Difference between revisions of "cpp/memory/destroy at"
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Revision as of 22:02, 6 February 2020
| Defined in header <memory>
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||
template< class T > void destroy_at( T* p ); |
(since C++17) (until C++20) |
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| 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).
Contents |
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.
|
While called in the evaluation of some expression e, |
(since C++20) |
Example
The following example demonstrates how to use 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::destroy_at(ptr + i); }
Output:
0 destructed 1 destructed 2 destructed 3 destructed 4 destructed 5 destructed 6 destructed 7 destructed
See also
| (C++17) |
destroys a range of objects (function template) |
| (C++17) |
destroys a number of objects in a range (function template) |
| (C++20) |
creates an object at a given address (function template) |
