src/block.cpp

   1 /*
   2  * Copyright (c) 2015 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_APACHE_LICENSE_HEADER_START@
   5  *
   6  * Licensed under the Apache License, Version 2.0 (the "License");
   7  * you may not use this file except in compliance with the License.
   8  * You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  *
  18  * @APPLE_APACHE_LICENSE_HEADER_END@
  19  */
  20
  21 #ifdef __BLOCKS__
  22
  23 #if __cplusplus < 201103L
  24 #error Must build with C++11 or later
  25 #endif
  26
  27 #if __has_feature(cxx_exceptions)
  28 #error Must build without C++ exceptions
  29 #endif
  30
  31 extern "C" {
  32 #include "internal.h"
  33 }
  34
  35 #if DISPATCH_DEBUG && DISPATCH_BLOCK_PRIVATE_DATA_DEBUG
  36 #define _dispatch_block_private_data_debug(msg, ...) \
  37                 _dispatch_debug("block_private[%p]: " msg, (this), ##__VA_ARGS__)
  38 #else
  39 #define _dispatch_block_private_data_debug(msg, ...)
  40 #endif
  41
  42 #pragma mark -
  43 #pragma mark _dispatch_block_create
  44
  45 // rdar://20766742 C++ helpers to enable block capture of vouchers and groups
  46
  47 struct dispatch_block_private_data_s {
  48         DISPATCH_BLOCK_PRIVATE_DATA_HEADER();
  49         static void* operator new(size_t) = delete;
  50         static void* operator new [] (size_t) = delete;
  51         explicit inline DISPATCH_ALWAYS_INLINE dispatch_block_private_data_s(
  52                         dispatch_block_flags_t flags, voucher_t voucher,
  53                         pthread_priority_t priority, dispatch_block_t block) noexcept :
  54                         dbpd_magic(), dbpd_flags(flags), dbpd_atomic_flags(),
  55                         dbpd_performed(), dbpd_priority(priority), dbpd_voucher(voucher),
  56                         dbpd_block(block), dbpd_group(), dbpd_queue(), dbpd_thread()
  57         {
  58                 // stack structure constructor, no releases on destruction
  59                 _dispatch_block_private_data_debug("create, block: %p", dbpd_block);
  60         }
  61         inline DISPATCH_ALWAYS_INLINE dispatch_block_private_data_s(
  62                         dispatch_block_private_data_s const &o) noexcept :
  63                         dbpd_magic(DISPATCH_BLOCK_PRIVATE_DATA_MAGIC),
  64                         dbpd_flags(o.dbpd_flags), dbpd_atomic_flags(), dbpd_performed(),
  65                         dbpd_priority(o.dbpd_priority), dbpd_voucher(o.dbpd_voucher),
  66                         dbpd_block(), dbpd_group(), dbpd_queue(), dbpd_thread()
  67         {
  68                 // copy constructor, create copy with retained references
  69                 if (dbpd_voucher) voucher_retain(dbpd_voucher);
  70                 if (o.dbpd_block) dbpd_block = _dispatch_Block_copy(o.dbpd_block);
  71                 _dispatch_block_private_data_debug("copy from %p, block: %p from %p",
  72                                 &o, dbpd_block, o.dbpd_block);
  73                 if (!o.dbpd_magic) return; // No group in initial copy of stack object
  74                 dbpd_group = _dispatch_group_create_and_enter();
  75         }
  76         inline DISPATCH_ALWAYS_INLINE ~dispatch_block_private_data_s() noexcept
  77         {
  78                 _dispatch_block_private_data_debug("destroy%s, block: %p",
  79                                 dbpd_magic ? "" : " (stack)", dbpd_block);
  80                 if (dbpd_magic != DISPATCH_BLOCK_PRIVATE_DATA_MAGIC) return;
  81                 if (dbpd_group) {
  82                         if (!dbpd_performed) dispatch_group_leave(dbpd_group);
  83                         ((void (*)(dispatch_group_t))dispatch_release)(dbpd_group);
  84                 }
  85                 if (dbpd_queue) {
  86                         ((void (*)(os_mpsc_queue_t))_os_object_release_internal)(dbpd_queue);
  87                 }
  88                 if (dbpd_block) Block_release(dbpd_block);
  89                 if (dbpd_voucher) voucher_release(dbpd_voucher);
  90         }
  91 };
  92
  93 dispatch_block_t
  94 _dispatch_block_create(dispatch_block_flags_t flags, voucher_t voucher,
  95                 pthread_priority_t pri, dispatch_block_t block)
  96 {
  97         struct dispatch_block_private_data_s dbpds(flags, voucher, pri, block);
  98         return _dispatch_Block_copy(^{
  99                 // Capture stack object: invokes copy constructor (17094902)
 100                 (void)dbpds;
 101                 _dispatch_block_invoke_direct(&dbpds);
 102         });
 103 }
 104
 105 extern "C" {
 106 // The compiler hides the name of the function it generates, and changes it if
 107 // we try to reference it directly, but the linker still sees it.
 108 extern void DISPATCH_BLOCK_SPECIAL_INVOKE(void *)
 109 #ifdef __linux__
 110                 asm("___dispatch_block_create_block_invoke");
 111 #else
 112                 asm("____dispatch_block_create_block_invoke");
 113 #endif
 114 void (*_dispatch_block_special_invoke)(void*) = DISPATCH_BLOCK_SPECIAL_INVOKE;
 115 }
 116
 117 #endif // __BLOCKS__