1 //===----------------------------------------------------------------------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
10 #ifdef _LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS
11 # define _LIBCPP_SHARED_PTR_DEFINE_LEGACY_INLINE_FUNCTIONS
16 #ifndef _LIBCPP_HAS_NO_THREADS
19 # if defined(__ELF__) && defined(_LIBCPP_LINK_PTHREAD_LIB)
20 # pragma comment(lib, "pthread")
24 #include "include/atomic_support.h"
26 _LIBCPP_BEGIN_NAMESPACE_STD
28 const allocator_arg_t allocator_arg
= allocator_arg_t();
30 bad_weak_ptr::~bad_weak_ptr() noexcept
{}
33 bad_weak_ptr::what() const noexcept
35 return "bad_weak_ptr";
38 __shared_count::~__shared_count()
42 __shared_weak_count::~__shared_weak_count()
46 #if defined(_LIBCPP_SHARED_PTR_DEFINE_LEGACY_INLINE_FUNCTIONS)
48 __shared_count::__add_shared() noexcept
50 __libcpp_atomic_refcount_increment(__shared_owners_
);
54 __shared_count::__release_shared() noexcept
56 if (__libcpp_atomic_refcount_decrement(__shared_owners_
) == -1)
65 __shared_weak_count::__add_shared() noexcept
67 __shared_count::__add_shared();
71 __shared_weak_count::__add_weak() noexcept
73 __libcpp_atomic_refcount_increment(__shared_weak_owners_
);
77 __shared_weak_count::__release_shared() noexcept
79 if (__shared_count::__release_shared())
82 #endif // _LIBCPP_SHARED_PTR_DEFINE_LEGACY_INLINE_FUNCTIONS
85 __shared_weak_count::__release_weak() noexcept
87 // NOTE: The acquire load here is an optimization of the very
88 // common case where a shared pointer is being destructed while
89 // having no other contended references.
91 // BENEFIT: We avoid expensive atomic stores like XADD and STREX
92 // in a common case. Those instructions are slow and do nasty
95 // IS THIS SAFE? Yes. During weak destruction, if we see that we
96 // are the last reference, we know that no-one else is accessing
97 // us. If someone were accessing us, then they would be doing so
98 // while the last shared / weak_ptr was being destructed, and
99 // that's undefined anyway.
101 // If we see anything other than a 0, then we have possible
102 // contention, and need to use an atomicrmw primitive.
103 // The same arguments don't apply for increment, where it is legal
104 // (though inadvisable) to share shared_ptr references between
105 // threads, and have them all get copied at once. The argument
106 // also doesn't apply for __release_shared, because an outstanding
107 // weak_ptr::lock() could read / modify the shared count.
108 if (__libcpp_atomic_load(&__shared_weak_owners_
, _AO_Acquire
) == 0)
110 // no need to do this store, because we are about
111 // to destroy everything.
112 //__libcpp_atomic_store(&__shared_weak_owners_, -1, _AO_Release);
113 __on_zero_shared_weak();
115 else if (__libcpp_atomic_refcount_decrement(__shared_weak_owners_
) == -1)
116 __on_zero_shared_weak();
120 __shared_weak_count::lock() noexcept
122 long object_owners
= __libcpp_atomic_load(&__shared_owners_
);
123 while (object_owners
!= -1)
125 if (__libcpp_atomic_compare_exchange(&__shared_owners_
,
134 __shared_weak_count::__get_deleter(const type_info
&) const noexcept
139 #if !defined(_LIBCPP_HAS_NO_THREADS)
141 static constexpr std::size_t __sp_mut_count
= 32;
142 static constinit __libcpp_mutex_t mut_back
[__sp_mut_count
] =
144 _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
,
145 _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
,
146 _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
,
147 _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
,
148 _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
,
149 _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
,
150 _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
,
151 _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
, _LIBCPP_MUTEX_INITIALIZER
154 _LIBCPP_CONSTEXPR
__sp_mut::__sp_mut(void* p
) noexcept
160 __sp_mut::lock() noexcept
162 auto m
= static_cast<__libcpp_mutex_t
*>(__lx
);
163 __libcpp_mutex_lock(m
);
167 __sp_mut::unlock() noexcept
169 __libcpp_mutex_unlock(static_cast<__libcpp_mutex_t
*>(__lx
));
173 __get_sp_mut(const void* p
)
175 static constinit __sp_mut muts
[__sp_mut_count
] = {
176 &mut_back
[ 0], &mut_back
[ 1], &mut_back
[ 2], &mut_back
[ 3],
177 &mut_back
[ 4], &mut_back
[ 5], &mut_back
[ 6], &mut_back
[ 7],
178 &mut_back
[ 8], &mut_back
[ 9], &mut_back
[10], &mut_back
[11],
179 &mut_back
[12], &mut_back
[13], &mut_back
[14], &mut_back
[15],
180 &mut_back
[16], &mut_back
[17], &mut_back
[18], &mut_back
[19],
181 &mut_back
[20], &mut_back
[21], &mut_back
[22], &mut_back
[23],
182 &mut_back
[24], &mut_back
[25], &mut_back
[26], &mut_back
[27],
183 &mut_back
[28], &mut_back
[29], &mut_back
[30], &mut_back
[31]
185 return muts
[hash
<const void*>()(p
) & (__sp_mut_count
-1)];
188 #endif // !defined(_LIBCPP_HAS_NO_THREADS)
191 align(size_t alignment
, size_t size
, void*& ptr
, size_t& space
)
196 char* p1
= static_cast<char*>(ptr
);
197 char* p2
= reinterpret_cast<char*>(reinterpret_cast<size_t>(p1
+ (alignment
- 1)) & -alignment
);
198 size_t d
= static_cast<size_t>(p2
- p1
);
199 if (d
<= space
- size
)
209 _LIBCPP_END_NAMESPACE_STD