uninitialized_fill_n

template<class FwdIt, class Size, class Ty>
    void uninitialized_fill_n(FwdIt first, Size count,
        const Ty& val);

The template function effectively executes:

while (0 < count--)
    new ((void *)&*first++)
        iterator_traits<FwdIt>::value_type(val);

unless the code throws an exception. In that case, all constructed objects are destroyed and the exception is rethrown.