GHC¶

Synopsis¶

ghc [option|filename]
ghci [option|filename]

Description¶

This manual page documents briefly the ghc and ghci commands. Note that ghci is not yet available on all architectures. Extensive documentation is available in various other formats including PDF and HTML.

Each of GHC’s command line options is classified as either static or dynamic. A static flag may only be specified on the command line, whereas a dynamic flag may also be given in an OPTIONS pragma in a source file or set from the GHCi command-line with :set .

As a rule of thumb, all the language options are dynamic, as are the warning options and the debugging options.

The rest are static, with the notable exceptions of -v, -cpp, -fasm, -fvia-C, -fllvm, and -#include. The OPTIONS sections lists the status of each flag.

Common suffixes of file names for Haskell are:

.hs

Haskell source code; preprocess, compile

.lhs

literate Haskell source; unlit, preprocess, compile

.hi

Interface file; contains information about exported symbols

.hc

intermediate C files

.⟨way⟩_o

object files for “way” ⟨way⟩; common ways are:

dyn: dynamically-linked
p: built with profiling

.⟨way⟩_hi

interface files for “way” ⟨way⟩; common ways are:

Options¶

Code generation

-dynamic-too -fasm -fllvm -fbyte-code -fbyte-code-and-object-code -fexpose-internal-symbols -fexternal-dynamic-refs -fllvm -fasm -fno-code -fobject-code -fPIC -fPIE -fprefer-byte-code -fwrite-if-simplified-core -fwrite-interface

Debugging the compiler

-dasm-lint -dcmm-lint -dcore-lint -ddisable-js-c-sources -ddisable-js-minifier -ddump-asm -ddump-asm-conflicts -ddump-asm-liveness -ddump-asm-native -ddump-asm-regalloc -ddump-asm-regalloc-stages -ddump-asm-stats -ddump-bcos -ddump-c-backend -ddump-call-arity -ddump-cfg-weights -ddump-cmm -ddump-cmm-caf -ddump-cmm-cbe -ddump-cmm-cfg -ddump-cmm-cps -ddump-cmm-from-stg -ddump-cmm-info -ddump-cmm-opt -ddump-cmm-proc -ddump-cmm-procmap -ddump-cmm-raw -ddump-cmm-sink -ddump-cmm-sp -ddump-cmm-split -ddump-cmm-switch -ddump-cmm-thread-sanitizer -ddump-cmm-verbose -ddump-cmm-verbose-by-proc -ddump-core-stats -ddump-cpr-signatures -ddump-cpranal -ddump-cs-trace -ddump-cse -ddump-debug -ddump-deriv -ddump-dmd-signatures -ddump-dmdanal -ddump-ds -ddump-ds-preopt -ddump-ec-trace -ddump-exitify -ddump-faststrings -ddump-file-prefix=⟨str⟩ -ddump-float-in -ddump-foreign -ddump-full-laziness -ddump-float-out -ddump-hie -ddump-hpc -ddump-if-trace -ddump-inlinings -ddump-js -ddump-json -ddump-late-cc -ddump-liberate-case -ddump-llvm -ddump-mod-map -ddump-occur-anal -ddump-opt-cmm -ddump-parsed -ddump-parsed-ast -ddump-prep -ddump-rn -ddump-rn-ast -ddump-rn-stats -ddump-rn-trace -ddump-rtti -ddump-rule-firings -ddump-rule-rewrites -ddump-rules -ddump-simpl -ddump-simpl-iterations -ddump-simpl-stats -ddump-simpl-trace -ddump-spec -ddump-spec-constr -ddump-splices -ddump-static-argument-transformation -ddump-stg -ddump-stg-cg -ddump-stg-final -ddump-stg-from-core -ddump-stg-tags -ddump-stg-unarised -ddump-str-signatures -ddump-stranal -ddump-tc -ddump-tc-ast -ddump-tc-trace -ddump-ticked -ddump-timings -ddump-to-file -ddump-types -ddump-verbose-inlinings -ddump-view-pattern-commoning -ddump-worker-wrapper -dfaststring-stats -dhex-word-literals -dinitial-unique=⟨s⟩ -dinline-check=⟨str⟩ -dipe-stats -dkeep-comments -dlinear-core-lint -dlint -dno-debug-output -ddebug-output -dno-typeable-binds -dppr-case-as-let -dppr-cols=⟨n⟩ -dppr-debug -dppr-user-length -drule-check=⟨str⟩ -dshow-passes -dstg-lint -dsuppress-all -dsuppress-coercion-types -dsuppress-coercions -dsuppress-core-sizes -dsuppress-idinfo -dsuppress-module-prefixes -dsuppress-stg-free-vars -dsuppress-stg-reps -dsuppress-ticks -dsuppress-timestamps -dsuppress-type-applications -dsuppress-type-signatures -dsuppress-unfoldings -dsuppress-uniques -dsuppress-var-kinds -dtag-inference-checks -dth-dec-file -dunique-increment=⟨i⟩ -dverbose-core2core -dverbose-stg2stg -falignment-sanitisation -fcatch-nonexhaustive-cases -fcheck-prim-bounds -fcmm-thread-sanitizer -fdistinct-constructor-tables -fdump-with-ways -finfo-table-map -finfo-table-map-with-fallback -fno-info-table-map-with-fallback -finfo-table-map-with-stack -fno-info-table-map-with-stack -fllvm-fill-undef-with-garbage -fno-info-table-map-with-fallback -finfo-table-map-with-fallback -fno-info-table-map-with-stack -finfo-table-map-with-stack -forig-thunk-info -fproc-alignment -funoptimized-core-for-interpreter -fno-unoptimized-core-for-interpreter -g -g⟨n⟩

C pre-processor

-cpp -D⟨symbol⟩[=⟨value⟩] -U⟨symbol⟩ -I⟨dir⟩ -U⟨symbol⟩

Finding imports

-i -i⟨dir⟩[:⟨dir⟩]*

Interactive mode

-fbreak-on-error -fno-break-on-error -fbreak-on-exception -fno-break-on-exception -fbreak-points -fno-break-points -fghci-hist-size=⟨n⟩ -fghci-leak-check -fno-ghci-leak-check -fimplicit-import-qualified -fno-implicit-import-qualified -flocal-ghci-history -fno-local-ghci-history -fno-it -fno-no-it -fprint-bind-result -fno-print-bind-result -fprint-evld-with-show -fshow-loaded-modules -ghci-script -ignore-dot-ghci -no-ignore-dot-ghci -interactive-print ⟨name⟩

Interface files

--show-iface ⟨file⟩ -ddump-hi -ddump-hi-diffs -ddump-minimal-imports

Keeping intermediate files

-keep-hc-file -keep-hc-files -keep-hi-files -no-keep-hi-files -keep-hscpp-file -keep-hscpp-files -keep-llvm-file -keep-llvm-files -keep-o-files -no-keep-o-files -keep-s-file -keep-s-files -keep-tmp-files

Language options

-XAllowAmbiguousTypes -XApplicativeDo -XArrows -XBangPatterns -XBinaryLiterals -XBlockArguments -XCApiFFI -XConstrainedClassMethods -XConstraintKinds -XCPP -XCUSKs -XDataKinds -XDatatypeContexts -XDeepSubsumption -XDefaultSignatures -XDeriveAnyClass -XDeriveDataTypeable -XDeriveFoldable -XDeriveFunctor -XDeriveGeneric -XDeriveLift -XDeriveTraversable -XDerivingStrategies -XDerivingVia -XDisambiguateRecordFields -XDuplicateRecordFields -XEmptyCase -XEmptyDataDecls -XEmptyDataDeriving -XExistentialQuantification -XExplicitForAll -XExplicitNamespaces -XExtendedDefaultRules -XExtendedLiterals -XFieldSelectors -XFlexibleContexts -XFlexibleInstances -XForeignFunctionInterface -XFunctionalDependencies -XGADTs -XGADTSyntax -XGeneralisedNewtypeDeriving -XGeneralizedNewtypeDeriving -XGHC2021 -XGHC2024 -XGHCForeignImportPrim -XHaskell2010 -XHaskell98 -XHexFloatLiterals -XImplicitParams -XImplicitPrelude -XImportQualifiedPost -XImpredicativeTypes -XIncoherentInstances -XInstanceSigs -XInterruptibleFFI -XKindSignatures -XLambdaCase -XLexicalNegation -XLiberalTypeSynonyms -XLinearTypes -XListTuplePuns -XMagicHash -XMonadComprehensions -XMonoLocalBinds -XMonomorphismRestriction -XMultilineStrings -XMultiParamTypeClasses -XMultiWayIf -XNamedDefaults -XNamedFieldPuns -XNamedWildCards -XNegativeLiterals -XNondecreasingIndentation -XNPlusKPatterns -XNullaryTypeClasses -XNumDecimals -XNumericUnderscores -XOrPatterns -XOverlappingInstances -XOverloadedLabels -XOverloadedLists -XOverloadedRecordDot -XOverloadedRecordUpdate -XOverloadedStrings -XPackageImports -XParallelListComp -XPartialTypeSignatures -XPatternGuards -XPatternSynonyms -XPolyKinds -XPostfixOperators -XQualifiedDo -XQuantifiedConstraints -XQuasiQuotes -XRank2Types -XRankNTypes -XRebindableSyntax -XRecordWildCards -XRecursiveDo -XRequiredTypeArguments -XRoleAnnotations -XSafe -XScopedTypeVariables -XStandaloneDeriving -XStandaloneKindSignatures -XStarIsType -XStaticPointers -XStrict -XStrictData -XTemplateHaskell -XTemplateHaskellQuotes -XTraditionalRecordSyntax -XTransformListComp -XTrustworthy -XTupleSections -XTypeAbstractions -XTypeApplications -XTypeData -XTypeFamilies -XTypeFamilyDependencies -XTypeInType -XTypeOperators -XTypeSynonymInstances -XUnboxedSums -XUnboxedTuples -XUndecidableInstances -XUndecidableSuperClasses -XUnicodeSyntax -XUnliftedDatatypes -XUnliftedFFITypes -XUnliftedNewtypes -XUnsafe -XViewPatterns

Linking options

-c -debug -dylib-install-name ⟨path⟩ -dynamic -dynload -eventlog -fcompact-unwind -fkeep-cafs -flink-rts -fno-embed-manifest -fno-gen-manifest -fno-shared-implib -framework ⟨name⟩ -framework-path ⟨dir⟩ -fsplit-sections -split-sections -fno-split-sections -fuse-rpaths -fwhole-archive-hs-libs -L ⟨dir⟩ -l ⟨lib⟩ -main-is ⟨thing⟩ -no-hs-main -no-pie -pie -no-rtsopts-suggestions -package ⟨name⟩ -pie -no-pie -rdynamic -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩] -shared -single-threaded -threaded -static -staticlib -threaded -single-threaded -with-rtsopts=⟨opts⟩

Miscellaneous options

-ddump-mod-cycles -fdefer-out-of-scope-variables -fno-defer-out-of-scope-variables -fdefer-type-errors -fno-defer-type-errors -fdefer-typed-holes -fno-defer-typed-holes -fexternal-interpreter -ffamily-application-cache -fno-family-application-cache -fglasgow-exts -fno-glasgow-exts -fno-safe-haskell -ghcversion-file ⟨path to ghcversion.h⟩ -H ⟨size⟩ -hidden-module ⟨module name⟩ -j[⟨n⟩] -jsem -reexported-module ⟨reexport-spec⟩ -this-package-name ⟨unit-id⟩ -unit @⟨filename⟩ -working-dir ⟨dir⟩

Modes of operation

--frontend ⟨module⟩ --help -? --info --interactive --make --numeric-version --print-booter-version --print-build-platform --print-c-compiler-flags --print-c-compiler-link-flags --print-debug-on --print-global-package-db --print-have-interpreter --print-have-native-code-generator --print-host-platform --print-ld-flags --print-leading-underscore --print-libdir --print-object-splitting-supported --print-project-git-commit-id --print-project-version --print-rts-ways --print-stage --print-support-smp --print-tables-next-to-code --print-target-platform --print-unregisterised --run ⟨file⟩ --show-iface ⟨file⟩ --show-options --supported-extensions --supported-languages --version -V -e ⟨expr⟩ -M -shared

Individual optimizations

-fasm-shortcutting -fno-asm-shortcutting -fbinary-blob-threshold=⟨n⟩ -fblock-layout-cfg -fno-block-layout-cfg -fblock-layout-weightless -fno-block-layout-weightless -fblock-layout-weights -fcall-arity -fno-call-arity -fcase-folding -fno-case-folding -fcase-merge -fno-case-merge -fcmm-control-flow -fno-cmm-control-flow -fcmm-elim-common-blocks -fno-cmm-elim-common-blocks -fcmm-sink -fno-cmm-sink -fcmm-static-pred -fno-cmm-static-pred -fcore-constant-folding -fno-core-constant-folding -fcpr-anal -fno-cpr-anal -fcross-module-specialise -fno-cross-module-specialise -fcse -fno-cse -fdicts-cheap -fno-dicts-cheap -fdicts-strict -fno-dicts-strict -fdmd-tx-dict-sel -fno-dmd-tx-dict-sel -fdmd-unbox-width=⟨n⟩ -fdo-clever-arg-eta-expansion -fno-do-clever-arg-eta-expansion -fdo-eta-reduction -fno-do-eta-reduction -fdo-lambda-eta-expansion -fno-do-lambda-eta-expansion -feager-blackholing -fenable-rewrite-rules -fno-enable-rewrite-rules -fexcess-precision -fno-excess-precision -fexitification -fno-exitification -fexpose-all-unfoldings -fno-expose-all-unfoldings -fexpose-overloaded-unfoldings -fno-expose-overloaded-unfoldings -ffloat-in -fno-float-in -ffull-laziness -fno-full-laziness -ffun-to-thunk -fno-fun-to-thunk -fignore-asserts -fno-ignore-asserts -fignore-interface-pragmas -fno-ignore-interface-pragmas -finline-generics -fno-inline-generics -finline-generics-aggressively -fno-inline-generics-aggressively -fkeep-auto-rules -fno-keep-auto-rules -flate-dmd-anal -fno-late-dmd-anal -flate-specialise -fno-late-specialise -fliberate-case -fno-liberate-case -fliberate-case-threshold=⟨n⟩ -fno-liberate-case-threshold -fllvm-pass-vectors-in-regs -flocal-float-out -fno-local-float-out -flocal-float-out-top-level -fno-local-float-out-top-level -floopification -fno-loopification -fmax-forced-spec-args=⟨n⟩ -fmax-inline-alloc-size=⟨n⟩ -fmax-inline-memcpy-insns=⟨n⟩ -fmax-inline-memset-insns=⟨n⟩ -fmax-simplifier-iterations=⟨n⟩ -fmax-uncovered-patterns=⟨n⟩ -fmax-worker-args=⟨n⟩ -fno-opt-coercion -fno-pre-inlining -fno-state-hack -fobject-determinism -fno-object-determinism -fomit-interface-pragmas -fno-omit-interface-pragmas -fomit-yields -fno-omit-yields -foptimal-applicative-do -fno-optimal-applicative-do -fpedantic-bottoms -fno-pedantic-bottoms -fpolymorphic-specialisation -fno-polymorphic-specialisation -fregs-graph -fno-regs-graph -fregs-iterative -fno-regs-iterative -fsimpl-tick-factor=⟨n⟩ -fsimplifier-phases=⟨n⟩ -fsolve-constant-dicts -fno-solve-constant-dicts -fspec-constr -fno-spec-constr -fspec-constr-count=⟨n⟩ -fno-spec-constr-count -fspec-constr-keen -fno-spec-constr-keen -fspec-constr-threshold=⟨n⟩ -fno-spec-constr-threshold -fspecialise -fno-specialise -fspecialise-aggressively -fno-specialise-aggressively -fspecialise-incoherents -fno-specialise-incoherents -fstatic-argument-transformation -fno-static-argument-transformation -fstg-cse -fno-stg-cse -fstg-lift-lams -fno-stg-lift-lams -fstg-lift-lams-known -fno-stg-lift-lams-known -fstg-lift-lams-non-rec-args -fstg-lift-lams-non-rec-args-any -fstg-lift-lams-rec-args -fstg-lift-lams-rec-args-any -fstrictness -fno-strictness -fstrictness-before=⟨n⟩ -funbox-small-strict-fields -fno-unbox-small-strict-fields -funbox-strict-fields -fno-unbox-strict-fields -funfolding-case-scaling=⟨n⟩ -funfolding-case-threshold=⟨n⟩ -funfolding-creation-threshold=⟨n⟩ -funfolding-dict-discount=⟨n⟩ -funfolding-fun-discount=⟨n⟩ -funfolding-keeness-factor=⟨n⟩ -funfolding-use-threshold=⟨n⟩ -fworker-wrapper -fworker-wrapper-cbv -fwrite-if-compression=⟨n⟩

Optimization levels

-O -O1 -O0 -O0 -O2 -O0 -O⟨n⟩ -O0

Package options

-clear-package-db -distrust ⟨pkg⟩ -distrust-all-packages -fpackage-trust -global-package-db -hide-all-packages -hide-package ⟨pkg⟩ -ignore-package ⟨pkg⟩ -no-auto-link-packages -no-global-package-db -no-user-package-db -package ⟨pkg⟩ -package-db ⟨file⟩ -package-env ⟨file⟩|⟨name⟩ -package-id ⟨unit-id⟩ -this-unit-id ⟨unit-id⟩ -trust ⟨pkg⟩ -user-package-db

Phases of compilation

--merge-objs -C -c -E -F -S -x ⟨suffix⟩

Overriding external programs

-pgma ⟨cmd⟩ -pgmc ⟨cmd⟩ -pgmCmmP ⟨cmd⟩ -pgmcxx ⟨cmd⟩ -pgmF ⟨cmd⟩ -pgmi ⟨cmd⟩ -pgminstall_name_tool ⟨cmd⟩ -pgmJSP ⟨cmd⟩ -pgmL ⟨cmd⟩ -pgml ⟨cmd⟩ -pgmlas ⟨cmd⟩ -pgmlc ⟨cmd⟩ -pgmlm ⟨cmd⟩ -pgmlo ⟨cmd⟩ -pgmotool ⟨cmd⟩ -pgmP ⟨cmd⟩ -pgms ⟨cmd⟩ -pgmwindres ⟨cmd⟩

Phase-specific options

-opta ⟨option⟩ -optc ⟨option⟩ -optCmmP ⟨option⟩ -optcxx ⟨option⟩ -optF ⟨option⟩ -opti ⟨option⟩ -optJSP ⟨option⟩ -optL ⟨option⟩ -optl ⟨option⟩ -optlas ⟨option⟩ -optlc ⟨option⟩ -optlm ⟨option⟩ -optlo ⟨option⟩ -optP ⟨option⟩ -optwindres ⟨option⟩ -pgmc-supports-no-pie -pgml-supports-no-pie

Platform-specific options

-mavx -mavx2 -mavx512cd -mavx512er -mavx512f -mavx512pf -mbmi -mbmi2 -mfma -msse -msse2 -msse3 -msse4 -msse4.2

Compiler plugins

-fclear-plugins -fplugin-library=⟨file-path⟩;⟨unit-id⟩;⟨module⟩;⟨args⟩ -fplugin-opt=⟨module⟩:⟨args⟩ -fplugin-trustworthy -fplugin=⟨module⟩ -hide-all-plugin-packages -plugin-package ⟨pkg⟩ -plugin-package-id ⟨pkg-id⟩

Profiling

-auto -auto-all -caf-all -fno-prof-count-entries -fprof-count-entries -fprof-auto -fno-prof-auto -fprof-auto-calls -fno-prof-auto -fprof-auto-exported -fno-prof-auto -fprof-auto-top -fno-prof-auto -fprof-cafs -fno-prof-cafs -fprof-callers=⟨name⟩ -fprof-late -fno-prof-late -fprof-late-inline -fno-prof-late-inline -fprof-late-overloaded -fno-prof-late-overloaded -fprof-late-overloaded-calls -fno-prof-late-overloaded-calls -fprof-manual -fno-prof-manual -no-auto -no-auto-all -no-caf-all -prof -ticky -ticky-allocd -ticky-ap-thunk -ticky-dyn-thunk -ticky-LNE -ticky-tag-checks

Program coverage

-fhpc -hpcdir⟨dir⟩

Recompilation checking

-exclude-module=⟨file⟩ -fforce-recomp -fno-force-recomp -fignore-hpc-changes -fno-ignore-hpc-changes -fignore-optim-changes -fno-ignore-optim-changes -include-cpp-deps -include-pkg-deps

Redirecting output

-dep-makefile ⟨file⟩ -dep-suffix ⟨suffix⟩ -dumpdir ⟨dir⟩ -dynhisuf ⟨suffix⟩ -dyno ⟨file⟩ -dynohi ⟨file⟩ -dynosuf ⟨suffix⟩ -hcsuf ⟨suffix⟩ -hidir ⟨dir⟩ -hiedir ⟨dir⟩ -hiesuf ⟨suffix⟩ -hisuf ⟨suffix⟩ -o ⟨file⟩ -odir ⟨dir⟩ -ohi ⟨file⟩ -osuf ⟨suffix⟩ -outputdir ⟨dir⟩ -stubdir ⟨dir⟩

Temporary files

-tmpdir ⟨dir⟩

Verbosity options

-fabstract-refinement-hole-fits -fno-abstract-refinement-hole-fits -fdefer-diagnostics -fdiagnostics-as-json -fdiagnostics-color=⟨always|auto|never⟩ -fdiagnostics-show-caret -fno-diagnostics-show-caret -ferror-spans -fhide-source-paths -fkeep-going -fmax-refinement-hole-fits=⟨n⟩ -fno-max-refinement-hole-fits -fmax-relevant-binds=⟨n⟩ -fno-max-relevant-binds -fmax-valid-hole-fits=⟨n⟩ -fno-max-valid-hole-fits -fno-show-valid-hole-fits -fno-sort-valid-hole-fits -fsort-valid-hole-fits -fprint-axiom-incomps -fno-print-axiom-incomps -fprint-equality-relations -fno-print-equality-relations -fprint-error-index-links=⟨always|auto|never⟩ -fprint-expanded-synonyms -fno-print-expanded-synonyms -fprint-explicit-coercions -fno-print-explicit-coercions -fprint-explicit-foralls -fno-print-explicit-foralls -fprint-explicit-kinds -fno-print-explicit-kinds -fprint-explicit-runtime-reps -fno-print-explicit-runtime-reps -fprint-potential-instances -fno-print-potential-instances -fprint-redundant-promotion-ticks -fno-print-redundant-promotion-ticks -fprint-typechecker-elaboration -fno-print-typechecker-elaboration -fprint-unicode-syntax -fno-print-unicode-syntax -frefinement-level-hole-fits=⟨n⟩ -fno-refinement-level-hole-fits -freverse-errors -fno-reverse-errors -fshow-docs-of-hole-fits -fno-show-docs-of-hole-fits -fshow-error-context -fno-show-error-context -fshow-hole-constraints -fshow-hole-matches-of-hole-fits -fno-show-hole-matches-of-hole-fits -fshow-provenance-of-hole-fits -fno-show-provenance-of-hole-fits -fshow-type-app-of-hole-fits -fno-show-type-app-of-hole-fits -fshow-type-app-vars-of-hole-fits -fno-show-type-app-vars-of-hole-fits -fshow-type-of-hole-fits -fno-show-type-of-hole-fits -fsort-by-size-hole-fits -fno-sort-by-size-hole-fits -fsort-by-subsumption-hole-fits -fno-sort-by-subsumption-hole-fits -funclutter-valid-hole-fits -Rghc-timing -v -v⟨n⟩

Warnings

-fenable-th-splice-warnings -fno-enable-th-splice-warnings -fhelpful-errors -fno-helpful-errors -fmax-pmcheck-models=⟨n⟩ -fshow-warning-groups -fno-show-warning-groups -fvia-C -W -Wno-extra -w -Wall -Wno-all -Wall-missed-specialisations -Wno-all-missed-specialisations -Wall-missed-specializations -Wno-all-missed-specializations -Wambiguous-fields -Wauto-orphans -Wbadly-staged-types -Wno-badly-staged-types -Wcompat -Wno-compat -Wcompat-unqualified-imports -Wno-compat-unqualified-imports -Wcpp-undef -Wdata-kinds-tc -Wno-data-kinds-tc -Wdefault -Wno-default -Wdefaulted-exception-context -Wnop-defaulted-exception-context -Wdeferred-out-of-scope-variables -Wno-deferred-out-of-scope-variables -Wdeferred-type-errors -Wno-deferred-type-errors -Wdeprecated-flags -Wno-deprecated-flags -Wdeprecated-type-abstractions -Wno-deprecated-type-abstractions -Wdeprecations -Wno-deprecations -Wderiving-defaults -Wno-deriving-defaults -Wderiving-typeable -Wno-deriving-typeable -Wdodgy-exports -Wno-dodgy-exports -Wdodgy-foreign-imports -Wno-dodgy-foreign-imports -Wdodgy-imports -Wno-dodgy-imports -Wduplicate-constraints -Wno-duplicate-constraints -Wduplicate-exports -Wno-duplicate-exports -Wempty-enumerations -Wno-empty-enumerations -Werror -Wwarn -Weverything -w -Wextended-warnings -Wno-extended-warnings -Wextra -Wno-extra -Wforall-identifier -Wgadt-mono-local-binds -Wno-gadt-mono-local-binds -Whi-shadowing -Wno-hi-shadowing -Widentities -Wno-identities -Wimplicit-kind-vars -Wno-implicit-kind-vars -Wimplicit-lift -Wno-implicit-lift -Wimplicit-prelude -Wno-implicit-prelude -Wimplicit-rhs-quantification -Wno-implicit-rhs-quantification -Winaccessible-code -Wno-inaccessible-code -Wincomplete-export-warnings -Wno-incomplete-export-warnings -Wincomplete-patterns -Wno-incomplete-patterns -Wincomplete-record-selectors -Wno-incomplete-record-selectors -Wincomplete-record-updates -Wno-incomplete-record-updates -Wincomplete-uni-patterns -Wno-incomplete-uni-patterns -Winconsistent-flags -Wno-inconsistent-flags -Winferred-safe-imports -Wno-inferred-safe-imports -Winline-rule-shadowing -Wno-inline-rule-shadowing -Winvalid-haddock -Wno-invalid-haddock -Wloopy-superclass-solve -Wno-loopy-superclass-solve -Wmisplaced-pragmas -Wno-misplaced-pragmas -Wmissed-extra-shared-lib -Wno-missed-extra-shared-lib -Wmissed-specialisations -Wno-missed-specialisations -Wmissed-specializations -Wno-missed-specializations -Wmissing-deriving-strategies -Wno-missing-deriving-strategies -Wmissing-export-lists -Wno-missing-export-lists -Wmissing-exported-pattern-synonym-signatures -Wno-missing-exported-pattern-synonym-signatures -Wmissing-exported-signatures -Wno-missing-exported-signatures -Wmissing-exported-sigs -Wno-missing-exported-sigs -Wmissing-fields -Wno-missing-fields -Wmissing-home-modules -Wno-missing-home-modules -Wmissing-import-lists -Wno-missing-import-lists -Wmissing-kind-signatures -Wno-missing-kind-signatures -Wmissing-local-signatures -Wno-missing-local-signatures -Wmissing-local-sigs -Wno-missing-local-sigs -Wmissing-methods -Wno-missing-methods -Wmissing-monadfail-instances -Wno-missing-monadfail-instances -Wmissing-pattern-synonym-signatures -Wno-missing-pattern-synonym-signatures -Wmissing-poly-kind-signatures -Wno-missing-poly-kind-signatures -Wmissing-role-annotations -Wno-role-annotations-signatures -Wmissing-safe-haskell-mode -Wno-missing-safe-haskell-mode -Wmissing-signatures -Wno-missing-signatures -Wmissing-space-after-bang -Wmonomorphism-restriction -Wno-monomorphism-restriction -Wname-shadowing -Wno-name-shadowing -Wnoncanonical-monad-instances -Wno-noncanonical-monad-instances -Wnoncanonical-monadfail-instances -Wno-noncanonical-monadfail-instances -Wnoncanonical-monoid-instances -Wno-noncanonical-monoid-instances -Wnot -Woperator-whitespace -Wno-operator-whitespace -Woperator-whitespace-ext-conflict -Wno-operator-whitespace-ext-conflict -Worphans -Wno-orphans -Woverflowed-literals -Wno-overflowed-literals -Woverlapping-patterns -Wno-overlapping-patterns -Wpartial-fields -Wno-partial-fields -Wpartial-type-signatures -Wno-partial-type-signatures -Wprepositive-qualified-module -Wno-prepositive-qualified-module -Wredundant-bang-patterns -Wno-redundant-bang-patterns -Wredundant-constraints -Wno-redundant-constraints -Wredundant-record-wildcards -Wno-redundant-record-wildcards -Wredundant-strictness-flags -Wno-redundant-strictness-flags -Wsafe -Wno-safe -Wsemigroup -Wno-semigroup -Wsimplifiable-class-constraints -Wno-simplifiable-class-constraints -Wstar-binder -Wno-star-binder -Wstar-is-type -Wno-star-is-type -Wtabs -Wno-tabs -Wterm-variable-capture -Wtrustworthy-safe -Wno-safe -Wtype-defaults -Wno-type-defaults -Wtype-equality-out-of-scope -Wno-type-equality-out-of-scope -Wtype-equality-requires-operators -Wno-type-equality-requires-operators -Wtyped-holes -Wno-typed-holes -Wunbanged-strict-patterns -Wno-unbanged-strict-patterns -Wunicode-bidirectional-format-characters -Wunrecognised-pragmas -Wno-unrecognised-pragmas -Wunrecognised-warning-flags -Wno-unrecognised-warning-flags -Wunsafe -Wno-unsafe -Wunsupported-calling-conventions -Wno-unsupported-calling-conventions -Wunsupported-llvm-version -Wno-unsupported-llvm-version -Wunticked-promoted-constructors -Wno-unticked-promoted-constructors -Wunused-binds -Wno-unused-binds -Wunused-do-bind -Wno-unused-do-bind -Wunused-foralls -Wno-unused-foralls -Wunused-imports -Wno-unused-imports -Wunused-local-binds -Wno-unused-local-binds -Wunused-matches -Wno-unused-matches -Wunused-packages -Wno-unused-packages -Wunused-pattern-binds -Wno-unused-pattern-binds -Wunused-record-wildcards -Wno-unused-record-wildcards -Wunused-top-binds -Wno-unused-top-binds -Wunused-type-patterns -Wno-unused-type-patterns -Wview-pattern-signatures -Wno-view-pattern-signatures -Wwarn -Werror -Wwarnings-deprecations -Wno-warnings-deprecations -Wwrong-do-bind -Wno-wrong-do-bind -Wx-⟨category⟩ -Wno-x-⟨category⟩

Code generation¶

-dynamic-too: Build dynamic object files as well as static object files during compilation
-fasm: Use the native code generator
-fbyte-code: Generate byte-code
-fbyte-code-and-object-code: Generate object code and byte-code
-fexpose-internal-symbols: Produce symbols for all functions, including internal functions.
-fexternal-dynamic-refs: Generate code for linking against dynamic libraries
-fllvm: Compile using the LLVM code generator
-fno-code: Omit code generation
-fobject-code: Generate object code
-fPIC: Generate position-independent code (where available)
-fPIE: Generate code for a position-independent executable (where available)
-fprefer-byte-code: Use byte-code if it is available to evaluate TH splices
-fwrite-if-simplified-core: Write an interface file containing the simplified core of the module.
-fwrite-interface: Always write interface files

Debugging the compiler¶

-dasm-lint: ASM pass sanity checking
-dcmm-lint: C-\- pass sanity checking
-dcore-lint: Turn on internal sanity checking
-ddisable-js-c-sources: Disable the link with C sources compiled to JavaScript
-ddisable-js-minifier: Generate pretty-printed JavaScript code instead of minified (compacted) code.
-ddump-asm: Dump final assembly
-ddump-asm-conflicts: Dump register conflicts from the register allocator.
-ddump-asm-liveness: Dump assembly augmented with register liveness
-ddump-asm-native: Dump initial assembly
-ddump-asm-regalloc: Dump the result of register allocation
-ddump-asm-regalloc-stages: Dump the build/spill stages of the -fregs-graph register allocator.
-ddump-asm-stats: Dump statistics from the register allocator.
-ddump-bcos: Dump interpreter byte code
-ddump-c-backend: Dump C code produced by the C (unregisterised) backend.
-ddump-call-arity: Dump output of the call arity analysis pass.
-ddump-cfg-weights: Dump the assumed weights of the CFG.
-ddump-cmm: Dump the final C-\- output
-ddump-cmm-caf: Dump the results of the C-\- CAF analysis pass.
-ddump-cmm-cbe: Dump the results of common block elimination
-ddump-cmm-cfg: Dump the results of the C-\- control flow optimisation pass.
-ddump-cmm-cps: Dump the results of the CPS pass
-ddump-cmm-from-stg: Dump STG-to-C-\- output
-ddump-cmm-info: Dump the results of the C-\- info table augmentation pass.
-ddump-cmm-opt: Dump the results of C-\- to C-\- optimising passes
-ddump-cmm-proc: Dump the results of proc-point analysis
-ddump-cmm-procmap: Dump the results of the C-\- proc-point map pass.
-ddump-cmm-raw: Dump raw C-\-
-ddump-cmm-sink: Dump the results of the C-\- sinking pass.
-ddump-cmm-sp: Dump the results of the C-\- stack layout pass.
-ddump-cmm-split: Dump the results of the C-\- proc-point splitting pass.
-ddump-cmm-switch: Dump the results of switch lowering passes
-ddump-cmm-thread-sanitizer: Dump the results of the C-\- ThreadSanitizer elaboration pass.
-ddump-cmm-verbose: Write output from main C-\- pipeline passes to files
-ddump-cmm-verbose-by-proc: Show output from main C-\- pipeline passes (grouped by proc)
-ddump-core-stats: Print a one-line summary of the size of the Core program at the end of the optimisation pipeline
-ddump-cpr-signatures: Dump CPR signatures
-ddump-cpranal: Dump CPR analysis output
-ddump-cs-trace: Trace constraint solver
-ddump-cse: Dump CSE output
-ddump-debug: Dump generated DWARF debug information
-ddump-deriv: Dump deriving output
-ddump-dmd-signatures: Dump top-level demand signatures
-ddump-dmdanal: Dump demand analysis output
-ddump-ds: Dump desugarer output.
-ddump-ec-trace: Trace exhaustiveness checker
-ddump-exitify: Dump output of the exitification pass.
-ddump-faststrings: Dump the whole FastString table when finished
-ddump-file-prefix=⟨str⟩: Set the prefix of the filenames used for debugging output.
-ddump-float-in: Dump float in output
-ddump-foreign: Dump foreign export stubs
-ddump-full-laziness: Dump full laziness pass output
-ddump-hie: Dump the hie file syntax tree
-ddump-hpc: An alias for -ddump-ticked.
-ddump-if-trace: Trace interface files
-ddump-inlinings: Dump inlinings performed by the simplifier.
-ddump-js: Dump final JavaScript code
-ddump-json: (deprecated) Use -fdiagnostics-as-json instead
-ddump-late-cc: Dump core with late cost centres added
-ddump-liberate-case: Dump liberate case output
-ddump-llvm: Dump LLVM intermediate code.
-ddump-mod-map: Dump the state of the module mapping database.
-ddump-occur-anal: Dump occurrence analysis output
-ddump-opt-cmm: Dump the results of C-\- to C-\- optimising passes
-ddump-parsed: Dump parse tree
-ddump-parsed-ast: Dump parser output as a syntax tree
-ddump-prep: Dump prepared core
-ddump-rn: Dump renamer output
-ddump-rn-ast: Dump renamer output as a syntax tree
-ddump-rn-stats: Renamer stats
-ddump-rn-trace: Trace renamer
-ddump-rtti: Trace runtime type inference
-ddump-rule-firings: Dump rule firing info
-ddump-rule-rewrites: Dump detailed rule firing info
-ddump-rules: Dump rewrite rules
-ddump-simpl: Dump final simplifier output
-ddump-simpl-iterations: Dump output from each simplifier iteration
-ddump-simpl-stats: Dump simplifier stats
-ddump-simpl-trace: Dump trace messages in simplifier
-ddump-spec: Dump specialiser output
-ddump-spec-constr: Dump specialiser output from SpecConstr
-ddump-splices: Dump TH spliced expressions, and what they evaluate to
-ddump-static-argument-transformation: Dump static argument transformation output
-ddump-stg: (deprecated) Alias for -ddump-stg-from-core
-ddump-stg-cg: Show output after Stg2Stg
-ddump-stg-final: Show output of last STG pass.
-ddump-stg-from-core: Show CoreToStg output
-ddump-stg-tags: Show output of the tag inference pass.
-ddump-stg-unarised: Show unarised STG
-ddump-str-signatures: (deprecated) Alias for -ddump-dmd-signatures
-ddump-stranal: (deprecated) Alias for -ddump-dmdanal
-ddump-tc: Dump typechecker output
-ddump-tc-ast: Dump typechecker output as a syntax tree
-ddump-tc-trace: Trace typechecker
-ddump-ticked: Dump the code instrumented by HPC (Observing Code Coverage).
-ddump-timings: Dump per-pass timing and allocation statistics
-ddump-to-file: Dump to files instead of stdout
-ddump-types: Dump type signatures
-ddump-verbose-inlinings: Dump all considered inlinings
-ddump-view-pattern-commoning: Dump commoned view patterns
-ddump-worker-wrapper: Dump worker-wrapper output
-dfaststring-stats: Show statistics for fast string usage when finished
-dhex-word-literals: Print values of type Word# in hexadecimal.
-dinitial-unique=⟨s⟩: Start UniqSupply allocation from ⟨s⟩.
-dinline-check=⟨str⟩: Dump information about inlining decisions
-dipe-stats: Show statistics about IPE information
-dkeep-comments: Include comments in the parser. Useful in combination with -ddump-parsed-ast.
-dlinear-core-lint: Turn on internal sanity checking
-dlint: Enable several common internal sanity checkers
-dno-debug-output: Suppress unsolicited debugging output
-dno-typeable-binds: Don't generate bindings for Typeable methods
-dppr-case-as-let: Print single alternative case expressions as strict lets.
-dppr-cols=⟨n⟩: Set the width of debugging output. For example -dppr-cols200
-dppr-debug: Turn on debug printing (more verbose)
-dppr-user-length: Set the depth for printing expressions in error msgs
-drule-check=⟨str⟩: Dump information about potential rule application
-dshow-passes: Print out each pass name as it happens
-dstg-lint: STG pass sanity checking
-dsuppress-all: In dumps, suppress everything (except for uniques) that is suppressible.
-dsuppress-coercion-types: Suppress the printing of coercion types in Core dumps to make them shorter
-dsuppress-coercions: Suppress the printing of coercions in Core dumps to make them shorter
-dsuppress-core-sizes: Suppress the printing of core size stats per binding (since 9.4)
-dsuppress-idinfo: Suppress extended information about identifiers where they are bound
-dsuppress-module-prefixes: Suppress the printing of module qualification prefixes
-dsuppress-stg-free-vars: Suppress the printing of closure free variable lists in STG output
-dsuppress-stg-reps: Suppress rep annotations on STG args.
-dsuppress-ticks: Suppress "ticks" in the pretty-printer output.
-dsuppress-timestamps: Suppress timestamps in dumps
-dsuppress-type-applications: Suppress type applications
-dsuppress-type-signatures: Suppress type signatures
-dsuppress-unfoldings: Suppress the printing of the stable unfolding of a variable at its binding site
-dsuppress-uniques: Suppress the printing of uniques in debug output (easier to use diff)
-dsuppress-var-kinds: Suppress the printing of variable kinds
-dtag-inference-checks: Affirm tag inference results are correct at runtime.
-dth-dec-file: Dump evaluated TH declarations into *.th.hs files
-dunique-increment=⟨i⟩: Set the increment for the generated Unique's to ⟨i⟩.
-dverbose-core2core: Show output from each core-to-core pass
-dverbose-stg2stg: Show output from each STG-to-STG pass
-falignment-sanitisation: Compile with alignment checks for all info table dereferences.
-fcatch-nonexhaustive-cases: Add a default error alternative to case expressions without a default alternative.
-fcheck-prim-bounds: Instrument array primops with bounds checks.
-fcmm-thread-sanitizer: Enable ThreadSanitizer instrumentation of memory accesses.
-fdistinct-constructor-tables: Generate a fresh info table for each usage of a data constructor.
-fdump-with-ways: Include the tag of the enabled ways in the extension of dump files.
-finfo-table-map: Embed a lookup table in the generated binary which maps the address of an info table to the source position the closure originated from.
-finfo-table-map-with-fallback: Include info tables with no source location information in the info table map.
-finfo-table-map-with-stack: Include info tables for STACK closures in the info table map.
-fllvm-fill-undef-with-garbage: Intruct LLVM to fill dead STG registers with garbage
-fno-info-table-map-with-fallback: Omit info tables with no source location information from the info table map.
-fno-info-table-map-with-stack: Omit info tables for STACK closures from the info table map.
-forig-thunk-info: Generate stg_orig_thunk_info stack frames on thunk entry
-fproc-alignment: Align functions at given boundary.
-funoptimized-core-for-interpreter: Disable optimizations with the interpreter
-g: 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.

C pre-processor¶

-cpp: Run the C pre-processor on Haskell source files
-D⟨symbol⟩[=⟨value⟩]: Define a symbol in the C pre-processor
-I⟨dir⟩: Add ⟨dir⟩ to the directory search list for #include files
-U⟨symbol⟩: Undefine a symbol in the C pre-processor

Finding imports¶

-i: Empty the import directory list
-i⟨dir⟩[:⟨dir⟩]*: add ⟨dir⟩, ⟨dir2⟩, etc. to import path

Interactive mode¶

-fbreak-on-error: Break on uncaught exceptions and errors
-fbreak-on-exception: Break on any exception thrown
-fbreak-points: Insert breakpoints in the GHCi debugger
-fghci-hist-size=⟨n⟩: Set the number of entries GHCi keeps for :history. See The GHCi Debugger.
-fghci-leak-check: (Debugging only) check for space leaks when loading new modules in GHCi.
-fimplicit-import-qualified: Put in scope qualified identifiers for every loaded module
-flocal-ghci-history: Use current directory for the GHCi command history file .ghci-history.
-fno-it: No longer set the special variable it.
-fprint-bind-result: Turn on printing of binding results in GHCi
-fprint-evld-with-show: Instruct :print to use Show instances where possible.
-fshow-loaded-modules: Show the names of modules that GHCi loaded after a :load command.
-ghci-script: Read additional .ghci files
-ignore-dot-ghci: Disable reading of .ghci files
-interactive-print ⟨name⟩: Select the function to use for printing evaluated expressions in GHCi

Interface files¶

--show-iface ⟨file⟩: See Modes of operation.
-ddump-hi: Dump the new interface to stdout
-ddump-hi-diffs: Show the differences vs. the old interface
-ddump-minimal-imports: Dump a minimal set of imports

Keeping intermediate files¶

-keep-hc-file: Retain intermediate .hc files.
-keep-hi-files: Retain intermediate .hi files (the default).
-keep-hscpp-file: Retain intermediate .hscpp files.
-keep-llvm-file: Retain intermediate LLVM .ll files. Implies -fllvm.
-keep-o-files: Retain intermediate .o files (the default).
-keep-s-file: Retain intermediate .s files.
-keep-tmp-files: Retain all intermediate temporary files.

Language options¶

-XAllowAmbiguousTypes: Allow the user to write ambiguous types, and the type inference engine to infer them.
-XApplicativeDo: Allow do-notation statements to be desugared via Applicative.
-XArrows: Allow arrow notation (e.g. proc)
-XBangPatterns: Allow bang pattern syntax.
-XBinaryLiterals: Allow binary literal syntax.
-XBlockArguments: Allow do blocks and other constructs as function arguments.
-XCApiFFI: Allow foreign imports to be declared with the capi calling convention.
-XConstrainedClassMethods: Allow class methods to have non-empty contexts.
-XConstraintKinds: Allow constraints to be used as types of kind Constraint.
-XCPP: Resolve C preprocessor directives.
-XCUSKs: Detect complete user-supplied kind signatures.
-XDataKinds: Allow use of data constructors in types.
-XDatatypeContexts: Allow contexts on data types.
-XDeepSubsumption: Use GHC's deep subsumption checking.
-XDefaultSignatures: Allow default signatures for typeclass methods.
-XDeriveAnyClass: Allow deriving syntax to be used for any class.
-XDeriveDataTypeable: Allow deriving for the Data class.
-XDeriveFoldable: Allow deriving for the Foldable class.
-XDeriveFunctor: Allow deriving for the Functor class.
-XDeriveGeneric: Allow deriving of Generic instances.
-XDeriveLift: Allow deriving for the Lift class
-XDeriveTraversable: Allow deriving for the Traversable class.
-XDerivingStrategies: Allow use of instance deriving strategies.
-XDerivingVia: Allow deriving instances via types of the same runtime representation.
-XDisambiguateRecordFields: Automatically disambiguate some record field references.
-XDuplicateRecordFields: Allow definition of record types with identically-named fields.
-XEmptyCase: Allow case expressions with no alternatives.
-XEmptyDataDecls: Allow definition of empty data types.
-XEmptyDataDeriving: Allow deriving instances of standard type classes for empty data types.
-XExistentialQuantification: Allow existentially quantified type variables in types.
-XExplicitForAll: Allow explicit universal quantification.
-XExplicitNamespaces: Allow use of the keyword type to specify the namespace of entries in imports and exports.
-XExtendedDefaultRules: Use GHCi's extended default rules in a normal module.
-XExtendedLiterals: Allow numeric literal postfix syntax for unboxed integers.
-XFieldSelectors: Make record field selector functions visible in expressions.
-XFlexibleContexts: Remove some restrictions on class contexts
-XFlexibleInstances: Allow instance heads to mention arbitrary nested types.
-XForeignFunctionInterface: Allow foreign function interface syntax.
-XFunctionalDependencies: Allow functional dependencies to be given on typeclass declarations.
-XGADTs: Allow definition of generalised algebraic data types.
-XGADTSyntax: Allow generalised algebraic data type syntax.
-XGeneralisedNewtypeDeriving: Allow instances to be derived via newtype deriving.
-XGeneralizedNewtypeDeriving: Allow instances to be derived via newtype deriving.
-XGHC2021: Use GHC’s set of default language extensions from 2021
-XGHC2024: Use GHC’s set of default language extensions from 2024
-XGHCForeignImportPrim: Allow prim calling convention. Intended for internal use only.
-XHaskell2010: Use the Haskell 2010 language edition.
-XHaskell98: Use the Haskell 98 language edition.
-XHexFloatLiterals: Allow hexadecimal floating-point literal syntax.
-XImplicitParams: Allow implicit parameter constraints.
-XImplicitPrelude: Implicitly import Prelude.
-XImportQualifiedPost: Allows the syntax import M qualified
-XImpredicativeTypes: Allow impredicative types.
-XIncoherentInstances: Allow definitions of instances that may result in incoherence.
-XInstanceSigs: Allow type signatures to be written for instance methods.
-XInterruptibleFFI: Allow interruptible FFI imports.
-XKindSignatures: Allow kind signatures to be given for types.
-XLambdaCase: Allow \case expressions.
-XLexicalNegation: Use whitespace to determine whether the minus sign stands for negation or subtraction.
-XLiberalTypeSynonyms: Relax many of Haskell 98's rules on type synonym definitions.
-XLinearTypes: Allow writing of linear arrow types. Implies MonoLocalBinds.
-XListTuplePuns: Enable punning for list, tuple and sum types.
-XMagicHash: Allow # as a postfix modifier on identifiers.
-XMonadComprehensions: Allow list comprehension syntax to be used at monads other than List.
-XMonoLocalBinds: Do not generalise types of local bindings.
-XMonomorphismRestriction: Apply the Haskell 2010 monomorphism restriction.
-XMultilineStrings: Enable multiline string literals.
-XMultiParamTypeClasses: Enable multi-parameter type classes.
-XMultiWayIf: Allow multi-way if-expressions.
-XNamedDefaults: Enable default declarations with explicitly named class.
-XNamedFieldPuns: Allow record field punning syntax.
-XNamedWildCards: Allow named wildcards in types.
-XNegativeLiterals: Allow negative numeric literal syntax.
-XNondecreasingIndentation: Allow nested contexts to be at the same indentation level as its enclosing context.
-XNPlusKPatterns: Allow use of n+k patterns.
-XNullaryTypeClasses: Deprecated, does nothing. nullary type classes are now enabled using MultiParamTypeClasses.
-XNumDecimals: Allow use of scientific notation syntax for integer literals.
-XNumericUnderscores: Allow underscores in numeric literals.
-XOrPatterns: Enable or-patterns.
-XOverlappingInstances: Allow definition of overlapping instances.
-XOverloadedLabels: Allow overloaded label syntax.
-XOverloadedLists: Desugar list syntax via the IsList class.
-XOverloadedRecordDot: Allow . to be used for record field access.
-XOverloadedRecordUpdate: Allow . syntax in record updates
-XOverloadedStrings: Desugar string literals via IsString class.
-XPackageImports: Allow package-qualified import syntax.
-XParallelListComp: Allow parallel list comprehension syntax.
-XPartialTypeSignatures: Allow type signatures to contain wildcards.
-XPatternGuards: Allow pattern guards syntax.
-XPatternSynonyms: Allow definition of pattern synonyms.
-XPolyKinds: Allow kind polymorphism.
-XPostfixOperators: Allow the use of postfix operators.
-XQualifiedDo: Allow qualified do-notation desugaring.
-XQuantifiedConstraints: Allow forall quantifiers in constraints.
-XQuasiQuotes: Allow quasiquotation syntax.
-XRank2Types: Enable rank-2 types.
-XRankNTypes: Allow types of rank greater than one.
-XRebindableSyntax: Allow rebinding of builtin syntax.
-XRecordWildCards: Allow use of record wildcard syntax.
-XRecursiveDo: Allow recursive do (e.g. mdo) notation.
-XRequiredTypeArguments: Allow use of required type argument syntax in terms.
-XRoleAnnotations: Allow role annotation syntax.
-XSafe: Enable the Safe Haskell Safe mode.
-XScopedTypeVariables: Lexically scope explicitly-introduced type variables.
-XStandaloneDeriving: Allow standalone instance deriving declarations.
-XStandaloneKindSignatures: Allow standalone kind signature declarations.
-XStarIsType: Treat * as Data.Kind.Type.
-XStaticPointers: Allow static syntax.
-XStrict: Make bindings in the current module strict by default.
-XStrictData: Treat datatype fields as strict by default.
-XTemplateHaskell: Allow Template Haskell's splice and quotation syntax.
-XTemplateHaskellQuotes: Allow Template Haskell's quotation syntax.
-XTraditionalRecordSyntax: Allow traditional record syntax (e.g. C {f = x}).
-XTransformListComp: Allow generalised list comprehension syntax.
-XTrustworthy: Enable the Safe Haskell Trustworthy mode.
-XTupleSections: Allow use of tuple section synxtax.
-XTypeAbstractions: Allow type abstraction syntax in patterns and type variable binders.
-XTypeApplications: Allow type application syntax in terms and types.
-XTypeData: Allow type data declarations.
-XTypeFamilies: Allow definition of type families.
-XTypeFamilyDependencies: Allow injectivity annotations on type families.
-XTypeInType: Deprecated. Enable kind polymorphism and datatype promotion.
-XTypeOperators: Allow type constructors to be given operator names.
-XTypeSynonymInstances: Allow type synonyms to be mentioned in instance heads.
-XUnboxedSums: Allow the use of unboxed sum syntax.
-XUnboxedTuples: Allow the use of unboxed tuple syntax.
-XUndecidableInstances: Allow definition of instances which may make solving undecidable.
-XUndecidableSuperClasses: Allow all superclass constraints, including those that may result in non-termination of the typechecker.
-XUnicodeSyntax: Enable unicode syntax.
-XUnliftedDatatypes: Allow the definition of unlifted data types.
-XUnliftedFFITypes: Allow the types of foreign imports to contain certain unlifted types.
-XUnliftedNewtypes: Allow definition of unlifted newtypes.
-XUnsafe: Enable Safe Haskell Unsafe mode.
-XViewPatterns: Allow view pattern syntax.

Linking options¶

-c: Stop after generating object (.o) file
-debug: Use the debugging runtime
-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: Build dynamically-linked object files and executables
-dynload: Selects one of a number of modes for finding shared libraries at runtime.
-eventlog: Enable runtime event tracing
-fcompact-unwind: Instruct the linker to produce a __compact_unwind section.
-fkeep-cafs: Do not garbage-collect CAFs (top-level expressions) at runtime
-flink-rts: Link the runtime when generating a shared or static library
-fno-embed-manifest: Do not embed the manifest in the executable (Windows only)
-fno-gen-manifest: Do not generate a manifest file (Windows only)
-fno-shared-implib: Don't generate an import library for a DLL (Windows only)
-framework ⟨name⟩: On Darwin/OS X/iOS only, link in the framework ⟨name⟩. This option corresponds to the -framework option for Apple's Linker.
-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.
-fsplit-sections: Split sections for link-time dead-code stripping
-fuse-rpaths: Set the rpath based on -L flags
-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
-L ⟨dir⟩: Add ⟨dir⟩ to the list of directories searched for libraries
-l ⟨lib⟩: Link in library ⟨lib⟩
-main-is ⟨thing⟩: Set main module and function
-no-hs-main: Don't assume this program contains main
-no-pie: Don't instruct the linker to produce a position-independent executable.
-no-rtsopts-suggestions: Don't print RTS suggestions about linking with -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩].
-package ⟨name⟩: Expose package ⟨pkg⟩
-pie: Instruct the linker to produce a position-independent executable.
-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.
-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, if -rtsopts is not passed); all means that all RTS flags are permitted (the default, if -rtsopts is passed with no argument); 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.
-shared: Generate a shared library (as opposed to an executable)
-single-threaded: Use the single-threaded runtime
-static: Use static Haskell libraries
-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.
-threaded: Use the threaded runtime
-with-rtsopts=⟨opts⟩: Set the default RTS options to ⟨opts⟩.

Miscellaneous options¶

-ddump-mod-cycles: Dump module cycles
-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.
-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.
-fdefer-typed-holes: Convert typed hole errors into warnings, deferring the error until runtime. Implied by -fdefer-type-errors. See also -Wtyped-holes.
-fexternal-interpreter: Run interpreted code in a separate process
-ffamily-application-cache: Use a cache when reducing type family applications
-fglasgow-exts: Deprecated. Enable most language extensions; see Controlling editions and extensions for exactly which ones.
-fno-safe-haskell: Disable Safe Haskell
-ghcversion-file ⟨path to ghcversion.h⟩: (GHC as a C compiler only) Use this ghcversion.h file
-H ⟨size⟩: Set the minimum size of the heap to ⟨size⟩
-hidden-module ⟨module name⟩: A module which should not be visible outside its unit.
-j[⟨n⟩]: When compiling with --make, compile ⟨n⟩ modules in parallel.
-jsem: When compiling with --make, coordinate with other processes through the semaphore ⟨sem⟩ to compile modules in parallel.
-reexported-module ⟨reexport-spec⟩: A module which should be reexported from this unit.
-this-package-name ⟨unit-id⟩: The name of the package which this module would be part of when installed.
-unit @⟨filename⟩: Specify the options to build a specific unit.
-working-dir ⟨dir⟩: Specify the directory a unit is expected to be compiled in.

Modes of operation¶

--frontend ⟨module⟩: run GHC with the given frontend plugin; see Frontend plugins for details.
--help: Display help
--info: display information about the compiler
--interactive: Interactive mode - normally used by just running ghci; see Using GHCi for details.
--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.
--numeric-version: display GHC version (numeric only)
--print-booter-version: display bootstrap compiler version
--print-build-platform: display platform on which GHC was built
--print-c-compiler-flags: C compiler flags used to build GHC
--print-c-compiler-link-flags: C linker flags used to build GHC
--print-debug-on: print whether GHC was built with -DDEBUG
--print-global-package-db: display GHC's global package database directory
--print-have-interpreter: display whether GHC was built with interactive support
--print-have-native-code-generator: display whether target platform has NCG support
--print-host-platform: display host platform of GHC
--print-ld-flags: display linker flags used to compile GHC
--print-leading-underscore: display use of leading underscores on symbol names
--print-libdir: display GHC library directory
--print-object-splitting-supported: display whether GHC supports object splitting
--print-project-git-commit-id: display Git commit id GHC is built from
--print-project-version: display GHC version
--print-rts-ways: display which way RTS was built
--print-stage: display stage number of GHC
--print-support-smp: display whether GHC was compiled with SMP support
--print-tables-next-to-code: display whether GHC was compiled with --enable-tables-next-to-code
--print-target-platform: display target platform of GHC
--print-unregisterised: display whether this GHC was built in unregisterised mode
--run ⟨file⟩: Run a Haskell program.
--show-iface ⟨file⟩: display the contents of an interface file.
--show-options: display the supported command line options
--supported-extensions: display the supported language extensions
--version: display GHC version
-e ⟨expr⟩: Evaluate expr; see Expression evaluation mode for details.
-M: generate dependency information suitable for use in a Makefile; see Dependency generation for details.
-shared: Create a shared object.

Individual optimizations¶

-fasm-shortcutting: Enable shortcutting on assembly. Implied by -O2.
-fbinary-blob-threshold=⟨n⟩: default: 500K. Tweak assembly generator for binary blobs.
-fblock-layout-cfg: Use the new cfg based block layout algorithm. Implied by -O.
-fblock-layout-weightless: Ignore cfg weights for code layout.
-fblock-layout-weights: Sets edge weights used by the new code layout algorithm.
-fcall-arity: Enable call-arity optimisation. Implied by -O.
-fcase-folding: Enable constant folding in case expressions. Implied by -O.
-fcase-merge: Enable case-merging. Implied by -O.
-fcmm-control-flow: Enable control flow optimisation in the Cmm backend. Implied by -O.
-fcmm-elim-common-blocks: Enable Cmm common block elimination. Implied by -O.
-fcmm-sink: Enable Cmm sinking. Implied by -O.
-fcmm-static-pred: Enable static control flow prediction. Implied by -O.
-fcore-constant-folding: Enable constant folding in Core. Implied by -O.
-fcpr-anal: Turn on Constructed Product Result analysis. Implied by -O.
-fcross-module-specialise: Turn on specialisation of overloaded functions imported from other modules. Implied by -O.
-fcse: Enable common sub-expression elimination. Implied by -O.
-fdicts-cheap: Make dictionary-valued expressions seem cheap to the optimiser.
-fdicts-strict: Make dictionaries strict. Implied by -O2.
-fdmd-tx-dict-sel: (deprecated) Use a special demand transformer for dictionary selectors.
-fdmd-unbox-width=⟨n⟩: default: 3. Boxity analysis pretends that returned records with this many fields can be unboxed.
-fdo-clever-arg-eta-expansion: Enable sophisticated argument eta-expansion. Implied by -O2.
-fdo-eta-reduction: Enable eta-reduction. Always enabled by default.
-fdo-lambda-eta-expansion: Enable lambda eta-expansion. Always enabled by default.
-feager-blackholing: Turn on eager blackholing
-fenable-rewrite-rules: Switch on all rewrite rules (including rules generated by automatic specialisation of overloaded functions). Implied by -O.
-fexcess-precision: Enable excess intermediate precision
-fexitification: Enables exitification optimisation. Implied by -O.
-fexpose-all-unfoldings: Expose all unfoldings, even for very large or recursive functions.
-fexpose-overloaded-unfoldings: Expose unfoldings carrying constraints, even for very large or recursive functions.
-ffloat-in: Turn on the float-in transformation. Implied by -O.
-ffull-laziness: Turn on full laziness (floating bindings outwards). Implied by -O.
-ffun-to-thunk: (deprecated) superseded by -ffull-laziness.
-fignore-asserts: Ignore assertions in the source. Implied by -O.
-fignore-interface-pragmas: Ignore pragmas in interface files. Implied by -O0 only.
-finline-generics: Annotate methods of derived Generic and Generic1 instances with INLINE[1] pragmas based on heuristics. Implied by -O.
-finline-generics-aggressively: Annotate methods of all derived Generic and Generic1 instances with INLINE[1] pragmas.
-fkeep-auto-rules: Keep all "auto" rules, generated by specialisation
-flate-dmd-anal: Run demand analysis again, at the end of the simplification pipeline
-flate-specialise: Run a late specialisation pass
-fliberate-case: Turn on the liberate-case transformation. Implied by -O2.
-fliberate-case-threshold=⟨n⟩: default: 2000. Set the size threshold for the liberate-case transformation to ⟨n⟩
-fllvm-pass-vectors-in-regs: (deprecated) Does nothing
-flocal-float-out: Enable local floating definitions out of let-binds.
-flocal-float-out-top-level: Enable local floating to float top-level bindings
-floopification: Turn saturated self-recursive tail-calls into local jumps in the generated assembly. Implied by -O.
-fmax-forced-spec-args=⟨n⟩: default: 333. Maximum number of value arguments for forced SpecConstr specializations.
-fmax-inline-alloc-size=⟨n⟩: default: 128. Set the maximum size of inline array allocations to ⟨n⟩ bytes (default: 128).
-fmax-inline-memcpy-insns=⟨n⟩: default: 32. Inline memcpy calls if they would generate no more than ⟨n⟩ pseudo instructions.
-fmax-inline-memset-insns=⟨n⟩: default: 32. Inline memset calls if they would generate no more than ⟨n⟩ pseudo instructions
-fmax-simplifier-iterations=⟨n⟩: default: 4. Set the max iterations for the simplifier.
-fmax-uncovered-patterns=⟨n⟩: default: 4. Set the maximum number of patterns to display in warnings about non-exhaustive ones.
-fmax-worker-args=⟨n⟩: default: 10. Maximum number of value arguments for a worker.
-fno-opt-coercion: Turn off the coercion optimiser
-fno-pre-inlining: Turn off pre-inlining
-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.
-fobject-determinism: Produce fully deterministic object code
-fomit-interface-pragmas: Don't generate interface pragmas. Implied by -O0 only.
-fomit-yields: Omit heap checks when no allocation is being performed.
-foptimal-applicative-do: Use a slower but better algorithm for ApplicativeDo
-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.
-fpolymorphic-specialisation: Allow specialisation to abstract over free type variables
-fregs-graph: Use the graph colouring register allocator for register allocation in the native code generator.
-fregs-iterative: Use the iterative coalescing graph colouring register allocator in the native code generator.
-fsimpl-tick-factor=⟨n⟩: default: 100. Set the percentage factor for simplifier ticks.
-fsimplifier-phases=⟨n⟩: default: 2. Set the number of phases for the simplifier. Ignored with -O0.
-fsolve-constant-dicts: When solving constraints, try to eagerly solve super classes using available dictionaries. Implied by -O.
-fspec-constr: Turn on the SpecConstr transformation. Implied by -O2.
-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.
-fspec-constr-keen: Specialize a call with an explicit constructor argument, even if the argument is not scrutinised in the body of the function
-fspec-constr-threshold=⟨n⟩: default: 2000. Set the size threshold for the SpecConstr transformation to ⟨n⟩.
-fspecialise: Turn on specialisation of overloaded functions. Implied by -O.
-fspecialise-aggressively: Turn on specialisation of overloaded functions regardless of size, if unfolding is available
-fspecialise-incoherents: Enable specialisation on incoherent instances
-fstatic-argument-transformation: Turn on the static argument transformation.
-fstg-cse: Enable common sub-expression elimination on the STG intermediate language. Implied by -O.
-fstg-lift-lams: Enable late lambda lifting on the STG intermediate language. Implied by -O2.
-fstg-lift-lams-known: Allow turning known into unknown calls while performing late lambda lifting.
-fstg-lift-lams-non-rec-args: Create top-level non-recursive functions with at most <n> parameters while performing late lambda lifting.
-fstg-lift-lams-rec-args: Create top-level recursive functions with at most <n> parameters while performing late lambda lifting.
-fstrictness: Turn on demand analysis. Implied by -O. Implies -fworker-wrapper
-fstrictness-before=⟨n⟩: Run an additional demand analysis before simplifier phase ⟨n⟩
-funbox-small-strict-fields: Flatten strict constructor fields with a pointer-sized representation. Implied by -O.
-funbox-strict-fields: Flatten strict constructor fields
-funfolding-case-scaling=⟨n⟩: default: 30. Apply a penalty of (inlining_cost * 1/n) for each level of case nesting.
-funfolding-case-threshold=⟨n⟩: default: 2. Reduce inlining for cases nested deeper than n.
-funfolding-creation-threshold=⟨n⟩: default: 750. Tweak unfolding settings.
-funfolding-dict-discount=⟨n⟩: default: 30. Tweak unfolding settings.
-funfolding-fun-discount=⟨n⟩: default: 60. Tweak unfolding settings.
-funfolding-keeness-factor=⟨n⟩: This has been deprecated in GHC 9.0.1.
-funfolding-use-threshold=⟨n⟩: default: 90. Tweak unfolding settings.
-fworker-wrapper: Enable the worker/wrapper transformation. Implied by -O and by -fstrictness.
-fworker-wrapper-cbv: Enable w/w splits for wrappers whos sole purpose is evaluating arguments.
-fwrite-if-compression=⟨n⟩: default: 2. Tweak the level of interface file compression.

Optimization levels¶

-O: Enable level 1 optimisations
-O0: Disable optimisations (default)
-O2: Enable level 2 optimisations
-O⟨n⟩: Any -On where n > 2 is the same as -O2.

Package options¶

-clear-package-db: Clear the package db stack.
-distrust ⟨pkg⟩: Expose package ⟨pkg⟩ and set it to be distrusted. See Safe Haskell.
-distrust-all-packages: Distrust all packages by default. See Safe Haskell.
-fpackage-trust: Enable Safe Haskell trusted package requirement for trustworthy modules.
-global-package-db: Add the global package db to the stack.
-hide-all-packages: Hide all packages by default
-hide-package ⟨pkg⟩: Hide package ⟨pkg⟩
-ignore-package ⟨pkg⟩: Ignore package ⟨pkg⟩
-no-auto-link-packages: Don't automatically link in the base and rts packages.
-no-global-package-db: Remove the global package db from the stack.
-no-user-package-db: Remove the user's package db from the stack.
-package ⟨pkg⟩: Expose package ⟨pkg⟩
-package-db ⟨file⟩: Add ⟨file⟩ to the package db stack.
-package-env ⟨file⟩|⟨name⟩: Use the specified package environment.
-package-id ⟨unit-id⟩: Expose package by id ⟨unit-id⟩
-this-unit-id ⟨unit-id⟩: Compile to be part of unit (i.e. package) ⟨unit-id⟩
-trust ⟨pkg⟩: Expose package ⟨pkg⟩ and set it to be trusted. See Safe Haskell.
-user-package-db: Add the user's package db to the stack.

Phases of compilation¶

--merge-objs: Merge a set of objects into a GHCi library.
-C: Stop after generating C (.hc file)
-c: Stop after generating object (.o) file
-E: Stop after preprocessing (.hspp file)
-F: Enable the use of a pre-processor (set with -pgmF ⟨cmd⟩)
-S: Stop after generating assembly (.s file)
-x ⟨suffix⟩: Override default behaviour for source files

Overriding external programs¶

-pgma ⟨cmd⟩: Use ⟨cmd⟩ as the assembler
-pgmc ⟨cmd⟩: Use ⟨cmd⟩ as the C compiler
-pgmCmmP ⟨cmd⟩: Use ⟨cmd⟩ as the C-- C pre-processor
-pgmcxx ⟨cmd⟩: Use ⟨cmd⟩ as the C++ compiler
-pgmF ⟨cmd⟩: Use ⟨cmd⟩ as the pre-processor (with -F only)
-pgmi ⟨cmd⟩: Use ⟨cmd⟩ as the external interpreter command.
-pgminstall_name_tool ⟨cmd⟩: Use ⟨cmd⟩ as the program to inject runpath into mach-o dylibs on macOS
-pgmJSP ⟨cmd⟩: Use ⟨cmd⟩ as the JavaScript C pre-processor (only for javascript-backend)
-pgmL ⟨cmd⟩: Use ⟨cmd⟩ as the literate pre-processor
-pgml ⟨cmd⟩: Use ⟨cmd⟩ as the linker
-pgmlas ⟨cmd⟩: Use ⟨cmd⟩ as the LLVM assembler
-pgmlc ⟨cmd⟩: Use ⟨cmd⟩ as the LLVM compiler
-pgmlm ⟨cmd⟩: Use ⟨cmd⟩ as the linker when merging object files
-pgmlo ⟨cmd⟩: Use ⟨cmd⟩ as the LLVM optimiser
-pgmotool ⟨cmd⟩: Use ⟨cmd⟩ as the program to inspect mach-o dylibs on macOS
-pgmP ⟨cmd⟩: Use ⟨cmd⟩ as the C pre-processor (with -cpp only)
-pgms ⟨cmd⟩: Use ⟨cmd⟩ as the splitter
-pgmwindres ⟨cmd⟩: Use ⟨cmd⟩ as the program for embedding manifests on Windows.

Phase-specific options¶

-opta ⟨option⟩: pass ⟨option⟩ to the assembler
-optc ⟨option⟩: pass ⟨option⟩ to the C compiler
-optCmmP ⟨option⟩: pass ⟨option⟩ to the C-- C pre-processor.
-optcxx ⟨option⟩: pass ⟨option⟩ to the C++ compiler
-optF ⟨option⟩: pass ⟨option⟩ to the custom pre-processor
-opti ⟨option⟩: pass ⟨option⟩ to the interpreter sub-process.
-optJSP ⟨option⟩: pass ⟨option⟩ to JavaScript C pre-processor (only for javascript-backend)
-optL ⟨option⟩: pass ⟨option⟩ to the literate pre-processor
-optl ⟨option⟩: pass ⟨option⟩ to the linker
-optlas ⟨option⟩: pass ⟨option⟩ to the LLVM assembler
-optlc ⟨option⟩: pass ⟨option⟩ to the LLVM compiler
-optlm ⟨option⟩: pass ⟨option⟩ to the linker when merging object files.
-optlo ⟨option⟩: pass ⟨option⟩ to the LLVM optimiser
-optP ⟨option⟩: pass ⟨option⟩ to cpp (with -cpp only)
-optwindres ⟨option⟩: pass ⟨option⟩ to windres.
-pgmc-supports-no-pie: (deprecated) Indicate that the linker supports -no-pie
-pgml-supports-no-pie: Indicate that the linker supports -no-pie

Platform-specific options¶

-mavx: (x86 only) Enable support for AVX SIMD extensions
-mavx2: (x86 only) Enable support for AVX2 SIMD extensions
-mavx512cd: (x86 only) Enable support for AVX512-CD SIMD extensions
-mavx512er: (x86 only) Enable support for AVX512-ER SIMD extensions
-mavx512f: (x86 only) Enable support for AVX512-F SIMD extensions
-mavx512pf: (x86 only) Enable support for AVX512-PF SIMD extensions
-mbmi: (x86 only) Use BMI1 for bit manipulation operations
-mbmi2: (x86 only) Use BMI2 for bit manipulation operations
-mfma: Use native FMA instructions for fused multiply-add floating-point operations
-msse: (x86 only) Use SSE for floating-point operations
-msse2: (x86 only) Use SSE2 for floating-point operations
-msse3: (x86 only) Use SSE3 for floating-point operations
-msse4: (x86 only) Use SSE4 for floating-point operations
-msse4.2: (x86 only) Use SSE4.2 for floating-point operations

Compiler plugins¶

-fclear-plugins: Clear the list of active plugins
-fplugin-library=⟨file-path⟩;⟨unit-id⟩;⟨module⟩;⟨args⟩: Load a pre-compiled static plugin from an external library
-fplugin-opt=⟨module⟩:⟨args⟩: Give arguments to a plugin module; module must be specified with -fplugin=⟨module⟩
-fplugin-trustworthy: Trust the used plugins and no longer mark the compiled module as unsafe
-fplugin=⟨module⟩: Load a plugin exported by a given module
-hide-all-plugin-packages: Hide all packages for plugins by default
-plugin-package ⟨pkg⟩: Expose ⟨pkg⟩ for plugins
-plugin-package-id ⟨pkg-id⟩: Expose ⟨pkg-id⟩ for plugins

Profiling¶

-auto: (deprecated) Alias for -fprof-auto-exported
-auto-all: (deprecated) Alias for -fprof-auto
-caf-all: (deprecated) Alias for -fprof-cafs
-fno-prof-count-entries: Do not collect entry counts
-fprof-auto: Auto-add SCC\ s to all bindings not marked INLINE
-fprof-auto-calls: Auto-add SCC\ s to all call sites
-fprof-auto-exported: Auto-add SCC\ s to all exported bindings not marked INLINE
-fprof-auto-top: Auto-add SCC\ s to all top-level bindings not marked INLINE
-fprof-cafs: Auto-add SCC\ s to all CAFs
-fprof-callers=⟨name⟩: Auto-add SCC\ s to all call-sites of the named function.
-fprof-late: Auto-add SCC\ s to all top level bindings after the core pipeline has run.
-fprof-late-inline: Auto-add SCC\ s to all top level bindings after the optimizer has run and retain them when inlining.
-fprof-late-overloaded: Auto-add SCC\ s to all top level overloaded bindings after the core pipeline has run.
-fprof-late-overloaded-calls: Auto-add SCC\ s to all call sites that include dictionary arguments after the core pipeline has run.
-fprof-manual: Process manual SCC annotations.
-no-auto: (deprecated) Alias for -fno-prof-auto
-no-auto-all: (deprecated) Alias for -fno-prof-auto
-no-caf-all: (deprecated) Alias for -fno-prof-cafs
-prof: Turn on profiling
-ticky: Turn on ticky-ticky profiling
-ticky-allocd: Track the number of times each closure type is allocated.
-ticky-ap-thunk: Don't use standard AP thunks on order to get more reliable entry counters.
-ticky-dyn-thunk: Track allocations of dynamic thunks
-ticky-LNE: Treat join point binders similar to thunks/functions.
-ticky-tag-checks: Emit dummy ticky counters to record how many tag-inference checks tag inference avoided.

Program coverage¶

-fhpc: Turn on Haskell program coverage instrumentation
-hpcdir⟨dir⟩: Set the directory where GHC places .mix files.

Recompilation checking¶

-exclude-module=⟨file⟩: Regard ⟨file⟩ as "stable"; i.e., exclude it from having dependencies on it.
-fforce-recomp: Turn off recompilation checking. This is implied by any -ddump-X option when compiling a single file (i.e. when using -c).
-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.
-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.
-include-cpp-deps: Include preprocessor dependencies
-include-pkg-deps: Regard modules imported from packages as unstable

Redirecting output¶

-dep-makefile ⟨file⟩: Use ⟨file⟩ as the makefile
-dep-suffix ⟨suffix⟩: Make dependencies that declare that files with suffix .⟨suf⟩⟨osuf⟩ depend on interface files with suffix .⟨suf⟩hi
-dumpdir ⟨dir⟩: redirect dump files
-dynhisuf ⟨suffix⟩: set the suffix to use for dynamic interface files
-dyno ⟨file⟩: set dynamic output filename
-dynohi ⟨file⟩: set the filename in which to put the dynamic interface
-dynosuf ⟨suffix⟩: set the dynamic output file suffix
-hcsuf ⟨suffix⟩: set the suffix to use for intermediate C files
-hidir ⟨dir⟩: set directory for interface files
-hiedir ⟨dir⟩: set directory for extended interface files
-hiesuf ⟨suffix⟩: set the suffix to use for extended interface files
-hisuf ⟨suffix⟩: set the suffix to use for interface files
-o ⟨file⟩: set output filename
-odir ⟨dir⟩: set directory for object files
-ohi ⟨file⟩: set the filename in which to put the interface
-osuf ⟨suffix⟩: set the output file suffix
-outputdir ⟨dir⟩: set output directory
-stubdir ⟨dir⟩: redirect FFI stub files

Temporary files¶

-tmpdir ⟨dir⟩: set the directory for temporary files

Verbosity options¶

-fabstract-refinement-hole-fits: default: off. Toggles whether refinements where one or more of the holes are abstract are reported.
-fdefer-diagnostics: Defer and group diagnostic messages by severity
-fdiagnostics-as-json: Output diagnostics in Json format specified by JSON schema
-fdiagnostics-color=⟨always|auto|never⟩: Use colors in error messages
-fdiagnostics-show-caret: Whether to show snippets of original source code
-ferror-spans: Output full span in error messages
-fhide-source-paths: hide module source and object paths
-fkeep-going: Continue compilation as far as possible on errors
-fmax-refinement-hole-fits=⟨n⟩: default: 6. Set the maximum number of refinement hole fits for typed holes to display in type error messages.
-fmax-relevant-binds=⟨n⟩: default: 6. Set the maximum number of bindings to display in type error messages.
-fmax-valid-hole-fits=⟨n⟩: default: 6. Set the maximum number of valid hole fits for typed holes to display in type error messages.
-fno-show-valid-hole-fits: Disables showing a list of valid hole fits for typed holes in type error messages.
-fno-sort-valid-hole-fits: Disables the sorting of the list of valid hole fits for typed holes in type error messages.
-fprint-axiom-incomps: Display equation incompatibilities in closed type families
-fprint-equality-relations: Distinguish between equality relations when printing
-fprint-error-index-links=⟨always|auto|never⟩: Whether to emit diagnostic codes as ANSI hyperlinks to the Haskell Error Index.
-fprint-expanded-synonyms: In type errors, also print type-synonym-expanded types.
-fprint-explicit-coercions: Print coercions in types
-fprint-explicit-foralls: Print explicit forall quantification in types. See also ExplicitForAll
-fprint-explicit-kinds: Print explicit kind foralls and kind arguments in types. See also KindSignatures
-fprint-explicit-runtime-reps: Print RuntimeRep and Levity variables in types which are runtime-representation polymorphic.
-fprint-potential-instances: display all available instances in type error messages
-fprint-redundant-promotion-ticks: Print redundant DataKinds promotion ticks
-fprint-typechecker-elaboration: Print extra information from typechecker.
-fprint-unicode-syntax: Use unicode syntax when printing expressions, types and kinds. See also UnicodeSyntax
-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.
-freverse-errors: Output errors in reverse order
-fshow-docs-of-hole-fits: Toggles whether to show the documentation of the valid hole fits in the output.
-fshow-error-context: Whether to show textual information about error context
-fshow-hole-constraints: Show constraints when reporting typed holes.
-fshow-hole-matches-of-hole-fits: Toggles whether to show the type of the additional holes in refinement hole fits.
-fshow-provenance-of-hole-fits: Toggles whether to show the provenance of the valid hole fits in the output.
-fshow-type-app-of-hole-fits: Toggles whether to show the type application of the valid hole fits in the output.
-fshow-type-app-vars-of-hole-fits: Toggles whether to show what type each quantified variable takes in a valid hole fit.
-fshow-type-of-hole-fits: Toggles whether to show the type of the valid hole fits in the output.
-fsort-by-size-hole-fits: Sort valid hole fits by size.
-fsort-by-subsumption-hole-fits: Sort valid hole fits by subsumption.
-funclutter-valid-hole-fits: Unclutter the list of valid hole fits by not showing provenance nor type applications of suggestions.
-Rghc-timing: Summarise timing stats for GHC (same as +RTS -tstderr).
-v: verbose mode (equivalent to -v3)
-v⟨n⟩: set verbosity level

Warnings¶

-fenable-th-splice-warnings: Generate warnings for Template Haskell splices
-fhelpful-errors: Make suggestions for mis-spelled names.
-fmax-pmcheck-models=⟨n⟩: soft limit on the number of parallel models the pattern match checker should check a pattern match clause against
-fshow-warning-groups: show which group an emitted warning belongs to.
-fvia-C: use the C code generator
-W: enable normal warnings
-w: disable all warnings
-Wall: enable almost all warnings (details in Warnings and sanity-checking)
-Wall-missed-specialisations: warn when specialisation of any overloaded function fails.
-Wall-missed-specializations: alias for -Wall-missed-specialisations
-Wambiguous-fields: warn about ambiguous field selectors or updates
-Wauto-orphans: (deprecated) Does nothing
-Wbadly-staged-types: warn when type binding is used at the wrong TH stage.
-Wcompat: enable future compatibility warnings (details in Warnings and sanity-checking)
-Wcompat-unqualified-imports: (deprecated) Report unqualified imports of core libraries which are expected to cause compatibility problems in future releases.
-Wcpp-undef: warn on uses of the #if directive on undefined identifiers
-Wdata-kinds-tc: warn when an illegal use of a type or kind without DataKinds is caught by the typechecker
-Wdefault: enable default flags
-Wdefaulted-exception-context: warn when an Control.Exception.Context.ExceptionContext implicit parameter is defaulted to Control.Exception.Context.emptyExceptionContext.
-Wdeferred-out-of-scope-variables: Report warnings when variable out-of-scope errors are deferred until runtime. See -fdefer-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.
-Wdeprecated-flags: warn about uses of commandline flags that are deprecated
-Wdeprecated-type-abstractions: warn when type abstractions in constructor patterns are used without enabling TypeApplications
-Wdeprecations: warn about uses of functions & types that have DEPRECATED pragmas, or WARNING pragmas with the deprecated category.
-Wderiving-defaults: warn about default deriving when using both DeriveAnyClass and GeneralizedNewtypeDeriving
-Wderiving-typeable: warn when Typeable is derived
-Wdodgy-exports: warn about dodgy exports
-Wdodgy-foreign-imports: warn about dodgy foreign imports
-Wdodgy-imports: warn about dodgy imports
-Wduplicate-constraints: warn when a constraint appears duplicated in a type signature
-Wduplicate-exports: warn when an entity is exported multiple times
-Wempty-enumerations: warn about enumerations that are empty
-Werror: make warnings fatal
-Weverything: enable all warnings supported by GHC
-Wextended-warnings: warn about uses of functions & types that have WARNING or DEPRECATED pragmas, across all categories
-Wextra: alias for -W
-Wforall-identifier: (deprecated) Does nothing
-Wgadt-mono-local-binds: warn when pattern matching on a GADT without MonoLocalBinds
-Whi-shadowing: (deprecated) warn when a .hi file in the current directory shadows a library
-Widentities: warn about uses of Prelude numeric conversions that are probably the identity (and hence could be omitted)
-Wimplicit-kind-vars: (deprecated) warn when kind variables are implicitly quantified over.
-Wimplicit-lift: warn about implicit lift in Template Haskell quotes
-Wimplicit-prelude: warn when the Prelude is implicitly imported
-Wimplicit-rhs-quantification: warn when type variables on the RHS of a type synonym are implicitly quantified
-Winaccessible-code: warn about inaccessible code
-Wincomplete-export-warnings: warn when some but not all of exports for a name are warned about
-Wincomplete-patterns: warn when a pattern match could fail
-Wincomplete-record-selectors: warn when a record selector application could fail
-Wincomplete-record-updates: warn when a record update could fail
-Wincomplete-uni-patterns: warn when a pattern match in a lambda expression, pattern binding or a lazy pattern could fail
-Winconsistent-flags: warn when command line options are inconsistent in some way.
-Winferred-safe-imports: warn when an explicitly Safe Haskell module imports a Safe-Inferred one
-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.
-Winvalid-haddock: warn when a Haddock comment occurs in an invalid position
-Wloopy-superclass-solve: (deprecated) warn when creating potentially-loopy superclass constraint evidence
-Wmisplaced-pragmas: warn about uses of file header pragmas in the module body
-Wmissed-extra-shared-lib: Warn when GHCi can't load a shared lib.
-Wmissed-specialisations: warn when specialisation of an imported, overloaded function fails.
-Wmissed-specializations: alias for -Wmissed-specialisations
-Wmissing-deriving-strategies: warn when deriving without mentioning a deriving strategy
-Wmissing-export-lists: warn when a module declaration does not explicitly list all exports
-Wmissing-exported-pattern-synonym-signatures: warn about pattern synonyms without signatures, only if they are exported
-Wmissing-exported-signatures: warn about top-level functions without signatures, only if they are exported
-Wmissing-exported-sigs: (deprecated) warn about top-level functions without signatures, only if they are exported. takes precedence over -Wmissing-signatures
-Wmissing-fields: warn when fields of a record are uninitialised
-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.
-Wmissing-import-lists: warn when an import declaration does not explicitly list all the names brought into scope
-Wmissing-kind-signatures: warn when type declarations don't have kind signatures nor CUSKs
-Wmissing-local-signatures: warn about polymorphic local bindings without signatures
-Wmissing-local-sigs: (deprecated) warn about polymorphic local bindings without signatures
-Wmissing-methods: warn when class methods are undefined
-Wmissing-monadfail-instances: (deprecated) Warn when a failable pattern is used in a do-block that does not have a MonadFail instance.
-Wmissing-pattern-synonym-signatures: warn when pattern synonyms do not have type signatures
-Wmissing-poly-kind-signatures: warn when inferred polykinded type or class declaration don't have kind signatures nor CUSKs
-Wmissing-role-annotations: warn when type declarations don't have role annotations
-Wmissing-safe-haskell-mode: warn when the Safe Haskell mode is not explicitly specified.
-Wmissing-signatures: warn about top-level functions without signatures
-Wmissing-space-after-bang: (deprecated) Does nothing
-Wmonomorphism-restriction: warn when the Monomorphism Restriction is applied
-Wname-shadowing: warn when names are shadowed
-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.
-Wnoncanonical-monadfail-instances: (deprecated) warn when Monad or MonadFail instances have noncanonical definitions of fail.
-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.
-Wnot: (deprecated) Alias for -w
-Woperator-whitespace: warn on prefix, suffix, and tight infix uses of infix operators
-Woperator-whitespace-ext-conflict: warn on uses of infix operators that would be parsed differently were a particular GHC extension enabled
-Worphans: warn when the module contains orphan instance declarations or rewrite rules
-Woverflowed-literals: warn about literals that will overflow their type
-Woverlapping-patterns: warn about overlapping patterns
-Wpartial-fields: warn when defining a partial record field.
-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.
-Wprepositive-qualified-module: Report imports with a leading/prepositive "qualified"
-Wredundant-bang-patterns: Warn about redundant bang patterns.
-Wredundant-constraints: Have the compiler warn about redundant constraints in type signatures.
-Wredundant-record-wildcards: Warn about record wildcard matches when the wildcard binds no patterns.
-Wredundant-strictness-flags: Warn about redundant strictness flags.
-Wsafe: warn if the module being compiled is regarded to be safe.
-Wsemigroup: (deprecated) Warn when a Monoid is not Semigroup, and on non-Semigroup definitions of (<>)
-Wsimplifiable-class-constraints: Warn about class constraints in a type signature that can be simplified using a top-level instance declaration.
-Wstar-binder: warn about binding the (*) type operator despite StarIsType
-Wstar-is-type: warn when * is used to mean Data.Kind.Type
-Wtabs: warn if there are tabs in the source file
-Wterm-variable-capture: warn when an implicitly quantified type variable captures a term's name
-Wtrustworthy-safe: warn if the module being compiled is marked as Trustworthy but it could instead be marked as Safe, a more informative bound.
-Wtype-defaults: warn when defaulting happens
-Wtype-equality-out-of-scope: warn when type equality a ~ b is used despite being out of scope
-Wtype-equality-requires-operators: warn when type equality a ~ b is used despite being out of scope
-Wtyped-holes: Report warnings when typed hole errors are deferred until runtime. See -fdefer-typed-holes.
-Wunbanged-strict-patterns: warn on pattern bind of unlifted variable that is neither bare nor banged
-Wunicode-bidirectional-format-characters: warn about the usage of unicode bidirectional layout override characters
-Wunrecognised-pragmas: warn about uses of pragmas that GHC doesn't recognise
-Wunrecognised-warning-flags: throw a warning when an unrecognised -W... flag is encountered on the command line.
-Wunsafe: warn if the module being compiled is regarded to be unsafe. See Safe Haskell
-Wunsupported-calling-conventions: warn about use of an unsupported calling convention
-Wunsupported-llvm-version: Warn when using -fllvm with an unsupported version of LLVM.
-Wunticked-promoted-constructors: warn if promoted constructors are not ticked
-Wunused-binds: warn about bindings that are unused. Alias for -Wunused-top-binds, -Wunused-local-binds and -Wunused-pattern-binds
-Wunused-do-bind: warn about do bindings that appear to throw away values of types other than ()
-Wunused-foralls: warn about type variables in user-written forall\s that are unused
-Wunused-imports: warn about unnecessary imports
-Wunused-local-binds: warn about local bindings that are unused
-Wunused-matches: warn about variables in patterns that aren't used
-Wunused-packages: warn when package is requested on command line, but not needed.
-Wunused-pattern-binds: warn about pattern match bindings that are unused
-Wunused-record-wildcards: Warn about record wildcard matches when none of the bound variables are used.
-Wunused-top-binds: warn about top-level bindings that are unused
-Wunused-type-patterns: warn about unused type variables which arise from patterns in in type family and data family instances
-Wview-pattern-signatures: warn when a view pattern is used with type signature without explicit parens
-Wwarn: make warnings non-fatal
-Wwarnings-deprecations: warn about uses of functions & types that have DEPRECATED pragmas, or WARNING pragmas with the deprecated category. Alias for -Wdeprecations.
-Wwrong-do-bind: warn about do bindings that appear to throw away monadic values that you should have bound instead
-Wx-⟨category⟩: warn about uses of functions & types that have WARNING pragmas with the given category