std::destroy_n (3) - Linux Manuals

std::destroy_n: std::destroy_n


std::destroy_n - std::destroy_n


Defined in header <memory>
template< class ForwardIt, class Size > (1) (since C++17)
ForwardIt destroy_n( ForwardIt first, Size n );
template< class ExecutionPolicy, class ForwardIt, class Size > (2) (since C++17)
ForwardIt destroy_n( ExecutionPolicy&& policy, ForwardIt first, Size n );

1) Destroys the n objects in the range starting at first, as if by

  for (; n > 0; (void) ++first, --n)

2) Same as (1), but executed according to policy. This overload does not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true


first - the beginning of the range of elements to destroy
n - the number of elements to destroy
policy - the execution policy to use. See execution_policy for details.

Type requirements

ForwardIt must meet the requirements of LegacyForwardIterator.
No increment, assignment, comparison, or indirection through valid instances of ForwardIt may throw exceptions.

Return value

The end of the range of objects that has been destroyed (i.e., std::next(first, n)).


Linear in n.


The overload with a template parameter named ExecutionPolicy reports errors as follows:

* If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard_policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
* If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation

  template<class ForwardIt, class Size>
  ForwardIt destroy_n( ForwardIt first, Size n )
    for (; n > 0; (void) ++first, --n)
    return first;


The following example demonstrates how to use destroy_n to destroy a contiguous sequence of elements.
// Run this code

  #include <memory>
  #include <new>
  #include <iostream>

  struct Tracer {
      int value;
      ~Tracer() { std::cout << value << " destructed\n"; }

  int main()
      alignas(Tracer) unsigned char buffer[sizeof(Tracer) * 8];

      for (int i = 0; i < 8; ++i)
          new(buffer + sizeof(Tracer) * i) Tracer{i}; //manually construct objects

      auto ptr = std::launder(reinterpret_cast<Tracer*>(buffer));

      std::destroy_n(ptr, 8);



  0 destructed
  1 destructed
  2 destructed
  3 destructed
  4 destructed
  5 destructed
  6 destructed
  7 destructed

See also

destroy destroys a range of objects
           (function template)

destroy_at destroys an object at a given address
           (function template)