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 _VSTD::__libcpp_allocate(__size, __align); /* FIXME */}
36 virtual void do_deallocate(void* __p, size_t __n, size_t __align) {
37 _VSTD::__libcpp_deallocate(__p, __n, __align); /* FIXME */
40 virtual bool do_is_equal(memory_resource const & __other) const _NOEXCEPT
41 { return &__other == this; }
44 // null_memory_resource()
46 class _LIBCPP_TYPE_VIS __null_memory_resource_imp
47 : public memory_resource
50 ~__null_memory_resource_imp() = default;
53 virtual void* do_allocate(size_t, size_t) {
56 virtual void do_deallocate(void *, size_t, size_t) {}
57 virtual bool do_is_equal(memory_resource const & __other) const _NOEXCEPT
58 { return &__other == this; }
63 union ResourceInitHelper {
65 __new_delete_memory_resource_imp new_delete_res;
66 __null_memory_resource_imp null_res;
69 _LIBCPP_CONSTEXPR_AFTER_CXX11 ResourceInitHelper() : resources() {}
70 ~ResourceInitHelper() {}
73 // Detect if the init_priority attribute is supported.
74 #if (defined(_LIBCPP_COMPILER_GCC) && defined(__APPLE__)) \
75 || defined(_LIBCPP_COMPILER_MSVC)
76 // GCC on Apple doesn't support the init priority attribute,
77 // and MSVC doesn't support any GCC attributes.
78 # define _LIBCPP_INIT_PRIORITY_MAX
80 # define _LIBCPP_INIT_PRIORITY_MAX __attribute__((init_priority(101)))
83 // When compiled in C++14 this initialization should be a constant expression.
84 // Only in C++11 is "init_priority" needed to ensure initialization order.
85 #if _LIBCPP_STD_VER > 11
88 ResourceInitHelper res_init _LIBCPP_INIT_PRIORITY_MAX;
93 memory_resource * new_delete_resource() _NOEXCEPT {
94 return &res_init.resources.new_delete_res;
97 memory_resource * null_memory_resource() _NOEXCEPT {
98 return &res_init.resources.null_res;
101 // default_memory_resource()
103 static memory_resource *
104 __default_memory_resource(bool set = false, memory_resource * new_res = nullptr) _NOEXCEPT
106 #ifndef _LIBCPP_HAS_NO_ATOMIC_HEADER
107 _LIBCPP_SAFE_STATIC static atomic<memory_resource*> __res =
108 ATOMIC_VAR_INIT(&res_init.resources.new_delete_res);
110 new_res = new_res ? new_res : new_delete_resource();
111 // TODO: Can a weaker ordering be used?
112 return _VSTD::atomic_exchange_explicit(
113 &__res, new_res, memory_order::memory_order_acq_rel);
116 return _VSTD::atomic_load_explicit(
117 &__res, memory_order::memory_order_acquire);
119 #elif !defined(_LIBCPP_HAS_NO_THREADS)
120 _LIBCPP_SAFE_STATIC static memory_resource * res = &res_init.resources.new_delete_res;
121 static mutex res_lock;
123 new_res = new_res ? new_res : new_delete_resource();
124 lock_guard<mutex> guard(res_lock);
125 memory_resource * old_res = res;
129 lock_guard<mutex> guard(res_lock);
133 _LIBCPP_SAFE_STATIC static memory_resource* res = &res_init.resources.new_delete_res;
135 new_res = new_res ? new_res : new_delete_resource();
136 memory_resource * old_res = res;
145 memory_resource * get_default_resource() _NOEXCEPT
147 return __default_memory_resource();
150 memory_resource * set_default_resource(memory_resource * __new_res) _NOEXCEPT
152 return __default_memory_resource(true, __new_res);
155 _LIBCPP_END_NAMESPACE_LFTS_PMR