[Sbcl-devel] Bug?: out-of-extent RETURN fails poorly

[Kevin R. <kp...@ma...>]

I reduced a failure in a program I wrote to this:

   (funcall (catch 't (block nil (throw 't (lambda () (return))))))

I recognize that this is undefined per CLHS 5.2, but SBCL usually  
reports a decent error and doesn't corrupt itself for out-of-extent  
calls to RETURN[-FROM].

In the above case, it does not. On one of my machines:

* (funcall (catch 't (block nil (throw 't (lambda () (return))))))
... Unhandled memory fault at #x0.

* (list (lisp-implementation-version) (machine-type) (software-type))
("1.0.6" "X86" "Darwin")

(This was the error I originally hit in my program, and the backtrace  
did not have any informative frames sufficiently near to the  
erroneous return-from that I could find out that that was the problem  
other than by reducing the code. There did not seem to be any  
corruption; I was able to repeatedly load and test code without  
restarting that sbcl.)

On another machine:

* (funcall (catch 't (block nil (throw 't (lambda () (return))))))
fatal error encountered in SBCL pid 10537:
fault in heap page 94326 not marked as write-protected
boxed_region.first_page: 6231, boxed_region.last_page 6231
LDB monitor

...
* (list (lisp-implementation-version) (machine-type) (software-type))
("1.0.4" "PowerPC" "Darwin")

Here are some earlier variations of the test case which also fail  
poorly on at least one of the above systems:

(let (x)
   (handler-case
     (block nil
       (setf x (lambda () (return)))
       (error "bang"))
     (error ()))
   (funcall x))

(let (x)
   (block t
     (handler-bind ((error (lambda (c) (return-from t))))
       (block nil
         (setf x (lambda () (return)))
         (error "bang"))))
   (funcall x))

(let (x)
   (catch 't
       (block nil
         (setf x (lambda () (return)))
         (throw 't nil)))
   (funcall x))

I could not find a failure case which used no SIGNAL or THROW.

-- 
Kevin Reid                            <http://homepage.mac.com/kpreid/>