This library does not define any procedures or syntax. Instead,
trace.ss is imported at the top-level for its
side-effects. The trace library installs a new load handler and load
extension handler to print information about the files that are
loaded. These handlers chain to the current handlers to perform the
actual loads. Trace output is printed to the port that is the current
error port when the library is loaded.
Before a file is loaded, the tracer prints the file name and ``time''
(as reported by the procedure current-process-milliseconds) when
the load starts. Trace information for nested loads is printed with
indentation. After the file is loaded, the file name is printed
with the ``time'' that the load completed.
If a _loader extension is loaded (see section 14.1 in PLT MzScheme: Language Manual), the
tracer wraps the returned loader procedure to print information about
libraries requested from the loader. When a library is found in the
loader, the thunk procedure that extracts the library is wrapped to
print the start and end times of the extraction.