std::uninitialized_value_construct (3) - Linux Man Pages

std::uninitialized_value_construct: std::uninitialized_value_construct

NAME

std::uninitialized_value_construct - std::uninitialized_value_construct

Synopsis


Defined in header <memory>
template< class ForwardIt > (1) (since C++17)
void uninitialized_value_construct( ForwardIt first, ForwardIt last);
template< class ExecutionPolicy, class ForwardIt > (2) (since C++17)
void uninitialized_value_construct( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last );


1) Constructs objects of type typename iterator_traits<ForwardIt>::value_type in the uninitialized storage designated by the range [first, last) by value-initialization, as if by


  for (; first != last; ++first)
    ::new (static_cast<void*>(std::addressof(*first)))
        typename std::iterator_traits<ForwardIt>::value_type();


If an exception is thrown during the initialization, the objects already constructed are destroyed in an unspecified order.
2) Same as (1), but executed according to policy. This overload does not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true

Parameters


first, last - the range of the elements to initialize
policy - the execution policy to use. See execution_policy for details.

Type requirements


-
ForwardIt must meet the requirements of LegacyForwardIterator.
-
No increment, assignment, comparison, or indirection through valid instances of ForwardIt may throw exceptions.

Return value


(none)

Complexity


Linear in the distance between first and last

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.

Possible implementation


  template<class ForwardIt>
  void uninitialized_value_construct(ForwardIt first, ForwardIt last)
  {
      using Value = typename std::iterator_traits<ForwardIt>::value_type;
      ForwardIt current = first;
      try {
          for (; current != last; ++current) {
              ::new (static_cast<void*>(std::addressof(*current))) Value();
          }
      } catch (...) {
          std::destroy(first, current);
          throw;
      }
  }

Example


 This section is incomplete
 Reason: no example

See also


uninitialized_value_construct_n constructs objects by value-initialization in an uninitialized area of memory, defined by a start and a count
                                (function template)
(C++17)


uninitialized_default_construct constructs objects by default-initialization in an uninitialized area of memory, defined by a range
                                (function template)
(C++17)