std::destroy

Defined in header `<memory>`
	(1)
template< class ForwardIt > void destroy( ForwardIt first, ForwardIt last );		(since C++17) (until C++20)
template< class ForwardIt > constexpr void destroy( ForwardIt first, ForwardIt last );		(since C++20)
template< class ExecutionPolicy, class ForwardIt > void destroy( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last );	(2)	(since C++17)

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`.	(until C++20)
`std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>` is `true`.	(since C++20)

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>
constexpr // since C++20
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.

#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

destroy_n (C++17)	destroys a number of objects in a range (function template)
destroy_at (C++17)	destroys an object at a given address (function template)
ranges::destroy (C++20)	destroys a range of objects (niebloid)