#8144: Interface hashes include time stamp of included .h file when CPP is used -------------------------------------------------+------------------------- Reporter: nh2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time performance bug | Unknown/Multiple Test Case: | Difficulty: Blocking: | Unknown | Blocked By: | Related Tickets: -------------------------------------------------+------------------------- Comment (by nh2): ''UsageFile'' was introduced with ''addDependentFile'' in https://github.com/ghc/ghc/commit/b994313. The modification time being only (obtained) in second resolution is what triggers the inconsistent behaviour. Regarding that commit, I am also not sure how https://github.com/ghc/ghc/commit/b994313#L3R1283 works: {{{ checkModUsage _this_pkg UsageFile{ usg_file_path = file, usg_mtime = old_mtime } = do new_mtime <- liftIO $ getModificationTime file return $ old_mtime /= new_mtime }}} I might be wrong, but it looks to me as if this can only ever return False (''UpToDate'' in current GHC head) '''because''' the mtime is so coarse - in other words if your computer is too slow, a second will pass and this will never be considered up to date? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8144#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler