https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114839
--- Comment #4 from Ed Maste <emaste at freebsd dot org> --- Thanks - 54568 adds some good context. Based on that I think it may that frame registration calls are not present in the FreeBSD crt bits used for static binaries, which could explain the differences in OSes. We could look into adding the registration calls, but it seems that using --eh-frame-hdr always is the best path for us.
