Compiler bug

[Raymond Toy]

Reported on cmucl-imp, 2008-10-31

(declaim (optimize (speed 0) (safety 3) (debug 3)))

(defun test-pop-and-return ()
  (loop
    (pop *random-stack*)
    (return)))

When compiled, this causes an internal compiler error from STACK-ANALYZE.

The error happens because NODE-PREV returns NIL instead of a node.

[Raymond Toy]

A related bug

(defun foo2 ()
  (catch (make-symbol "CMUCL-DEBUG-CATCH-TAG")
    (make-string 49)))

Same results: STACK-ANALYZE crashes because NODE-PREV is NIL.

[Raymond Toy]

Replying to rtoy:

Correction:

(declaim (optimize (safety 3)))

(defun foo2 ()
  (catch (make-symbol "CMUCL-DEBUG-CATCH-TAG")
    (make-string 49)))

There's no problem if safety < 3.

[Raymond Toy]

Both of these should be fixed in the 2008-12 snapshot.

I think the compiler was trying not to delete dead code when SAFETY = 3, but was erroneous linking continuations together. Now we do nothing in this case. The dead code remains and is executed and the results are never used. The above examples work fine, and the case of (progn (fboundp 42) t) still works (fboundp triggers an error instead of being deleted as dead code.)