std::raw_storage_iterator

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Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros(C++20)
Language support library
Concepts library(C++20)
Diagnostics library
Memory management library
Metaprogramming library(C++11)
General utilities library
Containers library
Iterators library
Ranges library(C++20)
Algorithms library
Strings library
Text processing library
Numerics library
Date and time library
Input/output library
Filesystem library(C++17)
Concurrency support library(C++11)
Execution control library(C++26)
Technical specifications
Symbols index
External libraries

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Memory management library

voidify

(exposition only*)

Allocators

allocator
allocator_traits (C++11)
allocation_result (C++23)
scoped_allocator_adaptor (C++11)
pmr::polymorphic_allocator (C++17)

allocator_arg (C++11)
uses_allocator (C++11)
uses_allocator_construction_args (C++20)
make_obj_using_allocator (C++20)
uninitialized_construct_using_allocator (C++20)

Uninitialized memory algorithms

uninitialized_copy
uninitialized_fill
uninitialized_move (C++17)
uninitialized_copy_n (C++11)
uninitialized_fill_n
uninitialized_move_n (C++17)
construct_at (C++20)

uninitialized_default_construct (C++17)
uninitialized_value_construct (C++17)
destroy (C++17)
uninitialized_default_construct_n (C++17)
uninitialized_value_construct_n (C++17)
destroy_n (C++17)
destroy_at (C++17)

Constrained uninitialized memory algorithms

ranges::uninitialized_copy (C++20)
ranges::uninitialized_fill (C++20)
ranges::uninitialized_move (C++20)
ranges::uninitialized_copy_n (C++20)
ranges::uninitialized_fill_n (C++20)
ranges::uninitialized_move_n (C++20)
ranges::construct_at (C++20)

ranges::uninitialized_default_construct (C++20)
ranges::uninitialized_value_construct (C++20)
ranges::destroy (C++20)
ranges::uninitialized_default_construct_n (C++20)
ranges::uninitialized_value_construct_n (C++20)
ranges::destroy_n (C++20)
ranges::destroy_at (C++20)

Memory resources

pmr::memory_resource (C++17)
pmr::get_default_resource (C++17)
pmr::set_default_resource (C++17)
pmr::new_delete_resource (C++17)
pmr::pool_options (C++17)

pmr::null_memory_resource (C++17)
pmr::synchronized_pool_resource (C++17)
pmr::unsynchronized_pool_resource (C++17)
pmr::monotonic_buffer_resource (C++17)

Explicit lifetime management
start_lifetime_as (C++23)
start_lifetime_as_array (C++23)

Types for composite class design
indirect (C++26)
polymorphic (C++26)

Uninitialized storage(until C++20)

raw_storage_iterator (until C++20*)
get_temporary_buffer (until C++20*)

return_temporary_buffer (until C++20*)

Garbage collector support(until C++23)

declare_reachable (C++11)(until C++23)
declare_no_pointers (C++11)(until C++23)
pointer_safety (C++11)(until C++23)

undeclare_reachable (C++11)(until C++23)
undeclare_no_pointers (C++11)(until C++23)
get_pointer_safety (C++11)(until C++23)

Low level memory
management

operator newoperator new[]

operator deleteoperator delete[]

(C++11)

(C++11)

(C++17)

(C++20)

(C++17)

(C++11)

(C++11)

(C++11)

(until C++17*)

(C++11)

(C++17)

(C++26)

(C++26)

enable_shared_from_this

(C++11)

(C++11)

(C++11)

(C++23)

(C++23)

(C++11)

(C++20)

(C++11)

(C++11)

(C++20)

is_sufficiently_aligned

(C++26)

C Library

malloc
calloc
realloc

free
aligned_alloc (C++17)

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std::raw_storage_iterator

Member functions
raw_storage_iterator::raw_storage_iterator
raw_storage_iterator::operator=
raw_storage_iterator::operator*
raw_storage_iterator::base (C++17)
raw_storage_iterator::operator++raw_storage_iterator::operator++(int)

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Defined in header`<memory>`
template<class OutputIt,class T> class raw_storage_iterator :publicstd::iterator<std::output_iterator_tag,void,void,void,void>;		(until C++17)
template<class OutputIt,class T> class raw_storage_iterator;		(since C++17) (deprecated in C++17) (removed in C++20)

The output iteratorstd::raw_storage_iterator makes it possible for standard algorithms to store results in uninitialized memory. Whenever the algorithm writes an object of typeT to the dereferenced iterator, the object is copy-constructed into the location in the uninitialized storage pointed to by the iterator. The template parameterOutputIt is any type that meets the requirements ofLegacyOutputIterator and hasoperator* defined to return an object, for whichoperator& returns an object of typeT*. Usually, the typeT* is used asOutputIt.

[edit]Type requirements

OutputIt must meet the requirements ofLegacyOutputIterator.

[edit]Member functions

(constructor)	creates a new`raw_storage_iterator` (public member function)[edit]
operator=	constructs an object at the pointed-to location in the buffer (public member function)[edit]
operator*	dereferences the iterator (public member function)[edit]
operator++operator++(int)	advances the iterator (public member function)[edit]
base (since C++17)	provides access to the wrapped iterator (public member function)[edit]

[edit]Member types

Member type Definition

iterator_category std::output_iterator_tag

value_type void

difference_type

void	(until C++20)
std::ptrdiff_t	(since C++20)

pointer void

reference void

Member typesiterator_category,value_type,difference_type,pointer andreference are required to be obtained by inheriting fromstd::iterator<std::output_iterator_tag,void,void,void,void>.

(until C++17)

[edit]Note

std::raw_storage_iterator was deprecated primarily because of its exception-unsafe behavior. Unlikestd::uninitialized_copy, it doesn't handle exceptions during operations likestd::copy safely, potentially leading to resource leaks due to a lack of tracking the number of successfully constructed objects and their proper destruction in the presence of exceptions.

[edit]Example

Run this code

#include <algorithm>#include <iostream>#include <memory>#include <string> int main(){conststd::string s[]={"This","is","a","test","."};std::string* p=std::allocator<std::string>().allocate(5); std::copy(std::begin(s),std::end(s),              std::raw_storage_iterator<std::string*,std::string>(p)); for(std::string* i= p; i!= p+5;++i){std::cout<<*i<<'\n';        i->~basic_string<char>();}std::allocator<std::string>().deallocate(p,5);}

Output:

Thisisatest.

[edit]See also

allocator_traits (C++11)	provides information about allocator types (class template)[edit]
scoped_allocator_adaptor (C++11)	implements multi-level allocator for multi-level containers (class template)[edit]
uses_allocator (C++11)	checks if the specified type supports uses-allocator construction (class template)[edit]