Messages issued by syslog not showing up in system logs

Despite what you pass to setlogmask(), in its default configuration, OS X will only write messages to the system log that have a priority of LOG_NOTICE or higher.

Any of the following will solve your problem...

1. Enable lower-priority logging in /etc/syslog.conf -- kern.* is not enough, as log messages from Xcode are not coming from the kernel
2. Change the priority of your messages from LOG_DEBUG to LOG_NOTICE
3. Simply use the built-in Xcode console -- the output will always appear there regardless of your syslog.conf settings

Here's what it looks like in the built-in Xcode 4 console:

Also, if you're developing exclusively for OS X, you might want to look into ASL (Apple System Log), which was meant to replace syslog().