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    std::uninitialized_move

    From cppreference.com
     
    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>
    template< class InputIt, class NoThrowForwardIt > NoThrowForwardIt uninitialized_move( InputIt first, InputIt last, NoThrowForwardIt d_first );
    		 (1) (since C++17)
    (constexpr since C++26)
    template< class ExecutionPolicy, class ForwardIt, class NoThrowForwardIt > NoThrowForwardIt uninitialized_move( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, NoThrowForwardIt d_first );
    		 (2) (since C++17)
    1) Copies the elements from [first, last) (using move semantics if supported) to an uninitialized memory area beginning at d_first as if by
    See More

    for (; first != last; ++d_first, (void) ++first)
        ::new (voidify(*d_first))
            typename std::iterator_traits<NoThrowForwardIt>::value_type(/* value */);
    return d_first;

    where /* value */ is std::move(*first) if *first is of an lvalue reference type, or *first otherwise.
    If an exception is thrown during the initialization, some objects in [first, last) are left in a valid but unspecified state, and the objects already constructed are destroyed in an unspecified order.
    2) Same as (1), but executed according to policy.
    This overload participates in overload resolution only if all following conditions are satisfied:

    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)


    If d_first + [0, std::distance(first, last)) overlaps with [first, last), the behavior is undefined.

    		(since C++20)

    Parameters

    first, last - the pair of iterators defining the range of elements to move
    d_first - the beginning of the destination range
    policy - the execution policy to use
    Type requirements
    -
    InputIt must meet the requirements of LegacyInputIterator.
    -
    ForwardIt must meet the requirements of LegacyForwardIterator.
    -
    NoThrowForwardIt must meet the requirements of LegacyForwardIterator.
    -
    No increment, assignment, comparison, or indirection through valid instances of NoThrowForwardIt may throw exceptions.

    Return value

    As described above.

    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.

    Notes

    When the input iterator deferences to an rvalue, the behavior of std::uninitialized_move is same as std::uninitialized_copy.

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

    Possible implementation

    template<class InputIt, class NoThrowForwardIt>
constexpr NoThrowForwardIt uninitialized_move(InputIt first, InputIt last,
                                              NoThrowForwardIt d_first)
{
    using ValueType = typename std::iterator_traits<NoThrowForwardIt>::value_type;
    auto current = d_first;
    try
    {
        for (; first != last; ++first, (void) ++current)
        {
            auto addr = static_cast<void*>(std::addressof(*current));
            if constexpr (std::is_lvalue_reference_v<decltype(*first)>)
                ::new (addr) ValueType(std::move(*first));
            else
                ::new (addr) ValueType(*first);
        }
        return current;
    }
    catch (...)
    {
        std::destroy(d_first, current);
        throw;
    }
}

    Example

    Run this code
    #include <cstdlib>
#include <iomanip>
#include <iostream>
#include <memory>
#include <string>

void print(auto rem, auto first, auto last)
{
    for (std::cout << rem; first != last; ++first)
        std::cout << std::quoted(*first) << ' ';
    std::cout << '\n';
}

int main()
{
    std::string in[]{"Home", "Work!"};
    print("initially, in: ", std::begin(in), std::end(in));
    
    if (
        constexpr auto sz = std::size(in);
        void* out = std::aligned_alloc(alignof(std::string), sizeof(std::string) * sz))
    {
        try
        {
            auto first{static_cast<std::string*>(out)};
            auto last{first + sz};
            std::uninitialized_move(std::begin(in), std::end(in), first);
            
            print("after move, in: ", std::begin(in), std::end(in));
            print("after move, out: ", first, last);
            
            std::destroy(first, last);
        }
        catch (...)
        {
            std::cout << "Exception!\n";
        }
        std::free(out);
    }
}

    Possible output: 

    initially, in: "Home" "Work!"
after move, in: "" ""
after move, out: "Home" "Work!"

    Defect reports

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

    DR Applied to Behavior as published Correct behavior
    LWG 3870 C++20 this algorithm might create objects on a const storage kept disallowed
    LWG 3918 C++17 additional temporary materialization was required
    when the input iterator deferences to a prvalue     		copies the element in this case

    See also

    		 copies a range of objects to an uninitialized area of memory
    (function template) [edit]
    (C++17)
    		 moves a number of objects to an uninitialized area of memory
    (function template) [edit]
    (C++20)
    		 moves a range of objects to an uninitialized area of memory
    (algorithm function object)[edit]