# std::ranges::destroy_at

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< cpp‎ | memory

Defined in header `<memory>` |  |
Call signature |  |
template< std::destructible T > constexpr void destroy_at( T* p ) noexcept; |  | (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()`. Otherwise, recursively destroys elements of *p in order, as if by calling std::destroy ( std::begin (*p), std::end (*p)).

The function-like entities described on this page are algorithm function objects (informally known as niebloids), that is:

- Explicit template argument lists cannot be specified when calling any of them.
- None of them are visible to argument-dependent lookup.
- When any of them are found by normal unqualified lookup as the name to the left of the function-call operator, argument-dependent lookup is inhibited.

### Parameters

p | - | a pointer to the object to be destroyed

### Return value

(none)

### Possible implementation

    struct destroy_at_fn
    {
        template<std::destructible T>
        constexpr void operator()(T *p) const noexcept
        {
            if constexpr (std::is_array_v<T>)
                for (auto &elem : *p)
                    operator()(std::addressof(elem));
            else
                p->~T();
        }
    };

    inline constexpr destroy_at_fn destroy_at{};

### 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.

### Example

The following example demonstrates how to use `ranges::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::ranges::destroy_at(ptr + i);
    }

Output:

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

### See also

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

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