I was avoiding using mudflap for a while due to the high volume of violations that I could not explain. Recently, they all disappeared which made me happy and I started using mf. I got zero violations since. When I had time to think about it I figured this just cannot be true. I have now confirmed that using -fmudflapth causes most of the checks to not happen. -fmudflap seems to have all checks done. In the past -fmudflapth did the job. Something changed. The help suggests that the two options have a function but it is not clear (to me) what it is. Attached is a sample that demonstrates how a simple violation is missed when -fmudflapth is used (the program does not use threads). -- Eyal Lebedinsky (eyal@eyal.emu.id.au)