1//===------------------------ memory_resource.cpp -------------------------===//
2//
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
6//
7//===----------------------------------------------------------------------===//
8
9#include "experimental/memory_resource"
10
11#ifndef _LIBCPP_HAS_NO_ATOMIC_HEADER
12#include "atomic"
13#elif !defined(_LIBCPP_HAS_NO_THREADS)
14#include "mutex"
15#if defined(__ELF__) && defined(_LIBCPP_LINK_PTHREAD_LIB)
16#pragma comment(lib, "pthread")
17#endif
18#endif
19
20_LIBCPP_BEGIN_NAMESPACE_LFTS_PMR
21
22// memory_resource
23
24//memory_resource::~memory_resource() {}
25
26// new_delete_resource()
27
28class _LIBCPP_TYPE_VIS __new_delete_memory_resource_imp
29 : public memory_resource
30{
31 void *do_allocate(size_t size, size_t align) override {
32#ifdef _LIBCPP_HAS_NO_ALIGNED_ALLOCATION
33 if (__is_overaligned_for_new(align))
34 __throw_bad_alloc();
35#endif
36 return _VSTD::__libcpp_allocate(size, align);
37 }
38
39 void do_deallocate(void *p, size_t n, size_t align) override {
40 _VSTD::__libcpp_deallocate(p, n, align);
41 }
42
43 bool do_is_equal(memory_resource const & other) const _NOEXCEPT override
44 { return &other == this; }
45
46public:
47 ~__new_delete_memory_resource_imp() override = default;
48};
49
50// null_memory_resource()
51
52class _LIBCPP_TYPE_VIS __null_memory_resource_imp
53 : public memory_resource
54{
55public:
56 ~__null_memory_resource_imp() = default;
57
58protected:
59 virtual void* do_allocate(size_t, size_t) {
60 __throw_bad_alloc();
61 }
62 virtual void do_deallocate(void *, size_t, size_t) {}
63 virtual bool do_is_equal(memory_resource const & __other) const _NOEXCEPT
64 { return &__other == this; }
65};
66
67namespace {
68
69union ResourceInitHelper {
70 struct {
71 __new_delete_memory_resource_imp new_delete_res;
72 __null_memory_resource_imp null_res;
73 } resources;
74 char dummy;
75 _LIBCPP_CONSTEXPR_AFTER_CXX11 ResourceInitHelper() : resources() {}
76 ~ResourceInitHelper() {}
77};
78
79// Detect if the init_priority attribute is supported.
80#if (defined(_LIBCPP_COMPILER_GCC) && defined(__APPLE__)) \
81 || defined(_LIBCPP_COMPILER_MSVC)
82// GCC on Apple doesn't support the init priority attribute,
83// and MSVC doesn't support any GCC attributes.
84# define _LIBCPP_INIT_PRIORITY_MAX
85#else
86# define _LIBCPP_INIT_PRIORITY_MAX __attribute__((init_priority(101)))
87#endif
88
89// When compiled in C++14 this initialization should be a constant expression.
90// Only in C++11 is "init_priority" needed to ensure initialization order.
91#if _LIBCPP_STD_VER > 11
92_LIBCPP_SAFE_STATIC
93#endif
94ResourceInitHelper res_init _LIBCPP_INIT_PRIORITY_MAX;
95
96} // end namespace
97
98
99memory_resource * new_delete_resource() _NOEXCEPT {
100 return &res_init.resources.new_delete_res;
101}
102
103memory_resource * null_memory_resource() _NOEXCEPT {
104 return &res_init.resources.null_res;
105}
106
107// default_memory_resource()
108
109static memory_resource *
110__default_memory_resource(bool set = false, memory_resource * new_res = nullptr) _NOEXCEPT
111{
112#ifndef _LIBCPP_HAS_NO_ATOMIC_HEADER
113 _LIBCPP_SAFE_STATIC static atomic<memory_resource*> __res =
114 ATOMIC_VAR_INIT(&res_init.resources.new_delete_res);
115 if (set) {
116 new_res = new_res ? new_res : new_delete_resource();
117 // TODO: Can a weaker ordering be used?
118 return _VSTD::atomic_exchange_explicit(
119 &__res, new_res, memory_order_acq_rel);
120 }
121 else {
122 return _VSTD::atomic_load_explicit(
123 &__res, memory_order_acquire);
124 }
125#elif !defined(_LIBCPP_HAS_NO_THREADS)
126 _LIBCPP_SAFE_STATIC static memory_resource * res = &res_init.resources.new_delete_res;
127 static mutex res_lock;
128 if (set) {
129 new_res = new_res ? new_res : new_delete_resource();
130 lock_guard<mutex> guard(res_lock);
131 memory_resource * old_res = res;
132 res = new_res;
133 return old_res;
134 } else {
135 lock_guard<mutex> guard(res_lock);
136 return res;
137 }
138#else
139 _LIBCPP_SAFE_STATIC static memory_resource* res = &res_init.resources.new_delete_res;
140 if (set) {
141 new_res = new_res ? new_res : new_delete_resource();
142 memory_resource * old_res = res;
143 res = new_res;
144 return old_res;
145 } else {
146 return res;
147 }
148#endif
149}
150
151memory_resource * get_default_resource() _NOEXCEPT
152{
153 return __default_memory_resource();
154}
155
156memory_resource * set_default_resource(memory_resource * __new_res) _NOEXCEPT
157{
158 return __default_memory_resource(true, __new_res);
159}
160
161_LIBCPP_END_NAMESPACE_LFTS_PMR
162