Musl changes

builder/comp-builder.nix

@@ -1,13 +1,6 @@
 { stdenv, buildPackages, ghc, lib, gobject-introspection ? null, haskellLib, makeConfigFiles, ghcForComponent, hsPkgs, runCommand, libffi, gmp, zlib, ncurses, numactl, nodejs }:
-let
-   # These are here to avoid multiple calls to override
-   gmpStatic = gmp.override { withStatic = true; };
-   zlibStatic = zlib.static;
-   ncursesStatic = ncurses.override { enableStatic = true; };
-   numactlStatic = numactl.overrideAttrs (_: { configureFlags = "--enable-static"; });
-in
 lib.makeOverridable (
-let self = 
+let self =
 { componentId
 , component
 , package
@@ -40,7 +33,10 @@ let self =
 , dontStrip ? component.dontStrip
 
 , enableStatic ? component.enableStatic
-, enableShared ? component.enableShared && !haskellLib.isCrossHost
+, enableShared ? ghc.enableShared && component.enableShared && !haskellLib.isCrossHost
+               # on x86 we'll use shared libraries, even with musl m(
+               # ghc's internal linker seems to be broken on x86.
+               && !(stdenv.hostPlatform.isMusl && !stdenv.hostPlatform.isx86)
 , enableDeadCodeElimination ? component.enableDeadCodeElimination
 
 # Options for Haddock generation
@@ -126,10 +122,6 @@ let
       "--disable-executable-dynamic"
       "--ghc-option=-optl=-pthread"
       "--ghc-option=-optl=-static"
-      "--ghc-option=-optl=-L${gmpStatic}/lib"
-      "--ghc-option=-optl=-L${zlibStatic}/lib"
-      "--ghc-option=-optl=-L${ncursesStatic}/lib"
-      "--ghc-option=-optl=-L${numactlStatic}/lib"
     ] ++ lib.optional enableSeparateDataOutput "--datadir=$data/share/${ghc.name}"
       ++ lib.optional doHaddock' "--docdir=${docdir "$doc"}"
       ++ lib.optional (enableLibraryProfiling || enableExecutableProfiling) "--profiling-detail=${profilingDetail}"

compiler/ghc/default.nix

@@ -107,6 +107,11 @@ let
   '' + stdenv.lib.optionalString (!enableTerminfo) ''
     WITH_TERMINFO=NO
   ''
+  # musl doesn't have a system-linker. Only on x86, and on x86 we need it, as
+  # our elf linker for x86_64 is broken.
+  + stdenv.lib.optionalString (targetPlatform.isMusl && !targetPlatform.isx86) ''
+    compiler_CONFIGURE_OPTS += --flags=-dynamic-system-linker
+  ''
   # While split sections are now enabled by default in ghc 8.8 for windows,
   # the seem to lead to `too many sections` errors when building base for
   # profiling.
@@ -284,15 +289,15 @@ stdenv.mkDerivation (rec {
     if [[ ! -f "$out/bin/${targetPrefix}ghc-pkg" ]]; then
       echo "ERROR: Missing file $out/bin/${targetPrefix}ghc-pkg"
       exit 0
-    fi    
+    fi
     if [[ ! -d "$out/lib/${targetPrefix}ghc-${version}" ]]; then
       echo "ERROR: Missing directory $out/lib/${targetPrefix}ghc-${version}"
       exit 0
-    fi    
+    fi
     if (( $(ls -1 "$out/lib/${targetPrefix}ghc-${version}" | wc -l) < 30 )); then
       echo "ERROR: Expected more files in $out/lib/${targetPrefix}ghc-${version}"
       exit 0
-    fi    
+    fi
   '';
 
   passthru = {

overlays/bootstrap.nix

@@ -141,6 +141,7 @@ in {
                 # hadrian one.
                 ++ fromUntil "8.8" "8.12"      ./patches/ghc/bec76733b818b0489ffea0834ab6b1560207577c.patch
                 ++ fromUntil "8.8" "8.12"      ./patches/ghc/67738db10010fd28a8e997b5c8f83ea591b88a0e.patch
+                ++ final.lib.optional (versionAtLeast "8.6.4" && versionLessThan "8.8") ./patches/ghc/ghc-no-system-linker.patch
                 ;
         in ({
             ghc844 = final.callPackage ../compiler/ghc {

overlays/hackage-quirks.nix

@@ -44,12 +44,6 @@ in { haskell-nix = prev.haskell-nix // {
             sha256 = "0jcpja4s4cylmg9rddyakb1p1fb4l41ffwmy0njpb1dxc5z3v618";
           };
         })
-        # Musl needs static zlib
-        (lib.optionalAttrs final.stdenv.hostPlatform.isMusl {
-          packages.pandoc.components.exes.pandoc.configureFlags = [
-            "--ghc-option=-optl=-L${final.zlib.static}/lib"
-          ];
-        })
       ];
     };
 

overlays/musl.nix

@@ -11,6 +11,19 @@ final: prev: prev.lib.optionalAttrs prev.stdenv.hostPlatform.isMusl ({
   # Prevent pkgsMusl.pkgsStatic chain
   busybox-sandbox-shell = prev.busybox-sandbox-shell.override { inherit (final) busybox; };
 
+  # we don't want the static output to be split. That just
+  # messes with the z -> libz mapping. We can't have a conditonal
+  # z -> libz / z -> libz.static mapping without threading the
+  # package configuration in.  That seems a bit overkill.
+  zlib = prev.zlib.override { splitStaticOutput = false; };
+
+  # and a few more packages that need their static libs explicitly enabled
+  gmp = prev.gmp.override { withStatic = true; };
+  ncurses = prev.ncurses.override { enableStatic = true; };
+  libsodium = prev.libsodium.overrideAttrs (_: { dontDisableStatic = true; });
+
+  numactl = prev.numactl.overrideAttrs (_: { configureFlags = "--enable-static"; });
+
   # Fails on cross compile
   nix = prev.nix.overrideAttrs (_: { doInstallCheck = false; });
 } // prev.lib.optionalAttrs (prev.lib.versionAtLeast prev.lib.trivial.release "20.03") {

overlays/patches/ghc/ghc-no-system-linker.patch

@@ -0,0 +1,78 @@
+diff --git a/compiler/ghc.cabal.in b/compiler/ghc.cabal.in
+index 01628dcad1..209704d034 100644
+--- a/compiler/ghc.cabal.in
++++ b/compiler/ghc.cabal.in
+@@ -45,6 +45,11 @@ Flag terminfo
+     Default: True
+     Manual: True
+
++Flag dynamic-system-linker
++    Description: The system can load dynamic code. This is not the case for musl.
++    Default: True
++    Manual: False
++
+ Library
+     Default-Language: Haskell2010
+     Exposed: False
+@@ -84,6 +89,9 @@ Library
+         CPP-Options: -DGHCI
+         Include-Dirs: ../rts/dist/build @FFIIncludeDir@
+
++    if flag(dynamic-system-linker)
++        CPP-Options: -DCAN_LOAD_DLL
++
+     Other-Extensions:
+         BangPatterns
+         CPP
+diff --git a/compiler/ghci/Linker.hs b/compiler/ghci/Linker.hs
+index 3b030be2d3..879c5c19ee 100644
+--- a/compiler/ghci/Linker.hs
++++ b/compiler/ghci/Linker.hs
+@@ -1295,13 +1295,13 @@ linkPackage hsc_env pkg
+
+         maybePutStr dflags
+             ("Loading package " ++ sourcePackageIdString pkg ++ " ... ")
+-
+         -- See comments with partOfGHCi
++#if defined(CAN_LOAD_DLL)
+         when (packageName pkg `notElem` partOfGHCi) $ do
+             loadFrameworks hsc_env platform pkg
+             mapM_ (load_dyn hsc_env)
+               (known_dlls ++ map (mkSOName platform) dlls)
+-
++#endif
+         -- After loading all the DLLs, we can load the static objects.
+         -- Ordering isn't important here, because we do one final link
+         -- step to resolve everything.
+@@ -1382,10 +1382,15 @@ locateLib hsc_env is_hs lib_dirs gcc_dirs lib
+     --   O(n). Loading an import library is also O(n) so in general we prefer
+     --   shared libraries because they are simpler and faster.
+     --
+-  = findDll   user `orElse`
++  =
++#if defined(CAN_LOAD_DLL)
++    findDll   user `orElse`
++#endif
+     tryImpLib user `orElse`
++#if defined(CAN_LOAD_DLL)
+     findDll   gcc  `orElse`
+     findSysDll     `orElse`
++#endif
+     tryImpLib gcc  `orElse`
+     findArchive    `orElse`
+     tryGcc         `orElse`
+@@ -1452,7 +1457,13 @@ locateLib hsc_env is_hs lib_dirs gcc_dirs lib
+                          full     = dllpath $ search lib_so_name lib_dirs
+                          gcc name = liftM (fmap Archive) $ search name lib_dirs
+                          files    = import_libs ++ arch_files
+-                     in apply $ short : full : map gcc files
++                         dlls     = [short, full]
++                         archives = map gcc files
++                     in apply $
++#if defined(CAN_LOAD_DLL)
++                          dlls ++
++#endif
++                          archives
+      tryImpLib re = case os of
+                        OSMinGW32 ->
+                         let dirs' = if re == user then lib_dirs else gcc_dirs

test/fully-static/default.nix

@@ -17,32 +17,11 @@ let
     src = testSrc "fully-static";
     pkg-def-extras = [];
     modules = [
-      # Musl libc fully static build
-      (let
-        staticLibs = [
-          zlib.static
-          (openssl.override { static = true; }).out
-          (libffi.overrideAttrs (oldAttrs: {
-            dontDisableStatic = true;
-            configureFlags = (oldAttrs.configureFlags or []) ++ [
-              "--enable-static"
-              "--disable-shared"
-            ];
-          }))
-        ] ++ optional gpl (gmp6.override { withStatic = true; });
-
-        withFullyStatic = {
-          configureFlags =
-             optionals stdenv.hostPlatform.isMusl (map (drv: "--ghc-option=-optl=-L${drv}/lib") staticLibs);
-        };
-      in {
+      {
         # Select a non-GMP compiler, usually for software licensing reasons.
         ghc.package = mkIf (stdenv.hostPlatform.isMusl && !gpl)
             buildPackages.haskell-nix.compiler.integer-simple.${compiler};
-
-        # Add GHC flags and libraries for fully static build
-        packages.pandoc.components.exes.pandoc = withFullyStatic;
-      })
+      }
     ];
   };
   packagesGmp = (project { gpl = true; }).hsPkgs;