std::destroy_n - cppreference.com (original) (raw)

1. Destroys the n objects in the range starting at first, as if by

2. Same as (1), but executed according to policy. This overload participates in overload resolution only if all following conditions are satisfied:

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Exceptions
• 5 Possible implementation
• 6 Example
• 7 See also

[edit] Parameters

[edit] Return value

The end of the range of objects that has been destroyed (i.e., std::next(first, n)).

[edit] Complexity

Linear in n.

[edit] Exceptions

The overload with a template parameter named ExecutionPolicy reports errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

[edit] Possible implementation

template<class ForwardIt, class Size> constexpr // since C++20 ForwardIt destroy_n(ForwardIt first, Size n) { for (; n > 0; (void) ++first, --n) std::destroy_at(std::addressof(*first)); return first; }

[edit] Example

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

Output:

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

[edit] See also