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

 

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Standard library headers

Language support
<cstddef> <cstdlib> <version> (C++20) <limits> <climits>	<cfloat> <cstdint> (C++11) <stdfloat> (C++23) <new> <typeinfo>	<source_location> (C++20) <exception> <initializer_list> (C++11) <compare> (C++20)	<coroutine> (C++20) <csignal> <csetjmp> <cstdarg>
Concepts
<concepts> (C++20)
Diagnostics
<stdexcept> <stacktrace> (C++23)	<cassert>	<cerrno>	<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
<utility> <tuple> (C++11) <optional> (C++17) <variant> (C++17)	<any> (C++17) <expected> (C++23) <bitset>	<functional> <typeindex> (C++11) <execution> (C++17)	<charconv> (C++17) <format> (C++20) <bit> (C++20)
Strings
<string_view> (C++17) <string>	<cctype> <cwctype>	<cstring> <cwchar>	<cuchar> (C++11)
Containers
<array> (C++11) <deque> <forward_list> (C++11) <list>	<vector> <map> <set> <unordered_map> (C++11)	<unordered_set> (C++11) <queue> <stack> <flat_map> (C++23)	<flat_set> (C++23) <span> (C++20) <mdspan> (C++23)
Iterators
<iterator>
Ranges
<ranges> (C++20)	<generator> (C++23)
Algorithms
<algorithm>	<numeric>
Numerics
<cfenv> (C++11) <complex>	<random> (C++11) <valarray>	<cmath>	<numbers> (C++20)
Time
<chrono> (C++11)	<ctime>
Localization
<locale>	<clocale>	<codecvt> (C++11/17*)
Input/output
<iosfwd> <iostream> <ios> <streambuf>	<istream> <ostream> <iomanip> <print> (C++23)	<sstream> <spanstream> (C++23) <fstream> <syncstream> (C++20)	<filesystem> (C++17) <cstdio> <cinttypes> (C++11) <strstream> (C++98*)
Regular expressions
<regex> (C++11)
Concurrency support
<stop_token> (C++20) <thread> (C++11) <atomic> (C++11)	<stdatomic.h> (C++23) <mutex> (C++11) <shared_mutex> (C++14)	<condition_variable> (C++11)   <semaphore> (C++20) <latch> (C++20)	<barrier> (C++20) <future> (C++11)
C compatibility
<cstdbool> (C++11/17/20*)   <ccomplex> (C++11/17/20*)	<ctgmath> (C++11/17/20*)	<cstdalign> (C++11/17/20*)	<ciso646> (until C++20)

 

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;
 
    [[nodiscard]] 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
    [[nodiscard]] Tp* allocate(size_t n);
    void deallocate(Tp* p, size_t n);
 
    [[nodiscard]] 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> [[nodiscard]] T* allocate_object(size_t n = 1);
    template<class T> void deallocate_object(T* p, size_t n = 1);
    template<class T, class... CtorArgs>
      [[nodiscard]] 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;
  };
}