A pathname designator.
An output stream,
log-bug-form opens the file log-file for output. It writes the current date followed by a bug form. The bug form contains description, and debugging information generated by the system. When it finishes it writes to the stream message-stream a single line reporting that a bug form was written.
If log-file is supplied it must be a valid path, and it is used to open the file. The default value of log-file is the value returned by executable-log-file.
log-bug-form is invoked automatically if the debugger decides to use the console (the terminal) rather than use the LispWorks IDE debugging tools. This means that after such an error the user can always find a bug form in the default log file, which can be found by using executable-log-file.
log-bug-form always appends, so if it is called frequently the log file grows continuously. You may need to clear it periodically. It may be a good idea to move the file rather than delete it, so a record of errors remains.
When editing the log file it should be noted that each bug form is preceded by the time it was written, and that the bug forms are in chronological order. That means that the interesting bug form is most often the last one in the file.
LispWorks User Guide and Reference Manual - 13 Feb 2015