5.6. Flag reference

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

5.6.1. Verbosity options

More details in Verbosity options

Flag Description Type Reverse

-fabstract-refinement-hole-fits

default: off. Toggles whether refinements where one or more of the holes are abstract are reported.

dynamic

-fno-abstract-refinement-hole-fits

-fdefer-diagnostics

Defer and group diagnostic messages by severity

dynamic

-fdiagnostics-color=⟨always|auto|never⟩

Use colors in error messages

dynamic

-fdiagnostics-show-caret

Whether to show snippets of original source code

dynamic

-fno-diagnostics-show-caret

-ferror-spans

Output full span in error messages

dynamic

-fhide-source-paths

hide module source and object paths

dynamic

-fkeep-going

Continue compilation as far as possible on errors

dynamic

-fmax-refinement-hole-fits=⟨n⟩

default: 6. Set the maximum number of refinement hole fits for typed holes to display in type error messages.

dynamic

-fno-max-refinement-hole-fits

-fmax-relevant-binds=⟨n⟩

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

dynamic

-fno-max-relevant-binds

-fmax-valid-hole-fits=⟨n⟩

default: 6. Set the maximum number of valid hole fits for typed holes to display in type error messages.

dynamic

-fno-max-valid-hole-fits

-fno-show-valid-hole-fits

Disables showing a list of valid hole fits for typed holes in type error messages.

dynamic

-fno-sort-valid-hole-fits

Disables the sorting of the list of valid hole fits for typed holes in type error messages.

dynamic

-fsort-valid-hole-fits

-fprint-axiom-incomps

Display equation incompatibilities in closed type families

dynamic

-fno-print-axiom-incomps

-fprint-equality-relations

Distinguish between equality relations when printing

dynamic

-fno-print-equality-relations

-fprint-expanded-synonyms

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

dynamic

-fno-print-expanded-synonyms

-fprint-explicit-coercions

Print coercions in types

dynamic

-fno-print-explicit-coercions

-fprint-explicit-foralls

Print explicit forall quantification in types. See also ExplicitForAll

dynamic

-fno-print-explicit-foralls

-fprint-explicit-kinds

Print explicit kind foralls and kind arguments in types. See also KindSignatures

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-potential-instances

display all available instances in type error messages

dynamic

-fno-print-potential-instances

-fprint-typechecker-elaboration

Print extra information from typechecker.

dynamic

-fno-print-typechecker-elaboration

-fprint-unicode-syntax

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

dynamic

-fno-print-unicode-syntax

-frefinement-level-hole-fits=⟨n⟩

default: off. Sets the level of refinement of the refinement hole fits, where level n means that hole fits of up to n holes will be considered.

dynamic

-fno-refinement-level-hole-fits

-freverse-errors

Output errors in reverse order

dynamic

-fno-reverse-errors

-fshow-docs-of-hole-fits

Toggles whether to show the documentation of the valid hole fits in the output.

dynamic

-fno-show-docs-of-hole-fits

-fshow-hole-constraints

Show constraints when reporting typed holes.

dynamic

-fshow-hole-matches-of-hole-fits

Toggles whether to show the type of the additional holes in refinement hole fits.

dynamic

-fno-show-hole-matches-of-hole-fits

-fshow-provenance-of-hole-fits

Toggles whether to show the provenance of the valid hole fits in the output.

dynamic

-fno-show-provenance-of-hole-fits

-fshow-type-app-of-hole-fits

Toggles whether to show the type application of the valid hole fits in the output.

dynamic

-fno-show-type-app-of-hole-fits

-fshow-type-app-vars-of-hole-fits

Toggles whether to show what type each quantified variable takes in a valid hole fit.

dynamic

-fno-show-type-app-vars-of-hole-fits

-fshow-type-of-hole-fits

Toggles whether to show the type of the valid hole fits in the output.

dynamic

-fno-type-of-hole-fits

-funclutter-valid-hole-fits

Unclutter the list of valid hole fits by not showing provenance nor type applications of suggestions.

dynamic

-Rghc-timing

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

dynamic

-v

verbose mode (equivalent to -v3)

dynamic

-v⟨n⟩

set verbosity level

dynamic

5.6.2. Alternative modes of operation

More details in Modes of operation

Flag Description Type Reverse

--frontend ⟨module⟩

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

mode

--help, -?

Display help

mode

--info

display information about the compiler

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

--mk-dll

DLL-creation mode (Windows only)

mode

--numeric-version

display GHC version (numeric only)

mode

--print-libdir

display GHC library directory

mode

--show-iface ⟨file⟩

display the contents of an interface file.

mode

--show-options

display the supported command line options

mode

--supported-extensions, --supported-languages

display the supported language extensions

mode

--version, -V

display GHC version

mode

-e ⟨expr⟩

Evaluate expr; see Expression evaluation mode for details.

mode

-M

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

mode

5.6.3. Which phases to run

More details in Batch compiler mode

Flag Description Type Reverse

-C

Stop after generating C (.hc file)

mode

-c

Stop after generating object (.o) file

mode

-E

Stop after preprocessing (.hspp file)

mode

-F

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

dynamic

-S

Stop after generating assembly (.s file)

mode

-x ⟨suffix⟩

Override default behaviour for source files

dynamic

5.6.4. Redirecting output

More details in Redirecting the compilation output(s)

Flag Description Type Reverse

--exclude-module=⟨file⟩

Regard ⟨file⟩ as "stable"; i.e., exclude it from having dependencies on it.

dynamic

-ddump-mod-cycles

Dump module cycles

dynamic

-dep-makefile ⟨file⟩

Use ⟨file⟩ as the makefile

dynamic

-dep-suffix ⟨suffix⟩

Make dependencies that declare that files with suffix .⟨suf⟩⟨osuf⟩ depend on interface files with suffix .⟨suf⟩hi

dynamic

-dumpdir ⟨dir⟩

redirect dump files

dynamic

-hcsuf ⟨suffix⟩

set the suffix to use for intermediate C files

dynamic

-hidir ⟨dir⟩

set directory for interface files

dynamic

-hiedir ⟨dir⟩

set directory for extended interface files

dynamic

-hiesuf ⟨suffix⟩

set the suffix to use for extended interface files

dynamic

-hisuf ⟨suffix⟩

set the suffix to use for interface files

dynamic

-include-cpp-deps

Include preprocessor dependencies

dynamic

-include-pkg-deps

Regard modules imported from packages as unstable

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

-outputdir ⟨dir⟩

set output directory

dynamic

-stubdir ⟨dir⟩

redirect FFI stub files

dynamic

5.6.5. 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-hscpp-file, -keep-hscpp-files

Retain intermediate .hscpp files.

dynamic

-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

5.6.6. Temporary files

More details in Redirecting temporary files

Flag Description Type Reverse

-tmpdir ⟨dir⟩

set the directory for temporary files

dynamic

5.6.7. Finding imports

More details in The search path

Flag Description Type Reverse

-i

Empty the import directory list

dynamic

-i⟨dir⟩[:⟨dir⟩]*

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

dynamic

5.6.8. Interface file options

More details in Other options related to interface files

Flag Description Type Reverse

--show-iface ⟨file⟩

See Modes of operation.

mode

-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

5.6.9. 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

-fignore-hpc-changes

Do not recompile modules just to match changes to HPC flags. This is especially useful for avoiding recompilation when using GHCi, and is enabled by default for GHCi.

dynamic

-fno-ignore-hpc-changes

-fignore-optim-changes

Do not recompile modules just to match changes to optimisation flags. This is especially useful for avoiding recompilation when using GHCi, and is enabled by default for GHCi.

dynamic

-fno-ignore-optim-changes

5.6.10. Interactive-mode options

More details in The .ghci and .haskeline files

Flag Description Type Reverse

-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

-fghci-leak-check

(Debugging only) check for space leaks when loading new modules in GHCi.

dynamic

-fno-ghci-leak-check

-flocal-ghci-history

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

dynamic

-fno-local-ghci-history

-fno-it

No longer set the special variable it.

dynamic

-fno-no-it

-fprint-bind-result

Turn on printing of binding results in GHCi

dynamic

-fno-print-bind-result

-fprint-evld-with-show

Instruct :print to use Show instances where possible.

dynamic

-fshow-loaded-modules

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

dynamic

-ghci-script

Read additional .ghci files

dynamic

-ignore-dot-ghci

Disable reading of .ghci files

dynamic

-interactive-print ⟨name⟩

Select the function to use for printing evaluated expressions in GHCi

dynamic

5.6.11. Packages

More details in Packages

Flag Description Type Reverse

-clear-package-db

Clear the package db stack.

dynamic

-distrust ⟨pkg⟩

Expose package ⟨pkg⟩ and set it to be distrusted. See Safe Haskell.

dynamic

-distrust-all-packages

Distrust all packages by default. See Safe Haskell.

dynamic

-fpackage-trust

Enable Safe Haskell trusted package requirement for trustworthy modules.

dynamic

-global-package-db

Add the global package db to the stack.

dynamic

-hide-all-packages

Hide all packages by default

dynamic

-hide-package ⟨pkg⟩

Hide package ⟨pkg⟩

dynamic

-ignore-package ⟨pkg⟩

Ignore package ⟨pkg⟩

dynamic

-no-auto-link-packages

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

dynamic

-no-global-package-db

Remove the global package db from the stack.

dynamic

-no-user-package-db

Remove the user's package db from the stack.

dynamic

-package ⟨pkg⟩

Expose package ⟨pkg⟩

dynamic

-package-db ⟨file⟩

Add ⟨file⟩ to the package db stack.

dynamic

-package-env ⟨file⟩|⟨name⟩

Use the specified package environment.

dynamic

-package-id ⟨unit-id⟩

Expose package by id ⟨unit-id⟩

dynamic

-this-unit-id ⟨unit-id⟩

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

dynamic

-trust ⟨pkg⟩

Expose package ⟨pkg⟩ and set it to be trusted. See Safe Haskell.

dynamic

-user-package-db

Add the user's package db to the stack.

dynamic

5.6.12. 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 Controlling extensions.

5.6.13. Warnings

More details in Warnings and sanity-checking

Flag Description Type Reverse

-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

-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

-fenable-th-splice-warnings

Generate warnings for Template Haskell splices

dynamic

-fno-enable-th-splices

-fhelpful-errors

Make suggestions for mis-spelled names.

dynamic

-fno-helpful-errors

-fmax-pmcheck-models=⟨n⟩

soft limit on the number of parallel models the pattern match checker should check a pattern match clause against

dynamic

-fshow-warning-groups

show which group an emitted warning belongs to.

dynamic

-fno-show-warning-groups

-fvia-C

use the C code generator

dynamic

-W

enable normal warnings

dynamic

-w

-w

disable all warnings

dynamic

-Wall

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

dynamic

-w

-Wall-missed-specialisations

warn when specialisation of any overloaded function fails.

dynamic

-Wno-all-missed-specialisations

-Wcompat

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

dynamic

-Wno-compat

-Wcompat-unqualified-imports

Report unqualified imports of core libraries which are expected to cause compatibility problems in future releases.

dynamic

-Wno-compat-unqualified-imports

-Wcpp-undef

warn on uses of the #if directive on undefined identifiers

dynamic

-Wdeferred-out-of-scope-variables

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

dynamic

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

-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

-Wdeprecated-flags

warn about uses of commandline flags that are deprecated

dynamic

-Wno-deprecated-flags

-Wdeprecations

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

dynamic

-Wno-deprecations

-Wderiving-defaults

warn about default deriving when using both DeriveAnyClass and GeneralizedNewtypeDeriving

dynamic

-Wno-deriving-defaults

-Wdodgy-exports

warn about dodgy exports

dynamic

-Wno-dodgy-exports

-Wdodgy-foreign-imports

warn about dodgy foreign imports

dynamic

-Wno-dodgy-foreign-import

-Wdodgy-imports

warn about dodgy imports

dynamic

-Wno-dodgy-imports

-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

-Wempty-enumerations

warn about enumerations that are empty

dynamic

-Wno-empty-enumerations

-Werror

make warnings fatal

dynamic

-Wwarn

-Weverything

enable all warnings supported by GHC

dynamic

-Whi-shadowing

(deprecated) 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-kind-vars

warn when kind variables are implicitly quantified over.

dynamic

-Wno-implicit-kind-vars

-Wimplicit-prelude

warn when the Prelude is implicitly imported

dynamic

-Wno-implicit-prelude

-Winaccessible-code

warn about inaccessible code

dynamic

-Wno-inaccessible-code

-Wincomplete-patterns

warn when a pattern match could fail

dynamic

-Wno-incomplete-patterns

-Wincomplete-record-updates

warn when a record update could fail

dynamic

-Wno-incomplete-record-updates

-Wincomplete-uni-patterns

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

dynamic

-Wno-incomplete-uni-patterns

-Winline-rule-shadowing

Warn if a rewrite RULE might fail to fire because the function might be inlined before the rule has a chance to fire. See How rules interact with INLINE/NOINLINE pragmas.

dynamic

-Wno-inline-rule-shadowing

-Winvalid-haddock

warn when a Haddock comment occurs in an invalid position

dynamic

-Wmissed-extra-shared-lib

Warn when GHCi can't load a shared lib.

dynamic

-Wno-missed-extra-shared-lib

-Wmissed-specialisations

warn when specialisation of an imported, overloaded function fails.

dynamic

-Wno-missed-specialisations

-Wmissing-deriving-strategies

warn when a deriving clause is missing a deriving strategy

dynamic

-Wno-missing-deriving-strategies

-Wmissing-export-lists

warn when a module declaration does not explicitly list all exports

dynamic

-fnowarn-missing-export-lists

-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-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-fields

warn when fields of a record are uninitialised

dynamic

-Wno-missing-fields

-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

-Wmissing-import-lists

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

dynamic

-fnowarn-missing-import-lists

-Wmissing-local-signatures

warn about polymorphic local bindings without signatures

dynamic

-Wno-missing-local-signatures

-Wmissing-local-sigs

(deprecated) warn about polymorphic local bindings without signatures

dynamic

-Wno-missing-local-sigs

-Wmissing-methods

warn when class methods are undefined

dynamic

-Wno-missing-methods

-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

-Wmissing-pattern-synonym-signatures

warn when pattern synonyms do not have type signatures

dynamic

-Wno-missing-pattern-synonym-signatures

-Wmissing-signatures

warn about top-level functions without signatures

dynamic

-Wno-missing-signatures

-Wmonomorphism-restriction

warn when the Monomorphism Restriction is applied

dynamic

-Wno-monomorphism-restriction

-Wname-shadowing

warn when names are shadowed

dynamic

-Wno-name-shadowing

-Wno-compat

Disables all warnings enabled by -Wcompat.

dynamic

-Wcompat

-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

-Woverflowed-literals

warn about literals that will overflow their type

dynamic

-Wno-overflowed-literals

-Woverlapping-patterns

warn about overlapping patterns

dynamic

-Wno-overlapping-patterns

-Wpartial-fields

warn when defining a partial record field.

dynamic

-Wno-partial-fields

-Wpartial-type-signatures

warn about holes in partial type signatures when PartialTypeSignatures is enabled. Not applicable when PartialTypeSignatures is not enabled, in which case errors are generated for such holes.

dynamic

-Wno-partial-type-signatures

-Wredundant-bang-patterns

Warn about redundant bang patterns.

dynamic

-Wno-redundant-bang-patterns

-Wredundant-constraints

Have the compiler warn about redundant constraints in type signatures.

dynamic

-Wno-redundant-constraints

-Wredundant-record-wildcards

Warn about record wildcard matches when the wildcard binds no patterns.

dynamic

-Wno-redundant-record-wildcards

-Wsafe

warn if the module being compiled is regarded to be safe.

dynamic

-Wno-safe

-Wsemigroup

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

dynamic

-Wno-semigroup

-Wsimplifiable-class-constraints

Warn about class constraints in a type signature that can be simplified using a top-level instance declaration.

dynamic

-Wno-simplifiable-class-constraints

-Wstar-binder

warn about binding the (*) type operator despite StarIsType

dynamic

-Wno-star-binder

-Wstar-is-type

warn when * is used to mean Data.Kind.Type

dynamic

-Wno-star-is-type

-Wtabs

warn if there are tabs in the source file

dynamic

-Wno-tabs

-Wtrustworthy-safe

warn if the module being compiled is marked as Trustworthy but it could instead be marked as Safe, a more informative bound.

dynamic

-Wno-safe

-Wtype-defaults

warn when defaulting happens

dynamic

-Wno-type-defaults

-Wtyped-holes

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

dynamic

-Wno-typed-holes

-Wunbanged-strict-patterns

warn on pattern bind of unlifted variable that is neither bare nor banged

dynamic

-Wno-unbanged-strict-patterns

-Wunrecognised-pragmas

warn about uses of pragmas that GHC doesn't recognise

dynamic

-Wno-unrecognised-pragmas

-Wunrecognised-warning-flags

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

dynamic

-Wno-unrecognised-warning-flags

-Wunsafe

warn if the module being compiled is regarded to be unsafe. See Safe Haskell

dynamic

-Wno-unsafe

-Wunsupported-calling-conventions

warn about use of an unsupported calling convention

dynamic

-Wno-unsupported-calling-conventions

-Wunsupported-llvm-version

Warn when using -fllvm with an unsupported version of LLVM.

dynamic

-Wno-monomorphism-restriction

-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-do-bind

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

dynamic

-Wno-unused-do-bind

-Wunused-foralls

warn about type variables in user-written forall\s that are unused

dynamic

-Wno-unused-foralls

-Wunused-imports

warn about unnecessary imports

dynamic

-Wno-unused-imports

-Wunused-local-binds

warn about local bindings that are unused

dynamic

-Wno-unused-local-binds

-Wunused-matches

warn about variables in patterns that aren't used

dynamic

-Wno-unused-matches

-Wunused-packages

warn when package is requested on command line, but was never loaded.

dynamic

-Wno-unused-packages

-Wunused-pattern-binds

warn about pattern match bindings that are unused

dynamic

-Wno-unused-pattern-binds

-Wunused-record-wildcards

Warn about record wildcard matches when none of the bound variables are used.

dynamic

-Wno-unused-record-wildcards

-Wunused-top-binds

warn about top-level bindings that are unused

dynamic

-Wno-unused-top-binds

-Wunused-type-patterns

warn about unused type variables which arise from patterns in in type family and data family instances

dynamic

-Wno-unused-type-patterns

-Wwarn

make warnings non-fatal

dynamic

-Werror

-Wwarnings-deprecations

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

dynamic

-Wno-warnings-deprecations

-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

5.6.14. 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

-O, -O1

Enable level 1 optimisations

dynamic

-O0

-O0

Disable optimisations (default)

dynamic

-O2

Enable level 2 optimisations

dynamic

-O0

-O⟨n⟩

Any -On where n > 2 is the same as -O2.

dynamic

-O0

5.6.15. 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

-fasm-shortcutting

Enable shortcutting on assembly. Implied by -O2.

dynamic

-fno-asm-shortcutting

-fbinary-blob-threshold=⟨n⟩

default: 500K. Tweak assembly generator for binary blobs.

dynamic

-fblock-layout-cfg

Use the new cfg based block layout algorithm.

dynamic

-fno-block-layout-cfg

-fblock-layout-weightless

Ignore cfg weights for code layout.

dynamic

-fno-block-layout-weightless

-fblock-layout-weights

Sets edge weights used by the new code layout algorithm.

dynamic

-fcall-arity

Enable call-arity optimisation. Implied by -O.

dynamic

-fno-call-arity

-fcase-folding

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

dynamic

-fno-case-folding

-fcase-merge

Enable case-merging. Implied by -O.

dynamic

-fno-case-merge

-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

-fcmm-static-pred

Enable static control flow prediction. Implied by -O.

dynamic

-fno-cmm-static-pred

-fcpr-anal

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

dynamic

-fno-cpr-anal

-fcross-module-specialise

Turn on specialisation of overloaded functions imported from other modules.

dynamic

-fno-cross-module-specialise

-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

(deprecated) Use a special demand transformer for dictionary selectors.

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

-fexitification

Enables exitification optimisation. Implied by -O.

dynamic

-fno-exitification

-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

-flate-specialise

Run a late specialisation pass

dynamic

-fno-late-specialise

-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

-fllvm-pass-vectors-in-regs

Pass vector value in vector registers for function calls

dynamic

-fno-llvm-pass-vectors-in-regs

-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).

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-simplifier-iterations=⟨n⟩

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

dynamic

-fmax-uncovered-patterns=⟨n⟩

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

dynamic

-fmax-worker-args=⟨n⟩

default: 10. Maximum number of value arguments for a worker.

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 hackwhereby 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

-fsimpl-tick-factor=⟨n⟩

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

dynamic

-fsimplifier-phases=⟨n⟩

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

dynamic

-fsolve-constant-dicts

When solving constraints, try to eagerly solve super classes using available dictionaries.

dynamic

-fno-solve-constant-dicts

-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-keen

Specialize a call with an explicit constructor argument, even if the argument is not scrutinised in the body of the function

dynamic

-fno-spec-constr-keen

-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

-fspecialise-aggressively

Turn on specialisation of overloaded functions regardless of size, if unfolding is available

dynamic

-fno-specialise-aggressively

-fstatic-argument-transformation

Turn on the static argument transformation.

dynamic

-fno-static-argument-transformation

-fstg-cse

Enable common sub-expression elimination on the STG intermediate language

dynamic

-fno-stg-cse

-fstg-lift-lams

Enable late lambda lifting on the STG intermediate language. Implied by -O2.

dynamic

-fno-stg-lift-lams

-fstg-lift-lams-known

Allow turning known into unknown calls while performing late lambda lifting.

dynamic

-fno-stg-lift-lams-known

-fstg-lift-lams-non-rec-args

Create top-level non-recursive functions with at most <n> parameters while performing late lambda lifting.

dynamic

-fno-stg-lift-lams-non-rec-args-any

-fstg-lift-lams-rec-args

Create top-level recursive functions with at most <n> parameters while performing late lambda lifting.

dynamic

-fno-stg-lift-lams-rec-args-any

-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: 80. Tweak unfolding settings.

dynamic

-fworker-wrapper

Enable the worker-wrapper transformation.

dynamic

5.6.16. Profiling options

More details in Profiling

Flag Description Type Reverse

-fno-prof-auto

Disables any previous -fprof-auto, -fprof-auto-top, or -fprof-auto-exported options.

dynamic

-fprof-auto

-fno-prof-cafs

Disables any previous -fprof-cafs option.

dynamic

-fprof-cafs

-fno-prof-count-entries

Do not collect entry counts

dynamic

-fprof-count-entries

-fprof-auto

Auto-add SCC\ s to all bindings not marked INLINE

dynamic

-fno-prof-auto

-fprof-auto-calls

Auto-add SCC\ s to all call sites

dynamic

-fno-prof-auto-calls

-fprof-auto-exported

Auto-add SCC\ s to all exported bindings not marked INLINE

dynamic

-fno-prof-auto

-fprof-auto-top

Auto-add SCC\ s to all top-level bindings not marked INLINE

dynamic

-fno-prof-auto

-fprof-cafs

Auto-add SCC\ s to all CAFs

dynamic

-fno-prof-cafs

-prof

Turn on profiling

dynamic

-ticky

Turn on ticky-ticky profiling

dynamic

5.6.17. Program coverage options

More details in Observing Code Coverage

Flag Description Type Reverse

-fhpc

Turn on Haskell program coverage instrumentation

dynamic

5.6.18. 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⟩

-I⟨dir⟩

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

dynamic

-U⟨symbol⟩

Undefine a symbol in the C pre-processor

dynamic

5.6.19. Code generation options

More details in Options affecting code generation

Flag Description Type Reverse

-dynamic-too

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

dynamic

-fasm

Use the native code generator

dynamic

-fllvm

-fbyte-code

Generate byte-code

dynamic

-fexternal-dynamic-refs

Generate code for linking against dynamic libraries

dynamic

-fllvm

Compile using the LLVM code generator

dynamic

-fasm

-fno-code

Omit code generation

dynamic

-fobject-code

Generate object code

dynamic

-fPIC

Generate position-independent code (where available)

dynamic

-fPIE

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

dynamic

-fwrite-interface

Always write interface files

dynamic

5.6.20. Linking options

More details in Options affecting linking

Flag Description Type Reverse

-c

Stop after generating object (.o) file

mode

-debug

Use the debugging runtime

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

-dynamic

Build dynamically-linked object files and executables

dynamic

-dynload

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

dynamic

-eventlog

Enable runtime event tracing

dynamic

-fkeep-cafs

Do not garbage-collect CAFs (top-level expressions) at runtime

dynamic

-flink-rts

Link the runtime when generating a shared or static library

dynamic

-fno-embed-manifest

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

dynamic

-fno-gen-manifest

Do not generate a manifest file (Windows only)

dynamic

-fno-shared-implib

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

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

-fwhole-archive-hs-libs

When linking a binary executable, this inserts the flag -Wl,--whole-archive before any -l flags for Haskell libraries, and -Wl,--no-whole-archive afterwards

dynamic

-L ⟨dir⟩

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

dynamic

-l ⟨lib⟩

Link in library ⟨lib⟩

dynamic

-main-is ⟨thing⟩

Set main module and function

dynamic

-no-hs-main

Don't assume this program contains main

dynamic

-no-rtsopts-suggestions

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

dynamic

-package ⟨name⟩

Expose package ⟨pkg⟩

dynamic

-pie

Instruct the linker to produce a position-independent executable.

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

-rtsopts[=⟨none|some|all|ignore|ignoreAll⟩]

Control whether the RTS behaviour can be tweaked via command-line flags 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); all (or no argument at all) means that all RTS flags are permitted; ignore means RTS flags can be given, but are treated as regular arguments and passed to the Haskell program as arguments; ignoreAll is the same as ignore, but GHCRTS is also ignored. -rtsopts does not affect -with-rtsopts behavior; flags passed via -with-rtsopts are used regardless of -rtsopts.

dynamic

-shared

Generate a shared library (as opposed to an executable)

dynamic

-split-sections

Split sections for link-time dead-code stripping

dynamic

-static

Use static Haskell libraries

dynamic

-staticlib

Generate a standalone static library (as opposed to an executable). This is useful when cross compiling. The library together with all its dependencies ends up in in a single static library that can be linked against.

dynamic

-threaded

Use the threaded runtime

dynamic

-with-rtsopts=⟨opts⟩

Set the default RTS options to ⟨opts⟩.

dynamic

5.6.21. Plugin options

More details in Compiler Plugins

Flag Description Type Reverse

-fclear-plugins

Clear the list of active plugins

dynamic

-fplugin-opt=⟨module⟩:⟨args⟩

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

dynamic

-fplugin-trustworthy

Trust the used plugins and no longer mark the compiled module as unsafe

dynamic

-fplugin=⟨module⟩

Load a plugin exported by a given module

dynamic

-hide-all-plugin-packages

Hide all packages for plugins by default

dynamic

-plugin-package ⟨pkg⟩

Expose ⟨pkg⟩ for plugins

dynamic

-plugin-package-id ⟨pkg-id⟩

Expose ⟨pkg-id⟩ for plugins

dynamic

5.6.22. Replacing phases

More details in Replacing the program for one or more phases

Flag Description Type Reverse

-pgma ⟨cmd⟩

Use ⟨cmd⟩ as the assembler

dynamic

-pgmc ⟨cmd⟩

Use ⟨cmd⟩ as the C compiler

dynamic

-pgmdll ⟨cmd⟩

Use ⟨cmd⟩ as the DLL generator

dynamic

-pgmF ⟨cmd⟩

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

dynamic

-pgmi ⟨cmd⟩

Use ⟨cmd⟩ as the external interpreter command.

dynamic

-pgmL ⟨cmd⟩

Use ⟨cmd⟩ as the literate pre-processor

dynamic

-pgml ⟨cmd⟩

Use ⟨cmd⟩ as the linker

dynamic

-pgmlc ⟨cmd⟩

Use ⟨cmd⟩ as the LLVM compiler

dynamic

-pgmlibtool ⟨cmd⟩

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

dynamic

-pgmlm ⟨cmd⟩

Use ⟨cmd⟩ as the linker when merging object files

dynamic

-pgmlo ⟨cmd⟩

Use ⟨cmd⟩ as the LLVM optimiser

dynamic

-pgmP ⟨cmd⟩

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

dynamic

-pgms ⟨cmd⟩

Use ⟨cmd⟩ as the splitter

dynamic

-pgmwindres ⟨cmd⟩

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

dynamic

5.6.23. Forcing options to particular phases

More details in Forcing options to a particular phase

Flag Description Type Reverse

-opta ⟨option⟩

pass ⟨option⟩ to the assembler

dynamic

-optc ⟨option⟩

pass ⟨option⟩ to the C compiler

dynamic

-optcxx ⟨option⟩

pass ⟨option⟩ to the C++ compiler

dynamic

-optdll ⟨option⟩

pass ⟨option⟩ to the DLL generator

dynamic

-optF ⟨option⟩

pass ⟨option⟩ to the custom pre-processor

dynamic

-opti ⟨option⟩

pass ⟨option⟩ to the interpreter sub-process.

dynamic

-optL ⟨option⟩

pass ⟨option⟩ to the literate pre-processor

dynamic

-optl ⟨option⟩

pass ⟨option⟩ to the linker

dynamic

-optlc ⟨option⟩

pass ⟨option⟩ to the LLVM compiler

dynamic

-optlm ⟨option⟩

pass ⟨option⟩ to the linker when merging object files.

dynamic

-optlo ⟨option⟩

pass ⟨option⟩ to the LLVM optimiser

dynamic

-optP ⟨option⟩

pass ⟨option⟩ to cpp (with -cpp only)

dynamic

-optwindres ⟨option⟩

pass ⟨option⟩ to windres.

dynamic

5.6.24. Platform-specific options

More details in Platform-specific Flags

Flag Description Type Reverse

-mbmi2

(x86 only) Use BMI2 for bit manipulation operations

dynamic

-msse2

(x86 only) Use SSE2 for floating-point operations

dynamic

-msse4.2

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

dynamic

5.6.25. Compiler debugging options

More details in Debugging the compiler

Flag Description Type Reverse

-dcmm-lint

C-\- pass sanity checking

dynamic

-dcore-lint

Turn on internal sanity checking

dynamic

-ddump-asm

Dump final assembly

dynamic

-ddump-asm-expanded

Dump the result of the synthetic instruction expansion pass.

dynamic

-ddump-asm-liveness

Dump assembly augmented with register liveness

dynamic

-ddump-asm-native

Dump initial assembly

dynamic

-ddump-asm-regalloc

Dump the result of register allocation

dynamic

-ddump-asm-regalloc-stages

Dump the build/spill stages of the -fregs-graph register allocator.

dynamic

-ddump-asm-stats

Dump statistics from the register allocator.

dynamic

-ddump-bcos

Dump interpreter byte code

dynamic

-ddump-cfg-weights

Dump the assumed weights of the CFG.

dynamic

-ddump-cmm

Dump the final C-\- output

dynamic

-ddump-cmm-caf

Dump the results of the C-\- CAF analysis pass.

dynamic

-ddump-cmm-cbe

Dump the results of common block elimination

dynamic

-ddump-cmm-cfg

Dump the results of the C-\- control flow optimisation pass.

dynamic

-ddump-cmm-cps

Dump the results of the CPS pass

dynamic

-ddump-cmm-from-stg

Dump STG-to-C-\- output

dynamic

-ddump-cmm-info

Dump the results of the C-\- info table augmentation pass.

dynamic

-ddump-cmm-opt

Dump the results of C-\- to C-\- optimising passes

dynamic

-ddump-cmm-proc

Dump the results of proc-point analysis

dynamic

-ddump-cmm-procmap

Dump the results of the C-\- proc-point map pass.

dynamic

-ddump-cmm-raw

Dump raw C-\-

dynamic

-ddump-cmm-sink

Dump the results of the C-\- sinking pass.

dynamic

-ddump-cmm-sp

Dump the results of the C-\- stack layout pass.

dynamic

-ddump-cmm-split

Dump the results of the C-\- proc-point splitting pass.

dynamic

-ddump-cmm-switch

Dump the results of switch lowering passes

dynamic

-ddump-cmm-verbose

Write output from main C-\- pipeline passes to files

dynamic

-ddump-cmm-verbose-by-proc

Show output from main C-\- pipeline passes (grouped by proc)

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-cpr-signatures

Dump CPR signatures

dynamic

-ddump-cpranal

Dump CPR analysis output

dynamic

-ddump-cse

Dump CSE output

dynamic

-ddump-deriv

Dump deriving output

dynamic

-ddump-ds, -ddump-ds-preopt

Dump desugarer output.

dynamic

-ddump-ec-trace

Trace exhaustiveness checker

dynamic

-ddump-file-prefix=⟨str⟩

Set the prefix of the filenames used for debugging output.

dynamic

-ddump-foreign

Dump foreign export stubs

dynamic

-ddump-hie

Dump the hie file syntax tree

dynamic

-ddump-hpc

An alias for -ddump-ticked.

dynamic

-ddump-if-trace

Trace interface files

dynamic

-ddump-inlinings

Dump inlining info

dynamic

-ddump-json

Dump error messages as JSON documents

dynamic

-ddump-llvm

Dump LLVM intermediate code.

dynamic

-ddump-mod-map

Dump the state of the module mapping database.

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-parsed-ast

Dump parser output as a syntax tree

dynamic

-ddump-prep

Dump prepared core

dynamic

-ddump-rn

Dump renamer output

dynamic

-ddump-rn-ast

Dump renamer output as a syntax tree

dynamic

-ddump-rn-stats

Renamer stats

dynamic

-ddump-rn-trace

Trace renamer

dynamic

-ddump-rtti

Trace runtime type inference

dynamic

-ddump-rule-firings

Dump rule firing info

dynamic

-ddump-rule-rewrites

Dump detailed rule firing info

dynamic

-ddump-rules

Dump rewrite rules

dynamic

-ddump-simpl

Dump final simplifier output

dynamic

-ddump-simpl-iterations

Dump output from each simplifier iteration

dynamic

-ddump-simpl-stats

Dump simplifier stats

dynamic

-ddump-spec

Dump specialiser output

dynamic

-ddump-splices

Dump TH spliced expressions, and what they evaluate to

dynamic

-ddump-stg

(deprecated) Alias for -ddump-stg-from-core

dynamic

-ddump-stg-final

Show output of last STG pass.

dynamic

-ddump-stg-from-core

Show CoreToStg output

dynamic

-ddump-stg-unarised

Show unarised STG

dynamic

-ddump-str-signatures

Dump strictness signatures

dynamic

-ddump-stranal

Dump strictness analyser output

dynamic

-ddump-tc

Dump typechecker output

dynamic

-ddump-tc-ast

Dump typechecker output as a syntax tree

dynamic

-ddump-tc-trace

Trace typechecker

dynamic

-ddump-ticked

Dump the code instrumented by HPC (Observing Code Coverage).

dynamic

-ddump-timings

Dump per-pass timing and allocation statistics

dynamic

-ddump-to-file

Dump to files instead of stdout

dynamic

-ddump-types

Dump type signatures

dynamic

-ddump-worker-wrapper

Dump worker-wrapper output

dynamic

-dfaststring-stats

Show statistics for fast string usage when finished

dynamic

-dhex-word-literals

Print values of type Word# in hexadecimal.

dynamic

-dinitial-unique=⟨s⟩

Start UniqSupply allocation from ⟨s⟩.

dynamic

-dinline-check=⟨str⟩

Dump information about inlining decisions

dynamic

-dlinear-core-lint

Turn on internal sanity checking

dynamic

-dno-debug-output

Suppress unsolicited debugging output

dynamic

-ddebug-output

-dno-typeable-binds

Don't generate bindings for Typeable methods

dynamic

-dppr-case-as-let

Print single alternative case expressions as strict lets.

dynamic

-dppr-cols=⟨n⟩

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

dynamic

-dppr-debug

Turn on debug printing (more verbose)

dynamic

-dppr-user-length

Set the depth for printing expressions in error msgs

dynamic

-drule-check=⟨str⟩

Dump information about potential rule application

dynamic

-dshow-passes

Print out each pass name as it happens

dynamic

-dstg-lint

STG pass sanity checking

dynamic

-dsuppress-all

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

dynamic

-dsuppress-coercions

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

dynamic

-dsuppress-idinfo

Suppress extended information about identifiers where they are bound

dynamic

-dsuppress-module-prefixes

Suppress the printing of module qualification prefixes

dynamic

-dsuppress-stg-free-vars

Suppress the printing of closure free variable lists in STG output

dynamic

-dsuppress-ticks

Suppress "ticks" in the pretty-printer output.

dynamic

-dsuppress-timestamps

Suppress timestamps in dumps

dynamic

-dsuppress-type-applications

Suppress type applications

dynamic

-dsuppress-type-signatures

Suppress type signatures

dynamic

-dsuppress-unfoldings

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

dynamic

-dsuppress-uniques

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

dynamic

-dsuppress-var-kinds

Suppress the printing of variable kinds

dynamic

-dth-dec-file

Dump evaluated TH declarations into *.th.hs files

dynamic

-dunique-increment=⟨i⟩

Set the increment for the generated Unique's to ⟨i⟩.

dynamic

-dverbose-core2core

Show output from each core-to-core pass

dynamic

-dverbose-stg2stg

Show output from each STG-to-STG pass

dynamic

-falignment-sanitisation

Compile with alignment checks for all info table dereferences.

dynamic

-fcatch-bottoms

Add a default error alternative to case expressions without a default alternative.

dynamic

-fllvm-fill-undef-with-garbage

Intruct LLVM to fill dead STG registers with garbage

dynamic

-fproc-alignment

Align functions at given boundary.

dynamic

-g, -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

5.6.26. Miscellaneous compiler options

Flag Description Type Reverse

-fexternal-interpreter

Run interpreted code in a separate process

dynamic

-fglasgow-exts

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

dynamic

-fno-glasgow-exts

-fno-safe-haskell

Disable Safe Haskell

dynamic

-fsort-by-size-hole-fits

Sort valid hole fits by size.

dynamic

-fno-sort-by-size-hole-fits

-fsort-by-subsumption-hole-fits

Sort valid hole fits by subsumption.

dynamic

-fno-sort-by-subsumption-hole-fits

-ghcversion-file ⟨path to ghcversion.h⟩

(GHC as a C compiler only) Use this ghcversion.h file

dynamic

-H ⟨size⟩

Set the minimum size of the heap to ⟨size⟩

dynamic

-j[⟨n⟩]

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

dynamic

-Winferred-safe-imports

warn when an explicitly Safe Haskell module imports a Safe-Inferred one

dynamic

-Wno-inferred-safe-imports

-Wmissing-safe-haskell-mode

warn when the Safe Haskell mode is not explicitly specified.

dynamic

-Wno-missing-safe-haskell-mode