Valgrind integration

I maintain Valgrind on FreeBSD and I've been wondering a bit about the Valgrind integration that was in jemalloc.

I saw on some old manpages that there were some options for Valgrind:

https://www.unix.com/man-page/FreeBSD/3/malloc/

I was wondering what these did and what was the benefit.

Initially I sent an e-mail to David Goldblatt who said

"We got rid of most of the internal handling of valgrind integration a while back. IIRC this wasn't borne of any specific opposition, but we didn't have any CI set up for it and so we kept breaking it accidentally (and decided it was better to not pretend that it worked). I think the man page references should be removed in current versions.

Jemalloc isn't my day job any more so I don't want to commit the current maintainers to anything, but I think that they'd probably be receptive to reinserting the valgrind hooks so long as it was careful about the fast path and came with CI testing too. Probably the best followup is on a github issue (feel free to quote me on any of this if you'd like)."

So I'm posting here.

Start by reviewing the current state of jemalloc's Valgrind integration and the existing CI testing setup, with attention to the fast path. The scope is not settled: determine whether the work should restore hooks, add CI coverage, and update the outdated manpage references, then define completion criteria with the maintainers.