path: root/pkgs/development/compilers/ghc/Cabal-3.6-3.8-paths-fix-cycle-aarch64-darwin.patch

This patch is based on https://github.com/sternenseemann/cabal/compare/982646d67b95b32813b89ab5d2d2f4d4dc03fb2b..7c49047f253e1f128e2df356400ec5da6f11066b
and has been postprocessed with `filterdiff --strip=1 --addoldprefix=a/libraries/Cabal/ --addnewprefix=b/libraries/Cabal/`.
Note that the base for the diff is not the Cabal 3.6.3.0 release tag, but
982646d67b95b32813b89ab5d2d2f4d4dc03fb2b which is obtained by applying
https://github.com/haskell/cabal/commit/6c796218c92f93c95e94d5ec2d077f6956f68e98
on top of said release tag. That patch is applied to all our GHCs in the 9.2 series.

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

diffCabal/src/Distribution/Simple/Build/PathsModule.hs b/Cabal/src/Distribution/Simple/Build/PathsModule.hs
index b2be7e1a8..9b63e9850 100644
--- a/libraries/Cabal/Cabal/src/Distribution/Simple/Build/PathsModule.hs
+++ b/libraries/Cabal/Cabal/src/Distribution/Simple/Build/PathsModule.hs
@@ -46,6 +46,7 @@ generatePathsModule pkg_descr lbi clbi = Z.render Z.Z
     , Z.zIsWindows                  = isWindows
     , Z.zIsI386                     = buildArch == I386
     , Z.zIsX8664                    = buildArch == X86_64
+    , Z.zOr                         = (||)
     , Z.zNot                        = not
     , Z.zManglePkgName              = showPkgName
 
@@ -56,8 +57,112 @@ generatePathsModule pkg_descr lbi clbi = Z.render Z.Z
     , 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])
diffCabal/src/Distribution/Simple/Build/PathsModule/Z.hs b/Cabal/src/Distribution/Simple/Build/PathsModule/Z.hs
index 6488ea061..a6cdc8e31 100644
--- a/libraries/Cabal/Cabal/src/Distribution/Simple/Build/PathsModule/Z.hs
+++ b/libraries/Cabal/Cabal/src/Distribution/Simple/Build/PathsModule/Z.hs
@@ -18,6 +18,14 @@ 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
@@ -45,10 +53,51 @@ render z_root = execWriter $ do
   tell "{-# OPTIONS_GHC -w #-}\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))
@@ -97,12 +146,15 @@ render z_root = execWriter $ do
   tell (zVersionDigits z_root)
   tell " []\n"
   tell "\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 "getBinDir, getLibDir, getDynLibDir, getDataDir, getLibexecDir, getSysconfDir :: IO FilePath\n"
+  if (zOr z_root (zNot z_root (zAbsolute z_root)) (zShouldEmitDataDir z_root))
+  then do
+    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
@@ -130,6 +182,7 @@ 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"
@@ -139,31 +192,37 @@ render z_root = execWriter $ do
     tell (zBindir z_root)
     tell ") `joinFileName` dirRel)\n"
     tell "\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 "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 "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 "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 "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 "getSysconfDir :: IO FilePath\n"
     tell "getSysconfDir = catchIO (getEnv \""
     tell (zManglePkgName z_root (zPackageName z_root))
     tell "_sysconfdir\") (\\_ -> getPrefixDirReloc $ "
@@ -177,72 +236,119 @@ 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 "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 "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 "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 "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 "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 "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 "getBinDir     :: IO FilePath\n"
         tell "getBinDir     = getPrefixDirRel $ "
         tell (zBindir z_root)
         tell "\n"
+        tell "getLibDir     :: IO FilePath\n"
         tell "getLibDir     = "
         tell (zLibdir z_root)
         tell "\n"
+        tell "getDynLibDir  :: IO FilePath\n"
         tell "getDynLibDir  = "
         tell (zDynlibdir z_root)
         tell "\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 "getLibexecDir :: IO FilePath\n"
         tell "getLibexecDir = "
         tell (zLibexecdir z_root)
         tell "\n"
+        tell "getSysconfDir :: IO FilePath\n"
         tell "getSysconfDir = "
         tell (zSysconfdir z_root)
         tell "\n"
diffcabal-dev-scripts/src/GenPathsModule.hs b/cabal-dev-scripts/src/GenPathsModule.hs
index e4b930635..9b978f284 100644
--- a/libraries/Cabal/cabal-dev-scripts/src/GenPathsModule.hs
+++ b/libraries/Cabal/cabal-dev-scripts/src/GenPathsModule.hs
@@ -41,6 +41,16 @@ $(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
         }
difftemplates/Paths_pkg.template.hs b/templates/Paths_pkg.template.hs
index 6bc6b7875..aa90a9382 100644
--- a/libraries/Cabal/templates/Paths_pkg.template.hs
+++ b/libraries/Cabal/templates/Paths_pkg.template.hs
@@ -9,10 +9,31 @@
 {% endif %}
 {-# OPTIONS_GHC -fno-warn-missing-import-lists #-}
 {-# OPTIONS_GHC -w #-}
-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 %}
@@ -51,12 +72,12 @@ catchIO = Exception.catch
 version :: Version
 version = Version {{ versionDigits }} []
 
+{% if or (not absolute) shouldEmitDataDir %}
 getDataFileName :: FilePath -> IO FilePath
 getDataFileName name = do
   dir <- getDataDir
   return (dir `joinFileName` name)
-
-getBinDir, getLibDir, getDynLibDir, getDataDir, getLibexecDir, getSysconfDir :: IO FilePath
+{% endif %}
 
 {% defblock function_defs %}
 minusFileName :: FilePath -> String -> FilePath
@@ -85,48 +106,93 @@ 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)
 
+getBinDir     :: IO FilePath
 getBinDir     = catchIO (getEnv "{{ manglePkgName packageName }}_bindir")     (\_ -> getPrefixDirReloc $ {{ bindir }})
+getLibDir     :: IO FilePath
 getLibDir     = catchIO (getEnv "{{ manglePkgName packageName }}_libdir")     (\_ -> getPrefixDirReloc $ {{ libdir }})
+getDynLibDir  :: IO FilePath
 getDynLibDir  = catchIO (getEnv "{{ manglePkgName packageName }}_dynlibdir")  (\_ -> getPrefixDirReloc $ {{ dynlibdir }})
+getDataDir    :: IO FilePath
 getDataDir    = catchIO (getEnv "{{ manglePkgName packageName }}_datadir")    (\_ -> getPrefixDirReloc $ {{ datadir }})
+getLibexecDir :: IO FilePath
 getLibexecDir = catchIO (getEnv "{{ manglePkgName packageName }}_libexecdir") (\_ -> getPrefixDirReloc $ {{ libexecdir }})
+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 }}
-
+getBinDir     :: IO FilePath
 getBinDir     = catchIO (getEnv "{{ manglePkgName packageName }}_bindir")     (\_ -> return bindir)
+
+{% if shouldEmitLibDir %}
+libdir     :: FilePath
+libdir     = {{ libdir }}
+getLibDir     :: IO FilePath
 getLibDir     = catchIO (getEnv "{{ manglePkgName packageName }}_libdir")     (\_ -> return libdir)
+{% endif %}
+
+{% if shouldEmitDynLibDir %}
+dynlibdir  :: FilePath
+dynlibdir  = {{ dynlibdir }}
+getDynLibDir  :: IO FilePath
 getDynLibDir  = catchIO (getEnv "{{ manglePkgName packageName }}_dynlibdir")  (\_ -> return dynlibdir)
+{% endif %}
+
+{% if shouldEmitDataDir %}
+datadir    :: FilePath
+datadir    = {{ datadir }}
+getDataDir    :: IO FilePath
 getDataDir    = catchIO (getEnv "{{ manglePkgName packageName }}_datadir")    (\_ -> return datadir)
+{% endif %}
+
+{% if shouldEmitLibexecDir %}
+libexecdir :: FilePath
+libexecdir = {{ libexecdir }}
+getLibexecDir :: IO FilePath
 getLibexecDir = catchIO (getEnv "{{ manglePkgName packageName }}_libexecdir") (\_ -> return libexecdir)
+{% endif %}
+
+{% if shouldEmitSysconfDir %}
+sysconfdir :: FilePath
+sysconfdir = {{ 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 }}
 
+getBinDir     :: IO FilePath
 getBinDir     = getPrefixDirRel $ {{ bindir }}
+getLibDir     :: IO FilePath
 getLibDir     = {{ libdir }}
+getDynLibDir  :: IO FilePath
 getDynLibDir  = {{ dynlibdir }}
+getDataDir    :: IO FilePath
 getDataDir    = catchIO (getEnv "{{ manglePkgName packageName }}_datadir")    (\_ -> {{ datadir }})
+getLibexecDir :: IO FilePath
 getLibexecDir = {{ libexecdir }}
+getSysconfDir :: IO FilePath
 getSysconfDir = {{ sysconfdir }}
 
 getPrefixDirRel :: FilePath -> IO FilePath