#8527: container's Typeable.h is being shadowed by base's Typeable.h during preprocessing ------------------------------------+------------------------------------- Reporter: parcs | Owner: parcs Type: bug | Status: new Priority: normal | Milestone: Component: Package system | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Here's a reduced test case: == cpp.hs == {{{ #!haskell {-# LANGUAGE CPP #-} #include "Typeable.h" main = return () }}} == command line == {{{ $ ghc-stage2 -c -package base cpp.hs In file included from cpp.hs:4:0: /home/patrick/code/ghc/libraries/base/include/Typeable.h:17:2: warning: #warning <Typeable.h> is obsolete and will be removed in GHC 7.10 [-Wcpp] #warning <Typeable.h> is obsolete and will be removed in GHC 7.10 ^ compilation IS NOT required $ ghc-stage2 -c -package base -package containers cpp.hs compilation IS NOT required $ ghc-stage2 -c -package containers -package base cpp.hs }}} Notice that if I pass `-package containers` to ghc, the cpp warning from Typeable.h (from the base library) doesn't appear. This is because containers also has a Typeable.h in its include path, and in the invocation of the preprocessor, containers' include path precedes base's no matter how I order the `-package` directives. This behavior is intuitive and limiting. To fix this, I think that the ordering of -I directives passed to the preprocessor should be consistent with the ordering of -package directives passed to ghc. For example, in the above test case, a warning should be shown in the 1st and 2nd invocations of ghc but not the 3rd, because in the 3rd invocation containers precedes base. Does this sound okay? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8527> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler