Re: Stack traces

[Matt Wette <matt.wette@gmail.com>]

> On Feb 15, 2017, at 7:36 AM, Christopher Allan Webber <cwebber@dustycloud.org> wrote:
> 
> One thing that we see requested a lot is how to do the equivalent of:
> 
>  import pdb
>  pdb.set_trace()
> 
> in python, just dumping something to "trigger" the debugger somewhere.
> I seem to remember getting some arcane code to do something similar, but
> maybe we can just have a simple invocation that people could put
> anywhere.  (Amirouche has been raising this one also I think.)
> 

I am playing with this.  It does dump me into the debugger but the interaction is not wonderful (like pdb.set_trace()). 
However, this is context for working in that direction (i.e., pdb.set_trace()):

mwette$ cat trapper.scm 
(use-modules (system repl repl))
(use-modules (system repl debug))

(define-syntax-rule (trap-here)
  (start-repl
   #:debug (make-debug (stack->vector (make-stack #t)) 0 "trap!" #t)))

(define (foo)
  (let iter ((sum 0) (vals '(1 2 3 5 8 2)))
    (trap-here)
    (if (null? vals) sum
	(iter (+ sum (car vals)) (cdr vals)))))

(foo)

mwette$ guile
GNU Guile 2.0.13
[…]
scheme@(guile-user)> (load "trapper.scm")
[…]
scheme@(guile-user) [1]> ,bt
[…]
In /Users/mwette/proj/scheme/myproj/potluck/trapper.scm:
     10:4  1 (foo)
In unknown file:
           0 (make-stack #t)
scheme@(guile-user) [1]>