mask had been added before to the list of allowed ones.
For example,
+
\begin{verbatim}
// wxTraceOleCalls is one of standard bit masks
wxLogTrace(wxTraceRefCount | wxTraceOleCalls, "Active object ref count: %d", nRef);
\end{verbatim}
will do something only if the current trace mask contains both
{\tt wxTraceRefCount} and {\tt wxTraceOle}, but
+
\begin{verbatim}
// wxTRACE_OleCalls is one of standard string masks
wxLogTrace(wxTRACE_OleCalls, "IFoo::Bar() called");
\end{verbatim}
+
will log the message if it was preceded by
+
\begin{verbatim}
wxLog::AddTraceMask(wxTRACE_OleCalls);
\end{verbatim}