[GHC] #8942: Duplicate symbol error when loading an archive twice

[GHC]

#8942: Duplicate symbol error when loading an archive twice
------------------------------------+-------------------------------
       Reporter:  gelisam           |             Owner:  simonmar
           Type:  bug               |            Status:  new
       Priority:  normal            |         Milestone:
      Component:  Runtime System    |           Version:  7.6.3
       Keywords:                    |  Operating System:  MacOS X
   Architecture:  Unknown/Multiple  |   Type of failure:  GHCi crash
     Difficulty:  Unknown           |         Test Case:
     Blocked By:                    |          Blocking:
Related Tickets:                    |
------------------------------------+-------------------------------
 ghci can load packages from object files (*.o) and from archive files
 (*.a). When an object file is loaded twice, the second attempt is silently
 ignored. When an archive file is loaded twice, ghci aborts with the
 message "fatal error: I found a duplicate definition for symbol ''s''",
 for the first symbol ''s'' in the archive.

 === Patch

 The attached patch changes {{{rts/Linker.c}}} so that loading an archive
 file twice silently ignores the second attempt, just like it does with
 object files.

 === Repro steps

 Install a package using Cabal 1.18.*, as that version only produces
 archives and not objects.

 Then, force ghci to load that package twice. One way to do this is to use
 hint inside ghci to load a value from the package.

 {{{
 $ ghci
 > import Hello
 > import Language.Haskell.Interpreter
 > r <- runInterpreter $ setImports ["Hello"] >> interpret "Hello" (as ::
 Hello)
 Loading package array-0.4.0.1 ... linking ... done.
 Loading package deepseq-1.3.0.1 ... linking ... done.
 Loading package containers-0.5.0.0 ... linking ... done.
 Loading package filepath-1.3.0.1 ... linking ... done.
 Loading package old-locale-1.0.0.5 ... linking ... done.
 Loading package time-1.4.0.1 ... linking ... done.
 Loading package bytestring-0.10.0.2 ... linking ... done.
 Loading package unix-2.6.0.1 ... linking ... done.
 Loading package directory-1.2.0.1 ... linking ... done.
 Loading package old-time-1.1.0.1 ... linking ... done.
 Loading package pretty-1.1.1.0 ... linking ... done.
 Loading package process-1.1.0.2 ... linking ... done.
 Loading package Cabal-1.16.0 ... linking ... done.
 Loading package binary-0.5.1.1 ... linking ... done.
 Loading package bin-package-db-0.0.0.0 ... linking ... done.
 Loading package hoopl-3.9.0.0 ... linking ... done.
 Loading package hpc-0.6.0.0 ... linking ... done.
 Loading package template-haskell ... linking ... done.
 Loading package ghc-7.6.3 ... linking ... done.
 Loading package utf8-string-0.3.8 ... linking ... done.
 Loading package transformers-0.3.0.0 ... linking ... done.
 Loading package hello-0.1.0.0 ... linking ... done.
 Loading package mtl-2.1.3.1 ... linking ... done.
 Loading package exceptions-0.3.3.1 ... linking ... done.
 Loading package extensible-exceptions-0.1.1.4 ... linking ... done.
 Loading package ghc-mtl-1.1.0.0 ... linking ... done.
 Loading package ghc-paths-0.1.0.9 ... linking ... done.
 Loading package random-1.0.1.1 ... linking ... done.
 Loading package hint-0.4.0.0 ... linking ... done.


 GHCi runtime linker: fatal error: I found a duplicate definition for
 symbol
    ___stginit_hellozm0zi1zi0zi0_Hello
 whilst processing object file
    /Users/gelisam/.cabal/lib/x86_64-osx-
 ghc-7.6.3/hello-0.1.0.0/libHShello-0.1.0.0.a
 This could be caused by:
    * Loading two different object files which export the same symbol
    * Specifying the same object file twice on the GHCi command line
    * An incorrect `package.conf' entry, causing some object to be
      loaded twice.
 GHCi cannot safely continue in this situation.  Exiting now.  Sorry.
 }}}

 A minimal definition for the hello package is attached, but doesn't
 contain anything relevant to the issue. It's just a dummy datatype:

 {{{#!haskell
 {-# LANGUAGE DeriveDataTypeable #-}
 module Hello where

 import Data.Typeable
 data Hello = Hello deriving Typeable
 }}}

 === Workaround
 Use Cabal 1.16, which (also) installs object files.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8942>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler