It's unfortunate that the C++ version of the code assumes the type T is default-constructible (and that the default constructor is cheap). It also assumes that the type T is copy-constructible; at a glance I can't tell if the algorithm depends on making a copy in every place that it does make a copy. E.g. in the `heap_sort` helper we have

    T k;                       // default-construct
    if (i > 0) k = left[--i];  // copy-assign

This fairly obviously could be replaced with "copy-construct." Could it be replaced with "move-construct"? I don't know. Again, in `partition_small`, we have

    T swbuf[SMALLPART];

which default-constructs a bunch of Ts. I think we're just going to overwrite that memory in a moment anyway, so constructing all those Ts is a waste of cycles; but I'm not sure.

All of my "I don't knows" and "I'm not sures" are due to my own lack of digging into the code; I'm sure one could find out if one really looked.

None of that matters if you're just sorting `int` or the benchmarked `struct entry`. But it matters a great deal if you're taking the README literally and trying to sort "types with higher copy costs [...] (such as strings)".