    {-# LANGUAGE CPP #-}

    -------------------------------------------------------------------------------
    --
    -- | Dynamic flags
    --
    -- Most flags are dynamic flags, which means they can change from compilation
    -- to compilation using @OPTIONS_GHC@ pragmas, and in a multi-session GHC each
    -- session can be using different dynamic flags. Dynamic flags can also be set
    -- at the prompt in GHCi.
    --
    -- (c) The University of Glasgow 2005
    --
    -------------------------------------------------------------------------------

    {-# OPTIONS_GHC -fno-cse #-}
    -- -fno-cse is needed for GLOBAL_VAR's to behave properly

    module DynFlags (
            -- * Dynamic flags and associated configuration types
            DumpFlag(..),
            GeneralFlag(..),
            WarningFlag(..),
            ExtensionFlag(..),
            Language(..),
            PlatformConstants(..),
            FatalMessager, LogAction, FlushOut(..), FlushErr(..),
            ProfAuto(..),
            glasgowExtsFlags,
            dopt, dopt_set, dopt_unset,
            gopt, gopt_set, gopt_unset,
            wopt, wopt_set, wopt_unset,
            xopt, xopt_set, xopt_unset,
            lang_set,
            useUnicodeSyntax,
            whenGeneratingDynamicToo, ifGeneratingDynamicToo,
            whenCannotGenerateDynamicToo,
            dynamicTooMkDynamicDynFlags,
            DynFlags(..),
            FlagSpec(..),
            HasDynFlags(..), ContainsDynFlags(..),
            RtsOptsEnabled(..),
            HscTarget(..), isObjectTarget, defaultObjectTarget,
            targetRetainsAllBindings,
            GhcMode(..), isOneShot,
            GhcLink(..), isNoLink,
            PackageFlag(..), PackageArg(..), ModRenaming(..),
            PkgConfRef(..),
            Option(..), showOpt,
            DynLibLoader(..),
            fFlags, fWarningFlags, fLangFlags, xFlags,
            dynFlagDependencies,
            tablesNextToCode, mkTablesNextToCode,
            SigOf(..), getSigOf,
            checkOptLevel,

            Way(..), mkBuildTag, wayRTSOnly, addWay', updateWays,
            wayGeneralFlags, wayUnsetGeneralFlags,

            -- ** Safe Haskell
            SafeHaskellMode(..),
            safeHaskellOn, safeImportsOn, safeLanguageOn, safeInferOn,
            packageTrustOn,
            safeDirectImpsReq, safeImplicitImpsReq,
            unsafeFlags, unsafeFlagsForInfer,

            -- ** System tool settings and locations
            Settings(..),
            targetPlatform, programName, projectVersion,
            ghcUsagePath, ghciUsagePath, topDir, tmpDir, rawSettings,
            versionedAppDir,
            extraGccViaCFlags, systemPackageConfig,
            pgm_L, pgm_P, pgm_F, pgm_c, pgm_s, pgm_a, pgm_l, pgm_dll, pgm_T,
            pgm_sysman, pgm_windres, pgm_libtool, pgm_lo, pgm_lc,
            opt_L, opt_P, opt_F, opt_c, opt_a, opt_l,
            opt_windres, opt_lo, opt_lc,

            -- ** Manipulating DynFlags
            defaultDynFlags,                -- Settings -> DynFlags
            defaultWays,
            interpWays,
            initDynFlags,                   -- DynFlags -> IO DynFlags
            defaultFatalMessager,
            defaultLogAction,
            defaultLogActionHPrintDoc,
            defaultLogActionHPutStrDoc,
            defaultFlushOut,
            defaultFlushErr,

            getOpts,                        -- DynFlags -> (DynFlags -> [a]) -> [a]
            getVerbFlags,
            updOptLevel,
            setTmpDir,
            setPackageKey,
            interpretPackageEnv,

            -- ** Parsing DynFlags
            parseDynamicFlagsCmdLine,
            parseDynamicFilePragma,
            parseDynamicFlagsFull,

            -- ** Available DynFlags
            allFlags,
            flagsAll,
            flagsDynamic,
            flagsPackage,
            flagsForCompletion,

            supportedLanguagesAndExtensions,
            languageExtensions,

            -- ** DynFlags C compiler options
            picCCOpts, picPOpts,

            -- * Configuration of the stg-to-stg passes
            StgToDo(..),
            getStgToDo,

            -- * Compiler configuration suitable for display to the user
            compilerInfo,

    #ifdef GHCI
            rtsIsProfiled,
    #endif
            dynamicGhc,

    #include "../includes/dist-derivedconstants/header/GHCConstantsHaskellExports.hs"
            bLOCK_SIZE_W,
            wORD_SIZE_IN_BITS,
            tAG_MASK,
            mAX_PTR_TAG,
            tARGET_MIN_INT, tARGET_MAX_INT, tARGET_MAX_WORD,

            unsafeGlobalDynFlags, setUnsafeGlobalDynFlags,

            -- * SSE and AVX
            isSseEnabled,
            isSse2Enabled,
            isSse4_2Enabled,
            isAvxEnabled,
            isAvx2Enabled,
            isAvx512cdEnabled,
            isAvx512erEnabled,
            isAvx512fEnabled,
            isAvx512pfEnabled,

            -- * Linker/compiler information
            LinkerInfo(..),
            CompilerInfo(..),
      ) where

    #include "HsVersions.h"

    import Platform
    import PlatformConstants
    import Module
    import PackageConfig
    import {-# SOURCE #-} Hooks
    import {-# SOURCE #-} PrelNames ( mAIN )
    import {-# SOURCE #-} Packages (PackageState)
    import DriverPhases     ( Phase(..), phaseInputExt )
    import Config
    import CmdLineParser
    import Constants
    import Panic
    import Util
    import Maybes
    import MonadUtils
    import qualified Pretty
    import SrcLoc
    import FastString
    import Outputable
    #ifdef GHCI
    import Foreign.C        ( CInt(..) )
    import System.IO.Unsafe ( unsafeDupablePerformIO )
    #endif
    import {-# SOURCE #-} ErrUtils ( Severity(..), MsgDoc, mkLocMessage )

    import System.IO.Unsafe ( unsafePerformIO )
    import Data.IORef
    import Control.Arrow ((&&&))
    import Control.Monad
    import Control.Exception (throwIO)

    import Data.Bits
    import Data.Char
    import Data.Int
    import Data.List
    import Data.Map (Map)
    import qualified Data.Map as Map
    import Data.Set (Set)
    import qualified Data.Set as Set
    import Data.Word
    import System.FilePath
    import System.Directory
    import System.Environment (getEnv)
    import System.IO
    import System.IO.Error
    import Text.ParserCombinators.ReadP hiding (char)
    import Text.ParserCombinators.ReadP as R

    import Data.IntSet (IntSet)
    import qualified Data.IntSet as IntSet

    import GHC.Foreign (withCString, peekCString)

    -- Note [Updating flag description in the User's Guide]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- If you modify anything in this file please make sure that your changes are
    -- described in the User's Guide. Usually at least two sections need to be
    -- updated:
    --
    --  * Flag Reference section in docs/users-guide/flags.xml lists all available
    --    flags together with a short description
    --
    --  * Flag description in docs/users_guide/using.xml provides a detailed
    --    explanation of flags' usage.

    -- Note [Supporting CLI completion]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- The command line interface completion (in for example bash) is an easy way
    -- for the developer to learn what flags are available from GHC.
    -- GHC helps by separating which flags are available when compiling with GHC,
    -- and which flags are available when using GHCi.
    -- A flag is assumed to either work in both these modes, or only in one of them.
    -- When adding or changing a flag, please consider for which mode the flag will
    -- have effect, and annotate it accordingly. For Flags use defFlag, defGhcFlag,
    -- defGhciFlag, and for FlagSpec use flagSpec or flagGhciSpec.

    -- -----------------------------------------------------------------------------
    -- DynFlags

    data DumpFlag
    -- See Note [Updating flag description in the User's Guide]

       -- debugging flags
       = Opt_D_dump_cmm
       | Opt_D_dump_cmm_raw
       -- All of the cmm subflags (there are a lot!)  Automatically
       -- enabled if you run -ddump-cmm
       | Opt_D_dump_cmm_cfg
       | Opt_D_dump_cmm_cbe
       | Opt_D_dump_cmm_proc
       | Opt_D_dump_cmm_sink
       | Opt_D_dump_cmm_sp
       | Opt_D_dump_cmm_procmap
       | Opt_D_dump_cmm_split
       | Opt_D_dump_cmm_info
       | Opt_D_dump_cmm_cps
       -- end cmm subflags
       | Opt_D_dump_asm
       | Opt_D_dump_asm_native
       | Opt_D_dump_asm_liveness
       | Opt_D_dump_asm_regalloc
       | Opt_D_dump_asm_regalloc_stages
       | Opt_D_dump_asm_conflicts
       | Opt_D_dump_asm_stats
       | Opt_D_dump_asm_expanded
       | Opt_D_dump_llvm
       | Opt_D_dump_core_stats
       | Opt_D_dump_deriv
       | Opt_D_dump_ds
       | Opt_D_dump_foreign
       | Opt_D_dump_inlinings
       | Opt_D_dump_rule_firings
       | Opt_D_dump_rule_rewrites
       | Opt_D_dump_simpl_trace
       | Opt_D_dump_occur_anal
       | Opt_D_dump_parsed
       | Opt_D_dump_rn
       | Opt_D_dump_simpl
       | Opt_D_dump_simpl_iterations
       | Opt_D_dump_spec
       | Opt_D_dump_prep
       | Opt_D_dump_stg
       | Opt_D_dump_call_arity
       | Opt_D_dump_stranal
       | Opt_D_dump_strsigs
       | Opt_D_dump_tc
       | Opt_D_dump_types
       | Opt_D_dump_rules
       | Opt_D_dump_cse
       | Opt_D_dump_worker_wrapper
       | Opt_D_dump_rn_trace
       | Opt_D_dump_rn_stats
       | Opt_D_dump_opt_cmm
       | Opt_D_dump_simpl_stats
       | Opt_D_dump_cs_trace -- Constraint solver in type checker
       | Opt_D_dump_tc_trace
       | Opt_D_dump_if_trace
       | Opt_D_dump_vt_trace
       | Opt_D_dump_splices
       | Opt_D_th_dec_file
       | Opt_D_dump_BCOs
       | Opt_D_dump_vect
       | Opt_D_dump_ticked
       | Opt_D_dump_rtti
       | Opt_D_source_stats
       | Opt_D_verbose_stg2stg
       | Opt_D_dump_hi
       | Opt_D_dump_hi_diffs
       | Opt_D_dump_mod_cycles
       | Opt_D_dump_mod_map
       | Opt_D_dump_view_pattern_commoning
       | Opt_D_verbose_core2core
       | Opt_D_dump_debug

       deriving (Eq, Show, Enum)

    -- | Enumerates the simple on-or-off dynamic flags
    data GeneralFlag
    -- See Note [Updating flag description in the User's Guide]

       = Opt_DumpToFile                     -- ^ Append dump output to files instead of stdout.
       | Opt_D_faststring_stats
       | Opt_D_dump_minimal_imports
       | Opt_DoCoreLinting
       | Opt_DoStgLinting
       | Opt_DoCmmLinting
       | Opt_DoAsmLinting
       | Opt_DoAnnotationLinting
       | Opt_NoLlvmMangler                 -- hidden flag

       | Opt_WarnIsError                    -- -Werror; makes warnings fatal

       | Opt_PrintExplicitForalls
       | Opt_PrintExplicitKinds

       -- optimisation opts
       | Opt_CallArity
       | Opt_Strictness
       | Opt_LateDmdAnal
       | Opt_KillAbsence
       | Opt_KillOneShot
       | Opt_FullLaziness
       | Opt_FloatIn
       | Opt_Specialise
       | Opt_SpecialiseAggressively
       | Opt_StaticArgumentTransformation
       | Opt_CSE
       | Opt_LiberateCase
       | Opt_SpecConstr
       | Opt_DoLambdaEtaExpansion
       | Opt_IgnoreAsserts
       | Opt_DoEtaReduction
       | Opt_CaseMerge
       | Opt_UnboxStrictFields
       | Opt_UnboxSmallStrictFields
       | Opt_DictsCheap
       | Opt_EnableRewriteRules             -- Apply rewrite rules during simplification
       | Opt_Vectorise
       | Opt_VectorisationAvoidance
       | Opt_RegsGraph                      -- do graph coloring register allocation
       | Opt_RegsIterative                  -- do iterative coalescing graph coloring register allocation
       | Opt_PedanticBottoms                -- Be picky about how we treat bottom
       | Opt_LlvmTBAA                       -- Use LLVM TBAA infastructure for improving AA (hidden flag)
       | Opt_LlvmPassVectorsInRegisters     -- Pass SIMD vectors in registers (requires a patched LLVM) (hidden flag)
       | Opt_IrrefutableTuples
       | Opt_CmmSink
       | Opt_CmmElimCommonBlocks
       | Opt_OmitYields
       | Opt_SimpleListLiterals
       | Opt_FunToThunk               -- allow WwLib.mkWorkerArgs to remove all value lambdas
       | Opt_DictsStrict                     -- be strict in argument dictionaries
       | Opt_DmdTxDictSel              -- use a special demand transformer for dictionary selectors
       | Opt_Loopification                  -- See Note [Self-recursive tail calls]

       -- Interface files
       | Opt_IgnoreInterfacePragmas
       | Opt_OmitInterfacePragmas
       | Opt_ExposeAllUnfoldings
       | Opt_WriteInterface -- forces .hi files to be written even with -fno-code

       -- profiling opts
       | Opt_AutoSccsOnIndividualCafs
       | Opt_ProfCountEntries

       -- misc opts
       | Opt_Pp
       | Opt_ForceRecomp
       | Opt_ExcessPrecision
       | Opt_EagerBlackHoling
       | Opt_NoHsMain
       | Opt_SplitObjs
       | Opt_StgStats
       | Opt_HideAllPackages
       | Opt_PrintBindResult
       | Opt_Haddock
       | Opt_HaddockOptions
       | Opt_Hpc_No_Auto
       | Opt_BreakOnException
       | Opt_BreakOnError
       | Opt_PrintEvldWithShow
       | Opt_PrintBindContents
       | Opt_GenManifest
       | Opt_EmbedManifest
       | Opt_EmitExternalCore
       | Opt_SharedImplib
       | Opt_BuildingCabalPackage
       | Opt_IgnoreDotGhci
       | Opt_GhciSandbox
       | Opt_GhciHistory
       | Opt_HelpfulErrors
       | Opt_DeferTypeErrors
       | Opt_DeferTypedHoles
       | Opt_Parallel
       | Opt_GranMacros
       | Opt_PIC
       | Opt_SccProfilingOn
       | Opt_Ticky
       | Opt_Ticky_Allocd
       | Opt_Ticky_LNE
       | Opt_Ticky_Dyn_Thunk
       | Opt_Static
       | Opt_RPath
       | Opt_RelativeDynlibPaths
       | Opt_Hpc
       | Opt_FlatCache

       -- PreInlining is on by default. The option is there just to see how
       -- bad things get if you turn it off!
       | Opt_SimplPreInlining

       -- output style opts
       | Opt_ErrorSpans -- Include full span info in error messages,
                        -- instead of just the start position.
       | Opt_PprCaseAsLet
       | Opt_PprShowTicks

       -- Suppress all coercions, them replacing with '...'
       | Opt_SuppressCoercions
       | Opt_SuppressVarKinds
       -- Suppress module id prefixes on variables.
       | Opt_SuppressModulePrefixes
       -- Suppress type applications.
       | Opt_SuppressTypeApplications
       -- Suppress info such as arity and unfoldings on identifiers.
       | Opt_SuppressIdInfo
       -- Suppress separate type signatures in core, but leave types on
       -- lambda bound vars
       | Opt_SuppressTypeSignatures
       -- Suppress unique ids on variables.
       -- Except for uniques, as some simplifier phases introduce new
       -- variables that have otherwise identical names.
       | Opt_SuppressUniques

       -- temporary flags
       | Opt_AutoLinkPackages
       | Opt_ImplicitImportQualified

       -- keeping stuff
       | Opt_KeepHiDiffs
       | Opt_KeepHcFiles
       | Opt_KeepSFiles
       | Opt_KeepTmpFiles
       | Opt_KeepRawTokenStream
       | Opt_KeepLlvmFiles

       | Opt_BuildDynamicToo

       -- safe haskell flags
       | Opt_DistrustAllPackages
       | Opt_PackageTrust

       -- debugging flags
       | Opt_Debug

       deriving (Eq, Show, Enum)

    data WarningFlag =
    -- See Note [Updating flag description in the User's Guide]
         Opt_WarnDuplicateExports
       | Opt_WarnDuplicateConstraints
       | Opt_WarnHiShadows
       | Opt_WarnImplicitPrelude
       | Opt_WarnIncompletePatterns
       | Opt_WarnIncompleteUniPatterns
       | Opt_WarnIncompletePatternsRecUpd
       | Opt_WarnOverflowedLiterals
       | Opt_WarnEmptyEnumerations
       | Opt_WarnMissingFields
       | Opt_WarnMissingImportList
       | Opt_WarnMissingMethods
       | Opt_WarnMissingSigs
       | Opt_WarnMissingLocalSigs
       | Opt_WarnNameShadowing
       | Opt_WarnOverlappingPatterns
       | Opt_WarnTypeDefaults
       | Opt_WarnMonomorphism
       | Opt_WarnUnusedBinds
       | Opt_WarnUnusedImports
       | Opt_WarnUnusedMatches
       | Opt_WarnContextQuantification
       | Opt_WarnWarningsDeprecations
       | Opt_WarnDeprecatedFlags
       | Opt_WarnAMP
       | Opt_WarnDodgyExports
       | Opt_WarnDodgyImports
       | Opt_WarnOrphans
       | Opt_WarnAutoOrphans
       | Opt_WarnIdentities
       | Opt_WarnTabs
       | Opt_WarnUnrecognisedPragmas
       | Opt_WarnDodgyForeignImports
       | Opt_WarnUnusedDoBind
       | Opt_WarnWrongDoBind
       | Opt_WarnAlternativeLayoutRuleTransitional
       | Opt_WarnUnsafe
       | Opt_WarnSafe
       | Opt_WarnTrustworthySafe
       | Opt_WarnPointlessPragmas
       | Opt_WarnUnsupportedCallingConventions
       | Opt_WarnUnsupportedLlvmVersion
       | Opt_WarnInlineRuleShadowing
       | Opt_WarnTypedHoles
       | Opt_WarnPartialTypeSignatures
       | Opt_WarnMissingExportedSigs
       | Opt_WarnUntickedPromotedConstructors
       | Opt_WarnDerivingTypeable
       deriving (Eq, Show, Enum)

    data Language = Haskell98 | Haskell2010
       deriving Enum

    -- | The various Safe Haskell modes
    data SafeHaskellMode
       = Sf_None
       | Sf_Unsafe
       | Sf_Trustworthy
       | Sf_Safe
       deriving (Eq)

    instance Show SafeHaskellMode where
        show Sf_None         = "None"
        show Sf_Unsafe       = "Unsafe"
        show Sf_Trustworthy  = "Trustworthy"
        show Sf_Safe         = "Safe"

    instance Outputable SafeHaskellMode where
        ppr = text . show

    data ExtensionFlag
    -- See Note [Updating flag description in the User's Guide]
       = Opt_Cpp
       | Opt_OverlappingInstances
       | Opt_UndecidableInstances
       | Opt_IncoherentInstances
       | Opt_MonomorphismRestriction
       | Opt_MonoPatBinds
       | Opt_MonoLocalBinds
       | Opt_RelaxedPolyRec           -- Deprecated
       | Opt_ExtendedDefaultRules     -- Use GHC's extended rules for defaulting
       | Opt_ForeignFunctionInterface
       | Opt_UnliftedFFITypes
       | Opt_InterruptibleFFI
       | Opt_CApiFFI
       | Opt_GHCForeignImportPrim
       | Opt_JavaScriptFFI
       | Opt_ParallelArrays           -- Syntactic support for parallel arrays
       | Opt_Arrows                   -- Arrow-notation syntax
       | Opt_TemplateHaskell
       | Opt_QuasiQuotes
       | Opt_ImplicitParams
       | Opt_ImplicitPrelude
       | Opt_ScopedTypeVariables
       | Opt_AllowAmbiguousTypes
       | Opt_UnboxedTuples
       | Opt_BangPatterns
       | Opt_TypeFamilies
       | Opt_OverloadedStrings
       | Opt_OverloadedLists
       | Opt_NumDecimals
       | Opt_DisambiguateRecordFields
       | Opt_RecordWildCards
       | Opt_RecordPuns
       | Opt_ViewPatterns
       | Opt_GADTs
       | Opt_GADTSyntax
       | Opt_NPlusKPatterns
       | Opt_DoAndIfThenElse
       | Opt_RebindableSyntax
       | Opt_ConstraintKinds
       | Opt_PolyKinds                -- Kind polymorphism
       | Opt_DataKinds                -- Datatype promotion
       | Opt_InstanceSigs

       | Opt_StandaloneDeriving
       | Opt_DeriveDataTypeable
       | Opt_AutoDeriveTypeable       -- Automatic derivation of Typeable
       | Opt_DeriveFunctor
       | Opt_DeriveTraversable
       | Opt_DeriveFoldable
       | Opt_DeriveGeneric            -- Allow deriving Generic/1
       | Opt_DefaultSignatures        -- Allow extra signatures for defmeths
       | Opt_DeriveAnyClass           -- Allow deriving any class

       | Opt_TypeSynonymInstances
       | Opt_FlexibleContexts
       | Opt_FlexibleInstances
       | Opt_ConstrainedClassMethods
       | Opt_MultiParamTypeClasses
       | Opt_NullaryTypeClasses
       | Opt_FunctionalDependencies
       | Opt_UnicodeSyntax
       | Opt_ExistentialQuantification
       | Opt_MagicHash
       | Opt_EmptyDataDecls
       | Opt_KindSignatures
       | Opt_RoleAnnotations
       | Opt_ParallelListComp
       | Opt_TransformListComp
       | Opt_MonadComprehensions
       | Opt_GeneralizedNewtypeDeriving
       | Opt_RecursiveDo
       | Opt_PostfixOperators
       | Opt_TupleSections
       | Opt_PatternGuards
       | Opt_LiberalTypeSynonyms
       | Opt_RankNTypes
       | Opt_ImpredicativeTypes
       | Opt_TypeOperators
       | Opt_ExplicitNamespaces
       | Opt_PackageImports
       | Opt_ExplicitForAll
       | Opt_AlternativeLayoutRule
       | Opt_AlternativeLayoutRuleTransitional
       | Opt_DatatypeContexts
       | Opt_NondecreasingIndentation
       | Opt_RelaxedLayout
       | Opt_TraditionalRecordSyntax
       | Opt_LambdaCase
       | Opt_MultiWayIf
       | Opt_BinaryLiterals
       | Opt_NegativeLiterals
       | Opt_EmptyCase
       | Opt_PatternSynonyms
       | Opt_PartialTypeSignatures
       | Opt_NamedWildCards
       | Opt_StaticPointers
       deriving (Eq, Enum, Show)

    data SigOf = NotSigOf
               | SigOf Module
               | SigOfMap (Map ModuleName Module)

    getSigOf :: DynFlags -> ModuleName -> Maybe Module
    getSigOf dflags n =
        case sigOf dflags of
            NotSigOf -> Nothing
            SigOf m -> Just m
            SigOfMap m -> Map.lookup n m

    -- | Contains not only a collection of 'GeneralFlag's but also a plethora of
    -- information relating to the compilation of a single file or GHC session
    data DynFlags = DynFlags {
      ghcMode               :: GhcMode,
      ghcLink               :: GhcLink,
      hscTarget             :: HscTarget,
      settings              :: Settings,
      -- See Note [Signature parameters in TcGblEnv and DynFlags]
      sigOf                 :: SigOf,       -- ^ Compiling an hs-boot against impl.
      verbosity             :: Int,         -- ^ Verbosity level: see Note [Verbosity levels]
      optLevel              :: Int,         -- ^ Optimisation level
      simplPhases           :: Int,         -- ^ Number of simplifier phases
      maxSimplIterations    :: Int,         -- ^ Max simplifier iterations
      ruleCheck             :: Maybe String,
      strictnessBefore      :: [Int],       -- ^ Additional demand analysis

      parMakeCount          :: Maybe Int,   -- ^ The number of modules to compile in parallel
                                            --   in --make mode, where Nothing ==> compile as
                                            --   many in parallel as there are CPUs.

      enableTimeStats       :: Bool,        -- ^ Enable RTS timing statistics?
      ghcHeapSize           :: Maybe Int,   -- ^ The heap size to set.

      maxRelevantBinds      :: Maybe Int,   -- ^ Maximum number of bindings from the type envt
                                            --   to show in type error messages
      simplTickFactor       :: Int,         -- ^ Multiplier for simplifier ticks
      specConstrThreshold   :: Maybe Int,   -- ^ Threshold for SpecConstr
      specConstrCount       :: Maybe Int,   -- ^ Max number of specialisations for any one function
      specConstrRecursive   :: Int,         -- ^ Max number of specialisations for recursive types
                                            --   Not optional; otherwise ForceSpecConstr can diverge.
      liberateCaseThreshold :: Maybe Int,   -- ^ Threshold for LiberateCase
      floatLamArgs          :: Maybe Int,   -- ^ Arg count for lambda floating
                                            --   See CoreMonad.FloatOutSwitches

      historySize           :: Int,

      cmdlineHcIncludes     :: [String],    -- ^ @\-\#includes@
      importPaths           :: [FilePath],
      mainModIs             :: Module,
      mainFunIs             :: Maybe String,
      ctxtStkDepth          :: Int,         -- ^ Typechecker context stack depth
      tyFunStkDepth         :: Int,         -- ^ Typechecker type function stack depth

      thisPackage           :: PackageKey,   -- ^ name of package currently being compiled

      -- ways
      ways                  :: [Way],       -- ^ Way flags from the command line
      buildTag              :: String,      -- ^ The global \"way\" (e.g. \"p\" for prof)
      rtsBuildTag           :: String,      -- ^ The RTS \"way\"

      -- For object splitting
      splitInfo             :: Maybe (String,Int),

      -- paths etc.
      objectDir             :: Maybe String,
      dylibInstallName      :: Maybe String,
      hiDir                 :: Maybe String,
      stubDir               :: Maybe String,
      dumpDir               :: Maybe String,

      objectSuf             :: String,
      hcSuf                 :: String,
      hiSuf                 :: String,

      canGenerateDynamicToo :: IORef Bool,
      dynObjectSuf          :: String,
      dynHiSuf              :: String,

      -- Packages.isDllName needs to know whether a call is within a
      -- single DLL or not. Normally it does this by seeing if the call
      -- is to the same package, but for the ghc package, we split the
      -- package between 2 DLLs. The dllSplit tells us which sets of
      -- modules are in which package.
      dllSplitFile          :: Maybe FilePath,
      dllSplit              :: Maybe [Set String],

      outputFile            :: Maybe String,
      dynOutputFile         :: Maybe String,
      outputHi              :: Maybe String,
      dynLibLoader          :: DynLibLoader,

      -- | This is set by 'DriverPipeline.runPipeline' based on where
      --    its output is going.
      dumpPrefix            :: Maybe FilePath,

      -- | Override the 'dumpPrefix' set by 'DriverPipeline.runPipeline'.
      --    Set by @-ddump-file-prefix@
      dumpPrefixForce       :: Maybe FilePath,

      ldInputs              :: [Option],

      includePaths          :: [String],
      libraryPaths          :: [String],
      frameworkPaths        :: [String],    -- used on darwin only
      cmdlineFrameworks     :: [String],    -- ditto

      rtsOpts               :: Maybe String,
      rtsOptsEnabled        :: RtsOptsEnabled,

      hpcDir                :: String,      -- ^ Path to store the .mix files

      -- Plugins
      pluginModNames        :: [ModuleName],
      pluginModNameOpts     :: [(ModuleName,String)],

      -- GHC API hooks
      hooks                 :: Hooks,

      --  For ghc -M
      depMakefile           :: FilePath,
      depIncludePkgDeps     :: Bool,
      depExcludeMods        :: [ModuleName],
      depSuffixes           :: [String],

      --  Package flags
      extraPkgConfs         :: [PkgConfRef] -> [PkgConfRef],
            -- ^ The @-package-db@ flags given on the command line, in the order
            -- they appeared.

      packageFlags          :: [PackageFlag],
            -- ^ The @-package@ and @-hide-package@ flags from the command-line
      packageEnv            :: Maybe FilePath,
            -- ^ Filepath to the package environment file (if overriding default)

      -- Package state
      -- NB. do not modify this field, it is calculated by
      -- Packages.initPackages and Packages.updatePackages.
      pkgDatabase           :: Maybe [PackageConfig],
      pkgState              :: PackageState,

      -- Temporary files
      -- These have to be IORefs, because the defaultCleanupHandler needs to
      -- know what to clean when an exception happens
      filesToClean          :: IORef [FilePath],
      dirsToClean           :: IORef (Map FilePath FilePath),
      filesToNotIntermediateClean :: IORef [FilePath],
      -- The next available suffix to uniquely name a temp file, updated atomically
      nextTempSuffix        :: IORef Int,

      -- Names of files which were generated from -ddump-to-file; used to
      -- track which ones we need to truncate because it's our first run
      -- through
      generatedDumps        :: IORef (Set FilePath),

      -- hsc dynamic flags
      dumpFlags             :: IntSet,
      generalFlags          :: IntSet,
      warningFlags          :: IntSet,
      -- Don't change this without updating extensionFlags:
      language              :: Maybe Language,
      -- | Safe Haskell mode
      safeHaskell           :: SafeHaskellMode,
      safeInfer             :: Bool,
      safeInferred          :: Bool,
      -- We store the location of where some extension and flags were turned on so
      -- we can produce accurate error messages when Safe Haskell fails due to
      -- them.
      thOnLoc               :: SrcSpan,
      newDerivOnLoc         :: SrcSpan,
      overlapInstLoc        :: SrcSpan,
      incoherentOnLoc       :: SrcSpan,
      pkgTrustOnLoc         :: SrcSpan,
      warnSafeOnLoc         :: SrcSpan,
      warnUnsafeOnLoc       :: SrcSpan,
      trustworthyOnLoc      :: SrcSpan,
      -- Don't change this without updating extensionFlags:
      extensions            :: [OnOff ExtensionFlag],
      -- extensionFlags should always be equal to
      --     flattenExtensionFlags language extensions
      extensionFlags        :: IntSet,

      -- Unfolding control
      -- See Note [Discounts and thresholds] in CoreUnfold
      ufCreationThreshold   :: Int,
      ufUseThreshold        :: Int,
      ufFunAppDiscount      :: Int,
      ufDictDiscount        :: Int,
      ufKeenessFactor       :: Float,
      ufDearOp              :: Int,

      maxWorkerArgs         :: Int,

      ghciHistSize          :: Int,

      -- | MsgDoc output action: use "ErrUtils" instead of this if you can
      log_action            :: LogAction,
      flushOut              :: FlushOut,
      flushErr              :: FlushErr,

      haddockOptions        :: Maybe String,
      ghciScripts           :: [String],

      -- Output style options
      pprUserLength         :: Int,
      pprCols               :: Int,
      traceLevel            :: Int, -- Standard level is 1. Less verbose is 0.

      useUnicode      :: Bool,

      -- | what kind of {-# SCC #-} to add automatically
      profAuto              :: ProfAuto,

      interactivePrint      :: Maybe String,

      llvmVersion           :: IORef Int,

      nextWrapperNum        :: IORef (ModuleEnv Int),

      -- | Machine dependant flags (-m<blah> stuff)
      sseVersion            :: Maybe SseVersion,
      avx                   :: Bool,
      avx2                  :: Bool,
      avx512cd              :: Bool, -- Enable AVX-512 Conflict Detection Instructions.
      avx512er              :: Bool, -- Enable AVX-512 Exponential and Reciprocal Instructions.
      avx512f               :: Bool, -- Enable AVX-512 instructions.
      avx512pf              :: Bool, -- Enable AVX-512 PreFetch Instructions.

      -- | Run-time linker information (what options we need, etc.)
      rtldInfo              :: IORef (Maybe LinkerInfo),

      -- | Run-time compiler information
      rtccInfo              :: IORef (Maybe CompilerInfo),

      -- Constants used to control the amount of optimization done.

      -- | Max size, in bytes, of inline array allocations.
      maxInlineAllocSize    :: Int,

      -- | Only inline memcpy if it generates no more than this many
      -- pseudo (roughly: Cmm) instructions.
      maxInlineMemcpyInsns  :: Int,

      -- | Only inline memset if it generates no more than this many
      -- pseudo (roughly: Cmm) instructions.
      maxInlineMemsetInsns  :: Int
    }

    class HasDynFlags m where
        getDynFlags :: m DynFlags

    class ContainsDynFlags t where
        extractDynFlags :: t -> DynFlags
        replaceDynFlags :: t -> DynFlags -> t

    data ProfAuto
      = NoProfAuto         -- ^ no SCC annotations added
      | ProfAutoAll        -- ^ top-level and nested functions are annotated
      | ProfAutoTop        -- ^ top-level functions annotated only
      | ProfAutoExports    -- ^ exported functions annotated only
      | ProfAutoCalls      -- ^ annotate call-sites
      deriving (Eq,Enum)

    data Settings = Settings {
      sTargetPlatform        :: Platform,    -- Filled in by SysTools
      sGhcUsagePath          :: FilePath,    -- Filled in by SysTools
      sGhciUsagePath         :: FilePath,    -- ditto
      sTopDir                :: FilePath,
      sTmpDir                :: String,      -- no trailing '/'
      sProgramName           :: String,
      sProjectVersion        :: String,
      -- You shouldn't need to look things up in rawSettings directly.
      -- They should have their own fields instead.
      sRawSettings           :: [(String, String)],
      sExtraGccViaCFlags     :: [String],
      sSystemPackageConfig   :: FilePath,
      sLdSupportsCompactUnwind :: Bool,
      sLdSupportsBuildId       :: Bool,
      sLdSupportsFilelist      :: Bool,
      sLdIsGnuLd               :: Bool,
      -- commands for particular phases
      sPgm_L                 :: String,
      sPgm_P                 :: (String,[Option]),
      sPgm_F                 :: String,
      sPgm_c                 :: (String,[Option]),
      sPgm_s                 :: (String,[Option]),
      sPgm_a                 :: (String,[Option]),
      sPgm_l                 :: (String,[Option]),
      sPgm_dll               :: (String,[Option]),
      sPgm_T                 :: String,
      sPgm_sysman            :: String,
      sPgm_windres           :: String,
      sPgm_libtool           :: String,
      sPgm_lo                :: (String,[Option]), -- LLVM: opt llvm optimiser
      sPgm_lc                :: (String,[Option]), -- LLVM: llc static compiler
      -- options for particular phases
      sOpt_L                 :: [String],
      sOpt_P                 :: [String],
      sOpt_F                 :: [String],
      sOpt_c                 :: [String],
      sOpt_a                 :: [String],
      sOpt_l                 :: [String],
      sOpt_windres           :: [String],
      sOpt_lo                :: [String], -- LLVM: llvm optimiser
      sOpt_lc                :: [String], -- LLVM: llc static compiler

      sPlatformConstants     :: PlatformConstants
     }

    targetPlatform :: DynFlags -> Platform
    targetPlatform dflags = sTargetPlatform (settings dflags)
    programName :: DynFlags -> String
    programName dflags = sProgramName (settings dflags)
    projectVersion :: DynFlags -> String
    projectVersion dflags = sProjectVersion (settings dflags)
    ghcUsagePath          :: DynFlags -> FilePath
    ghcUsagePath dflags = sGhcUsagePath (settings dflags)
    ghciUsagePath         :: DynFlags -> FilePath
    ghciUsagePath dflags = sGhciUsagePath (settings dflags)
    topDir                :: DynFlags -> FilePath
    topDir dflags = sTopDir (settings dflags)
    tmpDir                :: DynFlags -> String
    tmpDir dflags = sTmpDir (settings dflags)
    rawSettings           :: DynFlags -> [(String, String)]
    rawSettings dflags = sRawSettings (settings dflags)
    extraGccViaCFlags     :: DynFlags -> [String]
    extraGccViaCFlags dflags = sExtraGccViaCFlags (settings dflags)
    systemPackageConfig   :: DynFlags -> FilePath
    systemPackageConfig dflags = sSystemPackageConfig (settings dflags)
    pgm_L                 :: DynFlags -> String
    pgm_L dflags = sPgm_L (settings dflags)
    pgm_P                 :: DynFlags -> (String,[Option])
    pgm_P dflags = sPgm_P (settings dflags)
    pgm_F                 :: DynFlags -> String
    pgm_F dflags = sPgm_F (settings dflags)
    pgm_c                 :: DynFlags -> (String,[Option])
    pgm_c dflags = sPgm_c (settings dflags)
    pgm_s                 :: DynFlags -> (String,[Option])
    pgm_s dflags = sPgm_s (settings dflags)
    pgm_a                 :: DynFlags -> (String,[Option])
    pgm_a dflags = sPgm_a (settings dflags)
    pgm_l                 :: DynFlags -> (String,[Option])
    pgm_l dflags = sPgm_l (settings dflags)
    pgm_dll               :: DynFlags -> (String,[Option])
    pgm_dll dflags = sPgm_dll (settings dflags)
    pgm_T                 :: DynFlags -> String
    pgm_T dflags = sPgm_T (settings dflags)
    pgm_sysman            :: DynFlags -> String
    pgm_sysman dflags = sPgm_sysman (settings dflags)
    pgm_windres           :: DynFlags -> String
    pgm_windres dflags = sPgm_windres (settings dflags)
    pgm_libtool           :: DynFlags -> String
    pgm_libtool dflags = sPgm_libtool (settings dflags)
    pgm_lo                :: DynFlags -> (String,[Option])
    pgm_lo dflags = sPgm_lo (settings dflags)
    pgm_lc                :: DynFlags -> (String,[Option])
    pgm_lc dflags = sPgm_lc (settings dflags)
    opt_L                 :: DynFlags -> [String]
    opt_L dflags = sOpt_L (settings dflags)
    opt_P                 :: DynFlags -> [String]
    opt_P dflags = concatMap (wayOptP (targetPlatform dflags)) (ways dflags)
                ++ sOpt_P (settings dflags)
    opt_F                 :: DynFlags -> [String]
    opt_F dflags = sOpt_F (settings dflags)
    opt_c                 :: DynFlags -> [String]
    opt_c dflags = concatMap (wayOptc (targetPlatform dflags)) (ways dflags)
                ++ sOpt_c (settings dflags)
    opt_a                 :: DynFlags -> [String]
    opt_a dflags = sOpt_a (settings dflags)
    opt_l                 :: DynFlags -> [String]
    opt_l dflags = concatMap (wayOptl (targetPlatform dflags)) (ways dflags)
                ++ sOpt_l (settings dflags)
    opt_windres           :: DynFlags -> [String]
    opt_windres dflags = sOpt_windres (settings dflags)
    opt_lo                :: DynFlags -> [String]
    opt_lo dflags = sOpt_lo (settings dflags)
    opt_lc                :: DynFlags -> [String]
    opt_lc dflags = sOpt_lc (settings dflags)

    -- | The directory for this version of ghc in the user's app directory
    -- (typically something like @~/.ghc/x86_64-linux-7.6.3@)
    --
    versionedAppDir :: DynFlags -> IO FilePath
    versionedAppDir dflags = do
      appdir <- getAppUserDataDirectory (programName dflags)
      return $ appdir </> (TARGET_ARCH ++ '-':TARGET_OS ++ '-':projectVersion dflags)

    -- | The target code type of the compilation (if any).
    --
    -- Whenever you change the target, also make sure to set 'ghcLink' to
    -- something sensible.
    --
    -- 'HscNothing' can be used to avoid generating any output, however, note
    -- that:
    --
    --  * If a program uses Template Haskell the typechecker may try to run code
    --    from an imported module.  This will fail if no code has been generated
    --    for this module.  You can use 'GHC.needsTemplateHaskell' to detect
    --    whether this might be the case and choose to either switch to a
    --    different target or avoid typechecking such modules.  (The latter may be
    --    preferable for security reasons.)
    --
    data HscTarget
      = HscC           -- ^ Generate C code.
      | HscAsm         -- ^ Generate assembly using the native code generator.
      | HscLlvm        -- ^ Generate assembly using the llvm code generator.
      | HscInterpreted -- ^ Generate bytecode.  (Requires 'LinkInMemory')
      | HscNothing     -- ^ Don't generate any code.  See notes above.
      deriving (Eq, Show)

    -- | Will this target result in an object file on the disk?
    isObjectTarget :: HscTarget -> Bool
    isObjectTarget HscC     = True
    isObjectTarget HscAsm   = True
    isObjectTarget HscLlvm  = True
    isObjectTarget _        = False

    -- | Does this target retain *all* top-level bindings for a module,
    -- rather than just the exported bindings, in the TypeEnv and compiled
    -- code (if any)?  In interpreted mode we do this, so that GHCi can
    -- call functions inside a module.  In HscNothing mode we also do it,
    -- so that Haddock can get access to the GlobalRdrEnv for a module
    -- after typechecking it.
    targetRetainsAllBindings :: HscTarget -> Bool
    targetRetainsAllBindings HscInterpreted = True
    targetRetainsAllBindings HscNothing     = True
    targetRetainsAllBindings _              = False

    -- | The 'GhcMode' tells us whether we're doing multi-module
    -- compilation (controlled via the "GHC" API) or one-shot
    -- (single-module) compilation.  This makes a difference primarily to
    -- the "Finder": in one-shot mode we look for interface files for
    -- imported modules, but in multi-module mode we look for source files
    -- in order to check whether they need to be recompiled.
    data GhcMode
      = CompManager         -- ^ @\-\-make@, GHCi, etc.
      | OneShot             -- ^ @ghc -c Foo.hs@
      | MkDepend            -- ^ @ghc -M@, see "Finder" for why we need this
      deriving Eq

    instance Outputable GhcMode where
      ppr CompManager = ptext (sLit "CompManager")
      ppr OneShot     = ptext (sLit "OneShot")
      ppr MkDepend    = ptext (sLit "MkDepend")

    isOneShot :: GhcMode -> Bool
    isOneShot OneShot = True
    isOneShot _other  = False

    -- | What to do in the link step, if there is one.
    data GhcLink
      = NoLink              -- ^ Don't link at all
      | LinkBinary          -- ^ Link object code into a binary
      | LinkInMemory        -- ^ Use the in-memory dynamic linker (works for both
                            --   bytecode and object code).
      | LinkDynLib          -- ^ Link objects into a dynamic lib (DLL on Windows, DSO on ELF platforms)
      | LinkStaticLib       -- ^ Link objects into a static lib
      deriving (Eq, Show)

    isNoLink :: GhcLink -> Bool
    isNoLink NoLink = True
    isNoLink _      = False

    data PackageArg = PackageArg String
                    | PackageIdArg String
                    | PackageKeyArg String
      deriving (Eq, Show)

    data ModRenaming = ModRenaming Bool [(String, String)]
      deriving (Eq, Show)

    data PackageFlag
      = ExposePackage   PackageArg ModRenaming
      | HidePackage     String
      | IgnorePackage   String
      | TrustPackage    String
      | DistrustPackage String
      deriving (Eq, Show)

    defaultHscTarget :: Platform -> HscTarget
    defaultHscTarget = defaultObjectTarget

    -- | The 'HscTarget' value corresponding to the default way to create
    -- object files on the current platform.
    defaultObjectTarget :: Platform -> HscTarget
    defaultObjectTarget platform
      | platformUnregisterised platform     =  HscC
      | cGhcWithNativeCodeGen == "YES"      =  HscAsm
      | otherwise                           =  HscLlvm

    tablesNextToCode :: DynFlags -> Bool
    tablesNextToCode dflags
        = mkTablesNextToCode (platformUnregisterised (targetPlatform dflags))

    -- Determines whether we will be compiling
    -- info tables that reside just before the entry code, or with an
    -- indirection to the entry code.  See TABLES_NEXT_TO_CODE in
    -- includes/rts/storage/InfoTables.h.
    mkTablesNextToCode :: Bool -> Bool
    mkTablesNextToCode unregisterised
        = not unregisterised && cGhcEnableTablesNextToCode == "YES"

    data DynLibLoader
      = Deployable
      | SystemDependent
      deriving Eq

    data RtsOptsEnabled = RtsOptsNone | RtsOptsSafeOnly | RtsOptsAll
      deriving (Show)

    -----------------------------------------------------------------------------
    -- Ways

    -- The central concept of a "way" is that all objects in a given
    -- program must be compiled in the same "way".  Certain options change
    -- parameters of the virtual machine, eg. profiling adds an extra word
    -- to the object header, so profiling objects cannot be linked with
    -- non-profiling objects.

    -- After parsing the command-line options, we determine which "way" we
    -- are building - this might be a combination way, eg. profiling+threaded.

    -- We then find the "build-tag" associated with this way, and this
    -- becomes the suffix used to find .hi files and libraries used in
    -- this compilation.

    data Way
      = WayCustom String -- for GHC API clients building custom variants
      | WayThreaded
      | WayDebug
      | WayProf
      | WayEventLog
      | WayPar
      | WayGran
      | WayNDP
      | WayDyn
      deriving (Eq, Ord, Show)

    allowed_combination :: [Way] -> Bool
    allowed_combination way = and [ x `allowedWith` y
                                  | x <- way, y <- way, x < y ]
      where
            -- Note ordering in these tests: the left argument is
            -- <= the right argument, according to the Ord instance
            -- on Way above.

            -- dyn is allowed with everything
            _ `allowedWith` WayDyn                  = True
            WayDyn `allowedWith` _                  = True

            -- debug is allowed with everything
            _ `allowedWith` WayDebug                = True
            WayDebug `allowedWith` _                = True

            (WayCustom {}) `allowedWith` _          = True
            WayProf `allowedWith` WayNDP            = True
            WayThreaded `allowedWith` WayProf       = True
            WayThreaded `allowedWith` WayEventLog   = True
            _ `allowedWith` _                       = False

    mkBuildTag :: [Way] -> String
    mkBuildTag ways = concat (intersperse "_" (map wayTag ways))

    wayTag :: Way -> String
    wayTag (WayCustom xs) = xs
    wayTag WayThreaded = "thr"
    wayTag WayDebug    = "debug"
    wayTag WayDyn      = "dyn"
    wayTag WayProf     = "p"
    wayTag WayEventLog = "l"
    wayTag WayPar      = "mp"
    wayTag WayGran     = "mg"
    wayTag WayNDP      = "ndp"

    wayRTSOnly :: Way -> Bool
    wayRTSOnly (WayCustom {}) = False
    wayRTSOnly WayThreaded = True
    wayRTSOnly WayDebug    = True
    wayRTSOnly WayDyn      = False
    wayRTSOnly WayProf     = False
    wayRTSOnly WayEventLog = True
    wayRTSOnly WayPar      = False
    wayRTSOnly WayGran     = False
    wayRTSOnly WayNDP      = False

    wayDesc :: Way -> String
    wayDesc (WayCustom xs) = xs
    wayDesc WayThreaded = "Threaded"
    wayDesc WayDebug    = "Debug"
    wayDesc WayDyn      = "Dynamic"
    wayDesc WayProf     = "Profiling"
    wayDesc WayEventLog = "RTS Event Logging"
    wayDesc WayPar      = "Parallel"
    wayDesc WayGran     = "GranSim"
    wayDesc WayNDP      = "Nested data parallelism"

    -- Turn these flags on when enabling this way
    wayGeneralFlags :: Platform -> Way -> [GeneralFlag]
    wayGeneralFlags _ (WayCustom {}) = []
    wayGeneralFlags _ WayThreaded = []
    wayGeneralFlags _ WayDebug    = []
    wayGeneralFlags _ WayDyn      = [Opt_PIC]
        -- We could get away without adding -fPIC when compiling the
        -- modules of a program that is to be linked with -dynamic; the
        -- program itself does not need to be position-independent, only
        -- the libraries need to be.  HOWEVER, GHCi links objects into a
        -- .so before loading the .so using the system linker.  Since only
        -- PIC objects can be linked into a .so, we have to compile even
        -- modules of the main program with -fPIC when using -dynamic.
    wayGeneralFlags _ WayProf     = [Opt_SccProfilingOn]
    wayGeneralFlags _ WayEventLog = []
    wayGeneralFlags _ WayPar      = [Opt_Parallel]
    wayGeneralFlags _ WayGran     = [Opt_GranMacros]
    wayGeneralFlags _ WayNDP      = []

    -- Turn these flags off when enabling this way
    wayUnsetGeneralFlags :: Platform -> Way -> [GeneralFlag]
    wayUnsetGeneralFlags _ (WayCustom {}) = []
    wayUnsetGeneralFlags _ WayThreaded = []
    wayUnsetGeneralFlags _ WayDebug    = []
    wayUnsetGeneralFlags _ WayDyn      = [-- There's no point splitting objects
                                          -- when we're going to be dynamically
                                          -- linking. Plus it breaks compilation
                                          -- on OSX x86.
                                          Opt_SplitObjs]
    wayUnsetGeneralFlags _ WayProf     = []
    wayUnsetGeneralFlags _ WayEventLog = []
    wayUnsetGeneralFlags _ WayPar      = []
    wayUnsetGeneralFlags _ WayGran     = []
    wayUnsetGeneralFlags _ WayNDP      = []

    wayExtras :: Platform -> Way -> DynFlags -> DynFlags
    wayExtras _ (WayCustom {}) dflags = dflags
    wayExtras _ WayThreaded dflags = dflags
    wayExtras _ WayDebug    dflags = dflags
    wayExtras _ WayDyn      dflags = dflags
    wayExtras _ WayProf     dflags = dflags
    wayExtras _ WayEventLog dflags = dflags
    wayExtras _ WayPar      dflags = exposePackage' "concurrent" dflags
    wayExtras _ WayGran     dflags = exposePackage' "concurrent" dflags
    wayExtras _ WayNDP      dflags = setExtensionFlag' Opt_ParallelArrays
                                   $ setGeneralFlag' Opt_Vectorise dflags

    wayOptc :: Platform -> Way -> [String]
    wayOptc _ (WayCustom {}) = []
    wayOptc platform WayThreaded = case platformOS platform of
                                   OSOpenBSD -> ["-pthread"]
                                   OSNetBSD  -> ["-pthread"]
                                   _         -> []
    wayOptc _ WayDebug      = []
    wayOptc _ WayDyn        = []
    wayOptc _ WayProf       = ["-DPROFILING"]
    wayOptc _ WayEventLog   = ["-DTRACING"]
    wayOptc _ WayPar        = ["-DPAR", "-w"]
    wayOptc _ WayGran       = ["-DGRAN"]
    wayOptc _ WayNDP        = []

    wayOptl :: Platform -> Way -> [String]
    wayOptl _ (WayCustom {}) = []
    wayOptl platform WayThreaded =
            case platformOS platform of
            -- FreeBSD's default threading library is the KSE-based M:N libpthread,
            -- which GHC has some problems with.  It's currently not clear whether
            -- the problems are our fault or theirs, but it seems that using the
            -- alternative 1:1 threading library libthr works around it:
            OSFreeBSD  -> ["-lthr"]
            OSOpenBSD  -> ["-pthread"]
            OSNetBSD   -> ["-pthread"]
            _          -> []
    wayOptl _ WayDebug      = []
    wayOptl _ WayDyn        = []
    wayOptl _ WayProf       = []
    wayOptl _ WayEventLog   = []
    wayOptl _ WayPar        = ["-L${PVM_ROOT}/lib/${PVM_ARCH}",
                               "-lpvm3",
                               "-lgpvm3"]
    wayOptl _ WayGran       = []
    wayOptl _ WayNDP        = []

    wayOptP :: Platform -> Way -> [String]
    wayOptP _ (WayCustom {}) = []
    wayOptP _ WayThreaded = []
    wayOptP _ WayDebug    = []
    wayOptP _ WayDyn      = []
    wayOptP _ WayProf     = ["-DPROFILING"]
    wayOptP _ WayEventLog = ["-DTRACING"]
    wayOptP _ WayPar      = ["-D__PARALLEL_HASKELL__"]
    wayOptP _ WayGran     = ["-D__GRANSIM__"]
    wayOptP _ WayNDP      = []

    whenGeneratingDynamicToo :: MonadIO m => DynFlags -> m () -> m ()
    whenGeneratingDynamicToo dflags f = ifGeneratingDynamicToo dflags f (return ())

    ifGeneratingDynamicToo :: MonadIO m => DynFlags -> m a -> m a -> m a
    ifGeneratingDynamicToo dflags f g = generateDynamicTooConditional dflags f g g

    whenCannotGenerateDynamicToo :: MonadIO m => DynFlags -> m () -> m ()
    whenCannotGenerateDynamicToo dflags f
        = ifCannotGenerateDynamicToo dflags f (return ())

    ifCannotGenerateDynamicToo :: MonadIO m => DynFlags -> m a -> m a -> m a
    ifCannotGenerateDynamicToo dflags f g
        = generateDynamicTooConditional dflags g f g

    generateDynamicTooConditional :: MonadIO m
                                  => DynFlags -> m a -> m a -> m a -> m a
    generateDynamicTooConditional dflags canGen cannotGen notTryingToGen
        = if gopt Opt_BuildDynamicToo dflags
          then do let ref = canGenerateDynamicToo dflags
                  b <- liftIO $ readIORef ref
                  if b then canGen else cannotGen
          else notTryingToGen

    dynamicTooMkDynamicDynFlags :: DynFlags -> DynFlags
    dynamicTooMkDynamicDynFlags dflags0
        = let dflags1 = addWay' WayDyn dflags0
              dflags2 = dflags1 {
                            outputFile = dynOutputFile dflags1,
                            hiSuf = dynHiSuf dflags1,
                            objectSuf = dynObjectSuf dflags1
                        }
              dflags3 = updateWays dflags2
              dflags4 = gopt_unset dflags3 Opt_BuildDynamicToo
          in dflags4

    -----------------------------------------------------------------------------

    -- | Used by 'GHC.runGhc' to partially initialize a new 'DynFlags' value
    initDynFlags :: DynFlags -> IO DynFlags
    initDynFlags dflags = do
     let -- We can't build with dynamic-too on Windows, as labels before
         -- the fork point are different depending on whether we are
         -- building dynamically or not.
         platformCanGenerateDynamicToo
             = platformOS (targetPlatform dflags) /= OSMinGW32
     refCanGenerateDynamicToo <- newIORef platformCanGenerateDynamicToo
     refNextTempSuffix <- newIORef 0
     refFilesToClean <- newIORef []
     refDirsToClean <- newIORef Map.empty
     refFilesToNotIntermediateClean <- newIORef []
     refGeneratedDumps <- newIORef Set.empty
     refLlvmVersion <- newIORef 28
     refRtldInfo <- newIORef Nothing
     refRtccInfo <- newIORef Nothing
     wrapperNum <- newIORef emptyModuleEnv
     canUseUnicode <- do let enc = localeEncoding
                             str = "‘’"
                         (withCString enc str $ \cstr ->
                              do str' <- peekCString enc cstr
                                 return (str == str'))
                             `catchIOError` \_ -> return False
     return dflags{
            canGenerateDynamicToo = refCanGenerateDynamicToo,
            nextTempSuffix = refNextTempSuffix,
            filesToClean   = refFilesToClean,
            dirsToClean    = refDirsToClean,
            filesToNotIntermediateClean = refFilesToNotIntermediateClean,
            generatedDumps = refGeneratedDumps,
            llvmVersion    = refLlvmVersion,
            nextWrapperNum = wrapperNum,
            useUnicode    = canUseUnicode,
            rtldInfo      = refRtldInfo,
            rtccInfo      = refRtccInfo
            }

    -- | The normal 'DynFlags'. Note that they are not suitable for use in this form
    -- and must be fully initialized by 'GHC.runGhc' first.
    defaultDynFlags :: Settings -> DynFlags
    defaultDynFlags mySettings =
    -- See Note [Updating flag description in the User's Guide]
         DynFlags {
            ghcMode                 = CompManager,
            ghcLink                 = LinkBinary,
            hscTarget               = defaultHscTarget (sTargetPlatform mySettings),
            sigOf                   = NotSigOf,
            verbosity               = 0,
            optLevel                = 0,
            simplPhases             = 2,
            maxSimplIterations      = 4,
            ruleCheck               = Nothing,
            maxRelevantBinds        = Just 6,
            simplTickFactor         = 100,
            specConstrThreshold     = Just 2000,
            specConstrCount         = Just 3,
            specConstrRecursive     = 3,
            liberateCaseThreshold   = Just 2000,
            floatLamArgs            = Just 0, -- Default: float only if no fvs

            historySize             = 20,
            strictnessBefore        = [],

            parMakeCount            = Just 1,

            enableTimeStats         = False,
            ghcHeapSize             = Nothing,

            cmdlineHcIncludes       = [],
            importPaths             = ["."],
            mainModIs               = mAIN,
            mainFunIs               = Nothing,
            ctxtStkDepth            = mAX_CONTEXT_REDUCTION_DEPTH,
            tyFunStkDepth           = mAX_TYPE_FUNCTION_REDUCTION_DEPTH,

            thisPackage             = mainPackageKey,

            objectDir               = Nothing,
            dylibInstallName        = Nothing,
            hiDir                   = Nothing,
            stubDir                 = Nothing,
            dumpDir                 = Nothing,

            objectSuf               = phaseInputExt StopLn,
            hcSuf                   = phaseInputExt HCc,
            hiSuf                   = "hi",

            canGenerateDynamicToo   = panic "defaultDynFlags: No canGenerateDynamicToo",
            dynObjectSuf            = "dyn_" ++ phaseInputExt StopLn,
            dynHiSuf                = "dyn_hi",

            dllSplitFile            = Nothing,
            dllSplit                = Nothing,

            pluginModNames          = [],
            pluginModNameOpts       = [],
            hooks                   = emptyHooks,

            outputFile              = Nothing,
            dynOutputFile           = Nothing,
            outputHi                = Nothing,
            dynLibLoader            = SystemDependent,
            dumpPrefix              = Nothing,
            dumpPrefixForce         = Nothing,
            ldInputs                = [],
            includePaths            = [],
            libraryPaths            = [],
            frameworkPaths          = [],
            cmdlineFrameworks       = [],
            rtsOpts                 = Nothing,
            rtsOptsEnabled          = RtsOptsSafeOnly,

            hpcDir                  = ".hpc",

            extraPkgConfs           = id,
            packageFlags            = [],
            packageEnv              = Nothing,
            pkgDatabase             = Nothing,
            pkgState                = panic "no package state yet: call GHC.setSessionDynFlags",
            ways                    = defaultWays mySettings,
            buildTag                = mkBuildTag (defaultWays mySettings),
            rtsBuildTag             = mkBuildTag (defaultWays mySettings),
            splitInfo               = Nothing,
            settings                = mySettings,
            -- ghc -M values
            depMakefile       = "Makefile",
            depIncludePkgDeps = False,
            depExcludeMods    = [],
            depSuffixes       = [],
            -- end of ghc -M values
            nextTempSuffix = panic "defaultDynFlags: No nextTempSuffix",
            filesToClean   = panic "defaultDynFlags: No filesToClean",
            dirsToClean    = panic "defaultDynFlags: No dirsToClean",
            filesToNotIntermediateClean = panic "defaultDynFlags: No filesToNotIntermediateClean",
            generatedDumps = panic "defaultDynFlags: No generatedDumps",
            haddockOptions = Nothing,
            dumpFlags = IntSet.empty,
            generalFlags = IntSet.fromList (map fromEnum (defaultFlags mySettings)),
            warningFlags = IntSet.fromList (map fromEnum standardWarnings),
            ghciScripts = [],
            language = Nothing,
            safeHaskell = Sf_None,
            safeInfer   = True,
            safeInferred = True,
            thOnLoc = noSrcSpan,
            newDerivOnLoc = noSrcSpan,
            overlapInstLoc = noSrcSpan,
            incoherentOnLoc = noSrcSpan,
            pkgTrustOnLoc = noSrcSpan,
            warnSafeOnLoc = noSrcSpan,
            warnUnsafeOnLoc = noSrcSpan,
            trustworthyOnLoc = noSrcSpan,
            extensions = [],
            extensionFlags = flattenExtensionFlags Nothing [],

            -- The ufCreationThreshold threshold must be reasonably high to
            -- take account of possible discounts.
            -- E.g. 450 is not enough in 'fulsom' for Interval.sqr to inline
            -- into Csg.calc (The unfolding for sqr never makes it into the
            -- interface file.)
            ufCreationThreshold = 750,
            ufUseThreshold      = 60,
            ufFunAppDiscount    = 60,
            -- Be fairly keen to inline a fuction if that means
            -- we'll be able to pick the right method from a dictionary
            ufDictDiscount      = 30,
            ufKeenessFactor     = 1.5,
            ufDearOp            = 40,

            maxWorkerArgs = 10,

            ghciHistSize = 50, -- keep a log of length 50 by default

            log_action = defaultLogAction,
            flushOut = defaultFlushOut,
            flushErr = defaultFlushErr,
            pprUserLength = 5,
            pprCols = 100,
            useUnicode = False,
            traceLevel = 1,
            profAuto = NoProfAuto,
            llvmVersion = panic "defaultDynFlags: No llvmVersion",
            interactivePrint = Nothing,
            nextWrapperNum = panic "defaultDynFlags: No nextWrapperNum",
            sseVersion = Nothing,
            avx = False,
            avx2 = False,
            avx512cd = False,
            avx512er = False,
            avx512f = False,
            avx512pf = False,
            rtldInfo = panic "defaultDynFlags: no rtldInfo",
            rtccInfo = panic "defaultDynFlags: no rtccInfo",

            maxInlineAllocSize = 128,
            maxInlineMemcpyInsns = 32,
            maxInlineMemsetInsns = 32
          }

    defaultWays :: Settings -> [Way]
    defaultWays settings = if pc_DYNAMIC_BY_DEFAULT (sPlatformConstants settings)
                           then [WayDyn]
                           else []

    interpWays :: [Way]
    interpWays = if dynamicGhc
                 then [WayDyn]
                 else []

    --------------------------------------------------------------------------

    type FatalMessager = String -> IO ()
    type LogAction = DynFlags -> Severity -> SrcSpan -> PprStyle -> MsgDoc -> IO ()

    defaultFatalMessager :: FatalMessager
    defaultFatalMessager = hPutStrLn stderr

    defaultLogAction :: LogAction
    defaultLogAction dflags severity srcSpan style msg
        = case severity of
          SevOutput      -> printSDoc msg style
          SevDump        -> printSDoc (msg $$ blankLine) style
          SevInteractive -> putStrSDoc msg style
          SevInfo        -> printErrs msg style
          SevFatal       -> printErrs msg style
          _              -> do hPutChar stderr '\n'
                               printErrs (mkLocMessage severity srcSpan msg) style
                               -- careful (#2302): printErrs prints in UTF-8,
                               -- whereas converting to string first and using
                               -- hPutStr would just emit the low 8 bits of
                               -- each unicode char.
        where printSDoc  = defaultLogActionHPrintDoc  dflags stdout
              printErrs  = defaultLogActionHPrintDoc  dflags stderr
              putStrSDoc = defaultLogActionHPutStrDoc dflags stdout

    defaultLogActionHPrintDoc :: DynFlags -> Handle -> SDoc -> PprStyle -> IO ()
    defaultLogActionHPrintDoc dflags h d sty
     = defaultLogActionHPutStrDoc dflags h (d $$ text "") sty
          -- Adds a newline

    defaultLogActionHPutStrDoc :: DynFlags -> Handle -> SDoc -> PprStyle -> IO ()
    defaultLogActionHPutStrDoc dflags h d sty
      = Pretty.printDoc_ Pretty.PageMode (pprCols dflags) h doc
      where   -- Don't add a newline at the end, so that successive
              -- calls to this log-action can output all on the same line
        doc = runSDoc d (initSDocContext dflags sty)

    newtype FlushOut = FlushOut (IO ())

    defaultFlushOut :: FlushOut
    defaultFlushOut = FlushOut $ hFlush stdout

    newtype FlushErr = FlushErr (IO ())

    defaultFlushErr :: FlushErr
    defaultFlushErr = FlushErr $ hFlush stderr

    {-
    Note [Verbosity levels]
    ~~~~~~~~~~~~~~~~~~~~~~~
        0   |   print errors & warnings only
        1   |   minimal verbosity: print "compiling M ... done." for each module.
        2   |   equivalent to -dshow-passes
        3   |   equivalent to existing "ghc -v"
        4   |   "ghc -v -ddump-most"
        5   |   "ghc -v -ddump-all"
    -}

    data OnOff a = On a
                 | Off a

    -- OnOffs accumulate in reverse order, so we use foldr in order to
    -- process them in the right order
    flattenExtensionFlags :: Maybe Language -> [OnOff ExtensionFlag] -> IntSet
    flattenExtensionFlags ml = foldr f defaultExtensionFlags
        where f (On f)  flags = IntSet.insert (fromEnum f) flags
              f (Off f) flags = IntSet.delete (fromEnum f) flags
              defaultExtensionFlags = IntSet.fromList (map fromEnum (languageExtensions ml))

    languageExtensions :: Maybe Language -> [ExtensionFlag]

    languageExtensions Nothing
        -- Nothing => the default case
        = Opt_NondecreasingIndentation -- This has been on by default for some time
        : delete Opt_DatatypeContexts  -- The Haskell' committee decided to
                                       -- remove datatype contexts from the
                                       -- language:
       -- http://www.haskell.org/pipermail/haskell-prime/2011-January/003335.html
          (languageExtensions (Just Haskell2010))

       -- NB: MonoPatBinds is no longer the default

    languageExtensions (Just Haskell98)
        = [Opt_ImplicitPrelude,
           Opt_MonomorphismRestriction,
           Opt_NPlusKPatterns,
           Opt_DatatypeContexts,
           Opt_TraditionalRecordSyntax,
           Opt_NondecreasingIndentation
               -- strictly speaking non-standard, but we always had this
               -- on implicitly before the option was added in 7.1, and
               -- turning it off breaks code, so we're keeping it on for
               -- backwards compatibility.  Cabal uses -XHaskell98 by
               -- default unless you specify another language.
          ]

    languageExtensions (Just Haskell2010)
        = [Opt_ImplicitPrelude,
           Opt_MonomorphismRestriction,
           Opt_DatatypeContexts,
           Opt_TraditionalRecordSyntax,
           Opt_EmptyDataDecls,
           Opt_ForeignFunctionInterface,
           Opt_PatternGuards,
           Opt_DoAndIfThenElse,
           Opt_RelaxedPolyRec]

    -- | Test whether a 'DumpFlag' is set
    dopt :: DumpFlag -> DynFlags -> Bool
    dopt f dflags = (fromEnum f `IntSet.member` dumpFlags dflags)
                 || (verbosity dflags >= 4 && enableIfVerbose f)
        where enableIfVerbose Opt_D_dump_tc_trace               = False
              enableIfVerbose Opt_D_dump_rn_trace               = False
              enableIfVerbose Opt_D_dump_cs_trace               = False
              enableIfVerbose Opt_D_dump_if_trace               = False
              enableIfVerbose Opt_D_dump_vt_trace               = False
              enableIfVerbose Opt_D_dump_tc                     = False
              enableIfVerbose Opt_D_dump_rn                     = False
              enableIfVerbose Opt_D_dump_rn_stats               = False
              enableIfVerbose Opt_D_dump_hi_diffs               = False
              enableIfVerbose Opt_D_verbose_core2core           = False
              enableIfVerbose Opt_D_verbose_stg2stg             = False
              enableIfVerbose Opt_D_dump_splices                = False
              enableIfVerbose Opt_D_th_dec_file                 = False
              enableIfVerbose Opt_D_dump_rule_firings           = False
              enableIfVerbose Opt_D_dump_rule_rewrites          = False
              enableIfVerbose Opt_D_dump_simpl_trace            = False
              enableIfVerbose Opt_D_dump_rtti                   = False
              enableIfVerbose Opt_D_dump_inlinings              = False
              enableIfVerbose Opt_D_dump_core_stats             = False
              enableIfVerbose Opt_D_dump_asm_stats              = False
              enableIfVerbose Opt_D_dump_types                  = False
              enableIfVerbose Opt_D_dump_simpl_iterations       = False
              enableIfVerbose Opt_D_dump_ticked                 = False
              enableIfVerbose Opt_D_dump_view_pattern_commoning = False
              enableIfVerbose Opt_D_dump_mod_cycles             = False
              enableIfVerbose Opt_D_dump_mod_map                = False
              enableIfVerbose _                                 = True

    -- | Set a 'DumpFlag'
    dopt_set :: DynFlags -> DumpFlag -> DynFlags
    dopt_set dfs f = dfs{ dumpFlags = IntSet.insert (fromEnum f) (dumpFlags dfs) }

    -- | Unset a 'DumpFlag'
    dopt_unset :: DynFlags -> DumpFlag -> DynFlags
    dopt_unset dfs f = dfs{ dumpFlags = IntSet.delete (fromEnum f) (dumpFlags dfs) }

    -- | Test whether a 'GeneralFlag' is set
    gopt :: GeneralFlag -> DynFlags -> Bool
    gopt f dflags  = fromEnum f `IntSet.member` generalFlags dflags

    -- | Set a 'GeneralFlag'
    gopt_set :: DynFlags -> GeneralFlag -> DynFlags
    gopt_set dfs f = dfs{ generalFlags = IntSet.insert (fromEnum f) (generalFlags dfs) }

    -- | Unset a 'GeneralFlag'
    gopt_unset :: DynFlags -> GeneralFlag -> DynFlags
    gopt_unset dfs f = dfs{ generalFlags = IntSet.delete (fromEnum f) (generalFlags dfs) }

    -- | Test whether a 'WarningFlag' is set
    wopt :: WarningFlag -> DynFlags -> Bool
    wopt f dflags  = fromEnum f `IntSet.member` warningFlags dflags

    -- | Set a 'WarningFlag'
    wopt_set :: DynFlags -> WarningFlag -> DynFlags
    wopt_set dfs f = dfs{ warningFlags = IntSet.insert (fromEnum f) (warningFlags dfs) }

    -- | Unset a 'WarningFlag'
    wopt_unset :: DynFlags -> WarningFlag -> DynFlags
    wopt_unset dfs f = dfs{ warningFlags = IntSet.delete (fromEnum f) (warningFlags dfs) }

    -- | Test whether a 'ExtensionFlag' is set
    xopt :: ExtensionFlag -> DynFlags -> Bool
    xopt f dflags = fromEnum f `IntSet.member` extensionFlags dflags

    -- | Set a 'ExtensionFlag'
    xopt_set :: DynFlags -> ExtensionFlag -> DynFlags
    xopt_set dfs f
        = let onoffs = On f : extensions dfs
          in dfs { extensions = onoffs,
                   extensionFlags = flattenExtensionFlags (language dfs) onoffs }

    -- | Unset a 'ExtensionFlag'
    xopt_unset :: DynFlags -> ExtensionFlag -> DynFlags
    xopt_unset dfs f
        = let onoffs = Off f : extensions dfs
          in dfs { extensions = onoffs,
                   extensionFlags = flattenExtensionFlags (language dfs) onoffs }

    lang_set :: DynFlags -> Maybe Language -> DynFlags
    lang_set dflags lang =
       dflags {
                language = lang,
                extensionFlags = flattenExtensionFlags lang (extensions dflags)
              }

    useUnicodeSyntax :: DynFlags -> Bool
    useUnicodeSyntax = xopt Opt_UnicodeSyntax

    -- | Set the Haskell language standard to use
    setLanguage :: Language -> DynP ()
    setLanguage l = upd (`lang_set` Just l)

    -- | Some modules have dependencies on others through the DynFlags rather than textual imports
    dynFlagDependencies :: DynFlags -> [ModuleName]
    dynFlagDependencies = pluginModNames

    -- | Is the -fpackage-trust mode on
    packageTrustOn :: DynFlags -> Bool
    packageTrustOn = gopt Opt_PackageTrust

    -- | Is Safe Haskell on in some way (including inference mode)
    safeHaskellOn :: DynFlags -> Bool
    safeHaskellOn dflags = safeHaskell dflags /= Sf_None || safeInferOn dflags

    -- | Is the Safe Haskell safe language in use
    safeLanguageOn :: DynFlags -> Bool
    safeLanguageOn dflags = safeHaskell dflags == Sf_Safe

    -- | Is the Safe Haskell safe inference mode active
    safeInferOn :: DynFlags -> Bool
    safeInferOn = safeInfer

    -- | Test if Safe Imports are on in some form
    safeImportsOn :: DynFlags -> Bool
    safeImportsOn dflags = safeHaskell dflags == Sf_Unsafe ||
                           safeHaskell dflags == Sf_Trustworthy ||
                           safeHaskell dflags == Sf_Safe

    -- | Set a 'Safe Haskell' flag
    setSafeHaskell :: SafeHaskellMode -> DynP ()
    setSafeHaskell s = updM f
        where f dfs = do
                  let sf = safeHaskell dfs
                  safeM <- combineSafeFlags sf s
                  case s of
                    Sf_Safe -> return $ dfs { safeHaskell = safeM, safeInfer = False }
                    -- leave safe inferrence on in Trustworthy mode so we can warn
                    -- if it could have been inferred safe.
                    Sf_Trustworthy -> do
                      l <- getCurLoc
                      return $ dfs { safeHaskell = safeM, trustworthyOnLoc = l }
                    -- leave safe inference on in Unsafe mode as well.
                    _ -> return $ dfs { safeHaskell = safeM }

    -- | Are all direct imports required to be safe for this Safe Haskell mode?
    -- Direct imports are when the code explicitly imports a module
    safeDirectImpsReq :: DynFlags -> Bool
    safeDirectImpsReq d = safeLanguageOn d

    -- | Are all implicit imports required to be safe for this Safe Haskell mode?
    -- Implicit imports are things in the prelude. e.g System.IO when print is used.
    safeImplicitImpsReq :: DynFlags -> Bool
    safeImplicitImpsReq d = safeLanguageOn d

    -- | Combine two Safe Haskell modes correctly. Used for dealing with multiple flags.
    -- This makes Safe Haskell very much a monoid but for now I prefer this as I don't
    -- want to export this functionality from the module but do want to export the
    -- type constructors.
    combineSafeFlags :: SafeHaskellMode -> SafeHaskellMode -> DynP SafeHaskellMode
    combineSafeFlags a b | a == Sf_None         = return b
                         | b == Sf_None         = return a
                         | a == b               = return a
                         | otherwise            = addErr errm >> return (panic errm)
        where errm = "Incompatible Safe Haskell flags! ("
                        ++ show a ++ ", " ++ show b ++ ")"

    -- | A list of unsafe flags under Safe Haskell. Tuple elements are:
    --     * name of the flag
    --     * function to get srcspan that enabled the flag
    --     * function to test if the flag is on
    --     * function to turn the flag off
    unsafeFlags, unsafeFlagsForInfer
      :: [(String, DynFlags -> SrcSpan, DynFlags -> Bool, DynFlags -> DynFlags)]
    unsafeFlags = [ ("-XGeneralizedNewtypeDeriving", newDerivOnLoc,
                        xopt Opt_GeneralizedNewtypeDeriving,
                        flip xopt_unset Opt_GeneralizedNewtypeDeriving)
                  , ("-XTemplateHaskell", thOnLoc,
                        xopt Opt_TemplateHaskell,
                        flip xopt_unset Opt_TemplateHaskell)
                  ]
    unsafeFlagsForInfer = unsafeFlags ++
                  -- TODO: Can we do better than this for inference?
                  [ ("-XOverlappingInstances", overlapInstLoc,
                      xopt Opt_OverlappingInstances,
                      flip xopt_unset Opt_OverlappingInstances)
                  , ("-XIncoherentInstances", incoherentOnLoc,
                      xopt Opt_IncoherentInstances,
                      flip xopt_unset Opt_IncoherentInstances)
                  ]

    -- | Retrieve the options corresponding to a particular @opt_*@ field in the correct order
    getOpts :: DynFlags             -- ^ 'DynFlags' to retrieve the options from
            -> (DynFlags -> [a])    -- ^ Relevant record accessor: one of the @opt_*@ accessors
            -> [a]                  -- ^ Correctly ordered extracted options
    getOpts dflags opts = reverse (opts dflags)
            -- We add to the options from the front, so we need to reverse the list

    -- | Gets the verbosity flag for the current verbosity level. This is fed to
    -- other tools, so GHC-specific verbosity flags like @-ddump-most@ are not included
    getVerbFlags :: DynFlags -> [String]
    getVerbFlags dflags
      | verbosity dflags >= 4 = ["-v"]
      | otherwise             = []

    setObjectDir, setHiDir, setStubDir, setDumpDir, setOutputDir,
             setDynObjectSuf, setDynHiSuf,
             setDylibInstallName,
             setObjectSuf, setHiSuf, setHcSuf, parseDynLibLoaderMode,
             setPgmP, addOptl, addOptc, addOptP,
             addCmdlineFramework, addHaddockOpts, addGhciScript,
             setInteractivePrint
       :: String -> DynFlags -> DynFlags
    setOutputFile, setDynOutputFile, setOutputHi, setDumpPrefixForce
       :: Maybe String -> DynFlags -> DynFlags

    setObjectDir  f d = d{ objectDir  = Just f}
    setHiDir      f d = d{ hiDir      = Just f}
    setStubDir    f d = d{ stubDir    = Just f, includePaths = f : includePaths d }
      -- -stubdir D adds an implicit -I D, so that gcc can find the _stub.h file
      -- \#included from the .hc file when compiling via C (i.e. unregisterised
      -- builds).
    setDumpDir    f d = d{ dumpDir    = Just f}
    setOutputDir  f = setObjectDir f . setHiDir f . setStubDir f . setDumpDir f
    setDylibInstallName  f d = d{ dylibInstallName = Just f}

    setObjectSuf    f d = d{ objectSuf    = f}
    setDynObjectSuf f d = d{ dynObjectSuf = f}
    setHiSuf        f d = d{ hiSuf        = f}
    setDynHiSuf     f d = d{ dynHiSuf     = f}
    setHcSuf        f d = d{ hcSuf        = f}

    setOutputFile f d = d{ outputFile = f}
    setDynOutputFile f d = d{ dynOutputFile = f}
    setOutputHi   f d = d{ outputHi   = f}

    parseSigOf :: String -> SigOf
    parseSigOf str = case filter ((=="").snd) (readP_to_S parse str) of
        [(r, "")] -> r
        _ -> throwGhcException $ CmdLineError ("Can't parse -sig-of: " ++ str)
      where parse = parseOne +++ parseMany
            parseOne = SigOf `fmap` parseModule
            parseMany = SigOfMap . Map.fromList <$> sepBy parseEntry (R.char ',')
            parseEntry = do
                n <- tok $ parseModuleName
                -- ToDo: deprecate this 'is' syntax?
                tok $ ((string "is" >> return ()) +++ (R.char '=' >> return ()))
                m <- tok $ parseModule
                return (mkModuleName n, m)
            parseModule = do
                pk <- munch1 (\c -> isAlphaNum c || c `elem` "-_")
                _ <- R.char ':'
                m <- parseModuleName
                return (mkModule (stringToPackageKey pk) (mkModuleName m))
            tok m = skipSpaces >> m

    setSigOf :: String -> DynFlags -> DynFlags
    setSigOf s d = d { sigOf = parseSigOf s }

    addPluginModuleName :: String -> DynFlags -> DynFlags
    addPluginModuleName name d = d { pluginModNames = (mkModuleName name) : (pluginModNames d) }

    addPluginModuleNameOption :: String -> DynFlags -> DynFlags
    addPluginModuleNameOption optflag d = d { pluginModNameOpts = (mkModuleName m, option) : (pluginModNameOpts d) }
      where (m, rest) = break (== ':') optflag
            option = case rest of
              [] -> "" -- should probably signal an error
              (_:plug_opt) -> plug_opt -- ignore the ':' from break

    parseDynLibLoaderMode f d =
     case splitAt 8 f of
       ("deploy", "")       -> d{ dynLibLoader = Deployable }
       ("sysdep", "")       -> d{ dynLibLoader = SystemDependent }
       _                    -> throwGhcException (CmdLineError ("Unknown dynlib loader: " ++ f))

    setDumpPrefixForce f d = d { dumpPrefixForce = f}

    -- XXX HACK: Prelude> words "'does not' work" ===> ["'does","not'","work"]
    -- Config.hs should really use Option.
    setPgmP   f = let (pgm:args) = words f in alterSettings (\s -> s { sPgm_P   = (pgm, map Option args)})
    addOptl   f = alterSettings (\s -> s { sOpt_l   = f : sOpt_l s})
    addOptc   f = alterSettings (\s -> s { sOpt_c   = f : sOpt_c s})
    addOptP   f = alterSettings (\s -> s { sOpt_P   = f : sOpt_P s})

    setDepMakefile :: FilePath -> DynFlags -> DynFlags
    setDepMakefile f d = d { depMakefile = f }

    setDepIncludePkgDeps :: Bool -> DynFlags -> DynFlags
    setDepIncludePkgDeps b d = d { depIncludePkgDeps = b }

    addDepExcludeMod :: String -> DynFlags -> DynFlags
    addDepExcludeMod m d
        = d { depExcludeMods = mkModuleName m : depExcludeMods d }

    addDepSuffix :: FilePath -> DynFlags -> DynFlags
    addDepSuffix s d = d { depSuffixes = s : depSuffixes d }

    addCmdlineFramework f d = d{ cmdlineFrameworks = f : cmdlineFrameworks d}

    addHaddockOpts f d = d{ haddockOptions = Just f}

    addGhciScript f d = d{ ghciScripts = f : ghciScripts d}

    setInteractivePrint f d = d{ interactivePrint = Just f}

    -- -----------------------------------------------------------------------------
    -- Command-line options

    -- | When invoking external tools as part of the compilation pipeline, we
    -- pass these a sequence of options on the command-line. Rather than
    -- just using a list of Strings, we use a type that allows us to distinguish
    -- between filepaths and 'other stuff'. The reason for this is that
    -- this type gives us a handle on transforming filenames, and filenames only,
    -- to whatever format they're expected to be on a particular platform.
    data Option
     = FileOption -- an entry that _contains_ filename(s) / filepaths.
                  String  -- a non-filepath prefix that shouldn't be
                          -- transformed (e.g., "/out=")
                  String  -- the filepath/filename portion
     | Option     String
     deriving ( Eq )

    showOpt :: Option -> String
    showOpt (FileOption pre f) = pre ++ f
    showOpt (Option s)  = s

    -----------------------------------------------------------------------------
    -- Setting the optimisation level

    updOptLevel :: Int -> DynFlags -> DynFlags
    -- ^ Sets the 'DynFlags' to be appropriate to the optimisation level
    updOptLevel n dfs
      = dfs2{ optLevel = final_n }
      where
       final_n = max 0 (min 2 n)    -- Clamp to 0 <= n <= 2
       dfs1 = foldr (flip gopt_unset) dfs  remove_gopts
       dfs2 = foldr (flip gopt_set)   dfs1 extra_gopts

       extra_gopts  = [ f | (ns,f) <- optLevelFlags, final_n `elem` ns ]
       remove_gopts = [ f | (ns,f) <- optLevelFlags, final_n `notElem` ns ]

    -- -----------------------------------------------------------------------------
    -- StgToDo:  abstraction of stg-to-stg passes to run.

    data StgToDo
      = StgDoMassageForProfiling  -- should be (next to) last
      -- There's also setStgVarInfo, but its absolute "lastness"
      -- is so critical that it is hardwired in (no flag).
      | D_stg_stats

    getStgToDo :: DynFlags -> [StgToDo]
    getStgToDo dflags
      = todo2
      where
            stg_stats = gopt Opt_StgStats dflags

            todo1 = if stg_stats then [D_stg_stats] else []

            todo2 | WayProf `elem` ways dflags
                  = StgDoMassageForProfiling : todo1
                  | otherwise
                  = todo1

    {- **********************************************************************
    %*                                                                      *
                    DynFlags parser
    %*                                                                      *
    %********************************************************************* -}

    -- -----------------------------------------------------------------------------
    -- Parsing the dynamic flags.

    -- | Parse dynamic flags from a list of command line arguments.  Returns the
    -- the parsed 'DynFlags', the left-over arguments, and a list of warnings.
    -- Throws a 'UsageError' if errors occurred during parsing (such as unknown
    -- flags or missing arguments).
    parseDynamicFlagsCmdLine :: MonadIO m => DynFlags -> [Located String]
                             -> m (DynFlags, [Located String], [Located String])
                                -- ^ Updated 'DynFlags', left-over arguments, and
                                -- list of warnings.
    parseDynamicFlagsCmdLine = parseDynamicFlagsFull flagsAll True

    -- | Like 'parseDynamicFlagsCmdLine' but does not allow the package flags
    -- (-package, -hide-package, -ignore-package, -hide-all-packages, -package-db).
    -- Used to parse flags set in a modules pragma.
    parseDynamicFilePragma :: MonadIO m => DynFlags -> [Located String]
                           -> m (DynFlags, [Located String], [Located String])
                              -- ^ Updated 'DynFlags', left-over arguments, and
                              -- list of warnings.
    parseDynamicFilePragma = parseDynamicFlagsFull flagsDynamic False

    -- | Parses the dynamically set flags for GHC. This is the most general form of
    -- the dynamic flag parser that the other methods simply wrap. It allows
    -- saying which flags are valid flags and indicating if we are parsing
    -- arguments from the command line or from a file pragma.
    parseDynamicFlagsFull :: MonadIO m
                      => [Flag (CmdLineP DynFlags)]    -- ^ valid flags to match against
                      -> Bool                          -- ^ are the arguments from the command line?
                      -> DynFlags                      -- ^ current dynamic flags
                      -> [Located String]              -- ^ arguments to parse
                      -> m (DynFlags, [Located String], [Located String])
    parseDynamicFlagsFull activeFlags cmdline dflags0 args = do
      let ((leftover, errs, warns), dflags1)
              = runCmdLine (processArgs activeFlags args) dflags0

      -- See Note [Handling errors when parsing commandline flags]
      unless (null errs) $ liftIO $ throwGhcExceptionIO $
          errorsToGhcException . map (showPpr dflags0 . getLoc &&& unLoc) $ errs

      -- check for disabled flags in safe haskell
      let (dflags2, sh_warns) = safeFlagCheck cmdline dflags1
          dflags3 = updateWays dflags2
          theWays = ways dflags3

      unless (allowed_combination theWays) $ liftIO $
          throwGhcExceptionIO (CmdLineError ("combination not supported: " ++
                                   intercalate "/" (map wayDesc theWays)))

      let chooseOutput
            | isJust (outputFile dflags3)          -- Only iff user specified -o ...
            , not (isJust (dynOutputFile dflags3)) -- but not -dyno
            = return $ dflags3 { dynOutputFile = Just $ dynOut (fromJust $ outputFile dflags3) }
            | otherwise
            = return dflags3
            where
              dynOut = flip addExtension (dynObjectSuf dflags3) . dropExtension
      dflags4 <- ifGeneratingDynamicToo dflags3 chooseOutput (return dflags3)

      let (dflags5, consistency_warnings) = makeDynFlagsConsistent dflags4

      dflags6 <- case dllSplitFile dflags5 of
                 Nothing -> return (dflags5 { dllSplit = Nothing })
                 Just f ->
                     case dllSplit dflags5 of
                     Just _ ->
                         -- If dllSplit is out of date then it would have
                         -- been set to Nothing. As it's a Just, it must be
                         -- up-to-date.
                         return dflags5
                     Nothing ->
                         do xs <- liftIO $ readFile f
                            let ss = map (Set.fromList . words) (lines xs)
                            return $ dflags5 { dllSplit = Just ss }

      -- Set timer stats & heap size
      when (enableTimeStats dflags6) $ liftIO enableTimingStats
      case (ghcHeapSize dflags6) of
        Just x -> liftIO (setHeapSize x)
        _      -> return ()

      liftIO $ setUnsafeGlobalDynFlags dflags6

      return (dflags6, leftover, consistency_warnings ++ sh_warns ++ warns)

    updateWays :: DynFlags -> DynFlags
    updateWays dflags
        = let theWays = sort $ nub $ ways dflags
              f = if WayDyn `elem` theWays then unSetGeneralFlag'
                                           else setGeneralFlag'
          in f Opt_Static
           $ dflags {
                 ways        = theWays,
                 buildTag    = mkBuildTag (filter (not . wayRTSOnly) theWays),
                 rtsBuildTag = mkBuildTag                            theWays
             }

    -- | Check (and potentially disable) any extensions that aren't allowed
    -- in safe mode.
    --
    -- The bool is to indicate if we are parsing command line flags (false means
    -- file pragma). This allows us to generate better warnings.
    safeFlagCheck :: Bool -> DynFlags -> (DynFlags, [Located String])
    safeFlagCheck _ dflags | safeLanguageOn dflags = (dflagsUnset, warns)
      where
        -- Handle illegal flags under safe language.
        (dflagsUnset, warns) = foldl check_method (dflags, []) unsafeFlags

        check_method (df, warns) (str,loc,test,fix)
            | test df   = (fix df, warns ++ safeFailure (loc df) str)
            | otherwise = (df, warns)

        safeFailure loc str
           = [L loc $ str ++ " is not allowed in Safe Haskell; ignoring "
               ++ str]

    safeFlagCheck cmdl dflags =
      case (safeInferOn dflags) of
        True | safeFlags -> (dflags', warn)
        True             -> (dflags' { safeInferred = False }, warn)
        False            -> (dflags', warn)

      where
        -- dynflags and warn for when -fpackage-trust by itself with no safe
        -- haskell flag
        (dflags', warn)
          | safeHaskell dflags == Sf_None && not cmdl && packageTrustOn dflags
          = (gopt_unset dflags Opt_PackageTrust, pkgWarnMsg)
          | otherwise = (dflags, [])

        pkgWarnMsg = [L (pkgTrustOnLoc dflags') $
                        "-fpackage-trust ignored;" ++
                        " must be specified with a Safe Haskell flag"]

        safeFlags = all (\(_,_,t,_) -> not $ t dflags) unsafeFlagsForInfer
        -- Have we inferred Unsafe?
        -- See Note [HscMain . Safe Haskell Inference]

    {- **********************************************************************
    %*                                                                      *
                    DynFlags specifications
    %*                                                                      *
    %********************************************************************* -}

    -- | All dynamic flags option strings. These are the user facing strings for
    -- enabling and disabling options.
    allFlags :: [String]
    allFlags = [ '-':flagName flag
               | flag <- flagsAll
               , ok (flagOptKind flag) ]
      where ok (PrefixPred _ _) = False
            ok _   = True

    {-
     - Below we export user facing symbols for GHC dynamic flags for use with the
     - GHC API.
     -}

    -- All dynamic flags present in GHC.
    flagsAll :: [Flag (CmdLineP DynFlags)]
    flagsAll     = package_flags ++ dynamic_flags

    -- All dynamic flags, minus package flags, present in GHC.
    flagsDynamic :: [Flag (CmdLineP DynFlags)]
    flagsDynamic = dynamic_flags

    -- ALl package flags present in GHC.
    flagsPackage :: [Flag (CmdLineP DynFlags)]
    flagsPackage = package_flags

    --------------- The main flags themselves ------------------
    -- See Note [Updating flag description in the User's Guide]
    -- See Note [Supporting CLI completion]
    dynamic_flags :: [Flag (CmdLineP DynFlags)]
    dynamic_flags = [
        defFlag "n"
          (NoArg (addWarn "The -n flag is deprecated and no longer has any effect"))
      , defFlag "cpp"      (NoArg (setExtensionFlag Opt_Cpp))
      , defFlag "F"        (NoArg (setGeneralFlag Opt_Pp))
      , defFlag "#include"
          (HasArg (\s -> do
             addCmdlineHCInclude s
             addWarn ("-#include and INCLUDE pragmas are " ++
                      "deprecated: They no longer have any effect")))
      , defFlag "v"        (OptIntSuffix setVerbosity)

      , defGhcFlag "j"     (OptIntSuffix (\n -> upd (\d -> d {parMakeCount = n})))
      , defFlag "sig-of"   (sepArg setSigOf)

        -- RTS options -------------------------------------------------------------
      , defFlag "H"           (HasArg (\s -> upd (\d ->
              d { ghcHeapSize = Just $ fromIntegral (decodeSize s)})))

      , defFlag "Rghc-timing" (NoArg (upd (\d -> d { enableTimeStats = True })))

        ------- ways ---------------------------------------------------------------
      , defGhcFlag "prof"           (NoArg (addWay WayProf))
      , defGhcFlag "eventlog"       (NoArg (addWay WayEventLog))
      , defGhcFlag "parallel"       (NoArg (addWay WayPar))
      , defGhcFlag "gransim"        (NoArg (addWay WayGran))
      , defGhcFlag "smp"
          (NoArg (addWay WayThreaded >> deprecate "Use -threaded instead"))
      , defGhcFlag "debug"          (NoArg (addWay WayDebug))
      , defGhcFlag "ndp"            (NoArg (addWay WayNDP))
      , defGhcFlag "threaded"       (NoArg (addWay WayThreaded))

      , defGhcFlag "ticky"
          (NoArg (setGeneralFlag Opt_Ticky >> addWay WayDebug))

        -- -ticky enables ticky-ticky code generation, and also implies -debug which
        -- is required to get the RTS ticky support.

            ----- Linker --------------------------------------------------------
      , defGhcFlag "static"         (NoArg removeWayDyn)
      , defGhcFlag "dynamic"        (NoArg (addWay WayDyn))
      , defGhcFlag "rdynamic" $ noArg $
    #ifdef linux_HOST_OS
                                  addOptl "-rdynamic"
    #elif defined (mingw32_HOST_OS)
                                  addOptl "-export-all-symbols"
    #else
        -- ignored for compat w/ gcc:
                                  id
    #endif
      , defGhcFlag "relative-dynlib-paths"
          (NoArg (setGeneralFlag Opt_RelativeDynlibPaths))

            ------- Specific phases  --------------------------------------------
        -- need to appear before -pgmL to be parsed as LLVM flags.
      , defFlag "pgmlo"
          (hasArg (\f -> alterSettings (\s -> s { sPgm_lo  = (f,[])})))
      , defFlag "pgmlc"
          (hasArg (\f -> alterSettings (\s -> s { sPgm_lc  = (f,[])})))
      , defFlag "pgmL"
          (hasArg (\f -> alterSettings (\s -> s { sPgm_L   = f})))
      , defFlag "pgmP"
          (hasArg setPgmP)
      , defFlag "pgmF"
          (hasArg (\f -> alterSettings (\s -> s { sPgm_F   = f})))
      , defFlag "pgmc"
          (hasArg (\f -> alterSettings (\s -> s { sPgm_c   = (f,[])})))
      , defFlag "pgms"
          (hasArg (\f -> alterSettings (\s -> s { sPgm_s   = (f,[])})))
      , defFlag "pgma"
          (hasArg (\f -> alterSettings (\s -> s { sPgm_a   = (f,[])})))
      , defFlag "pgml"
          (hasArg (\f -> alterSettings (\s -> s { sPgm_l   = (f,[])})))
      , defFlag "pgmdll"
          (hasArg (\f -> alterSettings (\s -> s { sPgm_dll = (f,[])})))
      , defFlag "pgmwindres"
          (hasArg (\f -> alterSettings (\s -> s { sPgm_windres = f})))
      , defFlag "pgmlibtool"
          (hasArg (\f -> alterSettings (\s -> s { sPgm_libtool = f})))

        -- need to appear before -optl/-opta to be parsed as LLVM flags.
      , defFlag "optlo"
          (hasArg (\f -> alterSettings (\s -> s { sOpt_lo  = f : sOpt_lo s})))
      , defFlag "optlc"
          (hasArg (\f -> alterSettings (\s -> s { sOpt_lc  = f : sOpt_lc s})))
      , defFlag "optL"
          (hasArg (\f -> alterSettings (\s -> s { sOpt_L   = f : sOpt_L s})))
      , defFlag "optP"
          (hasArg addOptP)
      , defFlag "optF"
          (hasArg (\f -> alterSettings (\s -> s { sOpt_F   = f : sOpt_F s})))
      , defFlag "optc"
          (hasArg addOptc)
      , defFlag "opta"
          (hasArg (\f -> alterSettings (\s -> s { sOpt_a   = f : sOpt_a s})))
      , defFlag "optl"
          (hasArg addOptl)
      , defFlag "optwindres"
          (hasArg (\f ->
            alterSettings (\s -> s { sOpt_windres = f : sOpt_windres s})))

      , defGhcFlag "split-objs"
          (NoArg (if can_split
                    then setGeneralFlag Opt_SplitObjs
                    else addWarn "ignoring -fsplit-objs"))

            -------- ghc -M -----------------------------------------------------
      , defGhcFlag "dep-suffix"               (hasArg addDepSuffix)
      , defGhcFlag "dep-makefile"             (hasArg setDepMakefile)
      , defGhcFlag "include-pkg-deps"         (noArg (setDepIncludePkgDeps True))
      , defGhcFlag "exclude-module"           (hasArg addDepExcludeMod)

            -------- Linking ----------------------------------------------------
      , defGhcFlag "no-link"            (noArg (\d -> d{ ghcLink=NoLink }))
      , defGhcFlag "shared"             (noArg (\d -> d{ ghcLink=LinkDynLib }))
      , defGhcFlag "staticlib"          (noArg (\d -> d{ ghcLink=LinkStaticLib }))
      , defGhcFlag "dynload"            (hasArg parseDynLibLoaderMode)
      , defGhcFlag "dylib-install-name" (hasArg setDylibInstallName)
        -- -dll-split is an internal flag, used only during the GHC build
      , defHiddenFlag "dll-split"
          (hasArg (\f d -> d{ dllSplitFile = Just f, dllSplit = Nothing }))

            ------- Libraries ---------------------------------------------------
      , defFlag "L"   (Prefix addLibraryPath)
      , defFlag "l"   (hasArg (addLdInputs . Option . ("-l" ++)))

            ------- Frameworks --------------------------------------------------
            -- -framework-path should really be -F ...
      , defFlag "framework-path" (HasArg addFrameworkPath)
      , defFlag "framework"      (hasArg addCmdlineFramework)

            ------- Output Redirection ------------------------------------------
      , defGhcFlag "odir"              (hasArg setObjectDir)
      , defGhcFlag "o"                 (sepArg (setOutputFile . Just))
      , defGhcFlag "dyno"              (sepArg (setDynOutputFile . Just))
      , defGhcFlag "ohi"               (hasArg (setOutputHi . Just ))
      , defGhcFlag "osuf"              (hasArg setObjectSuf)
      , defGhcFlag "dynosuf"           (hasArg setDynObjectSuf)
      , defGhcFlag "hcsuf"             (hasArg setHcSuf)
      , defGhcFlag "hisuf"             (hasArg setHiSuf)
      , defGhcFlag "dynhisuf"          (hasArg setDynHiSuf)
      , defGhcFlag "hidir"             (hasArg setHiDir)
      , defGhcFlag "tmpdir"            (hasArg setTmpDir)
      , defGhcFlag "stubdir"           (hasArg setStubDir)
      , defGhcFlag "dumpdir"           (hasArg setDumpDir)
      , defGhcFlag "outputdir"         (hasArg setOutputDir)
      , defGhcFlag "ddump-file-prefix" (hasArg (setDumpPrefixForce . Just))

      , defGhcFlag "dynamic-too"       (NoArg (setGeneralFlag Opt_BuildDynamicToo))

            ------- Keeping temporary files -------------------------------------
         -- These can be singular (think ghc -c) or plural (think ghc --make)
      , defGhcFlag "keep-hc-file"     (NoArg (setGeneralFlag Opt_KeepHcFiles))
      , defGhcFlag "keep-hc-files"    (NoArg (setGeneralFlag Opt_KeepHcFiles))
      , defGhcFlag "keep-s-file"      (NoArg (setGeneralFlag Opt_KeepSFiles))
      , defGhcFlag "keep-s-files"     (NoArg (setGeneralFlag Opt_KeepSFiles))
      , defGhcFlag "keep-llvm-file"   (NoArg (do setObjTarget HscLlvm
                                                 setGeneralFlag Opt_KeepLlvmFiles))
      , defGhcFlag "keep-llvm-files"  (NoArg (do setObjTarget HscLlvm
                                                 setGeneralFlag Opt_KeepLlvmFiles))
         -- This only makes sense as plural
      , defGhcFlag "keep-tmp-files"   (NoArg (setGeneralFlag Opt_KeepTmpFiles))

            ------- Miscellaneous ----------------------------------------------
      , defGhcFlag "no-auto-link-packages"
          (NoArg (unSetGeneralFlag Opt_AutoLinkPackages))
      , defGhcFlag "no-hs-main"     (NoArg (setGeneralFlag Opt_NoHsMain))
      , defGhcFlag "with-rtsopts"   (HasArg setRtsOpts)
      , defGhcFlag "rtsopts"        (NoArg (setRtsOptsEnabled RtsOptsAll))
      , defGhcFlag "rtsopts=all"    (NoArg (setRtsOptsEnabled RtsOptsAll))
      , defGhcFlag "rtsopts=some"   (NoArg (setRtsOptsEnabled RtsOptsSafeOnly))
      , defGhcFlag "rtsopts=none"   (NoArg (setRtsOptsEnabled RtsOptsNone))
      , defGhcFlag "no-rtsopts"     (NoArg (setRtsOptsEnabled RtsOptsNone))
      , defGhcFlag "main-is"        (SepArg setMainIs)
      , defGhcFlag "haddock"        (NoArg (setGeneralFlag Opt_Haddock))
      , defGhcFlag "haddock-opts"   (hasArg addHaddockOpts)
      , defGhcFlag "hpcdir"         (SepArg setOptHpcDir)
      , defGhciFlag "ghci-script"    (hasArg addGhciScript)
      , defGhciFlag "interactive-print" (hasArg setInteractivePrint)
      , defGhcFlag "ticky-allocd"      (NoArg (setGeneralFlag Opt_Ticky_Allocd))
      , defGhcFlag "ticky-LNE"         (NoArg (setGeneralFlag Opt_Ticky_LNE))
      , defGhcFlag "ticky-dyn-thunk"   (NoArg (setGeneralFlag Opt_Ticky_Dyn_Thunk))
            ------- recompilation checker --------------------------------------
      , defGhcFlag "recomp"   (NoArg (do unSetGeneralFlag Opt_ForceRecomp
                                         deprecate "Use -fno-force-recomp instead"))
      , defGhcFlag "no-recomp" (NoArg (do setGeneralFlag Opt_ForceRecomp
                                          deprecate "Use -fforce-recomp instead"))

            ------ HsCpp opts ---------------------------------------------------
      , defFlag "D"              (AnySuffix (upd . addOptP))
      , defFlag "U"              (AnySuffix (upd . addOptP))

            ------- Include/Import Paths ----------------------------------------
      , defFlag "I"              (Prefix    addIncludePath)
      , defFlag "i"              (OptPrefix addImportPath)

            ------ Output style options -----------------------------------------
      , defFlag "dppr-user-length" (intSuffix (\n d -> d{ pprUserLength = n }))
      , defFlag "dppr-cols"        (intSuffix (\n d -> d{ pprCols = n }))
      , defGhcFlag "dtrace-level"  (intSuffix (\n d -> d{ traceLevel = n }))
      -- Suppress all that is suppressable in core dumps.
      -- Except for uniques, as some simplifier phases introduce new varibles that
      -- have otherwise identical names.
      , defGhcFlag "dsuppress-all"
          (NoArg $ do setGeneralFlag Opt_SuppressCoercions
                      setGeneralFlag Opt_SuppressVarKinds
                      setGeneralFlag Opt_SuppressModulePrefixes
                      setGeneralFlag Opt_SuppressTypeApplications
                      setGeneralFlag Opt_SuppressIdInfo
                      setGeneralFlag Opt_SuppressTypeSignatures)

            ------ Debugging ----------------------------------------------------
      , defGhcFlag "dstg-stats"              (NoArg (setGeneralFlag Opt_StgStats))

      , defGhcFlag "ddump-cmm"               (setDumpFlag Opt_D_dump_cmm)
      , defGhcFlag "ddump-cmm-raw"           (setDumpFlag Opt_D_dump_cmm_raw)
      , defGhcFlag "ddump-cmm-cfg"           (setDumpFlag Opt_D_dump_cmm_cfg)
      , defGhcFlag "ddump-cmm-cbe"           (setDumpFlag Opt_D_dump_cmm_cbe)
      , defGhcFlag "ddump-cmm-proc"          (setDumpFlag Opt_D_dump_cmm_proc)
      , defGhcFlag "ddump-cmm-sink"          (setDumpFlag Opt_D_dump_cmm_sink)
      , defGhcFlag "ddump-cmm-sp"            (setDumpFlag Opt_D_dump_cmm_sp)
      , defGhcFlag "ddump-cmm-procmap"       (setDumpFlag Opt_D_dump_cmm_procmap)
      , defGhcFlag "ddump-cmm-split"         (setDumpFlag Opt_D_dump_cmm_split)
      , defGhcFlag "ddump-cmm-info"          (setDumpFlag Opt_D_dump_cmm_info)
      , defGhcFlag "ddump-cmm-cps"           (setDumpFlag Opt_D_dump_cmm_cps)
      , defGhcFlag "ddump-core-stats"        (setDumpFlag Opt_D_dump_core_stats)
      , defGhcFlag "ddump-asm"               (setDumpFlag Opt_D_dump_asm)
      , defGhcFlag "ddump-asm-native"        (setDumpFlag Opt_D_dump_asm_native)
      , defGhcFlag "ddump-asm-liveness"      (setDumpFlag Opt_D_dump_asm_liveness)
      , defGhcFlag "ddump-asm-regalloc"      (setDumpFlag Opt_D_dump_asm_regalloc)
      , defGhcFlag "ddump-asm-conflicts"     (setDumpFlag Opt_D_dump_asm_conflicts)
      , defGhcFlag "ddump-asm-regalloc-stages"
          (setDumpFlag Opt_D_dump_asm_regalloc_stages)
      , defGhcFlag "ddump-asm-stats"         (setDumpFlag Opt_D_dump_asm_stats)
      , defGhcFlag "ddump-asm-expanded"      (setDumpFlag Opt_D_dump_asm_expanded)
      , defGhcFlag "ddump-llvm"            (NoArg (do setObjTarget HscLlvm
                                                      setDumpFlag' Opt_D_dump_llvm))
      , defGhcFlag "ddump-deriv"             (setDumpFlag Opt_D_dump_deriv)
      , defGhcFlag "ddump-ds"                (setDumpFlag Opt_D_dump_ds)
      , defGhcFlag "ddump-foreign"           (setDumpFlag Opt_D_dump_foreign)
      , defGhcFlag "ddump-inlinings"         (setDumpFlag Opt_D_dump_inlinings)
      , defGhcFlag "ddump-rule-firings"      (setDumpFlag Opt_D_dump_rule_firings)
      , defGhcFlag "ddump-rule-rewrites"     (setDumpFlag Opt_D_dump_rule_rewrites)
      , defGhcFlag "ddump-simpl-trace"       (setDumpFlag Opt_D_dump_simpl_trace)
      , defGhcFlag "ddump-occur-anal"        (setDumpFlag Opt_D_dump_occur_anal)
      , defGhcFlag "ddump-parsed"            (setDumpFlag Opt_D_dump_parsed)
      , defGhcFlag "ddump-rn"                (setDumpFlag Opt_D_dump_rn)
      , defGhcFlag "ddump-simpl"             (setDumpFlag Opt_D_dump_simpl)
      , defGhcFlag "ddump-simpl-iterations"
          (setDumpFlag Opt_D_dump_simpl_iterations)
      , defGhcFlag "ddump-spec"              (setDumpFlag Opt_D_dump_spec)
      , defGhcFlag "ddump-prep"              (setDumpFlag Opt_D_dump_prep)
      , defGhcFlag "ddump-stg"               (setDumpFlag Opt_D_dump_stg)
      , defGhcFlag "ddump-call-arity"        (setDumpFlag Opt_D_dump_call_arity)
      , defGhcFlag "ddump-stranal"           (setDumpFlag Opt_D_dump_stranal)
      , defGhcFlag "ddump-strsigs"           (setDumpFlag Opt_D_dump_strsigs)
      , defGhcFlag "ddump-tc"                (setDumpFlag Opt_D_dump_tc)
      , defGhcFlag "ddump-types"             (setDumpFlag Opt_D_dump_types)
      , defGhcFlag "ddump-rules"             (setDumpFlag Opt_D_dump_rules)
      , defGhcFlag "ddump-cse"               (setDumpFlag Opt_D_dump_cse)
      , defGhcFlag "ddump-worker-wrapper"    (setDumpFlag Opt_D_dump_worker_wrapper)
      , defGhcFlag "ddump-rn-trace"          (setDumpFlag Opt_D_dump_rn_trace)
      , defGhcFlag "ddump-if-trace"          (setDumpFlag Opt_D_dump_if_trace)
      , defGhcFlag "ddump-cs-trace"          (setDumpFlag Opt_D_dump_cs_trace)
      , defGhcFlag "ddump-tc-trace"          (NoArg (do
                                                setDumpFlag' Opt_D_dump_tc_trace
                                                setDumpFlag' Opt_D_dump_cs_trace))
      , defGhcFlag "ddump-vt-trace"          (setDumpFlag Opt_D_dump_vt_trace)
      , defGhcFlag "ddump-splices"           (setDumpFlag Opt_D_dump_splices)
      , defGhcFlag "dth-dec-file"            (setDumpFlag Opt_D_th_dec_file)

      , defGhcFlag "ddump-rn-stats"          (setDumpFlag Opt_D_dump_rn_stats)
      , defGhcFlag "ddump-opt-cmm"           (setDumpFlag Opt_D_dump_opt_cmm)
      , defGhcFlag "ddump-simpl-stats"       (setDumpFlag Opt_D_dump_simpl_stats)
      , defGhcFlag "ddump-bcos"              (setDumpFlag Opt_D_dump_BCOs)
      , defGhcFlag "dsource-stats"           (setDumpFlag Opt_D_source_stats)
      , defGhcFlag "dverbose-core2core"      (NoArg (do setVerbosity (Just 2)
                                                        setVerboseCore2Core))
      , defGhcFlag "dverbose-stg2stg"        (setDumpFlag Opt_D_verbose_stg2stg)
      , defGhcFlag "ddump-hi"                (setDumpFlag Opt_D_dump_hi)
      , defGhcFlag "ddump-minimal-imports"
          (NoArg (setGeneralFlag Opt_D_dump_minimal_imports))
      , defGhcFlag "ddump-vect"              (setDumpFlag Opt_D_dump_vect)
      , defGhcFlag "ddump-hpc"
          (setDumpFlag Opt_D_dump_ticked) -- back compat
      , defGhcFlag "ddump-ticked"            (setDumpFlag Opt_D_dump_ticked)
      , defGhcFlag "ddump-mod-cycles"        (setDumpFlag Opt_D_dump_mod_cycles)
      , defGhcFlag "ddump-mod-map"           (setDumpFlag Opt_D_dump_mod_map)
      , defGhcFlag "ddump-view-pattern-commoning"
          (setDumpFlag Opt_D_dump_view_pattern_commoning)
      , defGhcFlag "ddump-to-file"           (NoArg (setGeneralFlag Opt_DumpToFile))
      , defGhcFlag "ddump-hi-diffs"          (setDumpFlag Opt_D_dump_hi_diffs)
      , defGhcFlag "ddump-rtti"              (setDumpFlag Opt_D_dump_rtti)
      , defGhcFlag "dcore-lint"
          (NoArg (setGeneralFlag Opt_DoCoreLinting))
      , defGhcFlag "dstg-lint"
          (NoArg (setGeneralFlag Opt_DoStgLinting))
      , defGhcFlag "dcmm-lint"
          (NoArg (setGeneralFlag Opt_DoCmmLinting))
      , defGhcFlag "dasm-lint"
          (NoArg (setGeneralFlag Opt_DoAsmLinting))
      , defGhcFlag "dannot-lint"
          (NoArg (setGeneralFlag Opt_DoAnnotationLinting))
      , defGhcFlag "dshow-passes"            (NoArg (do forceRecompile
                                                        setVerbosity $ Just 2))
      , defGhcFlag "dfaststring-stats"
          (NoArg (setGeneralFlag Opt_D_faststring_stats))
      , defGhcFlag "dno-llvm-mangler"
          (NoArg (setGeneralFlag Opt_NoLlvmMangler)) -- hidden flag
      , defGhcFlag "ddump-debug"             (setDumpFlag Opt_D_dump_debug)

            ------ Machine dependant (-m<blah>) stuff ---------------------------

      , defGhcFlag "msse"         (noArg (\d -> d{ sseVersion = Just SSE1 }))
      , defGhcFlag "msse2"        (noArg (\d -> d{ sseVersion = Just SSE2 }))
      , defGhcFlag "msse3"        (noArg (\d -> d{ sseVersion = Just SSE3 }))
      , defGhcFlag "msse4"        (noArg (\d -> d{ sseVersion = Just SSE4 }))
      , defGhcFlag "msse4.2"      (noArg (\d -> d{ sseVersion = Just SSE42 }))
      , defGhcFlag "mavx"         (noArg (\d -> d{ avx = True }))
      , defGhcFlag "mavx2"        (noArg (\d -> d{ avx2 = True }))
      , defGhcFlag "mavx512cd"    (noArg (\d -> d{ avx512cd = True }))
      , defGhcFlag "mavx512er"    (noArg (\d -> d{ avx512er = True }))
      , defGhcFlag "mavx512f"     (noArg (\d -> d{ avx512f = True }))
      , defGhcFlag "mavx512pf"    (noArg (\d -> d{ avx512pf = True }))

         ------ Warning opts -------------------------------------------------
      , defFlag "W"      (NoArg (mapM_ setWarningFlag minusWOpts))
      , defFlag "Werror" (NoArg (setGeneralFlag           Opt_WarnIsError))
      , defFlag "Wwarn"  (NoArg (unSetGeneralFlag         Opt_WarnIsError))
      , defFlag "Wall"   (NoArg (mapM_ setWarningFlag minusWallOpts))
      , defFlag "Wnot"   (NoArg (do upd (\dfs -> dfs {warningFlags = IntSet.empty})
                                    deprecate "Use -w instead"))
      , defFlag "w"      (NoArg (upd (\dfs -> dfs {warningFlags = IntSet.empty})))

            ------ Plugin flags ------------------------------------------------
      , defGhcFlag "fplugin-opt" (hasArg addPluginModuleNameOption)
      , defGhcFlag "fplugin"     (hasArg addPluginModuleName)

            ------ Optimisation flags ------------------------------------------
      , defGhcFlag "O"      (noArgM (setOptLevel 1))
      , defGhcFlag "Onot"   (noArgM (\dflags -> do deprecate "Use -O0 instead"
                                                   setOptLevel 0 dflags))
      , defGhcFlag "Odph"   (noArgM setDPHOpt)
      , defGhcFlag "O"      (optIntSuffixM (\mb_n -> setOptLevel (mb_n `orElse` 1)))
                    -- If the number is missing, use 1

      , defFlag "fmax-relevant-binds"
          (intSuffix (\n d -> d{ maxRelevantBinds = Just n }))
      , defFlag "fno-max-relevant-binds"
          (noArg (\d -> d{ maxRelevantBinds = Nothing }))
      , defFlag "fsimplifier-phases"
          (intSuffix (\n d -> d{ simplPhases = n }))
      , defFlag "fmax-simplifier-iterations"
          (intSuffix (\n d -> d{ maxSimplIterations = n }))
      , defFlag "fsimpl-tick-factor"
          (intSuffix (\n d -> d{ simplTickFactor = n }))
      , defFlag "fspec-constr-threshold"
          (intSuffix (\n d -> d{ specConstrThreshold = Just n }))
      , defFlag "fno-spec-constr-threshold"
          (noArg (\d -> d{ specConstrThreshold = Nothing }))
      , defFlag "fspec-constr-count"
          (intSuffix (\n d -> d{ specConstrCount = Just n }))
      , defFlag "fno-spec-constr-count"
          (noArg (\d -> d{ specConstrCount = Nothing }))
      , defFlag "fspec-constr-recursive"
          (intSuffix (\n d -> d{ specConstrRecursive = n }))
      , defFlag "fliberate-case-threshold"
          (intSuffix (\n d -> d{ liberateCaseThreshold = Just n }))
      , defFlag "fno-liberate-case-threshold"
          (noArg (\d -> d{ liberateCaseThreshold = Nothing }))
      , defFlag "frule-check"
          (sepArg (\s d -> d{ ruleCheck = Just s }))
      , defFlag "fcontext-stack"
          (intSuffix (\n d -> d{ ctxtStkDepth = n }))
      , defFlag "ftype-function-depth"
          (intSuffix (\n d -> d{ tyFunStkDepth = n }))
      , defFlag "fstrictness-before"
          (intSuffix (\n d -> d{ strictnessBefore = n : strictnessBefore d }))
      , defFlag "ffloat-lam-args"
          (intSuffix (\n d -> d{ floatLamArgs = Just n }))
      , defFlag "ffloat-all-lams"
          (noArg (\d -> d{ floatLamArgs = Nothing }))

      , defFlag "fhistory-size"           (intSuffix (\n d -> d{ historySize = n }))

      , defFlag "funfolding-creation-threshold"
          (intSuffix   (\n d -> d {ufCreationThreshold = n}))
      , defFlag "funfolding-use-threshold"
          (intSuffix   (\n d -> d {ufUseThreshold = n}))
      , defFlag "funfolding-fun-discount"
          (intSuffix   (\n d -> d {ufFunAppDiscount = n}))
      , defFlag "funfolding-dict-discount"
          (intSuffix   (\n d -> d {ufDictDiscount = n}))
      , defFlag "funfolding-keeness-factor"
          (floatSuffix (\n d -> d {ufKeenessFactor = n}))

      , defFlag "fmax-worker-args" (intSuffix (\n d -> d {maxWorkerArgs = n}))

      , defGhciFlag "fghci-hist-size" (intSuffix (\n d -> d {ghciHistSize = n}))
      , defGhcFlag "fmax-inline-alloc-size"
          (intSuffix (\n d -> d{ maxInlineAllocSize = n }))
      , defGhcFlag "fmax-inline-memcpy-insns"
          (intSuffix (\n d -> d{ maxInlineMemcpyInsns = n }))
      , defGhcFlag "fmax-inline-memset-insns"
          (intSuffix (\n d -> d{ maxInlineMemsetInsns = n }))

            ------ Profiling ----------------------------------------------------

            -- OLD profiling flags
      , defGhcFlag "auto-all"    (noArg (\d -> d { profAuto = ProfAutoAll } ))
      , defGhcFlag "no-auto-all" (noArg (\d -> d { profAuto = NoProfAuto } ))
      , defGhcFlag "auto"        (noArg (\d -> d { profAuto = ProfAutoExports } ))
      , defGhcFlag "no-auto"     (noArg (\d -> d { profAuto = NoProfAuto } ))
      , defGhcFlag "caf-all"
          (NoArg (setGeneralFlag Opt_AutoSccsOnIndividualCafs))
      , defGhcFlag "no-caf-all"
          (NoArg (unSetGeneralFlag Opt_AutoSccsOnIndividualCafs))

            -- NEW profiling flags
      , defGhcFlag "fprof-auto"
          (noArg (\d -> d { profAuto = ProfAutoAll } ))
      , defGhcFlag "fprof-auto-top"
          (noArg (\d -> d { profAuto = ProfAutoTop } ))
      , defGhcFlag "fprof-auto-exported"
          (noArg (\d -> d { profAuto = ProfAutoExports } ))
      , defGhcFlag "fprof-auto-calls"
          (noArg (\d -> d { profAuto = ProfAutoCalls } ))
      , defGhcFlag "fno-prof-auto"
          (noArg (\d -> d { profAuto = NoProfAuto } ))

            ------ Compiler flags -----------------------------------------------

      , defGhcFlag "fasm"             (NoArg (setObjTarget HscAsm))
      , defGhcFlag "fvia-c"           (NoArg
             (addWarn $ "The -fvia-c flag does nothing; " ++
                        "it will be removed in a future GHC release"))
      , defGhcFlag "fvia-C"           (NoArg
             (addWarn $ "The -fvia-C flag does nothing; " ++
                        "it will be removed in a future GHC release"))
      , defGhcFlag "fllvm"            (NoArg (setObjTarget HscLlvm))

      , defFlag "fno-code"         (NoArg (do upd $ \d -> d{ ghcLink=NoLink }
                                              setTarget HscNothing))
      , defFlag "fbyte-code"       (NoArg (setTarget HscInterpreted))
      , defFlag "fobject-code"     (NoArg (setTargetWithPlatform defaultHscTarget))
      , defFlag "fglasgow-exts"
          (NoArg (do enableGlasgowExts
                     deprecate "Use individual extensions instead"))
      , defFlag "fno-glasgow-exts"
          (NoArg (do disableGlasgowExts
                     deprecate "Use individual extensions instead"))

            ------ Safe Haskell flags -------------------------------------------
      , defFlag "fpackage-trust"   (NoArg setPackageTrust)
      , defFlag "fno-safe-infer"   (noArg (\d -> d { safeInfer = False  } ))
      , defGhcFlag "fPIC"          (NoArg (setGeneralFlag Opt_PIC))
      , defGhcFlag "fno-PIC"       (NoArg (unSetGeneralFlag Opt_PIC))

             ------ Debugging flags ----------------------------------------------
      , defGhcFlag "g"             (NoArg (setGeneralFlag Opt_Debug))
     ]
     ++ map (mkFlag turnOn  ""     setGeneralFlag  ) negatableFlags
     ++ map (mkFlag turnOff "no-"  unSetGeneralFlag) negatableFlags
     ++ map (mkFlag turnOn  "d"    setGeneralFlag  ) dFlags
     ++ map (mkFlag turnOff "dno-" unSetGeneralFlag) dFlags
     ++ map (mkFlag turnOn  "f"    setGeneralFlag  ) fFlags
     ++ map (mkFlag turnOff "fno-" unSetGeneralFlag) fFlags
     ++ map (mkFlag turnOn  "f"    setWarningFlag  ) fWarningFlags
     ++ map (mkFlag turnOff "fno-" unSetWarningFlag) fWarningFlags
     ++ map (mkFlag turnOn  "f"    setExtensionFlag  ) fLangFlags
     ++ map (mkFlag turnOff "fno-" unSetExtensionFlag) fLangFlags
     ++ map (mkFlag turnOn  "X"    setExtensionFlag  ) xFlags
     ++ map (mkFlag turnOff "XNo"  unSetExtensionFlag) xFlags
     ++ map (mkFlag turnOn  "X"    setLanguage) languageFlags
     ++ map (mkFlag turnOn  "X"    setSafeHaskell) safeHaskellFlags
     ++ [ defFlag "XGenerics"
            (NoArg (deprecate $
                      "it does nothing; look into -XDefaultSignatures " ++
                      "and -XDeriveGeneric for generic programming support."))
        , defFlag "XNoGenerics"
            (NoArg (deprecate $
                      "it does nothing; look into -XDefaultSignatures and " ++
                      "-XDeriveGeneric for generic programming support.")) ]

    -- See Note [Supporting CLI completion]
    package_flags :: [Flag (CmdLineP DynFlags)]
    package_flags = [
            ------- Packages ----------------------------------------------------
        defFlag "package-db"            (HasArg (addPkgConfRef . PkgConfFile))
      , defFlag "clear-package-db"      (NoArg clearPkgConf)
      , defFlag "no-global-package-db"  (NoArg removeGlobalPkgConf)
      , defFlag "no-user-package-db"    (NoArg removeUserPkgConf)
      , defFlag "global-package-db"     (NoArg (addPkgConfRef GlobalPkgConf))
      , defFlag "user-package-db"       (NoArg (addPkgConfRef UserPkgConf))

        -- backwards compat with GHC<=7.4 :
      , defFlag "package-conf"          (HasArg $ \path -> do
                                           addPkgConfRef (PkgConfFile path)
                                           deprecate "Use -package-db instead")
      , defFlag "no-user-package-conf"
          (NoArg $ do removeUserPkgConf
                      deprecate "Use -no-user-package-db instead")

      , defGhcFlag "package-name"       (hasArg setPackageKey)
      , defGhcFlag "this-package-key"   (hasArg setPackageKey)
      , defFlag "package-id"            (HasArg exposePackageId)
      , defFlag "package"               (HasArg exposePackage)
      , defFlag "package-key"           (HasArg exposePackageKey)
      , defFlag "hide-package"          (HasArg hidePackage)
      , defFlag "hide-all-packages"     (NoArg (setGeneralFlag Opt_HideAllPackages))
      , defFlag "package-env"           (HasArg setPackageEnv)
      , defFlag "ignore-package"        (HasArg ignorePackage)
      , defFlag "syslib"
          (HasArg (\s -> do exposePackage s
                            deprecate "Use -package instead"))
      , defFlag "distrust-all-packages"
          (NoArg (setGeneralFlag Opt_DistrustAllPackages))
      , defFlag "trust"                 (HasArg trustPackage)
      , defFlag "distrust"              (HasArg distrustPackage)
      ]
      where
        setPackageEnv env = upd $ \s -> s { packageEnv = Just env }

    -- | Make a list of flags for shell completion.
    -- Filter all available flags into two groups, for interactive GHC vs all other.
    flagsForCompletion :: Bool -> [String]
    flagsForCompletion isInteractive
        = [ '-':flagName flag
          | flag <- flagsAll
          , modeFilter (flagGhcMode flag)
          ]
        where
          modeFilter AllModes = True
          modeFilter OnlyGhci = isInteractive
          modeFilter OnlyGhc = not isInteractive
          modeFilter HiddenFlag = False

    type TurnOnFlag = Bool   -- True  <=> we are turning the flag on
                             -- False <=> we are turning the flag off
    turnOn  :: TurnOnFlag; turnOn  = True
    turnOff :: TurnOnFlag; turnOff = False

    data FlagSpec flag
       = FlagSpec
           { flagSpecName :: String   -- ^ Flag in string form
           , flagSpecFlag :: flag     -- ^ Flag in internal form
           , flagSpecAction :: (TurnOnFlag -> DynP ())
               -- ^ Extra action to run when the flag is found
               -- Typically, emit a warning or error
           , flagSpecGhcMode :: GhcFlagMode
               -- ^ In which ghc mode the flag has effect
           }

    -- | Define a new flag.
    flagSpec :: String -> flag -> FlagSpec flag
    flagSpec name flag = flagSpec' name flag nop

    -- | Define a new flag with an effect.
    flagSpec' :: String -> flag -> (TurnOnFlag -> DynP ()) -> FlagSpec flag
    flagSpec' name flag act = FlagSpec name flag act AllModes

    -- | Define a new flag for GHCi.
    flagGhciSpec :: String -> flag -> FlagSpec flag
    flagGhciSpec name flag = flagGhciSpec' name flag nop

    -- | Define a new flag for GHCi with an effect.
    flagGhciSpec' :: String -> flag -> (TurnOnFlag -> DynP ()) -> FlagSpec flag
    flagGhciSpec' name flag act = FlagSpec name flag act OnlyGhci

    -- | Define a new flag invisible to CLI completion.
    flagHiddenSpec :: String -> flag -> FlagSpec flag
    flagHiddenSpec name flag = flagHiddenSpec' name flag nop

    -- | Define a new flag invisible to CLI completion with an effect.
    flagHiddenSpec' :: String -> flag -> (TurnOnFlag -> DynP ()) -> FlagSpec flag
    flagHiddenSpec' name flag act = FlagSpec name flag act HiddenFlag

    mkFlag :: TurnOnFlag            -- ^ True <=> it should be turned on
           -> String                -- ^ The flag prefix
           -> (flag -> DynP ())     -- ^ What to do when the flag is found
           -> FlagSpec flag         -- ^ Specification of this particular flag
           -> Flag (CmdLineP DynFlags)
    mkFlag turn_on flagPrefix f (FlagSpec name flag extra_action mode)
        = Flag (flagPrefix ++ name) (NoArg (f flag >> extra_action turn_on)) mode

    deprecatedForExtension :: String -> TurnOnFlag -> DynP ()
    deprecatedForExtension lang turn_on
        = deprecate ("use -X"  ++ flag ++
                     " or pragma {-# LANGUAGE " ++ flag ++ " #-} instead")
        where
          flag | turn_on    = lang
               | otherwise = "No"++lang

    useInstead :: String -> TurnOnFlag -> DynP ()
    useInstead flag turn_on
      = deprecate ("Use -f" ++ no ++ flag ++ " instead")
      where
        no = if turn_on then "" else "no-"

    nop :: TurnOnFlag -> DynP ()
    nop _ = return ()

    -- | These @-f\<blah\>@ flags can all be reversed with @-fno-\<blah\>@
    fWarningFlags :: [FlagSpec WarningFlag]
    fWarningFlags = [
    -- See Note [Updating flag description in the User's Guide]
    -- See Note [Supporting CLI completion]
    -- Please keep the list of flags below sorted alphabetically
      flagSpec "warn-alternative-layout-rule-transitional"
                                          Opt_WarnAlternativeLayoutRuleTransitional,
      flagSpec' "warn-amp"                        Opt_WarnAMP
        (\_ -> deprecate "it has no effect, and will be removed in GHC 7.12"),
      flagSpec "warn-auto-orphans"                Opt_WarnAutoOrphans,
      flagSpec "warn-deprecations"                Opt_WarnWarningsDeprecations,
      flagSpec "warn-deprecated-flags"            Opt_WarnDeprecatedFlags,
      flagSpec "warn-deriving-typeable"           Opt_WarnDerivingTypeable,
      flagSpec "warn-dodgy-exports"               Opt_WarnDodgyExports,
      flagSpec "warn-dodgy-foreign-imports"       Opt_WarnDodgyForeignImports,
      flagSpec "warn-dodgy-imports"               Opt_WarnDodgyImports,
      flagSpec "warn-empty-enumerations"          Opt_WarnEmptyEnumerations,
      flagSpec "warn-context-quantification"      Opt_WarnContextQuantification,
      flagSpec "warn-duplicate-constraints"       Opt_WarnDuplicateConstraints,
      flagSpec "warn-duplicate-exports"           Opt_WarnDuplicateExports,
      flagSpec "warn-hi-shadowing"                Opt_WarnHiShadows,
      flagSpec "warn-implicit-prelude"            Opt_WarnImplicitPrelude,
      flagSpec "warn-incomplete-patterns"         Opt_WarnIncompletePatterns,
      flagSpec "warn-incomplete-record-updates"   Opt_WarnIncompletePatternsRecUpd,
      flagSpec "warn-incomplete-uni-patterns"     Opt_WarnIncompleteUniPatterns,
      flagSpec "warn-inline-rule-shadowing"       Opt_WarnInlineRuleShadowing,
      flagSpec "warn-identities"                  Opt_WarnIdentities,
      flagSpec "warn-missing-fields"              Opt_WarnMissingFields,
      flagSpec "warn-missing-import-lists"        Opt_WarnMissingImportList,
      flagSpec "warn-missing-local-sigs"          Opt_WarnMissingLocalSigs,
      flagSpec "warn-missing-methods"             Opt_WarnMissingMethods,
      flagSpec "warn-missing-signatures"          Opt_WarnMissingSigs,
      flagSpec "warn-missing-exported-sigs"       Opt_WarnMissingExportedSigs,
      flagSpec "warn-monomorphism-restriction"    Opt_WarnMonomorphism,
      flagSpec "warn-name-shadowing"              Opt_WarnNameShadowing,
      flagSpec "warn-orphans"                     Opt_WarnOrphans,
      flagSpec "warn-overflowed-literals"         Opt_WarnOverflowedLiterals,
      flagSpec "warn-overlapping-patterns"        Opt_WarnOverlappingPatterns,
      flagSpec "warn-pointless-pragmas"           Opt_WarnPointlessPragmas,
      flagSpec' "warn-safe"                       Opt_WarnSafe setWarnSafe,
      flagSpec "warn-trustworthy-safe"            Opt_WarnTrustworthySafe,
      flagSpec "warn-tabs"                        Opt_WarnTabs,
      flagSpec "warn-type-defaults"               Opt_WarnTypeDefaults,
      flagSpec "warn-typed-holes"                 Opt_WarnTypedHoles,
      flagSpec "warn-partial-type-signatures"     Opt_WarnPartialTypeSignatures,
      flagSpec "warn-unrecognised-pragmas"        Opt_WarnUnrecognisedPragmas,
      flagSpec' "warn-unsafe"                     Opt_WarnUnsafe setWarnUnsafe,
      flagSpec "warn-unsupported-calling-conventions"
                                             Opt_WarnUnsupportedCallingConventions,
      flagSpec "warn-unsupported-llvm-version"    Opt_WarnUnsupportedLlvmVersion,
      flagSpec "warn-unticked-promoted-constructors"
                                             Opt_WarnUntickedPromotedConstructors,
      flagSpec "warn-unused-binds"                Opt_WarnUnusedBinds,
      flagSpec "warn-unused-do-bind"              Opt_WarnUnusedDoBind,
      flagSpec "warn-unused-imports"              Opt_WarnUnusedImports,
      flagSpec "warn-unused-matches"              Opt_WarnUnusedMatches,
      flagSpec "warn-warnings-deprecations"       Opt_WarnWarningsDeprecations,
      flagSpec "warn-wrong-do-bind"               Opt_WarnWrongDoBind]

    -- | These @-\<blah\>@ flags can all be reversed with @-no-\<blah\>@
    negatableFlags :: [FlagSpec GeneralFlag]
    negatableFlags = [
      flagGhciSpec "ignore-dot-ghci"              Opt_IgnoreDotGhci ]

    -- | These @-d\<blah\>@ flags can all be reversed with @-dno-\<blah\>@
    dFlags :: [FlagSpec GeneralFlag]
    dFlags = [
    -- See Note [Updating flag description in the User's Guide]
    -- See Note [Supporting CLI completion]
    -- Please keep the list of flags below sorted alphabetically
      flagSpec "ppr-case-as-let"            Opt_PprCaseAsLet,
      flagSpec "ppr-ticks"                  Opt_PprShowTicks,
      flagSpec "suppress-coercions"         Opt_SuppressCoercions,
      flagSpec "suppress-idinfo"            Opt_SuppressIdInfo,
      flagSpec "suppress-module-prefixes"   Opt_SuppressModulePrefixes,
      flagSpec "suppress-type-applications" Opt_SuppressTypeApplications,
      flagSpec "suppress-type-signatures"   Opt_SuppressTypeSignatures,
      flagSpec "suppress-uniques"           Opt_SuppressUniques,
      flagSpec "suppress-var-kinds"         Opt_SuppressVarKinds]

    -- | These @-f\<blah\>@ flags can all be reversed with @-fno-\<blah\>@
    fFlags :: [FlagSpec GeneralFlag]
    fFlags = [
    -- See Note [Updating flag description in the User's Guide]
    -- See Note [Supporting CLI completion]
    -- Please keep the list of flags below sorted alphabetically
      flagGhciSpec "break-on-error"               Opt_BreakOnError,
      flagGhciSpec "break-on-exception"           Opt_BreakOnException,
      flagSpec "building-cabal-package"           Opt_BuildingCabalPackage,
      flagSpec "call-arity"                       Opt_CallArity,
      flagSpec "case-merge"                       Opt_CaseMerge,
      flagSpec "cmm-elim-common-blocks"           Opt_CmmElimCommonBlocks,
      flagSpec "cmm-sink"                         Opt_CmmSink,
      flagSpec "cse"                              Opt_CSE,
      flagSpec "defer-type-errors"                Opt_DeferTypeErrors,
      flagSpec "defer-typed-holes"                Opt_DeferTypedHoles,
      flagSpec "dicts-cheap"                      Opt_DictsCheap,
      flagSpec "dicts-strict"                     Opt_DictsStrict,
      flagSpec "dmd-tx-dict-sel"                  Opt_DmdTxDictSel,
      flagSpec "do-eta-reduction"                 Opt_DoEtaReduction,
      flagSpec "do-lambda-eta-expansion"          Opt_DoLambdaEtaExpansion,
      flagSpec "eager-blackholing"                Opt_EagerBlackHoling,
      flagSpec "embed-manifest"                   Opt_EmbedManifest,
      flagSpec "enable-rewrite-rules"             Opt_EnableRewriteRules,
      flagSpec "error-spans"                      Opt_ErrorSpans,
      flagSpec "excess-precision"                 Opt_ExcessPrecision,
      flagSpec "expose-all-unfoldings"            Opt_ExposeAllUnfoldings,
      flagSpec' "ext-core"                        Opt_EmitExternalCore
        (\_ -> deprecate "it has no effect, and will be removed in GHC 7.12"),
      flagSpec "flat-cache"                       Opt_FlatCache,
      flagSpec "float-in"                         Opt_FloatIn,
      flagSpec "force-recomp"                     Opt_ForceRecomp,
      flagSpec "full-laziness"                    Opt_FullLaziness,
      flagSpec "fun-to-thunk"                     Opt_FunToThunk,
      flagSpec "gen-manifest"                     Opt_GenManifest,
      flagSpec "ghci-history"                     Opt_GhciHistory,
      flagSpec "ghci-sandbox"                     Opt_GhciSandbox,
      flagSpec "helpful-errors"                   Opt_HelpfulErrors,
      flagSpec "hpc"                              Opt_Hpc,
      flagSpec "hpc-no-auto"                      Opt_Hpc_No_Auto,
      flagSpec "ignore-asserts"                   Opt_IgnoreAsserts,
      flagSpec "ignore-interface-pragmas"         Opt_IgnoreInterfacePragmas,
      flagGhciSpec "implicit-import-qualified"    Opt_ImplicitImportQualified,
      flagSpec "irrefutable-tuples"               Opt_IrrefutableTuples,
      flagSpec "kill-absence"                     Opt_KillAbsence,
      flagSpec "kill-one-shot"                    Opt_KillOneShot,
      flagSpec "late-dmd-anal"                    Opt_LateDmdAnal,
      flagSpec "liberate-case"                    Opt_LiberateCase,
      flagHiddenSpec "llvm-pass-vectors-in-regs"  Opt_LlvmPassVectorsInRegisters,
      flagHiddenSpec "llvm-tbaa"                  Opt_LlvmTBAA,
      flagSpec "loopification"                    Opt_Loopification,
      flagSpec "omit-interface-pragmas"           Opt_OmitInterfacePragmas,
      flagSpec "omit-yields"                      Opt_OmitYields,
      flagSpec "pedantic-bottoms"                 Opt_PedanticBottoms,
      flagSpec "pre-inlining"                     Opt_SimplPreInlining,
      flagGhciSpec "print-bind-contents"          Opt_PrintBindContents,
      flagGhciSpec "print-bind-result"            Opt_PrintBindResult,
      flagGhciSpec "print-evld-with-show"         Opt_PrintEvldWithShow,
      flagSpec "print-explicit-foralls"           Opt_PrintExplicitForalls,
      flagSpec "print-explicit-kinds"             Opt_PrintExplicitKinds,
      flagSpec "prof-cafs"                        Opt_AutoSccsOnIndividualCafs,
      flagSpec "prof-count-entries"               Opt_ProfCountEntries,
      flagSpec "regs-graph"                       Opt_RegsGraph,
      flagSpec "regs-iterative"                   Opt_RegsIterative,
      flagSpec' "rewrite-rules"                   Opt_EnableRewriteRules
        (useInstead "enable-rewrite-rules"),
      flagSpec "shared-implib"                    Opt_SharedImplib,
      flagSpec "simple-list-literals"             Opt_SimpleListLiterals,
      flagSpec "spec-constr"                      Opt_SpecConstr,
      flagSpec "specialise"                       Opt_Specialise,
      flagSpec "specialise-aggressively"          Opt_SpecialiseAggressively,
      flagSpec "static-argument-transformation"   Opt_StaticArgumentTransformation,
      flagSpec "strictness"                       Opt_Strictness,
      flagSpec "use-rpaths"                       Opt_RPath,
      flagSpec "write-interface"                  Opt_WriteInterface,
      flagSpec "unbox-small-strict-fields"        Opt_UnboxSmallStrictFields,
      flagSpec "unbox-strict-fields"              Opt_UnboxStrictFields,
      flagSpec "vectorisation-avoidance"          Opt_VectorisationAvoidance,
      flagSpec "vectorise"                        Opt_Vectorise
      ]

    -- | These @-f\<blah\>@ flags can all be reversed with @-fno-\<blah\>@
    fLangFlags :: [FlagSpec ExtensionFlag]
    fLangFlags = [
    -- See Note [Updating flag description in the User's Guide]
    -- See Note [Supporting CLI completion]
      flagSpec' "th"                              Opt_TemplateHaskell
        (\on -> deprecatedForExtension "TemplateHaskell" on
             >> checkTemplateHaskellOk on),
      flagSpec' "fi"                              Opt_ForeignFunctionInterface
        (deprecatedForExtension "ForeignFunctionInterface"),
      flagSpec' "ffi"                             Opt_ForeignFunctionInterface
        (deprecatedForExtension "ForeignFunctionInterface"),
      flagSpec' "arrows"                          Opt_Arrows
        (deprecatedForExtension "Arrows"),
      flagSpec' "implicit-prelude"                Opt_ImplicitPrelude
        (deprecatedForExtension "ImplicitPrelude"),
      flagSpec' "bang-patterns"                   Opt_BangPatterns
        (deprecatedForExtension "BangPatterns"),
      flagSpec' "monomorphism-restriction"        Opt_MonomorphismRestriction
        (deprecatedForExtension "MonomorphismRestriction"),
      flagSpec' "mono-pat-binds"                  Opt_MonoPatBinds
        (deprecatedForExtension "MonoPatBinds"),
      flagSpec' "extended-default-rules"          Opt_ExtendedDefaultRules
        (deprecatedForExtension "ExtendedDefaultRules"),
      flagSpec' "implicit-params"                 Opt_ImplicitParams
        (deprecatedForExtension "ImplicitParams"),
      flagSpec' "scoped-type-variables"           Opt_ScopedTypeVariables
        (deprecatedForExtension "ScopedTypeVariables"),
      flagSpec' "parr"                            Opt_ParallelArrays
        (deprecatedForExtension "ParallelArrays"),
      flagSpec' "PArr"                            Opt_ParallelArrays
        (deprecatedForExtension "ParallelArrays"),
      flagSpec' "allow-overlapping-instances"     Opt_OverlappingInstances
        (deprecatedForExtension "OverlappingInstances"),
      flagSpec' "allow-undecidable-instances"     Opt_UndecidableInstances
        (deprecatedForExtension "UndecidableInstances"),
      flagSpec' "allow-incoherent-instances"      Opt_IncoherentInstances
        (deprecatedForExtension "IncoherentInstances")
      ]

    supportedLanguages :: [String]
    supportedLanguages = map flagSpecName languageFlags

    supportedLanguageOverlays :: [String]
    supportedLanguageOverlays = map flagSpecName safeHaskellFlags

    supportedExtensions :: [String]
    supportedExtensions
        = concatMap (\name -> [name, "No" ++ name]) (map flagSpecName xFlags)

    supportedLanguagesAndExtensions :: [String]
    supportedLanguagesAndExtensions =
        supportedLanguages ++ supportedLanguageOverlays ++ supportedExtensions

    -- | These -X<blah> flags cannot be reversed with -XNo<blah>
    languageFlags :: [FlagSpec Language]
    languageFlags = [
      flagSpec "Haskell98"   Haskell98,
      flagSpec "Haskell2010" Haskell2010
      ]

    -- | These -X<blah> flags cannot be reversed with -XNo<blah>
    -- They are used to place hard requirements on what GHC Haskell language
    -- features can be used.
    safeHaskellFlags :: [FlagSpec SafeHaskellMode]
    safeHaskellFlags = [mkF Sf_Unsafe, mkF Sf_Trustworthy, mkF Sf_Safe]
        where mkF flag = flagSpec (show flag) flag

    -- | These -X<blah> flags can all be reversed with -XNo<blah>
    xFlags :: [FlagSpec ExtensionFlag]
    xFlags = [
    -- See Note [Updating flag description in the User's Guide]
    -- See Note [Supporting CLI completion]
    -- Please keep the list of flags below sorted alphabetically
      flagSpec "AllowAmbiguousTypes"              Opt_AllowAmbiguousTypes,
      flagSpec "AlternativeLayoutRule"            Opt_AlternativeLayoutRule,
      flagSpec "AlternativeLayoutRuleTransitional"
                                              Opt_AlternativeLayoutRuleTransitional,
      flagSpec "Arrows"                           Opt_Arrows,
      flagSpec "AutoDeriveTypeable"               Opt_AutoDeriveTypeable,
      flagSpec "BangPatterns"                     Opt_BangPatterns,
      flagSpec "BinaryLiterals"                   Opt_BinaryLiterals,
      flagSpec "CApiFFI"                          Opt_CApiFFI,
      flagSpec "CPP"                              Opt_Cpp,
      flagSpec "ConstrainedClassMethods"          Opt_ConstrainedClassMethods,
      flagSpec "ConstraintKinds"                  Opt_ConstraintKinds,
      flagSpec "DataKinds"                        Opt_DataKinds,
      flagSpec' "DatatypeContexts"                Opt_DatatypeContexts
        (\ turn_on -> when turn_on $
             deprecate $ "It was widely considered a misfeature, " ++
                         "and has been removed from the Haskell language."),
      flagSpec "DefaultSignatures"                Opt_DefaultSignatures,
      flagSpec "DeriveAnyClass"                   Opt_DeriveAnyClass,
      flagSpec "DeriveDataTypeable"               Opt_DeriveDataTypeable,
      flagSpec "DeriveFoldable"                   Opt_DeriveFoldable,
      flagSpec "DeriveFunctor"                    Opt_DeriveFunctor,
      flagSpec "DeriveGeneric"                    Opt_DeriveGeneric,
      flagSpec "DeriveTraversable"                Opt_DeriveTraversable,
      flagSpec "DisambiguateRecordFields"         Opt_DisambiguateRecordFields,
      flagSpec "DoAndIfThenElse"                  Opt_DoAndIfThenElse,
      flagSpec' "DoRec"                           Opt_RecursiveDo
        (deprecatedForExtension "RecursiveDo"),
      flagSpec "EmptyCase"                        Opt_EmptyCase,
      flagSpec "EmptyDataDecls"                   Opt_EmptyDataDecls,
      flagSpec "ExistentialQuantification"        Opt_ExistentialQuantification,
      flagSpec "ExplicitForAll"                   Opt_ExplicitForAll,
      flagSpec "ExplicitNamespaces"               Opt_ExplicitNamespaces,
      flagSpec "ExtendedDefaultRules"             Opt_ExtendedDefaultRules,
      flagSpec "FlexibleContexts"                 Opt_FlexibleContexts,
      flagSpec "FlexibleInstances"                Opt_FlexibleInstances,
      flagSpec "ForeignFunctionInterface"         Opt_ForeignFunctionInterface,
      flagSpec "FunctionalDependencies"           Opt_FunctionalDependencies,
      flagSpec "GADTSyntax"                       Opt_GADTSyntax,
      flagSpec "GADTs"                            Opt_GADTs,
      flagSpec "GHCForeignImportPrim"             Opt_GHCForeignImportPrim,
      flagSpec' "GeneralizedNewtypeDeriving"      Opt_GeneralizedNewtypeDeriving
                                                  setGenDeriving,
      flagSpec "ImplicitParams"                   Opt_ImplicitParams,
      flagSpec "ImplicitPrelude"                  Opt_ImplicitPrelude,
      flagSpec "ImpredicativeTypes"               Opt_ImpredicativeTypes,
      flagSpec' "IncoherentInstances"             Opt_IncoherentInstances
                                                  setIncoherentInsts,
      flagSpec "InstanceSigs"                     Opt_InstanceSigs,
      flagSpec "InterruptibleFFI"                 Opt_InterruptibleFFI,
      flagSpec "JavaScriptFFI"                    Opt_JavaScriptFFI,
      flagSpec "KindSignatures"                   Opt_KindSignatures,
      flagSpec "LambdaCase"                       Opt_LambdaCase,
      flagSpec "LiberalTypeSynonyms"              Opt_LiberalTypeSynonyms,
      flagSpec "MagicHash"                        Opt_MagicHash,
      flagSpec "MonadComprehensions"              Opt_MonadComprehensions,
      flagSpec "MonoLocalBinds"                   Opt_MonoLocalBinds,
      flagSpec' "MonoPatBinds"                    Opt_MonoPatBinds
        (\ turn_on -> when turn_on $
             deprecate "Experimental feature now removed; has no effect"),
      flagSpec "MonomorphismRestriction"          Opt_MonomorphismRestriction,
      flagSpec "MultiParamTypeClasses"            Opt_MultiParamTypeClasses,
      flagSpec "MultiWayIf"                       Opt_MultiWayIf,
      flagSpec "NPlusKPatterns"                   Opt_NPlusKPatterns,
      flagSpec "NamedFieldPuns"                   Opt_RecordPuns,
      flagSpec "NamedWildCards"                   Opt_NamedWildCards,
      flagSpec "NegativeLiterals"                 Opt_NegativeLiterals,
      flagSpec "NondecreasingIndentation"         Opt_NondecreasingIndentation,
      flagSpec' "NullaryTypeClasses"              Opt_NullaryTypeClasses
        (deprecatedForExtension "MultiParamTypeClasses"),
      flagSpec "NumDecimals"                      Opt_NumDecimals,
      flagSpec' "OverlappingInstances"            Opt_OverlappingInstances
                                                  setOverlappingInsts,
      flagSpec "OverloadedLists"                  Opt_OverloadedLists,
      flagSpec "OverloadedStrings"                Opt_OverloadedStrings,
      flagSpec "PackageImports"                   Opt_PackageImports,
      flagSpec "ParallelArrays"                   Opt_ParallelArrays,
      flagSpec "ParallelListComp"                 Opt_ParallelListComp,
      flagSpec "PartialTypeSignatures"            Opt_PartialTypeSignatures,
      flagSpec "PatternGuards"                    Opt_PatternGuards,
      flagSpec' "PatternSignatures"               Opt_ScopedTypeVariables
        (deprecatedForExtension "ScopedTypeVariables"),
      flagSpec "PatternSynonyms"                  Opt_PatternSynonyms,
      flagSpec "PolyKinds"                        Opt_PolyKinds,
      flagSpec "PolymorphicComponents"            Opt_RankNTypes,
      flagSpec "PostfixOperators"                 Opt_PostfixOperators,
      flagSpec "QuasiQuotes"                      Opt_QuasiQuotes,
      flagSpec "Rank2Types"                       Opt_RankNTypes,
      flagSpec "RankNTypes"                       Opt_RankNTypes,
      flagSpec "RebindableSyntax"                 Opt_RebindableSyntax,
      flagSpec' "RecordPuns"                      Opt_RecordPuns
        (deprecatedForExtension "NamedFieldPuns"),
      flagSpec "RecordWildCards"                  Opt_RecordWildCards,
      flagSpec "RecursiveDo"                      Opt_RecursiveDo,
      flagSpec "RelaxedLayout"                    Opt_RelaxedLayout,
      flagSpec' "RelaxedPolyRec"                  Opt_RelaxedPolyRec
        (\ turn_on -> unless turn_on $
             deprecate "You can't turn off RelaxedPolyRec any more"),
      flagSpec "RoleAnnotations"                  Opt_RoleAnnotations,
      flagSpec "ScopedTypeVariables"              Opt_ScopedTypeVariables,
      flagSpec "StandaloneDeriving"               Opt_StandaloneDeriving,
      flagSpec "StaticPointers"                   Opt_StaticPointers,
      flagSpec' "TemplateHaskell"                 Opt_TemplateHaskell
                                                  checkTemplateHaskellOk,
      flagSpec "TraditionalRecordSyntax"          Opt_TraditionalRecordSyntax,
      flagSpec "TransformListComp"                Opt_TransformListComp,
      flagSpec "TupleSections"                    Opt_TupleSections,
      flagSpec "TypeFamilies"                     Opt_TypeFamilies,
      flagSpec "TypeOperators"                    Opt_TypeOperators,
      flagSpec "TypeSynonymInstances"             Opt_TypeSynonymInstances,
      flagSpec "UnboxedTuples"                    Opt_UnboxedTuples,
      flagSpec "UndecidableInstances"             Opt_UndecidableInstances,
      flagSpec "UnicodeSyntax"                    Opt_UnicodeSyntax,
      flagSpec "UnliftedFFITypes"                 Opt_UnliftedFFITypes,
      flagSpec "ViewPatterns"                     Opt_ViewPatterns
      ]

    defaultFlags :: Settings -> [GeneralFlag]
    defaultFlags settings
    -- See Note [Updating flag description in the User's Guide]
      = [ Opt_AutoLinkPackages,
          Opt_EmbedManifest,
          Opt_FlatCache,
          Opt_GenManifest,
          Opt_GhciHistory,
          Opt_GhciSandbox,
          Opt_HelpfulErrors,
          Opt_OmitYields,
          Opt_PrintBindContents,
          Opt_ProfCountEntries,
          Opt_RPath,
          Opt_SharedImplib,
          Opt_SimplPreInlining
        ]

        ++ [f | (ns,f) <- optLevelFlags, 0 `elem` ns]
                 -- The default -O0 options

        ++ default_PIC platform

        ++ (if pc_DYNAMIC_BY_DEFAULT (sPlatformConstants settings)
            then wayGeneralFlags platform WayDyn
            else [])

        where platform = sTargetPlatform settings

    default_PIC :: Platform -> [GeneralFlag]
    default_PIC platform =
      case (platformOS platform, platformArch platform) of
        (OSDarwin, ArchX86_64) -> [Opt_PIC]
        (OSOpenBSD, ArchX86_64) -> [Opt_PIC] -- Due to PIE support in
                                             -- OpenBSD since 5.3 release
                                             -- (1 May 2013) we need to
                                             -- always generate PIC. See
                                             -- #10597 for more
                                             -- information.
        _                      -> []

    impliedGFlags :: [(GeneralFlag, TurnOnFlag, GeneralFlag)]
    impliedGFlags = [(Opt_DeferTypeErrors, turnOn, Opt_DeferTypedHoles)]

    impliedXFlags :: [(ExtensionFlag, TurnOnFlag, ExtensionFlag)]
    impliedXFlags
    -- See Note [Updating flag description in the User's Guide]
      = [ (Opt_RankNTypes,                turnOn, Opt_ExplicitForAll)
        , (Opt_ScopedTypeVariables,       turnOn, Opt_ExplicitForAll)
        , (Opt_LiberalTypeSynonyms,       turnOn, Opt_ExplicitForAll)
        , (Opt_ExistentialQuantification, turnOn, Opt_ExplicitForAll)
        , (Opt_FlexibleInstances,         turnOn, Opt_TypeSynonymInstances)
        , (Opt_FunctionalDependencies,    turnOn, Opt_MultiParamTypeClasses)

        , (Opt_RebindableSyntax, turnOff, Opt_ImplicitPrelude)      -- NB: turn off!

        , (Opt_GADTs,            turnOn, Opt_GADTSyntax)
        , (Opt_GADTs,            turnOn, Opt_MonoLocalBinds)
        , (Opt_TypeFamilies,     turnOn, Opt_MonoLocalBinds)

        , (Opt_TypeFamilies,     turnOn, Opt_KindSignatures)  -- Type families use kind signatures
        , (Opt_PolyKinds,        turnOn, Opt_KindSignatures)  -- Ditto polymorphic kinds

        -- AutoDeriveTypeable is not very useful without DeriveDataTypeable
        , (Opt_AutoDeriveTypeable, turnOn, Opt_DeriveDataTypeable)

        -- We turn this on so that we can export associated type
        -- type synonyms in subordinates (e.g. MyClass(type AssocType))
        , (Opt_TypeFamilies,     turnOn, Opt_ExplicitNamespaces)
        , (Opt_TypeOperators, turnOn, Opt_ExplicitNamespaces)

        , (Opt_ImpredicativeTypes,  turnOn, Opt_RankNTypes)

            -- Record wild-cards implies field disambiguation
            -- Otherwise if you write (C {..}) you may well get
            -- stuff like " 'a' not in scope ", which is a bit silly
            -- if the compiler has just filled in field 'a' of constructor 'C'
        , (Opt_RecordWildCards,     turnOn, Opt_DisambiguateRecordFields)

        , (Opt_ParallelArrays, turnOn, Opt_ParallelListComp)

        -- An implicit parameter constraint, `?x::Int`, is desugared into
        -- `IP "x" Int`, which requires a flexible context/instance.
        , (Opt_ImplicitParams, turnOn, Opt_FlexibleContexts)
        , (Opt_ImplicitParams, turnOn, Opt_FlexibleInstances)

        , (Opt_JavaScriptFFI, turnOn, Opt_InterruptibleFFI)

        , (Opt_DeriveTraversable, turnOn, Opt_DeriveFunctor)
        , (Opt_DeriveTraversable, turnOn, Opt_DeriveFoldable)
      ]

    -- Note [Documenting optimisation flags]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- If you change the list of flags enabled for particular optimisation levels
    -- please remember to update the User's Guide. The relevant files are:
    --
    --  * docs/users_guide/flags.xml
    --  * docs/users_guide/using.xml
    --
    -- The first contains the Flag Refrence section, which breifly lists all
    -- available flags. The second contains a detailed description of the
    -- flags. Both places should contain information whether a flag is implied by
    -- -O0, -O or -O2.

    optLevelFlags :: [([Int], GeneralFlag)]
    optLevelFlags -- see Note [Documenting optimisation flags]
      = [ ([0,1,2], Opt_DoLambdaEtaExpansion)
        , ([0,1,2], Opt_DmdTxDictSel)
        , ([0,1,2], Opt_LlvmTBAA)
        , ([0,1,2], Opt_VectorisationAvoidance)
                    -- This one is important for a tiresome reason:
                    -- we want to make sure that the bindings for data
                    -- constructors are eta-expanded.  This is probably
                    -- a good thing anyway, but it seems fragile.

        , ([0],     Opt_IgnoreInterfacePragmas)
        , ([0],     Opt_OmitInterfacePragmas)

        , ([1,2],   Opt_CallArity)
        , ([1,2],   Opt_CaseMerge)
        , ([1,2],   Opt_CmmElimCommonBlocks)
        , ([1,2],   Opt_CmmSink)
        , ([1,2],   Opt_CSE)
        , ([1,2],   Opt_DoEtaReduction)
        , ([1,2],   Opt_EnableRewriteRules)  -- Off for -O0; see Note [Scoping for Builtin rules]
                                             --              in PrelRules
        , ([1,2],   Opt_FloatIn)
        , ([1,2],   Opt_FullLaziness)
        , ([1,2],   Opt_IgnoreAsserts)
        , ([1,2],   Opt_Loopification)
        , ([1,2],   Opt_Specialise)
        , ([1,2],   Opt_Strictness)
        , ([1,2],   Opt_UnboxSmallStrictFields)

        , ([2],     Opt_LiberateCase)
        , ([2],     Opt_SpecConstr)
    --  , ([2],     Opt_RegsGraph)
    --   RegsGraph suffers performance regression. See #7679
    --  , ([2],     Opt_StaticArgumentTransformation)
    --   Static Argument Transformation needs investigation. See #9374
        ]

    -- -----------------------------------------------------------------------------
    -- Standard sets of warning options

    -- Note [Documenting warning flags]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- If you change the list of warning enabled by default
    -- please remember to update the User's Guide. The relevant file is:
    --
    --  * docs/users_guide/using.xml

    standardWarnings :: [WarningFlag]
    standardWarnings -- see Note [Documenting warning flags]
        = [ Opt_WarnOverlappingPatterns,
            Opt_WarnWarningsDeprecations,
            Opt_WarnDeprecatedFlags,
            Opt_WarnTypedHoles,
            Opt_WarnPartialTypeSignatures,
            Opt_WarnUnrecognisedPragmas,
            Opt_WarnPointlessPragmas,
            Opt_WarnDuplicateConstraints,
            Opt_WarnDuplicateExports,
            Opt_WarnOverflowedLiterals,
            Opt_WarnEmptyEnumerations,
            Opt_WarnMissingFields,
            Opt_WarnMissingMethods,
            Opt_WarnWrongDoBind,
            Opt_WarnUnsupportedCallingConventions,
            Opt_WarnDodgyForeignImports,
            Opt_WarnInlineRuleShadowing,
            Opt_WarnAlternativeLayoutRuleTransitional,
            Opt_WarnUnsupportedLlvmVersion,
            Opt_WarnContextQuantification,
            Opt_WarnTabs
          ]

    minusWOpts :: [WarningFlag]
    -- Things you get with -W
    minusWOpts
        = standardWarnings ++
          [ Opt_WarnUnusedBinds,
            Opt_WarnUnusedMatches,
            Opt_WarnUnusedImports,
            Opt_WarnIncompletePatterns,
            Opt_WarnDodgyExports,
            Opt_WarnDodgyImports
          ]

    minusWallOpts :: [WarningFlag]
    -- Things you get with -Wall
    minusWallOpts
        = minusWOpts ++
          [ Opt_WarnTypeDefaults,
            Opt_WarnNameShadowing,
            Opt_WarnMissingSigs,
            Opt_WarnHiShadows,
            Opt_WarnOrphans,
            Opt_WarnUnusedDoBind,
            Opt_WarnTrustworthySafe,
            Opt_WarnUntickedPromotedConstructors
          ]

    enableGlasgowExts :: DynP ()
    enableGlasgowExts = do setGeneralFlag Opt_PrintExplicitForalls
                           mapM_ setExtensionFlag glasgowExtsFlags

    disableGlasgowExts :: DynP ()
    disableGlasgowExts = do unSetGeneralFlag Opt_PrintExplicitForalls
                            mapM_ unSetExtensionFlag glasgowExtsFlags

    glasgowExtsFlags :: [ExtensionFlag]
    glasgowExtsFlags = [
                 Opt_ConstrainedClassMethods
               , Opt_DeriveDataTypeable
               , Opt_DeriveFoldable
               , Opt_DeriveFunctor
               , Opt_DeriveGeneric
               , Opt_DeriveTraversable
               , Opt_EmptyDataDecls
               , Opt_ExistentialQuantification
               , Opt_ExplicitNamespaces
               , Opt_FlexibleContexts
               , Opt_FlexibleInstances
               , Opt_ForeignFunctionInterface
               , Opt_FunctionalDependencies
               , Opt_GeneralizedNewtypeDeriving
               , Opt_ImplicitParams
               , Opt_KindSignatures
               , Opt_LiberalTypeSynonyms
               , Opt_MagicHash
               , Opt_MultiParamTypeClasses
               , Opt_ParallelListComp
               , Opt_PatternGuards
               , Opt_PostfixOperators
               , Opt_RankNTypes
               , Opt_RecursiveDo
               , Opt_ScopedTypeVariables
               , Opt_StandaloneDeriving
               , Opt_TypeOperators
               , Opt_TypeSynonymInstances
               , Opt_UnboxedTuples
               , Opt_UnicodeSyntax
               , Opt_UnliftedFFITypes ]

    #ifdef GHCI
    -- Consult the RTS to find whether GHC itself has been built profiled
    -- If so, you can't use Template Haskell
    foreign import ccall unsafe "rts_isProfiled" rtsIsProfiledIO :: IO CInt

    rtsIsProfiled :: Bool
    rtsIsProfiled = unsafeDupablePerformIO rtsIsProfiledIO /= 0
    #endif

    #ifdef GHCI
    -- Consult the RTS to find whether GHC itself has been built with
    -- dynamic linking.  This can't be statically known at compile-time,
    -- because we build both the static and dynamic versions together with
    -- -dynamic-too.
    foreign import ccall unsafe "rts_isDynamic" rtsIsDynamicIO :: IO CInt

    dynamicGhc :: Bool
    dynamicGhc = unsafeDupablePerformIO rtsIsDynamicIO /= 0
    #else
    dynamicGhc :: Bool
    dynamicGhc = False
    #endif

    setWarnSafe :: Bool -> DynP ()
    setWarnSafe True  = getCurLoc >>= \l -> upd (\d -> d { warnSafeOnLoc = l })
    setWarnSafe False = return ()

    setWarnUnsafe :: Bool -> DynP ()
    setWarnUnsafe True  = getCurLoc >>= \l -> upd (\d -> d { warnUnsafeOnLoc = l })
    setWarnUnsafe False = return ()

    setPackageTrust :: DynP ()
    setPackageTrust = do
        setGeneralFlag Opt_PackageTrust
        l <- getCurLoc
        upd $ \d -> d { pkgTrustOnLoc = l }

    setGenDeriving :: TurnOnFlag -> DynP ()
    setGenDeriving True  = getCurLoc >>= \l -> upd (\d -> d { newDerivOnLoc = l })
    setGenDeriving False = return ()

    setOverlappingInsts :: TurnOnFlag -> DynP ()
    setOverlappingInsts False = return ()
    setOverlappingInsts True = do
      l <- getCurLoc
      upd (\d -> d { overlapInstLoc = l })
      deprecate "instead use per-instance pragmas OVERLAPPING/OVERLAPPABLE/OVERLAPS"

    setIncoherentInsts :: TurnOnFlag -> DynP ()
    setIncoherentInsts False = return ()
    setIncoherentInsts True = do
      l <- getCurLoc
      upd (\d -> d { incoherentOnLoc = l })

    checkTemplateHaskellOk :: TurnOnFlag -> DynP ()
    #ifdef GHCI
    checkTemplateHaskellOk turn_on
      | turn_on && rtsIsProfiled
      = addErr "You can't use Template Haskell with a profiled compiler"
      | otherwise
      = getCurLoc >>= \l -> upd (\d -> d { thOnLoc = l })
    #else
    -- In stage 1, Template Haskell is simply illegal, except with -M
    -- We don't bleat with -M because there's no problem with TH there,
    -- and in fact GHC's build system does ghc -M of the DPH libraries
    -- with a stage1 compiler
    checkTemplateHaskellOk turn_on
      | turn_on = do dfs <- liftEwM getCmdLineState
                     case ghcMode dfs of
                        MkDepend -> return ()
                        _        -> addErr msg
      | otherwise = return ()
      where
        msg = "Template Haskell requires GHC with interpreter support\n    " ++
              "Perhaps you are using a stage-1 compiler?"
    #endif

    {- **********************************************************************
    %*                                                                      *
                    DynFlags constructors
    %*                                                                      *
    %********************************************************************* -}

    type DynP = EwM (CmdLineP DynFlags)

    upd :: (DynFlags -> DynFlags) -> DynP ()
    upd f = liftEwM (do dflags <- getCmdLineState
                        putCmdLineState $! f dflags)

    updM :: (DynFlags -> DynP DynFlags) -> DynP ()
    updM f = do dflags <- liftEwM getCmdLineState
                dflags' <- f dflags
                liftEwM $ putCmdLineState $! dflags'

    --------------- Constructor functions for OptKind -----------------
    noArg :: (DynFlags -> DynFlags) -> OptKind (CmdLineP DynFlags)
    noArg fn = NoArg (upd fn)

    noArgM :: (DynFlags -> DynP DynFlags) -> OptKind (CmdLineP DynFlags)
    noArgM fn = NoArg (updM fn)

    hasArg :: (String -> DynFlags -> DynFlags) -> OptKind (CmdLineP DynFlags)
    hasArg fn = HasArg (upd . fn)

    sepArg :: (String -> DynFlags -> DynFlags) -> OptKind (CmdLineP DynFlags)
    sepArg fn = SepArg (upd . fn)

    intSuffix :: (Int -> DynFlags -> DynFlags) -> OptKind (CmdLineP DynFlags)
    intSuffix fn = IntSuffix (\n -> upd (fn n))

    floatSuffix :: (Float -> DynFlags -> DynFlags) -> OptKind (CmdLineP DynFlags)
    floatSuffix fn = FloatSuffix (\n -> upd (fn n))

    optIntSuffixM :: (Maybe Int -> DynFlags -> DynP DynFlags)
                  -> OptKind (CmdLineP DynFlags)
    optIntSuffixM fn = OptIntSuffix (\mi -> updM (fn mi))

    setDumpFlag :: DumpFlag -> OptKind (CmdLineP DynFlags)
    setDumpFlag dump_flag = NoArg (setDumpFlag' dump_flag)

    --------------------------
    addWay :: Way -> DynP ()
    addWay w = upd (addWay' w)

    addWay' :: Way -> DynFlags -> DynFlags
    addWay' w dflags0 = let platform = targetPlatform dflags0
                            dflags1 = dflags0 { ways = w : ways dflags0 }
                            dflags2 = wayExtras platform w dflags1
                            dflags3 = foldr setGeneralFlag' dflags2
                                            (wayGeneralFlags platform w)
                            dflags4 = foldr unSetGeneralFlag' dflags3
                                            (wayUnsetGeneralFlags platform w)
                        in dflags4

    removeWayDyn :: DynP ()
    removeWayDyn = upd (\dfs -> dfs { ways = filter (WayDyn /=) (ways dfs) })

    --------------------------
    setGeneralFlag, unSetGeneralFlag :: GeneralFlag -> DynP ()
    setGeneralFlag   f = upd (setGeneralFlag' f)
    unSetGeneralFlag f = upd (unSetGeneralFlag' f)

    setGeneralFlag' :: GeneralFlag -> DynFlags -> DynFlags
    setGeneralFlag' f dflags = foldr ($) (gopt_set dflags f) deps
      where
        deps = [ if turn_on then setGeneralFlag'   d
                            else unSetGeneralFlag' d
               | (f', turn_on, d) <- impliedGFlags, f' == f ]
            -- When you set f, set the ones it implies
            -- NB: use setGeneralFlag recursively, in case the implied flags
            --     implies further flags

    unSetGeneralFlag' :: GeneralFlag -> DynFlags -> DynFlags
    unSetGeneralFlag' f dflags = gopt_unset dflags f
       -- When you un-set f, however, we don't un-set the things it implies

    --------------------------
    setWarningFlag, unSetWarningFlag :: WarningFlag -> DynP ()
    setWarningFlag   f = upd (\dfs -> wopt_set dfs f)
    unSetWarningFlag f = upd (\dfs -> wopt_unset dfs f)

    --------------------------
    setExtensionFlag, unSetExtensionFlag :: ExtensionFlag -> DynP ()
    setExtensionFlag f = upd (setExtensionFlag' f)
    unSetExtensionFlag f = upd (unSetExtensionFlag' f)

    setExtensionFlag', unSetExtensionFlag' :: ExtensionFlag -> DynFlags -> DynFlags
    setExtensionFlag' f dflags = foldr ($) (xopt_set dflags f) deps
      where
        deps = [ if turn_on then setExtensionFlag'   d
                            else unSetExtensionFlag' d
               | (f', turn_on, d) <- impliedXFlags, f' == f ]
            -- When you set f, set the ones it implies
            -- NB: use setExtensionFlag recursively, in case the implied flags
            --     implies further flags

    unSetExtensionFlag' f dflags = xopt_unset dflags f
       -- When you un-set f, however, we don't un-set the things it implies
       --      (except for -fno-glasgow-exts, which is treated specially)

    --------------------------
    alterSettings :: (Settings -> Settings) -> DynFlags -> DynFlags
    alterSettings f dflags = dflags { settings = f (settings dflags) }

    --------------------------
    setDumpFlag' :: DumpFlag -> DynP ()
    setDumpFlag' dump_flag
      = do upd (\dfs -> dopt_set dfs dump_flag)
           when want_recomp forceRecompile
        where -- Certain dumpy-things are really interested in what's going
              -- on during recompilation checking, so in those cases we
              -- don't want to turn it off.
              want_recomp = dump_flag `notElem` [Opt_D_dump_if_trace,
                                                 Opt_D_dump_hi_diffs]

    forceRecompile :: DynP ()
    -- Whenver we -ddump, force recompilation (by switching off the
    -- recompilation checker), else you don't see the dump! However,
    -- don't switch it off in --make mode, else *everything* gets
    -- recompiled which probably isn't what you want
    forceRecompile = do dfs <- liftEwM getCmdLineState
                        when (force_recomp dfs) (setGeneralFlag Opt_ForceRecomp)
            where
              force_recomp dfs = isOneShot (ghcMode dfs)

    setVerboseCore2Core :: DynP ()
    setVerboseCore2Core = setDumpFlag' Opt_D_verbose_core2core

    setVerbosity :: Maybe Int -> DynP ()
    setVerbosity mb_n = upd (\dfs -> dfs{ verbosity = mb_n `orElse` 3 })

    addCmdlineHCInclude :: String -> DynP ()
    addCmdlineHCInclude a = upd (\s -> s{cmdlineHcIncludes =  a : cmdlineHcIncludes s})

    data PkgConfRef
      = GlobalPkgConf
      | UserPkgConf
      | PkgConfFile FilePath

    addPkgConfRef :: PkgConfRef -> DynP ()
    addPkgConfRef p = upd $ \s -> s { extraPkgConfs = (p:) . extraPkgConfs s }

    removeUserPkgConf :: DynP ()
    removeUserPkgConf = upd $ \s -> s { extraPkgConfs = filter isNotUser . extraPkgConfs s }
      where
        isNotUser UserPkgConf = False
        isNotUser _ = True

    removeGlobalPkgConf :: DynP ()
    removeGlobalPkgConf = upd $ \s -> s { extraPkgConfs = filter isNotGlobal . extraPkgConfs s }
      where
        isNotGlobal GlobalPkgConf = False
        isNotGlobal _ = True

    clearPkgConf :: DynP ()
    clearPkgConf = upd $ \s -> s { extraPkgConfs = const [] }

    parseModuleName :: ReadP String
    parseModuleName = munch1 (\c -> isAlphaNum c || c `elem` ".")

    parsePackageFlag :: (String -> PackageArg) -- type of argument
                     -> String                 -- string to parse
                     -> PackageFlag
    parsePackageFlag constr str = case filter ((=="").snd) (readP_to_S parse str) of
        [(r, "")] -> r
        _ -> throwGhcException $ CmdLineError ("Can't parse package flag: " ++ str)
      where parse = do
                pkg <- tok $ munch1 (\c -> isAlphaNum c || c `elem` ":-_.")
                ( do _ <- tok $ string "with"
                     fmap (ExposePackage (constr pkg) . ModRenaming True) parseRns
                 <++ fmap (ExposePackage (constr pkg) . ModRenaming False) parseRns
                 <++ return (ExposePackage (constr pkg) (ModRenaming True [])))
            parseRns = do _ <- tok $ R.char '('
                          rns <- tok $ sepBy parseItem (tok $ R.char ',')
                          _ <- tok $ R.char ')'
                          return rns
            parseItem = do
                orig <- tok $ parseModuleName
                (do _ <- tok $ string "as"
                    new <- tok $ parseModuleName
                    return (orig, new)
                  +++
                 return (orig, orig))
            tok m = m >>= \x -> skipSpaces >> return x

    exposePackage, exposePackageId, exposePackageKey, hidePackage, ignorePackage,
            trustPackage, distrustPackage :: String -> DynP ()
    exposePackage p = upd (exposePackage' p)
    exposePackageId p =
      upd (\s -> s{ packageFlags =
        parsePackageFlag PackageIdArg p : packageFlags s })
    exposePackageKey p =
      upd (\s -> s{ packageFlags =
        parsePackageFlag PackageKeyArg p : packageFlags s })
    hidePackage p =
      upd (\s -> s{ packageFlags = HidePackage p : packageFlags s })
    ignorePackage p =
      upd (\s -> s{ packageFlags = IgnorePackage p : packageFlags s })
    trustPackage p = exposePackage p >> -- both trust and distrust also expose a package
      upd (\s -> s{ packageFlags = TrustPackage p : packageFlags s })
    distrustPackage p = exposePackage p >>
      upd (\s -> s{ packageFlags = DistrustPackage p : packageFlags s })

    exposePackage' :: String -> DynFlags -> DynFlags
    exposePackage' p dflags
        = dflags { packageFlags =
                parsePackageFlag PackageArg p : packageFlags dflags }

    setPackageKey :: String -> DynFlags -> DynFlags
    setPackageKey p s =  s{ thisPackage = stringToPackageKey p }

    -- -----------------------------------------------------------------------------
    -- | Find the package environment (if one exists)
    --
    -- We interpret the package environment as a set of package flags; to be
    -- specific, if we find a package environment
    --
    -- > id1
    -- > id2
    -- > ..
    -- > idn
    --
    -- we interpret this as
    --
    -- > [ -hide-all-packages
    -- > , -package-id id1
    -- > , -package-id id2
    -- > , ..
    -- > , -package-id idn
    -- > ]
    interpretPackageEnv :: DynFlags -> IO DynFlags
    interpretPackageEnv dflags = do
        mPkgEnv <- runMaybeT $ msum $ [
                       getCmdLineArg >>= \env -> msum [
                           loadEnvFile  env
                         , loadEnvName  env
                         , cmdLineError env
                         ]
                     , getEnvVar >>= \env -> msum [
                           loadEnvFile env
                         , loadEnvName env
                         , envError    env
                         ]
                     , loadEnvFile localEnvFile
                     , loadEnvName defaultEnvName
                     ]
        case mPkgEnv of
          Nothing ->
            -- No environment found. Leave DynFlags unchanged.
            return dflags
          Just ids -> do
            let setFlags :: DynP ()
                setFlags = do
                  setGeneralFlag Opt_HideAllPackages
                  mapM_ exposePackageId (lines ids)

                (_, dflags') = runCmdLine (runEwM setFlags) dflags

            return dflags'
      where
        -- Loading environments (by name or by location)

        namedEnvPath :: String -> MaybeT IO FilePath
        namedEnvPath name = do
         appdir <- liftMaybeT $ versionedAppDir dflags
         return $ appdir </> "environments" </> name

        loadEnvName :: String -> MaybeT IO String
        loadEnvName name = loadEnvFile =<< namedEnvPath name

        loadEnvFile :: String -> MaybeT IO String
        loadEnvFile path = do
          guard =<< liftMaybeT (doesFileExist path)
          liftMaybeT $ readFile path

        -- Various ways to define which environment to use

        getCmdLineArg :: MaybeT IO String
        getCmdLineArg = MaybeT $ return $ packageEnv dflags

        getEnvVar :: MaybeT IO String
        getEnvVar = do
          mvar <- liftMaybeT $ try $ getEnv "GHC_ENVIRONMENT"
          case mvar of
            Right var -> return var
            Left err  -> if isDoesNotExistError err then mzero
                                                    else liftMaybeT $ throwIO err

        defaultEnvName :: String
        defaultEnvName = "default"

        localEnvFile :: FilePath
        localEnvFile = "./.ghc.environment"

        -- Error reporting

        cmdLineError :: String -> MaybeT IO a
        cmdLineError env = liftMaybeT . throwGhcExceptionIO . CmdLineError $
          "Package environment " ++ show env ++ " not found"

        envError :: String -> MaybeT IO a
        envError env = liftMaybeT . throwGhcExceptionIO . CmdLineError $
             "Package environment "
          ++ show env
          ++ " (specified in GHC_ENVIRIONMENT) not found"

    -- If we're linking a binary, then only targets that produce object
    -- code are allowed (requests for other target types are ignored).
    setTarget :: HscTarget -> DynP ()
    setTarget l = setTargetWithPlatform (const l)

    setTargetWithPlatform :: (Platform -> HscTarget) -> DynP ()
    setTargetWithPlatform f = upd set
      where
       set dfs = let l = f (targetPlatform dfs)
                 in if ghcLink dfs /= LinkBinary || isObjectTarget l
                    then dfs{ hscTarget = l }
                    else dfs

    -- Changes the target only if we're compiling object code.  This is
    -- used by -fasm and -fllvm, which switch from one to the other, but
    -- not from bytecode to object-code.  The idea is that -fasm/-fllvm
    -- can be safely used in an OPTIONS_GHC pragma.
    setObjTarget :: HscTarget -> DynP ()
    setObjTarget l = updM set
      where
       set dflags
         | isObjectTarget (hscTarget dflags)
           = return $ dflags { hscTarget = l }
         | otherwise = return dflags

    setOptLevel :: Int -> DynFlags -> DynP DynFlags
    setOptLevel n dflags = return (updOptLevel n dflags)

    checkOptLevel :: Int -> DynFlags -> Either String DynFlags
    checkOptLevel n dflags
       | hscTarget dflags == HscInterpreted && n > 0
         = Left "-O conflicts with --interactive; -O ignored."
       | otherwise
         = Right dflags

    -- -Odph is equivalent to
    --
    --    -O2                               optimise as much as possible
    --    -fmax-simplifier-iterations20     this is necessary sometimes
    --    -fsimplifier-phases=3             we use an additional simplifier phase for fusion
    --
    setDPHOpt :: DynFlags -> DynP DynFlags
    setDPHOpt dflags = setOptLevel 2 (dflags { maxSimplIterations  = 20
                                             , simplPhases         = 3
                                             })

    setMainIs :: String -> DynP ()
    setMainIs arg
      | not (null main_fn) && isLower (head main_fn)
         -- The arg looked like "Foo.Bar.baz"
      = upd $ \d -> d{ mainFunIs = Just main_fn,
                       mainModIs = mkModule mainPackageKey (mkModuleName main_mod) }

      | isUpper (head arg)  -- The arg looked like "Foo" or "Foo.Bar"
      = upd $ \d -> d{ mainModIs = mkModule mainPackageKey (mkModuleName arg) }

      | otherwise                   -- The arg looked like "baz"
      = upd $ \d -> d{ mainFunIs = Just arg }
      where
        (main_mod, main_fn) = splitLongestPrefix arg (== '.')

    addLdInputs :: Option -> DynFlags -> DynFlags
    addLdInputs p dflags = dflags{ldInputs = ldInputs dflags ++ [p]}

    -----------------------------------------------------------------------------
    -- Paths & Libraries

    addImportPath, addLibraryPath, addIncludePath, addFrameworkPath :: FilePath -> DynP ()

    -- -i on its own deletes the import paths
    addImportPath "" = upd (\s -> s{importPaths = []})
    addImportPath p  = upd (\s -> s{importPaths = importPaths s ++ splitPathList p})

    addLibraryPath p =
      upd (\s -> s{libraryPaths = libraryPaths s ++ splitPathList p})

    addIncludePath p =
      upd (\s -> s{includePaths = includePaths s ++ splitPathList p})

    addFrameworkPath p =
      upd (\s -> s{frameworkPaths = frameworkPaths s ++ splitPathList p})

    #ifndef mingw32_TARGET_OS
    split_marker :: Char
    split_marker = ':'   -- not configurable (ToDo)
    #endif

    splitPathList :: String -> [String]
    splitPathList s = filter notNull (splitUp s)
                    -- empty paths are ignored: there might be a trailing
                    -- ':' in the initial list, for example.  Empty paths can
                    -- cause confusion when they are translated into -I options
                    -- for passing to gcc.
      where
    #ifndef mingw32_TARGET_OS
        splitUp xs = split split_marker xs
    #else
         -- Windows: 'hybrid' support for DOS-style paths in directory lists.
         --
         -- That is, if "foo:bar:baz" is used, this interpreted as
         -- consisting of three entries, 'foo', 'bar', 'baz'.
         -- However, with "c:/foo:c:\\foo;x:/bar", this is interpreted
         -- as 3 elts, "c:/foo", "c:\\foo", "x:/bar"
         --
         -- Notice that no attempt is made to fully replace the 'standard'
         -- split marker ':' with the Windows / DOS one, ';'. The reason being
         -- that this will cause too much breakage for users & ':' will
         -- work fine even with DOS paths, if you're not insisting on being silly.
         -- So, use either.
        splitUp []             = []
        splitUp (x:':':div:xs) | div `elem` dir_markers
                               = ((x:':':div:p): splitUp rs)
                               where
                                  (p,rs) = findNextPath xs
              -- we used to check for existence of the path here, but that
              -- required the IO monad to be threaded through the command-line
              -- parser which is quite inconvenient.  The
        splitUp xs = cons p (splitUp rs)
                   where
                     (p,rs) = findNextPath xs

                     cons "" xs = xs
                     cons x  xs = x:xs

        -- will be called either when we've consumed nought or the
        -- "<Drive>:/" part of a DOS path, so splitting is just a Q of
        -- finding the next split marker.
        findNextPath xs =
            case break (`elem` split_markers) xs of
               (p, _:ds) -> (p, ds)
               (p, xs)   -> (p, xs)

        split_markers :: [Char]
        split_markers = [':', ';']

        dir_markers :: [Char]
        dir_markers = ['/', '\\']
    #endif

    -- -----------------------------------------------------------------------------
    -- tmpDir, where we store temporary files.

    setTmpDir :: FilePath -> DynFlags -> DynFlags
    setTmpDir dir = alterSettings (\s -> s { sTmpDir = normalise dir })
      -- we used to fix /cygdrive/c/.. on Windows, but this doesn't
      -- seem necessary now --SDM 7/2/2008

    -----------------------------------------------------------------------------
    -- RTS opts

    setRtsOpts :: String -> DynP ()
    setRtsOpts arg  = upd $ \ d -> d {rtsOpts = Just arg}

    setRtsOptsEnabled :: RtsOptsEnabled -> DynP ()
    setRtsOptsEnabled arg  = upd $ \ d -> d {rtsOptsEnabled = arg}

    -----------------------------------------------------------------------------
    -- Hpc stuff

    setOptHpcDir :: String -> DynP ()
    setOptHpcDir arg  = upd $ \ d -> d{hpcDir = arg}

    -----------------------------------------------------------------------------
    -- Via-C compilation stuff

    -- There are some options that we need to pass to gcc when compiling
    -- Haskell code via C, but are only supported by recent versions of
    -- gcc.  The configure script decides which of these options we need,
    -- and puts them in the "settings" file in $topdir. The advantage of
    -- having these in a separate file is that the file can be created at
    -- install-time depending on the available gcc version, and even
    -- re-generated later if gcc is upgraded.
    --
    -- The options below are not dependent on the version of gcc, only the
    -- platform.

    picCCOpts :: DynFlags -> [String]
    picCCOpts dflags
        = case platformOS (targetPlatform dflags) of
          OSDarwin
              -- Apple prefers to do things the other way round.
              -- PIC is on by default.
              -- -mdynamic-no-pic:
              --     Turn off PIC code generation.
              -- -fno-common:
              --     Don't generate "common" symbols - these are unwanted
              --     in dynamic libraries.

           | gopt Opt_PIC dflags -> ["-fno-common", "-U__PIC__", "-D__PIC__"]
           | otherwise           -> ["-mdynamic-no-pic"]
          OSMinGW32 -- no -fPIC for Windows
           | gopt Opt_PIC dflags -> ["-U__PIC__", "-D__PIC__"]
           | otherwise           -> []
          _
          -- we need -fPIC for C files when we are compiling with -dynamic,
          -- otherwise things like stub.c files don't get compiled
          -- correctly.  They need to reference data in the Haskell
          -- objects, but can't without -fPIC.  See
          -- http://ghc.haskell.org/trac/ghc/wiki/Commentary/PositionIndependentCode
           | gopt Opt_PIC dflags || not (gopt Opt_Static dflags) ->
              ["-fPIC", "-U__PIC__", "-D__PIC__"]
           | otherwise                             -> []

    picPOpts :: DynFlags -> [String]
    picPOpts dflags
     | gopt Opt_PIC dflags = ["-U__PIC__", "-D__PIC__"]
     | otherwise           = []

    -- -----------------------------------------------------------------------------
    -- Splitting

    can_split :: Bool
    can_split = cSupportsSplitObjs == "YES"

    -- -----------------------------------------------------------------------------
    -- Compiler Info

    compilerInfo :: DynFlags -> [(String, String)]
    compilerInfo dflags
        = -- We always make "Project name" be first to keep parsing in
          -- other languages simple, i.e. when looking for other fields,
          -- you don't have to worry whether there is a leading '[' or not
          ("Project name",                 cProjectName)
          -- Next come the settings, so anything else can be overridden
          -- in the settings file (as "lookup" uses the first match for the
          -- key)
        : rawSettings dflags
       ++ [("Project version",             projectVersion dflags),
           ("Project Git commit id",       cProjectGitCommitId),
           ("Booter version",              cBooterVersion),
           ("Stage",                       cStage),
           ("Build platform",              cBuildPlatformString),
           ("Host platform",               cHostPlatformString),
           ("Target platform",             cTargetPlatformString),
           ("Have interpreter",            cGhcWithInterpreter),
           ("Object splitting supported",  cSupportsSplitObjs),
           ("Have native code generator",  cGhcWithNativeCodeGen),
           ("Support SMP",                 cGhcWithSMP),
           ("Tables next to code",         cGhcEnableTablesNextToCode),
           ("RTS ways",                    cGhcRTSWays),
           ("Support dynamic-too",         if isWindows then "NO" else "YES"),
           ("Support parallel --make",     "YES"),
           ("Support reexported-modules",  "YES"),
           ("Support thinning and renaming package flags", "YES"),
           ("Uses package keys",           "YES"),
           ("Dynamic by default",          if dYNAMIC_BY_DEFAULT dflags
                                           then "YES" else "NO"),
           ("GHC Dynamic",                 if dynamicGhc
                                           then "YES" else "NO"),
           ("Leading underscore",          cLeadingUnderscore),
           ("Debug on",                    show debugIsOn),
           ("LibDir",                      topDir dflags),
           ("Global Package DB",           systemPackageConfig dflags)
          ]
      where
        isWindows = platformOS (targetPlatform dflags) == OSMinGW32

    #include "../includes/dist-derivedconstants/header/GHCConstantsHaskellWrappers.hs"

    bLOCK_SIZE_W :: DynFlags -> Int
    bLOCK_SIZE_W dflags = bLOCK_SIZE dflags `quot` wORD_SIZE dflags

    wORD_SIZE_IN_BITS :: DynFlags -> Int
    wORD_SIZE_IN_BITS dflags = wORD_SIZE dflags * 8

    tAG_MASK :: DynFlags -> Int
    tAG_MASK dflags = (1 `shiftL` tAG_BITS dflags) - 1

    mAX_PTR_TAG :: DynFlags -> Int
    mAX_PTR_TAG = tAG_MASK

    -- Might be worth caching these in targetPlatform?
    tARGET_MIN_INT, tARGET_MAX_INT, tARGET_MAX_WORD :: DynFlags -> Integer
    tARGET_MIN_INT dflags
        = case platformWordSize (targetPlatform dflags) of
          4 -> toInteger (minBound :: Int32)
          8 -> toInteger (minBound :: Int64)
          w -> panic ("tARGET_MIN_INT: Unknown platformWordSize: " ++ show w)
    tARGET_MAX_INT dflags
        = case platformWordSize (targetPlatform dflags) of
          4 -> toInteger (maxBound :: Int32)
          8 -> toInteger (maxBound :: Int64)
          w -> panic ("tARGET_MAX_INT: Unknown platformWordSize: " ++ show w)
    tARGET_MAX_WORD dflags
        = case platformWordSize (targetPlatform dflags) of
          4 -> toInteger (maxBound :: Word32)
          8 -> toInteger (maxBound :: Word64)
          w -> panic ("tARGET_MAX_WORD: Unknown platformWordSize: " ++ show w)

    -- Whenever makeDynFlagsConsistent does anything, it starts over, to
    -- ensure that a later change doesn't invalidate an earlier check.
    -- Be careful not to introduce potential loops!
    makeDynFlagsConsistent :: DynFlags -> (DynFlags, [Located String])
    makeDynFlagsConsistent dflags
     -- Disable -dynamic-too on Windows (#8228, #7134, #5987)
     | os == OSMinGW32 && gopt Opt_BuildDynamicToo dflags
        = let dflags' = gopt_unset dflags Opt_BuildDynamicToo
              warn    = "-dynamic-too is not supported on Windows"
          in loop dflags' warn
     | hscTarget dflags == HscC &&
       not (platformUnregisterised (targetPlatform dflags))
        = if cGhcWithNativeCodeGen == "YES"
          then let dflags' = dflags { hscTarget = HscAsm }
                   warn = "Compiler not unregisterised, so using native code generator rather than compiling via C"
               in loop dflags' warn
          else let dflags' = dflags { hscTarget = HscLlvm }
                   warn = "Compiler not unregisterised, so using LLVM rather than compiling via C"
               in loop dflags' warn
     | hscTarget dflags == HscAsm &&
       platformUnregisterised (targetPlatform dflags)
        = loop (dflags { hscTarget = HscC })
               "Compiler unregisterised, so compiling via C"
     | hscTarget dflags == HscAsm &&
       cGhcWithNativeCodeGen /= "YES"
          = let dflags' = dflags { hscTarget = HscLlvm }
                warn = "No native code generator, so using LLVM"
            in loop dflags' warn
     | hscTarget dflags == HscLlvm &&
       not ((arch == ArchX86_64) && (os == OSLinux || os == OSDarwin || os == OSFreeBSD)) &&
       not ((isARM arch) && (os == OSLinux)) &&
       (not (gopt Opt_Static dflags) || gopt Opt_PIC dflags)
        = if cGhcWithNativeCodeGen == "YES"
          then let dflags' = dflags { hscTarget = HscAsm }
                   warn = "Using native code generator rather than LLVM, as LLVM is incompatible with -fPIC and -dynamic on this platform"
               in loop dflags' warn
          else throwGhcException $ CmdLineError "Can't use -fPIC or -dynamic on this platform"
     | os == OSDarwin &&
       arch == ArchX86_64 &&
       not (gopt Opt_PIC dflags)
        = loop (gopt_set dflags Opt_PIC)
               "Enabling -fPIC as it is always on for this platform"
     | otherwise = (dflags, [])
        where loc = mkGeneralSrcSpan (fsLit "when making flags consistent")
              loop updated_dflags warning
                  = case makeDynFlagsConsistent updated_dflags of
                    (dflags', ws) -> (dflags', L loc warning : ws)
              platform = targetPlatform dflags
              arch = platformArch platform
              os   = platformOS   platform

    --------------------------------------------------------------------------
    -- Do not use unsafeGlobalDynFlags!
    --
    -- unsafeGlobalDynFlags is a hack, necessary because we need to be able
    -- to show SDocs when tracing, but we don't always have DynFlags
    -- available.
    --
    -- Do not use it if you can help it. You may get the wrong value, or this
    -- panic!

    GLOBAL_VAR(v_unsafeGlobalDynFlags, panic "v_unsafeGlobalDynFlags: not initialised", DynFlags)

    unsafeGlobalDynFlags :: DynFlags
    unsafeGlobalDynFlags = unsafePerformIO $ readIORef v_unsafeGlobalDynFlags

    setUnsafeGlobalDynFlags :: DynFlags -> IO ()
    setUnsafeGlobalDynFlags = writeIORef v_unsafeGlobalDynFlags

    -- -----------------------------------------------------------------------------
    -- SSE and AVX

    -- TODO: Instead of using a separate predicate (i.e. isSse2Enabled) to
    -- check if SSE is enabled, we might have x86-64 imply the -msse2
    -- flag.

    data SseVersion = SSE1
                    | SSE2
                    | SSE3
                    | SSE4
                    | SSE42
                    deriving (Eq, Ord)

    isSseEnabled :: DynFlags -> Bool
    isSseEnabled dflags = case platformArch (targetPlatform dflags) of
        ArchX86_64 -> True
        ArchX86    -> sseVersion dflags >= Just SSE1
        _          -> False

    isSse2Enabled :: DynFlags -> Bool
    isSse2Enabled dflags = case platformArch (targetPlatform dflags) of
        ArchX86_64 -> -- SSE2 is fixed on for x86_64.  It would be
                      -- possible to make it optional, but we'd need to
                      -- fix at least the foreign call code where the
                      -- calling convention specifies the use of xmm regs,
                      -- and possibly other places.
                      True
        ArchX86    -> sseVersion dflags >= Just SSE2
        _          -> False

    isSse4_2Enabled :: DynFlags -> Bool
    isSse4_2Enabled dflags = sseVersion dflags >= Just SSE42

    isAvxEnabled :: DynFlags -> Bool
    isAvxEnabled dflags = avx dflags || avx2 dflags || avx512f dflags

    isAvx2Enabled :: DynFlags -> Bool
    isAvx2Enabled dflags = avx2 dflags || avx512f dflags

    isAvx512cdEnabled :: DynFlags -> Bool
    isAvx512cdEnabled dflags = avx512cd dflags

    isAvx512erEnabled :: DynFlags -> Bool
    isAvx512erEnabled dflags = avx512er dflags

    isAvx512fEnabled :: DynFlags -> Bool
    isAvx512fEnabled dflags = avx512f dflags

    isAvx512pfEnabled :: DynFlags -> Bool
    isAvx512pfEnabled dflags = avx512pf dflags

    -- -----------------------------------------------------------------------------
    -- Linker/compiler information

    -- LinkerInfo contains any extra options needed by the system linker.
    data LinkerInfo
      = GnuLD    [Option]
      | GnuGold  [Option]
      | DarwinLD [Option]
      | SolarisLD [Option]
      | UnknownLD
      deriving Eq

    -- CompilerInfo tells us which C compiler we're using
    data CompilerInfo
       = GCC
       | Clang
       | AppleClang
       | AppleClang51
       | UnknownCC
       deriving Eq

    -- -----------------------------------------------------------------------------
    -- RTS hooks

    -- Convert sizes like "3.5M" into integers
    decodeSize :: String -> Integer
    decodeSize str
      | c == ""      = truncate n
      | c == "K" || c == "k" = truncate (n * 1000)
      | c == "M" || c == "m" = truncate (n * 1000 * 1000)
      | c == "G" || c == "g" = truncate (n * 1000 * 1000 * 1000)
      | otherwise            = throwGhcException (CmdLineError ("can't decode size: " ++ str))
      where (m, c) = span pred str
            n      = readRational m
            pred c = isDigit c || c == '.'

    foreign import ccall unsafe "setHeapSize"       setHeapSize       :: Int -> IO ()
    foreign import ccall unsafe "enableTimingStats" enableTimingStats :: IO ()