Call signature
(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:
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{};[edit] 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.
The following example demonstrates how to use ranges::destroy_at 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));
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[edit] See also
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