std::memset only works for sequential and contiguous memory. std::fill works on pretty much anything that has std::begin() and std::end(). As the conclusion of

std::memset only works for sequential and contiguous memory. std::fill works on pretty much anything that has std::begin() and std::end(). As the conclusion of the article says I would use the idiomatic way first, then and only if I have performance issues, actually force it to memset. The only bad thing here is that, gcc only do the reasonable optimization on '-O3'.