openpam_straddch(3) on FreeBSD
The text 710c355357ad, as FreeBSD 13.2-RELEASE, FreeBSD 13.1-RELEASE, FreeBSD 13.0-RELEASE, FreeBSD 12.4-RELEASE, FreeBSD 12.3-RELEASE, FreeBSD 11.4-RELEASE, FreeBSD 11.3-RELEASE shipped it.
add a character to a string, expanding the buffer if needed