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Hi,

 

Is there a migration guide for GHC API clients for the new “multiple home units” feature?

 

In particular, I have the following two functions in my code that used to interact with related features of GHC:

 

addUnit :: UnitInfo -> HscEnv -> HscEnv

addUnit unitInfo@GenericUnitInfo{..} = modifyUnitState $ \us -> us

    { packageNameMap = addToUFM (packageNameMap us) unitPackageName unitId

    , unitInfoMap = M.insert unitId unitInfo $ unitInfoMap us

    }

 

registerModule :: (GhcMonad m) => ModDetails -> ModIface -> m ()

registerModule details iface = modifySession $ extendHpt . addModule

  where

    hmi = HomeModInfo iface details Nothing

 

    mod = mi_module iface

    modOrig = ModOrigin (Just True) [] [] True

 

    addModule = modifyUnitState $ \us -> us

        { moduleNameProvidersMap = M.insert (moduleName mod) (M.singleton mod modOrig) $ moduleNameProvidersMap us

        }

 

    extendHpt env = env

        { hsc_unit_env = let ue = hsc_unit_env env in ue

            { ue_hpt = addHomeModInfoToHpt hmi (hsc_HPT env)

            }

        }

 

I implemented these using the following utility function:

 

modifyUnitState :: (UnitState -> UnitState) -> HscEnv -> HscEnv

modifyUnitState f env = env

    { hsc_unit_env = let ue = hsc_unit_env env in ue

        { ue_units = f (ue_units ue)

        }

    }

 

With the recent changes to GHC, `modifyUnitState` doesn’t work anymore because there is no single `UnitEnv` in the `HscEnv`. I tried updating the `HomeUnitEnv` of the current unit:

 

modifyUnitState :: (UnitState -> UnitState) -> HscEnv -> HscEnv

modifyUnitState f env = env

    { hsc_unit_env = let ue = hsc_unit_env env in

            ue_updateHomeUnitEnv f' (ue_currentUnit ue) ue

    }

  where

    f' hue = let units = homeUnitEnv_units hue in hue

        { homeUnitEnv_units = f units

        }

 

but this leads to a panic:

 

  GHC version 9.5.20220613:

        Unit unknown to the internal unit environment

 

unit (cortex-prim)

pprInternalUnitMap

  main (flags: main, Just main) ->

Call stack:

    CallStack (from HasCallStack):

      callStackDoc, called at compiler/GHC/Utils/Panic.hs:182:37 in ghc-lib-0.20220613-HQTH0nHhxeOCnJy5jYkZiX:GHC.Utils.Panic

      pprPanic, called at compiler/GHC/Unit/Env.hs:450:14 in ghc-lib-0.20220613-HQTH0nHhxeOCnJy5jYkZiX:GHC.Unit.Env

      ue_findHomeUnitEnv, called at compiler/GHC/Unit/Env.hs:394:48 in ghc-lib-0.20220613-HQTH0nHhxeOCnJy5jYkZiX:GHC.Unit.Env

      ue_unitFlags, called at compiler/GHC/Driver/Env.hs:421:18 in ghc-lib-0.20220613-HQTH0nHhxeOCnJy5jYkZiX:GHC.Driver.Env

      hscSetActiveUnitId, called at compiler/GHC/Driver/Env.hs:416:34 in ghc-lib-0.20220613-HQTH0nHhxeOCnJy5jYkZiX:GHC.Driver.Env

      hscSetActiveHomeUnit, called at compiler/GHC/Driver/Make.hs:1853:15 in ghc-lib-0.20220613-HQTH0nHhxeOCnJy5jYkZiX:GHC.Driver.Make

 

 

What is the new way of registering a new unit or new module with GHC?

 

Thanks,

            Gergo


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