libstdc++-v3/include/experimental/memory_resource

   1 // <experimental/memory_resource> -*- C++ -*-
   2
   3 // Copyright (C) 2015-2023 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 /** @file experimental/memory_resource
  26  *  This is a TS C++ Library header.
  27  *  @ingroup libfund-ts
  28  */
  29
  30 #ifndef _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE
  31 #define _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE 1
  32
  33 #pragma GCC system_header
  34
  35 #include <bits/requires_hosted.h> // experimental is currently omitted
  36
  37 #if __cplusplus >= 201402L
  38
  39 #include <memory>                       // align, uses_allocator, __uses_alloc
  40 #include <experimental/utility>         // pair, experimental::erased_type
  41 #include <tuple>                        // tuple, forward_as_tuple
  42 #include <atomic>                       // atomic
  43 #include <new>                          // placement new
  44 #include <cstddef>                      // max_align_t
  45 #include <bits/new_allocator.h>
  46 #include <debug/assertions.h>
  47
  48 /// @cond
  49 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  50 {
  51 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  52   template<typename _Tp> class malloc_allocator;
  53 _GLIBCXX_END_NAMESPACE_VERSION
  54 } // namespace __gnu_cxx
  55 /// @endcond
  56
  57 namespace std {
  58 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  59
  60 namespace experimental {
  61 inline namespace fundamentals_v2 {
  62 namespace pmr {
  63 #define __cpp_lib_experimental_memory_resources 201402L
  64
  65   // Standard memory resources
  66
  67   // 8.5 Class memory_resource
  68   class memory_resource;
  69
  70   // 8.6 Class template polymorphic_allocator
  71   template<typename _Tp>
  72     class polymorphic_allocator;
  73
  74   template<typename _Alloc, typename _Resource = memory_resource>
  75     class __resource_adaptor_imp;
  76
  77   // 8.7 Alias template resource_adaptor
  78   template<typename _Alloc>
  79     using resource_adaptor = __resource_adaptor_imp<
  80       typename allocator_traits<_Alloc>::template rebind_alloc<char>>;
  81
  82   // 8.8 Global memory resources
  83   memory_resource* new_delete_resource() noexcept;
  84   memory_resource* null_memory_resource() noexcept;
  85   memory_resource* get_default_resource() noexcept;
  86   memory_resource* set_default_resource(memory_resource* __r) noexcept;
  87
  88   // TODO 8.9 Pool resource classes
  89
  90   class memory_resource
  91   {
  92     static constexpr size_t _S_max_align = alignof(max_align_t);
  93
  94   public:
  95     memory_resource() = default;
  96     memory_resource(const memory_resource&) = default;
  97     virtual ~memory_resource() = default;
  98
  99     memory_resource& operator=(const memory_resource&) = default;
 100
 101     _GLIBCXX_NODISCARD void*
 102     allocate(size_t __bytes, size_t __alignment = _S_max_align)
 103     { return do_allocate(__bytes, __alignment); }
 104
 105     void
 106     deallocate(void* __p, size_t __bytes, size_t __alignment = _S_max_align)
 107     { return do_deallocate(__p, __bytes, __alignment); }
 108
 109     bool
 110     is_equal(const memory_resource& __other) const noexcept
 111     { return do_is_equal(__other); }
 112
 113   protected:
 114     virtual void*
 115     do_allocate(size_t __bytes, size_t __alignment) = 0;
 116
 117     virtual void
 118     do_deallocate(void* __p, size_t __bytes, size_t __alignment) = 0;
 119
 120     virtual bool
 121     do_is_equal(const memory_resource& __other) const noexcept = 0;
 122   };
 123
 124   inline bool
 125   operator==(const memory_resource& __a, const memory_resource& __b) noexcept
 126   { return &__a == &__b || __a.is_equal(__b); }
 127
 128   inline bool
 129   operator!=(const memory_resource& __a, const memory_resource& __b) noexcept
 130   { return !(__a == __b); }
 131
 132
 133   template<typename _Tp>
 134     class polymorphic_allocator
 135     {
 136     public:
 137       using value_type = _Tp;
 138
 139       polymorphic_allocator() noexcept
 140       : _M_resource(get_default_resource())
 141       { }
 142
 143       polymorphic_allocator(memory_resource* __r)
 144       : _M_resource(__r)
 145       { _GLIBCXX_DEBUG_ASSERT(__r); }
 146
 147       polymorphic_allocator(const polymorphic_allocator& __other) = default;
 148
 149       template <typename _Up>
 150         polymorphic_allocator(const polymorphic_allocator<_Up>&
 151                               __other) noexcept
 152         : _M_resource(__other.resource())
 153         { }
 154
 155       polymorphic_allocator&
 156         operator=(const polymorphic_allocator& __rhs) = default;
 157
 158       _GLIBCXX_NODISCARD _Tp* allocate(size_t __n)
 159       { return static_cast<_Tp*>(_M_resource->allocate(__n * sizeof(_Tp),
 160                                                        alignof(_Tp))); }
 161
 162       void
 163       deallocate(_Tp* __p, size_t __n)
 164       { _M_resource->deallocate(__p, __n * sizeof(_Tp), alignof(_Tp)); }
 165
 166       template <typename _Tp1, typename... _Args> //used here
 167         void
 168         construct(_Tp1* __p, _Args&&... __args)
 169         {
 170           std::__uses_allocator_construct(this->resource(), __p,
 171                                           std::forward<_Args>(__args)...);
 172         }
 173
 174       // Specializations for pair using piecewise construction
 175       template <typename _Tp1, typename _Tp2,
 176                typename... _Args1, typename... _Args2>
 177         void
 178         construct(pair<_Tp1, _Tp2>* __p, piecewise_construct_t,
 179                   tuple<_Args1...> __x, tuple<_Args2...> __y)
 180         {
 181           memory_resource* const __resource = this->resource();
 182           auto __x_use_tag =
 183             std::__use_alloc<_Tp1, memory_resource*, _Args1...>(__resource);
 184           auto __y_use_tag =
 185             std::__use_alloc<_Tp2, memory_resource*, _Args2...>(__resource);
 186
 187           ::new(__p) std::pair<_Tp1, _Tp2>(piecewise_construct,
 188                                            _M_construct_p(__x_use_tag, __x),
 189                                            _M_construct_p(__y_use_tag, __y));
 190         }
 191
 192       template <typename _Tp1, typename _Tp2>
 193         void
 194         construct(pair<_Tp1,_Tp2>* __p)
 195         { this->construct(__p, piecewise_construct, tuple<>(), tuple<>()); }
 196
 197       template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
 198         void
 199         construct(pair<_Tp1,_Tp2>* __p, _Up&& __x, _Vp&& __y)
 200         {
 201           this->construct(__p, piecewise_construct,
 202               std::forward_as_tuple(std::forward<_Up>(__x)),
 203               std::forward_as_tuple(std::forward<_Vp>(__y)));
 204         }
 205
 206       template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
 207         void
 208         construct(pair<_Tp1,_Tp2>* __p, const std::pair<_Up, _Vp>& __pr)
 209         {
 210           this->construct(__p, piecewise_construct,
 211               std::forward_as_tuple(__pr.first),
 212               std::forward_as_tuple(__pr.second));
 213         }
 214
 215       template <typename _Tp1, typename _Tp2, typename _Up, typename _Vp>
 216         void
 217         construct(pair<_Tp1,_Tp2>* __p, pair<_Up, _Vp>&& __pr)
 218         {
 219           this->construct(__p, piecewise_construct,
 220               std::forward_as_tuple(std::forward<_Up>(__pr.first)),
 221               std::forward_as_tuple(std::forward<_Vp>(__pr.second)));
 222         }
 223
 224       template <typename _Up>
 225         void
 226         destroy(_Up* __p)
 227         { __p->~_Up(); }
 228
 229       // Return a default-constructed allocator (no allocator propagation)
 230       polymorphic_allocator
 231       select_on_container_copy_construction() const
 232       { return polymorphic_allocator(); }
 233
 234       memory_resource* resource() const { return _M_resource; }
 235
 236     private:
 237       using __uses_alloc1_ = __uses_alloc1<memory_resource*>;
 238       using __uses_alloc2_ = __uses_alloc2<memory_resource*>;
 239
 240       template<typename _Tuple>
 241         _Tuple&&
 242         _M_construct_p(__uses_alloc0, _Tuple& __t)
 243         { return std::move(__t); }
 244
 245       template<typename... _Args>
 246         decltype(auto)
 247         _M_construct_p(__uses_alloc1_ __ua, tuple<_Args...>& __t)
 248         { return tuple_cat(make_tuple(allocator_arg, *(__ua._M_a)),
 249                            std::move(__t)); }
 250
 251       template<typename... _Args>
 252         decltype(auto)
 253         _M_construct_p(__uses_alloc2_ __ua, tuple<_Args...>& __t)
 254         { return tuple_cat(std::move(__t), make_tuple(*(__ua._M_a))); }
 255
 256       memory_resource* _M_resource;
 257     };
 258
 259   template <class _Tp1, class _Tp2>
 260     bool
 261     operator==(const polymorphic_allocator<_Tp1>& __a,
 262                const polymorphic_allocator<_Tp2>& __b) noexcept
 263     { return *__a.resource() == *__b.resource(); }
 264
 265   template <class _Tp1, class _Tp2>
 266     bool
 267     operator!=(const polymorphic_allocator<_Tp1>& __a,
 268                const polymorphic_allocator<_Tp2>& __b) noexcept
 269     { return !(__a == __b); }
 270
 271
 272   /// @cond undocumented
 273   class __resource_adaptor_common
 274   {
 275     template<typename, typename> friend class __resource_adaptor_imp;
 276
 277     struct _AlignMgr
 278     {
 279       _AlignMgr(size_t __nbytes, size_t __align)
 280       : _M_nbytes(__nbytes), _M_align(__align)
 281       { }
 282
 283       // Total size that needs to be allocated.
 284       size_t
 285       _M_alloc_size() const { return _M_buf_size() + _M_token_size(); }
 286
 287       void*
 288       _M_adjust(void* __ptr) const
 289       {
 290         const auto __orig_ptr = static_cast<char*>(__ptr);
 291         size_t __space = _M_buf_size();
 292         // Align the pointer within the buffer:
 293         std::align(_M_align, _M_nbytes, __ptr, __space);
 294         const auto __aligned_ptr = static_cast<char*>(__ptr);
 295         const auto __token_size = _M_token_size();
 296         // Store token immediately after the aligned block:
 297         char* const __end = __aligned_ptr + _M_nbytes;
 298         if (__token_size == 1)
 299           _S_write<unsigned char>(__end, __aligned_ptr - __orig_ptr);
 300         else if (__token_size == sizeof(short))
 301           _S_write<unsigned short>(__end, __aligned_ptr - __orig_ptr);
 302         else if (__token_size == sizeof(int) && sizeof(int) < sizeof(char*))
 303           _S_write<unsigned int>(__end, __aligned_ptr - __orig_ptr);
 304         else // (__token_size == sizeof(char*))
 305           // Just store the original pointer:
 306           _S_write<char*>(__end, __orig_ptr);
 307         return __aligned_ptr;
 308       }
 309
 310       char*
 311       _M_unadjust(char* __ptr) const
 312       {
 313         const char* const __end = __ptr + _M_nbytes;
 314         char* __orig_ptr;
 315         const auto __token_size = _M_token_size();
 316         // Read the token and restore the original pointer:
 317         if (__token_size == 1)
 318           __orig_ptr = __ptr - _S_read<unsigned char>(__end);
 319         else if (__token_size == sizeof(short))
 320           __orig_ptr = __ptr - _S_read<unsigned short>(__end);
 321         else if (__token_size == sizeof(int)
 322             && sizeof(int) < sizeof(char*))
 323           __orig_ptr = __ptr - _S_read<unsigned int>(__end);
 324         else // (__token_size == sizeof(char*))
 325           __orig_ptr = _S_read<char*>(__end);
 326         // The adjustment is always less than the requested alignment,
 327         // so if that isn't true now then either the wrong size was passed
 328         // to deallocate or the token was overwritten by a buffer overflow:
 329         __glibcxx_assert(static_cast<size_t>(__ptr - __orig_ptr) < _M_align);
 330         return __orig_ptr;
 331       }
 332
 333     private:
 334       size_t _M_nbytes;
 335       size_t _M_align;
 336
 337       // Number of bytes needed to fit block of given size and alignment.
 338       size_t
 339       _M_buf_size() const { return _M_nbytes + _M_align - 1; }
 340
 341       // Number of additional bytes needed to write the token.
 342       int
 343       _M_token_size() const
 344       {
 345         if (_M_align <= (1ul << __CHAR_BIT__))
 346           return 1;
 347         if (_M_align <= (1ul << (sizeof(short) * __CHAR_BIT__)))
 348           return sizeof(short);
 349         if (_M_align <= (1ull << (sizeof(int) * __CHAR_BIT__)))
 350           return sizeof(int);
 351         return sizeof(char*);
 352       }
 353
 354       template<typename _Tp>
 355         static void
 356         _S_write(void* __to, _Tp __val)
 357         { __builtin_memcpy(__to, &__val, sizeof(_Tp)); }
 358
 359       template<typename _Tp>
 360         static _Tp
 361         _S_read(const void* __from)
 362         {
 363           _Tp __val;
 364           __builtin_memcpy(&__val, __from, sizeof(_Tp));
 365           return __val;
 366         }
 367     };
 368   };
 369   /// @endcond
 370
 371   // 8.7.1 __resource_adaptor_imp
 372   template<typename _Alloc, typename _Resource>
 373     class __resource_adaptor_imp
 374     : public _Resource, private __resource_adaptor_common
 375     {
 376       using memory_resource = _Resource;
 377
 378       static_assert(is_same<char,
 379           typename allocator_traits<_Alloc>::value_type>::value,
 380           "Allocator's value_type is char");
 381       static_assert(is_same<char*,
 382           typename allocator_traits<_Alloc>::pointer>::value,
 383           "Allocator's pointer type is value_type*");
 384       static_assert(is_same<const char*,
 385           typename allocator_traits<_Alloc>::const_pointer>::value,
 386           "Allocator's const_pointer type is value_type const*");
 387       static_assert(is_same<void*,
 388           typename allocator_traits<_Alloc>::void_pointer>::value,
 389           "Allocator's void_pointer type is void*");
 390       static_assert(is_same<const void*,
 391           typename allocator_traits<_Alloc>::const_void_pointer>::value,
 392           "Allocator's const_void_pointer type is void const*");
 393
 394     public:
 395       using allocator_type = _Alloc;
 396
 397       __resource_adaptor_imp() = default;
 398       __resource_adaptor_imp(const __resource_adaptor_imp&) = default;
 399       __resource_adaptor_imp(__resource_adaptor_imp&&) = default;
 400
 401       explicit __resource_adaptor_imp(const _Alloc& __a2)
 402       : _M_alloc(__a2)
 403       { }
 404
 405       explicit __resource_adaptor_imp(_Alloc&& __a2)
 406       : _M_alloc(std::move(__a2))
 407       { }
 408
 409       __resource_adaptor_imp&
 410       operator=(const __resource_adaptor_imp&) = default;
 411
 412       allocator_type get_allocator() const noexcept { return _M_alloc; }
 413
 414     protected:
 415 #if (defined __sun__ || defined __VXWORKS__) && defined __i386__
 416 // Cannot use max_align_t on 32-bit Solaris x86, see PR libstdc++/77691
 417 # define _GLIBCXX_MAX_ALIGN_MATCHES_MALLOC 0
 418 #elif defined __hpux__ && defined __hppa__ && defined __LP64__
 419 // Ignore inconsistent long double and malloc alignment (libstdc++/77691)
 420 # define _GLIBCXX_MAX_ALIGN_MATCHES_MALLOC 0
 421 #else
 422 # define _GLIBCXX_MAX_ALIGN_MATCHES_MALLOC 1
 423 #endif
 424
 425       virtual void*
 426       do_allocate(size_t __bytes, size_t __alignment) override
 427       {
 428 #if _GLIBCXX_MAX_ALIGN_MATCHES_MALLOC
 429         if (__alignment == alignof(max_align_t))
 430           return _M_allocate<alignof(max_align_t)>(__bytes);
 431 #endif
 432         switch (__alignment)
 433           {
 434           case 1:
 435             return _M_alloc.allocate(__bytes);
 436           case 2:
 437             return _M_allocate<2>(__bytes);
 438           case 4:
 439             return _M_allocate<4>(__bytes);
 440           case 8:
 441             return _M_allocate<8>(__bytes);
 442           }
 443         const _AlignMgr __mgr(__bytes, __alignment);
 444         // Assume _M_alloc returns 1-byte aligned memory, so allocate enough
 445         // space to fit a block of the right size and alignment, plus some
 446         // extra bytes to store a token for retrieving the original pointer.
 447         return __mgr._M_adjust(_M_alloc.allocate(__mgr._M_alloc_size()));
 448       }
 449
 450       virtual void
 451       do_deallocate(void* __ptr, size_t __bytes, size_t __alignment) noexcept
 452       override
 453       {
 454 #if _GLIBCXX_MAX_ALIGN_MATCHES_MALLOC
 455         if (__alignment == alignof(max_align_t))
 456           return (void) _M_deallocate<alignof(max_align_t)>(__ptr, __bytes);
 457 #endif
 458         switch (__alignment)
 459           {
 460           case 1:
 461             return (void) _M_alloc.deallocate((char*)__ptr, __bytes);
 462           case 2:
 463             return (void) _M_deallocate<2>(__ptr, __bytes);
 464           case 4:
 465             return (void) _M_deallocate<4>(__ptr, __bytes);
 466           case 8:
 467             return (void) _M_deallocate<8>(__ptr, __bytes);
 468           }
 469         const _AlignMgr __mgr(__bytes, __alignment);
 470         // Use the stored token to retrieve the original pointer.
 471         _M_alloc.deallocate(__mgr._M_unadjust((char*)__ptr),
 472             __mgr._M_alloc_size());
 473       }
 474
 475       virtual bool
 476       do_is_equal(const memory_resource& __other) const noexcept override
 477       {
 478 #if __cpp_rtti
 479         if (auto __p = dynamic_cast<const __resource_adaptor_imp*>(&__other))
 480           return _M_alloc == __p->_M_alloc;
 481 #else
 482         if (this == &__other) // Need RTTI to do better than this.
 483           return true;
 484 #endif
 485         return false;
 486       }
 487
 488     private:
 489       template<size_t _Num>
 490         struct _Aligned_type { alignas(_Num) char __c[_Num]; };
 491
 492       // Rebind the allocator to the specified type and use it to allocate.
 493       template<size_t _Num, typename _Tp = _Aligned_type<_Num>>
 494         void*
 495         _M_allocate(size_t __bytes)
 496         {
 497           typename allocator_traits<_Alloc>::template
 498             rebind_alloc<_Tp> __a2(_M_alloc);
 499           const size_t __n = (__bytes + _Num - 1) / _Num;
 500           return __a2.allocate(__n);
 501         }
 502
 503       // Rebind the allocator to the specified type and use it to deallocate.
 504       template<size_t _Num, typename _Tp = _Aligned_type<_Num>>
 505         void
 506         _M_deallocate(void* __ptr, size_t __bytes) noexcept
 507         {
 508           typename allocator_traits<_Alloc>::template
 509             rebind_alloc<_Tp> __a2(_M_alloc);
 510           const size_t __n = (__bytes + _Num - 1) / _Num;
 511           __a2.deallocate((_Tp*)__ptr, __n);
 512         }
 513
 514       _Alloc _M_alloc{};
 515     };
 516
 517   // Global memory resources
 518
 519   inline memory_resource*
 520   new_delete_resource() noexcept
 521   {
 522     using type = resource_adaptor<std::__new_allocator<char>>;
 523     alignas(type) static unsigned char __buf[sizeof(type)];
 524     static type* __r = new(__buf) type;
 525     return __r;
 526   }
 527
 528   inline memory_resource*
 529   null_memory_resource() noexcept
 530   {
 531     class type final : public memory_resource
 532     {
 533       void*
 534       do_allocate(size_t, size_t) override
 535       { std::__throw_bad_alloc(); }
 536
 537       void
 538       do_deallocate(void*, size_t, size_t) noexcept override
 539       { }
 540
 541       bool
 542       do_is_equal(const memory_resource& __other) const noexcept override
 543       { return this == &__other; }
 544     };
 545
 546     alignas(type) static unsigned char __buf[sizeof(type)];
 547     static type* __r = new(__buf) type;
 548     return __r;
 549   }
 550
 551   // The default memory resource
 552
 553   /// @cond undocumented
 554   inline std::atomic<memory_resource*>&
 555   __get_default_resource()
 556   {
 557     using type = atomic<memory_resource*>;
 558     alignas(type) static unsigned char __buf[sizeof(type)];
 559     static type* __r = new(__buf) type(new_delete_resource());
 560     return *__r;
 561   }
 562   /// @endcond
 563
 564   /// Get the current default resource.
 565   inline memory_resource*
 566   get_default_resource() noexcept
 567   { return __get_default_resource().load(); }
 568
 569   /// Change the default resource and return the previous one.
 570   inline memory_resource*
 571   set_default_resource(memory_resource* __r) noexcept
 572   {
 573     if (__r == nullptr)
 574       __r = new_delete_resource();
 575     return __get_default_resource().exchange(__r);
 576   }
 577
 578 } // namespace pmr
 579 } // namespace fundamentals_v2
 580 } // namespace experimental
 581
 582 _GLIBCXX_END_NAMESPACE_VERSION
 583 } // namespace std
 584 #endif // C++14
 585 #endif // _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE