Passing flags to functions

I want to put this up for discussion. Is there a better way to pass flags to C functions than registering constants like SYSLOG_*, EXTR_*, etc. and then comparing the passed flag value to the internal #define with the same name? What if I want to pass flags that can be OR'ed together? Any ideas on how to make it work better? -Andrei "Hack: 1. n. Originally, a quick job that produces what is needed, but not well. 2. n. An incredibly good, and perhaps very time-consuming, piece of work that produces exactly what is needed." -- Jargon File