It seems that if compilation is not required, or if compilation is very fast, ghc -Rghc-timing will throw up a Floating point exception: [hdaume@hal3 timing]$ ls Timing.hs [hdaume@hal3 timing]$ cat Timing.hs module Timing where timing = undefined [hdaume@hal3 timing]$ ghc -Rghc-timing Timing.hs -c <