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std::uninitialized_fill(3)     C++ Standard Libary    std::uninitialized_fill(3)

NAME
     std::uninitialized_fill - std::uninitialized_fill

Synopsis
	Defined in header <memory>
	template< class ForwardIt, class T >
	void uninitialized_fill( ForwardIt first, ForwardIt last, const T& (1)
	value );
	template< class ExecutionPolicy, class ForwardIt, class T >

	void  uninitialized_fill(  ExecutionPolicy&& policy,		     (2)
     (since C++17)

				 ForwardIt first, ForwardIt last, const T&
	value );

	1) Copies the given value to an uninitialized memory  area,  defined  by
     the range
	[first, last) as if by for (; first != last; ++first)
	    ::new (/* VOIDIFY */(*first))
		typename std::iterator_traits<ForwardIt>::value_type(value);
	where /* VOIDIFY */(e) is:

	static_cast<void*>(&e)		      (until C++11)
	static_cast<void*>(std::addressof(e)) (since C++11)

	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 partici-
     pates in
	overload resolution only if

	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)

Parameters
	first, last	     -	       the range of the elements to initialize
	value		     -	       the value to construct the elements with
	policy		      - 	 the execution policy to use. See execu-
     tion policy for
				       details.

Type requirements
	-
	ForwardIt must meet the requirements of LegacyForwardIterator.
	-
	No increment, assignment, comparison, or indirection through  valid  in-
     stances of
	ForwardIt may throw exceptions.
	Applying &* to a ForwardIt value must yield a pointer to its value type.
	(until C++11)

Return value
	(none)

Complexity
	Linear in the distance between first and last.

Exceptions
	The overload with a template parameter named ExecutionPolicy reports er-
     rors 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-de-
     fined.
	  * If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation
	template<class ForwardIt, class T>
	void uninitialized_fill(ForwardIt first, ForwardIt last, const T& value)
	{
	    using V = typename std::iterator_traits<ForwardIt>::value_type;
	    ForwardIt current = first;
	    try
	    {
		for (; current != last; ++current)
		    ::new	  (static_cast<void*>(std::addressof(*current)))
     V(value);
	    }
	    catch (...)
	    {
		for (; first != current; ++first)
		    first->~V();
		throw;
	    }
	}

Example
     // Run this code

      #include <algorithm>
      #include <iostream>
      #include <memory>
      #include <string>

      int main()
      {
	  const std::size_t sz = 4;
	  std::allocator<std::string> alloc;
	  std::string* p = alloc.allocate(sz);

	  std::uninitialized_fill(p, p + sz, "Example");

	  for (std::string* i = p; i != p + sz; ++i)
	  {
	      std::cout << *i << '\n';
	      i->~basic_string<char>();
	  }

	  alloc.deallocate(p, sz);
      }

Output:
Example
Example
Example
Example
	Defect reports

	The  following	behavior-changing  defect  reports were applied retroac-
     tively to
	previously published C++ standards.

	   DR	 Applied to	     Behavior as published		 Correct
     behavior
			    given T as the value type of ForwardIt,
	LWG  866  C++98      if 				     uses global
     replacement-
			    T::operator new exists, the program     new instead
			    might be ill-formed
	LWG 2433  C++11       this  algorithm  might  be  hijacked  by	    uses
     std::addressof
			    overloaded operator&
	LWG  3870 C++20      this algorithm might create objects on  kept disal-
     lowed
			    a const storage

See also
				   copies an object to an uninitialized area  of
     memory,
	uninitialized_fill_n	   defined by a start and a count
				   (function template)
	ranges::uninitialized_fill  copies an object to an uninitialized area of
     memory,
	(C++20) 		   defined by a range
				   (niebloid)

http://cppreference.com 	   2024.06.10	      std::uninitialized_fill(3)
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