std::destroy_at - cppreference.com (original) (raw)
| | | | | ----------------------------------------------- | | ------------------------------------- | | template< class T > void destroy_at( T* p ); | | (since C++17) (constexpr 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).
[edit] Parameters
| p | - | a pointer to the object to be destroyed |
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[edit] Possible implementation
template constexpr void destroy_at(T* p) { if constexpr (std::is_array_v) for (auto& elem : p) (destroy_at)(std::addressof(elem)); else p->~T(); } // C++17 version: // template void destroy_at(T p) { p->~T(); }
[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. | (since C++20) |
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[edit] Example
The following example demonstrates how to use destroy_at to destroy a contiguous sequence of elements.
#include #include #include 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