···

       
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the library can't possible know that path when it's compiled, because the path

     

       
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GHC considers its own is determined only much later, when the user configures

     

       
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it through `ghcWithPackages`. So we [patched

     

       
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-
       
ghc-paths](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/haskell-modules/ghc-paths-nix.patch)

     

       
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+
       
ghc-paths](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/haskell-modules/patches/ghc-paths-nix.patch)

     

       
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to return the paths found in those environment variables at run-time rather

     

       
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than trying to guess them at compile-time.

     

       
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