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GHC(1) Glasgow Haskell Compiler GHC(1)

NAME

ghc - the Glasgow Haskell Compiler

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; see below.

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 -fbyte-code -fexternal-dynamic-refs -fllvm -fno-code -fobject-code -fPIC -fPIE -fwrite-interface
Debugging the compiler
-dcmm-lint -dcore-lint -ddump-asm -ddump-asm-expanded -ddump-asm-liveness -ddump-asm-native -ddump-asm-regalloc -ddump-asm-regalloc-stages -ddump-asm-stats -ddump-bcos -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-proc -ddump-cmm-procmap -ddump-cmm-raw -ddump-cmm-sink -ddump-cmm-sp -ddump-cmm-split -ddump-cmm-switch -ddump-cmm-verbose -ddump-core-stats -ddump-cse -ddump-deriv -ddump-ds -ddump-ds-preopt -ddump-ec-trace -ddump-file-prefix=⟨str⟩ -ddump-foreign -ddump-hpc -ddump-if-trace -ddump-inlinings -ddump-json -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-spec -ddump-splices -ddump-stg -ddump-str-signatures -ddump-stranal -ddump-tc -ddump-tc-ast -ddump-tc-trace -ddump-ticked -ddump-timings -ddump-to-file -ddump-types -ddump-worker-wrapper -dfaststring-stats -dhex-word-literals -dinitial-unique=⟨s⟩ -dinline-check=⟨str⟩ -dno-debug-output -dppr-case-as-let -dppr-cols=⟨n⟩ -dppr-debug -dppr-user-length -drule-check=⟨str⟩ -dshow-passes -dstg-lint -dsuppress-all -dsuppress-coercions -dsuppress-idinfo -dsuppress-module-prefixes -dsuppress-stg-free-vars -dsuppress-ticks -dsuppress-timestamps -dsuppress-type-applications -dsuppress-type-signatures -dsuppress-unfoldings -dsuppress-uniques -dsuppress-var-kinds -dth-dec-file -dunique-increment=⟨i⟩ -dverbose-core2core -dverbose-stg2stg -falignment-sanitisation -fcatch-bottoms -fllvm-fill-undef-with-garbage -fproc-alignment -g -g⟨n⟩
C pre-processor
-cpp -D⟨symbol⟩[=⟨value⟩] -I⟨dir⟩ -U⟨symbol⟩
Finding imports
-i -i⟨dir⟩[:⟨dir⟩]*
Interactive mode
-fbreak-on-error -fbreak-on-exception -fghci-hist-size=⟨n⟩ -fghci-leak-check -flocal-ghci-history -fno-it -fprint-bind-result -fshow-loaded-modules -ghci-script -ignore-dot-ghci -interactive-print ⟨expr⟩
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 -keep-hscpp-file -keep-hscpp-files -keep-llvm-file -keep-llvm-files -keep-o-files -keep-s-file -keep-s-files -keep-tmp-files
Language options
-fno-safe-haskell -fsort-by-size-hole-fits -fsort-by-subsumption-hole-fits -XAllowAmbiguousTypes -XApplicativeDo -XArrows -XBangPatterns -XBinaryLiterals -XBlockArguments -XCApiFFI -XConstrainedClassMethods -XConstraintKinds -XCPP -XDataKinds -XDatatypeContexts -XDefaultSignatures -XDeriveAnyClass -XDeriveDataTypeable -XDeriveFoldable -XDeriveFunctor -XDeriveGeneric -XDeriveLift -XDeriveTraversable -XDerivingStrategies -XDerivingVia -XDisambiguateRecordFields -XDuplicateRecordFields -XEmptyCase -XEmptyDataDecls -XEmptyDataDeriving -XExistentialQuantification -XExplicitForAll -XExplicitNamespaces -XExtendedDefaultRules -XFlexibleContexts -XFlexibleInstances -XForeignFunctionInterface -XFunctionalDependencies -XGADTs -XGADTSyntax -XGeneralisedNewtypeDeriving -XGeneralizedNewtypeDeriving -XHexFloatLiterals -XImplicitParams -XImpredicativeTypes -XIncoherentInstances -XInstanceSigs -XInterruptibleFFI -XKindSignatures -XLambdaCase -XLiberalTypeSynonyms -XMagicHash -XMonadComprehensions -XMonadFailDesugaring -XMonoLocalBinds -XMultiParamTypeClasses -XMultiWayIf -XNamedFieldPuns -XNamedWildCards -XNegativeLiterals -XNoImplicitPrelude -XNoMonomorphismRestriction -XNoPatternGuards -XNoTraditionalRecordSyntax -XNPlusKPatterns -XNullaryTypeClasses -XNumDecimals -XNumericUnderscores -XOverlappingInstances -XOverloadedLabels -XOverloadedLists -XOverloadedStrings -XPackageImports -XParallelListComp -XPartialTypeSignatures -XPatternSynonyms -XPolyKinds -XPostfixOperators -XQuantifiedConstraints -XQuasiQuotes -XRank2Types -XRankNTypes -XRebindableSyntax -XRecordWildCards -XRecursiveDo -XRoleAnnotations -XSafe -XScopedTypeVariables -XStandaloneDeriving -XStarIsType -XStaticPointers -XStrict -XStrictData -XTemplateHaskell -XTemplateHaskellQuotes -XTransformListComp -XTrustworthy -XTupleSections -XTypeApplications -XTypeFamilies -XTypeFamilyDependencies -XTypeInType -XTypeOperators -XTypeSynonymInstances -XUnboxedSums -XUnboxedTuples -XUndecidableInstances -XUndecidableSuperClasses -XUnicodeSyntax -XUnsafe -XViewPatterns
Linking options
-c -debug -dylib-install-name ⟨path⟩ -dynamic -dynload -eventlog -fno-embed-manifest -fno-gen-manifest -fno-shared-implib -framework ⟨name⟩ -framework-path ⟨dir⟩ -fwhole-archive-hs-libs -keep-cafs -L ⟨dir⟩ -l ⟨lib⟩ -main-is ⟨thing⟩ -no-hs-main -no-rtsopts-suggestions -package ⟨name⟩ -pie -rdynamic -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩] -shared -split-objs -split-sections -static -staticlib -threaded -with-rtsopts=⟨opts⟩
Miscellaneous options
-fexternal-interpreter -fglasgow-exts -ghcversion-file ⟨path to ghcversion.h⟩ -H ⟨size⟩ -j[⟨n⟩]
Modes of operation
--frontend ⟨module⟩ --help -? --info --interactive --make --mk-dll --numeric-version --print-libdir --show-iface ⟨file⟩ --show-options --supported-extensions --supported-languages --version -V -e ⟨expr⟩ -M
Individual optimizations
-fasm-shortcutting -fblock-layout-cfg -fblock-layout-weightless -fblock-layout-weights -fcall-arity -fcase-folding -fcase-merge -fcmm-elim-common-blocks -fcmm-sink -fcpr-anal -fcross-module-specialise -fcse -fdicts-cheap -fdicts-strict -fdmd-tx-dict-sel -fdo-eta-reduction -fdo-lambda-eta-expansion -feager-blackholing -fenable-rewrite-rules -fexcess-precision -fexitification -fexpose-all-unfoldings -ffloat-in -ffull-laziness -ffun-to-thunk -fignore-asserts -fignore-interface-pragmas -flate-dmd-anal -flate-specialise -fliberate-case -fliberate-case-threshold=⟨n⟩ -fllvm-pass-vectors-in-regs -floopification -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 -fomit-interface-pragmas -fomit-yields -foptimal-applicative-do -fpedantic-bottoms -fregs-graph -fregs-iterative -fsimpl-tick-factor=⟨n⟩ -fsimplifier-phases=⟨n⟩ -fsolve-constant-dicts -fspec-constr -fspec-constr-count=⟨n⟩ -fspec-constr-keen -fspec-constr-threshold=⟨n⟩ -fspecialise -fspecialise-aggressively -fstatic-argument-transformation -fstg-cse -fstg-lift-lams -fstg-lift-lams-known -fstg-lift-lams-non-rec-args -fstg-lift-lams-rec-args -fstrictness -fstrictness-before=⟨n⟩ -funbox-small-strict-fields -funbox-strict-fields -funfolding-creation-threshold=⟨n⟩ -funfolding-dict-discount=⟨n⟩ -funfolding-fun-discount=⟨n⟩ -funfolding-keeness-factor=⟨n⟩ -funfolding-use-threshold=⟨n⟩
Optimization levels
-O -O1 -O0 -O2
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
-C -c -E -F -S -x ⟨suffix⟩
Overriding external programs
-pgma ⟨cmd⟩ -pgmc ⟨cmd⟩ -pgmdll ⟨cmd⟩ -pgmF ⟨cmd⟩ -pgmi ⟨cmd⟩ -pgmL ⟨cmd⟩ -pgml ⟨cmd⟩ -pgmlc ⟨cmd⟩ -pgmlibtool ⟨cmd⟩ -pgmlo ⟨cmd⟩ -pgmP ⟨cmd⟩ -pgms ⟨cmd⟩ -pgmwindres ⟨cmd⟩
Phase-specific options
-opta ⟨option⟩ -optc ⟨option⟩ -optdll ⟨option⟩ -optF ⟨option⟩ -opti ⟨option⟩ -optL ⟨option⟩ -optl ⟨option⟩ -optlc ⟨option⟩ -optlo ⟨option⟩ -optP ⟨option⟩ -optwindres ⟨option⟩
Platform-specific options
-msse2 -msse4.2
Compiler plugins
-fclear-plugins -fplugin-opt=⟨module⟩:⟨args⟩ -fplugin=⟨module⟩ -hide-all-plugin-packages -plugin-package ⟨pkg⟩ -plugin-package-id ⟨pkg-id⟩
Profiling
-fno-prof-auto -fno-prof-cafs -fno-prof-count-entries -fprof-auto -fprof-auto-calls -fprof-auto-exported -fprof-auto-top -fprof-cafs -prof -ticky
Program coverage
-fhpc
Recompilation checking
-fforce-recomp -fignore-hpc-changes -fignore-optim-changes
Redirecting output
--exclude-module=⟨file⟩ -ddump-mod-cycles -dep-makefile ⟨file⟩ -dep-suffix ⟨suffix⟩ -dumpdir ⟨dir⟩ -hcsuf ⟨suffix⟩ -hidir ⟨dir⟩ -hiedir ⟨dir⟩ -hiesuf ⟨suffix⟩ -hisuf ⟨suffix⟩ -include-pkg-deps -o ⟨file⟩ -odir ⟨dir⟩ -ohi ⟨file⟩ -osuf ⟨suffix⟩ -outputdir ⟨dir⟩ -stubdir ⟨dir⟩
Temporary files
-tmpdir ⟨dir⟩
Verbosity options
-fabstract-refinement-hole-fits -fdiagnostics-color=⟨always|auto|never⟩ -fdiagnostics-show-caret -ferror-spans -fhide-source-paths -fmax-refinement-hole-fits=⟨n⟩ -fmax-relevant-binds=⟨n⟩ -fmax-valid-hole-fits=⟨n⟩ -fno-show-valid-hole-fits -fno-sort-valid-hole-fits -fprint-equality-relations -fprint-expanded-synonyms -fprint-explicit-coercions -fprint-explicit-foralls -fprint-explicit-kinds -fprint-explicit-runtime-reps -fprint-explicit-runtime-reps -fprint-potential-instances -fprint-typechecker-elaboration -fprint-unicode-syntax -frefinement-level-hole-fits=⟨n⟩ -freverse-errors -fshow-docs-of-hole-fits -fshow-hole-constraints -fshow-hole-matches-of-hole-fits -fshow-provenance-of-hole-fits -fshow-type-app-of-hole-fits -fshow-type-app-vars-of-hole-fits -fshow-type-of-hole-fits -funclutter-valid-hole-fits -Rghc-timing -v -v⟨n⟩
Warnings
-fdefer-out-of-scope-variables -fdefer-type-errors -fdefer-typed-holes -fhelpful-errors -fmax-pmcheck-iterations=⟨n⟩ -fshow-warning-groups -W -w -Wall -Wall-missed-specialisations -Wcompat -Wcpp-undef -Wdeferred-out-of-scope-variables -Wdeferred-type-errors -Wdeprecated-flags -Wdeprecations -Wdodgy-exports -Wdodgy-foreign-imports -Wdodgy-imports -Wduplicate-constraints -Wduplicate-exports -Wempty-enumerations -Werror -Weverything -Whi-shadowing -Widentities -Wimplicit-kind-vars -Wimplicit-prelude -Winaccessible-code -Wincomplete-patterns -Wincomplete-record-updates -Wincomplete-uni-patterns -Winline-rule-shadowing -Wmissed-extra-shared-lib -Wmissed-specialisations -Wmissing-deriving-strategies -Wmissing-export-lists -Wmissing-exported-signatures -Wmissing-exported-sigs -Wmissing-fields -Wmissing-home-modules -Wmissing-import-lists -Wmissing-local-signatures -Wmissing-local-sigs -Wmissing-methods -Wmissing-monadfail-instances -Wmissing-pattern-synonym-signatures -Wmissing-signatures -Wmonomorphism-restriction -Wname-shadowing -Wno-compat -Wnoncanonical-monad-instances -Wnoncanonical-monadfail-instances -Wnoncanonical-monoid-instances -Worphans -Woverflowed-literals -Woverlapping-patterns -Wpartial-fields -Wpartial-type-signatures -Wredundant-constraints -Wsafe -Wsemigroup -Wsimplifiable-class-constraints -Wspace-after-bang -Wstar-binder -Wstar-is-type -Wtabs -Wtrustworthy-safe -Wtype-defaults -Wtyped-holes -Wunbanged-strict-patterns -Wunrecognised-pragmas -Wunrecognised-warning-flags -Wunsafe -Wunsupported-calling-conventions -Wunsupported-llvm-version -Wunticked-promoted-constructors -Wunused-binds -Wunused-do-bind -Wunused-foralls -Wunused-imports -Wunused-local-binds -Wunused-matches -Wunused-pattern-binds -Wunused-top-binds -Wunused-type-patterns -Wwarn -Wwarnings-deprecations -Wwrong-do-bind

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
-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)
-fwrite-interface
Always write interface files

Debugging the compiler

-dcmm-lint
C-\- pass sanity checking
-dcore-lint
Turn on internal sanity checking
-ddump-asm
Dump final assembly
-ddump-asm-expanded
Dump the result of the synthetic instruction expansion pass.
-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-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-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-verbose
Show output from main C-\- pipeline passes
-ddump-core-stats
Print a one-line summary of the size of the Core program at the end of the optimisation pipeline
-ddump-cse
Dump CSE output
-ddump-deriv
Dump deriving output
-ddump-ds
Dump desugarer output.
-ddump-ec-trace
Trace exhaustiveness checker
-ddump-file-prefix=⟨str⟩
Set the prefix of the filenames used for debugging output.
-ddump-foreign
Dump foreign export stubs
-ddump-hpc
An alias for -ddump-ticked.
-ddump-if-trace
Trace interface files
-ddump-inlinings
Dump inlining info
-ddump-json
Dump error messages as JSON documents
-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-spec
Dump specialiser output
-ddump-splices
Dump TH spliced expressions, and what they evaluate to
-ddump-stg
Dump final STG
-ddump-str-signatures
Dump strictness signatures
-ddump-stranal
Dump strictness analyser output
-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 (hpc).
-ddump-timings
Dump per-pass timing and allocation statistics
-ddump-to-file
Dump to files instead of stdout
-ddump-types
Dump type signatures
-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
-dno-debug-output
Suppress unsolicited debugging output
-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-coercions
Suppress the printing of coercions in Core dumps to make them shorter
-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-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
-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-bottoms
Insert error expressions after bottoming expressions; useful when debugging the compiler.
-fllvm-fill-undef-with-garbage
Intruct LLVM to fill dead STG registers with garbage
-fproc-alignment
Align functions at given boundary.
-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
-fghci-hist-size=⟨n⟩
Set the number of entries GHCi keeps for :history. See ghci-debugger.
-fghci-leak-check
(Debugging only) check for space leaks when loading new modules in GHCi.
-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
-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 ⟨expr⟩
Select the function to use for printing evaluated expressions in GHCi

Interface files

--show-iface ⟨file⟩
See modes.
-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

-fno-safe-haskell
Disable Safe Haskell
-fsort-by-size-hole-fits
Sort valid hole fits by size.
-fsort-by-subsumption-hole-fits
Sort valid hole fits by subsumption.
-XAllowAmbiguousTypes
Allow the user to write ambiguous types, and the type inference engine to infer them.
-XApplicativeDo
Enable Applicative do-notation desugaring
-XArrows
Enable arrow notation extension
-XBangPatterns
Enable bang patterns.
-XBinaryLiterals
Enable support for binary literals.
-XBlockArguments
Allow do blocks and other constructs as function arguments.
-XCApiFFI
Enable the CAPI calling convention.
-XConstrainedClassMethods
Enable constrained class methods.
-XConstraintKinds
Enable a kind of constraints.
-XCPP
Enable the C preprocessor.
-XDataKinds
Enable datatype promotion.
-XDatatypeContexts
Allow contexts on data types.
-XDefaultSignatures
Enable default signatures.
-XDeriveAnyClass
Enable deriving for any class.
-XDeriveDataTypeable
Enable deriving for the Data class. Implied by (deprecated) AutoDeriveTypeable.
-XDeriveFoldable
Enable deriving for the Foldable class. Implied by DeriveTraversable.
-XDeriveFunctor
Enable deriving for the Functor class. Implied by DeriveTraversable.
-XDeriveGeneric
Enable deriving for the Generic class.
-XDeriveLift
Enable deriving for the Lift class
-XDeriveTraversable
Enable deriving for the Traversable class. Implies DeriveFunctor and DeriveFoldable.
-XDerivingStrategies
Enables deriving strategies.
-XDerivingVia
Enable deriving instances via types of the same runtime representation. Implies DerivingStrategies.
-XDisambiguateRecordFields
Enable record field disambiguation. Implied by RecordWildCards.
-XDuplicateRecordFields
Allow definition of record types with identically-named fields.
-XEmptyCase
Allow empty case alternatives.
-XEmptyDataDecls
Allow definition of empty data types.
-XEmptyDataDeriving
Allow deriving instances of standard type classes for empty data types.
-XExistentialQuantification
Enable liberalised type synonyms.
-XExplicitForAll
Enable explicit universal quantification. Implied by ScopedTypeVariables, LiberalTypeSynonyms, RankNTypes and ExistentialQuantification.
-XExplicitNamespaces
Enable using the keyword type to specify the namespace of entries in imports and exports (explicit-namespaces). Implied by TypeOperators and TypeFamilies.
-XExtendedDefaultRules
Use GHCi's extended default rules in a normal module.
-XFlexibleContexts
Enable flexible contexts. Implied by ImplicitParams.
-XFlexibleInstances
Enable flexible instances. Implies TypeSynonymInstances. Implied by ImplicitParams.
-XForeignFunctionInterface
Enable foreign function interface.
-XFunctionalDependencies
Enable functional dependencies. Implies MultiParamTypeClasses.
-XGADTs
Enable generalised algebraic data types. Implies GADTSyntax and MonoLocalBinds.
-XGADTSyntax
Enable generalised algebraic data type syntax.
-XGeneralisedNewtypeDeriving
Enable newtype deriving.
-XGeneralizedNewtypeDeriving
Enable newtype deriving.
-XHexFloatLiterals
Enable support for hexadecimal floating point literals.
-XImplicitParams
Enable Implicit Parameters. Implies FlexibleContexts and FlexibleInstances.
-XImpredicativeTypes
Enable impredicative types. Implies RankNTypes.
-XIncoherentInstances
Enable incoherent instances. Implies OverlappingInstances.
-XInstanceSigs
Enable instance signatures.
-XInterruptibleFFI
Enable interruptible FFI.
-XKindSignatures
Enable kind signatures. Implied by TypeFamilies and PolyKinds.
-XLambdaCase
Enable lambda-case expressions.
-XLiberalTypeSynonyms
Enable liberalised type synonyms.
-XMagicHash
Allow # as a postfix modifier on identifiers.
-XMonadComprehensions
Enable monad comprehensions.
-XMonadFailDesugaring
Enable monadfail desugaring.
-XMonoLocalBinds
Enable do not generalise local bindings. Implied by TypeFamilies and GADTs.
-XMultiParamTypeClasses
Enable multi parameter type classes. Implied by FunctionalDependencies.
-XMultiWayIf
Enable multi-way if-expressions.
-XNamedFieldPuns
Enable record puns.
-XNamedWildCards
Enable named wildcards.
-XNegativeLiterals
Enable support for negative literals.
-XNoImplicitPrelude
Don't implicitly import Prelude. Implied by RebindableSyntax.
-XNoMonomorphismRestriction
Disable the monomorphism restriction.
-XNoPatternGuards
Disable pattern guards. Implied by Haskell98.
-XNoTraditionalRecordSyntax
Disable support for traditional record syntax (as supported by Haskell 98) C {f = x}
-XNPlusKPatterns
Enable support for n+k patterns. Implied by Haskell98.
-XNullaryTypeClasses
Deprecated, does nothing. nullary (no parameter) type classes are now enabled using MultiParamTypeClasses.
-XNumDecimals
Enable support for 'fractional' integer literals.
-XNumericUnderscores
Enable support for numeric underscores.
-XOverlappingInstances
Enable overlapping instances.
-XOverloadedLabels
Enable overloaded labels.
-XOverloadedLists
Enable overloaded lists.
-XOverloadedStrings
Enable overloaded string literals.
-XPackageImports
Enable package-qualified imports.
-XParallelListComp
Enable parallel list comprehensions.
-XPartialTypeSignatures
Enable partial type signatures.
-XPatternSynonyms
Enable pattern synonyms.
-XPolyKinds
Enable kind polymorphism. Implies KindSignatures.
-XPostfixOperators
Enable postfix operators.
-XQuantifiedConstraints
Allow forall quantifiers in constraints.
-XQuasiQuotes
Enable quasiquotation.
-XRank2Types
Enable rank-2 types. Synonym for RankNTypes.
-XRankNTypes
Enable rank-N types. Implied by ImpredicativeTypes.
-XRebindableSyntax
Employ rebindable syntax. Implies NoImplicitPrelude.
-XRecordWildCards
Enable record wildcards. Implies DisambiguateRecordFields.
-XRecursiveDo
Enable recursive do (mdo) notation.
-XRoleAnnotations
Enable role annotations.
-XSafe
Enable the Safe Haskell Safe mode.
-XScopedTypeVariables
Enable lexically-scoped type variables.
-XStandaloneDeriving
Enable standalone deriving.
-XStarIsType
Treat * as Data.Kind.Type.
-XStaticPointers
Enable static pointers.
-XStrict
Make bindings in the current module strict by default.
-XStrictData
Enable default strict datatype fields.
-XTemplateHaskell
Enable Template Haskell.
-XTemplateHaskellQuotes
Enable quotation subset of Template Haskell.
-XTransformListComp
Enable generalised list comprehensions.
-XTrustworthy
Enable the Safe Haskell Trustworthy mode.
-XTupleSections
Enable tuple sections.
-XTypeApplications
Enable type application syntax in terms and types.
-XTypeFamilies
Enable type families. Implies ExplicitNamespaces, KindSignatures, and MonoLocalBinds.
-XTypeFamilyDependencies
Enable injective type families. Implies TypeFamilies.
-XTypeInType
Deprecated. Enable kind polymorphism and datatype promotion.
-XTypeOperators
Enable type operators. Implies ExplicitNamespaces.
-XTypeSynonymInstances
Enable type synonyms in instance heads. Implied by FlexibleInstances.
-XUnboxedSums
Enable unboxed sums.
-XUnboxedTuples
Enable the use of unboxed tuple syntax.
-XUndecidableInstances
Enable undecidable instances.
-XUndecidableSuperClasses
Allow all superclass constraints, including those that may result in non-termination of the typechecker.
-XUnicodeSyntax
Enable unicode syntax.
-XUnsafe
Enable Safe Haskell Unsafe mode.
-XViewPatterns
Enable view patterns.

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
-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.
-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
-keep-cafs
Do not garbage-collect CAFs (top-level expressions) at runtime
-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-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); 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.
-shared
Generate a shared library (as opposed to an executable)
-split-objs
Split objects (for libraries)
-split-sections
Split sections for link-time dead-code stripping
-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

-fexternal-interpreter
Run interpreted code in a separate process
-fglasgow-exts
Deprecated. Enable most language extensions; see options-language for exactly which ones.
-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⟩
-j[⟨n⟩]
When compiling with --make, compile ⟨n⟩ modules in parallel.

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 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 make-mode for details.
--mk-dll
DLL-creation mode (Windows only)
--numeric-version
display GHC version (numeric only)
--print-libdir
display GHC library directory
--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 eval-mode for details.
-M
generate dependency information suitable for use in a Makefile; see makefile-dependencies for details.

Individual optimizations

-fasm-shortcutting
Enable shortcutting on assembly. Implied by -O2.
-fblock-layout-cfg
Use the new cfg based block layout algorithm.
-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-elim-common-blocks
Enable Cmm common block elimination. Implied by -O.
-fcmm-sink
Enable Cmm sinking. Implied by -O.
-fcpr-anal
Turn on CPR analysis in the demand analyser. Implied by -O.
-fcross-module-specialise
Turn on specialisation of overloaded functions imported from other modules.
-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
-fdmd-tx-dict-sel
Use a special demand transformer for dictionary selectors. Always enabled by default.
-fdo-eta-reduction
Enable eta-reduction. Implied by -O.
-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.
-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
Allow worker-wrapper to convert a function closure into a thunk if the function does not use any of its arguments. Off by default.
-fignore-asserts
Ignore assertions in the source. Implied by -O.
-fignore-interface-pragmas
Ignore pragmas in interface files. Implied by -O0 only.
-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
Pass vector value in vector registers for function calls
-floopification
Turn saturated self-recursive tail-calls into local jumps in the generated assembly. Implied by -O.
-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. If a worker has that many arguments, none will be unpacked anymore.
-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.
-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.
-fregs-graph
Use the graph colouring register allocator for register allocation in the native code generator. Implied by -O2.
-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.
-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
-fstatic-argument-transformation
Turn on the static argument transformation.
-fstg-cse
Enable common sub-expression elimination on the STG intermediate language
-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 strictness analysis. Implied by -O. Implies -fworker-wrapper
-fstrictness-before=⟨n⟩
Run an additional strictness 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-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⟩
default: 1.5. Tweak unfolding settings.
-funfolding-use-threshold=⟨n⟩
default: 60. Tweak unfolding settings.

Optimization levels

-O
Enable level 1 optimisations
-O0
Disable optimisations (default)
-O2
Enable level 2 optimisations

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

-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
-pgmdll ⟨cmd⟩
Use ⟨cmd⟩ as the DLL generator
-pgmF ⟨cmd⟩
Use ⟨cmd⟩ as the pre-processor (with -F only)
-pgmi ⟨cmd⟩
Use ⟨cmd⟩ as the external interpreter command.
-pgmL ⟨cmd⟩
Use ⟨cmd⟩ as the literate pre-processor
-pgml ⟨cmd⟩
Use ⟨cmd⟩ as the linker
-pgmlc ⟨cmd⟩
Use ⟨cmd⟩ as the LLVM compiler
-pgmlibtool ⟨cmd⟩
Use ⟨cmd⟩ as the command for libtool (with -staticlib only).
-pgmlo ⟨cmd⟩
Use ⟨cmd⟩ as the LLVM optimiser
-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
-optdll ⟨option⟩
pass ⟨option⟩ to the DLL generator
-optF ⟨option⟩
pass ⟨option⟩ to the custom pre-processor
-opti ⟨option⟩
pass ⟨option⟩ to the interpreter sub-process.
-optL ⟨option⟩
pass ⟨option⟩ to the literate pre-processor
-optl ⟨option⟩
pass ⟨option⟩ to the linker
-optlc ⟨option⟩
pass ⟨option⟩ to the LLVM compiler
-optlo ⟨option⟩
pass ⟨option⟩ to the LLVM optimiser
-optP ⟨option⟩
pass ⟨option⟩ to cpp (with -cpp only)
-optwindres ⟨option⟩
pass ⟨option⟩ to windres.

Platform-specific options

-msse2
(x86 only) Use SSE2 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-opt=⟨module⟩:⟨args⟩
Give arguments to a plugin module; module must be specified with -fplugin=⟨module⟩
-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

-fno-prof-auto
Disables any previous -fprof-auto, -fprof-auto-top, or -fprof-auto-exported options.
-fno-prof-cafs
Disables any previous -fprof-cafs option.
-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
-prof
Turn on profiling
-ticky
Turn on ticky-ticky profiling

Program coverage

-fhpc
Turn on Haskell program coverage instrumentation

Recompilation checking

-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.

Redirecting output

--exclude-module=⟨file⟩
Regard ⟨file⟩ as "stable"; i.e., exclude it from having dependencies on it.
-ddump-mod-cycles
Dump module cycles
-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
-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
-include-pkg-deps
Regard modules imported from packages as unstable
-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.
-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
-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-equality-relations
Distinguish between equality relations when printing
-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 -XExplicitForAll
-fprint-explicit-kinds
Print explicit kind foralls and kind arguments in types. See also -XKindSignatures
-fprint-explicit-runtime-reps
Print RuntimeRep variables in types which are runtime-representation polymorphic.
-fprint-explicit-runtime-reps
Print RuntimeRep variables in types which are runtime-representation polymorphic.
-fprint-potential-instances
display all available instances in type error messages
-fprint-typechecker-elaboration
Print extra information from typechecker.
-fprint-unicode-syntax
Use unicode syntax when printing expressions, types and kinds. See also -XUnicodeSyntax
-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-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.
-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

-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.
-fhelpful-errors
Make suggestions for mis-spelled names.
-fmax-pmcheck-iterations=⟨n⟩
the iteration limit for the pattern match checker
-fshow-warning-groups
show which group an emitted warning belongs to.
-W
enable normal warnings
-w
disable all warnings
-Wall
enable almost all warnings (details in options-sanity)
-Wall-missed-specialisations
warn when specialisation of any overloaded function fails.
-Wcompat
enable future compatibility warnings (details in options-sanity)
-Wcpp-undef
warn on uses of the #if directive on undefined identifiers
-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
-Wdeprecations
warn about uses of functions & types that have warnings or deprecated pragmas. Alias for -Wwarnings-deprecations
-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
-Whi-shadowing
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
warn when kind variables are brought into scope implicitly despite the "forall-or-nothing" rule
-Wimplicit-prelude
warn when the Prelude is implicitly imported
-Winaccessible-code
warn about inaccessible code
-Wincomplete-patterns
warn when a pattern match could fail
-Wincomplete-record-updates
warn when a record update could fail
-Wincomplete-uni-patterns
warn when a pattern match in a lambda expression or pattern binding could fail
-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 rules-inline.
-Wmissed-extra-shared-lib
Warn when GHCi can't load a shared lib.
-Wmissed-specialisations
warn when specialisation of an imported, overloaded function fails.
-Wmissing-deriving-strategies
warn when a deriving clause is missing a deriving strategy
-Wmissing-export-lists
warn when a module declaration does not explicitly list all exports
-Wmissing-exported-signatures
warn about top-level functions without signatures, only if they are exported. takes precedence over -Wmissing-signatures
-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-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
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-signatures
warn about top-level functions without signatures
-Wmonomorphism-restriction
warn when the Monomorphism Restriction is applied
-Wname-shadowing
warn when names are shadowed
-Wno-compat
Disables all warnings enabled by -Wcompat.
-Wnoncanonical-monad-instances
warn when Applicative or Monad instances have noncanonical definitions of return, pure, (>>), or (*>). See flag description in options-sanity for more details.
-Wnoncanonical-monadfail-instances
warn when Monad or MonadFail instances have noncanonical definitions of fail. See flag description in options-sanity for more details.
-Wnoncanonical-monoid-instances
warn when Semigroup or Monoid instances have noncanonical definitions of (<>) or mappend. See flag description in options-sanity for more details.
-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 -XPartialTypeSignatures is enabled. Not applicable when -XPartialTypesignatures is not enabled, in which case errors are generated for such holes. See partial-type-signatures.
-Wredundant-constraints
Have the compiler warn about redundant constraints in type signatures.
-Wsafe
warn if the module being compiled is regarded to be safe.
-Wsemigroup
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.
-Wspace-after-bang
warn for missing space before the second argument of an infix definition of (!) when -XBangPatterns are not enabled
-Wstar-binder
warn about binding the (*) type operator despite -XStarIsType
-Wstar-is-type
warn when * is used to mean Data.Kind.Type
-Wtabs
warn if there are tabs in the source file
-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
-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
-Wunrecognised-pragmas
warn about uses of pragmas that GHC doesn't recognise
-Wunrecognised-warning-flags
throw a warning when an unreconised -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-pattern-binds
warn about pattern match bindings that are unused
-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
-Wwarn
make warnings non-fatal
-Wwarnings-deprecations
warn about uses of functions & types that have warnings or deprecated pragmas
-Wwrong-do-bind
warn about do bindings that appear to throw away monadic values that you should have bound instead

COPYRIGHT

Copyright 2015. The University Court of the University of Glasgow. All rights reserved.

AUTHOR

The GHC Team

COPYRIGHT

2019, GHC Team
September 12, 2019 8.8.1