Home Original page

std::raw_storage_iterator - cppreference.com

From cppreference.com

Defined in header <memory>

template< class OutputIt, class T > class raw_storage_iterator : public std::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 iterator std::raw_storage_iterator makes it possible for standard algorithms to store results in uninitialized memory. Whenever the algorithm writes an object of type T to the dereferenced iterator, the object is copy-constructed into the location in the uninitialized storage pointed to by the iterator. The template parameter OutputIt is any type that meets the requirements of LegacyOutputIterator and has operator* defined to return an object, for which operator& returns an object of type T*. Usually, the type T* is used as OutputIt.

Type requirements

Member functions

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 types iterator_category, value_type, difference_type, pointer and reference are required to be obtained by inheriting from std::iterator<std::output_iterator_tag, void, void, void, void>.

(until C++17)

Note

std::raw_storage_iterator was deprecated primarily because of its exception-unsafe behavior. Unlike std::uninitialized_copy, it doesn't handle exceptions during operations like std::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.

Example

#include <algorithm>
#include <iostream>
#include <memory>
#include <string>

int main()
{
    const std::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:

See also