1 //===------------------------ memory_resource.cpp -------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "experimental/memory_resource"
12 #ifndef _LIBCPP_HAS_NO_ATOMIC_HEADER
14 #elif !defined(_LIBCPP_HAS_NO_THREADS)
18 _LIBCPP_BEGIN_NAMESPACE_LFTS_PMR
22 //memory_resource::~memory_resource() {}
24 // new_delete_resource()
26 class _LIBCPP_TYPE_VIS __new_delete_memory_resource_imp
27 : public memory_resource
30 ~__new_delete_memory_resource_imp() = default;
33 virtual void* do_allocate(size_t __size, size_t __align)
34 { return __allocate(__size); }
36 virtual void do_deallocate(void * __p, size_t, size_t)
37 { _VSTD::__libcpp_deallocate(__p); }
39 virtual bool do_is_equal(memory_resource const & __other) const _NOEXCEPT
40 { return &__other == this; }
43 // null_memory_resource()
45 class _LIBCPP_TYPE_VIS __null_memory_resource_imp
46 : public memory_resource
49 ~__null_memory_resource_imp() = default;
52 virtual void* do_allocate(size_t, size_t) {
55 virtual void do_deallocate(void *, size_t, size_t) {}
56 virtual bool do_is_equal(memory_resource const & __other) const _NOEXCEPT
57 { return &__other == this; }
62 union ResourceInitHelper {
64 __new_delete_memory_resource_imp new_delete_res;
65 __null_memory_resource_imp null_res;
68 _LIBCPP_CONSTEXPR_AFTER_CXX11 ResourceInitHelper() : resources() {}
69 ~ResourceInitHelper() {}
71 // When compiled in C++14 this initialization should be a constant expression.
72 // Only in C++11 is "init_priority" needed to ensure initialization order.
73 #if _LIBCPP_STD_VER > 11
76 ResourceInitHelper res_init __attribute__((init_priority (101)));
81 memory_resource * new_delete_resource() _NOEXCEPT {
82 return &res_init.resources.new_delete_res;
85 memory_resource * null_memory_resource() _NOEXCEPT {
86 return &res_init.resources.null_res;
89 // default_memory_resource()
91 static memory_resource *
92 __default_memory_resource(bool set = false, memory_resource * new_res = nullptr) _NOEXCEPT
94 #ifndef _LIBCPP_HAS_NO_ATOMIC_HEADER
95 _LIBCPP_SAFE_STATIC static atomic<memory_resource*> __res =
96 ATOMIC_VAR_INIT(&res_init.resources.new_delete_res);
98 new_res = new_res ? new_res : new_delete_resource();
99 // TODO: Can a weaker ordering be used?
100 return _VSTD::atomic_exchange_explicit(
101 &__res, new_res, memory_order::memory_order_acq_rel);
104 return _VSTD::atomic_load_explicit(
105 &__res, memory_order::memory_order_acquire);
107 #elif !defined(_LIBCPP_HAS_NO_THREADS)
108 _LIBCPP_SAFE_STATIC static memory_resource * res = &res_init.resources.new_delete_res;
109 static mutex res_lock;
111 new_res = new_res ? new_res : new_delete_resource();
112 lock_guard<mutex> guard(res_lock);
113 memory_resource * old_res = res;
117 lock_guard<mutex> guard(res_lock);
121 _LIBCPP_SAFE_STATIC static memory_resource* res = &res_init.resources.new_delete_res;
123 new_res = new_res ? new_res : new_delete_resource();
124 memory_resource * old_res = res;
133 memory_resource * get_default_resource() _NOEXCEPT
135 return __default_memory_resource();
138 memory_resource * set_default_resource(memory_resource * __new_res) _NOEXCEPT
140 return __default_memory_resource(true, __new_res);
143 _LIBCPP_END_NAMESPACE_LFTS_PMR