Re: [GHC] #8527: The ordering of -I directives should be consistent with the ordering of -package directives (was: container's Typeable.h is being shadowed by base's Typeable.h during preprocessing)

#8527: The ordering of -I directives should be consistent with the ordering of -package directives -------------------------------------+------------------------------------- Reporter: parcs | Owner: parcs Type: bug | Status: new Priority: normal | Milestone: Component: Package | Version: 7.7 system | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Old description:

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/home/patrick/code/ghc/libraries/base/include/Typeable.h:17:2: warning: #warning is obsolete and will be removed in GHC 7.10 [-Wcpp] #warning is obsolete and will be removed in GHC 7.10 ^ compilation IS NOT required $ ghc-stage2 -c -package base -package containers cpp.hs compilation IS NOT required $ ghc-stage2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?

New description: 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In file included from cpp.hs:4:0: /home/patrick/code/ghc/libraries/base/include/Typeable.h:17:2: warning: #warning is obsolete and will be removed in GHC 7.10 [-Wcpp] #warning is obsolete and will be removed in GHC 7.10 ^ compilation IS NOT required $ ghc-stage2 -c -package base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 unintuitive 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? -- Comment (by thomie): Work has started: {{{ commit 574ccfa231ca05d03d1da9d31e5bc81e74cc5e1e Author: Patrick Palka Date: Tue Nov 26 11:46:59 2013 -0500 Respect the ordering of -package directives }}} But that commit was later reverted in fac831fd1377bcce5ef7513ab35a83661877f14c. With `ghc-7.9.20141115`, the warning from the description is always shown, regardless of the ordering of the package directives. So something ''has'' changed. Note: "Typeable.h" might be removed when you read this. That doesn't mean that this issue is fixed though. A test should be added as well. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8527#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler