std::destroy (3) - Linux Manuals

std::destroy: std::destroy

NAME

std::destroy - std::destroy

Synopsis

Defined in header <memory>
template< class ForwardIt > (1) (since C++17)
void destroy( ForwardIt first, ForwardIt last );
template< class ExecutionPolicy, class ForwardIt > (2) (since C++17)
void destroy( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last );

1) Destroys the objects in the range [first, last), as if by

  for (; first != last; ++first)
    std::destroy_at(std::addressof(*first));

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.

Parameters

first, last - the range 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

(none)

Complexity

Linear in the distance between first and last.

Exceptions

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 >
  void destroy( ForwardIt first, ForwardIt last )
  {
    for (; first != last; ++first)
      std::destroy_at(std::addressof(*first));
  }

Example

The following example demonstrates how to use destroy 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(ptr, ptr + 8);

  }

Output:

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