Try #1405:

builder/comp-builder.nix

@@ -382,18 +382,26 @@ let
       runHook postConfigure
     '';
 
-    buildPhase = if stdenv.hostPlatform.isGhcjs then ''
-      runHook preBuild
-      # https://gitlab.haskell.org/ghc/ghc/issues/9221
-      $SETUP_HS build ${haskellLib.componentTarget componentId} ${lib.concatStringsSep " " setupBuildFlags}
-      runHook postBuild
-    '' else ''
-      runHook preBuild
-      # https://gitlab.haskell.org/ghc/ghc/issues/9221
-      $SETUP_HS build ${haskellLib.componentTarget componentId} -j$(($NIX_BUILD_CORES > 4 ? 4 : $NIX_BUILD_CORES)) ${lib.concatStringsSep " " setupBuildFlags}
-      runHook postBuild
-    ''
-    ;
+    buildPhase =
+      # It seems that by the time the iserv wrapper specifiec by `--ghc-option=-pgmi` runs
+      # all the array environment variables are removed from the environment.  To get a list
+      # of all the locations a DLLs might be present we need access to pkgsHostTarget.
+      # Adding a string version of the list array of nix store paths allows us to get that
+      # list when we need it.
+      (lib.optionalString stdenv.hostPlatform.isWindows ''
+        export pkgsHostTargetAsString="''${pkgsHostTarget[@]}"
+      '') +
+      (if stdenv.hostPlatform.isGhcjs then ''
+        runHook preBuild
+        # https://gitlab.haskell.org/ghc/ghc/issues/9221
+        $SETUP_HS build ${haskellLib.componentTarget componentId} ${lib.concatStringsSep " " setupBuildFlags}
+        runHook postBuild
+      '' else ''
+        runHook preBuild
+        # https://gitlab.haskell.org/ghc/ghc/issues/9221
+        $SETUP_HS build ${haskellLib.componentTarget componentId} -j$(($NIX_BUILD_CORES > 4 ? 4 : $NIX_BUILD_CORES)) ${lib.concatStringsSep " " setupBuildFlags}
+        runHook postBuild
+      '');
 
     # Note: Cabal does *not* copy test executables during the `install` phase.
     #

overlays/mingw_w64.nix

@@ -28,7 +28,19 @@ let
     unset configureFlags
     PORT=$((5000 + $RANDOM % 5000))
     (>&2 echo "---> Starting remote-iserv on port $PORT")
-    WINEDLLOVERRIDES="winemac.drv=d" WINEDEBUG=warn-all,fixme-all,-menubuilder,-mscoree,-ole,-secur32,-winediag WINEPREFIX=$TMP ${wine}/bin/wine64 ${remote-iserv}/bin/remote-iserv.exe tmp $PORT &
+    REMOTE_ISERV=$(mktemp -d)
+    ln -s ${remote-iserv}/bin/* $REMOTE_ISERV
+    for p in $pkgsHostTargetAsString; do
+      find "$p" -iname '*.dll' -exec ln -s {} $REMOTE_ISERV \;
+      find "$p" -iname '*.dll.a' -exec ln -s {} $REMOTE_ISERV \;
+    done
+    (
+    cd $REMOTE_ISERV
+    for l in lib*.dll; do
+      if [[ ! -e "''${l#lib}" ]]; then ln -s "$l" "''${l#lib}"; fi
+    done
+    )
+    WINEDLLOVERRIDES="winemac.drv=d" WINEDEBUG=warn-all,fixme-all,-menubuilder,-mscoree,-ole,-secur32,-winediag WINEPREFIX=$TMP ${wine}/bin/wine64 $REMOTE_ISERV/remote-iserv.exe tmp $PORT &
     (>&2 echo "---| remote-iserv should have started on $PORT")
     RISERV_PID="$!"
     ${iserv-proxy}/bin/iserv-proxy $@ 127.0.0.1 "$PORT"
@@ -46,7 +58,19 @@ let
     unset configureFlags
     PORT=$((5000 + $RANDOM % 5000))
     (>&2 echo "---> Starting remote-iserv on port $PORT")
-    WINEDLLOVERRIDES="winemac.drv=d" WINEDEBUG=warn-all,fixme-all,-menubuilder,-mscoree,-ole,-secur32,-winediag WINEPREFIX=$TMP ${wine}/bin/wine64 ${remote-iserv.override { enableProfiling = true; }}/bin/remote-iserv.exe tmp $PORT &
+    REMOTE_ISERV=$(mktemp -d)
+    ln -s ${remote-iserv.override { enableProfiling = true; }}/bin/* $REMOTE_ISERV
+    for p in $pkgsHostTargetAsString; do
+      find "$p" -iname '*.dll' -exec ln -s {} $REMOTE_ISERV \;
+      find "$p" -iname '*.dll.a' -exec ln -s {} $REMOTE_ISERV \;
+    done
+    (
+    cd $REMOTE_ISERV
+    for l in lib*.dll; do
+      if [[ ! -e "''${l#lib}" ]]; then ln -s "$l" "''${l#lib}"; fi
+    done
+    )
+    WINEDLLOVERRIDES="winemac.drv=d" WINEDEBUG=warn-all,fixme-all,-menubuilder,-mscoree,-ole,-secur32,-winediag WINEPREFIX=$TMP ${wine}/bin/wine64 $REMOTE_ISERV/remote-iserv.exe tmp $PORT &
     (>&2 echo "---| remote-iserv should have started on $PORT")
     RISERV_PID="$!"
     ${iserv-proxy}/bin/iserv-proxy $@ 127.0.0.1 "$PORT"

overlays/windows.nix

@@ -73,7 +73,7 @@ final: prev:
           # dependencies) and then placing them somewhere where wine+remote-iserv
           # will find them.
           remote-iserv.postInstall = pkgs.lib.optionalString pkgs.stdenv.hostPlatform.isWindows (
-            let extra-libs = [ pkgs.openssl.bin pkgs.libffi pkgs.gmp (pkgs.libsodium-vrf or pkgs.libsodium) pkgs.windows.mcfgthreads pkgs.buildPackages.gcc.cc pkgs.secp256k1 ]; in ''
+            let extra-libs = [ pkgs.libffi pkgs.gmp pkgs.windows.mcfgthreads pkgs.buildPackages.gcc.cc ]; in ''
             for p in ${lib.concatStringsSep " "extra-libs}; do
               find "$p" -iname '*.dll' -exec cp {} $out/bin/ \;
               find "$p" -iname '*.dll.a' -exec cp {} $out/bin/ \;

test/default.nix

@@ -202,6 +202,7 @@ let
     sublib-docs = callTest ./sublib-docs { inherit util compiler-nix-name; };
     githash = haskell-nix.callPackage ./githash { inherit compiler-nix-name; testSrc = testSrcWithGitDir; };
     c-ffi = callTest ./c-ffi { inherit util compiler-nix-name; };
+    th-dlls = callTest ./th-dlls { inherit util compiler-nix-name; };
 
     unit = unitTests;
   };

test/th-dlls/default.nix

@@ -0,0 +1,30 @@
+# Test a package set
+{ stdenv, lib, util, mkCabalProjectPkgSet, project', haskellLib, recurseIntoAttrs, testSrc, compiler-nix-name }:
+
+with lib;
+
+let
+  modules = [
+     {
+       # Package has no exposed modules which causes
+       #   haddock: No input file(s)
+       packages.cabal-simple.doHaddock = false;
+     }
+  ];
+
+  project = project' {
+    inherit compiler-nix-name;
+    src = testSrc "th-dlls";
+    inherit modules;
+  };
+
+  packages = project.hsPkgs;
+
+in recurseIntoAttrs {
+  ifdInputs = {
+    inherit (project) plan-nix;
+  };
+
+  build = packages.th-dlls.components.library;
+  build-profiled = packages.th-dlls.components.library.profiled;
+}

test/th-dlls/src/Lib.hs

@@ -0,0 +1,11 @@
+{-# LANGUAGE TemplateHaskell #-}
+module Lib where
+
+import Control.Monad.IO.Class (liftIO)
+import OpenSSL (withOpenSSL)
+import OpenSSL.BN (withBN)
+import Libsodium (sodium_init)
+import Language.Haskell.TH.Syntax (Exp(..), Lit(..))
+
+x = $(liftIO (withOpenSSL (withBN 0 (\_ -> return (LitE (IntegerL 0))))))
+y = $(liftIO (sodium_init >> return (LitE (IntegerL 0))))

test/th-dlls/th-dlls.cabal

@@ -0,0 +1,16 @@
+cabal-version:       >=1.10
+name:                th-dlls
+version:             0.1.0.0
+license:             PublicDomain
+author:              Hamish Mackenzie
+maintainer:          Hamish.K.Mackenzie@gmail.com
+build-type:          Simple
+
+library
+  build-depends:       base
+                     , HsOpenSSL
+                     , libsodium
+                     , template-haskell
+  exposed-modules:     Lib
+  hs-source-dirs:      src
+  default-language:    Haskell2010