gistfile1.txt

diff --git a/default.nix b/default.nix
index b1f7ba5..a0104b8 100644
--- a/default.nix
+++ b/default.nix
@@ -7,8 +7,8 @@
 { nixpkgs   ? import <nixpkgs> {}
 , bootghc   ? "ghc844"
 , version   ? "8.7"
-, useClang  ? false  # use Clang for C compilation
-, withLlvm  ? false
+, useClang  ? true # use Clang for C compilation
+, withLlvm  ? true
 , withDocs  ? true
 , withDwarf ? nixpkgs.stdenv.isLinux  # enable libdw unwinding support
 , withNuma  ? nixpkgs.stdenv.isLinux
@@ -21,7 +21,7 @@ with nixpkgs;
 let
     stdenv =
       if useClang
-      then nixpkgs.clangStdenv
+      then nixpkgs.llvmPackages_7.stdenv
       else nixpkgs.stdenv;
     noTest = pkg: haskell.lib.dontCheck pkg;
 
@@ -43,9 +43,10 @@ let
         cabal-install
         zlib.out
         zlib.dev
+        lld
       ]
       ++ docsPackages
-      ++ stdenv.lib.optional withLlvm llvm_6
+      ++ stdenv.lib.optional withLlvm llvm_7
       ++ stdenv.lib.optional withNuma numactl
       ++ stdenv.lib.optional withDwarf elfutils ;