a couple bugs related to error reporting and backtraces

["Jose A. Ortega Ruiz" <jao@gnu.org>]

Hi,

I've got this trivial module definition in file a.scm:

  (define-module (a)
    #:export (ap))

  (define (ap) (not-bound))
  (ap)

intended to cause an error upon calling `ap'.

First bug is when trying to `load-compiled' a non-go file:

  scheme@(guile-user)> (load-compiled "./a.scm")

  Backtrace:
  In unknown file:
     ?: 0* [#<vm b7ade680> #<program b798ec20 at <unknown port>:0:0 ()>]
     1: 1* [#<program b798ec20 at <unknown port>:0:0 ()>]
     ?: 2* [load-compiled/vm "./a.scm"]

  ERROR: In procedure make_objcode_by_mmap:
  ERROR: Success
  scheme@(guile-user)>

As you can see, the error key, Success, is not correct. This happens
with any non-go file (so the contents above is not relevant).

So let's compile and load the real file:

  scheme@(guile-user)> ,i (system base compile)
  scheme@(guile-user)> (load-compiled (compile-file "/home/jao/tmp/a.scm"))

  Backtrace:
  In unknown file:
     ?: 0* [#<vm b7a8a680> #<program b793ed70 at <unknown port>:1:0 ()>]
     2: 1* [#<program b793ed70 at <unknown port>:1:0 ()>]
     ?: 2* [load-compiled/vm "/home/jao/.guile-ccache/1.9//home/jao/tmp/a.scm.go"]
     ?: 3* [ap]

  ERROR: In procedure module-lookup:
  ERROR: unbound variable: not-bound
  scheme@(a)>

As you can see, the location of the error is not reported; with the same
behaviour when calling the program interactively:

  scheme@(a)> ap
  #<program ap ()>
  scheme@(a)> (ap)

  Backtrace:
  In unknown file:
     ?: 0* [#<vm b7a8a680> #<program b6f102f0 at <unknown port>:3:0 ()>]
     ?: 1* [ap]

  ERROR: In procedure module-lookup:
  ERROR: unbound variable: not-bound
  scheme@(a)> 

Adding the directory containing a.scm to Guile's load path changes
nothing. What i was expecting is a backtrace pointing me to the location
of the call to `not-bound' in a.scm. Am i doing something wrong?

Thanks!
jao