[mem.res]

# 20 Memory management library [[mem]](./#mem)

## 20.5 Memory resources [mem.res]

### [20.5.1](#syn) Header <memory_resource> synopsis [[mem.res.syn]](mem.res.syn)

[ð](#header:%3cmemory_resource%3e)

namespace std::pmr {// [[mem.res.class]](#class "20.5.2 Class memory_­resource"), class memory_resourceclass memory_resource; bool operator==(const memory_resource& a, const memory_resource& b) noexcept; // [[mem.poly.allocator.class]](#mem.poly.allocator.class "20.5.3 Class template polymorphic_­allocator"), class template polymorphic_allocatortemplate<class Tp = byte> class polymorphic_allocator; template<class T1, class T2>bool operator==(const polymorphic_allocator<T1>& a, const polymorphic_allocator<T2>& b) noexcept; // [[mem.res.global]](#global "20.5.4 Access to program-wide memory_­resource objects"), global memory resources memory_resource* new_delete_resource() noexcept;
 memory_resource* null_memory_resource() noexcept;
 memory_resource* set_default_resource(memory_resource* r) noexcept;
 memory_resource* get_default_resource() noexcept; // [[mem.res.pool]](#pool "20.5.5 Pool resource classes"), pool resource classesstruct pool_options; class synchronized_pool_resource; class unsynchronized_pool_resource; class monotonic_buffer_resource;}

### [20.5.2](#class) Class memory_resource [[mem.res.class]](mem.res.class)

#### [20.5.2.1](#class.general) General [[mem.res.class.general]](mem.res.class.general)

[1](#class.general-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7484)

The memory_resource class is an abstract interface to an unbounded set of classes encapsulating memory resources[.](#class.general-1.sentence-1)

[ð](#lib:memory_resource)

namespace std::pmr {class memory_resource {static constexpr size_t max_align = alignof(max_align_t); // *exposition only*public: memory_resource() = default;
 memory_resource(const memory_resource&) = default; virtual ~memory_resource();

 memory_resource& operator=(const memory_resource&) = default; void* allocate(size_t bytes, size_t alignment = max_align); void deallocate(void* p, size_t bytes, size_t alignment = max_align); bool is_equal(const memory_resource& other) const noexcept; private:virtual void* do_allocate(size_t bytes, size_t alignment) = 0; virtual void do_deallocate(void* p, size_t bytes, size_t alignment) = 0; virtual bool do_is_equal(const memory_resource& other) const noexcept = 0; };}

#### [20.5.2.2](#public) Public member functions [[mem.res.public]](mem.res.public)

[ð](#lib:memory_resource,destructor)

`~memory_resource();
`

[1](#public-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7524)

*Effects*: Destroys this memory_resource[.](#public-1.sentence-1)

[ð](#lib:allocate,memory_resource)

`void* allocate(size_t bytes, size_t alignment = max_align);
`

[2](#public-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7535)

*Effects*: Allocates storage by calling do_allocate(bytes, alignment) and
implicitly creates objects within the allocated region of storage[.](#public-2.sentence-1)

[3](#public-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7540)

*Returns*: A pointer to a suitable created object ([[intro.object]](intro.object "6.8.2 Object model"))
in the allocated region of storage[.](#public-3.sentence-1)

[4](#public-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7545)

*Throws*: What and when the call to do_allocate throws[.](#public-4.sentence-1)

[ð](#lib:deallocate,memory_resource)

`void deallocate(void* p, size_t bytes, size_t alignment = max_align);
`

[5](#public-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7556)

*Effects*: Equivalent to do_deallocate(p, bytes, alignment)[.](#public-5.sentence-1)

[ð](#lib:is_equal,memory_resource)

`bool is_equal(const memory_resource& other) const noexcept;
`

[6](#public-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7567)

*Effects*: Equivalent to: return do_is_equal(other);

#### [20.5.2.3](#private) Private virtual member functions [[mem.res.private]](mem.res.private)

[ð](#lib:do_allocate,memory_resource)

`virtual void* do_allocate(size_t bytes, size_t alignment) = 0;
`

[1](#private-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7581)

*Preconditions*: alignment is a power of two[.](#private-1.sentence-1)

[2](#private-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7585)

*Returns*: A derived class shall implement this function to
return a pointer to allocated storage ([[basic.stc.dynamic.allocation]](basic.stc.dynamic.allocation "6.8.6.5.2 Allocation functions"))
with a size of at least bytes,
aligned to the specified alignment[.](#private-2.sentence-1)

[3](#private-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7592)

*Throws*: A derived class implementation shall throw an appropriate exception if it is unable to allocate memory with the requested size and alignment[.](#private-3.sentence-1)

[ð](#lib:do_deallocate,memory_resource)

`virtual void do_deallocate(void* p, size_t bytes, size_t alignment) = 0;
`

[4](#private-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7603)

*Preconditions*: p was returned from a prior call to allocate(bytes, alignment) on a memory resource equal to *this,
and the storage at p has not yet been deallocated[.](#private-4.sentence-1)

[5](#private-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7609)

*Effects*: A derived class shall implement this function to dispose of allocated storage[.](#private-5.sentence-1)

[6](#private-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7613)

*Throws*: Nothing[.](#private-6.sentence-1)

[ð](#lib:do_is_equal,memory_resource)

`virtual bool do_is_equal(const memory_resource& other) const noexcept = 0;
`

[7](#private-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7624)

*Returns*: A derived class shall implement this function to return true if memory allocated from *this can be deallocated from other and vice-versa,
otherwise false[.](#private-7.sentence-1)

[*Note [1](#private-note-1)*:

It is possible that the most-derived type of other does not match the type of *this[.](#private-7.sentence-2)

For a derived class D, an implementation of this function
can immediately return false if dynamic_cast<const D*>(&other) == nullptr[.](#private-7.sentence-3)

â *end note*]

#### [20.5.2.4](#eq) Equality [[mem.res.eq]](mem.res.eq)

[ð](#lib:operator==,memory_resource)

`bool operator==(const memory_resource& a, const memory_resource& b) noexcept;
`

[1](#eq-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7644)

*Returns*: &a == &b || a.is_equal(b)[.](#eq-1.sentence-1)

### [20.5.3](#mem.poly.allocator.class) Class template polymorphic_allocator [[mem.poly.allocator.class]](mem.poly.allocator.class)

#### [20.5.3.1](#mem.poly.allocator.class.general) General [[mem.poly.allocator.class.general]](mem.poly.allocator.class.general)

[1](#mem.poly.allocator.class.general-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7653)

A specialization of class template pmr​::​polymorphic_allocator meets
the *Cpp17Allocator* requirements ([[allocator.requirements.general]](allocator.requirements.general "16.4.4.6.1 General"))
if its template argument is a cv-unqualified object type[.](#mem.poly.allocator.class.general-1.sentence-1)

Constructed with different memory resources,
different instances of the same specialization of pmr​::​polymorphic_allocator can exhibit entirely different allocation behavior[.](#mem.poly.allocator.class.general-1.sentence-2)

This runtime polymorphism allows objects that use polymorphic_allocator to behave as if they used different allocator types at run time
even though they use the same static allocator type[.](#mem.poly.allocator.class.general-1.sentence-3)

[2](#mem.poly.allocator.class.general-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7664)

A specialization of class template pmr​::​polymorphic_allocator meets the allocator completeness requirements ([[allocator.requirements.completeness]](allocator.requirements.completeness "16.4.4.6.2 Allocator completeness requirements"))
if its template argument is a cv-unqualified object type[.](#mem.poly.allocator.class.general-2.sentence-1)

[ð](#lib:polymorphic_allocator)

namespace std::pmr {template<class Tp = byte> class polymorphic_allocator { memory_resource* memory_rsrc; // *exposition only*public:using value_type = Tp; // [[mem.poly.allocator.ctor]](#mem.poly.allocator.ctor "20.5.3.2 Constructors"), constructors polymorphic_allocator() noexcept;
 polymorphic_allocator(memory_resource* r);

 polymorphic_allocator(const polymorphic_allocator& other) = default; template<class U> polymorphic_allocator(const polymorphic_allocator<U>& other) noexcept;

 polymorphic_allocator& operator=(const polymorphic_allocator&) = delete; // [[mem.poly.allocator.mem]](#mem.poly.allocator.mem "20.5.3.3 Member functions"), member functions Tp* allocate(size_t n); void deallocate(Tp* p, size_t n); void* allocate_bytes(size_t nbytes, size_t alignment = alignof(max_align_t)); void deallocate_bytes(void* p, size_t nbytes, size_t alignment = alignof(max_align_t)); template<class T> T* allocate_object(size_t n = 1); template<class T> void deallocate_object(T* p, size_t n = 1); template<class T, class... CtorArgs> T* new_object(CtorArgs&&... ctor_args); template<class T> void delete_object(T* p); template<class T, class... Args>void construct(T* p, Args&&... args); template<class T>void destroy(T* p);

 polymorphic_allocator select_on_container_copy_construction() const;

 memory_resource* resource() const; // friendsfriend bool operator==(const polymorphic_allocator& a, const polymorphic_allocator& b) noexcept {return *a.resource() == *b.resource(); }};}

#### [20.5.3.2](#mem.poly.allocator.ctor) Constructors [[mem.poly.allocator.ctor]](mem.poly.allocator.ctor)

[ð](#lib:polymorphic_allocator,constructor)

`polymorphic_allocator() noexcept;
`

[1](#mem.poly.allocator.ctor-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7728)

*Effects*: Sets memory_rsrc to get_default_resource()[.](#mem.poly.allocator.ctor-1.sentence-1)

[ð](#lib:polymorphic_allocator,constructor_)

`polymorphic_allocator(memory_resource* r);
`

[2](#mem.poly.allocator.ctor-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7739)

*Preconditions*: r is non-null[.](#mem.poly.allocator.ctor-2.sentence-1)

[3](#mem.poly.allocator.ctor-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7743)

*Effects*: Sets memory_rsrc to r[.](#mem.poly.allocator.ctor-3.sentence-1)

[4](#mem.poly.allocator.ctor-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7747)

*Throws*: Nothing[.](#mem.poly.allocator.ctor-4.sentence-1)

[5](#mem.poly.allocator.ctor-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7751)

[*Note [1](#mem.poly.allocator.ctor-note-1)*:

This constructor provides an implicit conversion from memory_resource*[.](#mem.poly.allocator.ctor-5.sentence-1)

â *end note*]

[ð](#lib:polymorphic_allocator,constructor__)

`template<class U> polymorphic_allocator(const polymorphic_allocator<U>& other) noexcept;
`

[6](#mem.poly.allocator.ctor-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7763)

*Effects*: Sets memory_rsrc to other.resource()[.](#mem.poly.allocator.ctor-6.sentence-1)

#### [20.5.3.3](#mem.poly.allocator.mem) Member functions [[mem.poly.allocator.mem]](mem.poly.allocator.mem)

[ð](#lib:allocate,polymorphic_allocator)

`Tp* allocate(size_t n);
`

[1](#mem.poly.allocator.mem-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7777)

*Effects*: If numeric_limits<size_t>​::​max() / sizeof(Tp) < n,
throws bad_array_new_length[.](#mem.poly.allocator.mem-1.sentence-1)

Otherwise equivalent to:return static_cast<Tp*>(memory_rsrc->allocate(n * sizeof(Tp), alignof(Tp)));

[ð](#lib:deallocate,polymorphic_allocator)

`void deallocate(Tp* p, size_t n);
`

[2](#mem.poly.allocator.mem-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7793)

*Preconditions*: p was allocated from a memory resource x,
equal to *memory_rsrc,
using x.allocate(n * sizeof(Tp), alignof(Tp))[.](#mem.poly.allocator.mem-2.sentence-1)

[3](#mem.poly.allocator.mem-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7799)

*Effects*: Equivalent to memory_rsrc->deallocate(p, n * sizeof(Tp), alignof(Tp))[.](#mem.poly.allocator.mem-3.sentence-1)

[4](#mem.poly.allocator.mem-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7803)

*Throws*: Nothing[.](#mem.poly.allocator.mem-4.sentence-1)

[ð](#lib:allocate_bytes,polymorphic_allocator)

`void* allocate_bytes(size_t nbytes, size_t alignment = alignof(max_align_t));
`

[5](#mem.poly.allocator.mem-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7814)

*Effects*: Equivalent to: return memory_rsrc->allocate(nbytes, alignment);

[6](#mem.poly.allocator.mem-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7818)

[*Note [1](#mem.poly.allocator.mem-note-1)*:

The return type is void* (rather than, e.g., byte*)
to support conversion to an arbitrary pointer type U* by static_cast<U*>, thus facilitating construction of a U object in the allocated memory[.](#mem.poly.allocator.mem-6.sentence-1)

â *end note*]

[ð](#lib:deallocate_bytes,polymorphic_allocator)

`void deallocate_bytes(void* p, size_t nbytes, size_t alignment = alignof(max_align_t));
`

[7](#mem.poly.allocator.mem-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7833)

*Effects*: Equivalent to memory_rsrc->deallocate(p, nbytes, alignment)[.](#mem.poly.allocator.mem-7.sentence-1)

[ð](#lib:allocate_object,polymorphic_allocator)

`template<class T>
  T* allocate_object(size_t n = 1);
`

[8](#mem.poly.allocator.mem-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7845)

*Effects*: Allocates memory suitable for holding
an array of n objects of type T, as follows:

- [(8.1)](#mem.poly.allocator.mem-8.1)

if numeric_limits<size_t>​::​max() / sizeof(T) < n,
 throws bad_array_new_length,

- [(8.2)](#mem.poly.allocator.mem-8.2)

otherwise equivalent to:return static_cast<T*>(allocate_bytes(n*sizeof(T), alignof(T)));

[9](#mem.poly.allocator.mem-9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7860)

[*Note [2](#mem.poly.allocator.mem-note-2)*:

T is not deduced and must therefore be provided as a template argument[.](#mem.poly.allocator.mem-9.sentence-1)

â *end note*]

[ð](#lib:deallocate_object,polymorphic_allocator)

`template<class T>
  void deallocate_object(T* p, size_t n = 1);
`

[10](#mem.poly.allocator.mem-10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7873)

*Effects*: Equivalent to deallocate_bytes(p, n*sizeof(T), alignof(T))[.](#mem.poly.allocator.mem-10.sentence-1)

[ð](#lib:new_object,polymorphic_allocator)

`template<class T, class... CtorArgs>
  T* new_object(CtorArgs&&... ctor_args);
`

[11](#mem.poly.allocator.mem-11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7885)

*Effects*: Allocates and constructs an object of type T, as follows[.](#mem.poly.allocator.mem-11.sentence-1)

  
Equivalent to:T* p = allocate_object<T>();try { construct(p, std::forward<CtorArgs>(ctor_args)...);} catch (...) { deallocate_object(p); throw;}return p;

[12](#mem.poly.allocator.mem-12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7900)

[*Note [3](#mem.poly.allocator.mem-note-3)*:

T is not deduced and must therefore be provided as a template argument[.](#mem.poly.allocator.mem-12.sentence-1)

â *end note*]

[ð](#lib:new_object,polymorphic_allocator_)

`template<class T>
  void delete_object(T* p);
`

[13](#mem.poly.allocator.mem-13)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7913)

*Effects*: Equivalent to:destroy(p);
deallocate_object(p);

[ð](#lib:construct,polymorphic_allocator)

`template<class T, class... Args>
  void construct(T* p, Args&&... args);
`

[14](#mem.poly.allocator.mem-14)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7929)

*Mandates*: Uses-allocator construction of T with allocator *this (see [[allocator.uses.construction]](allocator.uses.construction "20.2.8.2 Uses-allocator construction"))
and constructor arguments std​::​forward<Args>(args)... is well-formed[.](#mem.poly.allocator.mem-14.sentence-1)

[15](#mem.poly.allocator.mem-15)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7935)

*Effects*: Constructs a T object in the storage
whose address is represented by p by uses-allocator construction with allocator *this and constructor arguments std​::​forward<Args>(args)...[.](#mem.poly.allocator.mem-15.sentence-1)

[16](#mem.poly.allocator.mem-16)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7942)

*Throws*: Nothing unless the constructor for T throws[.](#mem.poly.allocator.mem-16.sentence-1)

[ð](#lib:destroy,polymorphic_allocator)

`template<class T>
  void destroy(T* p);
`

[17](#mem.poly.allocator.mem-17)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7954)

*Effects*: Equivalent to p->~T()[.](#mem.poly.allocator.mem-17.sentence-1)

[ð](#lib:select_on_container_copy_construction,polymorphic_allocator)

`polymorphic_allocator select_on_container_copy_construction() const;
`

[18](#mem.poly.allocator.mem-18)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7965)

*Returns*: polymorphic_allocator()[.](#mem.poly.allocator.mem-18.sentence-1)

[19](#mem.poly.allocator.mem-19)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7969)

[*Note [4](#mem.poly.allocator.mem-note-4)*:

The memory resource is not propagated[.](#mem.poly.allocator.mem-19.sentence-1)

â *end note*]

[ð](#lib:resource,polymorphic_allocator)

`memory_resource* resource() const;
`

[20](#mem.poly.allocator.mem-20)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7981)

*Returns*: memory_rsrc[.](#mem.poly.allocator.mem-20.sentence-1)

#### [20.5.3.4](#mem.poly.allocator.eq) Equality [[mem.poly.allocator.eq]](mem.poly.allocator.eq)

[ð](#lib:operator==,polymorphic_allocator)

`template<class T1, class T2>
  bool operator==(const polymorphic_allocator<T1>& a,
                  const polymorphic_allocator<T2>& b) noexcept;
`

[1](#mem.poly.allocator.eq-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L7996)

*Returns*: *a.resource() == *b.resource()[.](#mem.poly.allocator.eq-1.sentence-1)

### [20.5.4](#global) Access to program-wide memory_resource objects [[mem.res.global]](mem.res.global)

[ð](#lib:new_delete_resource)

`memory_resource* new_delete_resource() noexcept;
`

[1](#global-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8009)

*Returns*: A pointer to a static-duration object of a type derived from memory_resource that can serve as a resource for allocating memory
using ​::​operator new and ​::​operator delete[.](#global-1.sentence-1)

The same value is returned every time this function is called[.](#global-1.sentence-2)

For a return value p and a memory resource r,p->is_equal(r) returns &r == p[.](#global-1.sentence-3)

[ð](#lib:null_memory_resource)

`memory_resource* null_memory_resource() noexcept;
`

[2](#global-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8025)

*Returns*: A pointer to a static-duration object of a type derived from memory_resource for which allocate() always throws bad_alloc and
for which deallocate() has no effect[.](#global-2.sentence-1)

The same value is returned every time this function is called[.](#global-2.sentence-2)

For a return value p and a memory resource r,p->is_equal(r) returns &r == p[.](#global-2.sentence-3)

[3](#global-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8035)

The [*default memory resource pointer*](#def:default_memory_resource_pointer "20.5.4 Access to program-wide memory_­resource objects [mem.res.global]") is a pointer to a memory resource
that is used by certain facilities when an explicit memory resource
is not supplied through the interface[.](#global-3.sentence-1)

Its initial value is the return value of new_delete_resource()[.](#global-3.sentence-2)

[ð](#lib:set_default_resource)

`memory_resource* set_default_resource(memory_resource* r) noexcept;
`

[4](#global-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8047)

*Effects*: If r is non-null,
sets the value of the default memory resource pointer to r,
otherwise sets the default memory resource pointer to new_delete_resource()[.](#global-4.sentence-1)

[5](#global-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8053)

*Returns*: The previous value of the default memory resource pointer[.](#global-5.sentence-1)

[6](#global-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8057)

*Remarks*: Calling the set_default_resource andget_default_resource functions shall not incur a data race ([[intro.races]](intro.races "6.10.2.2 Data races"))[.](#global-6.sentence-1)

A call to the set_default_resource function
synchronizes with subsequent calls to
the set_default_resource and get_default_resource functions[.](#global-6.sentence-2)

[ð](#lib:get_default_resource)

`memory_resource* get_default_resource() noexcept;
`

[7](#global-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8072)

*Returns*: The current value of the default memory resource pointer[.](#global-7.sentence-1)

### [20.5.5](#pool) Pool resource classes [[mem.res.pool]](mem.res.pool)

#### [20.5.5.1](#pool.overview) Classes synchronized_pool_resource and unsynchronized_pool_resource [[mem.res.pool.overview]](mem.res.pool.overview)

[1](#pool.overview-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8081)

The synchronized_pool_resource andunsynchronized_pool_resource classes
(collectively called [*pool resource classes*](#def:pool_resource_classes "20.5.5.1 Classes synchronized_­pool_­resource and unsynchronized_­pool_­resource [mem.res.pool.overview]"))
are general-purpose memory resources having the following qualities:

- [(1.1)](#pool.overview-1.1)

  Each resource frees its allocated memory on destruction,
even if deallocate has not been called for some of the allocated blocks[.](#pool.overview-1.1.sentence-1)

- [(1.2)](#pool.overview-1.2)

  A pool resource consists of a collection of [*pools*](#def:pools "20.5.5.1 Classes synchronized_­pool_­resource and unsynchronized_­pool_­resource [mem.res.pool.overview]"),
serving requests for different block sizes[.](#pool.overview-1.2.sentence-1)
  Each individual pool manages a collection of [*chunks*](#def:chunks "20.5.5.1 Classes synchronized_­pool_­resource and unsynchronized_­pool_­resource [mem.res.pool.overview]") that are in turn divided into blocks of uniform size,
returned via calls to do_allocate[.](#pool.overview-1.2.sentence-2)
  Each call to do_allocate(size, alignment) is dispatched
to the pool serving the smallest blocks accommodating at least size bytes[.](#pool.overview-1.2.sentence-3)

- [(1.3)](#pool.overview-1.3)

  When a particular pool is exhausted,
allocating a block from that pool results in the allocation
of an additional chunk of memory from the [*upstream allocator*](#def:upstream_allocator "20.5.5.1 Classes synchronized_­pool_­resource and unsynchronized_­pool_­resource [mem.res.pool.overview]") (supplied at construction), thus replenishing the pool[.](#pool.overview-1.3.sentence-1)
  With each successive replenishment,
the chunk size obtained increases geometrically[.](#pool.overview-1.3.sentence-2)
  [*Note [1](#pool.overview-note-1)*:
  By allocating memory in chunks,
the pooling strategy increases the chance that consecutive allocations
will be close together in memory[.](#pool.overview-1.3.sentence-3)
 â *end note*]

- [(1.4)](#pool.overview-1.4)

  Allocation requests that exceed the largest block size of any pool
are fulfilled directly from the upstream allocator[.](#pool.overview-1.4.sentence-1)

- [(1.5)](#pool.overview-1.5)

  A pool_options struct may be passed to the pool resource constructors
to tune the largest block size and the maximum chunk size[.](#pool.overview-1.5.sentence-1)

[2](#pool.overview-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8118)

A synchronized_pool_resource may be accessed from multiple threads
without external synchronization
and may have thread-specific pools to reduce synchronization costs[.](#pool.overview-2.sentence-1)

An unsynchronized_pool_resource class may not be accessed
from multiple threads simultaneously
and thus avoids the cost of synchronization entirely
in single-threaded applications[.](#pool.overview-2.sentence-2)

[ð](#lib:pool_options)

namespace std::pmr {struct pool_options { size_t max_blocks_per_chunk = 0;
 size_t largest_required_pool_block = 0; }; class synchronized_pool_resource : public memory_resource {public: synchronized_pool_resource(const pool_options& opts, memory_resource* upstream);

 synchronized_pool_resource(): synchronized_pool_resource(pool_options(), get_default_resource()) {}explicit synchronized_pool_resource(memory_resource* upstream): synchronized_pool_resource(pool_options(), upstream) {}explicit synchronized_pool_resource(const pool_options& opts): synchronized_pool_resource(opts, get_default_resource()) {} synchronized_pool_resource(const synchronized_pool_resource&) = delete; virtual ~synchronized_pool_resource();

 synchronized_pool_resource& operator=(const synchronized_pool_resource&) = delete; void release();
 memory_resource* upstream_resource() const;
 pool_options options() const; protected:void* do_allocate(size_t bytes, size_t alignment) override; void do_deallocate(void* p, size_t bytes, size_t alignment) override; bool do_is_equal(const memory_resource& other) const noexcept override; }; class unsynchronized_pool_resource : public memory_resource {public: unsynchronized_pool_resource(const pool_options& opts, memory_resource* upstream);

 unsynchronized_pool_resource(): unsynchronized_pool_resource(pool_options(), get_default_resource()) {}explicit unsynchronized_pool_resource(memory_resource* upstream): unsynchronized_pool_resource(pool_options(), upstream) {}explicit unsynchronized_pool_resource(const pool_options& opts): unsynchronized_pool_resource(opts, get_default_resource()) {} unsynchronized_pool_resource(const unsynchronized_pool_resource&) = delete; virtual ~unsynchronized_pool_resource();

 unsynchronized_pool_resource& operator=(const unsynchronized_pool_resource&) = delete; void release();
 memory_resource* upstream_resource() const;
 pool_options options() const; protected:void* do_allocate(size_t bytes, size_t alignment) override; void do_deallocate(void* p, size_t bytes, size_t alignment) override; bool do_is_equal(const memory_resource& other) const noexcept override; };}

#### [20.5.5.2](#pool.options) pool_options data members [[mem.res.pool.options]](mem.res.pool.options)

[1](#pool.options-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8195)

The members of pool_options comprise a set of constructor options for pool resources[.](#pool.options-1.sentence-1)

The effect of each option on the pool resource behavior is described below:

[ð](#lib:pool_options,max_blocks_per_chunk)

`size_t max_blocks_per_chunk;
`

[2](#pool.options-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8206)

The maximum number of blocks that will be allocated at once
from the upstream memory resource ([[mem.res.monotonic.buffer]](#monotonic.buffer "20.5.6 Class monotonic_­buffer_­resource"))
to replenish a pool[.](#pool.options-2.sentence-1)

If the value of max_blocks_per_chunk is zero or
is greater than an implementation-defined
limit, that limit is used instead[.](#pool.options-2.sentence-2)

The implementation
may choose to use a smaller value than is specified in this member and
may use different values for different pools[.](#pool.options-2.sentence-3)

[ð](#lib:pool_options,largest_required_pool_block)

`size_t largest_required_pool_block;
`

[3](#pool.options-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8224)

The largest allocation size that is required to be fulfilled
using the pooling mechanism[.](#pool.options-3.sentence-1)

Attempts to allocate a single block larger than this threshold
will be allocated directly from the upstream memory resource[.](#pool.options-3.sentence-2)

If largest_required_pool_block is zero or
is greater than an implementation-defined
limit, that limit is used instead[.](#pool.options-3.sentence-3)

The implementation may choose a pass-through threshold
larger than specified in this member[.](#pool.options-3.sentence-4)

#### [20.5.5.3](#pool.ctor) Constructors and destructors [[mem.res.pool.ctor]](mem.res.pool.ctor)

[ð](#lib:synchronized_pool_resource,constructor)

`synchronized_pool_resource(const pool_options& opts, memory_resource* upstream);
unsynchronized_pool_resource(const pool_options& opts, memory_resource* upstream);
`

[1](#pool.ctor-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8246)

*Preconditions*: upstream is the address of a valid memory resource[.](#pool.ctor-1.sentence-1)

[2](#pool.ctor-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8250)

*Effects*: Constructs a pool resource object that will obtain memory from upstream whenever the pool resource is unable to satisfy a memory request
from its own internal data structures[.](#pool.ctor-2.sentence-1)

The resulting object will hold a copy of upstream,
but will not own the resource to which upstream points[.](#pool.ctor-2.sentence-2)

[*Note [1](#pool.ctor-note-1)*:

The intention is that calls to upstream->allocate() will be substantially fewer than calls to this->allocate() in most cases[.](#pool.ctor-2.sentence-3)

â *end note*]

The behavior of the pooling mechanism is tuned
according to the value of the opts argument[.](#pool.ctor-2.sentence-4)

[3](#pool.ctor-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8265)

*Throws*: Nothing unless upstream->allocate() throws[.](#pool.ctor-3.sentence-1)

It is unspecified if, or under what conditions,
this constructor calls upstream->allocate()[.](#pool.ctor-3.sentence-2)

[ð](#lib:synchronized_pool_resource,destructor)

`virtual ~synchronized_pool_resource();
virtual ~unsynchronized_pool_resource();
`

[4](#pool.ctor-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8280)

*Effects*: Calls release()[.](#pool.ctor-4.sentence-1)

#### [20.5.5.4](#pool.mem) Members [[mem.res.pool.mem]](mem.res.pool.mem)

[ð](#lib:release,synchronized_pool_resource)

`void release();
`

[1](#pool.mem-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8294)

*Effects*: Calls upstream_resource()->deallocate() as necessary
to release all allocated memory[.](#pool.mem-1.sentence-1)

[*Note [1](#pool.mem-note-1)*:

The memory is released back to upstream_resource() even if deallocate has not been called
for some of the allocated blocks[.](#pool.mem-1.sentence-2)

â *end note*]

[ð](#lib:upstream_resource,synchronized_pool_resource)

`memory_resource* upstream_resource() const;
`

[2](#pool.mem-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8312)

*Returns*: The value of the upstream argument
provided to the constructor of this object[.](#pool.mem-2.sentence-1)

[ð](#lib:options,synchronized_pool_resource)

`pool_options options() const;
`

[3](#pool.mem-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8325)

*Returns*: The options that control the pooling behavior of this resource[.](#pool.mem-3.sentence-1)

The values in the returned struct may differ
from those supplied to the pool resource constructor in that
values of zero will be replaced with implementation-defined
defaults, and sizes may be rounded to unspecified granularity[.](#pool.mem-3.sentence-2)

[ð](#lib:do_allocate,synchronized_pool_resource)

`void* do_allocate(size_t bytes, size_t alignment) override;
`

[4](#pool.mem-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8341)

*Effects*: If the pool selected for a block of size bytes is unable to satisfy the memory request from its own internal data structures,
it will call upstream_resource()->allocate() to obtain more memory[.](#pool.mem-4.sentence-1)

If bytes is larger than that which the largest pool can handle,
then memory will be allocated using upstream_resource()->allocate()[.](#pool.mem-4.sentence-2)

[5](#pool.mem-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8349)

*Returns*: A pointer to allocated storage ([[basic.stc.dynamic.allocation]](basic.stc.dynamic.allocation "6.8.6.5.2 Allocation functions"))
with a size of at least bytes[.](#pool.mem-5.sentence-1)

The size and alignment of the allocated memory shall meet the requirements
for a class derived from memory_resource ([[mem.res.class]](#class "20.5.2 Class memory_­resource"))[.](#pool.mem-5.sentence-2)

[6](#pool.mem-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8356)

*Throws*: Nothing unless upstream_resource()->allocate() throws[.](#pool.mem-6.sentence-1)

[ð](#lib:do_deallocate,synchronized_pool_resource)

`void do_deallocate(void* p, size_t bytes, size_t alignment) override;
`

[7](#pool.mem-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8368)

*Effects*: Returns the memory at p to the pool[.](#pool.mem-7.sentence-1)

It is unspecified if, or under what circumstances,
this operation will result in a call to upstream_resource()->deallocate()[.](#pool.mem-7.sentence-2)

[8](#pool.mem-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8374)

*Throws*: Nothing[.](#pool.mem-8.sentence-1)

[ð](#lib:do_is_equal,synchronized_pool_resource)

`bool do_is_equal(const memory_resource& other) const noexcept override;
`

[9](#pool.mem-9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8386)

*Returns*: this == &other[.](#pool.mem-9.sentence-1)

### [20.5.6](#monotonic.buffer) Class monotonic_buffer_resource [[mem.res.monotonic.buffer]](mem.res.monotonic.buffer)

#### [20.5.6.1](#monotonic.buffer.general) General [[mem.res.monotonic.buffer.general]](mem.res.monotonic.buffer.general)

[1](#monotonic.buffer.general-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8395)

A monotonic_buffer_resource is a special-purpose memory resource
intended for very fast memory allocations in situations
where memory is used to build up a few objects
and then is released all at once when the memory resource object is destroyed[.](#monotonic.buffer.general-1.sentence-1)

[ð](#lib:monotonic_buffer_resource)

namespace std::pmr {class monotonic_buffer_resource : public memory_resource { memory_resource* upstream_rsrc; // *exposition only*void* current_buffer; // *exposition only* size_t next_buffer_size; // *exposition only*public:explicit monotonic_buffer_resource(memory_resource* upstream);
 monotonic_buffer_resource(size_t initial_size, memory_resource* upstream);
 monotonic_buffer_resource(void* buffer, size_t buffer_size, memory_resource* upstream);

 monotonic_buffer_resource(): monotonic_buffer_resource(get_default_resource()) {}explicit monotonic_buffer_resource(size_t initial_size): monotonic_buffer_resource(initial_size, get_default_resource()) {} monotonic_buffer_resource(void* buffer, size_t buffer_size): monotonic_buffer_resource(buffer, buffer_size, get_default_resource()) {} monotonic_buffer_resource(const monotonic_buffer_resource&) = delete; virtual ~monotonic_buffer_resource();

 monotonic_buffer_resource& operator=(const monotonic_buffer_resource&) = delete; void release();
 memory_resource* upstream_resource() const; protected:void* do_allocate(size_t bytes, size_t alignment) override; void do_deallocate(void* p, size_t bytes, size_t alignment) override; bool do_is_equal(const memory_resource& other) const noexcept override; };}

#### [20.5.6.2](#monotonic.buffer.ctor) Constructors and destructor [[mem.res.monotonic.buffer.ctor]](mem.res.monotonic.buffer.ctor)

[ð](#lib:monotonic_buffer_resource,constructor)

`explicit monotonic_buffer_resource(memory_resource* upstream);
monotonic_buffer_resource(size_t initial_size, memory_resource* upstream);
`

[1](#monotonic.buffer.ctor-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8448)

*Preconditions*: upstream is the address of a valid memory resource[.](#monotonic.buffer.ctor-1.sentence-1)

initial_size, if specified, is greater than zero[.](#monotonic.buffer.ctor-1.sentence-2)

[2](#monotonic.buffer.ctor-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8453)

*Effects*: Sets upstream_rsrc to upstream andcurrent_buffer to nullptr[.](#monotonic.buffer.ctor-2.sentence-1)

If initial_size is specified,
sets next_buffer_size to at least initial_size;
otherwise sets next_buffer_size to animplementation-defined size[.](#monotonic.buffer.ctor-2.sentence-2)

[ð](#lib:monotonic_buffer_resource,constructor_)

`monotonic_buffer_resource(void* buffer, size_t buffer_size, memory_resource* upstream);
`

[3](#monotonic.buffer.ctor-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8469)

*Preconditions*: upstream is the address of a valid memory resource[.](#monotonic.buffer.ctor-3.sentence-1)

buffer_size is no larger than the number of bytes in buffer[.](#monotonic.buffer.ctor-3.sentence-2)

[4](#monotonic.buffer.ctor-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8474)

*Effects*: Sets upstream_rsrc to upstream,current_buffer to buffer, andnext_buffer_size to buffer_size (but not less than 1),
then increases next_buffer_size by an implementation-defined growth factor (which need not be integral)[.](#monotonic.buffer.ctor-4.sentence-1)

[ð](#lib:monotonic_buffer_resource,destructor)

`~monotonic_buffer_resource();
`

[5](#monotonic.buffer.ctor-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8489)

*Effects*: Calls release()[.](#monotonic.buffer.ctor-5.sentence-1)

#### [20.5.6.3](#monotonic.buffer.mem) Members [[mem.res.monotonic.buffer.mem]](mem.res.monotonic.buffer.mem)

[ð](#lib:release,monotonic_buffer_resource)

`void release();
`

[1](#monotonic.buffer.mem-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8503)

*Effects*: Calls upstream_rsrc->deallocate() as necessary
to release all allocated memory[.](#monotonic.buffer.mem-1.sentence-1)

Resets current_buffer and next_buffer_size to their initial values at construction[.](#monotonic.buffer.mem-1.sentence-2)

[2](#monotonic.buffer.mem-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8510)

[*Note [1](#monotonic.buffer.mem-note-1)*:

The memory is released back to upstream_rsrc even if some blocks that were allocated from *this have not been deallocated from *this[.](#monotonic.buffer.mem-2.sentence-1)

â *end note*]

[ð](#lib:upstream_resource,monotonic_buffer_resource)

`memory_resource* upstream_resource() const;
`

[3](#monotonic.buffer.mem-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8524)

*Returns*: The value of upstream_rsrc[.](#monotonic.buffer.mem-3.sentence-1)

[ð](#lib:do_allocate,monotonic_buffer_resource)

`void* do_allocate(size_t bytes, size_t alignment) override;
`

[4](#monotonic.buffer.mem-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8535)

*Effects*: If the unused space in current_buffer can fit a block with the specified bytes and alignment,
then allocate the return block from current_buffer;
otherwise set current_buffer to upstream_rsrc->allocate(n, m),
where n is not less than max(bytes, next_buffer_size) andm is not less than alignment,
and increase next_buffer_size by an implementation-defined growth factor (which need not be integral),
then allocate the return block from the newly-allocated current_buffer[.](#monotonic.buffer.mem-4.sentence-1)

[5](#monotonic.buffer.mem-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8547)

*Returns*: A pointer to allocated storage ([[basic.stc.dynamic.allocation]](basic.stc.dynamic.allocation "6.8.6.5.2 Allocation functions"))
with a size of at least bytes[.](#monotonic.buffer.mem-5.sentence-1)

The size and alignment of the allocated memory shall meet the requirements
for a class derived from memory_resource ([[mem.res.class]](#class "20.5.2 Class memory_­resource"))[.](#monotonic.buffer.mem-5.sentence-2)

[6](#monotonic.buffer.mem-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8554)

*Throws*: Nothing unless upstream_rsrc->allocate() throws[.](#monotonic.buffer.mem-6.sentence-1)

[ð](#lib:do_deallocate,monotonic_buffer_resource)

`void do_deallocate(void* p, size_t bytes, size_t alignment) override;
`

[7](#monotonic.buffer.mem-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8565)

*Effects*: None[.](#monotonic.buffer.mem-7.sentence-1)

[8](#monotonic.buffer.mem-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8569)

*Throws*: Nothing[.](#monotonic.buffer.mem-8.sentence-1)

[9](#monotonic.buffer.mem-9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8573)

*Remarks*: Memory used by this resource increases monotonically until its destruction[.](#monotonic.buffer.mem-9.sentence-1)

[ð](#lib:do_is_equal,monotonic_buffer_resource)

`bool do_is_equal(const memory_resource& other) const noexcept override;
`

[10](#monotonic.buffer.mem-10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L8584)

*Returns*: this == &other[.](#monotonic.buffer.mem-10.sentence-1)
