file-position doesn't support large files on win32
On 32-bit windows, file-position is limited by 32 bit offsets. Actually the windows implementation of seek in sbcl supports large offsets, but it's blocked by the ansi-stream-
(declare (type (or index (alien sb!unix:off-t) (member nil :start :end))
while it should be:
(declare (type (or index (alien sb!unix:
sb-unix:unix-offset was introduced just for this particular case, but it's not actually used.
You can reproduce it with:
(file-position (open "test" :if-does-not-exist :create) 10000000000)
Tested with sbcl 1.1.12, 1.1.14 and HEAD on win32.