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Zubin pushed to branch wip/26135 at Glasgow Haskell Compiler / GHC

Commits:

6997abfc

by Zubin Duggal at 2025-06-24T16:32:03+05:30

compiler: Export a version of `newNameCache` that is not prone to footguns.
`newNameCache` must be initialized with both a non-"reserved" unique tag, as well
as a list of known key names. Failing to do so results in hard to debug unique conflicts.

It is difficult for API users to tell which unique tags are safe to use. So instead of leaving
this up to the user to decide, we now export a version of `newNameCache` which uses a guaranteed
non-reserved unique tag. In fact, this is now the way the unique tag is initialized for all invocations
of the compiler.

The original version of `newNameCache` is now exported as `newNameCache'` for advanced users.

We also deprecate `initNameCache` as it is also prone to footguns and is completely subsumed in
functionality by `newNameCache` and `newNameCache'`.

Fixes #26135 and #26055

3 changed files:

compiler/GHC/Driver/Main.hs
compiler/GHC/Types/Name/Cache.hs
testsuite/tests/hiefile/should_run/TestUtils.hs

Changes:

compiler/GHC/Driver/Main.hs

@@ -245,7 +245,7 @@ import GHC.Types.IPE
  import GHC.Types.SourceFile
  import GHC.Types.SrcLoc
  import GHC.Types.Name
 -import GHC.Types.Name.Cache ( newNameCache, knownKeysOrigNameCache )
 +import GHC.Types.Name.Cache ( newNameCache )
  import GHC.Types.Name.Reader
  import GHC.Types.Name.Ppr
  import GHC.Types.TyThing
@@ -322,7 +322,7 @@ newHscEnv top_dir dflags = do
  newHscEnvWithHUG :: FilePath -> DynFlags -> UnitId -> HomeUnitGraph -> IO HscEnv
  newHscEnvWithHUG top_dir top_dynflags cur_unit home_unit_graph = do
 -    nc_var  <- newNameCache 'r' knownKeysOrigNameCache
 +    nc_var  <- newNameCache
      fc_var  <- initFinderCache
      logger  <- initLogger
      tmpfs   <- initTmpFs

compiler/GHC/Types/Name/Cache.hs

@@ -4,6 +4,7 @@
  module GHC.Types.Name.Cache
    ( NameCache (..)
    , newNameCache
 +  , newNameCache'
    , initNameCache
    , takeUniqFromNameCache
    , updateNameCache'
@@ -140,11 +141,27 @@ extendOrigNameCache nc mod occ name
    where
      combine _ occ_env = extendOccEnv occ_env occ name
 -newNameCache :: Char -> OrigNameCache -> IO NameCache
 -newNameCache c nc = NameCache c <$> newMVar nc
 +-- | Initialize a new name cache
 +newNameCache :: IO NameCache
 +newNameCache = newNameCache' 'r' knownKeysOrigNameCache
 +-- | This is a version of `newNameCache` that lets you supply your
 +-- own unique tag and set of known key names. This can go wrong if the tag
 +-- supplied is one reserved by GHC for internal purposes. See #26055 for
 +-- an example.
 +--
 +-- Use `newNameCache` when possible.
 +newNameCache' :: Char -> OrigNameCache -> IO NameCache
 +newNameCache' c nc = NameCache c <$> newMVar nc
++
 +-- | This takes a tag for uniques to be generated and the list of knownKeyNames
 +-- These must be initialized properly to ensure that names generated from this
 +-- NameCache do not conflict with known key names.
 +--
 +-- Use `newNameCache` or `newNameCache'` instead
 +{-# DEPRECATED initNameCache "Use newNameCache or newNameCache' instead" #-}
  initNameCache :: Char -> [Name] -> IO NameCache
 -initNameCache c names = newNameCache c (initOrigNames names)
 +initNameCache c names = newNameCache' c (initOrigNames names)
  initOrigNames :: [Name] -> OrigNameCache
  initOrigNames names = foldl' extendOrigNameCache' emptyModuleEnv names

testsuite/tests/hiefile/should_run/TestUtils.hs

@@ -25,9 +25,6 @@ import GHC.Iface.Ext.Utils
  import GHC.Driver.Session
  import GHC.SysTools
 -makeNc :: IO NameCache
 -makeNc = initNameCache 'z' []
+-
  dynFlagsForPrinting :: String -> IO DynFlags
  dynFlagsForPrinting libdir = do
    systemSettings <- initSysTools libdir
@@ -37,7 +34,7 @@ readTestHie :: FilePath -> IO (DynFlags, HieFile)
  readTestHie fp = do
    libdir:_ <- getArgs
    df <- dynFlagsForPrinting libdir
 -  nc <- makeNc
 +  nc <- newNameCache
    hfr <- readHieFile nc fp
    pure (df, hie_file_result hfr)