< cpp‎ | memory
Dynamic memory management
Uninitialized storage
(deprecated since c++17)
(deprecated since c++17)
(deprecated since c++17)
Garbage collection support
C Library
Low level memory management
Defined in header <memory>
template< class ForwardIt, class T >
void uninitialized_fill( ForwardIt first, ForwardIt last, const T& value );
template< class ExecutionPolicy, class ForwardIt, class T >
void uninitialized_fill( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, const T& value );
(2) (since C++17)
1) Copies the given value to an uninitialized memory area, defined by the range [first, last) as if by
for (; first != last; ++first)
  ::new (static_cast<void*>(std::addressof(*first)))
      typename iterator_traits<ForwardIt>::value_type(x);
If an exception is thrown during the initialization, the function has no effects.
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


[edit] 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 execution policy for details.
Type requirements
ForwardIt must meet the requirements of ForwardIterator.
No increment, assignment, comparison, or indirection through valid instances of ForwardIt may throw exceptions.

[edit] Return value


[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, std::terminate is called.
  • If the algorithm fails to allocate memory, std::bad_alloc is thrown.

[edit] Possible implementation

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

[edit] Example

#include <algorithm>
#include <iostream>
#include <memory>
#include <string>
#include <tuple>
int main()
    std::string* p;
    std::size_t sz;
    std::tie(p, sz) = std::get_temporary_buffer<std::string>(4);
    std::uninitialized_fill(p, p+sz, "Example");
    for (std::string* i = p; i != p+sz; ++i) {
        std::cout << *i << '\n';



[edit] See also

copies an object to an uninitialized area of memory, defined by a start and a count
(function template)
parallelized version of std::uninitialized_fill
(function template)