title: GHCI: I found a duplicate definition for symbol _fps_count
body: <p><strong>tl;dr:</strong> It seems like <code>Network.HTTP</code> and <code>Data.Aeson</code> are not compatible with each other. How would I begin working around this?</p>
  
  <p><strong>Long version:</strong> I think I narrowed this down as much as possible. I started with a fresh cabal sandbox and now am getting a runtime linker fatal error.</p>
  
  <p>Here's my code:</p>
  
  <pre><code>-- test.hs
  import Network.HTTP (simpleHTTP, getRequest, getResponseBody, postRequestWithBody)
  import Data.Aeson
  
  main = print "hi"
  </code></pre>
  
  <p>And here's how I get the error, from the very first command:</p>
  
  <pre><code>$ cabal --version
  cabal-install version 1.20.0.3
  $ cabal sandbox init
  ...
  $ cabal install aeson
  ...
  $ cabal repl
  GHCi, version 7.6.3: http://www.haskell.org/ghc/  :? for help
  Loading package ghc-prim ... linking ... done.
  Loading package integer-gmp ... linking ... done.
  Loading package base ... linking ... done.
  Prelude&gt; :load test.hs
  [1 of 1] Compiling Main             ( test.hs, interpreted )
  Ok, modules loaded: Main.
  *Main&gt; main
  Loading package array-0.4.0.1 ... linking ... done.
  Loading package deepseq-1.3.0.1 ... linking ... done.
  Loading package primitive-0.5.0.1 ... linking ... done.
  Loading package vector-0.10.0.1 ... linking ... done.
  Loading package bytestring-0.10.0.2 ... linking ... done.
  Loading package transformers-0.3.0.0 ... linking ... done.
  Loading package mtl-2.1.2 ... linking ... done.
  Loading package text-0.11.3.1 ... linking ... done.
  Loading package parsec-3.1.3 ... linking ... done.
  Loading package old-locale-1.0.0.5 ... linking ... done.
  Loading package time-1.4.0.1 ... linking ... done.
  Loading package unix-2.6.0.1 ... linking ... done.
  Loading package network-2.4.1.2 ... linking ... done.
  Loading package old-time-1.1.0.1 ... linking ... done.
  Loading package HTTP-4000.2.8 ... linking ... done.
  Loading package containers-0.5.0.0 ... linking ... done.
  Loading package bytestring-0.10.4.0 ... 
  
  GHCi runtime linker: fatal error: I found a duplicate definition for symbol
     _fps_count
  whilst processing object file
     /Users/tapwater/p/haskell/stellar/.cabal-sandbox/lib/x86_64-osx-ghc-7.6.3/bytestring-0.10.4.0/libHSbytestring-0.10.4.0.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.
  </code></pre>
  
  <p>If I comment out either one of the import statements, everything works fine.</p>
  
  <p>Am I (hopefully) doing something wrong? Or are these two libraries entirely incompatible?</p>