Re: [Chicken-hackers] [PATCH] Fix #1620 by ignoring captured state of replaced variables

[megane]

megane <address@hidden> writes:

> Peter Bex <address@hidden> writes:
>
> Regarding the capturing, the capture test is still there:
>
>
>>       (when (and value (not global))
>>         (when (eq? '##core#variable (node-class value))
>> -         (let* ((name (first (node-parameters value)))
>> -                (nrefs (db-get db name 'references)) )
>> +         (let ((name (first (node-parameters value))) )
>>             (when (and (not captured)
>                           ^^^^^^^^^^^^^^
>                           Here.
> I got the impression you wanted to remove this.
>

Of course if this is dropped the other conditions must still meet.

Here's your proposed condition:

  (and (not captured)
       (or (and (not (db-get db name 'unknown))
                (db-get db name 'value))
           (and (not assigned)
                (not (db-get db name 'assigned))
                (or (not (variable-visible?
                          name block-compilation))
                    (not (db-get db name 'global))) )
              ))


If the (not captured) part is just dropped then if the first branch of
the or is taken, namely this:

  (and (not (db-get db name 'unknown))
       (db-get db name 'value))

then it's not checked that the variable to be replaced is never assigned
to! Here's a case that triggers the error:

  (define (foo x)
    (letrec ((pe* (lambda () (print x) (pe*))))
      (pe*)))
  (foo '((foo1 e)))
  (foo 'foo2)

The letrec expands to an assignment and to a (##core#undefined) that
triggers the first branch of the or.

Here's a correct way to drop the (not captured) check:

  (and (not assigned)
       (or (and (not (db-get db name 'unknown))
                (db-get db name 'value))
           (and (not (db-get db name 'assigned))
                (or (not (variable-visible?
                          name block-compilation))
                    (not (db-get db name 'global))) ) ))