sb-posix:tcsetattr segfaults on OpenBSD

[David Lamkins]

$ sbcl --version
SBCL 2.2.5.openbsd
$ uname -a
OpenBSD gilva.local 7.2 GENERIC.MP#2 amd64

Test case

(require 'sb-posix)

(defun invoke-with-echoing-disabled (thunk)
  (let ((fd (sb-sys:fd-stream-fd sb-sys:*stdout*)))
    (if (zerop (sb-unix:unix-isatty fd))
      (funcall thunk)
      (let ((termios (sb-posix:tcgetattr fd)))
        (setf (sb-posix:termios-lflag termios)
              (logand (sb-posix:termios-lflag termios)
                      (lognot sb-posix:echo)))
        (sb-posix:tcsetattr fd sb-posix:tcsaflush termios)
        (unwind-protect
          (funcall thunk)
          (setf (sb-posix:termios-lflag termios)
                (logior (sb-posix:termios-lflag termios)
                        sb-posix:echo))
          (sb-posix:tcsetattr fd sb-posix:tcsaflush termios))))))

(defmacro with-echoing-disabled (&body body)
  `(invoke-with-echoing-disabled (lambda () ,@body)))

$ sbcl --load test.lisp --eval '(with-echoing-disabled (read))'

Expected behavior: I type a form which is not echoed, but is printed when I press enter.
Observed behavior: sbcl exits immediately.

When I ktrace the above invocation, I can see the tcgetattr call succeed, but there's a SEGV where the tcsetattr trace should appear.

Note that the same code works as intended running on the sbcl packaged for Ubuntu:

$ sbcl --version
SBCL 2.1.11.debian
$ uname -a
Linux dlamkins-0316 5.15.0-56-generic #62-Ubuntu SMP Tue Nov 22 19:54:14 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux