When you are running a Solver program from a debugger, such as dbx or gdb, you can stop the execution on failures. A breakpoint can be set for the function ilc_fail_stop_here to stop the program after each call to IlcConstraintI::fail or IlcGoalI::fail. You do that like this:

(dbx) stop in ilc_fail_stop_here 
(gdb) break ilc_fail_stop_here

On some platforms, such as Windows NT® , for example, you must prefix an underscore to the name of the function, like this: _ilc_fail_stop_here.