std::destroy
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Defined in header
<memory>
template< class ForwardIt >
void destroy( ForwardIt first, ForwardIt last );
(1)
(since C++17) void destroy( ForwardIt first, ForwardIt last );
(constexpr since C++20)
template< class ExecutionPolicy, class ForwardIt >
void destroy( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last );
(2)
(since C++17)
void destroy( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last );
1) Destroys the objects in the range
[first, last), as if by
for (; first != last; ++first) std::destroy_at (std::addressof (*first));
2) Same as (1), but executed according to policy. This overload participates in overload resolution only if all following conditions are satisfied:
std::is_execution_policy_v <std::decay_t <ExecutionPolicy>> is true.
(until C++20)std::is_execution_policy_v <std::remove_cvref_t <ExecutionPolicy>> is true.
(since C++20)[edit] Parameters
first, last
-
the pair of iterators defining the range of elements to destroy
policy
-
the execution policy to use
Type requirements
-
ForwardIt must meet the requirements of LegacyForwardIterator.
-No increment, assignment, comparison, or indirection through valid instances of
ForwardIt may throw exceptions.
[edit] Complexity
Linear in the distance between first and last.
[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
ExecutionPolicyis one of the standard policies, std::terminate is called. For any otherExecutionPolicy, the behavior is implementation-defined. - If the algorithm fails to allocate memory, std::bad_alloc is thrown.
[edit] Possible implementation
template<class ForwardIt> constexpr // since C++20 void destroy(ForwardIt first, ForwardIt last) { for (; first != last; ++first) std::destroy_at (std::addressof (*first)); }
[edit] Example
The following example demonstrates how to use 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::destroy(ptr, ptr + 8); }
Output:
0 destructed 1 destructed 2 destructed 3 destructed 4 destructed 5 destructed 6 destructed 7 destructed