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Defined in header <memory> | ||
template<class InputIt,class NoThrowForwardIt> NoThrowForwardIt uninitialized_move( InputIt first, InputIt last, | (1) | (since C++17) (constexpr since C++26) |
template<class ExecutionPolicy, class ForwardIt,class NoThrowForwardIt> | (2) | (since C++17) |
[first, last) (using move semantics if supported) to an uninitialized memory area beginning atd_first as if byfor(; first!= last;++d_first,(void)++first) ::new(voidify(*d_first)) typenamestd::iterator_traits<NoThrowForwardIt>::value_type(/* value */);
return d_first;
[first, last) are left in a valid but unspecified state, and the objects already constructed are destroyed in an unspecified order.std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> istrue. | (until C++20) |
std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> istrue. | (since C++20) |
Ifd_first | (since C++20) |
Contents |
| first, last | - | the pair of iterators defining therange of elements to move |
| d_first | - | the beginning of the destination range |
| policy | - | theexecution policy to use |
| Type requirements | ||
-InputIt must meet the requirements ofLegacyInputIterator. | ||
-ForwardIt must meet the requirements ofLegacyForwardIterator. | ||
-NoThrowForwardIt must meet the requirements ofLegacyForwardIterator. | ||
-No increment, assignment, comparison, or indirection through valid instances ofNoThrowForwardIt may throw exceptions. | ||
As described above.
Linear in the distance betweenfirst andlast.
The overload with a template parameter namedExecutionPolicy reports errors as follows:
ExecutionPolicy is one of thestandard policies,std::terminate is called. For any otherExecutionPolicy, the behavior is implementation-defined.When the input iterator deferences to an rvalue, the behavior ofstd::uninitialized_move is same asstd::uninitialized_copy.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_raw_memory_algorithms | 202411L | (C++26) | constexpr forspecialized memory algorithms,(1) |
template<class InputIt,class NoThrowForwardIt>constexpr NoThrowForwardIt uninitialized_move(InputIt first, InputIt last, NoThrowForwardIt d_first){using ValueType=typenamestd::iterator_traits<NoThrowForwardIt>::value_type;auto current= d_first;try{for(; first!= last;++first,(void)++current){auto addr=static_cast<void*>(std::addressof(*current));ifconstexpr(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;}} |
#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(constexprauto 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!"
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 aconst 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 |
| 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] |
