The problem is that "gcc -Werror=format-security" complains about a format string that's not a string literal even though the string in question is clearly and provably unchanged from when it came from a string literal one line before. That's a gcc bug, but nonetheless it's easy to work around.
CHANGE: http://review.gluster.com/3117 (Fix compiler warnings and typos from Debian build.) merged in master by Anand Avati (avati)
Fix in upstream, will verify later.