external/bsd/libc++/dist/libcxx/src/memory.cpp

   1 //===------------------------ memory.cpp ----------------------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is dual licensed under the MIT and the University of Illinois Open
   6 // Source Licenses. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #define _LIBCPP_BUILDING_MEMORY
  11 #include "memory"
  12 #ifndef _LIBCPP_HAS_NO_THREADS
  13 #include "mutex"
  14 #include "thread"
  15 #endif
  16 #include "include/atomic_support.h"
  17
  18 _LIBCPP_BEGIN_NAMESPACE_STD
  19
  20 namespace
  21 {
  22
  23 // NOTE: Relaxed and acq/rel atomics (for increment and decrement respectively)
  24 // should be sufficient for thread safety.
  25 // See https://llvm.org/bugs/show_bug.cgi?id=22803
  26 template <class T>
  27 inline T
  28 increment(T& t) _NOEXCEPT
  29 {
  30     return __libcpp_atomic_add(&t, 1, _AO_Relaxed);
  31 }
  32
  33 template <class T>
  34 inline T
  35 decrement(T& t) _NOEXCEPT
  36 {
  37     return __libcpp_atomic_add(&t, -1, _AO_Acq_Rel);
  38 }
  39
  40 }  // namespace
  41
  42 const allocator_arg_t allocator_arg = allocator_arg_t();
  43
  44 bad_weak_ptr::~bad_weak_ptr() _NOEXCEPT {}
  45
  46 const char*
  47 bad_weak_ptr::what() const _NOEXCEPT
  48 {
  49     return "bad_weak_ptr";
  50 }
  51
  52 __shared_count::~__shared_count()
  53 {
  54 }
  55
  56 void
  57 __shared_count::__add_shared() _NOEXCEPT
  58 {
  59     increment(__shared_owners_);
  60 }
  61
  62 bool
  63 __shared_count::__release_shared() _NOEXCEPT
  64 {
  65     if (decrement(__shared_owners_) == -1)
  66     {
  67         __on_zero_shared();
  68         return true;
  69     }
  70     return false;
  71 }
  72
  73 __shared_weak_count::~__shared_weak_count()
  74 {
  75 }
  76
  77 void
  78 __shared_weak_count::__add_shared() _NOEXCEPT
  79 {
  80     __shared_count::__add_shared();
  81 }
  82
  83 void
  84 __shared_weak_count::__add_weak() _NOEXCEPT
  85 {
  86     increment(__shared_weak_owners_);
  87 }
  88
  89 void
  90 __shared_weak_count::__release_shared() _NOEXCEPT
  91 {
  92     if (__shared_count::__release_shared())
  93         __release_weak();
  94 }
  95
  96 void
  97 __shared_weak_count::__release_weak() _NOEXCEPT
  98 {
  99     if (decrement(__shared_weak_owners_) == -1)
 100         __on_zero_shared_weak();
 101 }
 102
 103 __shared_weak_count*
 104 __shared_weak_count::lock() _NOEXCEPT
 105 {
 106     long object_owners = __libcpp_atomic_load(&__shared_owners_);
 107     while (object_owners != -1)
 108     {
 109         if (__libcpp_atomic_compare_exchange(&__shared_owners_,
 110                                              &object_owners,
 111                                              object_owners+1))
 112             return this;
 113     }
 114     return 0;
 115 }
 116
 117 #if !defined(_LIBCPP_NO_RTTI) || !defined(_LIBCPP_BUILD_STATIC)
 118
 119 const void*
 120 __shared_weak_count::__get_deleter(const type_info&) const _NOEXCEPT
 121 {
 122     return 0;
 123 }
 124
 125 #endif  // _LIBCPP_NO_RTTI
 126
 127 #if defined(_LIBCPP_HAS_C_ATOMIC_IMP) && !defined(_LIBCPP_HAS_NO_THREADS)
 128
 129 static const std::size_t __sp_mut_count = 16;
 130 static pthread_mutex_t mut_back_imp[__sp_mut_count] =
 131 {
 132     PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
 133     PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
 134     PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
 135     PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER
 136 };
 137
 138 static mutex* mut_back = reinterpret_cast<std::mutex*>(mut_back_imp);
 139
 140 _LIBCPP_CONSTEXPR __sp_mut::__sp_mut(void* p) _NOEXCEPT
 141    : __lx(p)
 142 {
 143 }
 144
 145 void
 146 __sp_mut::lock() _NOEXCEPT
 147 {
 148     mutex& m = *static_cast<mutex*>(__lx);
 149     unsigned count = 0;
 150     while (!m.try_lock())
 151     {
 152         if (++count > 16)
 153         {
 154             m.lock();
 155             break;
 156         }
 157         this_thread::yield();
 158     }
 159 }
 160
 161 void
 162 __sp_mut::unlock() _NOEXCEPT
 163 {
 164     static_cast<mutex*>(__lx)->unlock();
 165 }
 166
 167 __sp_mut&
 168 __get_sp_mut(const void* p)
 169 {
 170     static __sp_mut muts[__sp_mut_count]
 171     {
 172         &mut_back[ 0], &mut_back[ 1], &mut_back[ 2], &mut_back[ 3],
 173         &mut_back[ 4], &mut_back[ 5], &mut_back[ 6], &mut_back[ 7],
 174         &mut_back[ 8], &mut_back[ 9], &mut_back[10], &mut_back[11],
 175         &mut_back[12], &mut_back[13], &mut_back[14], &mut_back[15]
 176     };
 177     return muts[hash<const void*>()(p) & (__sp_mut_count-1)];
 178 }
 179
 180 #endif // defined(_LIBCPP_HAS_C_ATOMIC_IMP) && !defined(_LIBCPP_HAS_NO_THREADS)
 181
 182 void
 183 declare_reachable(void*)
 184 {
 185 }
 186
 187 void
 188 declare_no_pointers(char*, size_t)
 189 {
 190 }
 191
 192 void
 193 undeclare_no_pointers(char*, size_t)
 194 {
 195 }
 196
 197 pointer_safety
 198 get_pointer_safety() _NOEXCEPT
 199 {
 200     return pointer_safety::relaxed;
 201 }
 202
 203 void*
 204 __undeclare_reachable(void* p)
 205 {
 206     return p;
 207 }
 208
 209 void*
 210 align(size_t alignment, size_t size, void*& ptr, size_t& space)
 211 {
 212     void* r = nullptr;
 213     if (size <= space)
 214     {
 215         char* p1 = static_cast<char*>(ptr);
 216         char* p2 = reinterpret_cast<char*>(reinterpret_cast<size_t>(p1 + (alignment - 1)) & -alignment);
 217         size_t d = static_cast<size_t>(p2 - p1);
 218         if (d <= space - size)
 219         {
 220             r = p2;
 221             ptr = r;
 222             space -= d;
 223         }
 224     }
 225     return r;
 226 }
 227
 228 _LIBCPP_END_NAMESPACE_STD