[Openmcl-devel] Raw-mode terminal weirdness redux

Ron Garret ron at flownet.com
Tue Mar 27 09:32:54 PDT 2018

Found a reliable workaround!

(defun %write (s)
  (with-cstrs ((cs s))
    (#_write 1 cs (length s))))

(defun test ()
  (rlet ((normal :termios))
    (#_tcgetattr 0 normal) ; This breaks it
    (rlet ((raw :termios))
      (#_tcgetattr 0 normal)
      (#_cfmakeraw raw)
      (%write "abc")
            (#_tcsetattr 0 2 raw)
            (%write "def"))
        (#_tcsetattr 0 2 normal)))
    (%write "hij")))

This version is broken.  If you comment out the line that says “This breaks it” it will start working properly.  Both working and non-working versions are 100% reliable.  Using a single RLET to allocate both termios structures also works.  It’s only when there is a call to tcgetattr in between the allocations that it breaks.  (Note that the “broken” version works in 1.8.  But for the fact that C code can reproduce this problem intermittently I would call this slam-dunk evidence that this is a bug in the CCL compiler, most likely in RLET.  But since the C code does what it does, I’m not willing to go quite that far.)

I’m not sure if this qualifies me to claim my own bug bounty or not :-)

Note that we now have this extremely interesting situation where a Lisp program is more reliable than the corresponding C program!


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