libstdc++-v3/testsuite/util/testsuite_allocator.h

   1 // -*- C++ -*-
   2 // Testing allocator for the C++ library testsuite.
   3 //
   4 // Copyright (C) 2002-2025 Free Software Foundation, Inc.
   5 //
   6 // This file is part of the GNU ISO C++ Library.  This library is free
   7 // software; you can redistribute it and/or modify it under the
   8 // terms of the GNU General Public License as published by the
   9 // Free Software Foundation; either version 3, or (at your option)
  10 // any later version.
  11 //
  12 // This library is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16 //
  17 // You should have received a copy of the GNU General Public License along
  18 // with this library; see the file COPYING3.  If not see
  19 // <http://www.gnu.org/licenses/>.
  20 //
  21
  22 // This file provides an test instrumentation allocator that can be
  23 // used to verify allocation functionality of standard library
  24 // containers.  2002.11.25 smw
  25
  26 #ifndef _GLIBCXX_TESTSUITE_ALLOCATOR_H
  27 #define _GLIBCXX_TESTSUITE_ALLOCATOR_H
  28
  29 #include <bits/move.h>
  30 #include <ext/pointer.h>
  31 #include <ext/alloc_traits.h>
  32 #include <testsuite_hooks.h>
  33 #if __cplusplus >= 201703L
  34 # include <memory_resource>
  35 # include <new>
  36 #endif
  37
  38 #if __cplusplus >= 201103L
  39 # include <unordered_map>
  40 namespace unord = std;
  41 #else
  42 # include <tr1/unordered_map>
  43 namespace unord = std::tr1;
  44 #endif
  45
  46 namespace __gnu_test
  47 {
  48   // A common API for calling max_size() on an allocator in any -std mode.
  49   template<typename A>
  50     typename A::size_type
  51     max_size(const A& a)
  52     {
  53 #if __cplusplus >= 201103L
  54       return std::allocator_traits<A>::max_size(a);
  55 #else
  56       return a.max_size();
  57 #endif
  58     }
  59
  60   class tracker_allocator_counter
  61   {
  62   public:
  63     typedef std::size_t    size_type;
  64
  65     static void
  66     allocate(size_type blocksize)
  67     { allocationCount_ += blocksize; }
  68
  69     static void
  70     construct() { ++constructCount_; }
  71
  72     static void
  73     destroy() { ++destructCount_; }
  74
  75     static void
  76     deallocate(size_type blocksize)
  77     { deallocationCount_ += blocksize; }
  78
  79     static size_type
  80     get_allocation_count() { return allocationCount_; }
  81
  82     static size_type
  83     get_deallocation_count() { return deallocationCount_; }
  84
  85     static int
  86     get_construct_count() { return constructCount_; }
  87
  88     static int
  89     get_destruct_count() { return destructCount_; }
  90
  91     static void
  92     reset()
  93     {
  94       allocationCount_ = 0;
  95       deallocationCount_ = 0;
  96       constructCount_ = 0;
  97       destructCount_ = 0;
  98     }
  99
 100  private:
 101     static size_type  allocationCount_;
 102     static size_type  deallocationCount_;
 103     static int        constructCount_;
 104     static int        destructCount_;
 105   };
 106
 107   // Helper to detect inconsistency between type used to instantiate an
 108   // allocator and the underlying allocator value_type.
 109   template<typename T, typename Alloc,
 110            typename = typename Alloc::value_type>
 111     struct check_consistent_alloc_value_type;
 112
 113   template<typename T, typename Alloc>
 114     struct check_consistent_alloc_value_type<T, Alloc, T>
 115     { typedef T value_type; };
 116
 117   // An allocator facade that intercepts allocate/deallocate/construct/destroy
 118   // calls and track them through the tracker_allocator_counter class. This
 119   // class is templated on the target object type, but tracker isn't.
 120   template<typename T, typename Alloc = std::allocator<T> >
 121     class tracker_allocator : public Alloc
 122     {
 123     private:
 124       typedef tracker_allocator_counter counter_type;
 125
 126       typedef __gnu_cxx::__alloc_traits<Alloc> AllocTraits;
 127
 128     public:
 129       typedef typename
 130       check_consistent_alloc_value_type<T, Alloc>::value_type value_type;
 131       typedef typename AllocTraits::pointer pointer;
 132       typedef typename AllocTraits::size_type size_type;
 133
 134       template<class U>
 135         struct rebind
 136         {
 137           typedef tracker_allocator<U,
 138                 typename AllocTraits::template rebind<U>::other> other;
 139         };
 140
 141 #if __cplusplus >= 201103L
 142       tracker_allocator() = default;
 143       tracker_allocator(const tracker_allocator&) = default;
 144       tracker_allocator(tracker_allocator&&) = default;
 145       tracker_allocator& operator=(const tracker_allocator&) = default;
 146       tracker_allocator& operator=(tracker_allocator&&) = default;
 147
 148       // Perfect forwarding constructor.
 149       template<typename... _Args>
 150         tracker_allocator(_Args&&... __args)
 151           : Alloc(std::forward<_Args>(__args)...)
 152         { }
 153 #else
 154       tracker_allocator()
 155       { }
 156
 157       tracker_allocator(const tracker_allocator& a) : Alloc(a)
 158       { }
 159
 160       ~tracker_allocator()
 161       { }
 162 #endif
 163
 164       template<class U>
 165         tracker_allocator(const tracker_allocator<U,
 166           typename AllocTraits::template rebind<U>::other>& alloc)
 167             _GLIBCXX_USE_NOEXCEPT
 168           : Alloc(alloc)
 169         { }
 170
 171       pointer
 172       allocate(size_type n, const void* = 0)
 173       {
 174         pointer p = AllocTraits::allocate(*this, n);
 175         counter_type::allocate(n * sizeof(T));
 176         return p;
 177       }
 178
 179 #if __cplusplus >= 201103L
 180       template<typename U, typename... Args>
 181         void
 182         construct(U* p, Args&&... args)
 183         {
 184           AllocTraits::construct(*this, p, std::forward<Args>(args)...);
 185           counter_type::construct();
 186         }
 187
 188       template<typename U>
 189         void
 190         destroy(U* p)
 191         {
 192           AllocTraits::destroy(*this, p);
 193           counter_type::destroy();
 194         }
 195 #else
 196       void
 197       construct(pointer p, const T& value)
 198       {
 199         AllocTraits::construct(*this, p, value);
 200         counter_type::construct();
 201       }
 202
 203       void
 204       destroy(pointer p)
 205       {
 206         AllocTraits::destroy(*this, p);
 207         counter_type::destroy();
 208       }
 209 #endif
 210
 211       void
 212       deallocate(pointer p, size_type num)
 213       {
 214         counter_type::deallocate(num * sizeof(T));
 215         AllocTraits::deallocate(*this, p, num);
 216       }
 217
 218       // Implement swap for underlying allocators that might need it.
 219       friend inline void
 220       swap(tracker_allocator& a, tracker_allocator& b)
 221       {
 222         using std::swap;
 223
 224         Alloc& aa = a;
 225         Alloc& ab = b;
 226         swap(aa, ab);
 227       }
 228     };
 229
 230   template<class T1, class Alloc1, class T2, class Alloc2>
 231     bool
 232     operator==(const tracker_allocator<T1, Alloc1>& lhs,
 233                const tracker_allocator<T2, Alloc2>& rhs) throw()
 234     {
 235       const Alloc1& alloc1 = lhs;
 236       const Alloc2& alloc2 = rhs;
 237       return alloc1 == alloc2;
 238     }
 239
 240   template<class T1, class Alloc1, class T2, class Alloc2>
 241     bool
 242     operator!=(const tracker_allocator<T1, Alloc1>& lhs,
 243                const tracker_allocator<T2, Alloc2>& rhs) throw()
 244     { return !(lhs == rhs); }
 245
 246   bool
 247   check_construct_destroy(const char* tag, int expected_c, int expected_d);
 248
 249   template<typename Alloc>
 250     bool
 251     check_deallocate_null()
 252     {
 253       // Let's not core here...
 254       Alloc a;
 255       a.deallocate(0, 1);
 256       a.deallocate(0, 10);
 257       return true;
 258     }
 259
 260 #if __cpp_exceptions
 261   template<typename Alloc>
 262     bool
 263     check_allocate_max_size()
 264     {
 265       Alloc a;
 266       try
 267         {
 268           (void) a.allocate(__gnu_test::max_size(a) + 1);
 269         }
 270       catch(std::bad_alloc&)
 271         {
 272           return true;
 273         }
 274       catch(...)
 275         {
 276           throw;
 277         }
 278       throw;
 279     }
 280 #endif
 281
 282   // A simple allocator which can be constructed endowed of a given
 283   // "personality" (an integer), queried in operator== to simulate the
 284   // behavior of realworld "unequal" allocators (i.e., not exploiting
 285   // the provision in 20.1.5/4, first bullet).  A global unordered_map,
 286   // filled at allocation time with (pointer, personality) pairs, is
 287   // then consulted to enforce the requirements in Table 32 about
 288   // deallocation vs allocator equality.  Note that this allocator is
 289   // swappable, not copy assignable, consistently with Option 3 of DR 431
 290   // (see N1599).
 291   struct uneq_allocator_base
 292   {
 293     typedef unord::unordered_map<void*, int>   map_type;
 294
 295     // Avoid static initialization troubles and/or bad interactions
 296     // with tests linking testsuite_allocator.o and playing globally
 297     // with operator new/delete.
 298     static map_type&
 299     get_map()
 300     {
 301       static map_type alloc_map;
 302       return alloc_map;
 303     }
 304   };
 305
 306   template<typename Tp, typename Alloc = std::allocator<Tp> >
 307     class uneq_allocator
 308     : private uneq_allocator_base,
 309       public Alloc
 310     {
 311       typedef __gnu_cxx::__alloc_traits<Alloc> AllocTraits;
 312
 313       Alloc& base() { return *this; }
 314       const Alloc& base() const  { return *this; }
 315       void swap_base(Alloc& b) { using std::swap; swap(b, this->base()); }
 316
 317     public:
 318       typedef typename check_consistent_alloc_value_type<Tp, Alloc>::value_type
 319         value_type;
 320       typedef typename AllocTraits::size_type   size_type;
 321       typedef typename AllocTraits::pointer     pointer;
 322
 323 #if __cplusplus >= 201103L
 324       typedef std::true_type                    propagate_on_container_swap;
 325       typedef std::false_type                   is_always_equal;
 326 #endif
 327
 328       template<typename Tp1>
 329         struct rebind
 330         {
 331           typedef uneq_allocator<Tp1,
 332                 typename AllocTraits::template rebind<Tp1>::other> other;
 333         };
 334
 335       uneq_allocator() _GLIBCXX_USE_NOEXCEPT
 336       : personality(0) { }
 337
 338       uneq_allocator(int person) _GLIBCXX_USE_NOEXCEPT
 339       : personality(person) { }
 340
 341 #if __cplusplus >= 201103L
 342       uneq_allocator(const uneq_allocator&) = default;
 343       uneq_allocator(uneq_allocator&&) = default;
 344 #endif
 345
 346       template<typename Tp1>
 347         uneq_allocator(const uneq_allocator<Tp1,
 348                        typename AllocTraits::template rebind<Tp1>::other>& b)
 349         _GLIBCXX_USE_NOEXCEPT
 350         : personality(b.get_personality()) { }
 351
 352       ~uneq_allocator() _GLIBCXX_USE_NOEXCEPT
 353       { }
 354
 355       int get_personality() const { return personality; }
 356
 357       pointer
 358       allocate(size_type n, const void* = 0)
 359       {
 360         pointer p = AllocTraits::allocate(*this, n);
 361
 362         try
 363           {
 364             get_map().insert(map_type::value_type(reinterpret_cast<void*>(p),
 365                                                   personality));
 366           }
 367         catch(...)
 368           {
 369             AllocTraits::deallocate(*this, p, n);
 370             __throw_exception_again;
 371           }
 372
 373         return p;
 374       }
 375
 376       void
 377       deallocate(pointer p, size_type n)
 378       {
 379         VERIFY( p );
 380
 381         map_type::iterator it = get_map().find(reinterpret_cast<void*>(p));
 382         VERIFY( it != get_map().end() );
 383
 384         // Enforce requirements in Table 32 about deallocation vs
 385         // allocator equality.
 386         VERIFY( it->second == personality );
 387
 388         get_map().erase(it);
 389         AllocTraits::deallocate(*this, p, n);
 390       }
 391
 392 #if __cplusplus >= 201103L
 393       // Not copy assignable...
 394       uneq_allocator&
 395       operator=(const uneq_allocator&) = delete;
 396
 397       // ... but still moveable if base allocator is.
 398       uneq_allocator&
 399       operator=(uneq_allocator&&) = default;
 400 #else
 401     private:
 402       // Not assignable...
 403       uneq_allocator&
 404       operator=(const uneq_allocator&);
 405 #endif
 406
 407     private:
 408       // ... yet swappable!
 409       friend inline void
 410       swap(uneq_allocator& a, uneq_allocator& b)
 411       {
 412         std::swap(a.personality, b.personality);
 413         a.swap_base(b);
 414       }
 415
 416       template<typename Tp1>
 417         friend inline bool
 418         operator==(const uneq_allocator& a,
 419                    const uneq_allocator<Tp1,
 420                    typename AllocTraits::template rebind<Tp1>::other>& b)
 421         { return a.personality == b.get_personality(); }
 422
 423       template<typename Tp1>
 424         friend inline bool
 425         operator!=(const uneq_allocator& a,
 426                    const uneq_allocator<Tp1,
 427                    typename AllocTraits::template rebind<Tp1>::other>& b)
 428         { return !(a == b); }
 429
 430       int personality;
 431     };
 432
 433 #if __cplusplus >= 201103L
 434   // An uneq_allocator which can be used to test allocator propagation.
 435   template<typename Tp, bool Propagate, typename Alloc = std::allocator<Tp>>
 436     class propagating_allocator : public uneq_allocator<Tp, Alloc>
 437     {
 438       typedef __gnu_cxx::__alloc_traits<Alloc> AllocTraits;
 439
 440       typedef uneq_allocator<Tp, Alloc> base_alloc;
 441       base_alloc& base() { return *this; }
 442       const base_alloc& base() const  { return *this; }
 443       void swap_base(base_alloc& b) { swap(b, this->base()); }
 444
 445       typedef std::integral_constant<bool, Propagate> trait_type;
 446
 447     public:
 448       // default allocator_traits::rebind_alloc would select
 449       // uneq_allocator::rebind so we must define rebind here
 450       template<typename Up>
 451         struct rebind
 452         {
 453           typedef propagating_allocator<Up, Propagate,
 454                 typename AllocTraits::template rebind<Up>::other> other;
 455         };
 456
 457       propagating_allocator(int i) noexcept
 458       : base_alloc(i)
 459       { }
 460
 461       template<typename Up>
 462         propagating_allocator(const propagating_allocator<Up, Propagate,
 463                               typename AllocTraits::template rebind<Up>::other>& a)
 464         noexcept
 465         : base_alloc(a)
 466         { }
 467
 468       propagating_allocator() noexcept = default;
 469
 470       propagating_allocator(const propagating_allocator&) noexcept = default;
 471
 472       propagating_allocator&
 473       operator=(const propagating_allocator& a) noexcept
 474       {
 475         static_assert(Propagate, "assigning propagating_allocator<T, true>");
 476         propagating_allocator(a).swap_base(*this);
 477         return *this;
 478       }
 479
 480       template<bool P2>
 481         propagating_allocator&
 482         operator=(const propagating_allocator<Tp, P2, Alloc>& a) noexcept
 483         {
 484           static_assert(P2, "assigning propagating_allocator<T, true>");
 485           propagating_allocator(a).swap_base(*this);
 486           return *this;
 487         }
 488
 489       // postcondition: LWG2593 a.get_personality() un-changed.
 490       propagating_allocator(propagating_allocator&& a) noexcept
 491       : base_alloc(std::move(a.base()))
 492       { }
 493
 494       // postcondition: LWG2593 a.get_personality() un-changed
 495       propagating_allocator&
 496       operator=(propagating_allocator&& a) noexcept
 497       {
 498         propagating_allocator(std::move(a)).swap_base(*this);
 499         return *this;
 500       }
 501
 502       typedef trait_type propagate_on_container_copy_assignment;
 503       typedef trait_type propagate_on_container_move_assignment;
 504       typedef trait_type propagate_on_container_swap;
 505
 506       propagating_allocator select_on_container_copy_construction() const
 507       { return Propagate ? *this : propagating_allocator(); }
 508     };
 509
 510   // Class template supporting the minimal interface that satisfies the
 511   // Allocator requirements, from example in [allocator.requirements]
 512   template <class Tp>
 513     struct SimpleAllocator
 514     {
 515       typedef Tp value_type;
 516
 517       constexpr SimpleAllocator() noexcept { }
 518
 519       template <class T>
 520         SimpleAllocator(const SimpleAllocator<T>&) { }
 521
 522       Tp *allocate(std::size_t n)
 523       { return std::allocator<Tp>().allocate(n); }
 524
 525       void deallocate(Tp *p, std::size_t n)
 526       { std::allocator<Tp>().deallocate(p, n); }
 527     };
 528
 529   template <class T, class U>
 530     bool operator==(const SimpleAllocator<T>&, const SimpleAllocator<U>&)
 531     { return true; }
 532   template <class T, class U>
 533     bool operator!=(const SimpleAllocator<T>&, const SimpleAllocator<U>&)
 534     { return false; }
 535
 536   template<typename T>
 537     struct default_init_allocator
 538     {
 539       using value_type = T;
 540
 541       default_init_allocator() = default;
 542
 543       template<typename U>
 544         default_init_allocator(const default_init_allocator<U>& a)
 545           : state(a.state)
 546         { }
 547
 548       T*
 549       allocate(std::size_t n)
 550       { return std::allocator<T>().allocate(n); }
 551
 552       void
 553       deallocate(T* p, std::size_t n)
 554       { std::allocator<T>().deallocate(p, n); }
 555
 556       int state;
 557     };
 558
 559   template<typename T, typename U>
 560     bool operator==(const default_init_allocator<T>& t,
 561                     const default_init_allocator<U>& u)
 562     { return t.state == u.state; }
 563
 564   template<typename T, typename U>
 565     bool operator!=(const default_init_allocator<T>& t,
 566                     const default_init_allocator<U>& u)
 567     { return !(t == u); }
 568 #endif
 569
 570   template<typename Tp>
 571     struct ExplicitConsAlloc : std::allocator<Tp>
 572     {
 573       ExplicitConsAlloc() { }
 574
 575       template<typename Up>
 576         explicit
 577         ExplicitConsAlloc(const ExplicitConsAlloc<Up>&) { }
 578
 579       template<typename Up>
 580         struct rebind
 581         { typedef ExplicitConsAlloc<Up> other; };
 582     };
 583
 584 #if __cplusplus >= 201103L
 585   template<typename Tp>
 586     class CustomPointerAlloc : public std::allocator<Tp>
 587     {
 588       template<typename Up, typename Sp = __gnu_cxx::_Std_pointer_impl<Up>>
 589         using Ptr =  __gnu_cxx::_Pointer_adapter<Sp>;
 590
 591     public:
 592       CustomPointerAlloc() = default;
 593
 594       template<typename Up>
 595         CustomPointerAlloc(const CustomPointerAlloc<Up>&) { }
 596
 597       template<typename Up>
 598         struct rebind
 599         { typedef CustomPointerAlloc<Up> other; };
 600
 601       typedef Ptr<Tp>           pointer;
 602       typedef Ptr<const Tp>     const_pointer;
 603       typedef Ptr<void>         void_pointer;
 604       typedef Ptr<const void>   const_void_pointer;
 605
 606       pointer allocate(std::size_t n, const_void_pointer = {})
 607       { return pointer(std::allocator<Tp>::allocate(n)); }
 608
 609       void deallocate(pointer p, std::size_t n)
 610       { std::allocator<Tp>::deallocate(std::addressof(*p), n); }
 611     };
 612
 613   // A class type meeting *only* the Cpp17NullablePointer requirements.
 614   // Can be used as a base class for fancy pointers (like PointerBase, below)
 615   // or to wrap a built-in pointer type to remove operations not required
 616   // by the Cpp17NullablePointer requirements (dereference, increment etc.)
 617   template<typename Ptr>
 618     struct NullablePointer
 619     {
 620       // N.B. default constructor does not initialize value
 621       NullablePointer() = default;
 622       NullablePointer(std::nullptr_t) noexcept : value() { }
 623
 624       explicit operator bool() const noexcept { return value != nullptr; }
 625
 626       friend inline bool
 627       operator==(NullablePointer lhs, NullablePointer rhs) noexcept
 628       { return lhs.value == rhs.value; }
 629
 630       friend inline bool
 631       operator!=(NullablePointer lhs, NullablePointer rhs) noexcept
 632       { return lhs.value != rhs.value; }
 633
 634     protected:
 635       explicit NullablePointer(Ptr p) noexcept : value(p) { }
 636       Ptr value;
 637     };
 638
 639   // NullablePointer<void> is an empty type that models Cpp17NullablePointer.
 640   template<>
 641     struct NullablePointer<void>
 642     {
 643       NullablePointer() = default;
 644       NullablePointer(std::nullptr_t) noexcept { }
 645       explicit NullablePointer(const volatile void*) noexcept { }
 646
 647       explicit operator bool() const noexcept { return false; }
 648
 649       friend inline bool
 650       operator==(NullablePointer, NullablePointer) noexcept
 651       { return true; }
 652
 653       friend inline bool
 654       operator!=(NullablePointer, NullablePointer) noexcept
 655       { return false; }
 656     };
 657
 658   // Utility for use as CRTP base class of custom pointer types
 659   template<typename Derived, typename T>
 660     struct PointerBase : NullablePointer<T*>
 661     {
 662       typedef T element_type;
 663
 664       // typedefs for iterator_traits
 665       typedef T value_type;
 666       typedef std::ptrdiff_t difference_type;
 667       typedef std::random_access_iterator_tag iterator_category;
 668       typedef Derived pointer;
 669       typedef T& reference;
 670
 671       using NullablePointer<T*>::NullablePointer;
 672
 673       // Public (but explicit) constructor from raw pointer:
 674       explicit PointerBase(T* p) noexcept : NullablePointer<T*>(p) { }
 675
 676       template<typename D, typename U,
 677                typename = decltype(static_cast<T*>(std::declval<U*>()))>
 678         PointerBase(const PointerBase<D, U>& p)
 679         : NullablePointer<T*>(p.operator->()) { }
 680
 681       T& operator*() const { return *this->value; }
 682       T* operator->() const { return this->value; }
 683       T& operator[](difference_type n) const { return this->value[n]; }
 684
 685       Derived& operator++() { ++this->value; return derived(); }
 686       Derived& operator--() { --this->value; return derived(); }
 687
 688       Derived operator++(int) { return Derived(this->value++); }
 689
 690       Derived operator--(int) { return Derived(this->value--); }
 691
 692       Derived& operator+=(difference_type n)
 693       {
 694         this->value += n;
 695         return derived();
 696       }
 697
 698       Derived& operator-=(difference_type n)
 699       {
 700         this->value -= n;
 701         return derived();
 702       }
 703
 704       Derived
 705       operator+(difference_type n) const
 706       {
 707         Derived p(derived());
 708         return p += n;
 709       }
 710
 711       Derived
 712       operator-(difference_type n) const
 713       {
 714         Derived p(derived());
 715         return p -= n;
 716       }
 717
 718     private:
 719       friend std::ptrdiff_t operator-(PointerBase l, PointerBase r)
 720       { return l.value - r.value; }
 721
 722       friend bool operator<(PointerBase l, PointerBase r)
 723       { return l.value < r.value; }
 724       friend bool operator>(PointerBase l, PointerBase r)
 725       { return l.value > r.value; }
 726       friend bool operator<=(PointerBase l, PointerBase r)
 727       { return l.value <= r.value; }
 728       friend bool operator>=(PointerBase l, PointerBase r)
 729       { return l.value >= r.value; }
 730
 731       Derived&
 732       derived() { return static_cast<Derived&>(*this); }
 733
 734       const Derived&
 735       derived() const { return static_cast<const Derived&>(*this); }
 736     };
 737
 738   // implementation for pointer-to-void specializations
 739   template<typename T>
 740     struct PointerBase_void : NullablePointer<T*>
 741     {
 742       typedef T element_type;
 743
 744       // typedefs for iterator_traits
 745       typedef T value_type;
 746       typedef std::ptrdiff_t difference_type;
 747       typedef std::random_access_iterator_tag iterator_category;
 748
 749       using NullablePointer<T*>::NullablePointer;
 750
 751       T* operator->() const { return this->value; }
 752
 753       template<typename D, typename U,
 754                typename = decltype(static_cast<T*>(std::declval<U*>()))>
 755         PointerBase_void(const PointerBase<D, U>& p)
 756         : NullablePointer<T*>(p.operator->()) { }
 757     };
 758
 759   template<typename Derived>
 760     struct PointerBase<Derived, void> : PointerBase_void<void>
 761     {
 762       using PointerBase_void::PointerBase_void;
 763       typedef Derived pointer;
 764     };
 765
 766   template<typename Derived>
 767     struct PointerBase<Derived, const void> : PointerBase_void<const void>
 768     {
 769       using PointerBase_void::PointerBase_void;
 770       typedef Derived pointer;
 771     };
 772 #endif // C++11
 773
 774 #if __cplusplus >= 201703L
 775 #if __cpp_aligned_new
 776   // A concrete memory_resource, with error checking.
 777   class memory_resource : public std::pmr::memory_resource
 778   {
 779   public:
 780     memory_resource()
 781     : lists(new allocation_lists)
 782     { }
 783
 784     memory_resource(const memory_resource& r) noexcept
 785     : lists(r.lists)
 786     { lists->refcount++; }
 787
 788     memory_resource& operator=(const memory_resource&) = delete;
 789
 790     ~memory_resource()
 791     {
 792       if (lists->refcount-- == 1)
 793         delete lists;  // last one out turns out the lights
 794     }
 795
 796     struct bad_size { };
 797     struct bad_alignment { };
 798     struct bad_address { };
 799
 800     // Deallocate everything (moving the tracking info to the freed list)
 801     void
 802     deallocate_everything()
 803     {
 804       while (lists->active)
 805         {
 806           auto a = lists->active;
 807           // Intentionally virtual dispatch, to inform derived classes:
 808           this->do_deallocate(a->p, a->bytes, a->alignment);
 809         }
 810     }
 811
 812     // Clear the freed list
 813     void
 814     forget_freed_allocations()
 815     { lists->forget_allocations(lists->freed); }
 816
 817     // Count how many allocations have been done and not freed.
 818     std::size_t
 819     number_of_active_allocations() const noexcept
 820     {
 821       std::size_t n = 0;
 822       for (auto a = lists->active; a != nullptr; a = a->next)
 823         ++n;
 824       return n;
 825     }
 826
 827   protected:
 828     void*
 829     do_allocate(std::size_t bytes, std::size_t alignment) override
 830     {
 831       // TODO perform a single allocation and put the allocation struct
 832       // in the buffer using placement new? It means deallocation won't
 833       // actually return memory to the OS, as it will stay in lists->freed.
 834       //
 835       // TODO adjust the returned pointer to be minimally aligned?
 836       // e.g. if alignment==1 don't return something aligned to 2 bytes.
 837       // Maybe not worth it, at least monotonic_buffer_resource will
 838       // never ask upstream for anything with small alignment.
 839       void* p = ::operator new(bytes, std::align_val_t(alignment));
 840       lists->active = new allocation{p, bytes, alignment, lists->active};
 841       return p;
 842     }
 843
 844     void
 845     do_deallocate(void* p, std::size_t bytes, std::size_t alignment) override
 846     {
 847       allocation** aptr = &lists->active;
 848       while (*aptr)
 849         {
 850           allocation* a = *aptr;
 851           if (p == a->p)
 852             {
 853               if (bytes != a->bytes)
 854                 _S_throw<bad_size>();
 855               if (alignment != a->alignment)
 856                 _S_throw<bad_alignment>();
 857 #if __cpp_sized_deallocation
 858               ::operator delete(p, bytes, std::align_val_t(alignment));
 859 #else
 860               ::operator delete(p, std::align_val_t(alignment));
 861 #endif
 862               *aptr = a->next;
 863               a->next = lists->freed;
 864               lists->freed = a;
 865               return;
 866             }
 867           aptr = &a->next;
 868         }
 869       _S_throw<bad_address>();
 870     }
 871
 872     bool
 873     do_is_equal(const std::pmr::memory_resource& r) const noexcept override
 874     {
 875 #if __cpp_rtti
 876       // Equality is determined by sharing the same allocation_lists object.
 877       if (auto p = dynamic_cast<const memory_resource*>(&r))
 878         return p->lists == lists;
 879 #else
 880       if (this == &r) // Is this the best we can do without RTTI?
 881         return true;
 882 #endif
 883       return false;
 884     }
 885
 886   private:
 887     template<typename E>
 888       static void
 889       _S_throw()
 890       {
 891 #if __cpp_exceptions
 892         throw E();
 893 #else
 894         __builtin_abort();
 895 #endif
 896       }
 897
 898     struct allocation
 899     {
 900       void* p;
 901       std::size_t bytes;
 902       std::size_t alignment;
 903       allocation* next;
 904     };
 905
 906     // Maintain list of allocated blocks and list of freed blocks.
 907     // Copies of this memory_resource share the same ref-counted lists.
 908     struct allocation_lists
 909     {
 910       unsigned refcount = 1;
 911       allocation* active = nullptr;
 912       allocation* freed = nullptr;
 913
 914       void forget_allocations(allocation*& list)
 915       {
 916         while (list)
 917           {
 918             auto p = list;
 919             list = list->next;
 920             delete p;
 921           }
 922       }
 923
 924       ~allocation_lists()
 925       {
 926         forget_allocations(active); // Anything in this list is a leak!
 927         forget_allocations(freed);
 928       }
 929     };
 930
 931     allocation_lists* lists;
 932   };
 933 #endif // aligned-new
 934
 935   // Set the default resource, and restore the previous one on destruction.
 936   struct default_resource_mgr
 937   {
 938     explicit default_resource_mgr(std::pmr::memory_resource* r)
 939     : prev(std::pmr::set_default_resource(r))
 940     { }
 941
 942     ~default_resource_mgr()
 943     { std::pmr::set_default_resource(prev); }
 944
 945     std::pmr::memory_resource* prev;
 946   };
 947
 948 #endif // C++17
 949
 950 } // namespace __gnu_test
 951
 952 #endif // _GLIBCXX_TESTSUITE_ALLOCATOR_H