https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92546
--- Comment #15 from Jonathan Wakely <redi at gcc dot gnu.org> --- <algorithm> and <memory> got unavoidably bigger in C++20 due to the extra algos in std::ranges. <valarray> includes <algorithm> so is larger. We can almost certainly replace <algorithm> with <bits/stl_algobase.h> and <bits/stl_algo.h> for <valarray>'s purposes, it doesn't use the ranges algos. <chrono> got a little bigger for C++20, and will grow bigger when the timezone features are added. We should add <bits/chrono.h> with just duration, time_point, steady_clock and system_clock, for use in <thread>, <mutex> etc. <iterator> has all the concepts stuff, and that makes a lot of other headers bigger. We might want to move common_iterator and counted_iterator out of <bits/stl_iterator.h> so they're only included by <iterator> and not the bits that <vector> etc. use.
