (i.e. use check() instead of fastcheck() everywhere)
  61 #define CHECK_AUTORELEASEPOOL (DEBUG)
  62
  63 #ifdef __cplusplus
  64 #include <string.h>
  65 #include <assert.h>
  66 #include <objc/objc.h>
  67 #include <pthread.h>
  68
  69
  70 #ifndef C_ASSERT
  71         #if __has_feature(cxx_static_assert)
  72                 #define C_ASSERT(expr) static_assert(expr, "(" #expr ")!")
  73         #elif __has_feature(c_static_assert)
  74                 #define C_ASSERT(expr) _Static_assert(expr, "(" #expr ")!")
  75         #else
  76                 #define C_ASSERT(expr)
  77         #endif
  78 #endif
  79
  80 // Make ASSERT work when objc-private.h hasn't been included.
  81 #ifndef ASSERT
  82 #define ASSERT(x) assert(x)
  83 #endif
  84
  85 struct magic_t {
  86         static const uint32_t M0 = 0xA1A1A1A1;
  87 #   define M1 "AUTORELEASE!"
  88         static const size_t M1_len = 12;
  89         uint32_t m[4];
  90
  91         magic_t() {
  92                 ASSERT(M1_len == strlen(M1));
  93                 ASSERT(M1_len == 3 * sizeof(m[1]));
  94
  95                 m[0] = M0;
  96                 strncpy((char *)&m[1], M1, M1_len);
  97         }
  98
  99         ~magic_t() {
 100                 // Clear magic before deallocation.
 101                 // This prevents some false positives in memory debugging tools.
 102                 // fixme semantically this should be memset_s(), but the
 103                 // compiler doesn't optimize that at all (rdar://44856676).
 104                 volatile uint64_t *p = (volatile uint64_t *)m;
 105                 p[0] = 0; p[1] = 0;
 106         }
 107
 108         bool check() const {
 109                 return (m[0] == M0 && 0 == strncmp((char *)&m[1], M1, M1_len));
 110         }
 111
 112         bool fastcheck() const {
 113 #if CHECK_AUTORELEASEPOOL
 114                 return check();
 115 #else
 116                 return (m[0] == M0);
 117 #endif
 118         }
 119
 120 #   undef M1
 121 };
 122
 123 class AutoreleasePoolPage;
 124 struct AutoreleasePoolPageData
 125 {
 126 #if SUPPORT_AUTORELEASEPOOL_DEDUP_PTRS
 127     struct AutoreleasePoolEntry {
 128         uintptr_t ptr: 48;
 129         uintptr_t count: 16;
 130
 131         static const uintptr_t maxCount = 65535; // 2^16 - 1
 132     };
 133     static_assert((AutoreleasePoolEntry){ .ptr = MACH_VM_MAX_ADDRESS }.ptr == MACH_VM_MAX_ADDRESS, "MACH_VM_MAX_ADDRESS doesn't fit into AutoreleasePoolEntry::ptr!");
 134 #endif
 135
 136         magic_t const magic;
 137         __unsafe_unretained id *next;
 138         pthread_t const thread;
 139         AutoreleasePoolPage * const parent;
 140         AutoreleasePoolPage *child;
 141         uint32_t const depth;
 142         uint32_t hiwat;
 143
 144         AutoreleasePoolPageData(__unsafe_unretained id* _next, pthread_t _thread, AutoreleasePoolPage* _parent, uint32_t _depth, uint32_t _hiwat)
 145                 : magic(), next(_next), thread(_thread),
 146                   parent(_parent), child(nil),
 147                   depth(_depth), hiwat(_hiwat)
 148         {
 149         }
 150 };
 151
 152
 153 struct thread_data_t
 154 {
 155 #ifdef __LP64__
 156         pthread_t const thread;
 157         uint32_t const hiwat;
 158         uint32_t const depth;
 159 #else
 160         pthread_t const thread;
 161         uint32_t const hiwat;
 162         uint32_t const depth;
 163         uint32_t padding;
 164 #endif
 165 };
 166 C_ASSERT(sizeof(thread_data_t) == 16);
 167
 168 #undef C_ASSERT
 169
 170 #endif
 171 #endif