Refine the GHCI macro into HAVE[_{INTERNAL, EXTERNAL}]_INTERPRETER

As discussed in #16331, the GHCI macro, defined through 'ghci' flags
in ghc.cabal.in, ghc-bin.cabal.in and ghci.cabal.in, is supposed to indicate
whether GHC is built with support for an internal interpreter, that runs in
the same process. It is however overloaded in a few places to mean
"there is an interpreter available", regardless of whether it's an internal
or external interpreter.

For the sake of clarity and with the hope of more easily being able to
build stage 1 GHCs with external interpreter support, this patch splits
the previous GHCI macro into 3 different ones:

- HAVE_INTERNAL_INTERPRETER: GHC is built with an internal interpreter
- HAVE_EXTERNAL_INTERPRETER: GHC is built with support for external interpreters
- HAVE_INTERPRETER: HAVE_INTERNAL_INTERPRETER || HAVE_EXTERNAL_INTERPRETER

9 files changed, 30 insertions, 19 deletions

diff --git a/compiler/ghc.cabal.in b/compiler/ghc.cabal.in
index e8e6bf7317..e1f0bec2b0 100644
--- a/compiler/ghc.cabal.in
+++ b/compiler/ghc.cabal.in
@@ -25,6 +25,11 @@ Flag ghci
     Default: False
     Manual: True
 
+Flag ext-interp
+    Description: Support external interpreter
+    Default: True
+    Manual: True
+
 Flag stage1
     Description: Is this stage 1?
     Default: False
@@ -90,9 +95,15 @@ Library
                  -Wnoncanonical-monoid-instances
 
     if flag(ghci)
-        CPP-Options: -DGHCI
+        CPP-Options: -DHAVE_INTERNAL_INTERPRETER
         Include-Dirs: ../rts/dist/build @FFIIncludeDir@
 
+    if flag(ext-interp)
+        CPP-Options: -DHAVE_EXTERNAL_INTERPRETER
+
+    if flag(ghci) || flag(ext-interp)
+        CPP-Options: -DHAVE_INTERPRETER
+
     -- sanity-check to ensure not more than one integer flag is set
     if flag(integer-gmp) && flag(integer-simple)
         build-depends: invalid-cabal-flag-settings<0
diff --git a/compiler/ghci/GHCi.hs b/compiler/ghci/GHCi.hs
index 7ec07fec78..8795b30973 100644
--- a/compiler/ghci/GHCi.hs
+++ b/compiler/ghci/GHCi.hs
@@ -51,7 +51,7 @@ module GHCi
 import GhcPrelude
 
 import GHCi.Message
-#if defined(GHCI)
+#if defined(HAVE_INTERNAL_INTERPRETER)
 import GHCi.Run
 #endif
 import GHCi.RemoteTypes
@@ -157,7 +157,7 @@ Other Notes on Remote GHCi
   * Note [Remote Template Haskell] in libraries/ghci/GHCi/TH.hs
 -}
 
-#if !defined(GHCI)
+#if !defined(HAVE_INTERNAL_INTERPRETER)
 needExtInt :: IO a
 needExtInt = throwIO
   (InstallationError "this operation requires -fexternal-interpreter")
@@ -175,7 +175,7 @@ iservCmd hsc_env@HscEnv{..} msg
        uninterruptibleMask_ $ do -- Note [uninterruptibleMask_]
          iservCall iserv msg
  | otherwise = -- Just run it directly
-#if defined(GHCI)
+#if defined(HAVE_INTERNAL_INTERPRETER)
    run msg
 #else
    needExtInt
@@ -391,7 +391,7 @@ lookupSymbol hsc_env@HscEnv{..} str
                writeIORef iservLookupSymbolCache $! addToUFM cache str p
                return (Just p)
  | otherwise =
-#if defined(GHCI)
+#if defined(HAVE_INTERNAL_INTERPRETER)
    fmap fromRemotePtr <$> run (LookupSymbol (unpackFS str))
 #else
    needExtInt
@@ -642,7 +642,7 @@ wormholeRef dflags _r
   | gopt Opt_ExternalInterpreter dflags
   = throwIO (InstallationError
       "this operation requires -fno-external-interpreter")
-#if defined(GHCI)
+#if defined(HAVE_INTERNAL_INTERPRETER)
   | otherwise
   = localRef _r
 #else
diff --git a/compiler/main/DynFlags.hs b/compiler/main/DynFlags.hs
index 5217fced5f..0b2b32d5bb 100644
--- a/compiler/main/DynFlags.hs
+++ b/compiler/main/DynFlags.hs
@@ -320,8 +320,8 @@ import qualified EnumSet
 import GHC.Foreign (withCString, peekCString)
 import qualified GHC.LanguageExtensions as LangExt
 
-#if defined(GHCI)
-import Foreign (Ptr) -- needed for 2nd stage
+#if defined(HAVE_INTERPRETER)
+import Foreign (Ptr)
 #endif
 
 -- Note [Updating flag description in the User's Guide]
@@ -4342,7 +4342,7 @@ supportedExtensions :: [String]
 supportedExtensions = concatMap toFlagSpecNamePair xFlags
   where
     toFlagSpecNamePair flg
-#if !defined(GHCI)
+#if !defined(HAVE_INTERPRETER)
       -- IMPORTANT! Make sure that `ghc --supported-extensions` omits
       -- "TemplateHaskell"/"QuasiQuotes" when it's known not to work out of the
       -- box. See also GHC #11102 and #16331 for more details about
diff --git a/compiler/main/DynamicLoading.hs b/compiler/main/DynamicLoading.hs
index 0a5264e3f2..64cc0a1216 100644
--- a/compiler/main/DynamicLoading.hs
+++ b/compiler/main/DynamicLoading.hs
@@ -3,7 +3,7 @@
 -- | Dynamically lookup up values from modules and loading them.
 module DynamicLoading (
         initializePlugins,
-#if defined(GHCI)
+#if defined(HAVE_INTERPRETER)
         -- * Loading plugins
         loadFrontendPlugin,
 
@@ -27,7 +27,7 @@ module DynamicLoading (
 import GhcPrelude
 import DynFlags
 
-#if defined(GHCI)
+#if defined(HAVE_INTERPRETER)
 import Linker           ( linkModule, getHValue )
 import GHCi             ( wormhole )
 import SrcLoc           ( noSrcSpan )
@@ -76,7 +76,7 @@ import Control.Monad    ( unless )
 -- actual compilation starts. Idempotent operation. Should be re-called if
 -- pluginModNames or pluginModNameOpts changes.
 initializePlugins :: HscEnv -> DynFlags -> IO DynFlags
-#if !defined(GHCI)
+#if !defined(HAVE_INTERPRETER)
 initializePlugins _ df
   = do let pluginMods = pluginModNames df
        unless (null pluginMods) (pluginError pluginMods)
@@ -96,7 +96,7 @@ initializePlugins hsc_env df
 #endif
 
 
-#if defined(GHCI)
+#if defined(HAVE_INTERPRETER)
 
 loadPlugins :: HscEnv -> IO [LoadedPlugin]
 loadPlugins hsc_env
diff --git a/compiler/rename/RnExpr.hs b/compiler/rename/RnExpr.hs
index 7b00a62403..98d487df2d 100644
--- a/compiler/rename/RnExpr.hs
+++ b/compiler/rename/RnExpr.hs
@@ -208,7 +208,7 @@ rnExpr (NegApp _ e _)
 
 ------------------------------------------
 -- Template Haskell extensions
--- Don't ifdef-GHCI them because we want to fail gracefully
+-- Don't ifdef-HAVE_INTERPRETER them because we want to fail gracefully
 -- (not with an rnExpr crash) in a stage-1 compiler.
 rnExpr e@(HsBracket _ br_body) = rnBracket e br_body
 
diff --git a/compiler/simplCore/SimplCore.hs b/compiler/simplCore/SimplCore.hs
index ade9816a1b..572084c420 100644
--- a/compiler/simplCore/SimplCore.hs
+++ b/compiler/simplCore/SimplCore.hs
@@ -462,7 +462,7 @@ doCorePass (CoreDoRuleCheck phase pat)  = ruleCheckPass phase pat
 doCorePass CoreDoNothing                = return
 doCorePass (CoreDoPasses passes)        = runCorePasses passes
 
-#if defined(GHCI)
+#if defined(HAVE_INTERPRETER)
 doCorePass (CoreDoPluginPass _ pass) = {-# SCC "Plugin" #-} pass
 #else
 doCorePass pass@CoreDoPluginPass {}  = pprPanic "doCorePass" (ppr pass)
diff --git a/compiler/typecheck/TcAnnotations.hs b/compiler/typecheck/TcAnnotations.hs
index 050c5db977..60f21ccce7 100644
--- a/compiler/typecheck/TcAnnotations.hs
+++ b/compiler/typecheck/TcAnnotations.hs
@@ -28,7 +28,7 @@ import Outputable
 -- Some platforms don't support the external interpreter, and
 -- compilation on those platforms shouldn't fail just due to
 -- annotations
-#ifndef GHCI
+#if !defined(HAVE_INTERNAL_INTERPRETER)
 tcAnnotations :: [LAnnDecl GhcRn] -> TcM [Annotation]
 tcAnnotations anns = do
   dflags <- getDynFlags
diff --git a/compiler/typecheck/TcPluginM.hs b/compiler/typecheck/TcPluginM.hs
index a112003ef9..3785a4aac5 100644
--- a/compiler/typecheck/TcPluginM.hs
+++ b/compiler/typecheck/TcPluginM.hs
@@ -3,7 +3,7 @@
 -- access select functions of the 'TcM', principally those to do with
 -- reading parts of the state.
 module TcPluginM (
-#if defined(GHCI)
+#if defined(HAVE_INTERPRETER)
         -- * Basic TcPluginM functionality
         TcPluginM,
         tcPluginIO,
@@ -52,7 +52,7 @@ module TcPluginM (
 #endif
     ) where
 
-#if defined(GHCI)
+#if defined(HAVE_INTERPRETER)
 import GhcPrelude
 
 import qualified TcRnMonad as TcM
diff --git a/compiler/utils/Util.hs b/compiler/utils/Util.hs
index b9a138902f..5770f2ffdc 100644
--- a/compiler/utils/Util.hs
+++ b/compiler/utils/Util.hs
@@ -188,7 +188,7 @@ the flags are off.
 -}
 
 ghciSupported :: Bool
-#if defined(GHCI)
+#if defined(HAVE_INTERNAL_INTERPRETER)
 ghciSupported = True
 #else
 ghciSupported = False