std:: destroy_at

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

Return value

(none)

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.

Example

The following 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) * 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));
 
    for (int i = 0; i < 8; ++i)
        std::destroy_at(ptr + i);
}

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

See also