I'm very interested in the question of logging libraries as well.

There are a few log4J ones out there. I've been using Log4cplus from sourceforge and a been happy enough with it for its simple purpose.

I personally agree. I've tried various different logging strategies including various types of macros and globally set log levels. However, I typically find that those approaches don't provide a sufficiently fine-grained approach when I debug code. (e.g., I might want some code to be hyperverbose and other bits to remain quiet). I like the additivity, hierarchical logger strategies of log4J et al. because they given a fairly fine-grained control over what gets logged and how. I've personally been using log4cpp (looks almost like log4cplus). It has two solutions to the issue of the cost of logging a message: 1. You can query the logger to see if the message would be logged if it were generated. Therefore, you can do things like: if (logger.isDebugEnabled()) logger.getDebugStream() << message ; (the stream support leaves a lot to be desired) 2. You can also log messages using printf-style commands: logger.debug("%s", message); These don't get evaluated unless the message is logged. Cheers, Simon