cc-wrapper: WIP linking hack for mac OS

Probably best to override Haskell packages set, or anything else
linking a lot of libraries, with this.

pkgs/build-support/cc-wrapper/default.nix

@@ -12,6 +12,7 @@
 , isGNU ? false, isClang ? cc.isClang or false, gnugrep ? null
 , buildPackages ? {}, hostPlatform, targetPlatform
 , runCommand ? null
+, useMacosReexportHack ? false
 }:
 
 with stdenv.lib;
@@ -295,7 +296,20 @@ stdenv.mkDerivation {
         ln -s $ldPath/${prefix}as $out/bin/${prefix}as
       fi
 
-      wrap ${prefix}ld ${preWrap ./ld-wrapper.sh} ''${ld:-$ldPath/${prefix}ld}
+      wrap ${prefix}ld ${if !useMacosReexportHack
+      then preWrap ./ld-wrapper.sh
+      else stdenv.mkDerivation {
+        name = "patched-ld-wrapper-src";
+        patches = [ ./macos-sierra-reexport-hack.patch ];
+        unpackPhase = ''
+          src=$PWD
+          cp ${./ld-wrapper.sh} ld-wrapper.sh
+        '';
+        buildPhase = "";
+        installPhase = ''
+          cp ld-wrapper.sh $out
+        '';
+      }} ''${ld:-$ldPath/${prefix}ld}
 
       if [ -e ${binutils_bin}/bin/${prefix}ld.gold ]; then
         wrap ${prefix}ld.gold ${preWrap ./ld-wrapper.sh} ${binutils_bin}/bin/${prefix}ld.gold
@@ -399,5 +413,7 @@ stdenv.mkDerivation {
     { description =
         stdenv.lib.attrByPath ["meta" "description"] "System C compiler" cc_
         + " (wrapper script)";
-    };
+  } // optionalAttrs useMacosReexportHack {
+    platforms = stdenv.lib.platforms.darwin;
+  };
 }

pkgs/build-support/cc-wrapper/macos-sierra-reexport-hack.patch

@@ -0,0 +1,140 @@
+--- a/ld-wrapper.sh
++++ b/ld-wrapper.sh
+@@ -101,35 +101,115 @@ if [ "$NIX_DONT_SET_RPATH" != 1 ]; then
+     rpath=""
+ 
+     # First, find all -L... switches.
+-    allParams=("${params[@]}" ${extra[@]})
++    declare -ar allParams=("${extraBefore[@]}" "${params[@]}" "${extra[@]}")
++    declare -a allParamsPost=() childrenLookup=() childrenLink=()
++
++    declare -r recurThreshold=300
++
++    declare overflowCount=0
++    for p in "${allParams[@]}"; do
++        case "$p" in
++            -o)
++                declare -r outputName="$p2"
++                ;;
++            (-l*)
++                let overflowCount+=1
++                ;;
++            *) ;;
++        esac
++    done
++
++    if (( "$overflowCount" > "$recurThreshold" )); then
++       declare -r linkIndirect="1"
++    else
++       declare -r linkIndirect=""
++    fi
++
++    function append_Ls() {
++        if [[ -n "$linkIndirect" ]]; then
++            childrenLookup+=("$@")
++        fi
++        allParamsPost+=("$@")
++    }
++
++    function append_ls() {
++        local p
++        if (( $# == 2 )); then p="$2"; else p="${1:2}"; fi
++        if [[ -n "$linkIndirect" && "$p" != "-lto_library" && "$p" != "-lSystem" ]]; then
++            childrenLink+=("$@")
++        else
++            allParamsPost+=("$@")
++        fi
++    }
++
+     n=0
+     while [ $n -lt ${#allParams[*]} ]; do
+         p=${allParams[n]}
+         p2=${allParams[$((n+1))]}
++
+         if [ "${p:0:3}" = -L/ ]; then
+             addToLibPath ${p:2}
++            append_Ls "$p"
+         elif [ "$p" = -L ]; then
+             addToLibPath ${p2}
++            append_Ls "$p" "$p2"
+             n=$((n + 1))
+         elif [ "$p" = -l ]; then
+             addToLibs ${p2}
++            append_ls "$p" "$p2"
+             n=$((n + 1))
+         elif [ "${p:0:2}" = -l ]; then
+             addToLibs ${p:2}
++            append_ls "$p"
+         elif [ "$p" = -dynamic-linker ]; then
+             # Ignore the dynamic linker argument, or it
+             # will get into the next 'elif'. We don't want
+             # the dynamic linker path rpath to go always first.
++            allParamsPost+=("$p" "$p2")
+             n=$((n + 1))
+         elif [[ "$p" =~ ^[^-].*\.so($|\.) ]]; then
+             # This is a direct reference to a shared library, so add
+             # its directory to the rpath.
+             path="$(dirname "$p")";
+             addToRPath "${path}"
++            allParamsPost+=("$p")
++        else
++            allParamsPost+=("$p")
+         fi
++
+         n=$((n + 1))
+     done
+ 
++    if [[ "$linkIndirect" ]]; then
++        while (( $n < "${#childrenLink[@]}" )); do
++            childrenLink[n]="-reexport${childrenLink[n]}"
++        done
++        declare -r outputNameLibless=$(basename $(
++            if [[ "${outputName:0:3}" = lib ]]; then
++                echo "${outputName:3}"
++            else
++                echo "${outputName:-unnamed}"
++            fi))
++        declare -ra children=("$outputNameLibless-reexport-delegate-0" \
++                              "$outputNameLibless-reexport-delegate-1")
++
++        mkdir -p "$out/lib"
++
++        # first half of libs
++        "$0" -dylib -o "$out/lib/lib${children[0]}.dylib" \
++             -install_name "$out/lib/lib${children[0]}.dylib" \
++             "${childrenLookup[@]}" \
++             "${childrenLink[@]::$((${#childrenLink[@]} / 2 ))}"
++
++        # second half of libs
++        "$0" -dylib -o "$out/lib/lib${children[1]}.dylib" \
++             -install_name "$out/lib/lib${children[1]}.dylib" \
++             "${childrenLookup[@]}" \
++             "${childrenLink[@]:$((${#childrenLink[@]} / 2 ))}"
++
++        allParamsPost+=("-L$out/lib" "-l${children[0]}" "-l${children[1]}")
++    fi
++
+     # Second, for each directory in the library search path (-L...),
+     # see if it contains a dynamic library used by a -l... flag.  If
+     # so, add the directory to the rpath.
+@@ -170,12 +243,8 @@ fi
+ 
+ # Optionally print debug info.
+ if [ -n "$NIX_DEBUG" ]; then
+-  echo "original flags to @prog@:" >&2
+-  for i in "${params[@]}"; do
+-      echo "  $i" >&2
+-  done
+-  echo "extra flags to @prog@:" >&2
+-  for i in ${extra[@]}; do
++  echo "flags to @prog@:" >&2
++  for i in "${allParamsPost[@]}"; do
+       echo "  $i" >&2
+   done
+ fi
+@@ -185,4 +254,4 @@ if [ -n "$NIX_LD_WRAPPER_EXEC_HOOK" ]; then
+ fi
+ 
+ PATH="$path_backup"
+-exec @prog@ ${extraBefore[@]} "${params[@]}" ${extra[@]}
++exec @prog@ "${allParamsPost[@]}"