Standard library header <memory_resource> (C++17)

 

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Language support <cfloat> <climits> <compare> (C++20) <coroutine> (C++20) <csetjmp> <csignal> <cstdarg> <cstddef> <cstdint> (C++11) <cstdlib> <exception> <initializer_list> (C++11)    <limits> <new> <source_location> (C++20) <stdfloat> (C++23) <typeinfo> <version> (C++20) Concepts <concepts> (C++20) Diagnostics <cassert> <cerrno> <debugging> (C++26) <stacktrace> (C++23) <stdexcept> <system_error> (C++11) Memory management <memory> <memory_resource> (C++17) <scoped_allocator> (C++11) Metaprogramming <type_traits> (C++11) <ratio> (C++11)

General utilities <any> (C++17) <bitset> <bit> (C++20) <charconv> (C++17) <expected> (C++23) <format> (C++20) <functional> <optional> (C++17) <tuple> (C++11) <typeindex> (C++11) <utility> <variant> (C++17) Containers <array> (C++11) <deque> <flat_map> (C++23) <flat_set> (C++23) <forward_list> (C++11) <inplace_vector> (C++26)    <list> <map> <mdspan> (C++23) <queue> <set> <span> (C++20) <stack> <unordered_map> (C++11) <unordered_set> (C++11) <vector> Iterators <iterator> Ranges <generator> (C++23) <ranges> (C++20)

Algorithms <algorithm> <numeric> Strings <cctype> <cstring> <cuchar> (C++11) <cwchar> <cwctype> <string_view> (C++17) <string> Text processing <clocale> <codecvt> (C++11/17/26*) <locale> <regex> (C++11) <text_encoding> (C++26)    Numerics <cfenv> (C++11) <cmath> <complex> <linalg> (C++26) <numbers> (C++20) <random> (C++11) <valarray> Time <chrono> (C++11) <ctime> C compatibility <ccomplex> (C++11/17/20*) <ciso646> (until C++20) <cstdalign> (C++11/17/20*) <cstdbool> (C++11/17/20*) <ctgmath> (C++11/17/20*)

Input/output <cinttypes> (C++11) <cstdio> <filesystem> (C++17) <fstream> <iomanip> <iosfwd> <iostream> <ios> <istream> <ostream> <print> (C++23) <spanstream> (C++23) <sstream> <streambuf> <strstream> (C++98/26*) <syncstream> (C++20) Concurrency support <atomic> (C++11) <barrier> (C++20) <condition_variable> (C++11) <future> (C++11) <hazard_pointer> (C++26) <latch> (C++20) <mutex> (C++11) <rcu> (C++26) <semaphore> (C++20) <shared_mutex> (C++14) <stdatomic.h> (C++23) <stop_token> (C++20) <thread> (C++11) Execution support <execution> (C++17)

 

Classes
Defined in namespace std::pmr
polymorphic_allocator (C++17)	an allocator that supports run-time polymorphism based on the std::pmr::memory_resource it is constructed with (class template)
memory_resource (C++17)	an abstract interface for classes that encapsulate memory resources (class)
pool_options (C++17)	a set of constructor options for pool resources (class)
synchronized_pool_resource (C++17)	a thread-safe std::pmr::memory_resource for managing allocations in pools of different block sizes (class)
unsynchronized_pool_resource (C++17)	a thread-unsafe std::pmr::memory_resource for managing allocations in pools of different block sizes (class)
monotonic_buffer_resource (C++17)	a special-purpose std::pmr::memory_resource that releases the allocated memory only when the resource is destroyed (class)
Functions
Defined in namespace std::pmr
new_delete_resource (C++17)	returns a static program-wide std::pmr::memory_resource that uses the global operator new and operator delete to allocate and deallocate memory (function)
null_memory_resource (C++17)	returns a static std::pmr::memory_resource that performs no allocation (function)
get_default_resource (C++17)	gets the default std::pmr::memory_resource (function)
set_default_resource (C++17)	sets the default std::pmr::memory_resource (function)

Synopsis

namespace std::pmr {
  // class memory_resource
  class memory_resource;
 
  bool operator==(const memory_resource& a, const memory_resource& b) noexcept;
 
  // class template polymorphic_allocator
  template<class Tp> class polymorphic_allocator;
 
  template<class T1, class T2>
    bool operator==(const polymorphic_allocator<T1>& a,
                    const polymorphic_allocator<T2>& b) noexcept;
 
  // 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;
 
  // pool resource classes
  struct pool_options;
  class synchronized_pool_resource;
  class unsynchronized_pool_resource;
  class monotonic_buffer_resource;
}

Class std::pmr::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;
  };
}

Class template std::pmr::polymorphic_allocator

namespace std::pmr {
  template<class Tp = byte> class polymorphic_allocator {
    memory_resource* memory_rsrc;       // exposition only
 
  public:
    using value_type = Tp;
 
    // 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;
 
    // 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); // deprecated
 
    polymorphic_allocator select_on_container_copy_construction() const;
 
    memory_resource* resource() const;
  };
}

Class std::pmr::pool_options

namespace std::pmr {
  struct pool_options {
    size_t max_blocks_per_chunk = 0;
    size_t largest_required_pool_block = 0;
  };
}

Class std::pmr::synchronized_pool_resource

namespace std::pmr {
  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 std::pmr::unsynchronized_pool_resource

namespace std::pmr {
  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;
  };
}

Class std::pmr::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;
  };
}