error-handling bug

[Raymond Toy]

From an email on cmucl-help from Matt Kaufmann on 2014/07/26.

It appears to be the same bug as this SBCL bug (now fixed for SBCL):

​https://bugs.launchpad.net/sbcl/+bug/1333327

Here is a log illustrating the bug in the CMUCL versions mentioned above. The expected behavior is shown later below (using SBCL 1.2.1).

.......... CMUCL 20e and also 2014-06 snapshot: ..........

* (defun read-string-fn (str)
     (handler-case
       (let ((acc nil))
         (with-input-from-string
           (stream str)
           (loop do
                 (let* ((eof-marker (cons nil nil))
                        (elem (read stream nil eof-marker)))
                   (if (eq elem eof-marker)
                       (loop-finish)
                     (push elem acc)))))
         (setq acc (nreverse acc))
         (values :OK acc))
       (error (condition)
              (return-from read-string-fn
                (values :ERROR (format nil "~A" condition))))
       (storage-condition (condition)
                          (return-from read-string-fn
                            (values :STORAGE (format nil "~A" condition))))))

READ-STRING-FN
* (read-string-fn "#\wtf")


Error in function LISP::CLOSED-FLAME:  #<String-Input Stream> is closed.
   [Condition of type SIMPLE-ERROR]

Restarts:
  0: [ABORT] Return to Top-Level.

Debug  (type H for help)

(LISP::CLOSED-FLAME #<String-Input Stream>)
Source: Error finding source: 
Error in function DEBUG::GET-FILE-TOP-LEVEL-FORM:  Source file no longer exists:
  target:code/stream.lisp.
0] 

..........

Here is the analogous log after defining the function above in SBCL 1.2.1, which I believe is as expected.

.......... SBCL 1.2.1 ..........

* (read-string-fn "#\wtf")

:ERROR
"no dispatch function defined for #\\W

  Stream: #<SB-IMPL::STRING-INPUT-STREAM {1002E27C03}>"
* 

[Raymond Toy]

Link to the actual message: ​http://article.gmane.org/gmane.lisp.cmucl.general/6515

[toy.raymond@…]

commit c0052f5544d27980c74d5a17cd55dc2069085602 Author: Raymond Toy <toy.raymond@…> Date: Sat Aug 9 12:53:57 2014 -0700

Fix ticket:105 by not flaming out on a closed stream.

• code/reader.lisp:
  • The READER-ERROR condition tries to be helpful and print out the position of where the error occurred using FILE-POSITION. But FILE-POSITION flames out when the stream is closed, so check for a closed stream before calling FILE-POSITION

• tests/trac.lisp:
  • Add test from the bug report.

• general-info/release-20f.txt:
  • Update.