std::uninitialized_fill_n - cppreference.com (original) (raw)

1. Copies value to an uninitialized memory area first+ [​0​, count) as if by

for (; count--; ++first)
::new ([_voidify_](voidify.html "cpp/memory/voidify")(\*first)) typename std::iterator_traits<NoThrowForwardIt>::value_type(value);
return first;

If an exception is thrown during the initialization, the objects already constructed are destroyed in an unspecified order.

1. Same as (1), but executed according to policy.

This overload participates in overload resolution only if all following conditions are satisfied:

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Exceptions
• 5 Notes
• 6 Possible implementation
• 7 Example
• 8 Defect reports
• 9 See also

[edit] Parameters

[edit] Return value

As described above.

[edit] Complexity

Linear in count.

[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 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.

[edit] Notes

[edit] Possible implementation

template<class NoThrowForwardIt, class Size, class T> constexpr NoThrowForwardIt uninitialized_fill_n(NoThrowForwardIt first, Size count, const T& value) { using V = typename std::iterator_traits::value_type; NoThrowForwardIt current = first; try { for (; count > 0; ++current, (void) --count) ::new (static_cast<void*>(std::addressof(*current))) V(value); return current; } catch (...) { for (; first != current; ++first) first->~V(); throw; } return current; }

[edit] Example

Output:

Example Example Example Example

[edit] Defect reports

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

[edit] See also