systemd now requires the mallinfo or mallinfo2 functions for building.
musl does not presently provide them. Therefore, systemd cannot be
built. Since systemd provides an essential package, this undermines the
availability of a musl port. I think this warrants important severity.

mallinfo2 is not only needed by systemd, but also by Android. In that
context, a patch was submitted.
https://www.openwall.com/lists/musl/2022/01/06/2
Rich Felker indicated a rather strong rejection of mallinfo due to the
use of too small size types. He offered a constructive review for
mallinfo2. That lead to a second version of the patch.
https://www.openwall.com/lists/musl/2022/01/07/7

Would it be sensible for Debian to include this patch in the packaging
deviating from upstream? It would probably be fine to remove the
addition of mallinfo to force users onto mallinfo2.

Helmut

Control: tags -1 + moreinfo

This has become more tricky. Due to the work of PostmarketOS and others,
systemd gained explicit support for musl and its way of doing so is
vendoring a couple of libraries providing stuff that's missing from
musl. One piece is mallinfo2. Now when compiling systemd with
-Dlibc=musl that mallinfo2 substitution conflicts with a musl that
provides mallinfo2.

I've not reached a final conclusion yet, but since other distributions
tend to not extend their musl with mallinfo2, Debian probably shouldn't
do so either and the immediate need vanished.

Helmut