debug and backtrace

[Mike Gran <spk121@yahoo.com>]

Hi-

With the default behavior of 1.9.x, REPL debug and backtrace are broken.
Consider the following example run using 'guile --debug' and
(debug-enable 'backtrace).

With 1.8.5

--------------------------------------------------------
guile> (string-append "abc" (string-append "def" (string-append (error
"blammo"))))

Backtrace:
In standard input:
   2: 0* [string-append "abc" ...
   2: 1*  [string-append "def" ...
   2: 2*   [string-append ...
   2: 3*    [error "blammo"]

standard input:2:58: In procedure error in expression (error "blammo"):
standard input:2:58: blammo
ABORT: (misc-error)
guile> (debug)
This is the Guile debugger -- for help, type `help'.
There are 4 frames on the stack.

Frame 3 at standard input:2:58
	[error "blammo"]
debug> up
Frame 2 at standard input:2:43
	[string-append ...
debug> up
Frame 1 at standard input:2:22
	[string-append "def" ...
debug> up
Frame 0 at standard input:2:1
	[string-append "abc" ...
--------------------------------------------------------

With 1.9.x

--------------------------------------------------------
scheme@(guile-user)> (string-append "abc" (string-append
"def" (string-append (error "blammo"))))

Backtrace:
In unknown file:
   ?: 0* [#<vm a0389b8> #<program a272300 at standard input:1:0 ()>]
   ?: 1* [error "blammo"]

ERROR: In procedure error:
ERROR: blammo
scheme@(guile-user)> (debug)
This is the Guile debugger -- for help, type `help'.
There are 2 frames on the stack.

Frame 1 at unknown source location
	[error "blammo"]
debug> up
Frame 0 at unknown source location
	[#<vm a0389b8> #<program a272300 at standard input:1:0 ()>]
--------------------------------------------------------

Thanks,
Mike