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std::ranges::uninitialized_fill

From cppreference.com
< cpp‎ | memory
 
C++
 
Memory management library
(exposition only*)
Allocators
Uninitialized memory algorithms
Constrained uninitialized memory algorithms
Memory resources
Uninitialized storage (until C++20)
(until C++20*)
(until C++20*)
(until C++20*)

Garbage collector support (until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
 
Defined in header <memory>
Call signature
template< no-throw-forward-iterator I, no-throw-sentinel-for<I> S,

          class T >
    requires std::constructible_from<std::iter_value_t<I>, const T&>

I uninitialized_fill( I first, S last, const T& value );
 (1) (since C++20)
(constexpr since C++26)
template< no-throw-forward-range R, class T >

    requires std::constructible_from<ranges::range_value_t<R>,
                                     const T&>
ranges::borrowed_iterator_t<R> uninitialized_fill( R&& r,

                                                   const T& value );
 (2) (since C++20)
(constexpr since C++26)
1) Copies value to an uninitialized memory area [first, last) as if by

for (; first != last; ++first)
    ::new (voidify(*first)) std::remove_reference_t<std::iter_reference_t<I>>(value);
return first;

If an exception is thrown during the initialization, the objects already constructed are destroyed in an unspecified order.
2) Equivalent to return ranges::uninitialized_fill(ranges::begin(r), ranges::end(r), value);.

The function-like entities described on this page are algorithm function objects (informally known as niebloids), that is:

Contents

[edit] Parameters

first, last - the iterator-sentinel pair defining the range of elements to initialize
r - the range of the elements to initialize
value - the value to construct the elements with

[edit] Return value

As described above.

[edit] Complexity

Linear in the size of the uninitialized memory area.

[edit] Exceptions

Any exception thrown on construction of the elements in the destination range.

[edit] Notes

An implementation may improve the efficiency of the ranges::uninitialized_fill, e.g. by using ranges::fill, if the value type of the output range is TrivialType.

Feature-test macro Value Std Feature
__cpp_lib_raw_memory_algorithms 202411L (C++26) constexpr for specialized memory algorithms, (1,2)

[edit] Possible implementation

struct uninitialized_fill_fn
{
    template<no-throw-forward-iterator I, no-throw-sentinel-for<I> S, class T>
        requires