Break when encountering a hard or soft error caused by ACL2
(break-on-error t) ; installs a trace causing a continuable error (break)
; when an error is invoked by ACL2.
(break-on-error) ; same as above
(break-on-error :all) ; same as above, but even when inside the prover
(break-on-error nil) ; uninstall any above trace
(Break-on-error) generates a suitable trace of error functions.
Evaluate (trace$) after (break-on-error) if you want to see the
specific trace forms (which you can modify and then submit directly to
trace$, if you wish). This trace should cause entry to the Lisp
debugger whenever ACL2 calls its error routines, except for certain errors
when inside the theorem prover, and also at those times if option :all is
NOTE: For technical reasons, you may see some error messages more than
Finally, note that you are welcome to define your own version of
break-on-error by modifying a copy of the source definition (search for
``(defmacro break-on-error'' in ACL2 source file other-events.lisp).
Please feel free to send your version of break-on-error to the ACL2
implementors, for possible inclusion into ACL2.
Break-on-error is implemented using ACL2 trace$. See trace! if you want an explanation of the ``TTAG NOTE'' that is
The argument, if supplied, is evaluated and must evaluate to t,
nil, or :all.
Also see set-debugger-enable for how to get raw-Lisp backtrace
information when an error occurs as a result of break-on-error, or even
of a raw Lisp error, by calling set-debugger-enable with argument
:bt, :bt-break, or :break-bt. Note that for ACL2 errors (as
opposed to raw Lisp errors), i.e. errors affected by break-on-error, all
three of those keyword values are treated equivalently (and, all are ignored
for non-ANSI GCL; see set-debugger-enable).