trace() - sets trace flags and returns the old ones.
int trace( int traceflags );
Sets the trace flags and returns the old trace flags. When tracing is on a lot of information is printed during execution. The trace bits are: Trace all function calls to lfuns. Trace all calls to "call_other". Trace all function returns. Print arguments at function calls and return values. Print all executed stack machine instructions (produces a lot of out‐ put!). Enable trace in heart beat functions. Trace calls to apply. Show object name in tracing.