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std::ranges::destroy

Defined in header <memory>

Call signature

Defined in header `<memory>`
Call signature
template< no-throw-input-iterator I, no-throw-sentinel-for<I> S > requires std::destructible<std::iter_value_t<I>> constexpr I destroy( I first, S last ) noexcept;	(1)	(since C++20)
template< no-throw-input-range R > requires std::destructible<ranges::range_value_t<R>> constexpr ranges::borrowed_iterator_t<R> destroy( R&& r ) noexcept;	(2)	(since C++20)

template< no-throw-input-iterator I, no-throw-sentinel-for<I> S >
    requires std::destructible<std::iter_value_t<I>>
constexpr I destroy( I first, S last ) noexcept;

(1)

(since C++20)

template< no-throw-input-range R >
    requires std::destructible<ranges::range_value_t<R>>
constexpr ranges::borrowed_iterator_t<R> destroy( R&& r ) noexcept;

(2)

(since C++20)

1) Destroys the objects in the range [first, last), as if by

for (; first != last; ++first)
    std::ranges::destroy_at(std::addressof(*first));
return first;

2) Same as (1), but uses r as the source range, as if using ranges::begin(r) as first and ranges::end(r) as last.

The function-like entities described on this page are 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.

In practice, they may be implemented as function objects, or with special compiler extensions.

Parameters

first, last	-	iterator-sentinel pair denoting the range of elements to destroy
r	-	the range to destroy

Return value

An iterator compares equal to last.

Complexity

Linear in the distance between first and last.

Possible implementation

struct destroy_fn
{
    template<no-throw-input-iterator I, no-throw-sentinel-for<I> S>
        requires std::destructible<std::iter_value_t<I>>
    constexpr I operator()(I first, S last) const noexcept
    {
        for (; first != last; ++first)
            std::ranges::destroy_at(std::addressof(*first));
        return first;
    }
 
    template<no-throw-input-range R>
        requires std::destructible<std::ranges::range_value_t<R>>
    constexpr std::ranges::borrowed_iterator_t<R> operator()(R&& r) const noexcept
    {
        return operator()(std::ranges::begin(r), std::ranges::end(r));
    }
};
 
inline constexpr destroy_fn destroy{};

Example

The following example demonstrates how to use ranges::destroy 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));
 
    std::ranges::destroy(ptr, ptr + 8);
}

Output:

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