std::destroy() algorithm

od C++17

// (1)
template< class ForwardIt >
void destroy( ForwardIt first, ForwardIt last );

// (2)
template< class ExecutionPolicy, class ForwardIt >
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.

Overload Resolution

These overloads participate in overload resolution only if std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>  (do C++20) std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>  (od C++20) 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

LegacyForwardIterator

No increment, assignment, comparison, or indirection through valid instances of NoThrowForwardIt may throw exceptions.

Return value

(none)

Complexity

Linear in the distance between first and last.

Exceptions

The overloads with a template parameter named ExecutionPolicy report 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 none other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation

destroy(1)

template<class ForwardIt>
constexpr // since C++20
void destroy(ForwardIt first, ForwardIt last)
{
    for (; first != last; ++first)
        std::destroy_at(std::addressof(*first));
}

Examples

Main.cpp

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

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