[no subject]

[REM@SUWATSON.stanford.edu]

I've had pretty good luck programming the resource manager traps
directly from MACL 1.2.2, but I'm having trouble with the file manager,
for example:

First I do this to load the traps.fasl file:
(require "traps")

Then I do this to define a function that should be similar to EJECT-DISK
except actually unmounting the disk instead of just ejecting it (and
returning the system error code as an integer):
(defun volname-unmount (volstr)
  (with-pstrs ((volName volStr))
    (_UnmountVol :a0 volName :d0 0 :d0)))

Then I insert diskette REM390, wait a second for the system to mount it,
and then try calling the function, which gives a system bomb (ID = 02 or
10 usually):
(volname-unmount "REM390:")

I'm probably doing something really dumb, but I can't see it. Can
somebody tell me what I'm doing wrong?