std::destroy_at

 

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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

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.

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

The following example demonstrates how to use destroy_at 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));
 
    for (int i = 0; i < 8; ++i)
        std::destroy_at(ptr + i);
}

Output:

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

See also

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