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 
28 class _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 
46 public:
47     ~__new_delete_memory_resource_imp() override = default;
48 };
49 
50 // null_memory_resource()
51 
52 class _LIBCPP_TYPE_VIS __null_memory_resource_imp
53     : public memory_resource
54 {
55 public:
56     ~__null_memory_resource_imp() = default;
57 
58 protected:
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 
67 namespace {
68 
69 union 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 _LIBCPP_SAFE_STATIC ResourceInitHelper res_init _LIBCPP_INIT_PRIORITY_MAX;
80 
81 } // end namespace
82 
83 
84 memory_resource * new_delete_resource() noexcept {
85     return &res_init.resources.new_delete_res;
86 }
87 
88 memory_resource * null_memory_resource() noexcept {
89     return &res_init.resources.null_res;
90 }
91 
92 // default_memory_resource()
93 
94 static memory_resource *
95 __default_memory_resource(bool set = false, memory_resource * new_res = nullptr) noexcept
96 {
97 #ifndef _LIBCPP_HAS_NO_ATOMIC_HEADER
98     _LIBCPP_SAFE_STATIC static atomic<memory_resource*> __res =
99         ATOMIC_VAR_INIT(&res_init.resources.new_delete_res);
100     if (set) {
101         new_res = new_res ? new_res : new_delete_resource();
102         // TODO: Can a weaker ordering be used?
103         return _VSTD::atomic_exchange_explicit(
104             &__res, new_res, memory_order_acq_rel);
105     }
106     else {
107         return _VSTD::atomic_load_explicit(
108             &__res, memory_order_acquire);
109     }
110 #elif !defined(_LIBCPP_HAS_NO_THREADS)
111     _LIBCPP_SAFE_STATIC static memory_resource * res = &res_init.resources.new_delete_res;
112     static mutex res_lock;
113     if (set) {
114         new_res = new_res ? new_res : new_delete_resource();
115         lock_guard<mutex> guard(res_lock);
116         memory_resource * old_res = res;
117         res = new_res;
118         return old_res;
119     } else {
120         lock_guard<mutex> guard(res_lock);
121         return res;
122     }
123 #else
124     _LIBCPP_SAFE_STATIC static memory_resource* res = &res_init.resources.new_delete_res;
125     if (set) {
126         new_res = new_res ? new_res : new_delete_resource();
127         memory_resource * old_res = res;
128         res = new_res;
129         return old_res;
130     } else {
131         return res;
132     }
133 #endif
134 }
135 
136 memory_resource * get_default_resource() noexcept
137 {
138     return __default_memory_resource();
139 }
140 
141 memory_resource * set_default_resource(memory_resource * __new_res) noexcept
142 {
143     return __default_memory_resource(true, __new_res);
144 }
145 
146 _LIBCPP_END_NAMESPACE_LFTS_PMR
147