base: Ensure that encoding global variables aren't inlinedwip/T17970

As noted in #17970, these (e.g. `getFileSystemEncoding` and
`setFileSystemEncoding`) previously had unfoldings, which would
break their global-ness.

While not strictly necessary, I also add a NOINLINE on
`initLocaleEncoding` since it is used in `System.IO`, ensuring that we
only system's query the locale encoding once.

Fixes #17970.

1 files changed, 10 insertions, 0 deletions

diff --git a/libraries/base/GHC/IO/Encoding.hs b/libraries/base/GHC/IO/Encoding.hs
index d607b7e7b5..9bad2c6b58 100644
--- a/libraries/base/GHC/IO/Encoding.hs
+++ b/libraries/base/GHC/IO/Encoding.hs
@@ -107,6 +107,7 @@ utf32be = UTF32.utf32be
 --
 -- @since 4.5.0.0
 getLocaleEncoding :: IO TextEncoding
+{-# NOINLINE getLocaleEncoding #-}
 
 -- | The Unicode encoding of the current locale, but allowing arbitrary
 -- undecodable bytes to be round-tripped through it.
@@ -120,6 +121,7 @@ getLocaleEncoding :: IO TextEncoding
 --
 -- @since 4.5.0.0
 getFileSystemEncoding :: IO TextEncoding
+{-# NOINLINE getFileSystemEncoding #-}
 
 -- | The Unicode encoding of the current locale, but where undecodable
 -- bytes are replaced with their closest visual match. Used for
@@ -127,9 +129,13 @@ getFileSystemEncoding :: IO TextEncoding
 --
 -- @since 4.5.0.0
 getForeignEncoding :: IO TextEncoding
+{-# NOINLINE getForeignEncoding #-}
 
 -- | @since 4.5.0.0
 setLocaleEncoding, setFileSystemEncoding, setForeignEncoding :: TextEncoding -> IO ()
+{-# NOINLINE setLocaleEncoding #-}
+{-# NOINLINE setFileSystemEncoding #-}
+{-# NOINLINE setForeignEncoding #-}
 
 (getLocaleEncoding, setLocaleEncoding)         = mkGlobal initLocaleEncoding
 (getFileSystemEncoding, setFileSystemEncoding) = mkGlobal initFileSystemEncoding
@@ -139,9 +145,13 @@ mkGlobal :: a -> (IO a, a -> IO ())
 mkGlobal x = unsafePerformIO $ do
     x_ref <- newIORef x
     return (readIORef x_ref, writeIORef x_ref)
+{-# NOINLINE mkGlobal #-}
 
 -- | @since 4.5.0.0
 initLocaleEncoding, initFileSystemEncoding, initForeignEncoding :: TextEncoding
+{-# NOINLINE initLocaleEncoding #-}
+-- N.B. initLocaleEncoding is exported for use in System.IO.localeEncoding.
+-- NOINLINE ensures that this result is shared.
 
 #if !defined(mingw32_HOST_OS)
 -- It is rather important that we don't just call Iconv.mkIconvEncoding here