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 <<ghc: 9358352 bytes, Floating point exception

This is a divide-by-zero bug in the code that generates the stats, which I think I've fixed. You must have some custom heap settings that are triggering this though: is your GHC_RTS environment variable set to anything? Cheers, Simon