openpam_straddch(3) on FreeBSD
The text 324b0d20d0f1, as FreeBSD 11.2-RELEASE, FreeBSD 11.1-RELEASE, FreeBSD 11.0-RELEASE, FreeBSD 10.4-RELEASE, FreeBSD 10.3-RELEASE, FreeBSD 10.2-RELEASE, FreeBSD 10.1-RELEASE shipped it.
add a character to a string, expanding the buffer if needed