According to
https://developer.apple.com/documentation/dnssd/1804733-dnsserviceregister
the DNSServiceRef is initialized only if DNSServiceRegister() returns
kDNSServiceErr_NoError.  The faulty error handling code could
therefore crash.

Preparing for a variant of TimerEvent with coarse 1-second
granularity, but cheaper (with a timer wheel).

zeroconf/ZeroconfBonjour: Fix compile errors resulting from "refactor to SocketEvent" and reenable bonjour for darwin build

Similar to commits 1686f4e8 and
30a5dd26

"DEFAULT" is a bad name - all it says is that it's the default value,
but it doesn't say what it means.  The name NOTICE mimics the syslog
level.

These flags are output-only.

[[maybe_unused]] (introduced in C++17) is standard C++.

https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
says that this is equivalent to the GNU unused attribute.
Signed-off-by: Rosen Penev <rosenp@gmail.com>