[GHC] #8572: Building an empty module with profiling requires profiling libraries for integer-gmp

[GHC]

#8572: Building an empty module with profiling requires profiling libraries for
integer-gmp
-------------------------------------------+-------------------------------
       Reporter:  parcs                    |             Owner:
           Type:  bug                      |            Status:  new
       Priority:  normal                   |         Milestone:
      Component:  Compiler (Type checker)  |           Version:  7.7
       Keywords:                           |  Operating System:
   Architecture:  Unknown/Multiple         |  Unknown/Multiple
     Difficulty:  Unknown                  |   Type of failure:
     Blocked By:                           |  None/Unknown
Related Tickets:                           |         Test Case:
                                           |          Blocking:
-------------------------------------------+-------------------------------
 {{{
 #!haskell
 {-# LANGUAGE NoImplicitPrelude #-}
 module A where
 }}}

 {{{
 $ ghc-stage2 -prof -c A.hs

 Top level:
     Failed to load interface for ‛GHC.Integer.Type’
     Perhaps you haven't installed the profiling libraries for package
 ‛integer-gmp’?
     Use -v to see a list of the files searched for.
 }}}

 I can't built module `A` without profiling libraries for `integer-gmp`,
 even though I don't use `integer-gmp` anywhere in the module.

 This happens because the `Tidy Core` pass attempts to look up the
 `mkInteger` name (in order to desugar integer literals) even when there
 are no integer literals in the module.

 The obvious fix is to lazily look up `mkInteger` in
 `Coreprep.lookupMkIntegerName`:

 {{{
 #!diff
 diff --git a/compiler/coreSyn/CorePrep.lhs b/compiler/coreSyn/CorePrep.lhs
 index 5e0cd65..9836982 100644
 --- a/compiler/coreSyn/CorePrep.lhs
 +++ b/compiler/coreSyn/CorePrep.lhs
 @@ -56,6 +56,7 @@ import Config
  import Data.Bits
  import Data.List        ( mapAccumL )
  import Control.Monad
 +import System.IO.Unsafe ( unsafeInterleaveIO )
  \end{code}

  --
 ---------------------------------------------------------------------------
 @@ -1119,6 +1120,7 @@ lookupMkIntegerName dflags hsc_env
        else if thisPackage dflags == integerPackageId
        then return $ panic "Can't use Integer in integer"
        else liftM tyThingId
 +         $ unsafeInterleaveIO
           $ initTcForLookup hsc_env (tcLookupGlobal mkIntegerName)

  mkInitialCorePrepEnv :: DynFlags -> HscEnv -> IO CorePrepEnv

 }}}

 This way, we don't attempt to look up `mkInteger` until we actually need
 it, i.e. if there are integer literals that we must desugar.

 Relevant commits are 2ef5cd26db27543ac8664a3d18f45550d0109a8b and
 fdd552e0ecaa17300670a48562995040e1d6687e

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8572>
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