Linking error compiling Cabal with custom snapshot

[hesselink]

This issue is similar to #1110 but that one is fixed for me, and this isn't. If I compile Cabal-1.22.4.0 on a custom snapshot based on ghc-7.8 which includes a newer unix than comes with that ghc (2.7.1.0 instead of 2.7.0.1), there is an error linking the setup executable for Cabal:

--  While building package Cabal-1.22.4.0 using:
      /usr/local/bin/ghc --make -odir /tmp/stack31011/Cabal-1.22.4.0/.stack-work/dist/x86_64-linux/Cabal-1.18.1.3/setup/ -hidir /tmp/stack31011/Cabal-1.22.4.0/.stack-work/dist/x86_64-linux/Cabal-1.18.1.3/setup/ -i -i. -package=Cabal-1.18.1.3 -clear-package-db -global-package-db -package-db=/home/erik/.stack/snapshots/x86_64-linux/custom-silk-2015-09/7.8.3/pkgdb/ /tmp/stack31011/Cabal-1.22.4.0/Setup.hs -o /tmp/stack31011/Cabal-1.22.4.0/.stack-work/dist/x86_64-linux/Cabal-1.18.1.3/setup/setup
    ...
    <snip compiling modules>
    ....
    Linking /tmp/stack31011/Cabal-1.22.4.0/.stack-work/dist/x86_64-linux/Cabal-1.18.1.3/setup/setup ...
    /usr/local/lib/ghc-7.8.3/unix-2.7.0.1/libHSunix-2.7.0.1.a(execvpe.o): In function `pPrPr_disableITimers':
    execvpe.c:(.text+0x340): multiple definition of `pPrPr_disableITimers'
    /home/erik/.stack/snapshots/x86_64-linux/custom-silk-2015-09/7.8.3/lib/x86_64-linux-ghc-7.8.3/unix-2.7.1.0/libHSunix-2.7.1.0.a(ghcrts.o):(.text+0x0): first defined here

The weird thing is that this only happens on linux (Ubuntu 14.04.1 LTS), not on Mac. I've uploaded a reproduction here. Further information: stack Version 0.1.6.0, Git revision e22271f5ce9afa2cb5be3bad9cafa392c623f85c (2313 commits) x86_64, ghc 7.8.3.

/usr/local/lib/ghc-7.8.3/package.conf.d
   Cabal-1.18.1.3
   HTTP-4000.2.12
   HTTP-4000.2.16.1
   QuickCheck-2.7.6
   array-0.5.0.0
   base-4.7.0.1
   bin-package-db-0.0.0.0
   binary-0.7.1.0
   bytestring-0.10.4.0
   containers-0.5.5.1
   cpphs-1.18.5
   deepseq-1.3.0.2
   directory-1.2.1.0
   filepath-1.3.0.2
   ghc-7.8.3
   ghc-prim-0.3.1.0
   haskeline-0.7.1.2
   haskell2010-1.1.2.0
   haskell98-2.0.0.3
   hoopl-3.10.0.1
   hpc-0.6.0.1
   integer-gmp-0.5.1.0
   mtl-2.1.3.1
   network-2.4.2.3
   old-locale-1.0.0.6
   old-time-1.1.0.2
   parsec-3.1.5
   polyparse-1.9
   pretty-1.1.1.1
   primitive-0.5.3.0
   process-1.2.0.0
   random-1.0.1.1
   rts-1.0
   setenv-0.1.1.1
   stm-2.4.3
   tar-0.4.0.1
   template-haskell-2.9.0.0
   terminfo-0.4.0.0
   text-1.1.0.1
   tf-random-0.5
   time-1.4.2
   transformers-0.3.0.0
   unix-2.7.0.1
   xhtml-3000.2.1
   zlib-0.5.4.1

[borsboom]

Thanks for the detailed report. I am able to reproduce this locally with stack-0.1.8.0 as well.

[borsboom]

@mgsloan: since you're working on changes to custom snapshots already, can you look into this?

[mgsloan]

Sure! Should be possible to work on this in the next couple weeks.

[mgsloan]

Downgrading to P2 since it doesn't seem to affect many people. Still something to keep in mind for the custom snapshots revamp.

[mgsloan]

@hesselink I believe this is now fixed. The issue was that when building Cabal-1.22's Setup.hs, it was linking against Cabal-1.18. I've added a special case for this.