7.6. Flag reference

This section is a quick-reference for GHC’s command-line flags. For each flag, we also list its static/dynamic status (see Static, Dynamic, and Mode options), and the flag’s opposite (if available).

7.6.1. Verbosity options

More details in Verbosity options

Flag

Description

Type

Reverse

-v

verbose mode (equivalent to -v3)

dynamic

-v ⟨n⟩

set verbosity level

dynamic

-fhide-source-paths

hide module source and object paths

dynamic

-fprint-potential-instances

display all available instances in type error messages

dynamic

-fno-print-potential-instances

-fprint-explicit-foralls

Print explicit forall quantification in types. See also -XExplicitForAll

dynamic

-fno-print-explicit-foralls

-fprint-explicit-kinds

Print explicit kind foralls and kind arguments in types. See also -XKindSignatures

dynamic

-fno-print-explicit-kinds

-fprint-explicit-runtime-reps

Print RuntimeRep variables in types which are runtime-representation polymorphic.

dynamic

-fno-print-explicit-runtime-reps

-fprint-unicode-syntax

Use unicode syntax when printing expressions, types and kinds. See also -XUnicodeSyntax

dynamic

-fno-print-unicode-syntax

-fprint-expanded-synonyms

In type errors, also print type-synonym-expanded types.

dynamic

-fno-print-expanded-synonyms

-fprint-typechecker-elaboration

Print extra information from typechecker.

dynamic

-fno-print-typechecker-elaboration

-fdiagnostics-color=(always|auto|never)

Use colors in error messages

dynamic

-f[no-]diagnostics-show-caret

Whether to show snippets of original source code

dynamic

-ferror-spans

Output full span in error messages

dynamic

-Rghc-timing

Summarise timing stats for GHC (same as +RTS -tstderr).

dynamic

-fshow-hole-constraints

Show constraints when reporting typed holes

dynamic

-fshow-loaded-modules

Show the names of modules that GHCi loaded after a :load command.

dynamic

7.6.2. Alternative modes of operation

More details in Modes of operation

Flag

Description

Type

Reverse

--help, -?

Display help

mode

--interactive

Interactive mode - normally used by just running ghci; see Using GHCi for details.

mode

--make

Build a multi-module Haskell program, automatically figuring out dependencies. Likely to be much easier, and faster, than using make; see Using ghc --make for details.

mode

-e ⟨expr⟩

Evaluate expr; see Expression evaluation mode for details.

mode

--show-iface ⟨file⟩

display the contents of an interface file.

mode

-M

generate dependency information suitable for use in a Makefile; see Dependency generation for details.

mode

--frontend ⟨module⟩

run GHC with the given frontend plugin; see Frontend plugins for details.

mode

--supported-extensions, --supported-languages

display the supported language extensions

mode

--show-options

display the supported command line options

mode

--info

display information about the compiler

mode

--version, -V

display GHC version

mode

--numeric-version

display GHC version (numeric only)

mode

--print-libdir

display GHC library directory

mode

7.6.3. Which phases to run

More details in Batch compiler mode

Flag

Description

Type

Reverse

-F

Enable the use of a pre-processor (set with -pgmF ⟨cmd⟩)

dynamic

-E

Stop after preprocessing (.hspp file)

mode

-C

Stop after generating C (.hc file)

mode

-S

Stop after generating assembly (.s file)

mode

-c

Stop after generating object (.o) file

mode

-x ⟨suffix⟩

Override default behaviour for source files

dynamic

7.6.4. Redirecting output

More details in Redirecting the compilation output(s)

Flag

Description

Type

Reverse

-hcsuf ⟨suffix⟩

set the suffix to use for intermediate C files

dynamic

-hidir ⟨dir⟩

set directory for interface files

dynamic

-hisuf ⟨suffix⟩

set the suffix to use for interface files

dynamic

-o ⟨file⟩

set output filename

dynamic

-odir ⟨dir⟩

set directory for object files

dynamic

-ohi ⟨file⟩

set the filename in which to put the interface

dynamic

-osuf ⟨suffix⟩

set the output file suffix

dynamic

-stubdir ⟨dir⟩

redirect FFI stub files

dynamic

-dumpdir ⟨dir⟩

redirect dump files

dynamic

-outputdir ⟨dir⟩

set output directory

dynamic

-dyno ⟨file⟩

Set the output filename for dynamic object files (see -dynamic-too)

dynamic

-dynosuf ⟨suffix⟩

Set the object suffix for dynamic object files (see -dynamic-too)

dynamic

-dynhisuf ⟨suffix⟩

Set the hi suffix for dynamic object files (see -dynamic-too)

dynamic

7.6.5. Keeping intermediate files

More details in Keeping Intermediate Files

Flag

Description

Type

Reverse

-keep-hc-file, -keep-hc-files

Retain intermediate .hc files.

dynamic

-keep-hi-files

Retain intermediate .hi files (the default).

dynamic

-no-keep-hi-files

-keep-llvm-file, -keep-llvm-files

Retain intermediate LLVM .ll files. Implies -fllvm.

dynamic

-keep-o-files

Retain intermediate .o files (the default).

dynamic

-no-keep-o-files

-keep-s-file, -keep-s-files

Retain intermediate .s files.

dynamic

-keep-tmp-files

Retain all intermediate temporary files.

dynamic

7.6.6. Temporary files

More details in Redirecting temporary files

Flag

Description

Type

Reverse

-tmpdir ⟨dir⟩

set the directory for temporary files

dynamic

7.6.7. Finding imports

More details in The search path

Flag

Description

Type

Reverse

-i⟨dir⟩[:⟨dir⟩]*

add ⟨dir⟩, ⟨dir2⟩, etc. to import path

dynamic/:set

-i

Empty the import directory list

dynamic/:set

7.6.8. Interface file options

More details in Other options related to interface files

Flag

Description

Type

Reverse

-ddump-hi

Dump the new interface to stdout

dynamic

-ddump-hi-diffs

Show the differences vs. the old interface

dynamic

-ddump-minimal-imports

Dump a minimal set of imports

dynamic

--show-iface ⟨file⟩

See Modes of operation.

mode

7.6.9. Recompilation checking

More details in The recompilation checker

Flag

Description

Type

Reverse

-fforce-recomp

Turn off recompilation checking. This is implied by any -ddump-X option when compiling a single file (i.e. when using -c).

dynamic

-fno-force-recomp

7.6.10. Interactive-mode options

More details in The .ghci and .haskeline files

Flag

Description

Type

Reverse

-ignore-dot-ghci

Disable reading of .ghci files

dynamic

-ghci-script

Read additional .ghci files

dynamic

-fbreak-on-error

Break on uncaught exceptions and errors

dynamic

-fno-break-on-error

-fbreak-on-exception

Break on any exception thrown

dynamic

-fno-break-on-exception

-fghci-hist-size=⟨n⟩

Set the number of entries GHCi keeps for :history. See The GHCi Debugger.

dynamic

-fprint-evld-with-show

Enable usage of Show instances in :print. See Breakpoints and inspecting variables.

dynamic

-fno-print-evld-with-show

-fprint-bind-result

Turn on printing of binding results in GHCi

dynamic

-fno-print-bind-result

-fno-print-bind-contents

Turn off printing of binding contents in GHCi

dynamic

-fno-implicit-import-qualified

Turn off implicit qualified import of everything in GHCi

dynamic

-interactive-print ⟨expr⟩

Select the function to use for printing evaluated expressions in GHCi

dynamic

7.6.11. Packages

More details in Packages

Flag

Description

Type

Reverse

-this-unit-id ⟨unit-id⟩

Compile to be part of unit (i.e. package) ⟨unit-id⟩

dynamic

-package ⟨pkg⟩

Expose package ⟨pkg⟩

dynamic/:set

-hide-all-packages

Hide all packages by default

dynamic

-hide-package ⟨pkg⟩

Hide package ⟨pkg⟩

dynamic/:set

-ignore-package ⟨pkg⟩

Ignore package ⟨pkg⟩

dynamic/:set

-package-db ⟨file⟩

Add ⟨file⟩ to the package db stack.

dynamic

-clear-package-db

Clear the package db stack.

dynamic

-no-global-package-db

Remove the global package db from the stack.

dynamic

-global-package-db

Add the global package db to the stack.

dynamic

-no-user-package-db

Remove the user’s package db from the stack.

dynamic

-user-package-db

Add the user’s package db to the stack.

dynamic

-no-auto-link-packages

Don’t automatically link in the base and rts packages.

dynamic

-trust ⟨pkg⟩

Expose package ⟨pkg⟩ and set it to be trusted

dynamic/:set

-distrust ⟨pkg⟩

Expose package ⟨pkg⟩ and set it to be distrusted

dynamic/:set

-distrust-all

Distrust all packages by default

dynamic/:set

-package-env ⟨file⟩|⟨name⟩

Use the specified package environment.

dynamic

7.6.12. Language options

Language options can be enabled either by a command-line option -Xblah, or by a {-# LANGUAGE blah #-} pragma in the file itself. See Language options. Some options are enabled using -f* flags.

Flag

Description

Type

Reverse

-fconstraint-solver-iterations=⟨n⟩

default: 4. Set the iteration limit for the type-constraint solver. Typically one iteration suffices; so please yell if you find you need to set it higher than the default. Zero means infinity.

dynamic

-freduction-depth=⟨n⟩

default: 200. Set the limit for type simplification. Zero means infinity.

dynamic

-fcontext-stack=⟨n⟩

Deprecated. Use -freduction-depth=⟨n⟩ instead.

dynamic

-fglasgow-exts

Deprecated. Enable most language extensions; see Language options for exactly which ones.

dynamic

-fno-glasgow-exts

-firrefutable-tuples

Make tuple pattern matching irrefutable

dynamic

-fno-irrefutable-tuples

-fpackage-trust

Enable Safe Haskell trusted package requirement for trustworthy modules.

dynamic

-ftype-function-depth=⟨n⟩

Deprecated. Use -freduction-depth=⟨n⟩ instead.

dynamic

-XAllowAmbiguousTypes

Allow the user to write ambiguous types, and the type inference engine to infer them.

dynamic

-XNoAllowAmbiguousTypes

-XArrows

Enable arrow notation extension

dynamic

-XNoArrows

-XApplicativeDo

Enable Applicative do-notation desugaring

dynamic

-XNoApplicativeDo

-XAutoDeriveTypeable

As of GHC 7.10, this option is not needed, and should not be used. Previously this would automatically derive Typeable instances for every datatype and type class declaration. Implies -XDeriveDataTypeable.

dynamic

-XNoAutoDeriveTypeable

-XBangPatterns

Enable bang patterns.

dynamic

-XNoBangPatterns

-XBinaryLiterals

Enable support for binary literals.

dynamic

-XNoBinaryLiterals

-XCApiFFI

Enable the CAPI calling convention.

dynamic

-XNoCAPIFFI

-XConstrainedClassMethods

Enable constrained class methods.

dynamic

-XNoConstrainedClassMethods

-XConstraintKinds

Enable a kind of constraints.

dynamic

-XNoConstraintKinds

-XCPP

Enable the C preprocessor.

dynamic

-XNoCPP

-XDataKinds

Enable datatype promotion.

dynamic

-XNoDataKinds

-XDefaultSignatures

Enable default signatures.

dynamic

-XNoDefaultSignatures

-XDeriveAnyClass

Enable deriving for any class.

dynamic

-XNoDeriveAnyClass

-XDeriveDataTypeable

Enable deriving for the Data class. Implied by -XAutoDeriveTypeable.

dynamic

-XNoDeriveDataTypeable

-XDeriveFunctor

Enable deriving for the Functor class. Implied by -XDeriveTraversable.

dynamic

-XNoDeriveFunctor

-XDeriveFoldable

Enable deriving for the Foldable class. Implied by -XDeriveTraversable.

dynamic

-XNoDeriveFoldable

-XDeriveGeneric

Enable deriving for the Generic class.

dynamic

-XNoDeriveGeneric

-XDeriveGeneric

Enable deriving for the Generic class.

dynamic

-XNoDeriveGeneric

-XDeriveLift

Enable deriving for the Lift class

dynamic

-XNoDeriveLift

-XDeriveTraversable

Enable deriving for the Traversable class. Implies -XDeriveFunctor and -XDeriveFoldable.

dynamic

-XNoDeriveTraversable

-XDerivingStrategies

Enables deriving strategies.

dynamic

-XNoDerivingStrategies

-XDisambiguateRecordFields

Enable record field disambiguation. Implied by -XRecordWildCards.

dynamic

-XNoDisambiguateRecordFields

-XEmptyCase

Allow empty case alternatives.

dynamic

-XNoEmptyCase

-XEmptyDataDecls

Enable empty data declarations.

dynamic

-XNoEmptyDataDecls

-XExistentialQuantification

Enable existential quantification.

dynamic

-XNoExistentialQuantification

-XExplicitForAll

Enable explicit universal quantification. Implied by -XScopedTypeVariables, -XLiberalTypeSynonyms, -XRankNTypes and -XExistentialQuantification.

dynamic

-XNoExplicitForAll

-XExplicitNamespaces

Enable using the keyword type to specify the namespace of entries in imports and exports (Explicit namespaces in import/export). Implied by -XTypeOperators and -XTypeFamilies.

dynamic

-XNoExplicitNamespaces

-XExtendedDefaultRules

Use GHCi’s extended default rules in a normal module.

dynamic

-XNoExtendedDefaultRules

-XFlexibleContexts

Enable flexible contexts. Implied by -XImplicitParams.

dynamic

-XNoFlexibleContexts

-XFlexibleInstances

Enable flexible instances. Implies -XTypeSynonymInstances. Implied by -XImplicitParams.

dynamic

-XNoFlexibleInstances

-XForeignFunctionInterface

Enable foreign function interface.

dynamic

-XNoForeignFunctionInterface

-XFunctionalDependencies

Enable functional dependencies. Implies -XMultiParamTypeClasses.

dynamic

-XNoFunctionalDependencies

-XGADTs

Enable generalised algebraic data types. Implies -XGADTSyntax and -XMonoLocalBinds.

dynamic

-XNoGADTs

-XGADTSyntax

Enable generalised algebraic data type syntax.

dynamic

-XNoGADTSyntax

-XGeneralizedNewtypeDeriving

Enable newtype deriving.

dynamic

-XNoGeneralizedNewtypeDeriving

-XGenerics

Deprecated, does nothing. No longer enables generic classes. See also GHC’s support for generic programming.

dynamic

-XNoGenerics

-XImplicitParams

Enable Implicit Parameters. Implies -XFlexibleContexts and -XFlexibleInstances.

dynamic

-XNoImplicitParams

-XNoImplicitPrelude

Don’t implicitly import Prelude. Implied by -XRebindableSyntax.

dynamic

-XImplicitPrelude

-XImpredicativeTypes

Enable impredicative types. Implies -XRankNTypes.

dynamic

-XNoImpredicativeTypes

-XIncoherentInstances

Enable incoherent instances. Implies -XOverlappingInstances.

dynamic

-XNoIncoherentInstances

-XTypeFamilyDependencies

Enable injective type families. Implies -XTypeFamilies.

dynamic

-XNoTypeFamilyDependencies

-XInstanceSigs

Enable instance signatures.

dynamic

-XNoInstanceSigs

-XInterruptibleFFI

Enable interruptible FFI.

dynamic

-XNoInterruptibleFFI

-XKindSignatures

Enable kind signatures. Implied by -XTypeFamilies and -XPolyKinds.

dynamic

-XNoKindSignatures

-XLambdaCase

Enable lambda-case expressions.

dynamic

-XNoLambdaCase

-XLiberalTypeSynonyms

Enable liberalised type synonyms.

dynamic

-XNoLiberalTypeSynonyms

-XMagicHash

Allow # as a postfix modifier on identifiers.

dynamic

-XNoMagicHash

-XMonadComprehensions

Enable monad comprehensions.

dynamic

-XNoMonadComprehensions

-XMonoLocalBinds

Enable do not generalise local bindings. Implied by -XTypeFamilies and -XGADTs.

dynamic

-XNoMonoLocalBinds

-XNoMonomorphismRestriction

Disable the monomorphism restriction.

dynamic

-XMonomorphismRestriction

-XMultiParamTypeClasses

Enable multi parameter type classes. Implied by -XFunctionalDependencies.

dynamic

-XNoMultiParamTypeClasses

-XMultiWayIf

Enable multi-way if-expressions.

dynamic

-XNoMultiWayIf

-XNamedFieldPuns

Enable record puns.

dynamic

-XNoNamedFieldPuns

-XNamedWildCards

Enable named wildcards.

dynamic

-XNoNamedWildCards

-XNegativeLiterals

Enable support for negative literals.

dynamic

-XNoNegativeLiterals

-XNPlusKPatterns

Enable support for n+k patterns. Implied by -XHaskell98.

dynamic

-XNoNPlusKPatterns

-XNullaryTypeClasses

Deprecated, does nothing. nullary (no parameter) type classes are now enabled using -XMultiParamTypeClasses.

dynamic

-XNoNullaryTypeClasses

-XNumDecimals

Enable support for ‘fractional’ integer literals.

dynamic

-XNoNumDecimals

-XOverlappingInstances

Enable overlapping instances.

dynamic

-XNoOverlappingInstances

-XOverloadedLabels

Enable overloaded labels.

dynamic

-XNoOverloadedLabels

-XOverloadedLists

Enable overloaded lists.

dynamic

-XNoOverloadedLists

-XOverloadedStrings

Enable overloaded string literals.

dynamic

-XNoOverloadedStrings

-XPackageImports

Enable package-qualified imports.

dynamic

-XNoPackageImports

-XParallelArrays

Enable parallel arrays. Implies -XParallelListComp.

dynamic

-XNoParallelArrays

-XParallelListComp

Enable parallel list comprehensions. Implied by -XParallelArrays.

dynamic

-XNoParallelListComp

-XPartialTypeSignatures

Enable partial type signatures.

dynamic

-XNoPartialTypeSignatures

-XNoPatternGuards

Disable pattern guards. Implied by -XHaskell98.

dynamic

-XPatternGuards

-XPatternSynonyms

Enable pattern synonyms.

dynamic

-XNoPatternSynonyms

-XPolyKinds

Enable kind polymorphism. Implies -XKindSignatures.

dynamic

-XNoPolyKinds

-XPolymorphicComponents

Enable polymorphic components for data constructors. Synonym for -XRankNTypes.

dynamic

-XNoPolymorphicComponents

-XPostfixOperators

Enable postfix operators.

dynamic

-XNoPostfixOperators

-XQuasiQuotes

Enable quasiquotation.

dynamic

-XNoQuasiQuotes

-XRank2Types

Enable rank-2 types. Synonym for -XRankNTypes.

dynamic

-XNoRank2Types

-XRankNTypes

Enable rank-N types. Implied by -XImpredicativeTypes.

dynamic

-XNoRankNTypes

-XRebindableSyntax

Employ rebindable syntax. Implies -XNoImplicitPrelude.

dynamic

-XNoRebindableSyntax

-XRecordWildCards

Enable record wildcards. Implies -XDisambiguateRecordFields.

dynamic

-XNoRecordWildCards

-XRecursiveDo

Enable recursive do (mdo) notation.

dynamic

-XNoRecursiveDo

-XRoleAnnotations

Enable role annotations.

dynamic

-XNoRoleAnnotations

-XSafe

Enable the Safe Haskell Safe mode.

dynamic

-XScopedTypeVariables

Enable lexically-scoped type variables.

dynamic

-XNoScopedTypeVariables

-XStandaloneDeriving

Enable standalone deriving.

dynamic

-XNoStandaloneDeriving

-XStaticPointers

Enable static pointers.

dynamic

-XNoStaticPointers

-XStrictData

Enable default strict datatype fields.

dynamic

-XNoStrictData

-XTemplateHaskell

Enable Template Haskell.

dynamic

-XNoTemplateHaskell

-XTemplateHaskellQuotes

Enable quotation subset of Template Haskell.

dynamic

-XNoTemplateHaskellQuotes

-XNoTraditionalRecordSyntax

Disable support for traditional record syntax (as supported by Haskell 98) C {f = x}

dynamic

-XTraditionalRecordSyntax

-XTransformListComp

Enable generalised list comprehensions.

dynamic

-XNoTransformListComp

-XTrustworthy

Enable the Safe Haskell Trustworthy mode.

dynamic

-XTupleSections

Enable tuple sections.

dynamic

-XNoTupleSections

-XTypeFamilies

Enable type families. Implies -XExplicitNamespaces, -XKindSignatures, and -XMonoLocalBinds.

dynamic

-XNoTypeFamilies

-XTypeInType

Allow kinds to be used as types, including explicit kind variable quantification, higher-rank kinds, kind synonyms, and kind families. Implies -XDataKinds, -XKindSignatures, and -XPolyKinds.

dynamic

-XNoTypeInType

-XTypeOperators

Enable type operators. Implies -XExplicitNamespaces.

dynamic

-XNoTypeOperators

-XTypeSynonymInstances

Enable type synonyms in instance heads. Implied by -XFlexibleInstances.

dynamic

-XNoTypeSynonymInstances

-XUnboxedTuples

Enable unboxed tuples.

dynamic

-XNoUnboxedTuples

-XUnboxedSums

Enable :ref: unboxed sums <unboxed-sums>.

dynamic

-XNoUnboxedSums

-XUndecidableInstances

Enable undecidable instances.

dynamic

-XNoUndecidableInstances

-XUnicodeSyntax

Enable unicode syntax.

dynamic

-XNoUnicodeSyntax

-XUnliftedFFITypes

Enable unlifted FFI types.

dynamic

-XNoUnliftedFFITypes

-XUnsafe

Enable Safe Haskell Unsafe mode.

dynamic

-XViewPatterns

Enable view patterns.

dynamic

-XNoViewPatterns

7.6.13. Warnings

More details in Warnings and sanity-checking

Flag

Description

Type

Reverse

-W

enable normal warnings

dynamic

-w

-w

disable all warnings

dynamic

-Wall

enable almost all warnings (details in Warnings and sanity-checking)

dynamic

-w

-Wcompat

enable future compatibility warnings (details in Warnings and sanity-checking)

dynamic

-Wno-compat

-Werror

make warnings fatal

dynamic

-Wwarn

-Werror=⟨wflag⟩

make a specific warning fatal

dynamic

-Wwarn=⟨wflag⟩

-Wwarn

make warnings non-fatal

dynamic

-Werror

-Wwarn=⟨wflag⟩

make a specific warning non-fatal

dynamic

-Werror=⟨wflag⟩

-Wunrecognised-warning-flags

throw a warning when an unreconised -W... flag is encountered on the command line.

dynamic

-Wno-unrecognised-warning-flags

-fshow-warning-groups

show which group an emitted warning belongs to.

dynamic

-fno-show-warning-groups

-fdefer-type-errors

Turn type errors into warnings, deferring the error until runtime. Implies -fdefer-typed-holes and -fdefer-out-of-scope-variables. See also -Wdeferred-type-errors

dynamic

-fno-defer-type-errors

-fdefer-typed-holes

Convert typed hole errors into warnings, deferring the error until runtime. Implied by -fdefer-type-errors. See also -Wtyped-holes.

dynamic

-fno-defer-typed-holes

-fdefer-out-of-scope-variables

Convert variable out of scope variables errors into warnings. Implied by -fdefer-type-errors. See also -Wdeferred-out-of-scope-variables.

dynamic

-fno-defer-out-of-scope-variables

-fhelpful-errors

Make suggestions for mis-spelled names.

dynamic

-fno-helpful-errors

-freverse-errors

Display errors in GHC/GHCi sorted by reverse order of source code line numbers.

dynamic

-fno-reverse-errors

-fmax-errors

Limit the number of errors displayed in GHC/GHCi.

dynamic

-fno-max-errors

-Wdeprecated-flags

warn about uses of commandline flags that are deprecated

dynamic

-Wno-deprecated-flags

-Wduplicate-constraints

warn when a constraint appears duplicated in a type signature

dynamic

-Wno-duplicate-constraints

-Wduplicate-exports

warn when an entity is exported multiple times

dynamic

-Wno-duplicate-exports

-Whi-shadowing

warn when a .hi file in the current directory shadows a library

dynamic

-Wno-hi-shadowing

-Widentities

warn about uses of Prelude numeric conversions that are probably the identity (and hence could be omitted)

dynamic

-Wno-identities

-Wimplicit-prelude

warn when the Prelude is implicitly imported

dynamic

-Wno-implicit-prelude

-Wincomplete-patterns

warn when a pattern match could fail

dynamic

-Wno-incomplete-patterns

-Wincomplete-uni-patterns

warn when a pattern match in a lambda expression or pattern binding could fail

dynamic

-Wno-incomplete-uni-patterns

-fmax-pmcheck-iterations=⟨n⟩

the iteration limit for the pattern match checker

dynamic

-Wincomplete-record-updates

warn when a record update could fail

dynamic

-Wno-incomplete-record-updates

-Wmissing-fields

warn when fields of a record are uninitialised

dynamic

-Wno-missing-fields

-Wmissing-import-lists

warn when an import declaration does not explicitly list all thenames brought into scope

dynamic

-fnowarn-missing-import-lists

-Wmissing-methods

warn when class methods are undefined

dynamic

-Wno-missing-methods

-Wmissing-signatures

warn about top-level functions without signatures

dynamic

-Wno-missing-signatures

-Wmissing-exported-sigs

(deprecated) warn about top-level functions without signatures, only if they are exported. takes precedence over -Wmissing-signatures

dynamic

-Wno-missing-exported-sigs

-Wmissing-exported-signatures

warn about top-level functions without signatures, only if they are exported. takes precedence over -Wmissing-signatures

dynamic

-Wno-missing-exported-signatures

-Wmissing-local-sigs

(deprecated) warn about polymorphic local bindings without signatures

dynamic

-Wno-missing-local-sigs

-Wmissing-local-signatures

warn about polymorphic local bindings without signatures

dynamic

-Wno-missing-local-signatures

-Wmissing-monadfail-instances

warn when a failable pattern is used in a do-block that does not have a MonadFail instance.

dynamic

-Wno-missing-monadfail-instances

-Wsemigroup

warn when a Monoid is not Semigroup, and on non-Semigroup definitions of (<>)?

dynamic

-Wno-semigroup

-Wmissed-specialisations

warn when specialisation of an imported, overloaded function fails.

dynamic

-Wno-missed-specialisations

-Wall-missed-specialisations

warn when specialisation of any overloaded function fails.

dynamic

-Wno-all-missed-specialisations

-Wmonomorphism-restriction

warn when the Monomorphism Restriction is applied

dynamic

-Wno-monomorphism-restriction

-Wname-shadowing

warn when names are shadowed

dynamic

-Wno-name-shadowing

-Wnoncanonical-monad-instances

warn when Applicative or Monad instances have noncanonical definitions of return, pure, (>>), or (*>). See flag description in Warnings and sanity-checking for more details.

dynamic

-Wno-noncanonical-monad-instances

-Wnoncanonical-monadfail-instances

warn when Monad or MonadFail instances have noncanonical definitions of fail.See flag description in Warnings and sanity-checking for more details.

dynamic

-Wno-noncanonical-monadfail-instances

-Wnoncanonical-monoid-instances

warn when Semigroup or Monoid instances have noncanonical definitions of (<>) or mappend. See flag description in Warnings and sanity-checking for more details.

dynamic

-Wno-noncanonical-monoid-instances

-Worphans

warn when the module contains orphan instance declarations or rewrite rules

dynamic

-Wno-orphans

-Woverlapping-patterns

warn about overlapping patterns

dynamic

-Wno-overlapping-patterns

-Wtabs

warn if there are tabs in the source file

dynamic

-Wno-tabs

-Wtype-defaults

warn when defaulting happens

dynamic

-Wno-type-defaults

-Wunrecognised-pragmas

warn about uses of pragmas that GHC doesn’t recognise

dynamic

-Wno-unrecognised-pragmas

-Wunticked-promoted-constructors

warn if promoted constructors are not ticked

dynamic

-Wno-unticked-promoted-constructors

-Wunused-binds

warn about bindings that are unused. Alias for -Wunused-top-binds, -Wunused-local-binds and -Wunused-pattern-binds

dynamic

-Wno-unused-binds

-Wunused-top-binds

warn about top-level bindings that are unused

dynamic

-Wno-unused-top-binds

-Wunused-local-binds

warn about local bindings that are unused

dynamic

-Wno-unused-local-binds

-Wunused-pattern-binds

warn about pattern match bindings that are unused

dynamic

-Wno-unused-pattern-binds

-Wunused-imports

warn about unnecessary imports

dynamic

-Wno-unused-imports

-Wunused-matches

warn about variables in patterns that aren’t used

dynamic

-Wno-unused-matches

-Wunused-foralls

warn about type variables in user-written foralls that are unused

dynamic

-Wno-unused-foralls

-Wunused-type-variables

warn about variables in type family or data family instances that are unused

dynamic

-Wno-unused-type-variables

-Wunused-do-bind

warn about do bindings that appear to throw away values of types other than ()

dynamic

-Wno-unused-do-bind

-Wwrong-do-bind

warn about do bindings that appear to throw away monadic values that you should have bound instead

dynamic

-Wno-wrong-do-bind

-Wunsafe

warn if the module being compiled is regarded to be unsafe. Should be used to check the safety status of modules when using safe inference. Works on all module types, even those using explicit Safe Haskell modes (such as -XTrustworthy) and so can be used to have the compiler check any assumptions made.

dynamic

-Wno-unsafe

-Wsafe

warn if the module being compiled is regarded to be safe. Should be used to check the safety status of modules when using safe inference. Works on all module types, even those using explicit Safe Haskell modes (such as -XTrustworthy) and so can be used to have the compiler check any assumptions made.

dynamic

-Wno-safe

-Wtrustworthy-safe

warn if the module being compiled is marked as -XTrustworthy but it could instead be marked as -XSafe, a more informative bound. Can be used to detectonce a Safe Haskell bound can be improved as dependencies are updated.

dynamic

-Wno-safe

-Wwarnings-deprecations

warn about uses of functions & types that have warnings or deprecated pragmas

dynamic

-Wno-warnings-deprecations

-Wdeprecations

warn about uses of functions & types that have warnings or deprecated pragmas. Alias for -Wwarnings-deprecations

dynamic

-Wno-deprecations

-Wamp

(deprecated) warn on definitions conflicting with the Applicative-Monad Proposal (AMP)

dynamic

-Wno-amp

-Wredundant-constraints

Have the compiler warn about redundant constraints in typesignatures.

dynamic

-Wno-redundant-constraints

-Wdeferred-type-errors

Report warnings when deferred type errors are enabled. This option is enabled by default. See -fdefer-type-errors.

dynamic

-Wno-deferred-type-errors

-Wtyped-holes

Report warnings when typed hole errors are deferred until runtime. See -fdefer-typed-holes.

dynamic

-Wno-typed-holes

-Wdeferred-out-of-scope-variables

Report warnings when variable out-of-scope errors are deferred until runtime. See :ghc-flag:-fdefer-out-of-scope-variables`.

dynamic

-Wno-deferred-out-of-scope-variables

-Wpartial-type-signatures

warn about holes in partial type signatures when -XPartialTypeSignatures is enabled. Not applicable when -XPartialTypesignatures is not enabled, in which case errors are generated for such holes. See Partial Type Signatures.

dynamic

-Wno-partial-type-signatures

-Wderiving-typeable

warn when encountering a request to derive an instance of class Typeable. As of GHC 7.10, such declarations are unnecessary and are ignored by the compiler because GHC has a custom solver for discharging this type of constraint.

dynamic

-Wno-deriving-typeable

-Wmissing-home-modules

warn when encountering a home module imported, but not listed on the command line. Useful for cabal to ensure GHC won’t pick up modules, not listed neither in exposed-modules, nor in other-modules.

dynamic

-Wno-missing-home-modules

7.6.14. Optimisation levels

These options are described in more detail in Optimisation (code improvement).

See Individual optimisations for a list of optimisations enabled on level 1 and level 2.

Flag

Description

Type

Reverse

-O0

Disable optimisations (default)

dynamic

-O

-O, -O1

Enable level 1 optimisations

dynamic

-O0

-O2

Enable level 2 optimisations

dynamic

-O0

-Odph

Enable level 2 optimisations, set -fmax-simplifier-iterations=20 and -fsimplifier-phases=3.

dynamic

7.6.15. Individual optimisations

These options are described in more detail in -f*: platform-independent flags. If a flag is implied by -O then it is also implied by -O2 (unless flag description explicitly says otherwise). If a flag is implied by -O0 only then the flag is not implied by -O and -O2.

Flag

Description

Type

Reverse

-fcall-arity

Enable call-arity optimisation. Implied by -O.

dynamic

-fno-call-arity

-fcase-merge

Enable case-merging. Implied by -O.

dynamic

-fno-case-merge

-fcase-folding

Enable constant folding in case expressions. Implied by -O.

dynamic

-fno-case-folding

-fcmm-elim-common-blocks

Enable Cmm common block elimination. Implied by -O.

dynamic

-fno-cmm-elim-common-blocks

-fcmm-sink

Enable Cmm sinking. Implied by -O.

dynamic

-fno-cmm-sink

-fcpr-anal

Turn on CPR analysis in the demand analyser. Implied by -O.

dynamic

-fno-cpr-anal

-fcse

Enable common sub-expression elimination. Implied by -O.

dynamic

-fno-cse

-fdicts-cheap

Make dictionary-valued expressions seem cheap to the optimiser.

dynamic

-fno-dicts-cheap

-fdicts-strict

Make dictionaries strict

dynamic

-fno-dicts-strict

-fdmd-tx-dict-sel

Use a special demand transformer for dictionary selectors. Always enabled by default.

dynamic

-fno-dmd-tx-dict-sel

-fdo-eta-reduction

Enable eta-reduction. Implied by -O.

dynamic

-fno-do-eta-reduction

-fdo-lambda-eta-expansion

Enable lambda eta-expansion. Always enabled by default.

dynamic

-fno-do-lambda-eta-expansion

-feager-blackholing

Turn on eager blackholing

dynamic

-fenable-rewrite-rules

Switch on all rewrite rules (including rules generated by automatic specialisation of overloaded functions). Implied by -O.

dynamic

-fno-enable-rewrite-rules

-fexcess-precision

Enable excess intermediate precision

dynamic

-fno-excess-precision

-fexpose-all-unfoldings

Expose all unfoldings, even for very large or recursive functions.

dynamic

-fno-expose-all-unfoldings

-ffloat-in

Turn on the float-in transformation. Implied by -O.

dynamic

-fno-float-in

-ffull-laziness

Turn on full laziness (floating bindings outwards). Implied by -O.

dynamic

-fno-full-laziness

-ffun-to-thunk

Allow worker-wrapper to convert a function closure into a thunk if the function does not use any of its arguments. Off by default.

dynamic

-fno-fun-to-thunk

-fignore-asserts

Ignore assertions in the source. Implied by -O.

dynamic

-fno-ignore-asserts

-fignore-interface-pragmas

Ignore pragmas in interface files. Implied by -O0 only.

dynamic

-fno-ignore-interface-pragmas

-flate-dmd-anal

Run demand analysis again, at the end of the simplification pipeline

dynamic

-fno-late-dmd-anal

-fliberate-case

Turn on the liberate-case transformation. Implied by -O2.

dynamic

-fno-liberate-case

-fliberate-case-threshold=⟨n⟩

default: 2000. Set the size threshold for the liberate-case transformation to ⟨n⟩

dynamic

-fno-liberate-case-threshold

-floopification

Turn saturated self-recursive tail-calls into local jumps in the generated assembly. Implied by -O.

dynamic

-fno-loopification

-fmax-inline-alloc-size=⟨n⟩

default: 128. Set the maximum size of inline array allocations to ⟨n⟩ bytes (default: 128). GHC will allocate non-pinned arrays of statically known size in the current nursery block if they’re no bigger than ⟨n⟩ bytes, ignoring GC overheap. This value should be quite a bit smaller than the block size (typically: 4096).

dynamic

-fmax-inline-memcpy-insns=⟨n⟩

default: 32. Inline memcpy calls if they would generate no more than ⟨n⟩ pseudo instructions.

dynamic

-fmax-inline-memset-insns=⟨n⟩

default: 32. Inline memset calls if they would generate no more than ⟨n⟩ pseudo instructions

dynamic

-fmax-relevant-binds=⟨n⟩

default: 6. Set the maximum number of bindings to display in type error messages.

dynamic

-fno-max-relevant-bindings

-fmax-uncovered-patterns=⟨n⟩

default: 4. Set the maximum number of patterns to display in warnings about non-exhaustive ones.

dynamic

-fmax-simplifier-iterations=⟨n⟩

default: 4. Set the max iterations for the simplifier.

dynamic

-fmax-worker-args=⟨n⟩

default: 10. If a worker has that many arguments, none will be unpacked anymore.

dynamic

-fno-opt-coercion

Turn off the coercion optimiser

dynamic

-fno-pre-inlining

Turn off pre-inlining

dynamic

-fno-state-hack

Turn off the “state hack” whereby any lambda with a real-world state token as argument is considered to be single-entry. Hence OK to inline things inside it.

dynamic

-fomit-interface-pragmas

Don’t generate interface pragmas. Implied by -O0 only.

dynamic

-fno-omit-interface-pragmas

-fomit-yields

Omit heap checks when no allocation is being performed.

dynamic

-fno-omit-yields

-foptimal-applicative-do

Use a slower but better algorithm for ApplicativeDo

dynamic

-fno-optimal-applicative-do

-fpedantic-bottoms

Make GHC be more precise about its treatment of bottom (but see also -fno-state-hack). In particular, GHC will not eta-expand through a case expression.

dynamic

-fno-pedantic-bottoms

-fregs-graph

Use the graph colouring register allocator for register allocation in the native code generator. Implied by -O2.

dynamic

-fno-regs-graph

-fregs-iterative

Use the iterative coalescing graph colouring register allocator in the native code generator.

dynamic

-fno-regs-iterative

-fsimplifier-phases=⟨n⟩

default: 2. Set the number of phases for the simplifier. Ignored with -O0.

dynamic

-fsimpl-tick-factor=⟨n⟩

default: 100. Set the percentage factor for simplifier ticks.

dynamic

-fspec-constr

Turn on the SpecConstr transformation. Implied by -O2.

dynamic

-fno-spec-constr

-fspec-constr-count=⟨n⟩

default: 3.* Set to ⟨n⟩ the maximum number of specialisations that will be created for any one function by the SpecConstr transformation.

dynamic

-fno-spec-constr-count

-fspec-constr-threshold=⟨n⟩

default: 2000. Set the size threshold for the SpecConstr transformation to ⟨n⟩.

dynamic

-fno-spec-constr-threshold

-fspecialise

Turn on specialisation of overloaded functions. Implied by -O.

dynamic

-fno-specialise

-fcross-module-specialise

Turn on specialisation of overloaded functions imported from other modules.

dynamic

-fno-cross-module-specialise

-fstatic-argument-transformation

Turn on the static argument transformation.

dynamic

-fno-static-argument-transformation

-fstrictness

Turn on strictness analysis. Implied by -O. Implies -fworker-wrapper

dynamic

-fno-strictness

-fstrictness-before=⟨n⟩

Run an additional strictness analysis before simplifier phase ⟨n⟩

dynamic

-funbox-small-strict-fields

Flatten strict constructor fields with a pointer-sized representation. Implied by -O.

dynamic

-fno-unbox-small-strict-fields

-funbox-strict-fields

Flatten strict constructor fields

dynamic

-fno-unbox-strict-fields

-funfolding-creation-threshold=⟨n⟩

default: 750. Tweak unfolding settings.

dynamic

-funfolding-dict-discount=⟨n⟩

default: 30. Tweak unfolding settings.

dynamic

-funfolding-fun-discount=⟨n⟩

default: 60. Tweak unfolding settings.

dynamic

-funfolding-keeness-factor=⟨n⟩

default: 1.5. Tweak unfolding settings.

dynamic

-funfolding-use-threshold=⟨n⟩

default: 60. Tweak unfolding settings.

dynamic

-fvectorisation-avoidance

Enable vectorisation avoidance. Always enabled by default.

dynamic

-fno-vectorisation-avoidance

-fvectorise

Enable vectorisation of nested data parallelism

dynamic

-fno-vectorise

-fworker-wrapper

Enable the worker-wrapper transformation after a strictness analysis pass. Implied by -O, and by -fstrictness. Disabled by -fno-strictness. Enabling -fworker-wrapper while strictness analysis is disabled (by -fno-strictness) has no effect.

dynamic

-fno-worker-wrapper

7.6.16. Profiling options

More details in Profiling

Flag

Description

Type

Reverse

-prof

Turn on profiling

dynamic

-fprof-auto

Auto-add SCCs to all bindings not marked INLINE

dynamic

-fno-prof-auto

-fprof-auto-top

Auto-add SCCs to all top-level bindings not marked INLINE

dynamic

-fno-prof-auto

-fprof-auto-exported

Auto-add SCCs to all exported bindings not marked INLINE

dynamic

-fno-prof-auto

-fprof-cafs

Auto-add SCCs to all CAFs

dynamic

-fno-prof-cafs

-fno-prof-count-entries

Do not collect entry counts

dynamic

-fprof-count-entries

-ticky

Turn on ticky-ticky profiling

dynamic

7.6.17. Program coverage options

More details in Observing Code Coverage

Flag

Description

Type

Reverse

-fhpc

Turn on Haskell program coverage instrumentation

dynamic

-hpcdir ⟨dir⟩

Directory to deposit .mix files during compilation (default is .hpc)

dynamic

7.6.18. C pre-processor options

More details in Options affecting the C pre-processor

Flag

Description

Type

Reverse

-cpp

Run the C pre-processor on Haskell source files

dynamic

-D⟨symbol⟩[=⟨value⟩]

Define a symbol in the C pre-processor

dynamic

-U⟨symbol⟩

-U⟨symbol⟩

Undefine a symbol in the C pre-processor

dynamic

-I⟨dir⟩

Add ⟨dir⟩ to the directory search list for #include files

dynamic

7.6.19. Code generation options

More details in Options affecting code generation

Flag

Description

Type

Reverse

-fasm

Use the native code generator

dynamic

-fllvm

-fllvm

Compile using the LLVM code generator

dynamic

-fasm

-fno-code

Omit code generation

dynamic

-fwrite-interface

Always write interface files

dynamic

-fbyte-code

Generate byte-code

dynamic

-fobject-code

Generate object code

dynamic

-g⟨n⟩

Produce DWARF debug information in compiled object files.⟨n⟩ can be 0, 1, or 2, with higher numbers producing richer output. If ⟨n⟩ is omitted level 2 is assumed.

dynamic

-dynamic

Build dynamically-linked object files and executables

dynamic

-dynamic-too

Build dynamic object files as well as static object files during compilation

dynamic

7.6.20. Linking options

More details in Options affecting linking

Flag

Description

Type

Reverse

-shared

Generate a shared library (as opposed to an executable)

dynamic

-staticlib

On Darwin/OS X/iOS only, generate a standalone static library (as opposed to an executable). This is the usual way to compile for iOS.

dynamic

-fPIC

Generate position-independent code (where available)

dynamic

-fPIE

Generate code for a position-independent executable (where available)

dynamic

-pie

Instruct the linker to produce a position-independent executable.

dynamic

-dynload

Selects one of a number of modes for finding shared libraries at runtime.

dynamic

-framework ⟨name⟩

On Darwin/OS X/iOS only, link in the framework ⟨name⟩. This option corresponds to the -framework option for Apple’s Linker.

dynamic

-framework-path ⟨dir⟩

On Darwin/OS X/iOS only, add ⟨dir⟩ to the list of directories searched for frameworks. This option corresponds to the -F option for Apple’s Linker.

dynamic

-l ⟨lib⟩

Link in library ⟨lib⟩

dynamic

-L ⟨dir⟩

Add ⟨dir⟩ to the list of directories searched for libraries

dynamic

-main-is ⟨thing⟩

Set main module and function

dynamic

--mk-dll

DLL-creation mode (Windows only)

dynamic

-no-hs-main

Don’t assume this program contains main

dynamic

-rtsopts[=⟨none|some|all⟩]

Control whether the RTS behaviour can be tweaked via command-lineflags and the GHCRTS environment variable. Using none means no RTS flags can be given; some means only a minimum of safe options can be given (the default), and all (or no argument at all) means that all RTS flags are permitted.

dynamic

-with-rtsopts=⟨opts⟩

Set the default RTS options to ⟨opts⟩.

dynamic

-no-rtsopts-suggestions

Don’t print RTS suggestions about linking with -rtsopts[=⟨none|some|all⟩].

dynamic

-no-link

Omit linking

dynamic

-split-objs

Split objects (for libraries)

dynamic

-split-sections

Split sections for link-time dead-code stripping

dynamic

-static

Use static Haskell libraries

dynamic

-threaded

Use the threaded runtime

dynamic

-debug

Use the debugging runtime

dynamic

-ticky

For linking, this simply implies -debug; see Using “ticky-ticky” profiling (for implementors).

dynamic

-eventlog

Enable runtime event tracing

dynamic

-fno-gen-manifest

Do not generate a manifest file (Windows only)

dynamic

-fno-embed-manifest

Do not embed the manifest in the executable (Windows only)

dynamic

-fno-shared-implib

Don’t generate an import library for a DLL (Windows only)

dynamic

-dylib-install-name ⟨path⟩

Set the install name (via -install_name passed to Apple’s linker), specifying the full install path of the library file. Any libraries or executables that link with it later will pick up that path as their runtime search location for it. (Darwin/OS X only)

dynamic

-rdynamic

This instructs the linker to add all symbols, not only used ones, to the dynamic symbol table. Currently Linux and Windows/MinGW32 only. This is equivalent to using -optl -rdynamic on Linux, and -optl -export-all-symbols on Windows.

dynamic

7.6.21. Plugin options

More details in Compiler Plugins

Flag

Description

Type

Reverse

-fplugin=⟨module⟩

Load a plugin exported by a given module

dynamic

-fplugin-opt=⟨module⟩:⟨args⟩

Give arguments to a plugin module; module must be specified with -fplugin

dynamic

7.6.22. Replacing phases

More details in Replacing the program for one or more phases

Flag

Description

Type

Reverse

-pgmL ⟨cmd⟩

Use ⟨cmd⟩ as the literate pre-processor

dynamic

-pgmP ⟨cmd⟩

Use ⟨cmd⟩ as the C pre-processor (with -cpp only)

dynamic

-pgmc ⟨cmd⟩

Use ⟨cmd⟩ as the C compiler

dynamic

-pgmlo ⟨cmd⟩

Use ⟨cmd⟩ as the LLVM optimiser

dynamic

-pgmlc ⟨cmd⟩

Use ⟨cmd⟩ as the LLVM compiler

dynamic

-pgms ⟨cmd⟩

Use ⟨cmd⟩ as the splitter

dynamic

-pgma ⟨cmd⟩

Use ⟨cmd⟩ as the assembler

dynamic

-pgml ⟨cmd⟩

Use ⟨cmd⟩ as the linker

dynamic

-pgmdll ⟨cmd⟩

Use ⟨cmd⟩ as the DLL generator

dynamic

-pgmF ⟨cmd⟩

Use ⟨cmd⟩ as the pre-processor (with -F only)

dynamic

-pgmwindres ⟨cmd⟩

Use ⟨cmd⟩ as the program for embedding manifests on Windows.

dynamic

-pgmlibtool ⟨cmd⟩

Use ⟨cmd⟩ as the command for libtool (with -staticlib only).

dynamic

7.6.23. Forcing options to particular phases

More details in Forcing options to a particular phase

Flag

Description

Type

Reverse

-optL ⟨option⟩

pass ⟨option⟩ to the literate pre-processor

dynamic

-optP ⟨option⟩

pass ⟨option⟩ to cpp (with -cpp only)

dynamic

-optF ⟨option⟩

pass ⟨option⟩ to the custom pre-processor

dynamic

-optc ⟨option⟩

pass ⟨option⟩ to the C compiler

dynamic

-optlo ⟨option⟩

pass ⟨option⟩ to the LLVM optimiser

dynamic

-optlc ⟨option⟩

pass ⟨option⟩ to the LLVM compiler

dynamic

-opta ⟨option⟩

pass ⟨option⟩ to the assembler

dynamic

-optl ⟨option⟩

pass ⟨option⟩ to the linker

dynamic

-optdll ⟨option⟩

pass ⟨option⟩ to the DLL generator

dynamic

-optwindres ⟨option⟩

pass ⟨option⟩ to windres.

dynamic

7.6.24. Platform-specific options

More details in Platform-specific Flags

Flag

Description

Type

Reverse

-msse2

(x86 only) Use SSE2 for floating-point operations

dynamic

-msse4.2

(x86 only) Use SSE4.2 for floating-point operations

dynamic

7.6.25. Compiler debugging options

More details in Debugging the compiler

Flag

Description

Type

Reverse

-dcore-lint

Turn on internal sanity checking

dynamic

-ddump-to-file

Dump to files instead of stdout

dynamic

-ddump-asm

Dump assembly

dynamic

-ddump-bcos

Dump interpreter byte code

dynamic

-ddump-cmm-from-stg

Dump STG-to-C– output

dynamic

-ddump-cmm-verbose

Show output from each C– pipeline pass

dynamic

-ddump-cmm

Dump the final C– output

dynamic

-ddump-core-stats

Print a one-line summary of the size of the Core program at the end of the optimisation pipeline

dynamic

-ddump-cse

Dump CSE output

dynamic

-ddump-deriv

Dump deriving output

dynamic

-ddump-ds

Dump desugarer output

dynamic

-ddump-foreign

Dump foreign export stubs

dynamic

-ddump-hpc

Dump after instrumentation for program coverage

dynamic

-ddump-inlinings

Dump inlining info

dynamic

-ddump-llvm

Dump LLVM intermediate code. Implies -fllvm.

dynamic

-ddump-occur-anal

Dump occurrence analysis output

dynamic

-ddump-opt-cmm

Dump the results of C– to C– optimising passes

dynamic

-ddump-parsed

Dump parse tree

dynamic

-ddump-prep

Dump prepared core

dynamic

-ddump-rn

Dump renamer output

dynamic

-ddump-rule-firings

Dump rule firing info

dynamic

-ddump-rule-rewrites

Dump detailed rule firing info

dynamic

-ddump-rules

Dump rules

dynamic

-ddump-vect

Dump vectoriser input and output

dynamic

-ddump-simpl

Dump final simplifier output

dynamic

-ddump-simpl-iterations

Dump output from each simplifier iteration

dynamic

-ddump-spec

Dump specialiser output

dynamic

-ddump-splices

Dump TH spliced expressions, and what they evaluate to

dynamic

-ddump-stg

Dump final STG

dynamic

-ddump-stranal

Dump strictness analyser output

dynamic

-ddump-str-signatures

Dump strictness signatures

dynamic

-ddump-tc

Dump typechecker output

dynamic

-dth-dec-file=⟨file⟩

Show evaluated TH declarations in a .th.hs file

dynamic

-ddump-types

Dump type signatures

dynamic

-ddump-worker-wrapper

Dump worker-wrapper output

dynamic

-ddump-if-trace

Trace interface files

dynamic

-ddump-tc-trace

Trace typechecker

dynamic

-ddump-vt-trace

Trace vectoriser

dynamic

-ddump-rn-trace

Trace renamer

dynamic

-ddump-rn-stats

Renamer stats

dynamic

-ddump-simpl-stats

Dump simplifier stats

dynamic

-dno-debug-output

Suppress unsolicited debugging output

dynamic

-dppr-debug

Turn on debug printing (more verbose)

dynamic

-dppr-user-length

Set the depth for printing expressions in error msgs

dynamic

-dppr-cols=⟨n⟩

Set the width of debugging output. For example -dppr-cols200

dynamic

-dppr-case-as-let

Print single alternative case expressions as strict lets.

dynamic

-dsuppress-all

In core dumps, suppress everything (except for uniques) that is suppressible.

dynamic

-dsuppress-uniques

Suppress the printing of uniques in debug output (easier to use diff)

dynamic

-dsuppress-idinfo

Suppress extended information about identifiers where they are bound

dynamic

-dsuppress-unfoldings

Suppress the printing of the stable unfolding of a variable at its binding site

dynamic

-dsuppress-module-prefixes

Suppress the printing of module qualification prefixes

dynamic

-dsuppress-type-signatures

Suppress type signatures

dynamic

-dsuppress-type-applications

Suppress type applications

dynamic

-dsuppress-coercions

Suppress the printing of coercions in Core dumps to make them shorter

dynamic

-dsource-stats

Dump haskell source stats

dynamic

-dcmm-lint

C– pass sanity checking

dynamic

-dstg-lint

STG pass sanity checking

dynamic

-dstg-stats

Dump STG stats

dynamic

-dverbose-core2core

Show output from each core-to-core pass

dynamic

-dverbose-stg2stg

Show output from each STG-to-STG pass

dynamic

-dshow-passes

Print out each pass name as it happens

dynamic

-dfaststring-stats

Show statistics for fast string usage when finished

dynamic

-frule-check

Report sites with rules that could have fired but didn’t. Takes a string argument.

dynamic

7.6.26. Miscellaneous compiler options

Flag

Description

Type

Reverse

-j[⟨n⟩]

When compiling with --make, compile ⟨n⟩ modules in parallel.

dynamic

-fno-hi-version-check

Don’t complain about .hi file mismatches

dynamic

-fhistory-size

Set simplification history size

dynamic

-fno-ghci-history

Do not use the load/store the GHCi command history from/to ghci_history.

dynamic

-fno-ghci-sandbox

Turn off the GHCi sandbox. Means computations are run in the main thread, rather than a forked thread.

dynamic

-flocal-ghci-history

Use current directory for the GHCi command history file .ghci-history.

dynamic

-fno-local-ghci-history