How can I put log statements into a browser plugin written for Mac OS X so that I can see them when the plugin is running?
Any printf you put in your browser plugin will eventually show up in the "console" application; however, recently that seems to take longer and longer and sometimes doesn't end up showing up at all.
I personally recommend logging to a file; the FireBreath project has built-in support for log4cplus so a lot of us use that, but there are plenty of logging statements.
Still, even just a printf will usually be visible if you look in the right place -- and that's the system log, which you can view by running Console.app (in Applications/Utilities)