On Maxima 5.11.0 GCL 2.6.8, internal errors look like this:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Maxima encountered a Lisp error:
Error in MACSYMA-TOP-LEVEL [or a callee]: ***the Lisp error message***
Automatically continuing.
To reenable the Lisp debugger set *debugger-hook* to nil.
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
Most of this is unnecessary or obscure for the ordinary (non-Lisp
programmer) user, and even for Maxima programmers (what use is the
Macsyma [sic] top level or a callee business?).
Could we change this to something like:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Maxima encountered an internal error:
***the Lisp error message***
This indicates a bug in Maxima; use bug_report() to report bugs.
To debug in Lisp, set *debugger-hook* to nil.
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
The last line is not helpful to most users, but I admit that I'd
forget the variable name myself if it weren't there, though better
might be:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Maxima encountered an internal error:
***the Lisp error message***
This indicates a bug in Maxima; use bug_report() to report bugs.
Lisp programmers: try debugging_advice().
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
Where debugging_advice could print out something useful.
It appears that the string "Error in ... [or a callee]" is part of the
'condition' object passed by GCL to Maxima. I don't know GCL well
enough to know how to control this. Do we have to do something silly
like string manipulation on the result to splice it out?
-s