guile-debugging: how to access source properties from trap context

[Holger Blasum]

Hello guile-user,

in the "Guile Debugging Enhancements" tutorial 
(http://download.gna.org/guile-debugging/guile-debugging.html)
there is encouragement to play with the source trap context
parameters. 

What I want to look at are the source file names and 
line numbers like eg in any gdb stepping session of a C program
say for matrix multiplication like: 

gdb -f a.out
(gdb) br main
Breakpoint 1 at 0x8048417: file matrix.c, line 11.
(gdb) run
Starting program: /home/blasum/a/comp/sema/sample/c/samples/a.out 
/home/blasum/a/comp/sema/sample/c/samples/matrix.c:12
(gdb) step
/home/blasum/a/comp/sema/sample/c/samples/matrix.c:13
(gdb) step
/home/blasum/a/comp/sema/sample/c/samples/matrix.c:14
(gdb) step
...

How can one access file name and line number of the source
properties in guile-debugging?

My first shot was at 

$ guile
guile> (use-modules (ice-9 debugger) (ossau 
        ice-9-debugger-extensions) (ossau traps) (ossau trace))
guile> (load "matrix.scm")
guile> (define (report-exp trap-context)
    (display "Expression: ")
    (display (tc:expression trap-context))
    (newline))
guile> (install-trap (make <procedure-trap> #:procedure mkmatrix
#:behaviour (list report-exp)))
guile> (do-main 4)
Expression: #f
Expression: #f
guile>

However expression (#f might be ok, because we are dealing 
with vectors, and it *is* called twice) is the wrong 
attribute what I'm really looking for is not the evaluated 
expression (nor its uninterpreted source text) but its
source text's file name and line number ;) 

Any hints (even if they involve twiddling with traps.scm) very 
welcome ... (Credits for the matrix multiplication sample 
are to Peter Williams, matrix multiplication is not really 
what I am interested in but is perhaps a good example for 
testing a stepper.)

Happy 2006,

-- 
Holger Blasum +49-174-7313590 (gsm) GnuPG 1024D/ACDFC3B769DC1ED66B47
"It has turned out that the networking of many small computers, at many 
places, is more efficient than the one supercomputer - the success of 
the internet is based on this principle." - Angela Merkel, government
declaration, 30 Nov 2005

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