ghc-9.14.1: GHC/Driver/Make.hs
{-# LANGUAGE NondecreasingIndentation #-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE DerivingStrategies #-}
{-# LANGUAGE ApplicativeDo #-}
{-# LANGUAGE MultiWayIf #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE BlockArguments #-}
{-# LANGUAGE ViewPatterns #-}
-- -----------------------------------------------------------------------------
--
-- (c) The University of Glasgow, 2011
--
-- This module implements multi-module compilation, and is used
-- by --make and GHCi.
--
-- -----------------------------------------------------------------------------
module GHC.Driver.Make (
depanal, depanalE, depanalPartial,
load, loadWithCache, load', AnyGhcDiagnostic, LoadHowMuch(..), ModIfaceCache(..), noIfaceCache, newIfaceCache,
downsweep,
topSortModuleGraph,
ms_home_srcimps, ms_home_imps,
hscSourceToIsBoot,
findExtraSigImports,
implicitRequirementsShallow,
noModError, cyclicModuleErr,
SummaryNode,
IsBootInterface(..), mkNodeKey,
ModNodeKey, ModNodeKeyWithUid(..),
ModNodeMap(..), emptyModNodeMap, modNodeMapElems, modNodeMapLookup, modNodeMapInsert, modNodeMapSingleton, modNodeMapUnionWith,
-- * Re-exports from Downsweep
checkHomeUnitsClosed,
summariseModule,
summariseModuleInterface,
SummariseResult(..),
summariseFile,
instantiationNodes,
) where
import GHC.Prelude
import GHC.Platform
import GHC.Tc.Utils.Backpack
import GHC.Tc.Utils.Monad ( initIfaceCheck, concatMapM )
import GHC.Runtime.Interpreter
import qualified GHC.Linker.Loader as Linker
import GHC.Linker.Types
import GHC.Driver.Config.Diagnostic
import GHC.Driver.Pipeline
import GHC.Driver.Session
import GHC.Driver.DynFlags (ReexportedModule(..))
import GHC.Driver.Monad
import GHC.Driver.Env
import GHC.Driver.Errors
import GHC.Driver.Errors.Types
import GHC.Driver.Main
import GHC.Driver.MakeSem
import GHC.Driver.Downsweep
import GHC.Driver.MakeAction
import GHC.ByteCode.Types
import GHC.Iface.Load ( cannotFindModule, readIface )
import GHC.IfaceToCore ( typecheckIface )
import GHC.Iface.Recomp ( RecompileRequired(..), CompileReason(..) )
import GHC.Data.Bag ( listToBag )
import GHC.Data.Graph.Directed
import GHC.Data.Maybe ( expectJust )
import GHC.Utils.Exception ( throwIO, SomeAsyncException )
import GHC.Utils.Outputable
import GHC.Utils.Panic
import GHC.Utils.Misc
import GHC.Utils.Error
import GHC.Utils.Logger
import GHC.Utils.TmpFs
import GHC.Types.Basic
import GHC.Types.Error
import GHC.Types.Target
import GHC.Types.SourceFile
import GHC.Types.SourceError
import GHC.Types.SrcLoc
import GHC.Types.PkgQual
import GHC.Unit
import GHC.Unit.Env
import GHC.Unit.Finder
import GHC.Unit.Module.ModSummary
import GHC.Unit.Module.ModIface
import GHC.Unit.Module.Graph
import GHC.Unit.Home.ModInfo
import GHC.Unit.Module.ModDetails
import qualified Data.Map as Map
import qualified Data.Set as Set
import Control.Concurrent.MVar
import Control.Monad
import qualified Control.Monad.Catch as MC
import Data.IORef
import Data.Maybe
import Data.List (sortOn, groupBy, sortBy)
import qualified Data.List as List
import System.FilePath
import Control.Monad.IO.Class
import Control.Monad.Trans.Reader
import qualified Data.Map.Strict as M
import GHC.Types.TypeEnv
import Control.Monad.Trans.State.Lazy
import Control.Monad.Trans.Class
import GHC.Driver.Env.KnotVars
import Control.Monad.Trans.Maybe
import GHC.Runtime.Loader
import GHC.Utils.Constants
import GHC.Iface.Errors.Types
import Data.Function
import qualified GHC.Data.Maybe as M
import GHC.Data.Graph.Directed.Reachability
import qualified GHC.Unit.Home.Graph as HUG
import GHC.Unit.Home.PackageTable
-- -----------------------------------------------------------------------------
-- Loading the program
-- | Perform a dependency analysis starting from the current targets
-- and update the session with the new module graph.
--
-- Dependency analysis entails parsing the @import@ directives and may
-- therefore require running certain preprocessors.
--
-- Note that each 'ModSummary' in the module graph caches its 'DynFlags'.
-- These 'DynFlags' are determined by the /current/ session 'DynFlags' and the
-- @OPTIONS@ and @LANGUAGE@ pragmas of the parsed module. Thus if you want
-- changes to the 'DynFlags' to take effect you need to call this function
-- again.
-- In case of errors, just throw them.
--
depanal :: GhcMonad m =>
[ModuleName] -- ^ excluded modules
-> Bool -- ^ allow duplicate roots
-> m ModuleGraph
depanal excluded_mods allow_dup_roots = do
(errs, mod_graph) <- depanalE mkUnknownDiagnostic Nothing excluded_mods allow_dup_roots
if isEmptyMessages errs
then pure mod_graph
else throwErrors (fmap GhcDriverMessage errs)
-- | Perform dependency analysis like in 'depanal'.
-- In case of errors, the errors and an empty module graph are returned.
depanalE :: GhcMonad m => -- New for #17459
(GhcMessage -> AnyGhcDiagnostic)
-> Maybe Messager
-> [ModuleName] -- ^ excluded modules
-> Bool -- ^ allow duplicate roots
-> m (DriverMessages, ModuleGraph)
depanalE diag_wrapper msg excluded_mods allow_dup_roots = do
hsc_env <- getSession
(errs, mod_graph) <- depanalPartial diag_wrapper msg excluded_mods allow_dup_roots
if isEmptyMessages errs
then do
hsc_env <- getSession
let one_unit_messages get_mod_errs k hue = do
errs <- get_mod_errs
unknown_module_err <- warnUnknownModules (hscSetActiveUnitId k hsc_env) (homeUnitEnv_dflags hue) mod_graph
let unused_home_mod_err = warnMissingHomeModules (homeUnitEnv_dflags hue) (hsc_targets hsc_env) mod_graph
unused_pkg_err = warnUnusedPackages (homeUnitEnv_units hue) (homeUnitEnv_dflags hue) mod_graph
return $ errs `unionMessages` unused_home_mod_err
`unionMessages` unused_pkg_err
`unionMessages` unknown_module_err
all_errs <- liftIO $ HUG.unitEnv_foldWithKey one_unit_messages (return emptyMessages) (hsc_HUG hsc_env)
logDiagnostics (GhcDriverMessage <$> all_errs)
setSession (setModuleGraph mod_graph hsc_env)
pure (emptyMessages, mod_graph)
else do
-- We don't have a complete module dependency graph,
-- The graph may be disconnected and is unusable.
setSession (setModuleGraph emptyMG hsc_env)
pure (errs, emptyMG)
-- | Perform dependency analysis like 'depanal' but return a partial module
-- graph even in the face of problems with some modules.
--
-- Modules which have parse errors in the module header, failing
-- preprocessors or other issues preventing them from being summarised will
-- simply be absent from the returned module graph.
--
-- Unlike 'depanal' this function will not update 'hsc_mod_graph' with the
-- new module graph.
depanalPartial
:: GhcMonad m
=> (GhcMessage -> AnyGhcDiagnostic)
-> Maybe Messager
-> [ModuleName] -- ^ excluded modules
-> Bool -- ^ allow duplicate roots
-> m (DriverMessages, ModuleGraph)
-- ^ possibly empty 'Bag' of errors and a module graph.
depanalPartial diag_wrapper msg excluded_mods allow_dup_roots = do
hsc_env <- getSession
let
targets = hsc_targets hsc_env
old_graph = hsc_mod_graph hsc_env
logger = hsc_logger hsc_env
withTiming logger (text "Chasing dependencies") (const ()) $ do
liftIO $ debugTraceMsg logger 2 (hcat [
text "Chasing modules from: ",
hcat (punctuate comma (map pprTarget targets))])
-- Home package modules may have been moved or deleted, and new
-- source files may have appeared in the home package that shadow
-- external package modules, so we have to discard the existing
-- cached finder data.
liftIO $ flushFinderCaches (hsc_FC hsc_env) (hsc_unit_env hsc_env)
(errs, mod_graph) <- liftIO $ downsweep
hsc_env diag_wrapper msg (mgModSummaries old_graph)
excluded_mods allow_dup_roots
return (unionManyMessages errs, mod_graph)
-- Note [Missing home modules]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- Sometimes we don't want GHC to process modules that weren't specified as
-- explicit targets. For example, cabal may want to enable this warning
-- when building a library, so that GHC warns the user about modules listed
-- neither in `exposed-modules` nor in `other-modules`.
--
-- Here "home module" means a module that doesn't come from another package.
--
-- For example, if GHC is invoked with modules "A" and "B" as targets,
-- but "A" imports some other module "C", then GHC will issue a warning
-- about module "C" not being listed in the command line.
--
-- The warning in enabled by `-Wmissing-home-modules`. See #13129
warnMissingHomeModules :: DynFlags -> [Target] -> ModuleGraph -> DriverMessages
warnMissingHomeModules dflags targets mod_graph =
if null missing
then emptyMessages
else warn
where
diag_opts = initDiagOpts dflags
-- We need to be careful to handle the case where (possibly
-- path-qualified) filenames (aka 'TargetFile') rather than module
-- names are being passed on the GHC command-line.
--
-- For instance, `ghc --make src-exe/Main.hs` and
-- `ghc --make -isrc-exe Main` are supposed to be equivalent.
-- Note also that we can't always infer the associated module name
-- directly from the filename argument. See #13727.
is_known_module mod =
is_module_target mod
||
maybe False is_file_target (ml_hs_file (ms_location mod))
is_module_target mod = (moduleName (ms_mod mod), ms_unitid mod) `Set.member` mod_targets
is_file_target file = Set.member (withoutExt file) file_targets
file_targets = Set.fromList (mapMaybe file_target targets)
file_target Target {targetId} =
case targetId of
TargetModule _ -> Nothing
TargetFile file _ ->
Just (withoutExt (augmentByWorkingDirectory dflags file))
mod_targets = Set.fromList (mod_target <$> targets)
mod_target Target {targetUnitId, targetId} =
case targetId of
TargetModule name -> (name, targetUnitId)
TargetFile file _ -> (mkModuleName (withoutExt file), targetUnitId)
withoutExt = fst . splitExtension
missing = map (moduleName . ms_mod) $
filter (not . is_known_module) $
(filter (\ms -> ms_unitid ms == homeUnitId_ dflags)
(mgModSummaries mod_graph))
warn = singleMessage $ mkPlainMsgEnvelope diag_opts noSrcSpan
$ DriverMissingHomeModules (homeUnitId_ dflags) missing (checkBuildingCabalPackage dflags)
-- Check that any modules we want to reexport or hide are actually in the package.
warnUnknownModules :: HscEnv -> DynFlags -> ModuleGraph -> IO DriverMessages
warnUnknownModules hsc_env dflags mod_graph = do
reexported_warns <- filterM check_reexport reexported_mods
return $ final_msgs hidden_warns reexported_warns
where
diag_opts = initDiagOpts dflags
unit_mods = Set.fromList (map ms_mod_name
(filter (\ms -> ms_unitid ms == homeUnitId_ dflags)
(mgModSummaries mod_graph)))
reexported_mods = reexportedModules dflags
hidden_mods = hiddenModules dflags
hidden_warns = hidden_mods `Set.difference` unit_mods
lookupModule mn = findImportedModule hsc_env mn NoPkgQual
check_reexport mn = do
fr <- lookupModule (reexportFrom mn)
case fr of
Found _ m -> return (moduleUnitId m == homeUnitId_ dflags)
_ -> return True
warn diagnostic = singleMessage $ mkPlainMsgEnvelope diag_opts noSrcSpan
$ diagnostic
final_msgs hidden_warns reexported_warns
=
unionManyMessages $
[warn (DriverUnknownHiddenModules (homeUnitId_ dflags) (Set.toList hidden_warns)) | not (Set.null hidden_warns)]
++ [warn (DriverUnknownReexportedModules (homeUnitId_ dflags) reexported_warns) | not (null reexported_warns)]
-- | Describes which modules of the module graph need to be loaded.
data LoadHowMuch
= LoadAllTargets
-- ^ Load all targets and its dependencies.
| LoadUpTo [HomeUnitModule]
-- ^ Load only the given modules and its dependencies.
-- If empty, we load none of the targets
| LoadDependenciesOf HomeUnitModule
-- ^ Load only the dependencies of the given module, but not the module
-- itself.
{-
Note [Caching HomeModInfo]
~~~~~~~~~~~~~~~~~~~~~~~~~~
API clients who call `load` like to cache the HomeModInfo in memory between
calls to this function. In the old days, this cache was a simple MVar which stored
a HomePackageTable. This was insufficient, as the interface files for boot modules
were not recorded in the cache. In the less old days, the cache was returned at the
end of load, and supplied at the start of load, however, this was not sufficient
because it didn't account for the possibility of exceptions such as SIGINT (#20780).
So now, in the current day, we have this ModIfaceCache abstraction which
can incrementally be updated during the process of upsweep. This allows us
to store interface files for boot modules in an exception-safe way.
When the final version of an interface file is completed then it is placed into
the cache. The contents of the cache is retrieved, and the cache cleared, by iface_clearCache.
Note that because we only store the ModIface and Linkable in the ModIfaceCache,
hydration and rehydration is totally irrelevant, and we just store the CachedIface as
soon as it is completed.
-}
-- Abstract interface to a cache of HomeModInfo
-- See Note [Caching HomeModInfo]
data ModIfaceCache = ModIfaceCache { iface_clearCache :: IO [CachedIface]
, iface_addToCache :: CachedIface -> IO () }
addHmiToCache :: ModIfaceCache -> HomeModInfo -> IO ()
addHmiToCache c (HomeModInfo i _ l) = iface_addToCache c (CachedIface i l)
data CachedIface = CachedIface { cached_modiface :: !ModIface
, cached_linkable :: !HomeModLinkable }
instance Outputable CachedIface where
ppr (CachedIface mi ln) = hsep [text "CachedIface", ppr (miKey mi), ppr ln]
noIfaceCache :: Maybe ModIfaceCache
noIfaceCache = Nothing
newIfaceCache :: IO ModIfaceCache
newIfaceCache = do
ioref <- newIORef []
return $
ModIfaceCache
{ iface_clearCache = atomicModifyIORef' ioref (\c -> ([], c))
, iface_addToCache = \hmi -> atomicModifyIORef' ioref (\c -> (hmi:c, ()))
}
-- | Try to load the program. See 'LoadHowMuch' for the different modes.
--
-- This function implements the core of GHC's @--make@ mode. It preprocesses,
-- compiles and loads the specified modules, avoiding re-compilation wherever
-- possible. Depending on the backend (see 'DynFlags.backend' field) compiling
-- and loading may result in files being created on disk.
--
-- Calls the 'defaultWarnErrLogger' after each compiling each module, whether
-- successful or not.
--
-- If errors are encountered during dependency analysis, the module `depanalE`
-- returns together with the errors an empty ModuleGraph.
-- After processing this empty ModuleGraph, the errors of depanalE are thrown.
-- All other errors are reported using the 'defaultWarnErrLogger'.
load :: GhcMonad f => LoadHowMuch -> f SuccessFlag
load how_much = loadWithCache noIfaceCache mkUnknownDiagnostic how_much
mkBatchMsg :: HscEnv -> Messager
mkBatchMsg hsc_env =
if length (hsc_all_home_unit_ids hsc_env) > 1
-- This also displays what unit each module is from.
then batchMultiMsg
else batchMsg
loadWithCache :: GhcMonad m => Maybe ModIfaceCache -- ^ Instructions about how to cache interfaces as we create them.
-> (GhcMessage -> AnyGhcDiagnostic) -- ^ How to wrap error messages before they are displayed to a user.
-- If you are using the GHC API you can use this to override how messages
-- created during 'loadWithCache' are displayed to the user.
-> LoadHowMuch -- ^ How much `loadWithCache` should load
-> m SuccessFlag
loadWithCache cache diag_wrapper how_much = do
msg <- mkBatchMsg <$> getSession
(errs, mod_graph) <- depanalE diag_wrapper (Just msg) [] False -- #17459
success <- load' cache how_much diag_wrapper (Just msg) mod_graph
if isEmptyMessages errs
then pure success
else throwErrors (fmap GhcDriverMessage errs)
-- Note [Unused packages]
-- ~~~~~~~~~~~~~~~~~~~~~~
-- Cabal passes `-package-id` flag for each direct dependency. But GHC
-- loads them lazily, so when compilation is done, we have a list of all
-- actually loaded packages. All the packages, specified on command line,
-- but never loaded, are probably unused dependencies.
warnUnusedPackages :: UnitState -> DynFlags -> ModuleGraph -> DriverMessages
warnUnusedPackages us dflags mod_graph =
let diag_opts = initDiagOpts dflags
home_mod_sum = filter (\ms -> homeUnitId_ dflags == ms_unitid ms) (mgModSummaries mod_graph)
-- Only need non-source imports here because SOURCE imports are always HPT
loadedPackages = concat $
mapMaybe (\(_st, fs, mn) -> lookupModulePackage us (unLoc mn) fs)
$ concatMap ms_imps home_mod_sum
used_args = Set.fromList (map unitId loadedPackages)
resolve (u,mflag) = do
-- The units which we depend on via the command line explicitly
flag <- mflag
-- Which we can find the UnitInfo for (should be all of them)
ui <- lookupUnit us u
-- Which are not explicitly used
guard (Set.notMember (unitId ui) used_args)
return (unitId ui, unitPackageName ui, unitPackageVersion ui, flag)
unusedArgs = sortOn (\(u,_,_,_) -> u) $ mapMaybe resolve (explicitUnits us)
warn = singleMessage $ mkPlainMsgEnvelope diag_opts noSrcSpan (DriverUnusedPackages unusedArgs)
in if null unusedArgs
then emptyMessages
else warn
-- | A ModuleGraphNode which also has a hs-boot file, and the list of nodes on any
-- path from module to its boot file.
data ModuleGraphNodeWithBootFile
= ModuleGraphNodeWithBootFile
ModuleGraphNode
-- ^ The module itself (not the hs-boot module)
[NodeKey]
-- ^ The modules in between the module and its hs-boot file,
-- not including the hs-boot file itself.
instance Outputable ModuleGraphNodeWithBootFile where
ppr (ModuleGraphNodeWithBootFile mgn deps) = text "ModeGraphNodeWithBootFile: " <+> ppr mgn $$ ppr deps
-- | A 'BuildPlan' is the result of attempting to linearise a single strongly-connected
-- component of the module graph.
data BuildPlan
-- | A simple, single module all alone (which *might* have an hs-boot file, if it isn't part of a cycle)
= SingleModule ModuleGraphNode
-- | A resolved cycle, linearised by hs-boot files
| ResolvedCycle [Either ModuleGraphNode ModuleGraphNodeWithBootFile]
-- | An actual cycle, which wasn't resolved by hs-boot files
| UnresolvedCycle [ModuleGraphNode]
instance Outputable BuildPlan where
ppr (SingleModule mgn) = text "SingleModule" <> parens (ppr mgn)
ppr (ResolvedCycle mgn) = text "ResolvedCycle:" <+> ppr mgn
ppr (UnresolvedCycle mgn) = text "UnresolvedCycle:" <+> ppr mgn
-- Just used for an assertion
countMods :: BuildPlan -> Int
countMods (SingleModule _) = 1
countMods (ResolvedCycle ns) = length ns
countMods (UnresolvedCycle ns) = length ns
-- See Note [Upsweep] for a high-level description.
createBuildPlan :: ModuleGraph -> Maybe [HomeUnitModule] -> [BuildPlan]
createBuildPlan mod_graph maybe_top_mod =
let -- Step 1: Compute SCCs without .hi-boot files, to find the cycles
cycle_mod_graph = topSortModuleGraph True mod_graph maybe_top_mod
acyclic_mod_graph = topSortModuleGraph False mod_graph maybe_top_mod
-- Step 2: Reanalyse loops, with relevant boot modules, to solve the cycles.
build_plan :: [BuildPlan]
build_plan
-- Fast path, if there are no boot modules just do a normal toposort
| isEmptyModuleEnv boot_modules = collapseAcyclic acyclic_mod_graph
| otherwise = toBuildPlan cycle_mod_graph []
toBuildPlan :: [SCC ModuleGraphNode] -> [ModuleGraphNode] -> [BuildPlan]
toBuildPlan [] mgn = collapseAcyclic (topSortWithBoot mgn)
toBuildPlan ((AcyclicSCC node):sccs) mgn = toBuildPlan sccs (node:mgn)
-- Interesting case
toBuildPlan ((CyclicSCC nodes):sccs) mgn =
let acyclic = collapseAcyclic (topSortWithBoot mgn)
-- Now perform another toposort but just with these nodes and relevant hs-boot files.
-- The result should be acyclic, if it's not, then there's an unresolved cycle in the graph.
mresolved_cycle = collapseSCC (topSortWithBoot nodes)
in acyclic ++ [either UnresolvedCycle ResolvedCycle mresolved_cycle] ++ toBuildPlan sccs []
-- Compute the intermediate modules between a file and its hs-boot file.
-- See Step 2a in Note [Upsweep]
boot_path mn uid =
Set.toList $
-- Don't include the boot module itself
Set.filter ((/= NodeKey_Module (key IsBoot)) . mkNodeKey) $
-- Keep intermediate dependencies: as per Step 2a in Note [Upsweep], these are
-- the transitive dependencies of the non-boot file which transitively depend
-- on the boot file.
Set.filter (\(mkNodeKey -> nk) ->
nodeKeyUnitId nk == uid -- Cheap test
&& mgQuery mod_graph nk (NodeKey_Module (key IsBoot))) $
Set.fromList $
expectJust (mgReachable mod_graph (NodeKey_Module (key NotBoot)))
where
key ib = ModNodeKeyWithUid (GWIB mn ib) uid
-- An environment mapping a module to its hs-boot file and all nodes on the path between the two, if one exists
boot_modules = mkModuleEnv
[ (mn, (m, boot_path (moduleName mn) (moduleUnitId mn)))
| m@(ModuleNode _ ms) <- mgModSummaries' mod_graph
, let mn = moduleNodeInfoModule ms
, isBootModuleNodeInfo ms == IsBoot]
select_boot_modules :: [ModuleGraphNode] -> [ModuleGraphNode]
select_boot_modules = mapMaybe (fmap fst . get_boot_module)
get_boot_module :: ModuleGraphNode -> Maybe (ModuleGraphNode, [ModuleGraphNode])
get_boot_module (ModuleNode _ ms)
| NotBoot <- isBootModuleNodeInfo ms
= lookupModuleEnv boot_modules (moduleNodeInfoModule ms)
get_boot_module _ = Nothing
-- Any cycles should be resolved now
collapseSCC :: [SCC ModuleGraphNode] -> Either [ModuleGraphNode] [(Either ModuleGraphNode ModuleGraphNodeWithBootFile)]
-- Must be at least two nodes, as we were in a cycle
collapseSCC [AcyclicSCC node1, AcyclicSCC node2] = Right [toNodeWithBoot node1, toNodeWithBoot node2]
collapseSCC (AcyclicSCC node : nodes) = either (Left . (node :)) (Right . (toNodeWithBoot node :)) (collapseSCC nodes)
-- Cyclic
collapseSCC nodes = Left (flattenSCCs nodes)
toNodeWithBoot :: ModuleGraphNode -> Either ModuleGraphNode ModuleGraphNodeWithBootFile
toNodeWithBoot mn =
case get_boot_module mn of
-- The node doesn't have a boot file
Nothing -> Left mn
-- The node does have a boot file
Just path -> Right (ModuleGraphNodeWithBootFile mn (map mkNodeKey (snd path)))
-- The toposort and accumulation of acyclic modules is solely to pick-up
-- hs-boot files which are **not** part of cycles.
collapseAcyclic :: [SCC ModuleGraphNode] -> [BuildPlan]
collapseAcyclic (AcyclicSCC node : nodes) = SingleModule node : collapseAcyclic nodes
collapseAcyclic (CyclicSCC cy_nodes : nodes) = (UnresolvedCycle cy_nodes) : collapseAcyclic nodes
collapseAcyclic [] = []
topSortWithBoot nodes = topSortModules False (select_boot_modules nodes ++ nodes) Nothing
in
-- We need to use 'acyclic_mod_graph', since if 'maybe_top_mod' is 'Just', then the resulting module
-- graph is pruned, reducing the number of 'build_plan' elements.
-- We don't use the size of 'cycle_mod_graph', as it removes @.hi-boot@ modules. These are added
-- later in the processing.
assertPpr (sum (map countMods build_plan) == lengthMGWithSCC acyclic_mod_graph)
(vcat [text "Build plan missing nodes:", (text "PLAN:" <+> ppr (sum (map countMods build_plan))), (text "GRAPH:" <+> ppr (lengthMGWithSCC acyclic_mod_graph))])
build_plan
where
lengthMGWithSCC :: [SCC a] -> Int
lengthMGWithSCC = List.foldl' (\acc scc -> length scc + acc) 0
-- | Generalized version of 'load' which also supports a custom
-- 'Messager' (for reporting progress) and 'ModuleGraph' (generally
-- produced by calling 'depanal'.
load' :: GhcMonad m => Maybe ModIfaceCache -> LoadHowMuch -> (GhcMessage -> AnyGhcDiagnostic) -> Maybe Messager -> ModuleGraph -> m SuccessFlag
load' mhmi_cache how_much diag_wrapper mHscMessage mod_graph = do
-- In normal usage plugins are initialised already by ghc/Main.hs this is protective
-- for any client who might interact with GHC via load'.
-- See Note [Timing of plugin initialization]
initializeSessionPlugins
modifySession (setModuleGraph mod_graph)
guessOutputFile
hsc_env <- getSession
let dflags = hsc_dflags hsc_env
let logger = hsc_logger hsc_env
let interp = hscInterp hsc_env
-- The "bad" boot modules are the ones for which we have
-- B.hs-boot in the module graph, but no B.hs
-- The downsweep should have ensured this does not happen
-- (see msDeps)
let all_home_mods =
Set.fromList [ Module (ms_unitid s) (ms_mod_name s)
| s <- mgModSummaries mod_graph, isBootSummary s == NotBoot]
-- TODO: Figure out what the correct form of this assert is. It's violated
-- when you have HsBootMerge nodes in the graph: then you'll have hs-boot
-- files without corresponding hs files.
-- bad_boot_mods = [s | s <- mod_graph, isBootSummary s,
-- not (ms_mod_name s `elem` all_home_mods)]
-- assert (null bad_boot_mods ) return ()
-- check that the module given in HowMuch actually exists, otherwise
-- topSortModuleGraph will bomb later.
let checkHowMuch (LoadUpTo ms) = checkMods ms
checkHowMuch (LoadDependenciesOf m) = checkMods [m]
checkHowMuch _ = id
checkMods ms and_then =
case List.partition (`Set.member` all_home_mods) ms of
(_, []) -> and_then
(_, not_found_mods) -> do
let
mkModuleNotFoundError m =
mkPlainErrorMsgEnvelope noSrcSpan
$ GhcDriverMessage
$ DriverModuleNotFound (moduleUnit m) (moduleName m)
throwErrors $ mkMessages $ listToBag [mkModuleNotFoundError not_found | not_found <- not_found_mods]
checkHowMuch how_much $ do
-- mg2_with_srcimps drops the hi-boot nodes, returning a
-- graph with cycles. It is just used for warning about unnecessary source imports.
let mg2_with_srcimps :: [SCC ModuleGraphNode]
mg2_with_srcimps = topSortModuleGraph True mod_graph Nothing
-- If we can determine that any of the {-# SOURCE #-} imports
-- are definitely unnecessary, then emit a warning.
warnUnnecessarySourceImports (filterToposortToModules mg2_with_srcimps)
let maybe_top_mods = case how_much of
LoadUpTo m -> Just m
LoadDependenciesOf m -> Just [m]
_ -> Nothing
build_plan = createBuildPlan mod_graph maybe_top_mods
cache <- liftIO $ maybe (return []) iface_clearCache mhmi_cache
let
-- prune the HPT so everything is not retained when doing an
-- upsweep.
!pruned_cache = pruneCache cache
[ms | (ModuleNodeCompile ms) <- (flattenSCCs (filterToposortToModules mg2_with_srcimps))]
-- before we unload anything, make sure we don't leave an old
-- interactive context around pointing to dead bindings. Also,
-- write an empty HPT to allow the old HPT to be GC'd.
let pruneHomeUnitEnv hme = do
emptyHPT <- liftIO emptyHomePackageTable
pure $! hme{ homeUnitEnv_hpt = emptyHPT }
hug' <- traverse pruneHomeUnitEnv (ue_home_unit_graph $ hsc_unit_env hsc_env)
let ue' = (hsc_unit_env hsc_env){ ue_home_unit_graph = hug' }
setSession $ discardIC hsc_env{hsc_unit_env = ue' }
hsc_env <- getSession
-- Unload everything
liftIO $ unload interp hsc_env
liftIO $ debugTraceMsg logger 2 (hang (text "Ready for upsweep")
2 (ppr build_plan))
worker_limit <- liftIO $ mkWorkerLimit dflags
(upsweep_ok, new_deps) <- withDeferredDiagnostics $ do
hsc_env <- getSession
liftIO $ upsweep worker_limit hsc_env mhmi_cache diag_wrapper mHscMessage (toCache pruned_cache) build_plan
-- At this point, all the HPT variables will be populated, but we don't want
-- to leak the contents of a failed session.
liftIO $ restrictDepsHscEnv new_deps hsc_env
case upsweep_ok of
Failed -> loadFinish upsweep_ok
Succeeded -> do
liftIO $ debugTraceMsg logger 2 (text "Upsweep completely successful.")
loadFinish upsweep_ok
-- | Finish up after a load.
loadFinish :: GhcMonad m => SuccessFlag -> m SuccessFlag
-- Empty the interactive context and set the module context to the topmost
-- newly loaded module, or the Prelude if none were loaded.
loadFinish all_ok
= do modifySession discardIC
return all_ok
-- | If there is no -o option, guess the name of target executable
-- by using top-level source file name as a base.
guessOutputFile :: GhcMonad m => m ()
guessOutputFile = modifySession $ \env ->
-- Force mod_graph to avoid leaking env
let !mod_graph = hsc_mod_graph env
new_home_graph =
flip fmap (hsc_HUG env) $ \hue ->
let dflags = homeUnitEnv_dflags hue
platform = targetPlatform dflags
mainModuleSrcPath :: Maybe String
mainModuleSrcPath = do
ms <- mgLookupModule mod_graph (mainModIs hue)
ml_hs_file (moduleNodeInfoLocation ms)
name = fmap dropExtension mainModuleSrcPath
-- MP: This exception is quite sensitive to being forced, if you
-- force it here then the error message is different because it gets
-- caught by a different error handler than the test (T9930fail) expects.
-- Putting an exception into DynFlags is probably not a great design but
-- I'll write this comment rather than more eagerly force the exception.
name_exe = do
-- we must add the .exe extension unconditionally here, otherwise
-- when name has an extension of its own, the .exe extension will
-- not be added by GHC.Driver.Pipeline.exeFileName. See #2248
!name' <- case platformArchOS platform of
ArchOS _ OSMinGW32 -> fmap (<.> "exe") name
ArchOS ArchWasm32 _ -> fmap (<.> "wasm") name
_ -> name
mainModuleSrcPath' <- mainModuleSrcPath
-- #9930: don't clobber input files (unless they ask for it)
if name' == mainModuleSrcPath'
then throwGhcException . UsageError $
"default output name would overwrite the input file; " ++
"must specify -o explicitly"
else Just name'
in
case outputFile_ dflags of
Just _ -> hue
Nothing -> hue {homeUnitEnv_dflags = dflags { outputFile_ = name_exe } }
in env { hsc_unit_env = (hsc_unit_env env) { ue_home_unit_graph = new_home_graph } }
-- -----------------------------------------------------------------------------
--
-- | Prune the HomePackageTable
--
-- Before doing an upsweep, we can throw away:
--
-- - all ModDetails, all linked code
-- - all unlinked code that is out of date with respect to
-- the source file
--
-- This is VERY IMPORTANT otherwise we'll end up requiring 2x the
-- space at the end of the upsweep, because the topmost ModDetails of the
-- old HPT holds on to the entire type environment from the previous
-- compilation.
-- Note [GHC Heap Invariants]
pruneCache :: [CachedIface]
-> [ModSummary]
-> [HomeModInfo]
pruneCache hpt summ
= strictMap prune hpt
where prune (CachedIface { cached_modiface = iface
, cached_linkable = linkable
}) = HomeModInfo iface emptyModDetails linkable'
where
modl = miKey iface
linkable'
| Just ms <- M.lookup modl ms_map
, mi_src_hash iface == Just (ms_hs_hash ms)
= linkable
| otherwise
= emptyHomeModInfoLinkable
-- Using UFM Module is safe for determinism because the map is just used for a transient lookup. The cache should be unique and a key clash is an error.
ms_map = M.fromListWith
(\ms1 ms2 -> assertPpr False (text "prune_cache" $$ (ppr ms1 <+> ppr ms2))
ms2)
[(msKey ms, ms) | ms <- summ]
-- ---------------------------------------------------------------------------
--
-- | Unloading
unload :: Interp -> HscEnv -> IO ()
unload interp hsc_env
= case ghcLink (hsc_dflags hsc_env) of
LinkInMemory -> Linker.unload interp hsc_env []
_other -> return ()
{- Parallel Upsweep
The parallel upsweep attempts to concurrently compile the modules in the
compilation graph using multiple Haskell threads.
The Algorithm
* The list of `MakeAction`s are created by `interpretBuildPlan`. A `MakeAction` is
a pair of an `IO a` action and a `MVar a`, where to place the result.
The list is sorted topologically, so can be executed in order without fear of
blocking.
* runPipelines takes this list and eventually passes it to runLoop which executes
each action and places the result into the right MVar.
* The amount of parallelism is controlled by a semaphore. This is just used around the
module compilation step, so that only the right number of modules are compiled at
the same time which reduces overall memory usage and allocations.
* Each proper node has a LogQueue, which dictates where to send it's output.
* The LogQueue is placed into the LogQueueQueue when the action starts and a worker
thread processes the LogQueueQueue printing logs for each module in a stable order.
* The result variable for an action producing `a` is of type `Maybe a`, therefore
it is still filled on a failure. If a module fails to compile, the
failure is propagated through the whole module graph and any modules which didn't
depend on the failure can still be compiled. This behaviour also makes the code
quite a bit cleaner.
-}
{-
Note [--make mode]
~~~~~~~~~~~~~~~~~
There are two main parts to `--make` mode.
1. `downsweep`: Starts from the top of the module graph and computes dependencies.
2. `upsweep`: Starts from the bottom of the module graph and compiles modules.
The result of the downsweep is a 'ModuleGraph', which is then passed to 'upsweep' which
computers how to build this ModuleGraph.
Note [Upsweep]
~~~~~~~~~~~~~~
Upsweep takes a 'ModuleGraph' as input, computes a build plan and then executes
the plan in order to compile the project.
The first step is computing the build plan from a 'ModuleGraph'.
The output of this step is a `[BuildPlan]`, which is a topologically sorted plan for
how to build all the modules.
```
data BuildPlan = SingleModule ModuleGraphNode -- A simple, single module all alone but *might* have an hs-boot file which isn't part of a cycle
| ResolvedCycle [Either ModuleGraphNode ModuleGraphNodeWithBoot] -- A resolved cycle, linearised by hs-boot files
| UnresolvedCycle [ModuleGraphNode] -- An actual cycle, which wasn't resolved by hs-boot files
```
The plan is computed in two steps:
Step 1: Topologically sort the module graph without hs-boot files. This returns a [SCC ModuleGraphNode] which contains
cycles.
Step 2: For each cycle, topologically sort the modules in the cycle *with* the relevant hs-boot files. This should
result in an acyclic build plan if the hs-boot files are sufficient to resolve the cycle.
Step 2a: For each module in the cycle, if the module has a boot file then compute the
modules on the path between it and the hs-boot file.
These are the intermediate modules which:
(1) are (transitive) dependencies of the non-boot module, and
(2) have the boot module as a (transitive) dependency.
In particular, all such intermediate modules must appear in the same unit as
the module under consideration, as module cycles cannot cross unit boundaries.
This information is stored in ModuleGraphNodeWithBoot.
The `[BuildPlan]` is then interpreted by the `interpretBuildPlan` function.
* SingleModule nodes are compiled normally by either the upsweep_inst or upsweep_mod functions.
* ResolvedCycles need to compiled "together" so that modules outside the cycle are presented
with a consistent knot-tied version of modules at the end.
- When the ModuleGraphNodeWithBoot nodes are compiled then suitable rehydration
is performed both before and after the module in question is compiled.
See Note [Hydrating Modules] for more information.
* UnresolvedCycles are indicative of a proper cycle, unresolved by hs-boot files
and are reported as an error to the user.
The main trickiness of `interpretBuildPlan` is deciding which version of a dependency
is visible from each module. For modules which are not in a cycle, there is just
one version of a module, so that is always used. For modules in a cycle, there are two versions of
'HomeModInfo'.
1. Internal to loop: The version created whilst compiling the loop by upsweep_mod.
2. External to loop: The knot-tied version created by typecheckLoop.
Whilst compiling a module inside the loop, we need to use the (1). For a module which
is outside of the loop which depends on something from in the loop, the (2) version
is used.
As the plan is interpreted, which version of a HomeModInfo is visible is updated
by updating a map held in a state monad. So after a loop has finished being compiled,
the visible module is the one created by typecheckLoop and the internal version is not
used again.
This plan also ensures the most important invariant to do with module loops:
> If you depend on anything within a module loop, before you can use the dependency,
the whole loop has to finish compiling.
The end result of `interpretBuildPlan` is a `[MakeAction]`, which are pairs
of `IO a` actions and a `MVar (Maybe a)`, somewhere to put the result of running
the action. This list is topologically sorted, so can be run in order to compute
the whole graph.
As well as this `interpretBuildPlan` also outputs an `IO [Maybe (Maybe HomeModInfo)]` which
can be queried at the end to get the result of all modules at the end, with their proper
visibility. For example, if any module in a loop fails then all modules in that loop will
report as failed because the visible node at the end will be the result of checking
these modules together.
-}
-- | Simple wrapper around MVar which allows a functor instance.
data ResultVar b = forall a . ResultVar (a -> b) (MVar (Maybe a))
deriving instance Functor ResultVar
mkResultVar :: MVar (Maybe a) -> ResultVar a
mkResultVar = ResultVar id
-- | Block until the result is ready.
waitResult :: ResultVar a -> MaybeT IO a
waitResult (ResultVar f var) = MaybeT (fmap f <$> readMVar var)
data BuildResult = BuildResult { _resultOrigin :: ResultOrigin
, resultVar :: ResultVar (Maybe HomeModInfo)
}
-- The origin of this result var, useful for debugging
data ResultOrigin = NoLoop | Loop ResultLoopOrigin deriving (Show)
data ResultLoopOrigin = Initialise | Rehydrated | Finalised deriving (Show)
mkBuildResult :: ResultOrigin -> ResultVar (Maybe HomeModInfo) -> BuildResult
mkBuildResult = BuildResult
data BuildLoopState = BuildLoopState { buildDep :: M.Map NodeKey BuildResult
-- The current way to build a specific TNodeKey, without cycles this just points to
-- the appropriate result of compiling a module but with
-- cycles there can be additional indirection and can point to the result of typechecking a loop
, nNODE :: Int
}
nodeId :: BuildM Int
nodeId = do
n <- gets nNODE
modify (\m -> m { nNODE = n + 1 })
return n
setModulePipeline :: NodeKey -> BuildResult -> BuildM ()
setModulePipeline mgn build_result = do
modify (\m -> m { buildDep = M.insert mgn build_result (buildDep m) })
type BuildMap = M.Map NodeKey BuildResult
getBuildMap :: BuildM BuildMap
getBuildMap = gets buildDep
getDependencies :: [NodeKey] -> BuildMap -> [BuildResult]
getDependencies direct_deps build_map =
strictMap (expectJust . flip M.lookup build_map) direct_deps
type BuildM a = StateT BuildLoopState IO a
-- | Given the build plan, creates a graph which indicates where each NodeKey should
-- get its direct dependencies from. This might not be the corresponding build action
-- if the module participates in a loop. This step also labels each node with a number for the output.
-- See Note [Upsweep] for a high-level description.
interpretBuildPlan :: HomeUnitGraph
-> Maybe ModIfaceCache
-> M.Map ModNodeKeyWithUid HomeModInfo
-> [BuildPlan]
-> IO ( Maybe [ModuleGraphNode] -- Is there an unresolved cycle
, [MakeAction] -- Actions we need to run in order to build everything
, IO [Maybe (Maybe HomeModInfo)]) -- An action to query to get all the built modules at the end.
interpretBuildPlan hug mhmi_cache old_hpt plan = do
((mcycle, plans), build_map) <- runStateT (buildLoop plan) (BuildLoopState M.empty 1)
let wait = collect_results (buildDep build_map)
return (mcycle, plans, wait)
where
collect_results build_map =
sequence (map (\br -> collect_result (resultVar br)) (M.elems build_map))
where
collect_result res_var = runMaybeT (waitResult res_var)
-- Just used for an assertion
count_mods :: BuildPlan -> Int
count_mods (SingleModule m) = count_m m
count_mods (ResolvedCycle ns) = length ns
count_mods (UnresolvedCycle ns) = length ns
count_m (UnitNode {}) = 0
count_m _ = 1
n_mods = sum (map count_mods plan)
buildLoop :: [BuildPlan]
-> BuildM (Maybe [ModuleGraphNode], [MakeAction])
-- Build the abstract pipeline which we can execute
-- Building finished
buildLoop [] = return (Nothing, [])
buildLoop (plan:plans) =
case plan of
-- If there was no cycle, then typecheckLoop is not necessary
SingleModule m -> do
one_plan <- buildSingleModule Nothing NoLoop m
(cycle, all_plans) <- buildLoop plans
return (cycle, one_plan : all_plans)
-- For a resolved cycle, depend on everything in the loop, then update
-- the cache to point to this node rather than directly to the module build
-- nodes
ResolvedCycle ms -> do
pipes <- buildModuleLoop ms
(cycle, graph) <- buildLoop plans
return (cycle, pipes ++ graph)
-- Can't continue past this point as the cycle is unresolved.
UnresolvedCycle ns -> return (Just ns, [])
buildSingleModule :: Maybe [NodeKey] -- Modules we need to rehydrate before compiling this module
-> ResultOrigin
-> ModuleGraphNode -- The node we are compiling
-> BuildM MakeAction
buildSingleModule rehydrate_nodes origin mod = do
!build_map <- getBuildMap
-- 1. Get the direct dependencies of this module
let direct_deps = mgNodeDependencies False mod
-- It's really important to force build_deps, or the whole buildMap is retained,
-- which would retain all the result variables, preventing us from collecting them
-- after they are no longer used.
!build_deps = getDependencies direct_deps build_map
!build_action <-
case mod of
InstantiationNode uid iu -> do
mod_idx <- nodeId
return $ withCurrentUnit (mgNodeUnitId mod) $ do
!_ <- wait_deps build_deps
executeInstantiationNode mod_idx n_mods hug uid iu
return Nothing
ModuleNode _build_deps ms -> do
let !old_hmi = M.lookup (mnKey ms) old_hpt
rehydrate_mods = mapMaybe nodeKeyModName <$> rehydrate_nodes
mod_idx <- nodeId
return $ withCurrentUnit (mgNodeUnitId mod) $ do
!_ <- wait_deps build_deps
hmi <- executeCompileNode mod_idx n_mods old_hmi hug rehydrate_mods ms
-- Write the HMI to an external cache (if one exists)
-- See Note [Caching HomeModInfo]
liftIO $ forM mhmi_cache $ \hmi_cache -> addHmiToCache hmi_cache hmi
-- Make sure the result is written to the HPT var
liftIO $ HUG.addHomeModInfoToHug hmi hug
return (Just hmi)
LinkNode _nks uid -> do
mod_idx <- nodeId
return $ withCurrentUnit (mgNodeUnitId mod) $ do
!_ <- wait_deps build_deps
executeLinkNode hug (mod_idx, n_mods) uid direct_deps
return Nothing
UnitNode {} -> return $ return Nothing
res_var <- liftIO newEmptyMVar
let result_var = mkResultVar res_var
setModulePipeline (mkNodeKey mod) (mkBuildResult origin result_var)
return $! (MakeAction build_action res_var)
buildOneLoopyModule :: ModuleGraphNodeWithBootFile -> BuildM [MakeAction]
buildOneLoopyModule (ModuleGraphNodeWithBootFile mn deps) = do
ma <- buildSingleModule (Just deps) (Loop Initialise) mn
-- Rehydration (1) from Note [Hydrating Modules], "Loops with multiple boot files"
rehydrate_action <- rehydrateAction Rehydrated ((GWIB (mkNodeKey mn) IsBoot) : (map (\d -> GWIB d NotBoot) deps))
return $ [ma, rehydrate_action]
buildModuleLoop :: [Either ModuleGraphNode ModuleGraphNodeWithBootFile] -> BuildM [MakeAction]
buildModuleLoop ms = do
build_modules <- concatMapM (either (fmap (:[]) <$> buildSingleModule Nothing (Loop Initialise)) buildOneLoopyModule) ms
let extract (Left mn) = GWIB (mkNodeKey mn) NotBoot
extract (Right (ModuleGraphNodeWithBootFile mn _)) = GWIB (mkNodeKey mn) IsBoot
let loop_mods = map extract ms
-- Rehydration (2) from Note [Hydrating Modules], "Loops with multiple boot files"
-- Fixes the space leak described in that note.
rehydrate_action <- rehydrateAction Finalised loop_mods
return $ build_modules ++ [rehydrate_action]
-- An action which rehydrates the given keys
rehydrateAction :: ResultLoopOrigin -> [GenWithIsBoot NodeKey] -> BuildM MakeAction
rehydrateAction origin deps = do
!build_map <- getBuildMap
res_var <- liftIO newEmptyMVar
let loop_unit :: UnitId
!loop_unit = nodeKeyUnitId (gwib_mod (head deps))
!build_deps = getDependencies (map gwib_mod deps) build_map
let loop_action = withCurrentUnit loop_unit $ do
!_ <- wait_deps build_deps
hsc_env <- asks hsc_env
let mns :: [ModuleName]
mns = mapMaybe (nodeKeyModName . gwib_mod) deps
hmis' <- liftIO $ rehydrateAfter hsc_env mns
checkRehydrationInvariant hmis' deps
-- Add hydrated interfaces to global variable
liftIO $ mapM_ (\hmi -> HUG.addHomeModInfoToHug hmi hug) hmis'
return hmis'
let fanout i = Just . (!! i) <$> mkResultVar res_var
-- From outside the module loop, anyone must wait for the loop to finish and then
-- use the result of the rehydrated iface. This makes sure that things not in the
-- module loop will see the updated interfaces for all the identifiers in the loop.
boot_key :: NodeKey -> NodeKey
boot_key (NodeKey_Module m) = NodeKey_Module (m { mnkModuleName = (mnkModuleName m) { gwib_isBoot = IsBoot } } )
boot_key k = pprPanic "boot_key" (ppr k)
update_module_pipeline (m, i) =
case gwib_isBoot m of
NotBoot -> setModulePipeline (gwib_mod m) (mkBuildResult (Loop origin) (fanout i))
IsBoot -> do
setModulePipeline (gwib_mod m) (mkBuildResult (Loop origin) (fanout i))
-- SPECIAL: Anything outside the loop needs to see A rather than A.hs-boot
setModulePipeline (boot_key (gwib_mod m)) (mkBuildResult (Loop origin) (fanout i))
let deps_i = zip deps [0..]
mapM update_module_pipeline deps_i
return $ MakeAction loop_action res_var
-- Checks that the interfaces returned from hydration match-up with the names of the
-- modules which were fed into the function.
checkRehydrationInvariant hmis deps =
let hmi_names = map (moduleName . mi_module . hm_iface) hmis
start = mapMaybe (nodeKeyModName . gwib_mod) deps
in massertPpr (hmi_names == start) $ (ppr hmi_names $$ ppr start)
withCurrentUnit :: UnitId -> RunMakeM a -> RunMakeM a
withCurrentUnit uid = do
local (\env -> env { hsc_env = hscSetActiveUnitId uid (hsc_env env)})
upsweep
:: WorkerLimit -- ^ The number of workers we wish to run in parallel
-> HscEnv -- ^ The base HscEnv, which is augmented for each module
-> Maybe ModIfaceCache -- ^ A cache to incrementally write final interface files to
-> (GhcMessage -> AnyGhcDiagnostic)
-> Maybe Messager
-> M.Map ModNodeKeyWithUid HomeModInfo
-> [BuildPlan]
-> IO (SuccessFlag, [HomeModInfo])
upsweep n_jobs hsc_env hmi_cache diag_wrapper mHscMessage old_hpt build_plan = do
(cycle, pipelines, collect_result) <- interpretBuildPlan (hsc_HUG hsc_env) hmi_cache old_hpt build_plan
runPipelines n_jobs hsc_env diag_wrapper mHscMessage pipelines
res <- collect_result
let completed = [m | Just (Just m) <- res]
-- Handle any cycle in the original compilation graph and return the result
-- of the upsweep.
case cycle of
Just mss -> do
throwOneError $ cyclicModuleErr mss
Nothing -> do
let success_flag = successIf (all isJust res)
return (success_flag, completed)
toCache :: [HomeModInfo] -> M.Map (ModNodeKeyWithUid) HomeModInfo
toCache hmis = M.fromList ([(miKey $ hm_iface hmi, hmi) | hmi <- hmis])
upsweep_inst :: HscEnv
-> Maybe Messager
-> Int -- index of module
-> Int -- total number of modules
-> UnitId
-> InstantiatedUnit
-> IO ()
upsweep_inst hsc_env mHscMessage mod_index nmods uid iuid = do
case mHscMessage of
Just hscMessage -> hscMessage hsc_env (mod_index, nmods) (NeedsRecompile MustCompile) (InstantiationNode uid iuid)
Nothing -> return ()
runHsc hsc_env $ ioMsgMaybe $ hoistTcRnMessage $ tcRnCheckUnit hsc_env $ VirtUnit iuid
pure ()
-- | Compile a single module. Always produce a Linkable for it if
-- successful. If no compilation happened, return the old Linkable.
upsweep_mod :: HscEnv
-> Maybe Messager
-> Maybe HomeModInfo
-> ModSummary
-> Int -- index of module
-> Int -- total number of modules
-> IO HomeModInfo
upsweep_mod hsc_env mHscMessage old_hmi summary mod_index nmods = do
hmi <- compileOne' mHscMessage hsc_env summary
mod_index nmods (hm_iface <$> old_hmi) (maybe emptyHomeModInfoLinkable hm_linkable old_hmi)
-- MP: This is a bit janky, because before you add the entries you have to extend the HPT with the module
-- you just compiled. Another option, would be delay adding anything until after upsweep has finished, but I
-- am unsure if this is sound (wrt running TH splices for example).
-- This function only does anything if the linkable produced is a BCO, which
-- used to only happen with the bytecode backend, but with
-- @-fprefer-byte-code@, @HomeModInfo@ has bytecode even when generating
-- object code, see #25230.
hscInsertHPT hmi hsc_env
addSptEntries (hsc_env)
(homeModInfoByteCode hmi)
return hmi
-- | Add the entries from a BCO linkable to the SPT table, see
-- See Note [Grand plan for static forms] in GHC.Iface.Tidy.StaticPtrTable.
addSptEntries :: HscEnv -> Maybe Linkable -> IO ()
addSptEntries hsc_env mlinkable =
hscAddSptEntries hsc_env
[ spt
| linkable <- maybeToList mlinkable
, bco <- linkableBCOs linkable
, spt <- bc_spt_entries bco
]
-- Note [When source is considered modified]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- A number of functions in GHC.Driver accept a SourceModified argument, which
-- is part of how GHC determines whether recompilation may be avoided (see the
-- definition of the SourceModified data type for details).
--
-- Determining whether or not a source file is considered modified depends not
-- only on the source file itself, but also on the output files which compiling
-- that module would produce. This is done because GHC supports a number of
-- flags which control which output files should be produced, e.g. -fno-code
-- -fwrite-interface and -fwrite-ide-file; we must check not only whether the
-- source file has been modified since the last compile, but also whether the
-- source file has been modified since the last compile which produced all of
-- the output files which have been requested.
--
-- Specifically, a source file is considered unmodified if it is up-to-date
-- relative to all of the output files which have been requested. Whether or
-- not an output file is up-to-date depends on what kind of file it is:
--
-- * iface (.hi) files are considered up-to-date if (and only if) their
-- mi_src_hash field matches the hash of the source file,
--
-- * all other output files (.o, .dyn_o, .hie, etc) are considered up-to-date
-- if (and only if) their modification times on the filesystem are greater
-- than or equal to the modification time of the corresponding .hi file.
--
-- Why do we use '>=' rather than '>' for output files other than the .hi file?
-- If the filesystem has poor resolution for timestamps (e.g. FAT32 has a
-- resolution of 2 seconds), we may often find that the .hi and .o files have
-- the same modification time. Using >= is slightly unsafe, but it matches
-- make's behaviour.
--
-- This strategy allows us to do the minimum work necessary in order to ensure
-- that all the files the user cares about are up-to-date; e.g. we should not
-- worry about .o files if the user has indicated that they are not interested
-- in them via -fno-code. See also #9243.
--
-- Note that recompilation avoidance is dependent on .hi files being produced,
-- which does not happen if -fno-write-interface -fno-code is passed. That is,
-- passing -fno-write-interface -fno-code means that you cannot benefit from
-- recompilation avoidance. See also Note [-fno-code mode].
--
-- The correctness of this strategy depends on an assumption that whenever we
-- are producing multiple output files, the .hi file is always written first.
-- If this assumption is violated, we risk recompiling unnecessarily by
-- incorrectly regarding non-.hi files as outdated.
--
-- ---------------------------------------------------------------------------
--
-- | Topological sort of the module graph
topSortModuleGraph
:: Bool
-- ^ Drop hi-boot nodes? (see below)
-> ModuleGraph
-> Maybe [HomeUnitModule]
-- ^ Root module name. If @Nothing@, use the full graph.
-> [SCC ModuleGraphNode]
-- ^ Calculate SCCs of the module graph, possibly dropping the hi-boot nodes
-- The resulting list of strongly-connected-components is in topologically
-- sorted order, starting with the module(s) at the bottom of the
-- dependency graph (ie compile them first) and ending with the ones at
-- the top.
--
-- Drop hi-boot nodes (first boolean arg)?
--
-- - @False@: treat the hi-boot summaries as nodes of the graph,
-- so the graph must be acyclic
--
-- - @True@: eliminate the hi-boot nodes, and instead pretend
-- the a source-import of Foo is an import of Foo
-- The resulting graph has no hi-boot nodes, but can be cyclic
topSortModuleGraph drop_hs_boot_nodes module_graph mb_root_mod =
topSortModules drop_hs_boot_nodes
(sortBy (cmpModuleGraphNodes `on` mkNodeKey) $ mgModSummaries' module_graph)
mb_root_mod
where
-- In order to get the "right" ordering
-- Module nodes must be in reverse lexigraphic order.
-- All modules nodes must appear before package nodes.
--
-- MP: This is just the ordering which the tests needed in Jan 2025, it does
-- not arise from nature.
--
-- Given the current implementation of scc, the result is in
-- The order is sensitive to the internal implementation in Data.Graph,
-- if it changes in future then this ordering will need to be modified.
--
-- The SCC algorithm firstly transposes the input graph and then
-- performs dfs on the vertices in the order which they are originally given.
-- Therefore, if `ExternalUnit` nodes are first, the order returned will
-- be determined by the order the dependencies are stored in the transposed graph.
moduleGraphNodeRank :: NodeKey -> Int
moduleGraphNodeRank k =
case k of
NodeKey_Unit {} -> 0
NodeKey_Module {} -> 1
NodeKey_Link {} -> 2
NodeKey_ExternalUnit {} -> 3
cmpModuleGraphNodes k1 k2 = compare (moduleGraphNodeRank k1) (moduleGraphNodeRank k2)
`mappend` compare k2 k1
topSortModules :: Bool -> [ModuleGraphNode] -> Maybe [HomeUnitModule] -> [SCC ModuleGraphNode]
topSortModules drop_hs_boot_nodes summaries mb_root_mod
= map (fmap summaryNodeSummary) $ stronglyConnCompG initial_graph
where
(graph, lookup_node) =
moduleGraphNodes drop_hs_boot_nodes summaries
initial_graph = case mb_root_mod of
Nothing -> graph
Just mods ->
-- restrict the graph to just those modules reachable from
-- the specified module. We do this by building a graph with
-- the full set of nodes, and determining the reachable set from
-- the specified node.
let
findNodeForModule (Module uid root_mod)
| Just node <- lookup_node $ NodeKey_Module $ ModNodeKeyWithUid (GWIB root_mod NotBoot) uid
, graph `hasVertexG` node
= seq node node
| otherwise
= throwGhcException (ProgramError "module does not exist")
roots = fmap findNodeForModule mods
in graphFromEdgedVerticesUniq (seq roots (roots ++ allReachableMany (graphReachability graph) roots))
newtype ModNodeMap a = ModNodeMap { unModNodeMap :: Map.Map ModNodeKey a }
deriving (Functor, Traversable, Foldable)
emptyModNodeMap :: ModNodeMap a
emptyModNodeMap = ModNodeMap Map.empty
modNodeMapInsert :: ModNodeKey -> a -> ModNodeMap a -> ModNodeMap a
modNodeMapInsert k v (ModNodeMap m) = ModNodeMap (Map.insert k v m)
modNodeMapElems :: ModNodeMap a -> [a]
modNodeMapElems (ModNodeMap m) = Map.elems m
modNodeMapLookup :: ModNodeKey -> ModNodeMap a -> Maybe a
modNodeMapLookup k (ModNodeMap m) = Map.lookup k m
modNodeMapSingleton :: ModNodeKey -> a -> ModNodeMap a
modNodeMapSingleton k v = ModNodeMap (M.singleton k v)
modNodeMapUnionWith :: (a -> a -> a) -> ModNodeMap a -> ModNodeMap a -> ModNodeMap a
modNodeMapUnionWith f (ModNodeMap m) (ModNodeMap n) = ModNodeMap (M.unionWith f m n)
-- | If there are {-# SOURCE #-} imports between strongly connected
-- components in the topological sort, then those imports can
-- definitely be replaced by ordinary non-SOURCE imports: if SOURCE
-- were necessary, then the edge would be part of a cycle.
warnUnnecessarySourceImports :: GhcMonad m => [SCC ModuleNodeInfo] -> m ()
warnUnnecessarySourceImports sccs = do
diag_opts <- initDiagOpts <$> getDynFlags
when (diag_wopt Opt_WarnUnusedImports diag_opts) $ do
let check ms =
let mods_in_this_cycle = map moduleNodeInfoModuleName ms in
[ warn i | (ModuleNodeCompile m) <- ms, i <- ms_home_srcimps m,
unLoc i `notElem` mods_in_this_cycle ]
warn :: Located ModuleName -> MsgEnvelope GhcMessage
warn (L loc mod) = GhcDriverMessage <$> mkPlainMsgEnvelope diag_opts
loc (DriverUnnecessarySourceImports mod)
logDiagnostics (mkMessages $ listToBag (concatMap (check . flattenSCC) sccs))
-----------------------------------------------------------------------------
-- Error messages
-----------------------------------------------------------------------------
-- Defer and group warning, error and fatal messages so they will not get lost
-- in the regular output.
withDeferredDiagnostics :: GhcMonad m => m a -> m a
withDeferredDiagnostics f = do
dflags <- getDynFlags
if not $ gopt Opt_DeferDiagnostics dflags
then f
else do
warnings <- liftIO $ newIORef []
errors <- liftIO $ newIORef []
fatals <- liftIO $ newIORef []
logger <- getLogger
let deferDiagnostics _dflags !msgClass !srcSpan !msg = do
let action = logMsg logger msgClass srcSpan msg
case msgClass of
MCDiagnostic SevWarning _reason _code
-> atomicModifyIORef' warnings $ \(!i) -> (action: i, ())
MCDiagnostic SevError _reason _code
-> atomicModifyIORef' errors $ \(!i) -> (action: i, ())
MCFatal
-> atomicModifyIORef' fatals $ \(!i) -> (action: i, ())
_ -> action
printDeferredDiagnostics = liftIO $
forM_ [warnings, errors, fatals] $ \ref -> do
-- This IORef can leak when the dflags leaks, so let us always
-- reset the content. The lazy variant is used here as we want to force
-- this error if the IORef is ever accessed again, rather than now.
-- See #20981 for an issue which discusses this general issue.
let landmine = if debugIsOn then panic "withDeferredDiagnostics: use after free" else []
actions <- atomicModifyIORef ref $ \i -> (landmine, i)
sequence_ $ reverse actions
MC.bracket
(pushLogHookM (const deferDiagnostics))
(\_ -> popLogHookM >> printDeferredDiagnostics)
(\_ -> f)
noModError :: HscEnv -> SrcSpan -> ModuleName -> FindResult -> MsgEnvelope GhcMessage
-- ToDo: we don't have a proper line number for this error
noModError hsc_env loc wanted_mod err
= mkPlainErrorMsgEnvelope loc $ GhcDriverMessage $
DriverInterfaceError $
(Can'tFindInterface (cannotFindModule hsc_env wanted_mod err) (LookingForModule wanted_mod NotBoot))
{-
noHsFileErr :: SrcSpan -> String -> DriverMessages
noHsFileErr loc path
= singleMessage $ mkPlainErrorMsgEnvelope loc (DriverFileNotFound path)
-}
cyclicModuleErr :: [ModuleGraphNode] -> MsgEnvelope GhcMessage
-- From a strongly connected component we find
-- a single cycle to report
cyclicModuleErr mss
= assert (not (null mss)) $
case findCycle graph of
Nothing -> pprPanic "Unexpected non-cycle" (ppr mss)
Just path -> mkPlainErrorMsgEnvelope src_span $
GhcDriverMessage $ DriverModuleGraphCycle path
where
src_span = maybe noSrcSpan (mkFileSrcSpan . moduleNodeInfoLocation) (mgNodeIsModule (head path))
where
graph :: [Node NodeKey ModuleGraphNode]
graph =
[ DigraphNode
{ node_payload = ms
, node_key = mkNodeKey ms
, node_dependencies = mgNodeDependencies False ms
}
| ms <- mss
]
cleanCurrentModuleTempFilesMaybe :: MonadIO m => Logger -> TmpFs -> DynFlags -> m ()
cleanCurrentModuleTempFilesMaybe logger tmpfs dflags =
if gopt Opt_KeepTmpFiles dflags
then liftIO $ keepCurrentModuleTempFiles logger tmpfs
else liftIO $ cleanCurrentModuleTempFiles logger tmpfs
-- | Thin each HPT variable to only contain keys from the given dependencies.
-- This is used at the end of upsweep to make sure that only completely successfully loaded
-- modules are visible for subsequent operations.
restrictDepsHscEnv :: [HomeModInfo] -> HscEnv -> IO ()
restrictDepsHscEnv deps hsc_env =
let deps_with_unit = map (\xs -> (fst (head xs), map snd xs)) $ groupBy ((==) `on` fst) (sortOn fst (map go deps))
hug = ue_home_unit_graph $ hsc_unit_env hsc_env
go hmi = (hmi_unit, hmi)
where
hmi_mod = mi_module (hm_iface hmi)
hmi_unit = toUnitId (moduleUnit hmi_mod)
in HUG.restrictHug deps_with_unit hug
setHUG :: HomeUnitGraph -> HscEnv -> HscEnv
setHUG deps hsc_env =
hscUpdateHUG (const $ deps) hsc_env
-- | Wrap an action to catch and handle exceptions.
wrapAction :: (GhcMessage -> AnyGhcDiagnostic) -> HscEnv -> IO a -> IO (Maybe a)
wrapAction msg_wrapper hsc_env k = do
let lcl_logger = hsc_logger hsc_env
lcl_dynflags = hsc_dflags hsc_env
print_config = initPrintConfig lcl_dynflags
logg err = printMessages lcl_logger print_config (initDiagOpts lcl_dynflags) (msg_wrapper <$> srcErrorMessages err)
-- MP: It is a bit strange how prettyPrintGhcErrors handles some errors but then we handle
-- SourceError and ThreadKilled differently directly below. TODO: Refactor to use `catches`
-- directly. MP should probably use safeTry here to not catch async exceptions but that will regress performance due to
-- internally using forkIO.
mres <- MC.try $ prettyPrintGhcErrors lcl_logger $ k
case mres of
Right res -> return $ Just res
Left exc -> do
case fromException exc of
Just (err :: SourceError)
-> logg err
Nothing -> case fromException exc of
-- ThreadKilled in particular needs to actually kill the thread.
-- So rethrow that and the other async exceptions
Just (err :: SomeAsyncException) -> throwIO err
_ -> errorMsg lcl_logger (text (show exc))
return Nothing
executeInstantiationNode :: Int
-> Int
-> HomeUnitGraph
-> UnitId
-> InstantiatedUnit
-> RunMakeM ()
executeInstantiationNode k n deps uid iu = do
env <- ask
-- Output of the logger is mediated by a central worker to
-- avoid output interleaving
msg <- asks env_messager
wrapper <- asks diag_wrapper
lift $ MaybeT $ withLoggerHsc k env $ \hsc_env ->
let lcl_hsc_env = setHUG deps hsc_env
in wrapAction wrapper lcl_hsc_env $ do
res <- upsweep_inst lcl_hsc_env msg k n uid iu
cleanCurrentModuleTempFilesMaybe (hsc_logger hsc_env) (hsc_tmpfs hsc_env) (hsc_dflags hsc_env)
return res
-- | executeCompileNode interprets how --make module should compile a ModuleNode
--
-- 1. If the ModuleNode is a ModuleNodeCompile, then we first check
-- if the interface file exists and is up to date. If it is, we return those.
-- Otherwise, we compile the module and return the new HomeModInfo.
-- 2. If the ModuleNode is a ModuleNodeFixed, then we just need to load the interface
-- and artifacts from disk.
executeCompileNode :: Int
-> Int
-> Maybe HomeModInfo
-> HomeUnitGraph
-> Maybe [ModuleName] -- List of modules we need to rehydrate before compiling
-> ModuleNodeInfo
-> RunMakeM HomeModInfo
executeCompileNode k n !old_hmi hug mrehydrate_mods mni = do
me@MakeEnv{..} <- ask
-- Rehydrate any dependencies if this module had a boot file or is a signature file.
lift $ MaybeT (withAbstractSem compile_sem $ withLoggerHsc k me $ \hsc_env -> do
hsc_env' <- liftIO $ maybeRehydrateBefore (setHUG hug hsc_env) mni fixed_mrehydrate_mods
case mni of
ModuleNodeCompile mod -> executeCompileNodeWithSource hsc_env' me mod
ModuleNodeFixed key loc -> executeCompileNodeFixed hsc_env' me key loc
)
where
fixed_mrehydrate_mods =
case moduleNodeInfoHscSource mni of
-- MP: It is probably a bit of a misimplementation in backpack that
-- compiling a signature requires an knot_var for that unit.
-- If you remove this then a lot of backpack tests fail.
Just HsigFile -> Just []
_ -> mrehydrate_mods
executeCompileNodeFixed :: HscEnv -> MakeEnv -> ModNodeKeyWithUid -> ModLocation -> IO (Maybe HomeModInfo)
executeCompileNodeFixed hsc_env MakeEnv{diag_wrapper, env_messager} mod loc =
wrapAction diag_wrapper hsc_env $ do
forM_ env_messager $ \hscMessage -> hscMessage hsc_env (k, n) UpToDate (ModuleNode [] (ModuleNodeFixed mod loc))
read_result <- readIface (hsc_hooks hsc_env) (hsc_logger hsc_env) (hsc_dflags hsc_env) (hsc_NC hsc_env) (mnkToModule mod) (ml_hi_file loc)
case read_result of
M.Failed interface_err ->
let mn = mnkModuleName mod
err = Can'tFindInterface (BadIfaceFile interface_err) (LookingForModule (gwib_mod mn) (gwib_isBoot mn))
in throwErrors $ singleMessage $ mkPlainErrorMsgEnvelope noSrcSpan (GhcDriverMessage (DriverInterfaceError err))
M.Succeeded iface -> do
details <- genModDetails hsc_env iface
mb_object <- findObjectLinkableMaybe (mi_module iface) loc
mb_bytecode <- loadIfaceByteCodeLazy hsc_env iface loc (md_types details)
let hm_linkable = HomeModLinkable mb_bytecode mb_object
return (HomeModInfo iface details hm_linkable)
executeCompileNodeWithSource :: HscEnv -> MakeEnv -> ModSummary -> IO (Maybe HomeModInfo)
executeCompileNodeWithSource hsc_env MakeEnv{diag_wrapper, env_messager} mod = do
let -- Use the cached DynFlags which includes OPTIONS_GHC pragmas
lcl_dynflags = ms_hspp_opts mod
let lcl_hsc_env =
-- Localise the hsc_env to use the cached flags
hscSetFlags lcl_dynflags $
hsc_env
-- Compile the module, locking with a semaphore to avoid too many modules
-- being compiled at the same time leading to high memory usage.
wrapAction diag_wrapper lcl_hsc_env $ do
res <- upsweep_mod lcl_hsc_env env_messager old_hmi mod k n
cleanCurrentModuleTempFilesMaybe (hsc_logger hsc_env) (hsc_tmpfs hsc_env) lcl_dynflags
return res
{- Rehydration, see Note [Rehydrating Modules] -}
rehydrate :: HscEnv -- ^ The HPT in this HscEnv needs rehydrating.
-> [HomeModInfo] -- ^ These are the modules we want to rehydrate.
-> IO [HomeModInfo]
rehydrate hsc_env hmis = do
debugTraceMsg logger 2 $ (
text "Re-hydrating loop: " <+> (ppr (map (mi_module . hm_iface) hmis)))
-- When the HPT was pure we had to tie a knot to update the ModDetails in the
-- HPT required to update those ModDetails, but since it was made an IORef we
-- just have to make sure the new ModDetails are "reset" so that the new
-- modules are looked up in HPT when it is forced. If we didn't "reset" the
-- ModDetails, modules in a loop would refer the wrong (hs-boot) definitions
-- (as explained in Note [Rehydrating Modules]).
mds <- initIfaceCheck (text "rehydrate") hsc_env $
mapM (typecheckIface . hm_iface) hmis
let new_mods = [ hmi{ hm_details = details }
| (hmi,details) <- zip hmis mds
]
return new_mods
where
logger = hsc_logger hsc_env
-- If needed, then rehydrate the necessary modules with a suitable KnotVars for the
-- module currently being compiled.
maybeRehydrateBefore :: HscEnv -> ModuleNodeInfo -> Maybe [ModuleName] -> IO HscEnv
maybeRehydrateBefore hsc_env _ Nothing = return hsc_env
maybeRehydrateBefore hsc_env mni (Just mns) = do
knot_var <- initialise_knot_var hsc_env
let hsc_env' = hsc_env { hsc_type_env_vars = knotVarsFromModuleEnv knot_var }
hmis <- mapM (fmap expectJust . lookupHpt (hsc_HPT hsc_env')) mns
hmis' <- rehydrate hsc_env' hmis
mapM_ (\hmi -> HUG.addHomeModInfoToHug hmi (hsc_HUG hsc_env')) hmis'
return hsc_env'
where
initialise_knot_var hsc_env = liftIO $
let mod_name = homeModuleInstantiation (hsc_home_unit_maybe hsc_env) (moduleNodeInfoModule mni)
in mkModuleEnv . (:[]) . (mod_name,) <$> newIORef emptyTypeEnv
rehydrateAfter :: HscEnv
-> [ModuleName]
-> IO [HomeModInfo]
rehydrateAfter hsc mns = do
let hpt = hsc_HPT hsc
hmis <- mapM (fmap expectJust . lookupHpt hpt) mns
rehydrate (hsc { hsc_type_env_vars = emptyKnotVars }) hmis
{-
Note [Hydrating Modules]
~~~~~~~~~~~~~~~~~~~~~~~~
There are at least 4 different representations of an interface file as described
by this diagram.
------------------------------
| On-disk M.hi |
------------------------------
| ^
| Read file | Write file
V |
-------------------------------
| ByteString |
-------------------------------
| ^
| Binary.get | Binary.put
V |
--------------------------------
| ModIface (an acyclic AST) |
--------------------------------
| ^
| hydrate | mkIfaceTc
V |
---------------------------------
| ModDetails (lots of cycles) |
---------------------------------
The last step, converting a ModIface into a ModDetails is known as "hydration".
Hydration happens in three different places
* When an interface file is initially loaded from disk, it has to be hydrated.
* When a module is finished compiling, we hydrate the ModIface in order to generate
the version of ModDetails which exists in memory (see Note [ModDetails and --make mode])
* When dealing with boot files and module loops (see Note [Rehydrating Modules])
Note [Rehydrating Modules]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
If a module has a boot file then it is critical to rehydrate the modules on
the path between the two (see #20561).
Suppose we have ("R" for "recursive"):
```
R.hs-boot: module R where
data T
g :: T -> T
A.hs: module A( f, T, g ) where
import {-# SOURCE #-} R
data S = MkS T
f :: T -> S = ...g...
R.hs: module R where
import A
data T = T1 | T2 S
g = ...f...
```
== Why we need to rehydrate A's ModIface before compiling R.hs
After compiling A.hs we'll have a TypeEnv in which the Id for `f` has a type
that uses the AbstractTyCon T; and a TyCon for `S` that also mentions that same
AbstractTyCon. (Abstract because it came from R.hs-boot; we know nothing about
it.)
When compiling R.hs, we build a TyCon for `T`. But that TyCon mentions `S`, and
it currently has an AbstractTyCon for `T` inside it. But we want to build a
fully cyclic structure, in which `S` refers to `T` and `T` refers to `S`.
Solution: **rehydration**. *Before compiling `R.hs`*, rehydrate all the
ModIfaces below it that depend on R.hs-boot. To rehydrate a ModIface, call
`typecheckIface` to convert it to a ModDetails. It's just a de-serialisation
step, no type inference, just lookups.
Now `S` will be bound to a thunk that, when forced, will "see" the final binding
for `T`; see [Tying the knot](https://gitlab.haskell.org/ghc/ghc/-/wikis/commentary/compiler/tying-the-knot).
But note that this must be done *before* compiling R.hs.
== Why we need to rehydrate A's ModIface after compiling R.hs
When compiling R.hs, the knot-tying stuff above will ensure that `f`'s unfolding
mentions the `LocalId` for `g`. But when we finish R, we carefully ensure that
all those `LocalIds` are turned into completed `GlobalIds`, replete with
unfoldings etc. Alas, that will not apply to the occurrences of `g` in `f`'s
unfolding. And if we leave matters like that, they will stay that way, and *all*
subsequent modules that import A will see a crippled unfolding for `f`.
Solution: rehydrate both R and A's ModIface together, right after completing R.hs.
~~ Which modules to rehydrate
We only need rehydrate modules that are
* Below R.hs
* Above R.hs-boot
There might be many unrelated modules (in the home package) that don't need to be
rehydrated.
== Loops with multiple boot files
It is possible for a module graph to have a loop (SCC, when ignoring boot files)
which requires multiple boot files to break. In this case, we must perform
several hydration steps:
1. The hydration steps described above, which are necessary for correctness.
2. An extra hydration step at the end of compiling the entire SCC, in order to
remove space leaks, as we explain below.
Consider the following example:
┌─────┐ ┌─────┐
│ A │ │ B │
└──┬──┘ └──┬──┘
│ │
┌───▼───────────▼───┐
│ C │
└───┬───────────┬───┘
│ │
┌────▼───┐ ┌───▼────┐
│ A-boot │ │ B-boot │
└────────┘ └────────┘
A, B and C live together in a SCC. Suppose that we compile the modules in the
order:
A-boot, B-boot, C, A, B.
When we come to compile A, we will perform the necessary hydration steps,
because A has a boot file. This means that C will be hydrated relative to A,
and the ModDetails for A will reference C/A. Then, when B is compiled,
C will be rehydrated again, and so B will reference C/A,B. At this point,
its interface will be hydrated relative to both A and B.
This causes a space leak: there are now two different copies of C's ModDetails,
kept alive by modules A and B. This is especially problematic if C is large.
The way to avoid this space leak is to rehydrate an entire SCC together at the
end of compilation, so that all the ModDetails point to interfaces for .hs files.
In this example, when we hydrate A, B and C together, then both A and B will refer to
C/A,B.
See #21900 for some more discussion.
== Modules "above" the loop
This dark corner is the subject of #14092.
Suppose we add to our example
```
X.hs module X where
import A
data XT = MkX T
fx = ...g...
```
If in `--make` we compile R.hs-boot, then A.hs, then X.hs, we'll get a `ModDetails` for `X` that has an AbstractTyCon for `T` in the argument type of `MkX`. So:
* Either we should delay compiling X until after R has been compiled. (This is what we do)
* Or we should rehydrate X after compiling R -- because it transitively depends on R.hs-boot.
Ticket #20200 has exposed some issues to do with the knot-tying logic in GHC.Make, in `--make` mode.
#20200 has lots of issues, many of them now fixed;
this particular issue starts [here](https://gitlab.haskell.org/ghc/ghc/-/issues/20200#note_385758).
The wiki page [Tying the knot](https://gitlab.haskell.org/ghc/ghc/-/wikis/commentary/compiler/tying-the-knot) is helpful.
Also closely related are
* #14092
* #14103
-}
executeLinkNode :: HomeUnitGraph -> (Int, Int) -> UnitId -> [NodeKey] -> RunMakeM ()
executeLinkNode hug kn uid deps = do
withCurrentUnit uid $ do
MakeEnv{..} <- ask
let dflags = hsc_dflags hsc_env
let hsc_env' = setHUG hug hsc_env
msg' = (\messager -> \recomp -> messager hsc_env kn recomp (LinkNode deps uid)) <$> env_messager
linkresult <- liftIO $ withAbstractSem compile_sem $ do
link (ghcLink dflags)
(hsc_logger hsc_env')
(hsc_tmpfs hsc_env')
(hsc_FC hsc_env')
(hsc_hooks hsc_env')
dflags
(hsc_unit_env hsc_env')
True -- We already decided to link
msg'
(hsc_HPT hsc_env')
case linkresult of
Failed -> fail "Link Failed"
Succeeded -> return ()
-- | Wait for dependencies to finish, and then return their results.
wait_deps :: [BuildResult] -> RunMakeM [HomeModInfo]
wait_deps [] = return []
wait_deps (x:xs) = do
res <- lift $ waitResult (resultVar x)
hmis <- wait_deps xs
case res of
Nothing -> return hmis
Just hmi -> return (hmi:hmis)
{- Note [GHC Heap Invariants]
~~~~~~~~~~~~~~~~~~~~~~~~~~
This note is a general place to explain some of the heap invariants which should
hold for a program compiled with --make mode. These invariants are all things
which can be checked easily using ghc-debug.
1. No HomeModInfo are reachable via the EPS.
Why? Interfaces are lazily loaded into the EPS and the lazy thunk retains
a reference to the entire HscEnv, if we are not careful the HscEnv will
contain the HomePackageTable at the time the interface was loaded and
it will never be released.
Where? dontLeakTheHUG in GHC.Iface.Load
2. No KnotVars are live at the end of upsweep (#20491)
Why? KnotVars contains an old stale reference to the TypeEnv for modules
which participate in a loop. At the end of a loop all the KnotVars references
should be removed by the call to typecheckLoop.
Where? typecheckLoop in GHC.Driver.Make.
3. Immediately after a reload, no ModDetails are live.
Why? During the upsweep all old ModDetails are replaced with a new ModDetails
generated from a ModIface. If we don't clear the ModDetails before the
reload takes place then memory usage during the reload is twice as much
as it should be as we retain a copy of the ModDetails for too long.
Where? pruneCache in GHC.Driver.Make
4. No TcGblEnv or TcLclEnv are live after typechecking is completed.
Why? By the time we get to simplification all the data structures from typechecking
should be eliminated.
Where? No one place in the compiler. These leaks can be introduced by not suitable
forcing functions which take a TcLclEnv as an argument.
5. At the end of a successful upsweep, the number of live ModDetails equals the
number of non-boot Modules.
Why? Each module has a HomeModInfo which contains a ModDetails from that module.
-}