GHC/Linker/MacOS.hs

    module GHC.Linker.MacOS
       ( runInjectRPaths
       , getUnitFrameworkOpts
       , getFrameworkOpts
       , loadFramework
       )
    where

    import GHC.Prelude
    import GHC.Platform

    import GHC.Driver.Session

    import GHC.Unit.Types
    import GHC.Unit.State
    import GHC.Unit.Env

    import GHC.SysTools.Tasks

    import GHC.Runtime.Interpreter

    import GHC.Utils.Exception
    import GHC.Utils.Logger

    import Data.List (isPrefixOf, nub, sort, intersperse, intercalate)
    import Data.Char
    import Data.Maybe
    import Control.Monad (join, forM, filterM, void)
    import System.Directory (doesFileExist, getHomeDirectory)
    import System.FilePath ((</>), (<.>))
    import Text.ParserCombinators.ReadP as Parser

    -- | On macOS we rely on the linkers @-dead_strip_dylibs@ flag to remove unused
    -- libraries from the dynamic library.  We do this to reduce the number of load
    -- commands that end up in the dylib, and has been limited to 32K (32768) since
    -- macOS Sierra (10.14).
    --
    -- @-dead_strip_dylibs@ does not dead strip @-rpath@ entries, as such passing
    -- @-l@ and @-rpath@ to the linker will result in the unnecesasry libraries not
    -- being included in the load commands, however the @-rpath@ entries are all
    -- forced to be included.  This can lead to 100s of @-rpath@ entries being
    -- included when only a handful of libraries end up being truly linked.
    --
    -- Thus after building the library, we run a fixup phase where we inject the
    -- @-rpath@ for each found library (in the given library search paths) into the
    -- dynamic library through @-add_rpath@.
    --
    -- See Note [Dynamic linking on macOS]
    runInjectRPaths :: Logger -> DynFlags -> [FilePath] -> FilePath -> IO ()
    -- Make sure to honour -fno-use-rpaths if set on darwin as well see #20004
    runInjectRPaths _ dflags _ _ | not (gopt Opt_RPath dflags) = return ()
    runInjectRPaths logger dflags lib_paths dylib = do
      info <- lines <$> askOtool logger dflags Nothing [Option "-L", Option dylib]
      -- filter the output for only the libraries. And then drop the @rpath prefix.
      let libs = fmap (drop 7) $ filter (isPrefixOf "@rpath") $ fmap (head.words) $ info
      -- find any pre-existing LC_PATH items
      info <- lines <$> askOtool logger dflags Nothing [Option "-l", Option dylib]
      let paths = mapMaybe get_rpath info
          lib_paths' = [ p | p <- lib_paths, not (p `elem` paths) ]
      -- only find those rpaths, that aren't already in the library.
      rpaths <- nub . sort . join <$> forM libs (\f -> filterM (\l -> doesFileExist (l </> f)) lib_paths')
      -- inject the rpaths
      case rpaths of
        [] -> return ()
        _  -> runInstallNameTool logger dflags $ map Option $ "-add_rpath":(intersperse "-add_rpath" rpaths) ++ [dylib]

    get_rpath :: String -> Maybe FilePath
    get_rpath l = case readP_to_S rpath_parser l of
                    [(rpath, "")] -> Just rpath
                    _ -> Nothing

    rpath_parser :: ReadP FilePath
    rpath_parser = do
      skipSpaces
      void $ string "path"
      void $ many1 (satisfy isSpace)
      rpath <- many get
      void $ many1 (satisfy isSpace)
      void $ string "(offset "
      void $ munch1 isDigit
      void $ Parser.char ')'
      skipSpaces
      return rpath

    getUnitFrameworkOpts :: UnitEnv -> [UnitId] -> IO [String]
    getUnitFrameworkOpts unit_env dep_packages
      | platformUsesFrameworks (ue_platform unit_env) = do
            ps <- mayThrowUnitErr (preloadUnitsInfo' unit_env dep_packages)
            let pkg_framework_path_opts = map ("-F" ++) (collectFrameworksDirs ps)
                pkg_framework_opts      = concat [ ["-framework", fw]
                                                 | fw <- collectFrameworks ps
                                                 ]
            return (pkg_framework_path_opts ++ pkg_framework_opts)

      | otherwise = return []

    getFrameworkOpts :: DynFlags -> Platform -> [String]
    getFrameworkOpts dflags platform
      | platformUsesFrameworks platform = framework_path_opts ++ framework_opts
      | otherwise = []
      where
        framework_paths     = frameworkPaths dflags
        framework_path_opts = map ("-F" ++) framework_paths

        frameworks     = cmdlineFrameworks dflags
        -- reverse because they're added in reverse order from the cmd line:
        framework_opts = concat [ ["-framework", fw]
                                | fw <- reverse frameworks ]

    {-
    Note [macOS Big Sur dynamic libraries]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    macOS Big Sur makes the following change to how frameworks are shipped
    with the OS:

    > New in macOS Big Sur 11 beta, the system ships with a built-in
    > dynamic linker cache of all system-provided libraries.  As part of
    > this change, copies of dynamic libraries are no longer present on
    > the filesystem.  Code that attempts to check for dynamic library
    > presence by looking for a file at a path or enumerating a directory
    > will fail.  Instead, check for library presence by attempting to
    > dlopen() the path, which will correctly check for the library in the
    > cache. (62986286)

    (https://developer.apple.com/documentation/macos-release-notes/macos-big-sur-11-beta-release-notes/)

    Therefore, the previous method of checking whether a library exists
    before attempting to load it makes GHC.Linker.MacOS.loadFramework
    fail to find frameworks installed at /System/Library/Frameworks.
    Instead, any attempt to load a framework at runtime, such as by
    passing -framework OpenGL to runghc or running code loading such a
    framework with GHCi, fails with a 'not found' message.

    GHC.Linker.MacOS.loadFramework now opportunistically loads the
    framework libraries without checking for their existence first,
    failing only if all attempts to load a given framework from any of the
    various possible locations fail.  See also #18446, which this change
    addresses.
    -}

    -- Darwin / MacOS X only: load a framework
    -- a framework is a dynamic library packaged inside a directory of the same
    -- name. They are searched for in different paths than normal libraries.
    loadFramework :: Interp -> [FilePath] -> FilePath -> IO (Maybe String)
    loadFramework interp extraPaths rootname
       = do { either_dir <- tryIO getHomeDirectory
            ; let homeFrameworkPath = case either_dir of
                                      Left _ -> []
                                      Right dir -> [dir </> "Library/Frameworks"]
                  ps = extraPaths ++ homeFrameworkPath ++ defaultFrameworkPaths
            ; errs <- findLoadDLL ps []
            ; return $ fmap (intercalate ", ") errs
            }
       where
         fwk_file = rootname <.> "framework" </> rootname

         -- sorry for the hardcoded paths, I hope they won't change anytime soon:
         defaultFrameworkPaths = ["/Library/Frameworks", "/System/Library/Frameworks"]

         -- Try to call loadDLL for each candidate path.
         --
         -- See Note [macOS Big Sur dynamic libraries]
         findLoadDLL [] errs =
           -- Tried all our known library paths, but dlopen()
           -- has no built-in paths for frameworks: give up
           return $ Just errs
         findLoadDLL (p:ps) errs =
           do { dll <- loadDLL interp (p </> fwk_file)
              ; case dll of
                  Nothing  -> return Nothing
                  Just err -> findLoadDLL ps ((p ++ ": " ++ err):errs)
              }