< cpp‎ | memory
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<ForwardIterator>::value_type(x);
If an exception is thrown during the initialization, the function has no effects. {{{1}}}
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.

[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,
  • if policy is std::parallel_vector_execution_policy, std::terminate is called
  • if policy is std::sequential_execution_policy or std::parallel_execution_policy, the algorithm exits with an std::exception_list containing all uncaught exceptions. If there was only one uncaught exception, the algorithm may rethrow it without wrapping in std::exception_list. It is unspecified how much work the algorithm will perform before returning after the first exception was encountered.
  • if policy is some other type, the behavior is implementation-defined
  • If the algorithm fails to allocate memory (either for itself or to construct an std::exception_list when handling a user exception), 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) [edit]
parallelized version of std::uninitialized_fill
(function template) [edit]