1 //===------------------------ memory_resource.cpp -------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "experimental/memory_resource"
11 
12 #ifndef _LIBCPP_HAS_NO_ATOMIC_HEADER
13 #include "atomic"
14 #elif !defined(_LIBCPP_HAS_NO_THREADS)
15 #include "mutex"
16 #endif
17 
18 _LIBCPP_BEGIN_NAMESPACE_LFTS_PMR
19 
20 // memory_resource
21 
22 //memory_resource::~memory_resource() {}
23 
24 // new_delete_resource()
25 
26 class _LIBCPP_TYPE_VIS_ONLY __new_delete_memory_resource_imp
27     : public memory_resource
28 {
29 public:
30     ~__new_delete_memory_resource_imp() = default;
31 
32 protected:
33     virtual void* do_allocate(size_t __size, size_t __align)
34         { return __allocate(__size); }
35 
36     virtual void do_deallocate(void * __p, size_t, size_t)
37         { __deallocate(__p); }
38 
39     virtual bool do_is_equal(memory_resource const & __other) const _NOEXCEPT
40         { return &__other == this; }
41 };
42 
43 // null_memory_resource()
44 
45 class _LIBCPP_TYPE_VIS_ONLY __null_memory_resource_imp
46     : public memory_resource
47 {
48 public:
49     ~__null_memory_resource_imp() = default;
50 
51 protected:
52     virtual void* do_allocate(size_t, size_t) {
53         __throw_bad_alloc();
54     }
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; }
58 };
59 
60 namespace {
61 
62 union ResourceInitHelper {
63   struct {
64     __new_delete_memory_resource_imp new_delete_res;
65     __null_memory_resource_imp       null_res;
66   } resources;
67   char dummy;
68   _LIBCPP_CONSTEXPR_AFTER_CXX11 ResourceInitHelper() : resources() {}
69   ~ResourceInitHelper() {}
70 };
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
74 _LIBCPP_SAFE_STATIC
75 #endif
76 ResourceInitHelper res_init  __attribute__((init_priority (101)));
77 
78 } // end namespace
79 
80 
81 memory_resource * new_delete_resource() _NOEXCEPT {
82     return &res_init.resources.new_delete_res;
83 }
84 
85 memory_resource * null_memory_resource() _NOEXCEPT {
86     return &res_init.resources.null_res;
87 }
88 
89 // default_memory_resource()
90 
91 static memory_resource *
92 __default_memory_resource(bool set = false, memory_resource * new_res = nullptr) _NOEXCEPT
93 {
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);
97     if (set) {
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);
102     }
103     else {
104         return _VSTD::atomic_load_explicit(
105             &__res, memory_order::memory_order_acquire);
106     }
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;
110     if (set) {
111         new_res = new_res ? new_res : new_delete_resource();
112         lock_guard<mutex> guard(res_lock);
113         memory_resource * old_res = res;
114         res = new_res;
115         return old_res;
116     } else {
117         lock_guard<mutex> guard(res_lock);
118         return res;
119     }
120 #else
121     _LIBCPP_SAFE_STATIC static memory_resource* res = &res_init.resources.new_delete_res;
122     if (set) {
123         new_res = new_res ? new_res : new_delete_resource();
124         memory_resource * old_res = res;
125         res = new_res;
126         return old_res;
127     } else {
128         return res;
129     }
130 #endif
131 }
132 
133 memory_resource * get_default_resource() _NOEXCEPT
134 {
135     return __default_memory_resource();
136 }
137 
138 memory_resource * set_default_resource(memory_resource * __new_res) _NOEXCEPT
139 {
140     return __default_memory_resource(true, __new_res);
141 }
142 
143 _LIBCPP_END_NAMESPACE_LFTS_PMR