path: root/pkgs/development/compilers/ghc/Cabal-3.16-paths-fix-cycle-aarch64-darwin.patch

This patch is based on https://github.com/sternenseemann/cabal/tree/sterni-cabal-3.16-for-aarch64-darwin and has been created using
git diff 77afa40961a686d36717604864b4c48ed5233bea eeed4f92625bbe2dbfb57f51d953e3b9a495d884 --patch --src-prefix=a/libraries/Cabal/ --dst-prefix=b/libraries/Cabal/

Reasoning and explanation of the patch can be found in the comment in the diff for PathsModule.hs below.

diff --git a/libraries/Cabal/Cabal/src/Distribution/Simple/Build/PathsModule.hs b/libraries/Cabal/Cabal/src/Distribution/Simple/Build/PathsModule.hs
index 9392acf3c..3417e613a 100644
--- a/libraries/Cabal/Cabal/src/Distribution/Simple/Build/PathsModule.hs
+++ b/libraries/Cabal/Cabal/src/Distribution/Simple/Build/PathsModule.hs
@@ -52,6 +52,7 @@ generatePathsModule pkg_descr lbi clbi =
       , Z.zIsI386 = buildArch == I386
       , Z.zIsX8664 = buildArch == X86_64
       , Z.zIsAArch64 = buildArch == AArch64
+      , Z.zOr = (||)
       , Z.zNot = not
       , Z.zManglePkgName = showPkgName
       , Z.zPrefix = show flat_prefix
@@ -61,8 +62,110 @@ generatePathsModule pkg_descr lbi clbi =
       , Z.zDatadir = zDatadir
       , Z.zLibexecdir = zLibexecdir
       , Z.zSysconfdir = zSysconfdir
+      , -- Sadly we can't be cleverer about this – we can't have literals in the template
+        Z.zShouldEmitDataDir = shouldEmit "DataDir"
+      , Z.zShouldEmitLibDir = shouldEmit "LibDir"
+      , Z.zShouldEmitDynLibDir = shouldEmit "DynLibDir"
+      , Z.zShouldEmitLibexecDir = shouldEmit "LibexecDir"
+      , Z.zShouldEmitSysconfDir = shouldEmit "SysconfDir"
+      , Z.zWarning = zWarning
+      , Z.zShouldEmitWarning = zShouldEmitWarning
       }
   where
+    -- GHC's NCG backend for aarch64-darwin does not support link-time dead code
+    -- elimination to the extent that NCG does for other targets. Consequently,
+    -- we struggle with unnecessarily retained store path references due to the
+    -- use of `Paths_*` modules – even if `getLibDir` is not used, it'll end up
+    -- in the final library or executables we build.
+    --
+    -- When using a different output for the executables and library, this
+    -- becomes more sinister: The library will contain a reference to the bin
+    -- output and itself due to `getLibDir` and `getBinDir`, but the executables
+    -- will do so, too. Either due to linking dynamically or because the library
+    -- is linked statically into the executable and retains those references.
+    -- Since Nix disallows cyclical references between two outputs, it becomes
+    -- impossible to use the `Paths_*` module and a separate `bin` output for
+    -- aarch64-darwin.
+    --
+    -- The solution we have resorted to for now, is to trim the `Paths_*` module
+    -- dynamically depending on what references *could* be used without causing
+    -- a cyclical reference. That has the effect that any code that would not
+    -- cause a cyclical reference with dead code elimination will compile and
+    -- work for aarch64-darwin. If the code would use a `get*Dir` function that
+    -- has been omitted, this would indicate that the code would have caused a
+    -- cyclical reference anyways.
+    --
+    -- The logic for this makes some pretty big assumptions about installation
+    -- prefixes that probably only hold fully in nixpkgs with
+    -- `haskellPackages.mkDerivation`. Simple uses outside nixpkgs that have
+    -- everything below the same prefix should continue to work as expected,
+    -- though.
+    --
+    -- We assume the following:
+    --
+    -- - flat_prefix is `$out`.
+    -- - flat_libdir etc. are always below `$out`.
+    --
+    -- Since in the normal case due to static linking `$bin` and `$out` will
+    -- have the same references in libraries/executables, we need to either
+    -- prevent usage of `getBinDir` or `getLibDir` to break the cycle in case
+    -- `flat_bindir` is not below `$out`. We have decided to always allow usage
+    -- of `getBinDir`, so `getLibDir` gets dropped if a separate `bin` output is
+    -- used. This has the simple reason that `$out` which contains `flat_libdir`
+    -- tends to be quite big – we would like to have a `bin` output that doesn't
+    -- require keeping that around.
+    pathEmittable :: FilePath -> Bool
+    pathEmittable p
+      -- If the executable installation target is below `$out` the reference
+      -- cycle is within a single output (since libs are installed to `$out`)
+      -- and thus unproblematic. We can use any and all `get*Dir` functions.
+      | flat_prefix `isPrefixOf` flat_bindir = True
+      -- Otherwise, we need to disallow all `get*Dir` functions that would cause
+      -- a reference to `$out` which contains the libraries that would in turn
+      -- reference `$bin`. This always include `flat_libdir` and friends, but
+      -- can also include `flat_datadir` if no separate output for data files is
+      -- used.
+      | otherwise = not (flat_prefix `isPrefixOf` p)
+
+    -- This list maps the "name" of the directory to whether we want to include
+    -- it in the `Paths_*` module or not. `shouldEmit` performs a lookup in this.
+    dirs :: [(String, Bool)]
+    dirs =
+      map
+        (\(name, path) -> (name, pathEmittable path))
+        [ ("LibDir", flat_libdir)
+        , ("DynLibDir", flat_dynlibdir)
+        , ("DataDir", flat_datadir)
+        , ("LibexecDir", flat_libexecdir)
+        , ("SysconfDir", flat_sysconfdir)
+        ]
+
+    shouldEmit :: String -> Bool
+    shouldEmit name =
+      case lookup name dirs of
+        Just b -> b
+        Nothing -> error "panic! BUG in Cabal Paths_ patch for aarch64-darwin, report this at https://github.com/nixos/nixpkgs/issues"
+
+    -- This is a comma separated list of all functions that have been omitted.
+    -- This is included in a GHC warning which will be attached to the `Paths_*`
+    -- module in case we are dropping any `get*Dir` functions that would
+    -- normally exist.
+    --
+    -- TODO: getDataFileName is not accounted for at the moment.
+    omittedFunctions :: String
+    omittedFunctions =
+      intercalate ", " $
+        map (("get" ++) . fst) $
+          filter (not . snd) dirs
+
+    zWarning :: String
+    zWarning =
+      show $
+        "The following functions have been omitted by a nixpkgs-specific patch to Cabal: "
+          ++ omittedFunctions
+    zShouldEmitWarning :: Bool
+    zShouldEmitWarning = any (not . snd) dirs
+
     supports_cpp = supports_language_pragma
     supports_rebindable_syntax = ghc_newer_than (mkVersion [7, 0, 1])
     supports_language_pragma = ghc_newer_than (mkVersion [6, 6, 1])
diff --git a/libraries/Cabal/Cabal/src/Distribution/Simple/Build/PathsModule/Z.hs b/libraries/Cabal/Cabal/src/Distribution/Simple/Build/PathsModule/Z.hs
index 8f33717bb..b89775893 100644
--- a/libraries/Cabal/Cabal/src/Distribution/Simple/Build/PathsModule/Z.hs
+++ b/libraries/Cabal/Cabal/src/Distribution/Simple/Build/PathsModule/Z.hs
@@ -20,6 +20,14 @@ data Z
          zDatadir :: FilePath,
          zLibexecdir :: FilePath,
          zSysconfdir :: FilePath,
+         zShouldEmitLibDir :: Bool,
+         zShouldEmitDynLibDir :: Bool,
+         zShouldEmitLibexecDir :: Bool,
+         zShouldEmitDataDir :: Bool,
+         zShouldEmitSysconfDir :: Bool,
+         zShouldEmitWarning :: Bool,
+         zWarning :: String,
+         zOr :: (Bool -> Bool -> Bool),
          zNot :: (Bool -> Bool),
          zManglePkgName :: (PackageName -> String)}
     deriving Generic
@@ -74,10 +82,51 @@ render z_root = execWriter $ do
   tell "\n"
   tell "module Paths_"
   tell (zManglePkgName z_root (zPackageName z_root))
-  tell " (\n"
+  tell "\n"
+  tell "  "
+  if (zShouldEmitWarning z_root)
+  then do
+    tell "{-# WARNING "
+    tell (zWarning z_root)
+    tell " #-}"
+    return ()
+  else do
+    return ()
+  tell "\n"
+  tell "  (\n"
   tell "    version,\n"
-  tell "    getBinDir, getLibDir, getDynLibDir, getDataDir, getLibexecDir,\n"
-  tell "    getDataFileName, getSysconfDir\n"
+  tell "    getBinDir,\n"
+  if (zOr z_root (zNot z_root (zAbsolute z_root)) (zShouldEmitLibDir z_root))
+  then do
+    tell "    getLibDir,\n"
+    return ()
+  else do
+    return ()
+  if (zOr z_root (zNot z_root (zAbsolute z_root)) (zShouldEmitDynLibDir z_root))
+  then do
+    tell "    getDynLibDir,\n"
+    return ()
+  else do
+    return ()
+  if (zOr z_root (zNot z_root (zAbsolute z_root)) (zShouldEmitLibexecDir z_root))
+  then do
+    tell "    getLibexecDir,\n"
+    return ()
+  else do
+    return ()
+  if (zOr z_root (zNot z_root (zAbsolute z_root)) (zShouldEmitDataDir z_root))
+  then do
+    tell "    getDataFileName,\n"
+    tell "    getDataDir,\n"
+    return ()
+  else do
+    return ()
+  if (zOr z_root (zNot z_root (zAbsolute z_root)) (zShouldEmitSysconfDir z_root))
+  then do
+    tell "    getSysconfDir\n"
+    return ()
+  else do
+    return ()
   tell "  ) where\n"
   tell "\n"
   if (zNot z_root (zAbsolute z_root))
@@ -126,57 +175,19 @@ render z_root = execWriter $ do
   tell (zVersionDigits z_root)
   tell " []\n"
   tell "\n"
-  tell "-- |If the argument is a filename, the result is the name of a corresponding\n"
-  tell "-- file on the system on which the program is running, if the file were listed\n"
-  tell "-- in the @data-files@ field of the package's Cabal package description file.\n"
-  tell "-- No check is performed that the given filename is listed in that field.\n"
-  tell "getDataFileName :: FilePath -> IO FilePath\n"
-  tell "getDataFileName name = do\n"
-  tell "  dir <- getDataDir\n"
-  tell "  return (dir `joinFileName` name)\n"
-  tell "\n"
-  tell "-- |The location of the directory specified by Cabal's @--bindir@ option (where\n"
-  tell "-- executables that the user might invoke are installed). This can be overridden\n"
-  tell "-- at runtime using the environment variable "
-  tell (zManglePkgName z_root (zPackageName z_root))
-  tell "_bindir.\n"
-  tell "getBinDir :: IO FilePath\n"
-  tell "\n"
-  tell "-- |The location of the directory specified by Cabal's @--libdir@ option (where\n"
-  tell "-- object libraries are installed). This can be overridden at runtime using the\n"
-  tell "-- environment variable "
-  tell (zManglePkgName z_root (zPackageName z_root))
-  tell "_libdir.\n"
-  tell "getLibDir :: IO FilePath\n"
-  tell "\n"
-  tell "-- |The location of the directory specified by Cabal's @--dynlibdir@ option\n"
-  tell "-- (where dynamic libraries are installed). This can be overridden at runtime\n"
-  tell "-- using the environment variable "
-  tell (zManglePkgName z_root (zPackageName z_root))
-  tell "_dynlibdir.\n"
-  tell "getDynLibDir :: IO FilePath\n"
-  tell "\n"
-  tell "-- |The location of the directory specified by Cabal's @--datadir@ option (where\n"
-  tell "-- architecture-independent data files are installed). This can be overridden at\n"
-  tell "-- runtime using the environment variable "
-  tell (zManglePkgName z_root (zPackageName z_root))
-  tell "_datadir.\n"
-  tell "getDataDir :: IO FilePath\n"
-  tell "\n"
-  tell "-- |The location of the directory specified by Cabal's @--libexedir@ option\n"
-  tell "-- (where executables that are not expected to be invoked directly by the user\n"
-  tell "-- are installed). This can be overridden at runtime using the environment\n"
-  tell "-- variable "
-  tell (zManglePkgName z_root (zPackageName z_root))
-  tell "_libexedir.\n"
-  tell "getLibexecDir :: IO FilePath\n"
-  tell "\n"
-  tell "-- |The location of the directory specified by Cabal's @--sysconfdir@ option\n"
-  tell "-- (where configuration files are installed). This can be overridden at runtime\n"
-  tell "-- using the environment variable "
-  tell (zManglePkgName z_root (zPackageName z_root))
-  tell "_sysconfdir.\n"
-  tell "getSysconfDir :: IO FilePath\n"
+  if (zOr z_root (zNot z_root (zAbsolute z_root)) (zShouldEmitDataDir z_root))
+  then do
+    tell "-- |If the argument is a filename, the result is the name of a corresponding\n"
+    tell "-- file on the system on which the program is running, if the file were listed\n"
+    tell "-- in the @data-files@ field of the package's Cabal package description file.\n"
+    tell "-- No check is performed that the given filename is listed in that field.\n"
+    tell "getDataFileName :: FilePath -> IO FilePath\n"
+    tell "getDataFileName name = do\n"
+    tell "  dir <- getDataDir\n"
+    tell "  return (dir `joinFileName` name)\n"
+    return ()
+  else do
+    return ()
   tell "\n"
   let
     z_var0_function_defs = do
@@ -204,6 +215,7 @@ render z_root = execWriter $ do
   tell "\n"
   if (zRelocatable z_root)
   then do
+    tell "\n"
     tell "\n"
     tell "getPrefixDirReloc :: FilePath -> IO FilePath\n"
     tell "getPrefixDirReloc dirRel = do\n"
@@ -213,31 +225,68 @@ render z_root = execWriter $ do
     tell (zBindir z_root)
     tell ") `joinFileName` dirRel)\n"
     tell "\n"
+    tell "-- |The location of the directory specified by Cabal's @--bindir@ option (where\n"
+    tell "-- executables that the user might invoke are installed). This can be overridden\n"
+    tell "-- at runtime using the environment variable "
+    tell (zManglePkgName z_root (zPackageName z_root))
+    tell "_bindir.\n"
+    tell "getBinDir     :: IO FilePath\n"
     tell "getBinDir     = catchIO (getEnv \""
     tell (zManglePkgName z_root (zPackageName z_root))
     tell "_bindir\")     (\\_ -> getPrefixDirReloc $ "
     tell (zBindir z_root)
     tell ")\n"
+    tell "-- |The location of the directory specified by Cabal's @--libdir@ option (where\n"
+    tell "-- object libraries are installed). This can be overridden at runtime using the\n"
+    tell "-- environment variable "
+    tell (zManglePkgName z_root (zPackageName z_root))
+    tell "_libdir.\n"
+    tell "getLibDir     :: IO FilePath\n"
     tell "getLibDir     = catchIO (getEnv \""
     tell (zManglePkgName z_root (zPackageName z_root))
     tell "_libdir\")     (\\_ -> getPrefixDirReloc $ "
     tell (zLibdir z_root)
     tell ")\n"
+    tell "-- |The location of the directory specified by Cabal's @--dynlibdir@ option\n"
+    tell "-- (where dynamic libraries are installed). This can be overridden at runtime\n"
+    tell "-- using the environment variable "
+    tell (zManglePkgName z_root (zPackageName z_root))
+    tell "_dynlibdir.\n"
+    tell "getDynLibDir  :: IO FilePath\n"
     tell "getDynLibDir  = catchIO (getEnv \""
     tell (zManglePkgName z_root (zPackageName z_root))
     tell "_dynlibdir\")  (\\_ -> getPrefixDirReloc $ "
     tell (zDynlibdir z_root)
     tell ")\n"
+    tell "-- |The location of the directory specified by Cabal's @--datadir@ option (where\n"
+    tell "-- architecture-independent data files are installed). This can be overridden at\n"
+    tell "-- runtime using the environment variable "
+    tell (zManglePkgName z_root (zPackageName z_root))
+    tell "_datadir.\n"
+    tell "getDataDir    :: IO FilePath\n"
     tell "getDataDir    = catchIO (getEnv \""
     tell (zManglePkgName z_root (zPackageName z_root))
     tell "_datadir\")    (\\_ -> getPrefixDirReloc $ "
     tell (zDatadir z_root)
     tell ")\n"
+    tell "-- |The location of the directory specified by Cabal's @--libexedir@ option\n"
+    tell "-- (where executables that are not expected to be invoked directly by the user\n"
+    tell "-- are installed). This can be overridden at runtime using the environment\n"
+    tell "-- variable "
+    tell (zManglePkgName z_root (zPackageName z_root))
+    tell "_libexedir.\n"
+    tell "getLibexecDir :: IO FilePath\n"
     tell "getLibexecDir = catchIO (getEnv \""
     tell (zManglePkgName z_root (zPackageName z_root))
     tell "_libexecdir\") (\\_ -> getPrefixDirReloc $ "
     tell (zLibexecdir z_root)
     tell ")\n"
+    tell "-- |The location of the directory specified by Cabal's @--sysconfdir@ option\n"
+    tell "-- (where configuration files are installed). This can be overridden at runtime\n"
+    tell "-- using the environment variable "
+    tell (zManglePkgName z_root (zPackageName z_root))
+    tell "_sysconfdir.\n"
+    tell "getSysconfDir :: IO FilePath\n"
     tell "getSysconfDir = catchIO (getEnv \""
     tell (zManglePkgName z_root (zPackageName z_root))
     tell "_sysconfdir\") (\\_ -> getPrefixDirReloc $ "
@@ -251,72 +300,186 @@ render z_root = execWriter $ do
     if (zAbsolute z_root)
     then do
       tell "\n"
-      tell "bindir, libdir, dynlibdir, datadir, libexecdir, sysconfdir :: FilePath\n"
+      tell "bindir     :: FilePath\n"
       tell "bindir     = "
       tell (zBindir z_root)
       tell "\n"
-      tell "libdir     = "
-      tell (zLibdir z_root)
       tell "\n"
-      tell "dynlibdir  = "
-      tell (zDynlibdir z_root)
+      tell "-- |The location of the directory specified by Cabal's @--bindir@ option (where\n"
+      tell "-- executables that the user might invoke are installed). This can be overridden\n"
+      tell "-- at runtime using the environment variable "
+      tell (zManglePkgName z_root (zPackageName z_root))
+      tell "_bindir.\n"
+      tell "getBinDir     :: IO FilePath\n"
+      tell "getBinDir     = catchIO (getEnv \""
+      tell (zManglePkgName z_root (zPackageName z_root))
+      tell "_bindir\")     (\\_ -> return bindir)\n"
       tell "\n"
-      tell "datadir    = "
-      tell (zDatadir z_root)
+      if (zShouldEmitLibDir z_root)
+      then do
+        tell "libdir     :: FilePath\n"
+        tell "libdir     = "
+        tell (zLibdir z_root)
+        tell "\n"
+        tell "\n"
+        tell "-- |The location of the directory specified by Cabal's @--libdir@ option (where\n"
+        tell "-- object libraries are installed). This can be overridden at runtime using the\n"
+        tell "-- environment variable "
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_libdir.\n"
+        tell "getLibDir     :: IO FilePath\n"
+        tell "getLibDir     = catchIO (getEnv \""
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_libdir\")     (\\_ -> return libdir)\n"
+        return ()
+      else do
+        return ()
       tell "\n"
-      tell "libexecdir = "
-      tell (zLibexecdir z_root)
+      if (zShouldEmitDynLibDir z_root)
+      then do
+        tell "dynlibdir  :: FilePath\n"
+        tell "dynlibdir  = "
+        tell (zDynlibdir z_root)
+        tell "\n"
+        tell "-- |The location of the directory specified by Cabal's @--dynlibdir@ option\n"
+        tell "-- (where dynamic libraries are installed). This can be overridden at runtime\n"
+        tell "-- using the environment variable "
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_dynlibdir.\n"
+        tell "getDynLibDir  :: IO FilePath\n"
+        tell "getDynLibDir  = catchIO (getEnv \""
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_dynlibdir\")  (\\_ -> return dynlibdir)\n"
+        return ()
+      else do
+        return ()
       tell "\n"
-      tell "sysconfdir = "
-      tell (zSysconfdir z_root)
+      if (zShouldEmitDataDir z_root)
+      then do
+        tell "datadir    :: FilePath\n"
+        tell "datadir    = "
+        tell (zDatadir z_root)
+        tell "\n"
+        tell "\n"
+        tell "-- |The location of the directory specified by Cabal's @--datadir@ option (where\n"
+        tell "-- architecture-independent data files are installed). This can be overridden at\n"
+        tell "-- runtime using the environment variable "
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_datadir.\n"
+        tell "getDataDir    :: IO FilePath\n"
+        tell "getDataDir    = catchIO (getEnv \""
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_datadir\")    (\\_ -> return datadir)\n"
+        return ()
+      else do
+        return ()
       tell "\n"
+      if (zShouldEmitLibexecDir z_root)
+      then do
+        tell "libexecdir :: FilePath\n"
+        tell "libexecdir = "
+        tell (zLibexecdir z_root)
+        tell "\n"
+        tell "\n"
+        tell "-- |The location of the directory specified by Cabal's @--libexedir@ option\n"
+        tell "-- (where executables that are not expected to be invoked directly by the user\n"
+        tell "-- are installed). This can be overridden at runtime using the environment\n"
+        tell "-- variable "
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_libexedir.\n"
+        tell "getLibexecDir :: IO FilePath\n"
+        tell "getLibexecDir = catchIO (getEnv \""
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_libexecdir\") (\\_ -> return libexecdir)\n"
+        return ()
+      else do
+        return ()
       tell "\n"
-      tell "getBinDir     = catchIO (getEnv \""
-      tell (zManglePkgName z_root (zPackageName z_root))
-      tell "_bindir\")     (\\_ -> return bindir)\n"
-      tell "getLibDir     = catchIO (getEnv \""
-      tell (zManglePkgName z_root (zPackageName z_root))
-      tell "_libdir\")     (\\_ -> return libdir)\n"
-      tell "getDynLibDir  = catchIO (getEnv \""
-      tell (zManglePkgName z_root (zPackageName z_root))
-      tell "_dynlibdir\")  (\\_ -> return dynlibdir)\n"
-      tell "getDataDir    = catchIO (getEnv \""
-      tell (zManglePkgName z_root (zPackageName z_root))
-      tell "_datadir\")    (\\_ -> return datadir)\n"
-      tell "getLibexecDir = catchIO (getEnv \""
-      tell (zManglePkgName z_root (zPackageName z_root))
-      tell "_libexecdir\") (\\_ -> return libexecdir)\n"
-      tell "getSysconfDir = catchIO (getEnv \""
-      tell (zManglePkgName z_root (zPackageName z_root))
-      tell "_sysconfdir\") (\\_ -> return sysconfdir)\n"
+      if (zShouldEmitSysconfDir z_root)
+      then do
+        tell "sysconfdir :: FilePath\n"
+        tell "sysconfdir = "
+        tell (zSysconfdir z_root)
+        tell "\n"
+        tell "\n"
+        tell "-- |The location of the directory specified by Cabal's @--sysconfdir@ option\n"
+        tell "-- (where configuration files are installed). This can be overridden at runtime\n"
+        tell "-- using the environment variable "
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_sysconfdir.\n"
+        tell "getSysconfDir :: IO FilePath\n"
+        tell "getSysconfDir = catchIO (getEnv \""
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_sysconfdir\") (\\_ -> return sysconfdir)\n"
+        return ()
+      else do
+        return ()
       tell "\n"
       return ()
     else do
       if (zIsWindows z_root)
       then do
+        tell "\n"
         tell "\n"
         tell "prefix :: FilePath\n"
         tell "prefix = "
         tell (zPrefix z_root)
         tell "\n"
         tell "\n"
+        tell "-- |The location of the directory specified by Cabal's @--bindir@ option (where\n"
+        tell "-- executables that the user might invoke are installed). This can be overridden\n"
+        tell "-- at runtime using the environment variable "
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_bindir.\n"
+        tell "getBinDir     :: IO FilePath\n"
         tell "getBinDir     = getPrefixDirRel $ "
         tell (zBindir z_root)
         tell "\n"
+        tell "-- |The location of the directory specified by Cabal's @--libdir@ option (where\n"
+        tell "-- object libraries are installed). This can be overridden at runtime using the\n"
+        tell "-- environment variable "
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_libdir.\n"
+        tell "getLibDir     :: IO FilePath\n"
         tell "getLibDir     = "
         tell (zLibdir z_root)
         tell "\n"
+        tell "-- |The location of the directory specified by Cabal's @--dynlibdir@ option\n"
+        tell "-- (where dynamic libraries are installed). This can be overridden at runtime\n"
+        tell "-- using the environment variable "
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_dynlibdir.\n"
+        tell "getDynLibDir  :: IO FilePath\n"
         tell "getDynLibDir  = "
         tell (zDynlibdir z_root)
         tell "\n"
+        tell "-- |The location of the directory specified by Cabal's @--datadir@ option (where\n"
+        tell "-- architecture-independent data files are installed). This can be overridden at\n"
+        tell "-- runtime using the environment variable "
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_datadir.\n"
+        tell "getDataDir    :: IO FilePath\n"
         tell "getDataDir    = catchIO (getEnv \""
         tell (zManglePkgName z_root (zPackageName z_root))
         tell "_datadir\")    (\\_ -> "
         tell (zDatadir z_root)
         tell ")\n"
+        tell "-- |The location of the directory specified by Cabal's @--libexedir@ option\n"
+        tell "-- (where executables that are not expected to be invoked directly by the user\n"
+        tell "-- are installed). This can be overridden at runtime using the environment\n"
+        tell "-- variable "
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_libexedir.\n"
+        tell "getLibexecDir :: IO FilePath\n"
         tell "getLibexecDir = "
         tell (zLibexecdir z_root)
         tell "\n"
+        tell "-- |The location of the directory specified by Cabal's @--sysconfdir@ option\n"
+        tell "-- (where configuration files are installed). This can be overridden at runtime\n"
+        tell "-- using the environment variable "
+        tell (zManglePkgName z_root (zPackageName z_root))
+        tell "_sysconfdir.\n"
+        tell "getSysconfDir :: IO FilePath\n"
         tell "getSysconfDir = "
         tell (zSysconfdir z_root)
         tell "\n"
diff --git a/libraries/Cabal/cabal-dev-scripts/src/GenPathsModule.hs b/libraries/Cabal/cabal-dev-scripts/src/GenPathsModule.hs
index 7c5c947a5..3b7a67498 100644
--- a/libraries/Cabal/cabal-dev-scripts/src/GenPathsModule.hs
+++ b/libraries/Cabal/cabal-dev-scripts/src/GenPathsModule.hs
@@ -42,6 +42,16 @@ $(capture "decls" [d|
         , zLibexecdir :: FilePath
         , zSysconfdir :: FilePath
 
+        , zShouldEmitLibDir     :: Bool
+        , zShouldEmitDynLibDir  :: Bool
+        , zShouldEmitLibexecDir :: Bool
+        , zShouldEmitDataDir    :: Bool
+        , zShouldEmitSysconfDir :: Bool
+
+        , zShouldEmitWarning :: Bool
+        , zWarning           :: String
+
+        , zOr                         :: Bool -> Bool -> Bool
         , zNot                        :: Bool -> Bool
         , zManglePkgName              :: PackageName -> String
         }
diff --git a/libraries/Cabal/templates/Paths_pkg.template.hs b/libraries/Cabal/templates/Paths_pkg.template.hs
index a9b02b0ef..d99252a29 100644
--- a/libraries/Cabal/templates/Paths_pkg.template.hs
+++ b/libraries/Cabal/templates/Paths_pkg.template.hs
@@ -31,10 +31,31 @@ For further information about Cabal's options for its configuration step, and
 their default values, see the Cabal User Guide.
 -}
 
-module Paths_{{ manglePkgName packageName }} (
+module Paths_{{ manglePkgName packageName }}
+  {% if shouldEmitWarning %}{-# WARNING {{ warning }} #-}{% endif %}
+  (
     version,
-    getBinDir, getLibDir, getDynLibDir, getDataDir, getLibexecDir,
-    getDataFileName, getSysconfDir
+    getBinDir,
+{# We only care about the absolute case for our emit logic, since only in this
+   case references are incurred. We are not going to hit isWindows and relocatable
+   has no absolute references to begin with.
+#}
+{% if or (not absolute) shouldEmitLibDir %}
+    getLibDir,
+{% endif %}
+{% if or (not absolute) shouldEmitDynLibDir %}
+    getDynLibDir,
+{% endif %}
+{% if or (not absolute) shouldEmitLibexecDir %}
+    getLibexecDir,
+{% endif %}
+{% if or (not absolute) shouldEmitDataDir %}
+    getDataFileName,
+    getDataDir,
+{% endif %}
+{% if or (not absolute) shouldEmitSysconfDir %}
+    getSysconfDir
+{% endif %}
   ) where
 
 {% if not absolute %}
@@ -73,6 +94,7 @@ catchIO = Exception.catch
 version :: Version
 version = Version {{ versionDigits }} []
 
+{% if or (not absolute) shouldEmitDataDir %}
 -- |If the argument is a filename, the result is the name of a corresponding
 -- file on the system on which the program is running, if the file were listed
 -- in the @data-files@ field of the package's Cabal package description file.
@@ -81,37 +103,7 @@ getDataFileName :: FilePath -> IO FilePath
 getDataFileName name = do
   dir <- getDataDir
   return (dir `joinFileName` name)
-
--- |The location of the directory specified by Cabal's @--bindir@ option (where
--- executables that the user might invoke are installed). This can be overridden
--- at runtime using the environment variable {{ manglePkgName packageName }}_bindir.
-getBinDir :: IO FilePath
-
--- |The location of the directory specified by Cabal's @--libdir@ option (where
--- object libraries are installed). This can be overridden at runtime using the
--- environment variable {{ manglePkgName packageName }}_libdir.
-getLibDir :: IO FilePath
-
--- |The location of the directory specified by Cabal's @--dynlibdir@ option
--- (where dynamic libraries are installed). This can be overridden at runtime
--- using the environment variable {{ manglePkgName packageName }}_dynlibdir.
-getDynLibDir :: IO FilePath
-
--- |The location of the directory specified by Cabal's @--datadir@ option (where
--- architecture-independent data files are installed). This can be overridden at
--- runtime using the environment variable {{ manglePkgName packageName }}_datadir.
-getDataDir :: IO FilePath
-
--- |The location of the directory specified by Cabal's @--libexedir@ option
--- (where executables that are not expected to be invoked directly by the user
--- are installed). This can be overridden at runtime using the environment
--- variable {{ manglePkgName packageName }}_libexedir.
-getLibexecDir :: IO FilePath
-
--- |The location of the directory specified by Cabal's @--sysconfdir@ option
--- (where configuration files are installed). This can be overridden at runtime
--- using the environment variable {{ manglePkgName packageName }}_sysconfdir.
-getSysconfDir :: IO FilePath
+{% endif %}
 
 {% defblock function_defs %}
 minusFileName :: FilePath -> String -> FilePath
@@ -140,48 +132,155 @@ splitFileName p = (reverse (path2++drive), reverse fname)
 
 {% if relocatable %}
 
+{# Relocatable can not incur any absolute references, so we can ignore it.
+   Additionally, --enable-relocatable is virtually useless in Nix builds
+#}
+
 getPrefixDirReloc :: FilePath -> IO FilePath
 getPrefixDirReloc dirRel = do
   exePath <- getExecutablePath
   let (dir,_) = splitFileName exePath
   return ((dir `minusFileName` {{ bindir }}) `joinFileName` dirRel)
 
+-- |The location of the directory specified by Cabal's @--bindir@ option (where
+-- executables that the user might invoke are installed). This can be overridden
+-- at runtime using the environment variable {{ manglePkgName packageName }}_bindir.
+getBinDir     :: IO FilePath
 getBinDir     = catchIO (getEnv "{{ manglePkgName packageName }}_bindir")     (\_ -> getPrefixDirReloc $ {{ bindir }})
+-- |The location of the directory specified by Cabal's @--libdir@ option (where
+-- object libraries are installed). This can be overridden at runtime using the
+-- environment variable {{ manglePkgName packageName }}_libdir.
+getLibDir     :: IO FilePath
 getLibDir     = catchIO (getEnv "{{ manglePkgName packageName }}_libdir")     (\_ -> getPrefixDirReloc $ {{ libdir }})
+-- |The location of the directory specified by Cabal's @--dynlibdir@ option
+-- (where dynamic libraries are installed). This can be overridden at runtime
+-- using the environment variable {{ manglePkgName packageName }}_dynlibdir.
+getDynLibDir  :: IO FilePath
 getDynLibDir  = catchIO (getEnv "{{ manglePkgName packageName }}_dynlibdir")  (\_ -> getPrefixDirReloc $ {{ dynlibdir }})
+-- |The location of the directory specified by Cabal's @--datadir@ option (where
+-- architecture-independent data files are installed). This can be overridden at
+-- runtime using the environment variable {{ manglePkgName packageName }}_datadir.
+getDataDir    :: IO FilePath
 getDataDir    = catchIO (getEnv "{{ manglePkgName packageName }}_datadir")    (\_ -> getPrefixDirReloc $ {{ datadir }})
+-- |The location of the directory specified by Cabal's @--libexedir@ option
+-- (where executables that are not expected to be invoked directly by the user
+-- are installed). This can be overridden at runtime using the environment
+-- variable {{ manglePkgName packageName }}_libexedir.
+getLibexecDir :: IO FilePath
 getLibexecDir = catchIO (getEnv "{{ manglePkgName packageName }}_libexecdir") (\_ -> getPrefixDirReloc $ {{ libexecdir }})
+-- |The location of the directory specified by Cabal's @--sysconfdir@ option
+-- (where configuration files are installed). This can be overridden at runtime
+-- using the environment variable {{ manglePkgName packageName }}_sysconfdir.
+getSysconfDir :: IO FilePath
 getSysconfDir = catchIO (getEnv "{{ manglePkgName packageName }}_sysconfdir") (\_ -> getPrefixDirReloc $ {{ sysconfdir }})
 
 {% useblock function_defs %}
 
 {% elif absolute %}
 
-bindir, libdir, dynlibdir, datadir, libexecdir, sysconfdir :: FilePath
+bindir     :: FilePath
 bindir     = {{ bindir }}
-libdir     = {{ libdir }}
-dynlibdir  = {{ dynlibdir }}
-datadir    = {{ datadir }}
-libexecdir = {{ libexecdir }}
-sysconfdir = {{ sysconfdir }}
 
+-- |The location of the directory specified by Cabal's @--bindir@ option (where
+-- executables that the user might invoke are installed). This can be overridden
+-- at runtime using the environment variable {{ manglePkgName packageName }}_bindir.
+getBinDir     :: IO FilePath
 getBinDir     = catchIO (getEnv "{{ manglePkgName packageName }}_bindir")     (\_ -> return bindir)
+
+{% if shouldEmitLibDir %}
+libdir     :: FilePath
+libdir     = {{ libdir }}
+
+-- |The location of the directory specified by Cabal's @--libdir@ option (where
+-- object libraries are installed). This can be overridden at runtime using the
+-- environment variable {{ manglePkgName packageName }}_libdir.
+getLibDir     :: IO FilePath
 getLibDir     = catchIO (getEnv "{{ manglePkgName packageName }}_libdir")     (\_ -> return libdir)
+{% endif %}
+
+{% if shouldEmitDynLibDir %}
+dynlibdir  :: FilePath
+dynlibdir  = {{ dynlibdir }}
+-- |The location of the directory specified by Cabal's @--dynlibdir@ option
+-- (where dynamic libraries are installed). This can be overridden at runtime
+-- using the environment variable {{ manglePkgName packageName }}_dynlibdir.
+getDynLibDir  :: IO FilePath
 getDynLibDir  = catchIO (getEnv "{{ manglePkgName packageName }}_dynlibdir")  (\_ -> return dynlibdir)
+{% endif %}
+
+{% if shouldEmitDataDir %}
+datadir    :: FilePath
+datadir    = {{ datadir }}
+
+-- |The location of the directory specified by Cabal's @--datadir@ option (where
+-- architecture-independent data files are installed). This can be overridden at
+-- runtime using the environment variable {{ manglePkgName packageName }}_datadir.
+getDataDir    :: IO FilePath
 getDataDir    = catchIO (getEnv "{{ manglePkgName packageName }}_datadir")    (\_ -> return datadir)
+{% endif %}
+
+{% if shouldEmitLibexecDir %}
+libexecdir :: FilePath
+libexecdir = {{ libexecdir }}
+
+-- |The location of the directory specified by Cabal's @--libexedir@ option
+-- (where executables that are not expected to be invoked directly by the user
+-- are installed). This can be overridden at runtime using the environment
+-- variable {{ manglePkgName packageName }}_libexedir.
+getLibexecDir :: IO FilePath
 getLibexecDir = catchIO (getEnv "{{ manglePkgName packageName }}_libexecdir") (\_ -> return libexecdir)
+{% endif %}
+
+{% if shouldEmitSysconfDir %}
+sysconfdir :: FilePath
+sysconfdir = {{ sysconfdir }}
+
+-- |The location of the directory specified by Cabal's @--sysconfdir@ option
+-- (where configuration files are installed). This can be overridden at runtime
+-- using the environment variable {{ manglePkgName packageName }}_sysconfdir.
+getSysconfDir :: IO FilePath
 getSysconfDir = catchIO (getEnv "{{ manglePkgName packageName }}_sysconfdir") (\_ -> return sysconfdir)
+{% endif %}
 
 {% elif isWindows %}
 
+{# We are only trying to fix the problem for aarch64-darwin with this patch,
+   so let's ignore Windows which we can reach via pkgsCross, for example.
+#}
+
 prefix :: FilePath
 prefix = {{ prefix }}
 
+-- |The location of the directory specified by Cabal's @--bindir@ option (where
+-- executables that the user might invoke are installed). This can be overridden
+-- at runtime using the environment variable {{ manglePkgName packageName }}_bindir.
+getBinDir     :: IO FilePath
 getBinDir     = getPrefixDirRel $ {{ bindir }}
+-- |The location of the directory specified by Cabal's @--libdir@ option (where
+-- object libraries are installed). This can be overridden at runtime using the
+-- environment variable {{ manglePkgName packageName }}_libdir.
+getLibDir     :: IO FilePath
 getLibDir     = {{ libdir }}
+-- |The location of the directory specified by Cabal's @--dynlibdir@ option
+-- (where dynamic libraries are installed). This can be overridden at runtime
+-- using the environment variable {{ manglePkgName packageName }}_dynlibdir.
+getDynLibDir  :: IO FilePath
 getDynLibDir  = {{ dynlibdir }}
+-- |The location of the directory specified by Cabal's @--datadir@ option (where
+-- architecture-independent data files are installed). This can be overridden at
+-- runtime using the environment variable {{ manglePkgName packageName }}_datadir.
+getDataDir    :: IO FilePath
 getDataDir    = catchIO (getEnv "{{ manglePkgName packageName }}_datadir")    (\_ -> {{ datadir }})
+-- |The location of the directory specified by Cabal's @--libexedir@ option
+-- (where executables that are not expected to be invoked directly by the user
+-- are installed). This can be overridden at runtime using the environment
+-- variable {{ manglePkgName packageName }}_libexedir.
+getLibexecDir :: IO FilePath
 getLibexecDir = {{ libexecdir }}
+-- |The location of the directory specified by Cabal's @--sysconfdir@ option
+-- (where configuration files are installed). This can be overridden at runtime
+-- using the environment variable {{ manglePkgName packageName }}_sysconfdir.
+getSysconfDir :: IO FilePath
 getSysconfDir = {{ sysconfdir }}
 
 getPrefixDirRel :: FilePath -> IO FilePath