{-# LANGUAGE CPP #-}
{-# LANGUAGE FlexibleInstances #-}

-------------------------------------------------------------------------------
--
-- | 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(..), WarnReason(..),
        Language(..),
        PlatformConstants(..),
        FatalMessager, LogAction, LogFinaliser, FlushOut(..), FlushErr(..),
        ProfAuto(..),
        glasgowExtsFlags,
        warningGroups, warningHierarchies,
        hasPprDebug, hasNoDebugOutput, hasNoStateHack, hasNoOptCoercion,
        dopt, dopt_set, dopt_unset,
        gopt, gopt_set, gopt_unset, setGeneralFlag', unSetGeneralFlag',
        wopt, wopt_set, wopt_unset,
        wopt_fatal,
        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(..),
        packageFlagsChanged,
        IgnorePackageFlag(..), TrustFlag(..),
        PackageDBFlag(..), PkgConfRef(..),
        Option(..), showOpt,
        DynLibLoader(..),
        fFlags, fLangFlags, xFlags,
        wWarningFlags,
        dynFlagDependencies,
        tablesNextToCode, mkTablesNextToCode,
        makeDynFlagsConsistent,
        shouldUseColor,

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

        thisPackage, thisComponentId, thisUnitIdInsts,

        -- ** Log output
        putLogMsg,

        -- ** 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_windres, pgm_libtool, pgm_lo, pgm_lc, pgm_i,
        opt_L, opt_P, opt_F, opt_c, opt_a, opt_l, opt_i,
        opt_windres, opt_lo, opt_lc,


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

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

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

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

        supportedLanguagesAndExtensions,
        languageExtensions,

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

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

        rtsIsProfiled,
        dynamicGhc,

#include "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, emptyPackageState)
import DriverPhases     ( Phase(..), phaseInputExt )
import Config
import CmdLineParser
import Constants
import Panic
import qualified PprColour as Col
import Util
import Maybes
import MonadUtils
import qualified Pretty
import SrcLoc
import BasicTypes       ( IntWithInf, treatZeroAsInf )
import FastString
import Outputable
import Foreign.C        ( CInt(..) )
import System.IO.Unsafe ( unsafeDupablePerformIO )
import {-# SOURCE #-} ErrUtils ( Severity(..), MsgDoc, mkLocMessageAnn
                               , getCaretDiagnostic, dumpSDoc )
import Json
import SysTools.Terminal ( stderrSupportsAnsiColors )

import System.IO.Unsafe ( unsafePerformIO )
import Data.IORef
import Control.Arrow ((&&&))
import Control.Monad
import Control.Monad.Trans.Class
import Control.Monad.Trans.Writer
import Control.Monad.Trans.Reader
import Control.Monad.Trans.Except
import Control.Exception (throwIO)

import Data.Ord
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, lookupEnv)
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)
import qualified GHC.LanguageExtensions as LangExt

import Foreign (Ptr) -- needed for 2nd stage

-- 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 generated from the modules in
--    utils/mkUserGuidePart/Options
--
--  * Flag description in docs/users_guide/using.rst 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.

-- Note [Adding a language extension]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--
-- There are a few steps to adding (or removing) a language extension,
--
--  * Adding the extension to GHC.LanguageExtensions
--
--    The Extension type in libraries/ghc-boot-th/GHC/LanguageExtensions/Type.hs
--    is the canonical list of language extensions known by GHC.
--
--  * Adding a flag to DynFlags.xFlags
--
--    This is fairly self-explanatory. The name should be concise, memorable,
--    and consistent with any previous implementations of the similar idea in
--    other Haskell compilers.
--
--  * Adding the flag to the documentation
--
--    This is the same as any other flag. See
--    Note [Updating flag description in the User's Guide]
--
--  * Adding the flag to Cabal
--
--    The Cabal library has its own list of all language extensions supported
--    by all major compilers. This is the list that user code being uploaded
--    to Hackage is checked against to ensure language extension validity.
--    Consequently, it is very important that this list remains up-to-date.
--
--    To this end, there is a testsuite test (testsuite/tests/driver/T4437.hs)
--    whose job it is to ensure these GHC's extensions are consistent with
--    Cabal.
--
--    The recommended workflow is,
--
--     1. Temporarily add your new language extension to the
--        expectedGhcOnlyExtensions list in T4437 to ensure the test doesn't
--        break while Cabal is updated.
--
--     2. After your GHC change is accepted, submit a Cabal pull request adding
--        your new extension to Cabal's list (found in
--        Cabal/Language/Haskell/Extension.hs).
--
--     3. After your Cabal change is accepted, let the GHC developers know so
--        they can update the Cabal submodule and remove the extensions from
--        expectedGhcOnlyExtensions.
--
--  * Adding the flag to the GHC Wiki
--
--    There is a change log tracking language extension additions and removals
--    on the GHC wiki:  https://ghc.haskell.org/trac/ghc/wiki/LanguagePragmaHistory
--
--  See Trac #4437 and #8176.

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

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

   -- debugging flags
   = Opt_D_dump_cmm
   | Opt_D_dump_cmm_from_stg
   | Opt_D_dump_cmm_raw
   | Opt_D_dump_cmm_verbose
   -- All of the cmm subflags (there are a lot!) automatically
   -- enabled if you run -ddump-cmm-verbose
   -- Each flag corresponds to exact stage of Cmm pipeline.
   | Opt_D_dump_cmm_cfg
   | Opt_D_dump_cmm_cbe
   | Opt_D_dump_cmm_switch
   | Opt_D_dump_cmm_proc
   | Opt_D_dump_cmm_sp
   | Opt_D_dump_cmm_sink
   | Opt_D_dump_cmm_caf
   | 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_parsed_ast
   | Opt_D_dump_rn
   | Opt_D_dump_rn_ast
   | Opt_D_dump_shape
   | 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_str_signatures
   | Opt_D_dump_tc
   | Opt_D_dump_tc_ast
   | 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_ec_trace -- Pattern match exhaustiveness checker
   | 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
   | Opt_D_dump_json
   | Opt_D_ppr_debug
   | Opt_D_no_debug_output
   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_ShowWarnGroups                 -- Show the group a warning belongs to
   | Opt_HideSourcePaths                -- Hide module source/object paths

   | Opt_PrintExplicitForalls
   | Opt_PrintExplicitKinds
   | Opt_PrintExplicitCoercions
   | Opt_PrintExplicitRuntimeReps
   | Opt_PrintEqualityRelations
   | Opt_PrintUnicodeSyntax
   | Opt_PrintExpandedSynonyms
   | Opt_PrintPotentialInstances
   | Opt_PrintTypecheckerElaboration

   -- optimisation opts
   | Opt_CallArity
   | Opt_Strictness
   | Opt_LateDmdAnal
   | Opt_KillAbsence
   | Opt_KillOneShot
   | Opt_FullLaziness
   | Opt_FloatIn
   | Opt_Specialise
   | Opt_SpecialiseAggressively
   | Opt_CrossModuleSpecialise
   | Opt_StaticArgumentTransformation
   | Opt_CSE
   | Opt_StgCSE
   | Opt_LiberateCase
   | Opt_SpecConstr
   | Opt_SpecConstrKeen
   | Opt_DoLambdaEtaExpansion
   | Opt_IgnoreAsserts
   | Opt_DoEtaReduction
   | Opt_CaseMerge
   | Opt_CaseFolding                    -- Constant folding through case-expressions
   | 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_LlvmFillUndefWithGarbage       -- Testing for undef bugs (hidden flag)
   | Opt_IrrefutableTuples
   | Opt_CmmSink
   | Opt_CmmElimCommonBlocks
   | Opt_OmitYields
   | 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]
   | Opt_CprAnal
   | Opt_WorkerWrapper
   | Opt_SolveConstantDicts

   -- 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_SplitSections
   | Opt_StgStats
   | Opt_HideAllPackages
   | Opt_HideAllPluginPackages
   | Opt_PrintBindResult
   | Opt_Haddock
   | Opt_HaddockOptions
   | Opt_BreakOnException
   | Opt_BreakOnError
   | Opt_PrintEvldWithShow
   | Opt_PrintBindContents
   | Opt_GenManifest
   | Opt_EmbedManifest
   | Opt_SharedImplib
   | Opt_BuildingCabalPackage
   | Opt_IgnoreDotGhci
   | Opt_GhciSandbox
   | Opt_GhciHistory
   | Opt_LocalGhciHistory
   | Opt_HelpfulErrors
   | Opt_DeferTypeErrors
   | Opt_DeferTypedHoles
   | Opt_DeferOutOfScopeVariables
   | Opt_PIC
   | Opt_SccProfilingOn
   | Opt_Ticky
   | Opt_Ticky_Allocd
   | Opt_Ticky_LNE
   | Opt_Ticky_Dyn_Thunk
   | Opt_RPath
   | Opt_RelativeDynlibPaths
   | Opt_Hpc
   | Opt_FlatCache
   | Opt_ExternalInterpreter
   | Opt_OptimalApplicativeDo
   | Opt_VersionMacros
   | Opt_WholeArchiveHsLibs

   -- 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_DiagnosticsShowCaret -- Show snippets of offending code
   | Opt_PprCaseAsLet
   | Opt_PprShowTicks
   | Opt_ShowHoleConstraints

   -- 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_SuppressUnfoldings
   -- Suppress the details of even stable unfoldings
   | Opt_SuppressTypeSignatures
   -- Suppress unique ids on variables.
   -- Except for uniques, as some simplifier phases introduce new
   -- variables that have otherwise identical names.
   | Opt_SuppressUniques
   | Opt_SuppressTicks     -- Replaces Opt_PprShowTicks

   -- temporary flags
   | Opt_AutoLinkPackages
   | Opt_ImplicitImportQualified

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

   | Opt_BuildDynamicToo

   -- safe haskell flags
   | Opt_DistrustAllPackages
   | Opt_PackageTrust

   | Opt_G_NoStateHack
   | Opt_G_NoOptCoercion
   deriving (Eq, Show, Enum)

-- | Used when outputting warnings: if a reason is given, it is
-- displayed. If a warning isn't controlled by a flag, this is made
-- explicit at the point of use.
data WarnReason = NoReason | Reason !WarningFlag
  deriving Show

instance Outputable WarnReason where
  ppr = text . show

instance ToJson WarnReason where
  json NoReason = JSNull
  json (Reason wf) = JSString (show wf)

data WarningFlag =
-- See Note [Updating flag description in the User's Guide]
     Opt_WarnDuplicateExports
   | Opt_WarnDuplicateConstraints
   | Opt_WarnRedundantConstraints
   | Opt_WarnHiShadows
   | Opt_WarnImplicitPrelude
   | Opt_WarnIncompletePatterns
   | Opt_WarnIncompleteUniPatterns
   | Opt_WarnIncompletePatternsRecUpd
   | Opt_WarnOverflowedLiterals
   | Opt_WarnEmptyEnumerations
   | Opt_WarnMissingFields
   | Opt_WarnMissingImportList
   | Opt_WarnMissingMethods
   | Opt_WarnMissingSignatures
   | Opt_WarnMissingLocalSignatures
   | Opt_WarnNameShadowing
   | Opt_WarnOverlappingPatterns
   | Opt_WarnTypeDefaults
   | Opt_WarnMonomorphism
   | Opt_WarnUnusedTopBinds
   | Opt_WarnUnusedLocalBinds
   | Opt_WarnUnusedPatternBinds
   | Opt_WarnUnusedImports
   | Opt_WarnUnusedMatches
   | Opt_WarnUnusedTypePatterns
   | Opt_WarnUnusedForalls
   | Opt_WarnWarningsDeprecations
   | Opt_WarnDeprecatedFlags
   | Opt_WarnAMP -- Introduced in GHC 7.8, obsolete since 7.10
   | Opt_WarnMissingMonadFailInstances -- since 8.0
   | Opt_WarnSemigroup -- since 8.0
   | 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_WarnMissedSpecs
   | Opt_WarnAllMissedSpecs
   | Opt_WarnUnsupportedCallingConventions
   | Opt_WarnUnsupportedLlvmVersion
   | Opt_WarnInlineRuleShadowing
   | Opt_WarnTypedHoles
   | Opt_WarnPartialTypeSignatures
   | Opt_WarnMissingExportedSignatures
   | Opt_WarnUntickedPromotedConstructors
   | Opt_WarnDerivingTypeable
   | Opt_WarnDeferredTypeErrors
   | Opt_WarnDeferredOutOfScopeVariables
   | Opt_WarnNonCanonicalMonadInstances   -- since 8.0
   | Opt_WarnNonCanonicalMonadFailInstances -- since 8.0
   | Opt_WarnNonCanonicalMonoidInstances  -- since 8.0
   | Opt_WarnMissingPatternSynonymSignatures -- since 8.0
   | Opt_WarnUnrecognisedWarningFlags     -- since 8.0
   | Opt_WarnSimplifiableClassConstraints -- Since 8.2
   | Opt_WarnCPPUndef                     -- Since 8.2
   | Opt_WarnUnbangedStrictPatterns       -- Since 8.2
   | Opt_WarnMissingHomeModules           -- Since 8.2
   deriving (Eq, Show, Enum)

data Language = Haskell98 | Haskell2010
   deriving (Eq, Enum, Show)

instance Outputable Language where
    ppr = text . show

-- | 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

-- | 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,
  verbosity             :: Int,         -- ^ Verbosity level: see Note [Verbosity levels]
  optLevel              :: Int,         -- ^ Optimisation level
  debugLevel            :: Int,         -- ^ How much debug information to produce
  simplPhases           :: Int,         -- ^ Number of simplifier phases
  maxSimplIterations    :: Int,         -- ^ Max simplifier iterations
  maxPmCheckIterations  :: Int,         -- ^ Max no iterations for pm checking
  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
  maxUncoveredPatterns  :: Int,         -- ^ Maximum number of unmatched patterns to show
                                        --   in non-exhaustiveness warnings
  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,         -- ^ Simplification history size

  importPaths           :: [FilePath],
  mainModIs             :: Module,
  mainFunIs             :: Maybe String,
  reductionDepth        :: IntWithInf,   -- ^ Typechecker maximum stack depth
  solverIterations      :: IntWithInf,   -- ^ Number of iterations in the constraints solver
                                         --   Typically only 1 is needed

  thisInstalledUnitId   :: InstalledUnitId,
  thisComponentId_      :: Maybe ComponentId,
  thisUnitIdInsts_      :: Maybe [(ModuleName, Module)],

  -- 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,
  rtsOptsSuggestions    :: Bool,

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

  -- Plugins
  pluginModNames        :: [ModuleName],
  pluginModNameOpts     :: [(ModuleName,String)],
  frontendPluginOpts    :: [String],
    -- ^ the @-ffrontend-opt@ flags given on the command line, in *reverse*
    -- order that they're specified on the command line.

  -- GHC API hooks
  hooks                 :: Hooks,

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

  --  Package flags
  packageDBFlags        :: [PackageDBFlag],
        -- ^ The @-package-db@ flags given on the command line, In
        -- *reverse* order that they're specified on the command line.
        -- This is intended to be applied with the list of "initial"
        -- package databases derived from @GHC_PACKAGE_PATH@; see
        -- 'getPackageConfRefs'.

  ignorePackageFlags    :: [IgnorePackageFlag],
        -- ^ The @-ignore-package@ flags from the command line.
        -- In *reverse* order that they're specified on the command line.
  packageFlags          :: [PackageFlag],
        -- ^ The @-package@ and @-hide-package@ flags from the command-line.
        -- In *reverse* order that they're specified on the command line.
  pluginPackageFlags    :: [PackageFlag],
        -- ^ The @-plugin-package-id@ flags from command line.
        -- In *reverse* order that they're specified on the command line.
  trustFlags            :: [TrustFlag],
        -- ^ The @-trust@ and @-distrust@ flags.
        -- In *reverse* order that they're specified on 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
  pkgDatabase           :: Maybe [(FilePath, [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,
  fatalWarningFlags     :: 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 LangExt.Extension],
  -- extensionFlags should always be equal to
  --     flattenExtensionFlags language extensions
  -- LangExt.Extension is defined in libraries/ghc-boot so that it can be used
  -- by template-haskell
  extensionFlags        :: IntSet,

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

  maxWorkerArgs         :: Int,

  ghciHistSize          :: Int,

  -- | MsgDoc output action: use "ErrUtils" instead of this if you can
  initLogAction         :: IO (Maybe LogOutput),
  log_action            :: LogAction,
  log_finaliser         :: LogFinaliser,
  flushOut              :: FlushOut,
  flushErr              :: FlushErr,

  haddockOptions        :: Maybe String,

  -- | GHCi scripts specified by -ghci-script, in reverse order
  ghciScripts           :: [String],

  -- Output style options
  pprUserLength         :: Int,
  pprCols               :: Int,

  useUnicode            :: Bool,
  useColor              :: OverridingBool,
  canUseColor           :: Bool,
  colScheme             :: Col.Scheme,

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

  interactivePrint      :: Maybe String,

  nextWrapperNum        :: IORef (ModuleEnv Int),

  -- | Machine dependent 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,

  -- | Reverse the order of error messages in GHC/GHCi
  reverseErrors         :: Bool,

  -- | Limit the maximum number of errors to show
  maxErrors             :: Maybe Int,

  -- | Unique supply configuration for testing build determinism
  initialUnique         :: Int,
  uniqueIncrement       :: Int
}

class HasDynFlags m where
    getDynFlags :: m DynFlags

{- It would be desirable to have the more generalised

  instance (MonadTrans t, Monad m, HasDynFlags m) => HasDynFlags (t m) where
      getDynFlags = lift getDynFlags

instance definition. However, that definition would overlap with the
`HasDynFlags (GhcT m)` instance. Instead we define instances for a
couple of common Monad transformers explicitly. -}

instance (Monoid a, Monad m, HasDynFlags m) => HasDynFlags (WriterT a m) where
    getDynFlags = lift getDynFlags

instance (Monad m, HasDynFlags m) => HasDynFlags (ReaderT a m) where
    getDynFlags = lift getDynFlags

instance (Monad m, HasDynFlags m) => HasDynFlags (MaybeT m) where
    getDynFlags = lift getDynFlags

instance (Monad m, HasDynFlags m) => HasDynFlags (ExceptT e m) where
    getDynFlags = lift getDynFlags

class ContainsDynFlags t where
    extractDynFlags :: t -> DynFlags

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,
  sGccSupportsNoPie        :: 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_windres           :: String,
  sPgm_libtool           :: String,
  sPgm_lo                :: (String,[Option]), -- LLVM: opt llvm optimiser
  sPgm_lc                :: (String,[Option]), -- LLVM: llc static compiler
  sPgm_i                 :: String,
  -- 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
  sOpt_i                 :: [String], -- iserv options

  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_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)
pgm_i                 :: DynFlags -> String
pgm_i dflags = sPgm_i (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)
opt_i                 :: DynFlags -> [String]
opt_i dflags = sOpt_i (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 -> MaybeT IO FilePath
versionedAppDir dflags = do
  -- Make sure we handle the case the HOME isn't set (see #11678)
  appdir <- tryMaybeT $ getAppUserDataDirectory (programName dflags)
  return $ appdir </> versionedFilePath dflags

-- | A filepath like @x86_64-linux-7.6.3@ with the platform string to use when
-- constructing platform-version-dependent files that need to co-exist.
--
versionedFilePath :: DynFlags -> FilePath
versionedFilePath dflags =     TARGET_ARCH
                        ++ '-':TARGET_OS
                        ++ '-':projectVersion dflags
  -- NB: This functionality is reimplemented in Cabal, so if you
  -- change it, be sure to update Cabal.

-- | 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 = text "CompManager"
  ppr OneShot     = text "OneShot"
  ppr MkDepend    = text "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

-- | We accept flags which make packages visible, but how they select
-- the package varies; this data type reflects what selection criterion
-- is used.
data PackageArg =
      PackageArg String    -- ^ @-package@, by 'PackageName'
    | UnitIdArg UnitId     -- ^ @-package-id@, by 'UnitId'
  deriving (Eq, Show)
instance Outputable PackageArg where
    ppr (PackageArg pn) = text "package" <+> text pn
    ppr (UnitIdArg uid) = text "unit" <+> ppr uid

-- | Represents the renaming that may be associated with an exposed
-- package, e.g. the @rns@ part of @-package "foo (rns)"@.
--
-- Here are some example parsings of the package flags (where
-- a string literal is punned to be a 'ModuleName':
--
--      * @-package foo@ is @ModRenaming True []@
--      * @-package foo ()@ is @ModRenaming False []@
--      * @-package foo (A)@ is @ModRenaming False [("A", "A")]@
--      * @-package foo (A as B)@ is @ModRenaming False [("A", "B")]@
--      * @-package foo with (A as B)@ is @ModRenaming True [("A", "B")]@
data ModRenaming = ModRenaming {
    modRenamingWithImplicit :: Bool, -- ^ Bring all exposed modules into scope?
    modRenamings :: [(ModuleName, ModuleName)] -- ^ Bring module @m@ into scope
                                               --   under name @n@.
  } deriving (Eq)
instance Outputable ModRenaming where
    ppr (ModRenaming b rns) = ppr b <+> parens (ppr rns)

-- | Flags for manipulating the set of non-broken packages.
newtype IgnorePackageFlag = IgnorePackage String -- ^ @-ignore-package@
  deriving (Eq)

-- | Flags for manipulating package trust.
data TrustFlag
  = TrustPackage    String -- ^ @-trust@
  | DistrustPackage String -- ^ @-distrust@
  deriving (Eq)

-- | Flags for manipulating packages visibility.
data PackageFlag
  = ExposePackage   String PackageArg ModRenaming -- ^ @-package@, @-package-id@
  | HidePackage     String -- ^ @-hide-package@
  deriving (Eq) -- NB: equality instance is used by packageFlagsChanged

data PackageDBFlag
  = PackageDB PkgConfRef
  | NoUserPackageDB
  | NoGlobalPackageDB
  | ClearPackageDBs
  deriving (Eq)

packageFlagsChanged :: DynFlags -> DynFlags -> Bool
packageFlagsChanged idflags1 idflags0 =
  packageFlags idflags1 /= packageFlags idflags0 ||
  ignorePackageFlags idflags1 /= ignorePackageFlags idflags0 ||
  pluginPackageFlags idflags1 /= pluginPackageFlags idflags0 ||
  trustFlags idflags1 /= trustFlags idflags0 ||
  packageDBFlags idflags1 /= packageDBFlags idflags0 ||
  packageGFlags idflags1 /= packageGFlags idflags0
 where
   packageGFlags dflags = map (`gopt` dflags)
     [ Opt_HideAllPackages
     , Opt_HideAllPluginPackages
     , Opt_AutoLinkPackages ]

instance Outputable PackageFlag where
    ppr (ExposePackage n arg rn) = text n <> braces (ppr arg <+> ppr rn)
    ppr (HidePackage str) = text "-hide-package" <+> text str

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)

shouldUseColor :: DynFlags -> Bool
shouldUseColor dflags = overrideWith (canUseColor dflags) (useColor dflags)

-----------------------------------------------------------------------------
-- 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
  | 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
        WayThreaded `allowedWith` WayProf       = True
        WayThreaded `allowedWith` WayEventLog   = True
        WayProf     `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"

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

wayDesc :: Way -> String
wayDesc (WayCustom xs) = xs
wayDesc WayThreaded = "Threaded"
wayDesc WayDebug    = "Debug"
wayDesc WayDyn      = "Dynamic"
wayDesc WayProf     = "Profiling"
wayDesc WayEventLog = "RTS Event Logging"

-- 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 = []

-- 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,
                                      -- If splitobjs wasn't useful for this,
                                      -- assume sections aren't either.
                                      Opt_SplitSections]
wayUnsetGeneralFlags _ WayProf     = []
wayUnsetGeneralFlags _ WayEventLog = []

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"]

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   = []

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

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
 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
 canUseColor <- stderrSupportsAnsiColors
 maybeGhcColorsEnv  <- lookupEnv "GHC_COLORS"
 maybeGhcColoursEnv <- lookupEnv "GHC_COLOURS"
 let adjustCols (Just env) = Col.parseScheme env
     adjustCols Nothing    = id
 let (useColor', colScheme') =
       (adjustCols maybeGhcColoursEnv . adjustCols maybeGhcColorsEnv)
       (useColor dflags, colScheme dflags)
 return dflags{
        canGenerateDynamicToo = refCanGenerateDynamicToo,
        nextTempSuffix = refNextTempSuffix,
        filesToClean   = refFilesToClean,
        dirsToClean    = refDirsToClean,
        filesToNotIntermediateClean = refFilesToNotIntermediateClean,
        generatedDumps = refGeneratedDumps,
        nextWrapperNum = wrapperNum,
        useUnicode    = canUseUnicode,
        useColor      = useColor',
        canUseColor   = canUseColor,
        colScheme     = colScheme',
        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),
        verbosity               = 0,
        optLevel                = 0,
        debugLevel              = 0,
        simplPhases             = 2,
        maxSimplIterations      = 4,
        maxPmCheckIterations    = 2000000,
        ruleCheck               = Nothing,
        maxRelevantBinds        = Just 6,
        maxUncoveredPatterns    = 4,
        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,

        importPaths             = ["."],
        mainModIs               = mAIN,
        mainFunIs               = Nothing,
        reductionDepth          = treatZeroAsInf mAX_REDUCTION_DEPTH,
        solverIterations        = treatZeroAsInf mAX_SOLVER_ITERATIONS,

        thisInstalledUnitId     = toInstalledUnitId mainUnitId,
        thisUnitIdInsts_        = Nothing,
        thisComponentId_        = Nothing,

        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       = [],
        frontendPluginOpts      = [],
        hooks                   = emptyHooks,

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

        hpcDir                  = ".hpc",

        packageDBFlags          = [],
        packageFlags            = [],
        pluginPackageFlags      = [],
        ignorePackageFlags      = [],
        trustFlags              = [],
        packageEnv              = Nothing,
        pkgDatabase             = Nothing,
        -- This gets filled in with GHC.setSessionDynFlags
        pkgState                = emptyPackageState,
        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),
        fatalWarningFlags = IntSet.empty,
        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 function if that means
        -- we'll be able to pick the right method from a dictionary
        ufDictDiscount      = 30,
        ufKeenessFactor     = 1.5,
        ufDearOp            = 40,
        ufVeryAggressive    = False,

        maxWorkerArgs = 10,

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

        -- Logging

        initLogAction = defaultLogOutput,

        log_action = defaultLogAction,
        log_finaliser = \ _ -> return (),

        flushOut = defaultFlushOut,
        flushErr = defaultFlushErr,
        pprUserLength = 5,
        pprCols = 100,
        useUnicode = False,
        useColor = Auto,
        canUseColor = False,
        colScheme = Col.defaultScheme,
        profAuto = NoProfAuto,
        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,

        initialUnique = 0,
        uniqueIncrement = 1,

        reverseErrors = False,
        maxErrors     = Nothing
      }

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

interpWays :: [Way]
interpWays
  | dynamicGhc = [WayDyn]
  | rtsIsProfiled = [WayProf]
  | otherwise = []

interpreterProfiled :: DynFlags -> Bool
interpreterProfiled dflags
  | gopt Opt_ExternalInterpreter dflags = gopt Opt_SccProfilingOn dflags
  | otherwise = rtsIsProfiled

interpreterDynamic :: DynFlags -> Bool
interpreterDynamic dflags
  | gopt Opt_ExternalInterpreter dflags = WayDyn `elem` ways dflags
  | otherwise = dynamicGhc

--------------------------------------------------------------------------
--
-- Note [JSON Error Messages]
--
-- When the user requests the compiler output to be dumped as json
-- we modify the log_action to collect all the messages in an IORef
-- and then finally in GHC.withCleanupSession the log_finaliser is
-- called which prints out the messages together.
--
-- Before the compiler calls log_action, it has already turned the `ErrMsg`
-- into a formatted message. This means that we lose some possible
-- information to provide to the user but refactoring log_action is quite
-- invasive as it is called in many places. So, for now I left it alone
-- and we can refine its behaviour as users request different output.

type FatalMessager = String -> IO ()

data LogOutput = LogOutput
               { getLogAction :: LogAction
               , getLogFinaliser :: LogFinaliser
               }

defaultLogOutput :: IO (Maybe LogOutput)
defaultLogOutput = return $ Nothing

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

type LogFinaliser = DynFlags -> IO ()

defaultFatalMessager :: FatalMessager
defaultFatalMessager = hPutStrLn stderr


-- See Note [JSON Error Messages]
jsonLogOutput :: IO (Maybe LogOutput)
jsonLogOutput = do
  ref <- newIORef []
  return . Just $ LogOutput (jsonLogAction ref) (jsonLogFinaliser ref)

jsonLogAction :: IORef [SDoc] -> LogAction
jsonLogAction iref dflags reason severity srcSpan style msg
  = do
      addMessage . withPprStyle (mkCodeStyle CStyle) . renderJSON $
        JSObject [ ( "span", json srcSpan )
                 , ( "doc" , JSString (showSDoc dflags msg) )
                 , ( "severity", json severity )
                 , ( "reason" ,   json reason )
                ]
      defaultLogAction dflags reason severity srcSpan style msg
  where
    addMessage m = modifyIORef iref (m:)


jsonLogFinaliser :: IORef [SDoc] -> DynFlags -> IO ()
jsonLogFinaliser iref dflags = do
  msgs <- readIORef iref
  let fmt_msgs = brackets $ pprWithCommas (blankLine $$) msgs
  output fmt_msgs
  where
    -- dumpSDoc uses log_action to output the dump
    dflags' = dflags { log_action = defaultLogAction }
    output doc = dumpSDoc dflags' neverQualify Opt_D_dump_json "" doc


defaultLogAction :: LogAction
defaultLogAction dflags reason severity srcSpan style msg
    = case severity of
      SevOutput      -> printOut msg style
      SevDump        -> printOut (msg $$ blankLine) style
      SevInteractive -> putStrSDoc msg style
      SevInfo        -> printErrs msg style
      SevFatal       -> printErrs msg style
      _              -> do -- otherwise (i.e. SevError or SevWarning)
                           hPutChar stderr '\n'
                           caretDiagnostic <-
                               if gopt Opt_DiagnosticsShowCaret dflags
                               then getCaretDiagnostic severity srcSpan
                               else pure empty
                           printErrs (message $+$ caretDiagnostic)
                               (setStyleColoured True 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 printOut   = defaultLogActionHPrintDoc  dflags stdout
          printErrs  = defaultLogActionHPrintDoc  dflags stderr
          putStrSDoc = defaultLogActionHPutStrDoc dflags stdout
          -- Pretty print the warning flag, if any (#10752)
          message = mkLocMessageAnn flagMsg severity srcSpan msg
          flagMsg = case reason of
                        NoReason -> Nothing
                        Reason flag -> (\spec -> "-W" ++ flagSpecName spec ++ flagGrp flag) <$>
                                          flagSpecOf flag

          flagGrp flag
              | gopt Opt_ShowWarnGroups dflags =
                    case smallestGroups flag of
                        [] -> ""
                        groups -> " (in " ++ intercalate ", " (map ("-W"++) groups) ++ ")"
              | otherwise = ""

-- | Like 'defaultLogActionHPutStrDoc' but appends an extra newline.
defaultLogActionHPrintDoc :: DynFlags -> Handle -> SDoc -> PprStyle -> IO ()
defaultLogActionHPrintDoc dflags h d sty
 = defaultLogActionHPutStrDoc dflags h (d $$ text "") sty

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

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
  deriving (Eq, Show)

instance Outputable a => Outputable (OnOff a) where
  ppr (On x)  = text "On" <+> ppr x
  ppr (Off x) = text "Off" <+> ppr x

-- OnOffs accumulate in reverse order, so we use foldr in order to
-- process them in the right order
flattenExtensionFlags :: Maybe Language -> [OnOff LangExt.Extension] -> 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 -> [LangExt.Extension]

languageExtensions Nothing
    -- Nothing => the default case
    = LangExt.NondecreasingIndentation -- This has been on by default for some time
    : delete LangExt.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)
    = [LangExt.ImplicitPrelude,
       LangExt.MonomorphismRestriction,
       LangExt.NPlusKPatterns,
       LangExt.DatatypeContexts,
       LangExt.TraditionalRecordSyntax,
       LangExt.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)
    = [LangExt.ImplicitPrelude,
       LangExt.MonomorphismRestriction,
       LangExt.DatatypeContexts,
       LangExt.TraditionalRecordSyntax,
       LangExt.EmptyDataDecls,
       LangExt.ForeignFunctionInterface,
       LangExt.PatternGuards,
       LangExt.DoAndIfThenElse,
       LangExt.RelaxedPolyRec]

hasPprDebug :: DynFlags -> Bool
hasPprDebug = dopt Opt_D_ppr_debug

hasNoDebugOutput :: DynFlags -> Bool
hasNoDebugOutput = dopt Opt_D_no_debug_output

hasNoStateHack :: DynFlags -> Bool
hasNoStateHack = gopt Opt_G_NoStateHack

hasNoOptCoercion :: DynFlags -> Bool
hasNoOptCoercion = gopt Opt_G_NoOptCoercion


-- | 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_shape                  = 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 Opt_D_dump_ec_trace               = 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 'WarningFlag' is set as fatal
wopt_fatal :: WarningFlag -> DynFlags -> Bool
wopt_fatal f dflags = fromEnum f `IntSet.member` fatalWarningFlags dflags

-- | Mark a 'WarningFlag' as fatal (do not set the flag)
wopt_set_fatal :: DynFlags -> WarningFlag -> DynFlags
wopt_set_fatal dfs f
    = dfs { fatalWarningFlags =
              IntSet.insert (fromEnum f) (fatalWarningFlags dfs) }

-- | Mark a 'WarningFlag' as not fatal
wopt_unset_fatal :: DynFlags -> WarningFlag -> DynFlags
wopt_unset_fatal dfs f
    = dfs { fatalWarningFlags =
              IntSet.delete (fromEnum f) (fatalWarningFlags dfs) }

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

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

-- | Unset a 'LangExt.Extension'
xopt_unset :: DynFlags -> LangExt.Extension -> 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)
          }

-- | An internal helper to check whether to use unicode syntax for output.
--
-- Note: You should very likely be using 'Outputable.unicodeSyntax' instead
-- of this function.
useUnicodeSyntax :: DynFlags -> Bool
useUnicodeSyntax = gopt Opt_PrintUnicodeSyntax

-- | 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 >> pure a
    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 LangExt.GeneralizedNewtypeDeriving,
                    flip xopt_unset LangExt.GeneralizedNewtypeDeriving)
              , ("-XTemplateHaskell", thOnLoc,
                    xopt LangExt.TemplateHaskell,
                    flip xopt_unset LangExt.TemplateHaskell)
              ]
unsafeFlagsForInfer = unsafeFlags


-- | 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}

setJsonLogAction :: DynFlags -> DynFlags
setJsonLogAction d = d { initLogAction = jsonLogOutput }

thisComponentId :: DynFlags -> ComponentId
thisComponentId dflags =
  case thisComponentId_ dflags of
    Just cid -> cid
    Nothing  ->
      case thisUnitIdInsts_ dflags of
        Just _  ->
          throwGhcException $ CmdLineError ("Use of -instantiated-with requires -this-component-id")
        Nothing -> ComponentId (unitIdFS (thisPackage dflags))

thisUnitIdInsts :: DynFlags -> [(ModuleName, Module)]
thisUnitIdInsts dflags =
    case thisUnitIdInsts_ dflags of
        Just insts -> insts
        Nothing    -> []

thisPackage :: DynFlags -> UnitId
thisPackage dflags =
    case thisUnitIdInsts_ dflags of
        Nothing -> default_uid
        Just insts
          | all (\(x,y) -> mkHoleModule x == y) insts
          -> newUnitId (thisComponentId dflags) insts
          | otherwise
          -> default_uid
  where
    default_uid = DefiniteUnitId (DefUnitId (thisInstalledUnitId dflags))

parseUnitIdInsts :: String -> [(ModuleName, Module)]
parseUnitIdInsts str = case filter ((=="").snd) (readP_to_S parse str) of
    [(r, "")] -> r
    _ -> throwGhcException $ CmdLineError ("Can't parse -instantiated-with: " ++ str)
  where parse = sepBy parseEntry (R.char ',')
        parseEntry = do
            n <- parseModuleName
            _ <- R.char '='
            m <- parseModuleId
            return (n, m)

setUnitIdInsts :: String -> DynFlags -> DynFlags
setUnitIdInsts s d =
    d { thisUnitIdInsts_ = Just (parseUnitIdInsts s) }

setComponentId :: String -> DynFlags -> DynFlags
setComponentId s d =
    d { thisComponentId_ = Just (ComponentId (fsLit 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

addFrontendPluginOption :: String -> DynFlags -> DynFlags
addFrontendPluginOption s d = d { frontendPluginOpts = s : frontendPluginOpts d }

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 ]

{- **********************************************************************
%*                                                                      *
                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 ()

  dflags7 <- liftIO $ setLogAction dflags6

  liftIO $ setUnsafeGlobalDynFlags dflags7

  return (dflags7, leftover, consistency_warnings ++ sh_warns ++ warns)

setLogAction :: DynFlags -> IO DynFlags
setLogAction dflags = do
 mlogger <- initLogAction dflags
 return $
    maybe
         dflags
         (\logger ->
            dflags
              { log_action    = getLogAction logger
              , log_finaliser = getLogFinaliser logger
              , initLogAction = return $ Nothing -- Don't initialise it twice
              })
         mlogger

-- | Write an error or warning to the 'LogOutput'.
putLogMsg :: DynFlags -> WarnReason -> Severity -> SrcSpan -> PprStyle
          -> MsgDoc -> IO ()
putLogMsg dflags = log_action dflags dflags

updateWays :: DynFlags -> DynFlags
updateWays dflags
    = let theWays = sort $ nub $ ways dflags
      in 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"]

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


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

-- | All dynamic flags option strings without the deprecated ones.
-- These are the user facing strings for enabling and disabling options.
allNonDeprecatedFlags :: [String]
allNonDeprecatedFlags = allFlagsDeps False

-- | All flags with possibility to filter deprecated ones
allFlagsDeps :: Bool -> [String]
allFlagsDeps keepDeprecated = [ '-':flagName flag
                              | (deprecated, flag) <- flagsAllDeps
                              , ok (flagOptKind flag)
                              , keepDeprecated || not (isDeprecated deprecated)]
  where ok (PrefixPred _ _) = False
        ok _   = True
        isDeprecated Deprecated = True
        isDeprecated _ = False

{-
 - 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 = map snd flagsAllDeps

-- All dynamic flags present in GHC with deprecation information.
flagsAllDeps :: [(Deprecation, Flag (CmdLineP DynFlags))]
flagsAllDeps =  package_flags_deps ++ dynamic_flags_deps


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

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

----------------Helpers to make flags and keep deprecation information----------

type FlagMaker m = String -> OptKind m -> Flag m
type DynFlagMaker = FlagMaker (CmdLineP DynFlags)
data Deprecation = NotDeprecated | Deprecated deriving (Eq, Ord)

-- Make a non-deprecated flag
make_ord_flag :: DynFlagMaker -> String -> OptKind (CmdLineP DynFlags)
              -> (Deprecation, Flag (CmdLineP DynFlags))
make_ord_flag fm name kind = (NotDeprecated, fm name kind)

-- Make a deprecated flag
make_dep_flag :: DynFlagMaker -> String -> OptKind (CmdLineP DynFlags) -> String
                 -> (Deprecation, Flag (CmdLineP DynFlags))
make_dep_flag fm name kind message = (Deprecated,
                                      fm name $ add_dep_message kind message)

add_dep_message :: OptKind (CmdLineP DynFlags) -> String
                -> OptKind (CmdLineP DynFlags)
add_dep_message (NoArg f) message = NoArg $ f >> deprecate message
add_dep_message (HasArg f) message = HasArg $ \s -> f s >> deprecate message
add_dep_message (SepArg f) message = SepArg $ \s -> f s >> deprecate message
add_dep_message (Prefix f) message = Prefix $ \s -> f s >> deprecate message
add_dep_message (OptPrefix f) message =
                                  OptPrefix $ \s -> f s >> deprecate message
add_dep_message (OptIntSuffix f) message =
                               OptIntSuffix $ \oi -> f oi >> deprecate message
add_dep_message (IntSuffix f) message =
                                  IntSuffix $ \i -> f i >> deprecate message
add_dep_message (FloatSuffix f) message =
                                FloatSuffix $ \fl -> f fl >> deprecate message
add_dep_message (PassFlag f) message =
                                   PassFlag $ \s -> f s >> deprecate message
add_dep_message (AnySuffix f) message =
                                  AnySuffix $ \s -> f s >> deprecate message
add_dep_message (PrefixPred pred f) message =
                            PrefixPred pred $ \s -> f s >> deprecate message
add_dep_message (AnySuffixPred pred f) message =
                         AnySuffixPred pred $ \s -> f s >> deprecate message

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

  , make_ord_flag defGhcFlag "j"     (OptIntSuffix
        (\n -> case n of
                 Just n
                     | n > 0     -> upd (\d -> d { parMakeCount = Just n })
                     | otherwise -> addErr "Syntax: -j[n] where n > 0"
                 Nothing -> upd (\d -> d { parMakeCount = Nothing })))
                 -- When the number of parallel builds
                 -- is omitted, it is the same
                 -- as specifing that the number of
                 -- parallel builds is equal to the
                 -- result of getNumProcessors
  , make_ord_flag defFlag "instantiated-with"   (sepArg setUnitIdInsts)
  , make_ord_flag defFlag "this-component-id"   (sepArg setComponentId)

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

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

    ------- ways ---------------------------------------------------------------
  , make_ord_flag defGhcFlag "prof"           (NoArg (addWay WayProf))
  , make_ord_flag defGhcFlag "eventlog"       (NoArg (addWay WayEventLog))
  , make_dep_flag defGhcFlag "smp"
      (NoArg $ addWay WayThreaded) "Use -threaded instead"
  , make_ord_flag defGhcFlag "debug"          (NoArg (addWay WayDebug))
  , make_ord_flag defGhcFlag "threaded"       (NoArg (addWay WayThreaded))

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

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

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

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

  , make_ord_flag defGhcFlag "split-sections"
      (noArgM (\dflags -> do
        if platformHasSubsectionsViaSymbols (targetPlatform dflags)
          then do addErr $
                    "-split-sections is not useful on this platform " ++
                    "since it always uses subsections via symbols."
                  return dflags
          else return (gopt_set dflags Opt_SplitSections)))

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

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

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

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

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

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

        ------- Keeping temporary files -------------------------------------
     -- These can be singular (think ghc -c) or plural (think ghc --make)
  , make_ord_flag defGhcFlag "keep-hc-file"
        (NoArg (setGeneralFlag Opt_KeepHcFiles))
  , make_ord_flag defGhcFlag "keep-hc-files"
        (NoArg (setGeneralFlag Opt_KeepHcFiles))
  , make_ord_flag defGhcFlag "keep-s-file"
        (NoArg (setGeneralFlag Opt_KeepSFiles))
  , make_ord_flag defGhcFlag "keep-s-files"
        (NoArg (setGeneralFlag Opt_KeepSFiles))
  , make_ord_flag defGhcFlag "keep-llvm-file"
        (NoArg $ setObjTarget HscLlvm >> setGeneralFlag Opt_KeepLlvmFiles)
  , make_ord_flag defGhcFlag "keep-llvm-files"
        (NoArg $ setObjTarget HscLlvm >> setGeneralFlag Opt_KeepLlvmFiles)
     -- This only makes sense as plural
  , make_ord_flag defGhcFlag "keep-tmp-files"
        (NoArg (setGeneralFlag Opt_KeepTmpFiles))
  , make_ord_flag defGhcFlag "keep-hi-file"
        (NoArg (setGeneralFlag Opt_KeepHiFiles))
  , make_ord_flag defGhcFlag "no-keep-hi-file"
        (NoArg (unSetGeneralFlag Opt_KeepHiFiles))
  , make_ord_flag defGhcFlag "keep-hi-files"
        (NoArg (setGeneralFlag Opt_KeepHiFiles))
  , make_ord_flag defGhcFlag "no-keep-hi-files"
        (NoArg (unSetGeneralFlag Opt_KeepHiFiles))
  , make_ord_flag defGhcFlag "keep-o-file"
        (NoArg (setGeneralFlag Opt_KeepOFiles))
  , make_ord_flag defGhcFlag "no-keep-o-file"
        (NoArg (unSetGeneralFlag Opt_KeepOFiles))
  , make_ord_flag defGhcFlag "keep-o-files"
        (NoArg (setGeneralFlag Opt_KeepOFiles))
  , make_ord_flag defGhcFlag "no-keep-o-files"
        (NoArg (unSetGeneralFlag Opt_KeepOFiles))

        ------- Miscellaneous ----------------------------------------------
  , make_ord_flag defGhcFlag "no-auto-link-packages"
        (NoArg (unSetGeneralFlag Opt_AutoLinkPackages))
  , make_ord_flag defGhcFlag "no-hs-main"
        (NoArg (setGeneralFlag Opt_NoHsMain))
  , make_ord_flag defGhcFlag "fno-state-hack"
        (NoArg (setGeneralFlag Opt_G_NoStateHack))
  , make_ord_flag defGhcFlag "fno-opt-coercion"
        (NoArg (setGeneralFlag Opt_G_NoOptCoercion))
  , make_ord_flag defGhcFlag "with-rtsopts"
        (HasArg setRtsOpts)
  , make_ord_flag defGhcFlag "rtsopts"
        (NoArg (setRtsOptsEnabled RtsOptsAll))
  , make_ord_flag defGhcFlag "rtsopts=all"
        (NoArg (setRtsOptsEnabled RtsOptsAll))
  , make_ord_flag defGhcFlag "rtsopts=some"
        (NoArg (setRtsOptsEnabled RtsOptsSafeOnly))
  , make_ord_flag defGhcFlag "rtsopts=none"
        (NoArg (setRtsOptsEnabled RtsOptsNone))
  , make_ord_flag defGhcFlag "no-rtsopts"
        (NoArg (setRtsOptsEnabled RtsOptsNone))
  , make_ord_flag defGhcFlag "no-rtsopts-suggestions"
      (noArg (\d -> d {rtsOptsSuggestions = False}))

  , make_ord_flag defGhcFlag "main-is"              (SepArg setMainIs)
  , make_ord_flag defGhcFlag "haddock"              (NoArg (setGeneralFlag Opt_Haddock))
  , make_ord_flag defGhcFlag "haddock-opts"         (hasArg addHaddockOpts)
  , make_ord_flag defGhcFlag "hpcdir"               (SepArg setOptHpcDir)
  , make_ord_flag defGhciFlag "ghci-script"         (hasArg addGhciScript)
  , make_ord_flag defGhciFlag "interactive-print"   (hasArg setInteractivePrint)
  , make_ord_flag defGhcFlag "ticky-allocd"
        (NoArg (setGeneralFlag Opt_Ticky_Allocd))
  , make_ord_flag defGhcFlag "ticky-LNE"
        (NoArg (setGeneralFlag Opt_Ticky_LNE))
  , make_ord_flag defGhcFlag "ticky-dyn-thunk"
        (NoArg (setGeneralFlag Opt_Ticky_Dyn_Thunk))
        ------- recompilation checker --------------------------------------
  , make_dep_flag defGhcFlag "recomp"
        (NoArg $ unSetGeneralFlag Opt_ForceRecomp)
             "Use -fno-force-recomp instead"
  , make_dep_flag defGhcFlag "no-recomp"
        (NoArg $ setGeneralFlag Opt_ForceRecomp) "Use -fforce-recomp instead"
  , make_ord_flag defFlag "fmax-errors"
      (intSuffix (\n d -> d { maxErrors = Just (max 1 n) }))
  , make_ord_flag defFlag "fno-max-errors"
      (noArg (\d -> d { maxErrors = Nothing }))
  , make_ord_flag defFlag "freverse-errors"
        (noArg (\d -> d {reverseErrors = True} ))
  , make_ord_flag defFlag "fno-reverse-errors"
        (noArg (\d -> d {reverseErrors = False} ))

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

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

        ------ Output style options -----------------------------------------
  , make_ord_flag defFlag "dppr-user-length" (intSuffix (\n d ->
                                                       d { pprUserLength = n }))
  , make_ord_flag defFlag "dppr-cols"        (intSuffix (\n d ->
                                                             d { pprCols = n }))
  , make_ord_flag defFlag "fdiagnostics-color=auto"
      (NoArg (upd (\d -> d { useColor = Auto })))
  , make_ord_flag defFlag "fdiagnostics-color=always"
      (NoArg (upd (\d -> d { useColor = Always })))
  , make_ord_flag defFlag "fdiagnostics-color=never"
      (NoArg (upd (\d -> d { useColor = Never })))

  -- Suppress all that is suppressable in core dumps.
  -- Except for uniques, as some simplifier phases introduce new variables that
  -- have otherwise identical names.
  , make_ord_flag defGhcFlag "dsuppress-all"
      (NoArg $ do setGeneralFlag Opt_SuppressCoercions
                  setGeneralFlag Opt_SuppressVarKinds
                  setGeneralFlag Opt_SuppressModulePrefixes
                  setGeneralFlag Opt_SuppressTypeApplications
                  setGeneralFlag Opt_SuppressIdInfo
                  setGeneralFlag Opt_SuppressTicks
                  setGeneralFlag Opt_SuppressTypeSignatures)

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

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

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

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

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

     ------ Warning opts -------------------------------------------------
  , make_ord_flag defFlag "W"       (NoArg (mapM_ setWarningFlag minusWOpts))
  , make_ord_flag defFlag "Werror"
               (NoArg (do { setGeneralFlag Opt_WarnIsError
                          ; mapM_ setFatalWarningFlag minusWeverythingOpts   }))
  , make_ord_flag defFlag "Wwarn"
               (NoArg (do { unSetGeneralFlag Opt_WarnIsError
                          ; mapM_ unSetFatalWarningFlag minusWeverythingOpts }))
                          -- Opt_WarnIsError is still needed to pass -Werror
                          -- to CPP; see runCpp in SysTools
  , make_dep_flag defFlag "Wnot"    (NoArg (upd (\d ->
                                              d {warningFlags = IntSet.empty})))
                                             "Use -w or -Wno-everything instead"
  , make_ord_flag defFlag "w"       (NoArg (upd (\d ->
                                              d {warningFlags = IntSet.empty})))

     -- New-style uniform warning sets
     --
     -- Note that -Weverything > -Wall > -Wextra > -Wdefault > -Wno-everything
  , make_ord_flag defFlag "Weverything"    (NoArg (mapM_
                                           setWarningFlag minusWeverythingOpts))
  , make_ord_flag defFlag "Wno-everything"
                           (NoArg (upd (\d -> d {warningFlags = IntSet.empty})))

  , make_ord_flag defFlag "Wall"           (NoArg (mapM_
                                                  setWarningFlag minusWallOpts))
  , make_ord_flag defFlag "Wno-all"        (NoArg (mapM_
                                                unSetWarningFlag minusWallOpts))

  , make_ord_flag defFlag "Wextra"         (NoArg (mapM_
                                                     setWarningFlag minusWOpts))
  , make_ord_flag defFlag "Wno-extra"      (NoArg (mapM_
                                                   unSetWarningFlag minusWOpts))

  , make_ord_flag defFlag "Wdefault"       (NoArg (mapM_
                                               setWarningFlag standardWarnings))
  , make_ord_flag defFlag "Wno-default"    (NoArg (mapM_
                                             unSetWarningFlag standardWarnings))

  , make_ord_flag defFlag "Wcompat"        (NoArg (mapM_
                                               setWarningFlag minusWcompatOpts))
  , make_ord_flag defFlag "Wno-compat"     (NoArg (mapM_
                                             unSetWarningFlag minusWcompatOpts))

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

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


  , make_ord_flag defFlag "fmax-relevant-binds"
      (intSuffix (\n d -> d { maxRelevantBinds = Just n }))
  , make_ord_flag defFlag "fno-max-relevant-binds"
      (noArg (\d -> d { maxRelevantBinds = Nothing }))
  , make_ord_flag defFlag "fmax-uncovered-patterns"
      (intSuffix (\n d -> d { maxUncoveredPatterns = n }))
  , make_ord_flag defFlag "fsimplifier-phases"
      (intSuffix (\n d -> d { simplPhases = n }))
  , make_ord_flag defFlag "fmax-simplifier-iterations"
      (intSuffix (\n d -> d { maxSimplIterations = n }))
  , make_ord_flag defFlag "fmax-pmcheck-iterations"
      (intSuffix (\n d -> d{ maxPmCheckIterations = n }))
  , make_ord_flag defFlag "fsimpl-tick-factor"
      (intSuffix (\n d -> d { simplTickFactor = n }))
  , make_ord_flag defFlag "fspec-constr-threshold"
      (intSuffix (\n d -> d { specConstrThreshold = Just n }))
  , make_ord_flag defFlag "fno-spec-constr-threshold"
      (noArg (\d -> d { specConstrThreshold = Nothing }))
  , make_ord_flag defFlag "fspec-constr-count"
      (intSuffix (\n d -> d { specConstrCount = Just n }))
  , make_ord_flag defFlag "fno-spec-constr-count"
      (noArg (\d -> d { specConstrCount = Nothing }))
  , make_ord_flag defFlag "fspec-constr-recursive"
      (intSuffix (\n d -> d { specConstrRecursive = n }))
  , make_ord_flag defFlag "fliberate-case-threshold"
      (intSuffix (\n d -> d { liberateCaseThreshold = Just n }))
  , make_ord_flag defFlag "fno-liberate-case-threshold"
      (noArg (\d -> d { liberateCaseThreshold = Nothing }))
  , make_ord_flag defFlag "frule-check"
      (sepArg (\s d -> d { ruleCheck = Just s }))
  , make_ord_flag defFlag "freduction-depth"
      (intSuffix (\n d -> d { reductionDepth = treatZeroAsInf n }))
  , make_ord_flag defFlag "fconstraint-solver-iterations"
      (intSuffix (\n d -> d { solverIterations = treatZeroAsInf n }))
  , (Deprecated, defFlag "fcontext-stack"
      (intSuffixM (\n d ->
       do { deprecate $ "use -freduction-depth=" ++ show n ++ " instead"
          ; return $ d { reductionDepth = treatZeroAsInf n } })))
  , (Deprecated, defFlag "ftype-function-depth"
      (intSuffixM (\n d ->
       do { deprecate $ "use -freduction-depth=" ++ show n ++ " instead"
          ; return $ d { reductionDepth = treatZeroAsInf n } })))
  , make_ord_flag defFlag "fstrictness-before"
      (intSuffix (\n d -> d { strictnessBefore = n : strictnessBefore d }))
  , make_ord_flag defFlag "ffloat-lam-args"
      (intSuffix (\n d -> d { floatLamArgs = Just n }))
  , make_ord_flag defFlag "ffloat-all-lams"
      (noArg (\d -> d { floatLamArgs = Nothing }))
  , make_ord_flag defFlag "fhistory-size"
      (intSuffix (\n d -> d { historySize = n }))
  , make_ord_flag defFlag "funfolding-creation-threshold"
      (intSuffix   (\n d -> d {ufCreationThreshold = n}))
  , make_ord_flag defFlag "funfolding-use-threshold"
      (intSuffix   (\n d -> d {ufUseThreshold = n}))
  , make_ord_flag defFlag "funfolding-fun-discount"
      (intSuffix   (\n d -> d {ufFunAppDiscount = n}))
  , make_ord_flag defFlag "funfolding-dict-discount"
      (intSuffix   (\n d -> d {ufDictDiscount = n}))
  , make_ord_flag defFlag "funfolding-keeness-factor"
      (floatSuffix (\n d -> d {ufKeenessFactor = n}))
  , make_ord_flag defFlag "fmax-worker-args"
      (intSuffix (\n d -> d {maxWorkerArgs = n}))
  , make_ord_flag defGhciFlag "fghci-hist-size"
      (intSuffix (\n d -> d {ghciHistSize = n}))
  , make_ord_flag defGhcFlag "fmax-inline-alloc-size"
      (intSuffix (\n d -> d { maxInlineAllocSize = n }))
  , make_ord_flag defGhcFlag "fmax-inline-memcpy-insns"
      (intSuffix (\n d -> d { maxInlineMemcpyInsns = n }))
  , make_ord_flag defGhcFlag "fmax-inline-memset-insns"
      (intSuffix (\n d -> d { maxInlineMemsetInsns = n }))
  , make_ord_flag defGhcFlag "dinitial-unique"
      (intSuffix (\n d -> d { initialUnique = n }))
  , make_ord_flag defGhcFlag "dunique-increment"
      (intSuffix (\n d -> d { uniqueIncrement = n }))

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

        -- OLD profiling flags
  , make_dep_flag defGhcFlag "auto-all"
                    (noArg (\d -> d { profAuto = ProfAutoAll } ))
                    "Use -fprof-auto instead"
  , make_dep_flag defGhcFlag "no-auto-all"
                    (noArg (\d -> d { profAuto = NoProfAuto } ))
                    "Use -fno-prof-auto instead"
  , make_dep_flag defGhcFlag "auto"
                    (noArg (\d -> d { profAuto = ProfAutoExports } ))
                    "Use -fprof-auto-exported instead"
  , make_dep_flag defGhcFlag "no-auto"
            (noArg (\d -> d { profAuto = NoProfAuto } ))
                    "Use -fno-prof-auto instead"
  , make_dep_flag defGhcFlag "caf-all"
            (NoArg (setGeneralFlag Opt_AutoSccsOnIndividualCafs))
                    "Use -fprof-cafs instead"
  , make_dep_flag defGhcFlag "no-caf-all"
            (NoArg (unSetGeneralFlag Opt_AutoSccsOnIndividualCafs))
                    "Use -fno-prof-cafs instead"

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

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

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

  , make_ord_flag defFlag "fno-code"         (NoArg ((upd $ \d ->
                  d { ghcLink=NoLink }) >> setTarget HscNothing))
  , make_ord_flag defFlag "fbyte-code"       (NoArg (setTarget HscInterpreted))
  , make_ord_flag defFlag "fobject-code"     (NoArg (setTargetWithPlatform
                                                             defaultHscTarget))
  , make_dep_flag defFlag "fglasgow-exts"
      (NoArg enableGlasgowExts) "Use individual extensions instead"
  , make_dep_flag defFlag "fno-glasgow-exts"
      (NoArg disableGlasgowExts) "Use individual extensions instead"
  , make_ord_flag defFlag "Wunused-binds" (NoArg enableUnusedBinds)
  , make_ord_flag defFlag "Wno-unused-binds" (NoArg disableUnusedBinds)
  , make_ord_flag defHiddenFlag "fwarn-unused-binds" (NoArg enableUnusedBinds)
  , make_ord_flag defHiddenFlag "fno-warn-unused-binds" (NoArg
                                                            disableUnusedBinds)

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

         ------ Debugging flags ----------------------------------------------
  , make_ord_flag defGhcFlag "g"             (OptIntSuffix setDebugLevel)
 ]
 ++ map (mkFlag turnOn  ""          setGeneralFlag    ) negatableFlagsDeps
 ++ map (mkFlag turnOff "no-"       unSetGeneralFlag  ) negatableFlagsDeps
 ++ map (mkFlag turnOn  "d"         setGeneralFlag    ) dFlagsDeps
 ++ map (mkFlag turnOff "dno-"      unSetGeneralFlag  ) dFlagsDeps
 ++ map (mkFlag turnOn  "f"         setGeneralFlag    ) fFlagsDeps
 ++ map (mkFlag turnOff "fno-"      unSetGeneralFlag  ) fFlagsDeps
 ++ map (mkFlag turnOn  "W"         setWarningFlag    ) wWarningFlagsDeps
 ++ map (mkFlag turnOff "Wno-"      unSetWarningFlag  ) wWarningFlagsDeps
 ++ map (mkFlag turnOn  "Werror="   (\flag -> do {
                                       ; setWarningFlag flag
                                       ; setFatalWarningFlag flag }))
                                                        wWarningFlagsDeps
 ++ map (mkFlag turnOn  "Wwarn="     unSetFatalWarningFlag )
                                                        wWarningFlagsDeps
 ++ map (mkFlag turnOn  "Wno-error=" unSetFatalWarningFlag )
                                                        wWarningFlagsDeps
 ++ map (mkFlag turnOn  "fwarn-"    setWarningFlag   . hideFlag)
    wWarningFlagsDeps
 ++ map (mkFlag turnOff "fno-warn-" unSetWarningFlag . hideFlag)
    wWarningFlagsDeps
 ++ [ (NotDeprecated, unrecognisedWarning "W"),
      (Deprecated,    unrecognisedWarning "fwarn-"),
      (Deprecated,    unrecognisedWarning "fno-warn-") ]
 ++ map (mkFlag turnOn  "f"         setExtensionFlag  ) fLangFlagsDeps
 ++ map (mkFlag turnOff "fno-"      unSetExtensionFlag) fLangFlagsDeps
 ++ map (mkFlag turnOn  "X"         setExtensionFlag  ) xFlagsDeps
 ++ map (mkFlag turnOff "XNo"       unSetExtensionFlag) xFlagsDeps
 ++ map (mkFlag turnOn  "X"         setLanguage       ) languageFlagsDeps
 ++ map (mkFlag turnOn  "X"         setSafeHaskell    ) safeHaskellFlagsDeps
 ++ [ make_dep_flag defFlag "XGenerics"
        (NoArg $ return ())
                  ("it does nothing; look into -XDefaultSignatures " ++
                   "and -XDeriveGeneric for generic programming support.")
    , make_dep_flag defFlag "XNoGenerics"
        (NoArg $ return ())
               ("it does nothing; look into -XDefaultSignatures and " ++
                  "-XDeriveGeneric for generic programming support.") ]

-- | This is where we handle unrecognised warning flags. We only issue a warning
-- if -Wunrecognised-warning-flags is set. See Trac #11429 for context.
unrecognisedWarning :: String -> Flag (CmdLineP DynFlags)
unrecognisedWarning prefix = defHiddenFlag prefix (Prefix action)
  where
    action :: String -> EwM (CmdLineP DynFlags) ()
    action flag = do
      f <- wopt Opt_WarnUnrecognisedWarningFlags <$> liftEwM getCmdLineState
      when f $ addWarn $ "unrecognised warning flag: -" ++ prefix ++ flag

-- See Note [Supporting CLI completion]
package_flags_deps :: [(Deprecation, Flag (CmdLineP DynFlags))]
package_flags_deps = [
        ------- Packages ----------------------------------------------------
    make_ord_flag defFlag "package-db"
      (HasArg (addPkgConfRef . PkgConfFile))
  , make_ord_flag defFlag "clear-package-db"      (NoArg clearPkgConf)
  , make_ord_flag defFlag "no-global-package-db"  (NoArg removeGlobalPkgConf)
  , make_ord_flag defFlag "no-user-package-db"    (NoArg removeUserPkgConf)
  , make_ord_flag defFlag "global-package-db"
      (NoArg (addPkgConfRef GlobalPkgConf))
  , make_ord_flag defFlag "user-package-db"
      (NoArg (addPkgConfRef UserPkgConf))
    -- backwards compat with GHC<=7.4 :
  , make_dep_flag defFlag "package-conf"
      (HasArg $ addPkgConfRef . PkgConfFile) "Use -package-db instead"
  , make_dep_flag defFlag "no-user-package-conf"
      (NoArg removeUserPkgConf)              "Use -no-user-package-db instead"
  , make_ord_flag defGhcFlag "package-name"       (HasArg $ \name -> do
                                      upd (setUnitId name))
                                      -- TODO: Since we JUST deprecated
                                      -- -this-package-key, let's keep this
                                      -- undeprecated for another cycle.
                                      -- Deprecate this eventually.
                                      -- deprecate "Use -this-unit-id instead")
  , make_dep_flag defGhcFlag "this-package-key"   (HasArg $ upd . setUnitId)
                                                  "Use -this-unit-id instead"
  , make_ord_flag defGhcFlag "this-unit-id"       (hasArg setUnitId)
  , make_ord_flag defFlag "package"               (HasArg exposePackage)
  , make_ord_flag defFlag "plugin-package-id"     (HasArg exposePluginPackageId)
  , make_ord_flag defFlag "plugin-package"        (HasArg exposePluginPackage)
  , make_ord_flag defFlag "package-id"            (HasArg exposePackageId)
  , make_ord_flag defFlag "hide-package"          (HasArg hidePackage)
  , make_ord_flag defFlag "hide-all-packages"
      (NoArg (setGeneralFlag Opt_HideAllPackages))
  , make_ord_flag defFlag "hide-all-plugin-packages"
      (NoArg (setGeneralFlag Opt_HideAllPluginPackages))
  , make_ord_flag defFlag "package-env"           (HasArg setPackageEnv)
  , make_ord_flag defFlag "ignore-package"        (HasArg ignorePackage)
  , make_dep_flag defFlag "syslib" (HasArg exposePackage) "Use -package instead"
  , make_ord_flag defFlag "distrust-all-packages"
      (NoArg (setGeneralFlag Opt_DistrustAllPackages))
  , make_ord_flag defFlag "trust"                 (HasArg trustPackage)
  , make_ord_flag 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 -> (Deprecation, FlagSpec flag)
flagSpec name flag = flagSpec' name flag nop

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

-- | Define a new deprecated flag with an effect.
depFlagSpecOp :: String -> flag -> (TurnOnFlag -> DynP ()) -> String
            -> (Deprecation, FlagSpec flag)
depFlagSpecOp name flag act dep =
    (Deprecated, snd (flagSpec' name flag (\f -> act f >> deprecate dep)))

-- | Define a new deprecated flag.
depFlagSpec :: String -> flag -> String
            -> (Deprecation, FlagSpec flag)
depFlagSpec name flag dep = depFlagSpecOp name flag nop dep

-- | Define a new deprecated flag with an effect where the deprecation message
-- depends on the flag value
depFlagSpecOp' :: String
             -> flag
             -> (TurnOnFlag -> DynP ())
             -> (TurnOnFlag -> String)
             -> (Deprecation, FlagSpec flag)
depFlagSpecOp' name flag act dep =
    (Deprecated, FlagSpec name flag (\f -> act f >> (deprecate $ dep f))
                                                                       AllModes)

-- | Define a new deprecated flag where the deprecation message
-- depends on the flag value
depFlagSpec' :: String
             -> flag
             -> (TurnOnFlag -> String)
             -> (Deprecation, FlagSpec flag)
depFlagSpec' name flag dep = depFlagSpecOp' name flag nop dep


-- | Define a new deprecated flag where the deprecation message
-- is shown depending on the flag value
depFlagSpecCond :: String
                -> flag
                -> (TurnOnFlag -> Bool)
                -> String
                -> (Deprecation, FlagSpec flag)
depFlagSpecCond name flag cond dep =
    (Deprecated, FlagSpec name flag (\f -> when (cond f) $ deprecate dep)
                                                                       AllModes)

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

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

-- | Define a new flag invisible to CLI completion.
flagHiddenSpec :: String -> flag -> (Deprecation, 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 ())
                -> (Deprecation, FlagSpec flag)
flagHiddenSpec' name flag act = (NotDeprecated, FlagSpec name flag act
                                                                     HiddenFlag)

-- | Hide a 'FlagSpec' from being displayed in @--show-options@.
--
-- This is for example useful for flags that are obsolete, but should not
-- (yet) be deprecated for compatibility reasons.
hideFlag :: (Deprecation, FlagSpec a) -> (Deprecation, FlagSpec a)
hideFlag (dep, fs) = (dep, fs { flagSpecGhcMode = HiddenFlag })

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

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

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

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

-- | Find the 'FlagSpec' for a 'WarningFlag'.
flagSpecOf :: WarningFlag -> Maybe (FlagSpec WarningFlag)
flagSpecOf flag = listToMaybe $ filter check wWarningFlags
  where
    check fs = flagSpecFlag fs == flag

-- | These @-W\<blah\>@ flags can all be reversed with @-Wno-\<blah\>@
wWarningFlags :: [FlagSpec WarningFlag]
wWarningFlags = map snd (sortBy (comparing fst) wWarningFlagsDeps)

wWarningFlagsDeps :: [(Deprecation, FlagSpec WarningFlag)]
wWarningFlagsDeps = [
-- 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 "alternative-layout-rule-transitional"
                                      Opt_WarnAlternativeLayoutRuleTransitional,
  depFlagSpec "amp"                      Opt_WarnAMP
    "it has no effect",
  depFlagSpec "auto-orphans"             Opt_WarnAutoOrphans
    "it has no effect",
  flagSpec "cpp-undef"                   Opt_WarnCPPUndef,
  flagSpec "unbanged-strict-patterns"    Opt_WarnUnbangedStrictPatterns,
  flagSpec "deferred-type-errors"        Opt_WarnDeferredTypeErrors,
  flagSpec "deferred-out-of-scope-variables"
                                         Opt_WarnDeferredOutOfScopeVariables,
  flagSpec "deprecations"                Opt_WarnWarningsDeprecations,
  flagSpec "deprecated-flags"            Opt_WarnDeprecatedFlags,
  flagSpec "deriving-typeable"           Opt_WarnDerivingTypeable,
  flagSpec "dodgy-exports"               Opt_WarnDodgyExports,
  flagSpec "dodgy-foreign-imports"       Opt_WarnDodgyForeignImports,
  flagSpec "dodgy-imports"               Opt_WarnDodgyImports,
  flagSpec "empty-enumerations"          Opt_WarnEmptyEnumerations,
  depFlagSpec "duplicate-constraints"    Opt_WarnDuplicateConstraints
    "it is subsumed by -Wredundant-constraints",
  flagSpec "redundant-constraints"       Opt_WarnRedundantConstraints,
  flagSpec "duplicate-exports"           Opt_WarnDuplicateExports,
  flagSpec "hi-shadowing"                Opt_WarnHiShadows,
  flagSpec "implicit-prelude"            Opt_WarnImplicitPrelude,
  flagSpec "incomplete-patterns"         Opt_WarnIncompletePatterns,
  flagSpec "incomplete-record-updates"   Opt_WarnIncompletePatternsRecUpd,
  flagSpec "incomplete-uni-patterns"     Opt_WarnIncompleteUniPatterns,
  flagSpec "inline-rule-shadowing"       Opt_WarnInlineRuleShadowing,
  flagSpec "identities"                  Opt_WarnIdentities,
  flagSpec "missing-fields"              Opt_WarnMissingFields,
  flagSpec "missing-import-lists"        Opt_WarnMissingImportList,
  depFlagSpec "missing-local-sigs"       Opt_WarnMissingLocalSignatures
    "it is replaced by -Wmissing-local-signatures",
  flagSpec "missing-local-signatures"    Opt_WarnMissingLocalSignatures,
  flagSpec "missing-methods"             Opt_WarnMissingMethods,
  flagSpec "missing-monadfail-instances" Opt_WarnMissingMonadFailInstances,
  flagSpec "semigroup"                   Opt_WarnSemigroup,
  flagSpec "missing-signatures"          Opt_WarnMissingSignatures,
  depFlagSpec "missing-exported-sigs"    Opt_WarnMissingExportedSignatures
    "it is replaced by -Wmissing-exported-signatures",
  flagSpec "missing-exported-signatures" Opt_WarnMissingExportedSignatures,
  flagSpec "monomorphism-restriction"    Opt_WarnMonomorphism,
  flagSpec "name-shadowing"              Opt_WarnNameShadowing,
  flagSpec "noncanonical-monad-instances"
                                         Opt_WarnNonCanonicalMonadInstances,
  flagSpec "noncanonical-monadfail-instances"
                                         Opt_WarnNonCanonicalMonadFailInstances,
  flagSpec "noncanonical-monoid-instances"
                                         Opt_WarnNonCanonicalMonoidInstances,
  flagSpec "orphans"                     Opt_WarnOrphans,
  flagSpec "overflowed-literals"         Opt_WarnOverflowedLiterals,
  flagSpec "overlapping-patterns"        Opt_WarnOverlappingPatterns,
  flagSpec "missed-specialisations"      Opt_WarnMissedSpecs,
  flagSpec "missed-specializations"      Opt_WarnMissedSpecs,
  flagSpec "all-missed-specialisations"  Opt_WarnAllMissedSpecs,
  flagSpec "all-missed-specializations"  Opt_WarnAllMissedSpecs,
  flagSpec' "safe"                       Opt_WarnSafe setWarnSafe,
  flagSpec "trustworthy-safe"            Opt_WarnTrustworthySafe,
  flagSpec "tabs"                        Opt_WarnTabs,
  flagSpec "type-defaults"               Opt_WarnTypeDefaults,
  flagSpec "typed-holes"                 Opt_WarnTypedHoles,
  flagSpec "partial-type-signatures"     Opt_WarnPartialTypeSignatures,
  flagSpec "unrecognised-pragmas"        Opt_WarnUnrecognisedPragmas,
  flagSpec' "unsafe"                     Opt_WarnUnsafe setWarnUnsafe,
  flagSpec "unsupported-calling-conventions"
                                         Opt_WarnUnsupportedCallingConventions,
  flagSpec "unsupported-llvm-version"    Opt_WarnUnsupportedLlvmVersion,
  flagSpec "unticked-promoted-constructors"
                                         Opt_WarnUntickedPromotedConstructors,
  flagSpec "unused-do-bind"              Opt_WarnUnusedDoBind,
  flagSpec "unused-foralls"              Opt_WarnUnusedForalls,
  flagSpec "unused-imports"              Opt_WarnUnusedImports,
  flagSpec "unused-local-binds"          Opt_WarnUnusedLocalBinds,
  flagSpec "unused-matches"              Opt_WarnUnusedMatches,
  flagSpec "unused-pattern-binds"        Opt_WarnUnusedPatternBinds,
  flagSpec "unused-top-binds"            Opt_WarnUnusedTopBinds,
  flagSpec "unused-type-patterns"        Opt_WarnUnusedTypePatterns,
  flagSpec "warnings-deprecations"       Opt_WarnWarningsDeprecations,
  flagSpec "wrong-do-bind"               Opt_WarnWrongDoBind,
  flagSpec "missing-pattern-synonym-signatures"
                                    Opt_WarnMissingPatternSynonymSignatures,
  flagSpec "simplifiable-class-constraints" Opt_WarnSimplifiableClassConstraints,
  flagSpec "missing-home-modules"        Opt_WarnMissingHomeModules,
  flagSpec "unrecognised-warning-flags"  Opt_WarnUnrecognisedWarningFlags ]

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

-- | These @-d\<blah\>@ flags can all be reversed with @-dno-\<blah\>@
dFlagsDeps :: [(Deprecation, FlagSpec GeneralFlag)]
dFlagsDeps = [
-- 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,
  depFlagSpec' "ppr-ticks"              Opt_PprShowTicks
     (\turn_on -> useInstead "suppress-ticks" (not turn_on)),
  flagSpec "suppress-ticks"             Opt_SuppressTicks,
  flagSpec "suppress-coercions"         Opt_SuppressCoercions,
  flagSpec "suppress-idinfo"            Opt_SuppressIdInfo,
  flagSpec "suppress-unfoldings"        Opt_SuppressUnfoldings,
  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 = map snd fFlagsDeps

fFlagsDeps :: [(Deprecation, FlagSpec GeneralFlag)]
fFlagsDeps = [
-- 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 "case-folding"                     Opt_CaseFolding,
  flagSpec "cmm-elim-common-blocks"           Opt_CmmElimCommonBlocks,
  flagSpec "cmm-sink"                         Opt_CmmSink,
  flagSpec "cse"                              Opt_CSE,
  flagSpec "stg-cse"                          Opt_StgCSE,
  flagSpec "cpr-anal"                         Opt_CprAnal,
  flagSpec "defer-type-errors"                Opt_DeferTypeErrors,
  flagSpec "defer-typed-holes"                Opt_DeferTypedHoles,
  flagSpec "defer-out-of-scope-variables"     Opt_DeferOutOfScopeVariables,
  flagSpec "diagnostics-show-caret"           Opt_DiagnosticsShowCaret,
  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 "external-interpreter"             Opt_ExternalInterpreter,
  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,
  flagGhciSpec "local-ghci-history"           Opt_LocalGhciHistory,
  flagSpec "ghci-sandbox"                     Opt_GhciSandbox,
  flagSpec "helpful-errors"                   Opt_HelpfulErrors,
  flagSpec "hpc"                              Opt_Hpc,
  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,
  flagHiddenSpec "llvm-fill-undef-with-garbage" Opt_LlvmFillUndefWithGarbage,
  flagSpec "loopification"                    Opt_Loopification,
  flagSpec "omit-interface-pragmas"           Opt_OmitInterfacePragmas,
  flagSpec "omit-yields"                      Opt_OmitYields,
  flagSpec "optimal-applicative-do"           Opt_OptimalApplicativeDo,
  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 "print-explicit-coercions"         Opt_PrintExplicitCoercions,
  flagSpec "print-explicit-runtime-reps"      Opt_PrintExplicitRuntimeReps,
  flagSpec "print-equality-relations"         Opt_PrintEqualityRelations,
  flagSpec "print-unicode-syntax"             Opt_PrintUnicodeSyntax,
  flagSpec "print-expanded-synonyms"          Opt_PrintExpandedSynonyms,
  flagSpec "print-potential-instances"        Opt_PrintPotentialInstances,
  flagSpec "print-typechecker-elaboration"    Opt_PrintTypecheckerElaboration,
  flagSpec "prof-cafs"                        Opt_AutoSccsOnIndividualCafs,
  flagSpec "prof-count-entries"               Opt_ProfCountEntries,
  flagSpec "regs-graph"                       Opt_RegsGraph,
  flagSpec "regs-iterative"                   Opt_RegsIterative,
  depFlagSpec' "rewrite-rules"                Opt_EnableRewriteRules
   (useInstead "enable-rewrite-rules"),
  flagSpec "shared-implib"                    Opt_SharedImplib,
  flagSpec "spec-constr"                      Opt_SpecConstr,
  flagSpec "spec-constr-keen"                 Opt_SpecConstrKeen,
  flagSpec "specialise"                       Opt_Specialise,
  flagSpec "specialize"                       Opt_Specialise,
  flagSpec "specialise-aggressively"          Opt_SpecialiseAggressively,
  flagSpec "specialize-aggressively"          Opt_SpecialiseAggressively,
  flagSpec "cross-module-specialise"          Opt_CrossModuleSpecialise,
  flagSpec "cross-module-specialize"          Opt_CrossModuleSpecialise,
  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,
  flagSpec "version-macros"                   Opt_VersionMacros,
  flagSpec "worker-wrapper"                   Opt_WorkerWrapper,
  flagSpec "solve-constant-dicts"             Opt_SolveConstantDicts,
  flagSpec "show-warning-groups"              Opt_ShowWarnGroups,
  flagSpec "hide-source-paths"                Opt_HideSourcePaths,
  flagSpec "show-hole-constraints"            Opt_ShowHoleConstraints,
  flagSpec "whole-archive-hs-libs"            Opt_WholeArchiveHsLibs
  ]

-- | These @-f\<blah\>@ flags can all be reversed with @-fno-\<blah\>@
fLangFlags :: [FlagSpec LangExt.Extension]
fLangFlags = map snd fLangFlagsDeps

fLangFlagsDeps :: [(Deprecation, FlagSpec LangExt.Extension)]
fLangFlagsDeps = [
-- See Note [Updating flag description in the User's Guide]
-- See Note [Supporting CLI completion]
  depFlagSpecOp' "th"                           LangExt.TemplateHaskell
    checkTemplateHaskellOk
    (deprecatedForExtension "TemplateHaskell"),
  depFlagSpec' "fi"                             LangExt.ForeignFunctionInterface
    (deprecatedForExtension "ForeignFunctionInterface"),
  depFlagSpec' "ffi"                            LangExt.ForeignFunctionInterface
    (deprecatedForExtension "ForeignFunctionInterface"),
  depFlagSpec' "arrows"                         LangExt.Arrows
    (deprecatedForExtension "Arrows"),
  depFlagSpec' "implicit-prelude"               LangExt.ImplicitPrelude
    (deprecatedForExtension "ImplicitPrelude"),
  depFlagSpec' "bang-patterns"                  LangExt.BangPatterns
    (deprecatedForExtension "BangPatterns"),
  depFlagSpec' "monomorphism-restriction"       LangExt.MonomorphismRestriction
    (deprecatedForExtension "MonomorphismRestriction"),
  depFlagSpec' "mono-pat-binds"                 LangExt.MonoPatBinds
    (deprecatedForExtension "MonoPatBinds"),
  depFlagSpec' "extended-default-rules"         LangExt.ExtendedDefaultRules
    (deprecatedForExtension "ExtendedDefaultRules"),
  depFlagSpec' "implicit-params"                LangExt.ImplicitParams
    (deprecatedForExtension "ImplicitParams"),
  depFlagSpec' "scoped-type-variables"          LangExt.ScopedTypeVariables
    (deprecatedForExtension "ScopedTypeVariables"),
  depFlagSpec' "parr"                           LangExt.ParallelArrays
    (deprecatedForExtension "ParallelArrays"),
  depFlagSpec' "PArr"                           LangExt.ParallelArrays
    (deprecatedForExtension "ParallelArrays"),
  depFlagSpec' "allow-overlapping-instances"    LangExt.OverlappingInstances
    (deprecatedForExtension "OverlappingInstances"),
  depFlagSpec' "allow-undecidable-instances"    LangExt.UndecidableInstances
    (deprecatedForExtension "UndecidableInstances"),
  depFlagSpec' "allow-incoherent-instances"     LangExt.IncoherentInstances
    (deprecatedForExtension "IncoherentInstances")
  ]

supportedLanguages :: [String]
supportedLanguages = map (flagSpecName . snd) languageFlagsDeps

supportedLanguageOverlays :: [String]
supportedLanguageOverlays = map (flagSpecName . snd) safeHaskellFlagsDeps

supportedExtensions :: [String]
supportedExtensions = concatMap toFlagSpecNamePair xFlags
  where
    toFlagSpecNamePair flg
      | otherwise = [name, noName]
      where
        noName = "No" ++ name
        name = flagSpecName flg

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

-- | These -X<blah> flags cannot be reversed with -XNo<blah>
languageFlagsDeps :: [(Deprecation, FlagSpec Language)]
languageFlagsDeps = [
  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.
safeHaskellFlagsDeps :: [(Deprecation, FlagSpec SafeHaskellMode)]
safeHaskellFlagsDeps = [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 LangExt.Extension]
xFlags = map snd xFlagsDeps

xFlagsDeps :: [(Deprecation, FlagSpec LangExt.Extension)]
xFlagsDeps = [
-- See Note [Updating flag description in the User's Guide]
-- See Note [Supporting CLI completion]
-- See Note [Adding a language extension]
-- Please keep the list of flags below sorted alphabetically
  flagSpec "AllowAmbiguousTypes"              LangExt.AllowAmbiguousTypes,
  flagSpec "AlternativeLayoutRule"            LangExt.AlternativeLayoutRule,
  flagSpec "AlternativeLayoutRuleTransitional"
                                              LangExt.AlternativeLayoutRuleTransitional,
  flagSpec "Arrows"                           LangExt.Arrows,
  flagSpec "AutoDeriveTypeable"               LangExt.AutoDeriveTypeable,
  flagSpec "BangPatterns"                     LangExt.BangPatterns,
  flagSpec "BinaryLiterals"                   LangExt.BinaryLiterals,
  flagSpec "CApiFFI"                          LangExt.CApiFFI,
  flagSpec "CPP"                              LangExt.Cpp,
  flagSpec "ConstrainedClassMethods"          LangExt.ConstrainedClassMethods,
  flagSpec "ConstraintKinds"                  LangExt.ConstraintKinds,
  flagSpec "DataKinds"                        LangExt.DataKinds,
  depFlagSpecCond "DatatypeContexts"          LangExt.DatatypeContexts
    id
         ("It was widely considered a misfeature, " ++
                     "and has been removed from the Haskell language."),
  flagSpec "DefaultSignatures"                LangExt.DefaultSignatures,
  flagSpec "DeriveAnyClass"                   LangExt.DeriveAnyClass,
  flagSpec "DeriveDataTypeable"               LangExt.DeriveDataTypeable,
  flagSpec "DeriveFoldable"                   LangExt.DeriveFoldable,
  flagSpec "DeriveFunctor"                    LangExt.DeriveFunctor,
  flagSpec "DeriveGeneric"                    LangExt.DeriveGeneric,
  flagSpec "DeriveLift"                       LangExt.DeriveLift,
  flagSpec "DeriveTraversable"                LangExt.DeriveTraversable,
  flagSpec "DerivingStrategies"               LangExt.DerivingStrategies,
  flagSpec "DisambiguateRecordFields"         LangExt.DisambiguateRecordFields,
  flagSpec "DoAndIfThenElse"                  LangExt.DoAndIfThenElse,
  depFlagSpec' "DoRec"                        LangExt.RecursiveDo
    (deprecatedForExtension "RecursiveDo"),
  flagSpec "DuplicateRecordFields"            LangExt.DuplicateRecordFields,
  flagSpec "EmptyCase"                        LangExt.EmptyCase,
  flagSpec "EmptyDataDecls"                   LangExt.EmptyDataDecls,
  flagSpec "ExistentialQuantification"        LangExt.ExistentialQuantification,
  flagSpec "ExplicitForAll"                   LangExt.ExplicitForAll,
  flagSpec "ExplicitNamespaces"               LangExt.ExplicitNamespaces,
  flagSpec "ExtendedDefaultRules"             LangExt.ExtendedDefaultRules,
  flagSpec "FlexibleContexts"                 LangExt.FlexibleContexts,
  flagSpec "FlexibleInstances"                LangExt.FlexibleInstances,
  flagSpec "ForeignFunctionInterface"         LangExt.ForeignFunctionInterface,
  flagSpec "FunctionalDependencies"           LangExt.FunctionalDependencies,
  flagSpec "GADTSyntax"                       LangExt.GADTSyntax,
  flagSpec "GADTs"                            LangExt.GADTs,
  flagSpec "GHCForeignImportPrim"             LangExt.GHCForeignImportPrim,
  flagSpec' "GeneralizedNewtypeDeriving"      LangExt.GeneralizedNewtypeDeriving
                                              setGenDeriving,
  flagSpec "ImplicitParams"                   LangExt.ImplicitParams,
  flagSpec "ImplicitPrelude"                  LangExt.ImplicitPrelude,
  flagSpec "ImpredicativeTypes"               LangExt.ImpredicativeTypes,
  flagSpec' "IncoherentInstances"             LangExt.IncoherentInstances
                                              setIncoherentInsts,
  flagSpec "TypeFamilyDependencies"           LangExt.TypeFamilyDependencies,
  flagSpec "InstanceSigs"                     LangExt.InstanceSigs,
  flagSpec "ApplicativeDo"                    LangExt.ApplicativeDo,
  flagSpec "InterruptibleFFI"                 LangExt.InterruptibleFFI,
  flagSpec "JavaScriptFFI"                    LangExt.JavaScriptFFI,
  flagSpec "KindSignatures"                   LangExt.KindSignatures,
  flagSpec "LambdaCase"                       LangExt.LambdaCase,
  flagSpec "LiberalTypeSynonyms"              LangExt.LiberalTypeSynonyms,
  flagSpec "MagicHash"                        LangExt.MagicHash,
  flagSpec "MonadComprehensions"              LangExt.MonadComprehensions,
  flagSpec "MonadFailDesugaring"              LangExt.MonadFailDesugaring,
  flagSpec "MonoLocalBinds"                   LangExt.MonoLocalBinds,
  depFlagSpecCond "MonoPatBinds"              LangExt.MonoPatBinds
    id
         "Experimental feature now removed; has no effect",
  flagSpec "MonomorphismRestriction"          LangExt.MonomorphismRestriction,
  flagSpec "MultiParamTypeClasses"            LangExt.MultiParamTypeClasses,
  flagSpec "MultiWayIf"                       LangExt.MultiWayIf,
  flagSpec "NPlusKPatterns"                   LangExt.NPlusKPatterns,
  flagSpec "NamedFieldPuns"                   LangExt.RecordPuns,
  flagSpec "NamedWildCards"                   LangExt.NamedWildCards,
  flagSpec "NegativeLiterals"                 LangExt.NegativeLiterals,
  flagSpec "NondecreasingIndentation"         LangExt.NondecreasingIndentation,
  depFlagSpec' "NullaryTypeClasses"           LangExt.NullaryTypeClasses
    (deprecatedForExtension "MultiParamTypeClasses"),
  flagSpec "NumDecimals"                      LangExt.NumDecimals,
  depFlagSpecOp "OverlappingInstances"        LangExt.OverlappingInstances
    setOverlappingInsts
    "instead use per-instance pragmas OVERLAPPING/OVERLAPPABLE/OVERLAPS",
  flagSpec "OverloadedLabels"                 LangExt.OverloadedLabels,
  flagSpec "OverloadedLists"                  LangExt.OverloadedLists,
  flagSpec "OverloadedStrings"                LangExt.OverloadedStrings,
  flagSpec "PackageImports"                   LangExt.PackageImports,
  flagSpec "ParallelArrays"                   LangExt.ParallelArrays,
  flagSpec "ParallelListComp"                 LangExt.ParallelListComp,
  flagSpec "PartialTypeSignatures"            LangExt.PartialTypeSignatures,
  flagSpec "PatternGuards"                    LangExt.PatternGuards,
  depFlagSpec' "PatternSignatures"            LangExt.ScopedTypeVariables
    (deprecatedForExtension "ScopedTypeVariables"),
  flagSpec "PatternSynonyms"                  LangExt.PatternSynonyms,
  flagSpec "PolyKinds"                        LangExt.PolyKinds,
  flagSpec "PolymorphicComponents"            LangExt.RankNTypes,
  flagSpec "PostfixOperators"                 LangExt.PostfixOperators,
  flagSpec "QuasiQuotes"                      LangExt.QuasiQuotes,
  flagSpec "Rank2Types"                       LangExt.RankNTypes,
  flagSpec "RankNTypes"                       LangExt.RankNTypes,
  flagSpec "RebindableSyntax"                 LangExt.RebindableSyntax,
  depFlagSpec' "RecordPuns"                   LangExt.RecordPuns
    (deprecatedForExtension "NamedFieldPuns"),
  flagSpec "RecordWildCards"                  LangExt.RecordWildCards,
  flagSpec "RecursiveDo"                      LangExt.RecursiveDo,
  flagSpec "RelaxedLayout"                    LangExt.RelaxedLayout,
  depFlagSpecCond "RelaxedPolyRec"            LangExt.RelaxedPolyRec
    not
         "You can't turn off RelaxedPolyRec any more",
  flagSpec "RoleAnnotations"                  LangExt.RoleAnnotations,
  flagSpec "ScopedTypeVariables"              LangExt.ScopedTypeVariables,
  flagSpec "StandaloneDeriving"               LangExt.StandaloneDeriving,
  flagSpec "StaticPointers"                   LangExt.StaticPointers,
  flagSpec "Strict"                           LangExt.Strict,
  flagSpec "StrictData"                       LangExt.StrictData,
  flagSpec' "TemplateHaskell"                 LangExt.TemplateHaskell
                                              checkTemplateHaskellOk,
  flagSpec "TemplateHaskellQuotes"            LangExt.TemplateHaskellQuotes,
  flagSpec "TraditionalRecordSyntax"          LangExt.TraditionalRecordSyntax,
  flagSpec "TransformListComp"                LangExt.TransformListComp,
  flagSpec "TupleSections"                    LangExt.TupleSections,
  flagSpec "TypeApplications"                 LangExt.TypeApplications,
  flagSpec "TypeInType"                       LangExt.TypeInType,
  flagSpec "TypeFamilies"                     LangExt.TypeFamilies,
  flagSpec "TypeOperators"                    LangExt.TypeOperators,
  flagSpec "TypeSynonymInstances"             LangExt.TypeSynonymInstances,
  flagSpec "UnboxedTuples"                    LangExt.UnboxedTuples,
  flagSpec "UnboxedSums"                      LangExt.UnboxedSums,
  flagSpec "UndecidableInstances"             LangExt.UndecidableInstances,
  flagSpec "UndecidableSuperClasses"          LangExt.UndecidableSuperClasses,
  flagSpec "UnicodeSyntax"                    LangExt.UnicodeSyntax,
  flagSpec "UnliftedFFITypes"                 LangExt.UnliftedFFITypes,
  flagSpec "ViewPatterns"                     LangExt.ViewPatterns
  ]

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

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

    ++ default_PIC platform

    ++ concatMap (wayGeneralFlags platform) (defaultWays settings)

    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.
    _                      -> []

-- General flags that are switched on/off when other general flags are switched
-- on
impliedGFlags :: [(GeneralFlag, TurnOnFlag, GeneralFlag)]
impliedGFlags = [(Opt_DeferTypeErrors, turnOn, Opt_DeferTypedHoles)
                ,(Opt_DeferTypeErrors, turnOn, Opt_DeferOutOfScopeVariables)
                ,(Opt_Strictness, turnOn, Opt_WorkerWrapper)
                ]

-- General flags that are switched on/off when other general flags are switched
-- off
impliedOffGFlags :: [(GeneralFlag, TurnOnFlag, GeneralFlag)]
impliedOffGFlags = [(Opt_Strictness, turnOff, Opt_WorkerWrapper)]

impliedXFlags :: [(LangExt.Extension, TurnOnFlag, LangExt.Extension)]
impliedXFlags
-- See Note [Updating flag description in the User's Guide]
  = [ (LangExt.RankNTypes,                turnOn, LangExt.ExplicitForAll)
    , (LangExt.ScopedTypeVariables,       turnOn, LangExt.ExplicitForAll)
    , (LangExt.LiberalTypeSynonyms,       turnOn, LangExt.ExplicitForAll)
    , (LangExt.ExistentialQuantification, turnOn, LangExt.ExplicitForAll)
    , (LangExt.FlexibleInstances,         turnOn, LangExt.TypeSynonymInstances)
    , (LangExt.FunctionalDependencies,    turnOn, LangExt.MultiParamTypeClasses)
    , (LangExt.MultiParamTypeClasses,     turnOn, LangExt.ConstrainedClassMethods)  -- c.f. Trac #7854
    , (LangExt.TypeFamilyDependencies,    turnOn, LangExt.TypeFamilies)

    , (LangExt.RebindableSyntax, turnOff, LangExt.ImplicitPrelude)      -- NB: turn off!

    , (LangExt.GADTs,            turnOn, LangExt.GADTSyntax)
    , (LangExt.GADTs,            turnOn, LangExt.MonoLocalBinds)
    , (LangExt.TypeFamilies,     turnOn, LangExt.MonoLocalBinds)

    , (LangExt.TypeFamilies,     turnOn, LangExt.KindSignatures)  -- Type families use kind signatures
    , (LangExt.PolyKinds,        turnOn, LangExt.KindSignatures)  -- Ditto polymorphic kinds
    , (LangExt.TypeInType,       turnOn, LangExt.DataKinds)
    , (LangExt.TypeInType,       turnOn, LangExt.PolyKinds)
    , (LangExt.TypeInType,       turnOn, LangExt.KindSignatures)

    -- AutoDeriveTypeable is not very useful without DeriveDataTypeable
    , (LangExt.AutoDeriveTypeable, turnOn, LangExt.DeriveDataTypeable)

    -- We turn this on so that we can export associated type
    -- type synonyms in subordinates (e.g. MyClass(type AssocType))
    , (LangExt.TypeFamilies,     turnOn, LangExt.ExplicitNamespaces)
    , (LangExt.TypeOperators, turnOn, LangExt.ExplicitNamespaces)

    , (LangExt.ImpredicativeTypes,  turnOn, LangExt.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'
    , (LangExt.RecordWildCards,     turnOn, LangExt.DisambiguateRecordFields)

    , (LangExt.ParallelArrays, turnOn, LangExt.ParallelListComp)

    , (LangExt.JavaScriptFFI, turnOn, LangExt.InterruptibleFFI)

    , (LangExt.DeriveTraversable, turnOn, LangExt.DeriveFunctor)
    , (LangExt.DeriveTraversable, turnOn, LangExt.DeriveFoldable)

    -- Duplicate record fields require field disambiguation
    , (LangExt.DuplicateRecordFields, turnOn, LangExt.DisambiguateRecordFields)

    , (LangExt.TemplateHaskell, turnOn, LangExt.TemplateHaskellQuotes)
    , (LangExt.Strict, turnOn, LangExt.StrictData)
  ]

-- 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:
--
--  * utils/mkUserGuidePart/Options/
--  * docs/users_guide/using.rst
--
-- 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_DoEtaReduction)       -- See Note [Eta-reduction in -O0]
    , ([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_CaseFolding)
    , ([1,2],   Opt_CmmElimCommonBlocks)
    , ([1,2],   Opt_CmmSink)
    , ([1,2],   Opt_CSE)
    , ([1,2],   Opt_StgCSE)
    , ([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_CrossModuleSpecialise)
    , ([1,2],   Opt_Strictness)
    , ([1,2],   Opt_UnboxSmallStrictFields)
    , ([1,2],   Opt_CprAnal)
    , ([1,2],   Opt_WorkerWrapper)
    , ([1,2],   Opt_SolveConstantDicts)

    , ([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
    ]

{- Note [Eta-reduction in -O0]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Trac #11562 showed an example which tripped an ASSERT in CoreToStg; a
function was marked as MayHaveCafRefs when in fact it obviously
didn't.  Reason was:
 * Eta reduction wasn't happening in the simplifier, but it was
   happening in CorePrep, on
        $fBla = MkDict (/\a. K a)
 * Result: rhsIsStatic told TidyPgm that $fBla might have CAF refs
   but the eta-reduced version (MkDict K) obviously doesn't
Simple solution: just let the simplifier do eta-reduction even in -O0.
After all, CorePrep does it unconditionally!  Not a big deal, but
removes an assertion failure. -}


-- -----------------------------------------------------------------------------
-- 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:
--
--  * utils/mkUserGuidePart/
--  * docs/users_guide/using-warnings.rst

-- | Warning groups.
--
-- As all warnings are in the Weverything set, it is ignored when
-- displaying to the user which group a warning is in.
warningGroups :: [(String, [WarningFlag])]
warningGroups =
    [ ("compat",       minusWcompatOpts)
    , ("unused-binds", unusedBindsFlags)
    , ("default",      standardWarnings)
    , ("extra",        minusWOpts)
    , ("all",          minusWallOpts)
    , ("everything",   minusWeverythingOpts)
    ]

-- | Warning group hierarchies, where there is an explicit inclusion
-- relation.
--
-- Each inner list is a hierarchy of warning groups, ordered from
-- smallest to largest, where each group is a superset of the one
-- before it.
--
-- Separating this from 'warningGroups' allows for multiple
-- hierarchies with no inherent relation to be defined.
--
-- The special-case Weverything group is not included.
warningHierarchies :: [[String]]
warningHierarchies = hierarchies ++ map (:[]) rest
  where
    hierarchies = [["default", "extra", "all"]]
    rest = filter (`notElem` "everything" : concat hierarchies) $
           map fst warningGroups

-- | Find the smallest group in every hierarchy which a warning
-- belongs to, excluding Weverything.
smallestGroups :: WarningFlag -> [String]
smallestGroups flag = mapMaybe go warningHierarchies where
    -- Because each hierarchy is arranged from smallest to largest,
    -- the first group we find in a hierarchy which contains the flag
    -- is the smallest.
    go (group:rest) = fromMaybe (go rest) $ do
        flags <- lookup group warningGroups
        guard (flag `elem` flags)
        pure (Just group)
    go [] = Nothing

-- | Warnings enabled unless specified otherwise
standardWarnings :: [WarningFlag]
standardWarnings -- see Note [Documenting warning flags]
    = [ Opt_WarnOverlappingPatterns,
        Opt_WarnWarningsDeprecations,
        Opt_WarnDeprecatedFlags,
        Opt_WarnDeferredTypeErrors,
        Opt_WarnTypedHoles,
        Opt_WarnDeferredOutOfScopeVariables,
        Opt_WarnPartialTypeSignatures,
        Opt_WarnUnrecognisedPragmas,
        Opt_WarnDuplicateExports,
        Opt_WarnOverflowedLiterals,
        Opt_WarnEmptyEnumerations,
        Opt_WarnMissingFields,
        Opt_WarnMissingMethods,
        Opt_WarnWrongDoBind,
        Opt_WarnUnsupportedCallingConventions,
        Opt_WarnDodgyForeignImports,
        Opt_WarnInlineRuleShadowing,
        Opt_WarnAlternativeLayoutRuleTransitional,
        Opt_WarnUnsupportedLlvmVersion,
        Opt_WarnTabs,
        Opt_WarnUnrecognisedWarningFlags,
        Opt_WarnSimplifiableClassConstraints
      ]

-- | Things you get with -W
minusWOpts :: [WarningFlag]
minusWOpts
    = standardWarnings ++
      [ Opt_WarnUnusedTopBinds,
        Opt_WarnUnusedLocalBinds,
        Opt_WarnUnusedPatternBinds,
        Opt_WarnUnusedMatches,
        Opt_WarnUnusedForalls,
        Opt_WarnUnusedImports,
        Opt_WarnIncompletePatterns,
        Opt_WarnDodgyExports,
        Opt_WarnDodgyImports,
        Opt_WarnUnbangedStrictPatterns
      ]

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

-- | Things you get with -Weverything, i.e. *all* known warnings flags
minusWeverythingOpts :: [WarningFlag]
minusWeverythingOpts = [ toEnum 0 .. ]

-- | Things you get with -Wcompat.
--
-- This is intended to group together warnings that will be enabled by default
-- at some point in the future, so that library authors eager to make their
-- code future compatible to fix issues before they even generate warnings.
minusWcompatOpts :: [WarningFlag]
minusWcompatOpts
    = [ Opt_WarnMissingMonadFailInstances
      , Opt_WarnSemigroup
      , Opt_WarnNonCanonicalMonoidInstances
      ]

enableUnusedBinds :: DynP ()
enableUnusedBinds = mapM_ setWarningFlag unusedBindsFlags

disableUnusedBinds :: DynP ()
disableUnusedBinds = mapM_ unSetWarningFlag unusedBindsFlags

-- Things you get with -Wunused-binds
unusedBindsFlags :: [WarningFlag]
unusedBindsFlags = [ Opt_WarnUnusedTopBinds
                   , Opt_WarnUnusedLocalBinds
                   , Opt_WarnUnusedPatternBinds
                   ]

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

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

glasgowExtsFlags :: [LangExt.Extension]
glasgowExtsFlags = [
             LangExt.ConstrainedClassMethods
           , LangExt.DeriveDataTypeable
           , LangExt.DeriveFoldable
           , LangExt.DeriveFunctor
           , LangExt.DeriveGeneric
           , LangExt.DeriveTraversable
           , LangExt.EmptyDataDecls
           , LangExt.ExistentialQuantification
           , LangExt.ExplicitNamespaces
           , LangExt.FlexibleContexts
           , LangExt.FlexibleInstances
           , LangExt.ForeignFunctionInterface
           , LangExt.FunctionalDependencies
           , LangExt.GeneralizedNewtypeDeriving
           , LangExt.ImplicitParams
           , LangExt.KindSignatures
           , LangExt.LiberalTypeSynonyms
           , LangExt.MagicHash
           , LangExt.MultiParamTypeClasses
           , LangExt.ParallelListComp
           , LangExt.PatternGuards
           , LangExt.PostfixOperators
           , LangExt.RankNTypes
           , LangExt.RecursiveDo
           , LangExt.ScopedTypeVariables
           , LangExt.StandaloneDeriving
           , LangExt.TypeOperators
           , LangExt.TypeSynonymInstances
           , LangExt.UnboxedTuples
           , LangExt.UnicodeSyntax
           , LangExt.UnliftedFFITypes ]

foreign import ccall unsafe "rts_isProfiled" rtsIsProfiledIO :: IO CInt

-- | Was the runtime system built with profiling enabled?
rtsIsProfiled :: Bool
rtsIsProfiled = unsafeDupablePerformIO rtsIsProfiledIO /= 0

-- 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

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 })

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

checkTemplateHaskellOk :: TurnOnFlag -> DynP ()
checkTemplateHaskellOk _turn_on
  = getCurLoc >>= \l -> upd (\d -> d { thOnLoc = l })

{- **********************************************************************
%*                                                                      *
                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))

intSuffixM :: (Int -> DynFlags -> DynP DynFlags) -> OptKind (CmdLineP DynFlags)
intSuffixM fn = IntSuffix (\n -> updM (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 = foldr setGeneralFlag' dflags1
                                        (wayGeneralFlags platform w)
                        dflags3 = foldr unSetGeneralFlag' dflags2
                                        (wayUnsetGeneralFlags platform w)
                    in dflags3

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 = foldr ($) (gopt_unset dflags f) deps
  where
    deps = [ if turn_on then setGeneralFlag' d
                        else unSetGeneralFlag' d
           | (f', turn_on, d) <- impliedOffGFlags, f' == f ]
   -- In general, when you un-set f, we don't un-set the things it implies.
   -- There are however some exceptions, e.g., -fno-strictness implies
   -- -fno-worker-wrapper.
   --
   -- NB: use unSetGeneralFlag' recursively, in case the implied off flags
   --     imply further flags.

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

setFatalWarningFlag, unSetFatalWarningFlag :: WarningFlag -> DynP ()
setFatalWarningFlag   f = upd (\dfs -> wopt_set_fatal dfs f)
unSetFatalWarningFlag f = upd (\dfs -> wopt_unset_fatal dfs f)

--------------------------
setExtensionFlag, unSetExtensionFlag :: LangExt.Extension -> DynP ()
setExtensionFlag f = upd (setExtensionFlag' f)
unSetExtensionFlag f = upd (unSetExtensionFlag' f)

setExtensionFlag', unSetExtensionFlag' :: LangExt.Extension -> 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,
                                             Opt_D_no_debug_output]

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 })

setDebugLevel :: Maybe Int -> DynP ()
setDebugLevel mb_n = upd (\dfs -> dfs{ debugLevel = mb_n `orElse` 2 })

data PkgConfRef
  = GlobalPkgConf
  | UserPkgConf
  | PkgConfFile FilePath
  deriving Eq

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

removeUserPkgConf :: DynP ()
removeUserPkgConf = upd $ \s ->
  s { packageDBFlags = NoUserPackageDB : packageDBFlags s }

removeGlobalPkgConf :: DynP ()
removeGlobalPkgConf = upd $ \s ->
 s { packageDBFlags = NoGlobalPackageDB : packageDBFlags s }

clearPkgConf :: DynP ()
clearPkgConf = upd $ \s ->
  s { packageDBFlags = ClearPackageDBs : packageDBFlags s }

parsePackageFlag :: String                 -- the flag
                 -> ReadP PackageArg       -- type of argument
                 -> String                 -- string to parse
                 -> PackageFlag
parsePackageFlag flag arg_parse str
 = case filter ((=="").snd) (readP_to_S parse str) of
    [(r, "")] -> r
    _ -> throwGhcException $ CmdLineError ("Can't parse package flag: " ++ str)
  where doc = flag ++ " " ++ str
        parse = do
            pkg_arg <- tok arg_parse
            let mk_expose = ExposePackage doc pkg_arg
            ( do _ <- tok $ string "with"
                 fmap (mk_expose . ModRenaming True) parseRns
             <++ fmap (mk_expose . ModRenaming False) parseRns
             <++ return (mk_expose (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, hidePackage,
        exposePluginPackage, exposePluginPackageId,
        ignorePackage,
        trustPackage, distrustPackage :: String -> DynP ()
exposePackage p = upd (exposePackage' p)
exposePackageId p =
  upd (\s -> s{ packageFlags =
    parsePackageFlag "-package-id" parseUnitIdArg p : packageFlags s })
exposePluginPackage p =
  upd (\s -> s{ pluginPackageFlags =
    parsePackageFlag "-plugin-package" parsePackageArg p : pluginPackageFlags s })
exposePluginPackageId p =
  upd (\s -> s{ pluginPackageFlags =
    parsePackageFlag "-plugin-package-id" parseUnitIdArg p : pluginPackageFlags s })
hidePackage p =
  upd (\s -> s{ packageFlags = HidePackage p : packageFlags s })
ignorePackage p =
  upd (\s -> s{ ignorePackageFlags = IgnorePackage p : ignorePackageFlags s })

trustPackage p = exposePackage p >> -- both trust and distrust also expose a package
  upd (\s -> s{ trustFlags = TrustPackage p : trustFlags s })
distrustPackage p = exposePackage p >>
  upd (\s -> s{ trustFlags = DistrustPackage p : trustFlags s })

exposePackage' :: String -> DynFlags -> DynFlags
exposePackage' p dflags
    = dflags { packageFlags =
            parsePackageFlag "-package" parsePackageArg p : packageFlags dflags }

parsePackageArg :: ReadP PackageArg
parsePackageArg =
    fmap PackageArg (munch1 (\c -> isAlphaNum c || c `elem` ":-_."))

parseUnitIdArg :: ReadP PackageArg
parseUnitIdArg =
    fmap UnitIdArg parseUnitId

setUnitId :: String -> DynFlags -> DynFlags
setUnitId p d = d { thisInstalledUnitId = stringToInstalledUnitId p }

-- | Given a 'ModuleName' of a signature in the home library, find
-- out how it is instantiated.  E.g., the canonical form of
-- A in @p[A=q[]:A]@ is @q[]:A@.
canonicalizeHomeModule :: DynFlags -> ModuleName -> Module
canonicalizeHomeModule dflags mod_name =
    case lookup mod_name (thisUnitIdInsts dflags) of
        Nothing  -> mkModule (thisPackage dflags) mod_name
        Just mod -> mod


-- -----------------------------------------------------------------------------
-- | 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 file like
--
-- > clear-package-db
-- > global-package-db
-- > package-db blah/package.conf.d
-- > package-id id1
-- > package-id id2
--
-- we interpret this as
--
-- > [ -hide-all-packages
-- > , -clear-package-db
-- > , -global-package-db
-- > , -package-db blah/package.conf.d
-- > , -package-id id1
-- > , -package-id id2
-- > ]
--
-- There's also an older syntax alias for package-id, which is just an
-- unadorned package id
--
-- > id1
-- > id2
--
interpretPackageEnv :: DynFlags -> IO DynFlags
interpretPackageEnv dflags = do
    mPkgEnv <- runMaybeT $ msum $ [
                   getCmdLineArg >>= \env -> msum [
                       probeEnvFile env
                     , probeEnvName env
                     , cmdLineError env
                     ]
                 , getEnvVar >>= \env -> msum [
                       probeEnvFile env
                     , probeEnvName env
                     , envError     env
                     ]
                 , notIfHideAllPackages >> msum [
                       findLocalEnvFile >>= probeEnvFile
                     , probeEnvName defaultEnvName
                     ]
                 ]
    case mPkgEnv of
      Nothing ->
        -- No environment found. Leave DynFlags unchanged.
        return dflags
      Just envfile -> do
        content <- readFile envfile
        let setFlags :: DynP ()
            setFlags = do
              setGeneralFlag Opt_HideAllPackages
              parseEnvFile envfile content

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

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

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

    probeEnvName :: String -> MaybeT IO FilePath
    probeEnvName name = probeEnvFile =<< namedEnvPath name

    probeEnvFile :: FilePath -> MaybeT IO FilePath
    probeEnvFile path = do
      guard =<< liftMaybeT (doesFileExist path)
      return path

    parseEnvFile :: FilePath -> String -> DynP ()
    parseEnvFile envfile = mapM_ parseEntry . lines
      where
        parseEntry str = case words str of
          ("package-db": _)     -> addPkgConfRef (PkgConfFile (envdir </> db))
            -- relative package dbs are interpreted relative to the env file
            where envdir = takeDirectory envfile
                  db     = drop 11 str
          ["clear-package-db"]  -> clearPkgConf
          ["global-package-db"] -> addPkgConfRef GlobalPkgConf
          ["user-package-db"]   -> addPkgConfRef UserPkgConf
          ["package-id", pkgid] -> exposePackageId pkgid
          (('-':'-':_):_)       -> return () -- comments
          -- and the original syntax introduced in 7.10:
          [pkgid]               -> exposePackageId pkgid
          []                    -> return ()
          _                     -> throwGhcException $ CmdLineError $
                                        "Can't parse environment file entry: "
                                     ++ envfile ++ ": " ++ str

    -- 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

    notIfHideAllPackages :: MaybeT IO ()
    notIfHideAllPackages =
      guard (not (gopt Opt_HideAllPackages dflags))

    defaultEnvName :: String
    defaultEnvName = "default"

    -- e.g. .ghc.environment.x86_64-linux-7.6.3
    localEnvFileName :: FilePath
    localEnvFileName = ".ghc.environment" <.> versionedFilePath dflags

    -- Search for an env file, starting in the current dir and looking upwards.
    -- Fail if we get to the users home dir or the filesystem root. That is,
    -- we don't look for an env file in the user's home dir. The user-wide
    -- env lives in ghc's versionedAppDir/environments/default
    findLocalEnvFile :: MaybeT IO FilePath
    findLocalEnvFile = do
        curdir  <- liftMaybeT getCurrentDirectory
        homedir <- tryMaybeT getHomeDirectory
        let probe dir | isDrive dir || dir == homedir
                      = mzero
            probe dir = do
              let file = dir </> localEnvFileName
              exists <- liftMaybeT (doesFileExist file)
              if exists
                then return file
                else probe (takeDirectory dir)
        probe curdir

    -- 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_ENVIRONMENT) 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 mainUnitId (mkModuleName main_mod) }

  | isUpper (head arg)  -- The arg looked like "Foo" or "Foo.Bar"
  = upd $ \d -> d { mainModIs = mkModule mainUnitId (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 || WayDyn `elem` ways 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),
       ("RTS expects libdw",           showBool cGhcRtsWithLibdw),
       -- Whether or not we support @-dynamic-too@
       ("Support dynamic-too",         showBool $ not isWindows),
       -- Whether or not we support the @-j@ flag with @--make@.
       ("Support parallel --make",     "YES"),
       -- Whether or not we support "Foo from foo-0.1-XXX:Foo" syntax in
       -- installed package info.
       ("Support reexported-modules",  "YES"),
       -- Whether or not we support extended @-package foo (Foo)@ syntax.
       ("Support thinning and renaming package flags", "YES"),
       -- Whether or not we support Backpack.
       ("Support Backpack", "YES"),
       -- If true, we require that the 'id' field in installed package info
       -- match what is passed to the @-this-unit-id@ flag for modules
       -- built in it
       ("Requires unified installed package IDs", "YES"),
       -- Whether or not we support the @-this-package-key@ flag.  Prefer
       -- "Uses unit IDs" over it.
       ("Uses package keys",           "YES"),
       -- Whether or not we support the @-this-unit-id@ flag
       ("Uses unit IDs",               "YES"),
       -- Whether or not GHC compiles libraries as dynamic by default
       ("Dynamic by default",          showBool $ dYNAMIC_BY_DEFAULT dflags),
       -- Whether or not GHC was compiled using -dynamic
       ("GHC Dynamic",                 showBool dynamicGhc),
       -- Whether or not GHC was compiled using -prof
       ("GHC Profiled",                showBool rtsIsProfiled),
       ("Leading underscore",          cLeadingUnderscore),
       ("Debug on",                    show debugIsOn),
       ("LibDir",                      topDir dflags),
       -- The path of the global package database used by GHC
       ("Global Package DB",           systemPackageConfig dflags)
      ]
  where
    showBool True  = "YES"
    showBool False = "NO"
    isWindows = platformOS (targetPlatform dflags) == OSMinGW32

-- Produced by deriveConstants
#include "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)


{- -----------------------------------------------------------------------------
Note [DynFlags consistency]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

There are a number of number of DynFlags configurations which either
do not make sense or lead to unimplemented or buggy codepaths in the
compiler. makeDynFlagsConsistent is responsible for verifying the validity
of a set of DynFlags, fixing any issues, and reporting them back to the
caller.

GHCi and -O
---------------

When using optimization, the compiler can introduce several things
(such as unboxed tuples) into the intermediate code, which GHCi later
chokes on since the bytecode interpreter can't handle this (and while
this is arguably a bug these aren't handled, there are no plans to fix
it.)

While the driver pipeline always checks for this particular erroneous
combination when parsing flags, we also need to check when we update
the flags; this is because API clients may parse flags but update the
DynFlags afterwords, before finally running code inside a session (see
T10052 and #10052).
-}

-- | Resolve any internal inconsistencies in a set of 'DynFlags'.
-- Returns the consistent 'DynFlags' as well as a list of warnings
-- to report to the user.
makeDynFlagsConsistent :: DynFlags -> (DynFlags, [Located String])
-- 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 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
 | gopt Opt_Hpc dflags && hscTarget dflags == HscInterpreted
    = let dflags' = gopt_unset dflags Opt_Hpc
          warn = "Hpc can't be used with byte-code interpreter. Ignoring -fhpc."
      in loop dflags' warn
 | hscTarget dflags `elem` [HscAsm, HscLlvm] &&
   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)) &&
   (gopt Opt_PIC dflags || WayDyn `elem` ways 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"
 | Left err <- checkOptLevel (optLevel dflags) dflags
    = loop (updOptLevel 0 dflags) err

 | LinkInMemory <- ghcLink dflags
 , not (gopt Opt_ExternalInterpreter dflags)
 , rtsIsProfiled
 , isObjectTarget (hscTarget dflags)
 , WayProf `notElem` ways dflags
    = loop dflags{ways = WayProf : ways dflags}
         "Enabling -prof, because -fobject-code is enabled and GHCi is profiled"

 | 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!

-- | This is the value that 'unsafeGlobalDynFlags' takes before it is
-- initialized.
defaultGlobalDynFlags :: DynFlags
defaultGlobalDynFlags =
    (defaultDynFlags settings) { verbosity = 2 }
  where
    settings = panic "v_unsafeGlobalDynFlags: not initialised"

#if STAGE < 2
GLOBAL_VAR(v_unsafeGlobalDynFlags, defaultGlobalDynFlags, DynFlags)
#else
SHARED_GLOBAL_VAR( v_unsafeGlobalDynFlags
                 , getOrSetLibHSghcGlobalDynFlags
                 , "getOrSetLibHSghcGlobalDynFlags"
                 , defaultGlobalDynFlags
                 , DynFlags )
#endif

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]
  | AixLD    [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 ()