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std::destroy_at - cppreference.com

From cppreference.com

Defined in header <memory> 

template< class T >
void destroy_at( T* p );
(since C++17)
(until C++20)		 
template< class T >
constexpr void destroy_at( T* p );
(since C++20)

If T is not an array type, calls the destructor of the object pointed to by p, as if by p->~T().

If T is an array type, the program is ill-formed(until C++20)recursively destroys elements of *p in order, as if by calling std::destroy(std::begin(*p), std::end(*p))(since C++20).

Parameters

p - a pointer to the object to be destroyed

Possible implementation

template<class T>
constexpr void destroy_at(T* p) 
{
    if constexpr (std::is_array_v<T>)
        for (auto &elem : *p)
            (destroy_at)(std::addressof(elem));
    else
        p->~T(); 
}
// C++17 version:
// template<class T> void destroy_at(T* p) { p->~T(); }

Notes

destroy_at deduces the type of object to be destroyed and hence avoids writing it explicitly in the destructor call.

When destroy_at is called in the evaluation of some constant expression e, the argument p must point to an object whose lifetime began within the evaluation of e.

(since C++20)

Example

Demonstrates how to use destroy_at 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) * 4];
    
    for (int i = 0; i < 4; ++i)
        new (buffer + sizeof(Tracer) * i) Tracer{i}; // manually construct objects

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

    for (int i = 0; i < 4; ++i)
        std::destroy_at(ptr + i);
}

Output: 

0 destructed
1 destructed
2 destructed
3 destructed

See also

(C++17)

 destroys a range of objects
(function template & algorithm function object)[edit]

(C++17)

 destroys a number of objects in a range
(function template & algorithm function object)[edit]
creates an object at a given address
(function template & algorithm function object)[edit]
destroys an object at a given address
(algorithm function object)[edit]