how did BSD libc make binary compatibility promise beetween freebsd version?

[kang joni]

As the title suggest, I usually compile my linux code from old debian
squeeze to run for either centos 6 or debian wheezy and these distros
later version and adjusting some app rpath and clang libc++ runtime
libs to point local relative file path via origin method. Is there any
easy guideline to follow when working on bsd libc version? I feels do
not like on how libc emulation method as it seems complex
configuration fine tuning for starter BSD like me.

Thanks.