std:: uninitialized_fill
|
|
|
|
Defined in header
<memory>
|
||
template
<
class
ForwardIt,
class
T
>
void uninitialized_fill ( ForwardIt first, ForwardIt last, const T & value ) ; |
(1) | |
template
<
class
ExecutionPolicy,
class
ForwardIt,
class
T
>
void
uninitialized_fill
(
ExecutionPolicy
&&
policy,
|
(2) | (since C++17) |
[
first
,
last
)
as if by
for
(
;
first
!
=
last
;
++
first
)
:: new ( /* VOIDIFY */ ( * first ) )
typename std:: iterator_traits < ForwardIt > :: value_type ( value ) ;
|
(until C++11) |
|
(since C++11) |
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) |
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
LegacyForwardIterator
.
|
||
-
ForwardIt
may throw exceptions.
Applying
&
*
to a
ForwardIt
value must yield a pointer to its value type.
(until C++11)
|
Return value
(none)
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 otherExecutionPolicy
, the behavior is implementation-defined. - If the algorithm fails to allocate memory, std::bad_alloc is thrown.
Possible implementation
template<class ForwardIt, class T> void uninitialized_fill(ForwardIt first, ForwardIt last, const T& value) { using V = typename std::iterator_traits<ForwardIt>::value_type; ForwardIt current = first; try { for (; current != last; ++current) ::new (static_cast<void*>(std::addressof(*current))) V(value); } catch (...) { for (; first != current; ++first) first->~V(); throw; } } |
Example
#include <algorithm> #include <iostream> #include <memory> #include <string> int main() { const std::size_t sz = 4; std::allocator<std::string> alloc; std::string* p = alloc.allocate(sz); std::uninitialized_fill(p, p + sz, "Example"); for (std::string* i = p; i != p + sz; ++i) { std::cout << *i << '\n'; i->~basic_string<char>(); } alloc.deallocate(p, sz); }
Output:
Example Example Example Example
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 866 | C++98 |
given
T
as the value type of
ForwardIt
, if
T :: operator new exists, the program might be ill-formed |
uses global replacement-
new instead |
LWG 2433 | C++11 | this algorithm might be hijacked by overloaded operator & | uses std::addressof |
LWG 3870 | C++20 | this algorithm might create objects on a const storage | kept disallowed |
See also
copies an object to an uninitialized area of memory, defined by a start and a count
(function template) |
|
(C++20)
|
copies an object to an uninitialized area of memory, defined by a range
(algorithm function object) |