[Git][ghc/ghc][wip/spj-reinstallable-base2] 4 commits: Document in commit message cycle with unpack

7 May 2026

Rodrigo Mesquita pushed to branch wip/spj-reinstallable-base2 at Glasgow Haskell Compiler / GHC


Commits:
ede44664 by Rodrigo Mesquita at 2026-05-06T14:06:59+01:00
Document in commit message cycle with unpack

- GHC.Internal.CString defines a known-key name unpackCString# (unpackCStringIdKey)
- IIUC, this known-key is looked up essentially for all modules, as long as there’s some literal string in it (coreStringLit uses unpackCStringIdKey)
- GHC.Internal.Types has literal strings, so it needs to lookup unpackCString. It fails with this error:

libraries/ghc-internal/src/GHC/Internal/Types.hs:653:1: error: [GHC-99040]
   • Could not find known-key entity ‘unpackCString#’
       in the top-level environment (unqualified, or qualified as Rebindable)
       Consider importing it
       Call stack:
             lookupKnownGRE, called at compiler/GHC/Iface/Load.hs:196:10 in ghc-10.1-inplace:GHC.Iface.Load
             […]
             tcLookupKnownKeyId, called at compiler/GHC/Tc/Solver/Monad.hs:1192:36 in ghc-10.1-inplace:GHC.Tc.Solver.Monad
   • In the kind ‘k’
     In the class declaration for ‘Coercible’
   |
653 | class Coercible (a :: k) (b :: k)
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

- This makes sense, unpackCString must be in scope (this is GHC.Internal.Types, i.e. ghc-internal, i.e. compiled with -frebindable-known-names)
	- For GHC.Internal.Types, unpackCString is looked up to later construct a string expression in `evCallStack`
- Thus, GHC.Internal.Types MUST import unpackCString from GHC.Internal.String
- BUT! GHC.Internal.CString imports GHC.Internal.Types…

- - - - -
61d6b31d by Rodrigo Mesquita at 2026-05-06T14:20:35+01:00
ptrTyConName, funPtrTyConName

- - - - -
6decd81e by Rodrigo Mesquita at 2026-05-06T14:24:17+01:00
word8TyConName is wired in

- - - - -
9dec147e by Rodrigo Mesquita at 2026-05-06T17:29:51+01:00
pluginTyConName, frontendPluginTyConName

- - - - -


7 changed files:

- compiler/GHC/Builtin/KnownKeys.hs
- compiler/GHC/Builtin/WiredIn/Types.hs
- compiler/GHC/Driver/Plugins.hs
- compiler/GHC/HsToCore/Foreign/C.hs
- compiler/GHC/Runtime/Loader.hs
- libraries/base/src/GHC/Essentials.hs
- libraries/ghc-internal/src/GHC/Internal/Ptr.hs


Changes:

=====================================
compiler/GHC/Builtin/KnownKeys.hs
=====================================
@@ -163,6 +163,8 @@ knownKeyRdrName key = knownOccRdrName (knownKeyOccName key)
 This section tells what the compiler knows about the association of
 names with uniques.  These ones are the *non* wired-in ones.  The
 wired in ones are defined in GHC.Builtin.Types etc.
+
+See Note [Overview of known entities] in GHC.Builtin
 -}
 
 knownKeyTable :: [(OccName, KnownKey)]
@@ -269,6 +271,10 @@ knownKeyTable
     , (mkDataOcc ":$$:",      typeErrorVAppendDataConKey)
     , (mkDataOcc "ShowType",  typeErrorShowTypeDataConKey)
 
+    -- Plugins
+    , (mkTcOcc "Plugin", pluginTyConKey)
+    , (mkTcOcc "FrontendPlugin", frontendPluginTyConKey)
+
     -- Base strings Strings
     , (mkVarOcc "unpackCString#",     unpackCStringIdKey)
     , (mkVarOcc "unpackCStringUtf8#", unpackCStringUtf8IdKey)
@@ -367,16 +373,9 @@ basicKnownKeyNames
         starArrStarKindRepName,
         starArrStarArrStarKindRepName,
         constraintKindRepName,
-        -- FFI primitive types that are not wired-in.
-        ptrTyConName, funPtrTyConName,
-        word8TyConName,
-
-        -- Plugins
-        pluginTyConName
-        , frontendPluginTyConName
 
         -- Unsafe coercion proofs
-        , unsafeCoercePrimName
+        unsafeCoercePrimName
     ]
 
 
@@ -445,23 +444,6 @@ unsafeCoercePrimName    = varQual gHC_INTERNAL_UNSAFE_COERCE (fsLit "unsafeCoerc
 genericClassKeys :: [KnownKey]
 genericClassKeys = [genClassKey, gen1ClassKey]

--- Word module
-word8TyConName :: Name
-word8TyConName = tcQual  gHC_INTERNAL_WORD (fsLit "Word8")  word8TyConKey
-
--- PrelPtr module
-ptrTyConName, funPtrTyConName :: Name
-ptrTyConName      = tcQual   gHC_INTERNAL_PTR (fsLit "Ptr")    ptrTyConKey
-funPtrTyConName   = tcQual   gHC_INTERNAL_PTR (fsLit "FunPtr") funPtrTyConKey
-
--- plugins
-pLUGINS :: Module
-pLUGINS = mkThisGhcModule (fsLit "GHC.Driver.Plugins")
-pluginTyConName :: Name
-pluginTyConName = tcQual pLUGINS (fsLit "Plugin") pluginTyConKey
-frontendPluginTyConName :: Name
-frontendPluginTyConName = tcQual pLUGINS (fsLit "FrontendPlugin") frontendPluginTyConKey
-
 {-
 ************************************************************************
 *                                                                      *


=====================================
compiler/GHC/Builtin/WiredIn/Types.hs
=====================================
@@ -58,7 +58,7 @@ module GHC.Builtin.WiredIn.Types (
         wordTyCon, wordDataCon, wordTyConName, wordTy,
 
         -- * Word8
-        word8TyCon, word8DataCon, word8Ty,
+        word8TyCon, word8DataCon, word8TyConName, word8Ty,
 
         -- * List
         listTyCon, listTyConName, listTyConKey,
@@ -395,10 +395,11 @@ nothingDataConName = mkWiredInDataConName UserSyntax gHC_INTERNAL_MAYBE (fsLit "
 justDataConName    = mkWiredInDataConName UserSyntax gHC_INTERNAL_MAYBE (fsLit "Just")
                                           justDataConKey justDataCon
 
-wordTyConName, wordDataConName, word8DataConName :: Name
-wordTyConName      = mkWiredInTyConName   UserSyntax gHC_TYPES (fsLit "Word")   wordTyConKey     wordTyCon
-wordDataConName    = mkWiredInDataConName UserSyntax gHC_TYPES (fsLit "W#")     wordDataConKey   wordDataCon
-word8DataConName   = mkWiredInDataConName UserSyntax gHC_INTERNAL_WORD  (fsLit "W8#")    word8DataConKey  word8DataCon
+wordTyConName, wordDataConName, word8TyConName, word8DataConName :: Name
+wordTyConName      = mkWiredInTyConName   UserSyntax gHC_TYPES         (fsLit "Word")   wordTyConKey     wordTyCon
+wordDataConName    = mkWiredInDataConName UserSyntax gHC_TYPES         (fsLit "W#")     wordDataConKey   wordDataCon
+word8TyConName     = mkWiredInTyConName   UserSyntax gHC_INTERNAL_WORD (fsLit "Word8")  word8TyConKey    word8TyCon
+word8DataConName   = mkWiredInDataConName UserSyntax gHC_INTERNAL_WORD (fsLit "W8#")    word8DataConKey  word8DataCon
 
 floatTyConName, floatDataConName, doubleTyConName, doubleDataConName :: Name
 floatTyConName     = mkWiredInTyConName   UserSyntax gHC_TYPES (fsLit "Float")  floatTyConKey    floatTyCon


=====================================
compiler/GHC/Driver/Plugins.hs
=====================================
@@ -5,6 +5,12 @@
 {-# LANGUAGE UnboxedTuples #-}
 #endif
 
+#if __GLASGOW_HASKELL__ > 1000
+{-# OPTIONS_GHC -fdefines-known-key-names #-}
+  -- 'Plugin' and 'FrontendPlugin' are known-key names
+  --  (they have a fixed known unique) (from GHC 10.2)
+  -- See Note [Overview of known entities] in GHC.Builtin
+#endif
 
 -- | Definitions for writing /plugins/ for GHC. Plugins can hook into
 -- several areas of the compiler. See the 'Plugin' type. These plugins


=====================================
compiler/GHC/HsToCore/Foreign/C.hs
=====================================
@@ -365,7 +365,7 @@ toCType t = case f False t of
            -- If the inner type is void-based, we collapse the pointer
            -- chain to just "void*". See Note [Collapsing void pointer chains].
            | Just (ptr, [t']) <- splitTyConApp_maybe t
-           , tyConName ptr `elem` [ptrTyConName, funPtrTyConName]
+           , tyConUnique ptr `elem` [ptrTyConKey, funPtrTyConKey]
               = case f True t' of
                 (mh, True, _) ->
                     (mh, True, text "void*")


=====================================
compiler/GHC/Runtime/Loader.hs
=====================================
@@ -37,7 +37,7 @@ import GHC.Rename.Names ( gresFromAvails )
 
 import GHC.Tc.Utils.Monad      ( initTcInteractive, initIfaceTcRn )
 import GHC.Iface.Load          ( loadPluginInterface, cannotFindModule )
-import GHC.Builtin.KnownKeys ( pluginTyConName, frontendPluginTyConName )
+import GHC.Builtin.KnownKeys ( pluginTyConKey, frontendPluginTyConKey )
 
 import GHC.Driver.Env
 import GHCi.RemoteTypes     ( HValue )
@@ -47,7 +47,7 @@ import GHC.Core.TyCon       ( TyCon(tyConName) )
 
 
 import GHC.Types.SrcLoc        ( noSrcSpan )
-import GHC.Types.Name    ( Name, nameModule, nameModule_maybe )
+import GHC.Types.Name    ( Name, nameModule, nameModule_maybe, KnownKey, mkKnownKeyName, mkTcOcc )
 import GHC.Types.Id      ( idType )
 import GHC.Types.PkgQual
 import GHC.Types.TyThing
@@ -75,6 +75,7 @@ import GHC.Linker.Types
 import Data.List (unzip4)
 import GHC.Iface.Errors.Ppr
 import GHC.Driver.Monad
+import GHC.Builtin.Modules
 
 {- Note [Timing of plugin initialization]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -170,12 +171,13 @@ loadPlugins hsc_env
       where
         options = [ option | (opt_mod_nm, option) <- pluginModNameOpts dflags
                             , opt_mod_nm == mod_nm ]
+    pluginTyConName = mkKnownKeyGhcPluginsName (mkTcOcc "Plugin") pluginTyConKey
     loadPlugin = loadPlugin' (mkVarOccFS (fsLit "plugin")) pluginTyConName hsc_env
 
-
 loadFrontendPlugin :: HscEnv -> ModuleName -> IO (FrontendPlugin, [LinkableUsage], PkgsLoaded)
 loadFrontendPlugin hsc_env mod_name = do
     checkExternalInterpreter hsc_env
+    let frontendPluginTyConName = mkKnownKeyGhcPluginsName (mkTcOcc "FrontendPlugin") frontendPluginTyConKey
     (plugin, _iface, links, pkgs)
       <- loadPlugin' (mkVarOccFS (fsLit "frontendPlugin")) frontendPluginTyConName
            hsc_env mod_name
@@ -188,6 +190,10 @@ checkExternalInterpreter hsc_env = case interpInstance <$> hsc_interp hsc_env of
     -> throwIO (InstallationError "Plugins require -fno-external-interpreter")
   _ -> pure ()
 
+mkKnownKeyGhcPluginsName :: OccName -> KnownKey -> Name
+mkKnownKeyGhcPluginsName occ kk =
+  mkKnownKeyName kk (mkThisGhcModule (fsLit "GHC.Driver.Plugins")) occ noSrcSpan
+
 loadPlugin' :: OccName -> Name -> HscEnv -> ModuleName -> IO (a, ModIface, [LinkableUsage], PkgsLoaded)
 loadPlugin' occ_name plugin_name hsc_env mod_name
   = do { let plugin_rdr_name = mkRdrQual mod_name occ_name


=====================================
libraries/base/src/GHC/Essentials.hs
=====================================
@@ -76,6 +76,7 @@ module GHC.Essentials
     , Void
 
     -- FFI
+    , Ptr, FunPtr
     , ConstPtr
 
     -- Show internals
@@ -302,6 +303,7 @@ import GHC.Internal.GHCi
 import GHC.Internal.Desugar (toAnnotationWrapper)
 import GHC.Internal.Stack.Types
 import GHC.Internal.Exception.Context
+import GHC.Internal.Ptr
 import GHC.Internal.Foreign.C.ConstPtr
 #if defined(javascript_HOST_ARCH)
 import GHC.Internal.JS.Prim (unsafeUnpackJSStringUtf8##)


=====================================
libraries/ghc-internal/src/GHC/Internal/Ptr.hs
=====================================
@@ -2,6 +2,7 @@
 {-# LANGUAGE CPP, NoImplicitPrelude, MagicHash, RoleAnnotations #-}
 {-# LANGUAGE UnboxedTuples #-}
 {-# OPTIONS_HADDOCK not-home #-}
+{-# OPTIONS_GHC -fdefines-known-key-names #-}
 
 -----------------------------------------------------------------------------
 -- |



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/64ed2f412343e5cdc5c0694b79f61eb...

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Rodrigo Mesquita (＠alt-romes)

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