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Re: frames / stacks / source? was Re: coverage/profiling

From: Han-Wen Nienhuys
Subject: Re: frames / stacks / source? was Re: coverage/profiling
Date: Wed, 10 Jan 2007 13:59:56 +0100
User-agent: Thunderbird (X11/20061219)

Neil Jerram escreveu:
>>> Do you think you need to do this in C?  (You might do, for reasonable
>>> performance - I genuinely don't know yet.)  The evaluator already has
>>> hooks (see "Evaluator trap options" in the manual) that allow you to
>>> call out to arbitrary Scheme code at the entry and exit of every
>>> frame.
>> address@hidden info]$ guile
>> guile> (trap-enable 'enter-frame-handler)
>> throw from within critical section.
>> Abortado
>> address@hidden info]$ 
> Takes effect quickly, doesn't it? :-)
> What you need is something more like this:
> (trap-set! enter-frame-handler
>   (lambda (key continuation . args)
>     ...))
> (trap-enable 'enter-frame)
> And it's important to do them in this order.


perhaps the documentation could be extended to include a small example,
such as

"The following example demonstrates the use of traps. The program
displays each source line as it is executed, by installing a handler
that examines the origin of each continuation.  The handlers are
installed and enabled with @code{trap-set!} and @code{trap-enable},
but they only become active if traps are switched on with
@code{(trap-enable 'traps)}.

(define (test-add x y)

(define (record-coverage key continuation . args)
      ((stack (make-stack continuation))
       (frame (stack-ref stack 0))
       (source (frame-source frame))
       (line (and source (source-property source 'line))))
    (if (and line (< line 10))
        (format #t "line ~a ~a ~a \n"  (1+ line) key args))))

(trap-set! apply-frame-handler record-coverage)
(trap-set! enter-frame-handler record-coverage)
(trap-set! exit-frame-handler record-coverage)

(trap-enable 'apply-frame 'exit-frame 'enter-frame)

(trap-enable 'traps)

(define z (test-add 1 2))

(trap-disable 'traps)

when this is put in a file and executed with --debug, the following
is shown

line 2 enter-frame (#t (+ x (/ x y))) 
line 4 enter-frame (#f (/ x y)) 
line 4 apply-frame (#f) 
line 4 exit-frame (1/2) 
line 2 apply-frame (#t) 
line 2 exit-frame (3/2) 


(I'm not sure what the #f / #t mean, though)      

 Han-Wen Nienhuys - address@hidden -

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