The dev-libs/cyrus-sasl-2.1.27-r2 version is no longer printing function names to logs:
May 31 11:26:09 hostname saslauthd: : master exited: 19626
May 31 11:26:09 hostname saslauthd: : master pid is: 438
May 31 11:26:09 hostname saslauthd: : listening on socket: /run/saslauthd/mux
I tracked this back to the configure script no longer defining HAVE_FUNC. There was a patch for 2.1.25 that would add this functionality to configure.h.in but after the project switched to configure.ac the patches' functionality has been lost.
The same issue has been filed with the cyrus-sasl library: https://github.com/cyrusimap/cyrus-sasl/issues/571