add qsort

[gmmyung]

Most part of the source code is copied from relibc, which is under MIT license.

[jonathanpallant]

Couple of small notes. But also, can you run cargo-tarpaulin on this and check we have good coverage? We have a lot of large, complex, undocumented functions here and we should really check they all work correctly no matter what input they are given. For example, I suspect we don’t hit the recursion limit? It may also make sense to unit test the helper functions.

[jonathanpallant]

Plus I don’t understand the failure on beta. Any ideas?

[gmmyung]

Plus I don’t understand the failure on beta. Any ideas?

It seems like stable rust doesn't not have runtime checks on copy_from_nonoverlapping.
https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=7a8fae6d1301cfc983e9fe9d853e00e3

Maybe this should be also fixed in upstream relibc.

[gmmyung]

Added tests for more coverage. The coverage is at 96%, but testing the fallback to heapsort when we hit max_depth is tough to reach.

[thejpster]

I have some ideas to make this much safer, basically operating entirely on indicies and only dealing with pointers when items have to be compared or swapped. But I see no reason for that to block this.

Stale