[Sbcl-devel] division-by-zero bug

[Gabriel D. R. <gd...@in...>]

The form exposes a bug in the SBCL DIVISION-BY-ZERO class.

;; --- cut here
(defun invert-x (x) (/ 1 x))

(defun handle-div-by-zero (c)
  (let ((op (arithmetic-error-operation c))
        (args (arithmetic-error-operands c)))
    (format *error-output* "op = ~A, args = ~A ~%" op args)
    (throw 'result "failed")))

(defun invert (x)
  (handler-bind ((division-by-zero #'handle-div-by-zero))
                (catch 'result (invert-x x))))

(invert 0)       ;; OK -- returns "failed"
(invert 0.0)     ;; KO -- drops into debugger

;; -- cut here


On gets dropped into the debugger:

debugger invoked on a SIMPLE-ERROR: unbound condition slot: SB-KERNEL::OPERANDS

Type HELP for debugger help, or (SB-EXT:QUIT) to exit from SBCL.

restarts (invokable by number or by possibly-abbreviated name):
  0: [ABORT] Exit debugger, returning to top level.

(SB-KERNEL::FIND-SLOT-DEFAULT
 #<SB-KERNEL::CONDITION-CLASSOID DIVISION-BY-ZERO>
 #S(SB-KERNEL::CONDITION-SLOT
    :NAME SB-KERNEL::OPERANDS
    :INITARGS (:OPERANDS)
    :READERS (ARITHMETIC-ERROR-OPERANDS)
    :WRITERS NIL
    :INITFORM-P NIL
    :INITFORM NIL
    :ALLOCATION :INSTANCE
    :CELL NIL
    :DOCUMENTATION NIL))
0]