3.3 Using Debugger commands

3.3.4 Examining dynamic context markers

• a catch

The marker contains the name of a catch and its argument, which is the tag. You can specify a new argument to a catch just as you can to a local variable in the Debugger.

• anunwind-protect indicator

The marker contains an indicator thatunwind-protect forms exist;unwind-protect forms must be evaluated if you throw past them.

• a special binding

The marker contains the name of a special variable, the value that it had at the time of the binding, and the current value for that binding.

• The:bm command displays the list of function calls and dynamic context markers from the specified frame to the bottom of the stack.

• The:nm command moves down the stack by one frame or dynamic context marker.

• The:pm command moves up the stack by one frame or dynamic context marker.

;;; Define two functions that are linked by an incorrect
;;; catch and throw.
> (defun catcher ()
    (catch 'here (thrower)))
CATCHER

> (defun thrower ()
    (throw 'there t))
THROWER

> (compile 'catcher)
CATCHER

	> (catcher)
>>Error: Uncaught THROW to tag THERE
THROWER:
Original code: (NAMED-LAMBDA THROWER NIL 
(BLOCK THROWER (THROW # T)))
:A  0: Abort to Lisp Top Level

-> :bm
THROWER <- [:CATCH HERE] <- CATCHER <- EVAL

-> :nm
[:CATCH]:
   Catch 0 (TAG): HERE

-> :s 0 'there
-> :d
>>Error: Uncaught THROW to tag THERE
[:CATCH]:
   Catch 0 (TAG): THERE
:A  0: Abort to Lisp Top Level

-> :pm

THROWER:
Original code: (NAMED-LAMBDA THROWER NIL (BLOCK THROWER (THROW # T)))

-> :f

Re-executing (THROWER), OK? (Y or N): y
T
> 

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