CLOSE :ABORT T on superseding streams

[Nikodemus Siivola]

Closing a stream opened with :IF-EXISTS :SUPERSEDE with :ABORT T leaves no
file on disk, even if one existed before opening.

The illegality of this is not crystal clear, as the ANSI dictionary
entry for CLOSE says that when :ABORT is T superseded files are not
superseded (ie. the original should be restored), whereas the OPEN
entry says about :IF-EXISTS :SUPERSEDE "If possible, the
implementation should not destroy the old file until the new stream
is closed." -- implying that even though undesirable, early deletion
is legal. Restoring the original would none the less be the polite
thing to do.

Note: Richard Kreuter's "transaction stream" proposal (sbcl-devel link goes here)
would be one way to address this, and other related issues.

[Tomas Hlavaty (tomas-hlavaty)]

simple test case (works as expected on ccl and allegro):

(let ((fname "/tmp/a"))
  ;; touch
  (with-open-file (s fname :direction :output :if-exists :supersede)
    (format s "hello~%"))
  ;; supersede
  (catch 'hi
    (with-open-file (s fname :direction :output :if-exists :supersede)
      (format s "hi~%")
      (throw 'hi nil)))
  ;; check still exists
  (assert (probe-file fname)) ;; <=== it was deleted:-{
  (with-open-file (s fname)
    (assert (equal "hello" (read-line s)))
    t))

[Pierre Neidhardt (ambrevar)]

I was bitten by this as well.

Has there been any progress ever since?

The original post mentions a "transaction stream" proposal, has it been merged?