#12056: Too aggressive `-w` option -------------------------------------+------------------------------------- Reporter: asr | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: #11429, #11789 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by wozgonon): Error appears to be in parsing of flags before DynFlags. See comment at end of ghc/compiler/main/CmdLineParser.hs {{{ errorsToGhcException errs = UsageError $ intercalate "\n" $ [ l ++ ": " ++ e | (l, e) <- errs ] {- Note [Handling errors when parsing commandline flags] Parsing of static and mode flags happens before any session is started, i.e., before the first call to 'GHC.withGhc'. Therefore, to report errors for invalid usage of these two types of flags, we can not call any function that needs DynFlags, as there are no DynFlags available yet (unsafeGlobalDynFlags is not set either). So we always print "on the commandline" as the location, which is true except for Api users, which is probably ok. When reporting errors for invalid usage of dynamic flags we /can/ make use of DynFlags, and we do so explicitly in DynFlags.parseDynamicFlagsFull. Before, we called unsafeGlobalDynFlags when an invalid (combination of) flag(s) was given on the commandline, resulting in panics (#9963). -} }}} The actual error displayed seems to originate from ghc/compiler/main/StaticFlags.hs which calls the above 'errorsToGhcException' in CmdLineParser.hs {{{ StaticFlags.hs:86: errorsToGhcException . map (("on the commandline", ) . unLoc) $ errs }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12056#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler