NAME¶

std::ranges::destroy - std::ranges::destroy

Synopsis¶

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>> (1) (since C++20)

constexpr I destroy( I first, S last ) noexcept;
template< no-throw-input-range R >

requires std::destructible<ranges::range_value_t<R>> (2) (since C++20)

constexpr ranges::borrowed_iterator_t<R> destroy( R&& r )
noexcept;

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.

// 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));

std::ranges::destroy(ptr, ptr + 8);
}

Output:¶

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

See also¶

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