The machine-specific atomics implementations are an optional optimization. (Heck, even threading is still an optional optimization in BIND.) I think it falls back to a generic implementation if you're on a platform they haven't ported it to. Personally, I think they're more trouble than they're worth -- see, e.g., https://bugs.debian.org/778720 -- and ought to be replaced with calls to the equivalent machine-independent compiler-provided intrinsics, on compilers that support those intrinsics.
I'm not sure if ISC has a formally defined portability target for BIND (at least, I don't think they did when I was there). But you'll occasionally see commits targeting systems that have long since been abandoned by their vendors, e.g.:
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Date: 2016-05-21 17:38 (UTC)I'm not sure if ISC has a formally defined portability target for BIND (at least, I don't think they did when I was there). But you'll occasionally see commits targeting systems that have long since been abandoned by their vendors, e.g.:
https://source.isc.org/cgi-bin/gitweb.cgi/?p=bind9.git;a=commitdiff;h=6f6b1abb106d970f1b0c5e959cddfabc9cc3b4ae