# Dynamic memory management

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< cpp

### Smart pointers

Smart pointers enable automatic, exception-safe, object lifetime management.

Defined in header `<memory>`

##### Pointer categories

unique_ptr (C++11) | smart pointer with unique object ownership semantics (class template)
shared_ptr (C++11) | smart pointer with shared object ownership semantics (class template)
weak_ptr (C++11) | weak reference to an object managed by std::shared_ptr (class template)
auto_ptr (until C++17) | smart pointer with strict object ownership semantics (class template)

##### Helper classes

owner_less (C++11) | provides mixed-type owner-based ordering of shared and weak pointers (class template)
enable_shared_from_this (C++11) | allows an object to create a `shared_ptr` referring to itself (class template)
bad_weak_ptr (C++11) | exception thrown when accessing a `weak_ptr` which refers to already destroyed object (class)
default_delete (C++11) | default deleter for `unique_ptr` (class template)

### Allocators

Allocators are class templates encapsulating memory allocation strategy. This allows generic containers to decouple memory management from the data itself.

Defined in header `<memory>`
allocator | the default allocator (class template)
allocator_traits (C++11) | provides information about allocator types (class template)
allocator_arg_t (C++11) | tag type used to select allocator-aware constructor overloads (class)
allocator_arg (C++11) | an object of type std::allocator_arg_t used to select allocator-aware constructors (constant)
uses_allocator (C++11) | checks if the specified type supports uses-allocator construction (class template)
Defined in header `<scoped_allocator>`
scoped_allocator_adaptor (C++11) | implements multi-level allocator for multi-level containers (class template)
Defined in header `<memory_resource>`
Defined in namespace `pmr`
polymorphic_allocator (C++17) | an allocator that supports run-time polymorphism based on the std::memory_resource it is constructed with (class template)

### Memory resources

Memory resources implement memory allocation strategies that can be used by std::pmr::polymorphic_allocator

Defined in header `<memory_resource>`
Defined in namespace `pmr`
memory_resource (C++17) | an abstract interface for classes that encapsulate memory resources (class)
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)
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)

### Uninitialized storage

Several utilities are provided to create and access raw storage

Defined in header `<memory>`
uninitialized_copy | copies a range of objects to an uninitialized area of memory (function template)
uninitialized_copy_n (C++11) | copies a number of objects to an uninitialized area of memory (function template)
uninitialized_fill | copies an object to an uninitialized area of memory, defined by a range (function template)
uninitialized_fill_n | copies an object to an uninitialized area of memory, defined by a start and a count (function template)
uninitialized_move (C++17) | moves a range of objects to an uninitialized area of memory (function template)
uninitialized_move_n (C++17) | moves a number of objects to an uninitialized area of memory (function template)
uninitialized_default_construct (C++17) | constructs objects by default-initialization in an uninitialized area of memory, defined by a range (function template)
uninitialized_default_construct_n (C++17) | constructs objects by default-initialization in an uninitialized area of memory, defined by a start and a count (function template)
uninitialized_value_construct (C++17) | constructs objects by value-initialization in an uninitialized area of memory, defined by a range (function template)
uninitialized_value_construct_n (C++17) | constructs objects by value-initialization in an uninitialized area of memory, defined by a start and a count (function template)
destroy_at (C++17) | destroys an object at a given address (function template)
destroy (C++17) | destroys a range of objects (function template)
destroy_n (C++17) | destroys a number of objects in a range (function template)
raw_storage_iterator (deprecated in C++17) | an iterator that allows standard algorithms to store results in uninitialized memory (class template)
get_temporary_buffer (deprecated in C++17) | obtains uninitialized storage (function template)
return_temporary_buffer (deprecated in C++17) | frees uninitialized storage (function template)

### Garbage collector support

Defined in header `<memory>`
declare_reachable (C++11) | declares that an object can not be recycled (function)
undeclare_reachable (C++11) | declares that an object can be recycled (function template)
declare_no_pointers (C++11) | declares that a memory area does not contain traceable pointers (function)
undeclare_no_pointers (C++11) | cancels the effect of std::declare_no_pointers (function)
pointer_safety (C++11) | lists pointer safety models (class)
get_pointer_safety (C++11) | returns the current pointer safety model (function)

### Miscellaneous

Defined in header `<memory>`
pointer_traits (C++11) | provides information about pointer-like types (class template)
addressof (C++11) | obtains actual address of an object, even if the & operator is overloaded (function template)
align (C++11) | aligns a pointer in a buffer (function)

### C-style memory management

Includes e.g. std::malloc, std::free

### Low level memory management

Includes e.g. `operator new` , `operator delete` , std::set_new_handler

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