# std::destroy_at

From cppreference.com
< cpp‎ | memory

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 <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);
    }

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 (algorithm function object)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/memory/destroy_at&oldid=153304"