xo_flush_h(3) on FreeBSD
The text 79cdf77f9993, as FreeBSD 12.4-RELEASE, FreeBSD 12.3-RELEASE, FreeBSD 12.2-RELEASE, FreeBSD 12.1-RELEASE, FreeBSD 12.0-RELEASE, FreeBSD 11.4-RELEASE, FreeBSD 11.3-RELEASE, FreeBSD 11.2-RELEASE shipped it.
flush formatted output from libxo handle