Rust stacktraces are <unknown> on FreeBSD

Tonight I ran into an issue where when a rust program panics on my FreeBSD laptop, the stacktrace doesn’t contain code locations, and instead shows <unknown> on every line:

$ RUST_BACKTRACE=full cargo run --bin gpt-fat-disk-image-create -- -l -d /foo/bar/ -o /tmp/a
    Finished dev [unoptimized + debuginfo] target(s) in 0.06s
     Running `target/debug/gpt-fat-disk-image-create -l -d /foo/bar/ -o /tmp/a`
thread 'main' panicked at 'source slice length (92) does not match destination slice length (512)', /rustc/31530e5d132ebcc3654baf2e5460599681520af0/library/core/src/slice/
stack backtrace:
   0:          0x11298b1 - <unknown>
   1:          0x1141d60 - <unknown>
   2:          0x11277df - <unknown>
   3:          0x112b59d - <unknown>
   4:          0x112b24c - <unknown>
   5:          0x112bc45 - <unknown>
   6:          0x112b80d - <unknown>
   7:          0x1129d70 - <unknown>
   8:          0x112b7cc - <unknown>
   9:          0x1141040 - <unknown>
  10:          0x11437f7 - <unknown>
  11:          0x10a0864 - <unknown>
  12:          0x1096c59 - <unknown>
  13:          0x1096095 - <unknown>
  14:          0x108351d - <unknown>
  15:          0x1073e66 - <unknown>
  16:          0x108af2e - <unknown>
  17:          0x107bad1 - <unknown>
  18:          0x106a3c4 - <unknown>
  19:          0x112c0ae - <unknown>
  20:          0x106a3a2 - <unknown>
  21:          0x1073f0b - <unknown>
  22:          0x106a10b - <unknown>

Sounds at least related to a known issue, but that issue is already closed and not necessarily the same problem so I raised a new one. It’s not clear whether the problem lies with rust or FreeBSD (or elsewhere).

But this is a major hindrance to my productivity! Rust development is the main thing I use this computer for. There are a couple of Linux distros I’ve been meaning to check out, namely void and crux, and I can always go crawling back to archlinux if they don’t work out.