1GHC(1) Glasgow Haskell Compiler GHC(1)
2
6 ghc - the Glasgow Haskell Compiler
7
9 ghc [option|filename]
10 ghci [option|filename]
11
13 This manual page documents briefly the ghc and ghci commands. Note that
14 ghci is not yet available on all architectures. Extensive documentation
15 is available in various other formats including PDF and HTML.
16 Each of GHC's command line options is classified as either static or
18 dynamic. A static flag may only be specified on the command line,
19 whereas a dynamic flag may also be given in an OPTIONS pragma in a
20 source file or set from the GHCi command-line with :set .
21 As a rule of thumb, all the language options are dynamic, as are the
23 warning options and the debugging options.
24 The rest are static, with the notable exceptions of -v, -cpp, -fasm,
26 -fvia-C, -fllvm, and -#include. The OPTIONS sections lists the status
27 of each flag.
28 Common suffixes of file names for Haskell are:
30 .hs Haskell source code; preprocess, compile
32 .lhs literate Haskell source; unlit, preprocess, compile
34 .hi Interface file; contains information about exported symbols
36 .hc intermediate C files
38 .⟨way⟩_o
40 object files for "way" ⟨way⟩; common ways are:
41 dyn dynamically-linked
43 p built with profiling
45 .⟨way⟩_hi
47 interface files for "way" ⟨way⟩; common ways are:
48
50 Code generation
51 -dynamic-too -fasm -fllvm -fbyte-code -fexternal-dynamic-refs
52 -fllvm -fasm -fno-code -fobject-code -fPIC -fPIE -fwrite-inter‐
53 face
54 Debugging the compiler
56 -dcmm-lint -dcore-lint -ddump-asm -ddump-asm-expanded
57 -ddump-asm-liveness -ddump-asm-native -ddump-asm-regalloc
58 -ddump-asm-regalloc-stages -ddump-asm-stats -ddump-bcos
59 -ddump-cfg-weights -ddump-cmm -ddump-cmm-caf -ddump-cmm-cbe
60 -ddump-cmm-cfg -ddump-cmm-cps -ddump-cmm-from-stg
61 -ddump-cmm-info -ddump-cmm-proc -ddump-cmm-procmap
62 -ddump-cmm-raw -ddump-cmm-sink -ddump-cmm-sp -ddump-cmm-split
63 -ddump-cmm-switch -ddump-cmm-verbose -ddump-cmm-verbose-by-proc
64 -ddump-core-stats -ddump-cse -ddump-deriv -ddump-ds
65 -ddump-ds-preopt -ddump-ec-trace -ddump-file-prefix=⟨str⟩
66 -ddump-foreign -ddump-hpc -ddump-if-trace -ddump-inlinings
67 -ddump-json -ddump-llvm -ddump-mod-map -ddump-occur-anal
68 -ddump-opt-cmm -ddump-parsed -ddump-parsed-ast -ddump-prep
69 -ddump-rn -ddump-rn-ast -ddump-rn-stats -ddump-rn-trace
70 -ddump-rtti -ddump-rule-firings -ddump-rule-rewrites
71 -ddump-rules -ddump-simpl -ddump-simpl-iterations
72 -ddump-simpl-stats -ddump-spec -ddump-splices -ddump-stg
73 -ddump-stg-final -ddump-stg-unarised -ddump-str-signatures
74 -ddump-stranal -ddump-tc -ddump-tc-ast -ddump-tc-trace
75 -ddump-ticked -ddump-timings -ddump-to-file -ddump-types
76 -ddump-worker-wrapper -dfaststring-stats -dhex-word-literals
77 -dinitial-unique=⟨s⟩ -dinline-check=⟨str⟩ -dno-debug-output
78 -ddebug-output -dno-typeable-binds -dppr-case-as-let
79 -dppr-cols=⟨n⟩ -dppr-debug -dppr-user-length -drule-check=⟨str⟩
80 -dshow-passes -dstg-lint -dsuppress-all -dsuppress-coercions
81 -dsuppress-idinfo -dsuppress-module-prefixes -dsup‐
82 press-stg-free-vars -dsuppress-ticks -dsuppress-timestamps
83 -dsuppress-type-applications -dsuppress-type-signatures -dsup‐
84 press-unfoldings -dsuppress-uniques -dsuppress-var-kinds
85 -dth-dec-file -dunique-increment=⟨i⟩ -dverbose-core2core -dver‐
86 bose-stg2stg -falignment-sanitisation -fcatch-bottoms
87 -fllvm-fill-undef-with-garbage -fproc-alignment -g -g⟨n⟩
88 C pre-processor
90 -cpp -D⟨symbol⟩[=⟨value⟩] -U⟨symbol⟩ -I⟨dir⟩ -U⟨symbol⟩
91 Finding imports
93 -i -i⟨dir⟩[:⟨dir⟩]*
94 Interactive mode
96 -fbreak-on-error -fno-break-on-error -fbreak-on-exception
97 -fno-break-on-exception -fghci-hist-size=⟨n⟩ -fghci-leak-check
98 -fno-ghci-leak-check -flocal-ghci-history -fno-local-ghci-his‐
99 tory -fno-it -fno-no-it -fprint-bind-result -fno-print-bind-re‐
100 sult -fprint-evld-with-show -fshow-loaded-modules -ghci-script
101 -ignore-dot-ghci -interactive-print ⟨name⟩
102 Interface files
104 --show-iface ⟨file⟩ -ddump-hi -ddump-hi-diffs -ddump-minimal-im‐
105 ports
106 Keeping intermediate files
108 -keep-hc-file -keep-hc-files -keep-hi-files -no-keep-hi-files
109 -keep-hscpp-file -keep-hscpp-files -keep-llvm-file
110 -keep-llvm-files -keep-o-files -no-keep-o-files -keep-s-file
111 -keep-s-files -keep-tmp-files
112 Language options
114 -fno-safe-haskell -fsort-by-size-hole-fits
115 -fno-sort-by-size-hole-fits -fsort-by-subsumption-hole-fits
116 -fno-sort-by-subsumption-hole-fits -Winferred-safe-imports
117 -Wno-inferred-safe-imports -Wmissing-safe-haskell-mode
118 -Wno-missing-safe-haskell-mode -XAllowAmbiguousTypes -XApplica‐
119 tiveDo -XArrows -XBangPatterns -XBinaryLiterals -XBlockArguments
120 -XCApiFFI -XConstrainedClassMethods -XConstraintKinds -XCPP
121 -XCUSKs -XDataKinds -XDatatypeContexts -XDefaultSignatures
122 -XDeriveAnyClass -XDeriveDataTypeable -XDeriveFoldable -XDerive‐
123 Functor -XDeriveGeneric -XDeriveLift -XDeriveTraversable
124 -XDerivingStrategies -XDerivingVia -XDisambiguateRecordFields
125 -XDuplicateRecordFields -XEmptyCase -XEmptyDataDecls -XEmpty‐
126 DataDeriving -XExistentialQuantification -XExplicitForAll -XEx‐
127 plicitNamespaces -XExtendedDefaultRules -XFlexibleContexts
128 -XFlexibleInstances -XForeignFunctionInterface -XFunctionalDe‐
129 pendencies -XGADTs -XGADTSyntax -XGeneralisedNewtypeDeriving
130 -XGeneralizedNewtypeDeriving -XHaskell2010 -XHaskell98
131 -XHexFloatLiterals -XImplicitParams -XImportQualifiedPost -XIm‐
132 predicativeTypes -XIncoherentInstances -XInstanceSigs -XInter‐
133 ruptibleFFI -XKindSignatures -XLambdaCase -XLiberalTypeSynonyms
134 -XMagicHash -XMonadComprehensions -XMonadFailDesugaring
135 -XMonoLocalBinds -XMultiParamTypeClasses -XMultiWayIf -XNamed‐
136 FieldPuns -XNamedWildCards -XNegativeLiterals -XNoImplicitPre‐
137 lude -XNoMonomorphismRestriction -XNondecreasingIndentation
138 -XNoPatternGuards -XNoTraditionalRecordSyntax -XNPlusKPatterns
139 -XNullaryTypeClasses -XNumDecimals -XNumericUnderscores -XOver‐
140 lappingInstances -XOverloadedLabels -XOverloadedLists -XOver‐
141 loadedStrings -XPackageImports -XParallelListComp -XPartial‐
142 TypeSignatures -XPatternSynonyms -XPolyKinds -XPostfixOperators
143 -XQuantifiedConstraints -XQuasiQuotes -XRank2Types -XRankNTypes
144 -XRebindableSyntax -XRecordWildCards -XRecursiveDo -XRoleAnnota‐
145 tions -XSafe -XScopedTypeVariables -XStandaloneDeriving -XStan‐
146 daloneKindSignatures -XStarIsType -XStaticPointers -XStrict
147 -XStrictData -XTemplateHaskell -XTemplateHaskellQuotes -XTrans‐
148 formListComp -XTrustworthy -XTupleSections -XTypeApplications
149 -XTypeFamilies -XTypeFamilyDependencies -XTypeInType -XTypeOper‐
150 ators -XTypeSynonymInstances -XUnboxedSums -XUnboxedTuples -XUn‐
151 decidableInstances -XUndecidableSuperClasses -XUnicodeSyntax
152 -XUnliftedFFITypes -XUnliftedNewtypes -XUnsafe -XViewPatterns
153 Linking options
155 -c -debug -dylib-install-name ⟨path⟩ -dynamic -dynload -eventlog
156 -fno-embed-manifest -fno-gen-manifest -fno-shared-implib -frame‐
157 work ⟨name⟩ -framework-path ⟨dir⟩ -fwhole-archive-hs-libs
158 -keep-cafs -L ⟨dir⟩ -l ⟨lib⟩ -main-is ⟨thing⟩ -no-hs-main
159 -no-rtsopts-suggestions -package ⟨name⟩ -pie -rdynamic -rt‐
160 sopts[=⟨none|some|all|ignore|ignoreAll⟩] -shared -split-sections
161 -static -staticlib -threaded -with-rtsopts=⟨opts⟩
162 Miscellaneous options
164 -fexternal-interpreter -fglasgow-exts -fno-glasgow-exts -ghcver‐
165 sion-file ⟨path to ghcversion.h⟩ -H ⟨size⟩ -j[⟨n⟩]
166 Modes of operation
168 --frontend ⟨module⟩ --help -? --info --interactive --make
169 --mk-dll --numeric-version --print-libdir --show-iface ⟨file⟩
170 --show-options --supported-extensions --supported-languages
171 --version -V -e ⟨expr⟩ -M
172 Individual optimizations
174 -fasm-shortcutting -fno-asm-shortcutting -fbinary-blob-thresh‐
175 old=⟨n⟩ -fblock-layout-cfg -fno-block-layout-cfg -fblock-lay‐
176 out-weightless -fno-block-layout-weightless -fblock-lay‐
177 out-weights -fcall-arity -fno-call-arity -fcase-folding
178 -fno-case-folding -fcase-merge -fno-case-merge -fcmm-elim-com‐
179 mon-blocks -fno-cmm-elim-common-blocks -fcmm-sink -fno-cmm-sink
180 -fcpr-anal -fno-cpr-anal -fcross-module-specialise
181 -fno-cross-module-specialise -fcse -fno-cse -fdicts-cheap
182 -fno-dicts-cheap -fdicts-strict -fno-dicts-strict
183 -fdmd-tx-dict-sel -fno-dmd-tx-dict-sel -fdo-eta-reduction
184 -fno-do-eta-reduction -fdo-lambda-eta-expansion
185 -fno-do-lambda-eta-expansion -feager-blackholing -fenable-re‐
186 write-rules -fno-enable-rewrite-rules -fexcess-precision
187 -fno-excess-precision -fexitification -fno-exitification -fex‐
188 pose-all-unfoldings -fno-expose-all-unfoldings -ffloat-in
189 -fno-float-in -ffull-laziness -fno-full-laziness -ffun-to-thunk
190 -fno-fun-to-thunk -fignore-asserts -fno-ignore-asserts -fig‐
191 nore-interface-pragmas -fno-ignore-interface-pragmas
192 -flate-dmd-anal -fno-late-dmd-anal -flate-specialise
193 -fno-late-specialise -fliberate-case -fno-liberate-case -fliber‐
194 ate-case-threshold=⟨n⟩ -fno-liberate-case-threshold
195 -fllvm-pass-vectors-in-regs -fno-llvm-pass-vectors-in-regs
196 -floopification -fno-loopification -fmax-inline-alloc-size=⟨n⟩
197 -fmax-inline-memcpy-insns=⟨n⟩ -fmax-inline-memset-insns=⟨n⟩
198 -fmax-simplifier-iterations=⟨n⟩ -fmax-uncovered-patterns=⟨n⟩
199 -fmax-worker-args=⟨n⟩ -fno-opt-coercion -fno-pre-inlining
200 -fno-state-hack -fomit-interface-pragmas -fno-omit-inter‐
201 face-pragmas -fomit-yields -fno-omit-yields -foptimal-applica‐
202 tive-do -fno-optimal-applicative-do -fpedantic-bottoms
203 -fno-pedantic-bottoms -fregs-graph -fno-regs-graph -fregs-itera‐
204 tive -fno-regs-iterative -fsimpl-tick-factor=⟨n⟩ -fsimpli‐
205 fier-phases=⟨n⟩ -fsolve-constant-dicts -fno-solve-constant-dicts
206 -fspec-constr -fno-spec-constr -fspec-constr-count=⟨n⟩
207 -fno-spec-constr-count -fspec-constr-keen -fno-spec-constr-keen
208 -fspec-constr-threshold=⟨n⟩ -fno-spec-constr-threshold -fspe‐
209 cialise -fno-specialise -fspecialise-aggressively -fno-spe‐
210 cialise-aggressively -fstatic-argument-transformation
211 -fno-static-argument-transformation -fstg-cse -fno-stg-cse
212 -fstg-lift-lams -fno-stg-lift-lams -fstg-lift-lams-known
213 -fno-stg-lift-lams-known -fstg-lift-lams-non-rec-args
214 -fno-stg-lift-lams-non-rec-args-any -fstg-lift-lams-rec-args
215 -fno-stg-lift-lams-rec-args-any -fstrictness -fno-strictness
216 -fstrictness-before=⟨n⟩ -funbox-small-strict-fields -fno-un‐
217 box-small-strict-fields -funbox-strict-fields -fno-un‐
218 box-strict-fields -funfolding-creation-threshold=⟨n⟩ -funfold‐
219 ing-dict-discount=⟨n⟩ -funfolding-fun-discount=⟨n⟩ -funfold‐
220 ing-keeness-factor=⟨n⟩ -funfolding-use-threshold=⟨n⟩
221 -fworker-wrapper
222 Optimization levels
224 -O -O1 -O0 -O0 -O2 -O0 -O⟨n⟩ -O0
225 Package options
227 -clear-package-db -distrust ⟨pkg⟩ -distrust-all-packages -fpack‐
228 age-trust -global-package-db -hide-all-packages -hide-package
229 ⟨pkg⟩ -ignore-package ⟨pkg⟩ -no-auto-link-packages
230 -no-global-package-db -no-user-package-db -package ⟨pkg⟩ -pack‐
231 age-db ⟨file⟩ -package-env ⟨file⟩|⟨name⟩ -package-id ⟨unit-id⟩
232 -this-unit-id ⟨unit-id⟩ -trust ⟨pkg⟩ -user-package-db
233 Phases of compilation
235 -C -c -E -F -S -x ⟨suffix⟩
236 Overriding external programs
238 -pgma ⟨cmd⟩ -pgmc ⟨cmd⟩ -pgmdll ⟨cmd⟩ -pgmF ⟨cmd⟩ -pgmi ⟨cmd⟩
239 -pgminstall_name_tool ⟨cmd⟩ -pgmL ⟨cmd⟩ -pgml ⟨cmd⟩ -pgmlc ⟨cmd⟩
240 -pgmlibtool ⟨cmd⟩ -pgmlm ⟨cmd⟩ -pgmlo ⟨cmd⟩ -pgmotool ⟨cmd⟩
241 -pgmP ⟨cmd⟩ -pgms ⟨cmd⟩ -pgmwindres ⟨cmd⟩
242 Phase-specific options
244 -opta ⟨option⟩ -optc ⟨option⟩ -optcxx ⟨option⟩ -optdll ⟨option⟩
245 -optF ⟨option⟩ -opti ⟨option⟩ -optL ⟨option⟩ -optl ⟨option⟩
246 -optlc ⟨option⟩ -optlm ⟨option⟩ -optlo ⟨option⟩ -optP ⟨option⟩
247 -optwindres ⟨option⟩ -pgmc-supports-no-pie
248 Platform-specific options
250 -mbmi2 -msse2 -msse4.2
251 Compiler plugins
253 -fclear-plugins -fplugin-opt=⟨module⟩:⟨args⟩ -fplugin-trustwor‐
254 thy -fplugin=⟨module⟩ -hide-all-plugin-packages -plugin-package
255 ⟨pkg⟩ -plugin-package-id ⟨pkg-id⟩
256 Profiling
258 -fno-prof-auto -fprof-auto -fno-prof-cafs -fprof-cafs
259 -fno-prof-count-entries -fprof-count-entries -fprof-auto
260 -fno-prof-auto -fprof-auto-calls -fno-prof-auto-calls
261 -fprof-auto-exported -fno-prof-auto -fprof-auto-top
262 -fno-prof-auto -fprof-cafs -fno-prof-cafs -prof -ticky
263 Program coverage
265 -fhpc
266 Recompilation checking
268 -fforce-recomp -fno-force-recomp -fignore-hpc-changes -fno-ig‐
269 nore-hpc-changes -fignore-optim-changes -fno-ignore-op‐
270 tim-changes
271 Redirecting output
273 --exclude-module=⟨file⟩ -ddump-mod-cycles -dep-makefile ⟨file⟩
274 -dep-suffix ⟨suffix⟩ -dumpdir ⟨dir⟩ -hcsuf ⟨suffix⟩ -hidir ⟨dir⟩
275 -hiedir ⟨dir⟩ -hiesuf ⟨suffix⟩ -hisuf ⟨suffix⟩ -include-cpp-deps
276 -include-pkg-deps -o ⟨file⟩ -odir ⟨dir⟩ -ohi ⟨file⟩ -osuf ⟨suf‐
277 fix⟩ -outputdir ⟨dir⟩ -stubdir ⟨dir⟩
278 Temporary files
280 -tmpdir ⟨dir⟩
281 Verbosity options
283 -fabstract-refinement-hole-fits -fno-abstract-refine‐
284 ment-hole-fits -fdefer-diagnostics -fdiagnostics-color=⟨al‐
285 ways|auto|never⟩ -fdiagnostics-show-caret -fno-diagnos‐
286 tics-show-caret -ferror-spans -fhide-source-paths -fkeep-going
287 -fmax-refinement-hole-fits=⟨n⟩ -fno-max-refinement-hole-fits
288 -fmax-relevant-binds=⟨n⟩ -fno-max-relevant-binds
289 -fmax-valid-hole-fits=⟨n⟩ -fno-max-valid-hole-fits
290 -fno-show-valid-hole-fits -fno-sort-valid-hole-fits
291 -fsort-valid-hole-fits -fprint-axiom-incomps -fno-print-ax‐
292 iom-incomps -fprint-equality-relations -fno-print-equality-rela‐
293 tions -fprint-expanded-synonyms -fno-print-expanded-synonyms
294 -fprint-explicit-coercions -fno-print-explicit-coercions
295 -fprint-explicit-foralls -fno-print-explicit-foralls -fprint-ex‐
296 plicit-kinds -fno-print-explicit-kinds -fprint-explicit-run‐
297 time-reps -fno-print-explicit-runtime-reps -fprint-potential-in‐
298 stances -fno-print-potential-instances -fprint-typechecker-elab‐
299 oration -fno-print-typechecker-elaboration -fprint-unicode-syn‐
300 tax -fno-print-unicode-syntax -frefinement-level-hole-fits=⟨n⟩
301 -fno-refinement-level-hole-fits -freverse-errors -fno-re‐
302 verse-errors -fshow-docs-of-hole-fits
303 -fno-show-docs-of-hole-fits -fshow-hole-constraints
304 -fshow-hole-matches-of-hole-fits
305 -fno-show-hole-matches-of-hole-fits -fshow-prove‐
306 nance-of-hole-fits -fno-show-provenance-of-hole-fits
307 -fshow-type-app-of-hole-fits -fno-show-type-app-of-hole-fits
308 -fshow-type-app-vars-of-hole-fits
309 -fno-show-type-app-vars-of-hole-fits -fshow-type-of-hole-fits
310 -fno-type-of-hole-fits -funclutter-valid-hole-fits -Rghc-timing
311 -v -v⟨n⟩
312 Warnings
314 -fdefer-out-of-scope-variables -fno-defer-out-of-scope-variables
315 -fdefer-type-errors -fno-defer-type-errors -fdefer-typed-holes
316 -fno-defer-typed-holes -fenable-th-splice-warnings -fno-en‐
317 able-th-splices -fhelpful-errors -fno-helpful-errors -fmax-pm‐
318 check-models=⟨n⟩ -fshow-warning-groups -fno-show-warning-groups
319 -fvia-C -W -w -w -Wall -w -Wall-missed-specialisations
320 -Wno-all-missed-specialisations -Wcompat -Wno-compat -Wcom‐
321 pat-unqualified-imports -Wno-compat-unqualified-imports
322 -Wcpp-undef -Wdeferred-out-of-scope-variables -Wno-de‐
323 ferred-out-of-scope-variables -Wdeferred-type-errors -Wno-de‐
324 ferred-type-errors -Wdeprecated-flags -Wno-deprecated-flags
325 -Wdeprecations -Wno-deprecations -Wderiving-defaults -Wno-deriv‐
326 ing-defaults -Wdodgy-exports -Wno-dodgy-exports -Wdodgy-for‐
327 eign-imports -Wno-dodgy-foreign-import -Wdodgy-imports
328 -Wno-dodgy-imports -Wduplicate-constraints -Wno-duplicate-con‐
329 straints -Wduplicate-exports -Wno-duplicate-exports -Wempty-enu‐
330 merations -Wno-empty-enumerations -Werror -Wwarn -Weverything
331 -Whi-shadowing -Wno-hi-shadowing -Widentities -Wno-identities
332 -Wimplicit-kind-vars -Wno-implicit-kind-vars -Wimplicit-prelude
333 -Wno-implicit-prelude -Winaccessible-code -Wno-inaccessible-code
334 -Wincomplete-patterns -Wno-incomplete-patterns -Wincom‐
335 plete-record-updates -Wno-incomplete-record-updates -Wincom‐
336 plete-uni-patterns -Wno-incomplete-uni-patterns -Win‐
337 line-rule-shadowing -Wno-inline-rule-shadowing -Wmissed-ex‐
338 tra-shared-lib -Wno-missed-extra-shared-lib -Wmissed-specialisa‐
339 tions -Wno-missed-specialisations -Wmissing-deriving-strategies
340 -Wno-missing-deriving-strategies -Wmissing-export-lists
341 -fnowarn-missing-export-lists -Wmissing-exported-signatures
342 -Wno-missing-exported-signatures -Wmissing-exported-sigs
343 -Wno-missing-exported-sigs -Wmissing-fields -Wno-missing-fields
344 -Wmissing-home-modules -Wno-missing-home-modules -Wmissing-im‐
345 port-lists -fnowarn-missing-import-lists -Wmissing-local-signa‐
346 tures -Wno-missing-local-signatures -Wmissing-local-sigs
347 -Wno-missing-local-sigs -Wmissing-methods -Wno-missing-methods
348 -Wmissing-monadfail-instances -Wno-missing-monadfail-instances
349 -Wmissing-pattern-synonym-signatures -Wno-missing-pattern-syn‐
350 onym-signatures -Wmissing-signatures -Wno-missing-signatures
351 -Wmonomorphism-restriction -Wno-monomorphism-restriction
352 -Wname-shadowing -Wno-name-shadowing -Wno-compat -Wcompat -Wnon‐
353 canonical-monad-instances -Wno-noncanonical-monad-instances
354 -Wnoncanonical-monadfail-instances -Wno-noncanonical-monad‐
355 fail-instances -Wnoncanonical-monoid-instances -Wno-noncanoni‐
356 cal-monoid-instances -Worphans -Wno-orphans -Woverflowed-liter‐
357 als -Wno-overflowed-literals -Woverlapping-patterns -Wno-over‐
358 lapping-patterns -Wpartial-fields -Wno-partial-fields -Wpar‐
359 tial-type-signatures -Wno-partial-type-signatures -Wredun‐
360 dant-constraints -Wno-redundant-constraints -Wredun‐
361 dant-record-wildcards -Wno-redundant-record-wildcards -Wsafe
362 -Wno-safe -Wsemigroup -Wno-semigroup -Wsimplifiable-class-con‐
363 straints -Wno-simplifiable-class-constraints -Wspace-after-bang
364 -Wno-missing-space-after-bang -Wstar-binder -Wno-star-binder
365 -Wstar-is-type -Wno-star-is-type -Wtabs -Wno-tabs -Wtrustwor‐
366 thy-safe -Wno-safe -Wtype-defaults -Wno-type-defaults
367 -Wtyped-holes -Wno-typed-holes -Wunbanged-strict-patterns
368 -Wno-unbanged-strict-patterns -Wunrecognised-pragmas -Wno-un‐
369 recognised-pragmas -Wunrecognised-warning-flags -Wno-unrecog‐
370 nised-warning-flags -Wunsafe -Wno-unsafe -Wunsupported-call‐
371 ing-conventions -Wno-unsupported-calling-conventions -Wunsup‐
372 ported-llvm-version -Wno-monomorphism-restriction
373 -Wunticked-promoted-constructors -Wno-unticked-promoted-con‐
374 structors -Wunused-binds -Wno-unused-binds -Wunused-do-bind
375 -Wno-unused-do-bind -Wunused-foralls -Wno-unused-foralls
376 -Wunused-imports -Wno-unused-imports -Wunused-local-binds
377 -Wno-unused-local-binds -Wunused-matches -Wno-unused-matches
378 -Wunused-packages -Wno-unused-packages -Wunused-pattern-binds
379 -Wno-unused-pattern-binds -Wunused-record-wildcards -Wno-un‐
380 used-record-wildcards -Wunused-top-binds -Wno-unused-top-binds
381 -Wunused-type-patterns -Wno-unused-type-patterns -Wwarn -Werror
382 -Wwarnings-deprecations -Wno-warnings-deprecations
383 -Wwrong-do-bind -Wno-wrong-do-bind
384 Code generation
386 -dynamic-too
387 Build dynamic object files as well as static object files during
388 compilation
389 -fasm Use the native code generator
391 -fbyte-code
393 Generate byte-code
394 -fexternal-dynamic-refs
396 Generate code for linking against dynamic libraries
397 -fllvm Compile using the LLVM code generator
399 -fno-code
401 Omit code generation
402 -fobject-code
404 Generate object code
405 -fPIC Generate position-independent code (where available)
407 -fPIE Generate code for a position-independent executable (where
409 available)
410 -fwrite-interface
412 Always write interface files
413 Debugging the compiler
415 -dcmm-lint
416 C-\- pass sanity checking
417 -dcore-lint
419 Turn on internal sanity checking
420 -ddump-asm
422 Dump final assembly
423 -ddump-asm-expanded
425 Dump the result of the synthetic instruction expansion pass.
426 -ddump-asm-liveness
428 Dump assembly augmented with register liveness
429 -ddump-asm-native
431 Dump initial assembly
432 -ddump-asm-regalloc
434 Dump the result of register allocation
435 -ddump-asm-regalloc-stages
437 Dump the build/spill stages of the -fregs-graph register alloca‐
438 tor.
439 -ddump-asm-stats
441 Dump statistics from the register allocator.
442 -ddump-bcos
444 Dump interpreter byte code
445 -ddump-cfg-weights
447 Dump the assumed weights of the CFG.
448 -ddump-cmm
450 Dump the final C-\- output
451 -ddump-cmm-caf
453 Dump the results of the C-\- CAF analysis pass.
454 -ddump-cmm-cbe
456 Dump the results of common block elimination
457 -ddump-cmm-cfg
459 Dump the results of the C-\- control flow optimisation pass.
460 -ddump-cmm-cps
462 Dump the results of the CPS pass
463 -ddump-cmm-from-stg
465 Dump STG-to-C-\- output
466 -ddump-cmm-info
468 Dump the results of the C-\- info table augmentation pass.
469 -ddump-cmm-proc
471 Dump the results of proc-point analysis
472 -ddump-cmm-procmap
474 Dump the results of the C-\- proc-point map pass.
475 -ddump-cmm-raw
477 Dump raw C-\-
478 -ddump-cmm-sink
480 Dump the results of the C-\- sinking pass.
481 -ddump-cmm-sp
483 Dump the results of the C-\- stack layout pass.
484 -ddump-cmm-split
486 Dump the results of the C-\- proc-point splitting pass.
487 -ddump-cmm-switch
489 Dump the results of switch lowering passes
490 -ddump-cmm-verbose
492 Write output from main C-\- pipeline passes to files
493 -ddump-cmm-verbose-by-proc
495 Show output from main C-\- pipeline passes (grouped by proc)
496 -ddump-core-stats
498 Print a one-line summary of the size of the Core program at the
499 end of the optimisation pipeline
500 -ddump-cse
502 Dump CSE output
503 -ddump-deriv
505 Dump deriving output
506 -ddump-ds
508 Dump desugarer output.
509 -ddump-ec-trace
511 Trace exhaustiveness checker
512 -ddump-file-prefix=⟨str⟩
514 Set the prefix of the filenames used for debugging output.
515 -ddump-foreign
517 Dump foreign export stubs
518 -ddump-hpc
520 An alias for -ddump-ticked.
521 -ddump-if-trace
523 Trace interface files
524 -ddump-inlinings
526 Dump inlining info
527 -ddump-json
529 Dump error messages as JSON documents
530 -ddump-llvm
532 Dump LLVM intermediate code.
533 -ddump-mod-map
535 Dump the state of the module mapping database.
536 -ddump-occur-anal
538 Dump occurrence analysis output
539 -ddump-opt-cmm
541 Dump the results of C-\- to C-\- optimising passes
542 -ddump-parsed
544 Dump parse tree
545 -ddump-parsed-ast
547 Dump parser output as a syntax tree
548 -ddump-prep
550 Dump prepared core
551 -ddump-rn
553 Dump renamer output
554 -ddump-rn-ast
556 Dump renamer output as a syntax tree
557 -ddump-rn-stats
559 Renamer stats
560 -ddump-rn-trace
562 Trace renamer
563 -ddump-rtti
565 Trace runtime type inference
566 -ddump-rule-firings
568 Dump rule firing info
569 -ddump-rule-rewrites
571 Dump detailed rule firing info
572 -ddump-rules
574 Dump rewrite rules
575 -ddump-simpl
577 Dump final simplifier output
578 -ddump-simpl-iterations
580 Dump output from each simplifier iteration
581 -ddump-simpl-stats
583 Dump simplifier stats
584 -ddump-spec
586 Dump specialiser output
587 -ddump-splices
589 Dump TH spliced expressions, and what they evaluate to
590 -ddump-stg
592 Show CoreToStg output
593 -ddump-stg-final
595 Show output of last STG pass.
596 -ddump-stg-unarised
598 Show unarised STG
599 -ddump-str-signatures
601 Dump strictness signatures
602 -ddump-stranal
604 Dump strictness analyser output
605 -ddump-tc
607 Dump typechecker output
608 -ddump-tc-ast
610 Dump typechecker output as a syntax tree
611 -ddump-tc-trace
613 Trace typechecker
614 -ddump-ticked
616 Dump the code instrumented by HPC (hpc).
617 -ddump-timings
619 Dump per-pass timing and allocation statistics
620 -ddump-to-file
622 Dump to files instead of stdout
623 -ddump-types
625 Dump type signatures
626 -ddump-worker-wrapper
628 Dump worker-wrapper output
629 -dfaststring-stats
631 Show statistics for fast string usage when finished
632 -dhex-word-literals
634 Print values of type Word# in hexadecimal.
635 -dinitial-unique=⟨s⟩
637 Start UniqSupply allocation from ⟨s⟩.
638 -dinline-check=⟨str⟩
640 Dump information about inlining decisions
641 -dno-debug-output
643 Suppress unsolicited debugging output
644 -dno-typeable-binds
646 Don't generate bindings for Typeable methods
647 -dppr-case-as-let
649 Print single alternative case expressions as strict lets.
650 -dppr-cols=⟨n⟩
652 Set the width of debugging output. For example -dppr-cols200
653 -dppr-debug
655 Turn on debug printing (more verbose)
656 -dppr-user-length
658 Set the depth for printing expressions in error msgs
659 -drule-check=⟨str⟩
661 Dump information about potential rule application
662 -dshow-passes
664 Print out each pass name as it happens
665 -dstg-lint
667 STG pass sanity checking
668 -dsuppress-all
670 In dumps, suppress everything (except for uniques) that is sup‐
671 pressible.
672 -dsuppress-coercions
674 Suppress the printing of coercions in Core dumps to make them
675 shorter
676 -dsuppress-idinfo
678 Suppress extended information about identifiers where they are
679 bound
680 -dsuppress-module-prefixes
682 Suppress the printing of module qualification prefixes
683 -dsuppress-stg-free-vars
685 Suppress the printing of closure free variable lists in STG out‐
686 put
687 -dsuppress-ticks
689 Suppress "ticks" in the pretty-printer output.
690 -dsuppress-timestamps
692 Suppress timestamps in dumps
693 -dsuppress-type-applications
695 Suppress type applications
696 -dsuppress-type-signatures
698 Suppress type signatures
699 -dsuppress-unfoldings
701 Suppress the printing of the stable unfolding of a variable at
702 its binding site
703 -dsuppress-uniques
705 Suppress the printing of uniques in debug output (easier to use
706 diff)
707 -dsuppress-var-kinds
709 Suppress the printing of variable kinds
710 -dth-dec-file
712 Dump evaluated TH declarations into *.th.hs files
713 -dunique-increment=⟨i⟩
715 Set the increment for the generated Unique's to ⟨i⟩.
716 -dverbose-core2core
718 Show output from each core-to-core pass
719 -dverbose-stg2stg
721 Show output from each STG-to-STG pass
722 -falignment-sanitisation
724 Compile with alignment checks for all info table dereferences.
725 -fcatch-bottoms
727 Insert error expressions after bottoming expressions; useful
728 when debugging the compiler.
729 -fllvm-fill-undef-with-garbage
731 Intruct LLVM to fill dead STG registers with garbage
732 -fproc-alignment
734 Align functions at given boundary.
735 -g Produce DWARF debug information in compiled object files. ⟨n⟩
737 can be 0, 1, or 2, with higher numbers producing richer output.
738 If ⟨n⟩ is omitted, level 2 is assumed.
739 C pre-processor
741 -cpp Run the C pre-processor on Haskell source files
742 -D⟨symbol⟩[=⟨value⟩]
744 Define a symbol in the C pre-processor
745 -I⟨dir⟩
747 Add ⟨dir⟩ to the directory search list for #include files
748 -U⟨symbol⟩
750 Undefine a symbol in the C pre-processor
751 Finding imports
753 -i Empty the import directory list
754 -i⟨dir⟩[:⟨dir⟩]*
756 add ⟨dir⟩, ⟨dir2⟩, etc. to import path
757 Interactive mode
759 -fbreak-on-error
760 Break on uncaught exceptions and errors
761 -fbreak-on-exception
763 Break on any exception thrown
764 -fghci-hist-size=⟨n⟩
766 Set the number of entries GHCi keeps for :history. See ghci-de‐
767 bugger.
768 -fghci-leak-check
770 (Debugging only) check for space leaks when loading new modules
771 in GHCi.
772 -flocal-ghci-history
774 Use current directory for the GHCi command history file
775 .ghci-history.
776 -fno-it
778 No longer set the special variable it.
779 -fprint-bind-result
781 Turn on printing of binding results in GHCi
782 -fprint-evld-with-show
784 Instruct :print to use Show instances where possible.
785 -fshow-loaded-modules
787 Show the names of modules that GHCi loaded after a :load com‐
788 mand.
789 -ghci-script
791 Read additional .ghci files
792 -ignore-dot-ghci
794 Disable reading of .ghci files
795 -interactive-print ⟨name⟩
797 Select the function to use for printing evaluated expressions in
798 GHCi
799 Interface files
801 --show-iface ⟨file⟩
802 See modes.
803 -ddump-hi
805 Dump the new interface to stdout
806 -ddump-hi-diffs
808 Show the differences vs. the old interface
809 -ddump-minimal-imports
811 Dump a minimal set of imports
812 Keeping intermediate files
814 -keep-hc-file
815 Retain intermediate .hc files.
816 -keep-hi-files
818 Retain intermediate .hi files (the default).
819 -keep-hscpp-file
821 Retain intermediate .hscpp files.
822 -keep-llvm-file
824 Retain intermediate LLVM .ll files. Implies -fllvm.
825 -keep-o-files
827 Retain intermediate .o files (the default).
828 -keep-s-file
830 Retain intermediate .s files.
831 -keep-tmp-files
833 Retain all intermediate temporary files.
834 Language options
836 -fno-safe-haskell
837 Disable Safe Haskell
838 -fsort-by-size-hole-fits
840 Sort valid hole fits by size.
841 -fsort-by-subsumption-hole-fits
843 Sort valid hole fits by subsumption.
844 -Winferred-safe-imports
846 warn when an explicitly Safe Haskell module imports a Safe-In‐
847 ferred one
848 -Wmissing-safe-haskell-mode
850 warn when the Safe Haskell mode is not explicitly specified.
851 -XAllowAmbiguousTypes
853 Allow the user to write ambiguous types, and the type inference
854 engine to infer them.
855 -XApplicativeDo
857 Enable Applicative do-notation desugaring
858 -XArrows
860 Enable arrow notation extension
861 -XBangPatterns
863 Enable bang patterns.
864 -XBinaryLiterals
866 Enable support for binary literals.
867 -XBlockArguments
869 Allow do blocks and other constructs as function arguments.
870 -XCApiFFI
872 Enable the CAPI calling convention.
873 -XConstrainedClassMethods
875 Enable constrained class methods.
876 -XConstraintKinds
878 Enable a kind of constraints.
879 -XCPP Enable the C preprocessor.
881 -XCUSKs
883 Enable detection of complete user-supplied kind signatures.
884 -XDataKinds
886 Enable datatype promotion.
887 -XDatatypeContexts
889 Allow contexts on data types.
890 -XDefaultSignatures
892 Enable default signatures.
893 -XDeriveAnyClass
895 Enable deriving for any class.
896 -XDeriveDataTypeable
898 Enable deriving for the Data class. Implied by (deprecated) Au‐
899 toDeriveTypeable.
900 -XDeriveFoldable
902 Enable deriving for the Foldable class. Implied by Derive‐
903 Traversable.
904 -XDeriveFunctor
906 Enable deriving for the Functor class. Implied by Derive‐
907 Traversable.
908 -XDeriveGeneric
910 Enable deriving for the Generic class.
911 -XDeriveLift
913 Enable deriving for the Lift class
914 -XDeriveTraversable
916 Enable deriving for the Traversable class. Implies DeriveFunc‐
917 tor and DeriveFoldable.
918 -XDerivingStrategies
920 Enables deriving strategies.
921 -XDerivingVia
923 Enable deriving instances via types of the same runtime repre‐
924 sentation. Implies DerivingStrategies.
925 -XDisambiguateRecordFields
927 Enable record field disambiguation. Implied by RecordWildCards.
928 -XDuplicateRecordFields
930 Allow definition of record types with identically-named fields.
931 -XEmptyCase
933 Allow empty case alternatives.
934 -XEmptyDataDecls
936 Allow definition of empty data types.
937 -XEmptyDataDeriving
939 Allow deriving instances of standard type classes for empty data
940 types.
941 -XExistentialQuantification
943 Enable liberalised type synonyms.
944 -XExplicitForAll
946 Enable explicit universal quantification. Implied by Scoped‐
947 TypeVariables, LiberalTypeSynonyms, RankNTypes and Existen‐
948 tialQuantification.
949 -XExplicitNamespaces
951 Enable using the keyword type to specify the namespace of en‐
952 tries in imports and exports (explicit-namespaces). Implied by
953 TypeOperators and TypeFamilies.
954 -XExtendedDefaultRules
956 Use GHCi's extended default rules in a normal module.
957 -XFlexibleContexts
959 Enable flexible contexts.
960 -XFlexibleInstances
962 Enable flexible instances. Implies TypeSynonymInstances.
963 -XForeignFunctionInterface
965 Enable foreign function interface.
966 -XFunctionalDependencies
968 Enable functional dependencies. Implies MultiParamTypeClasses.
969 -XGADTs
971 Enable generalised algebraic data types. Implies GADTSyntax and
972 MonoLocalBinds.
973 -XGADTSyntax
975 Enable generalised algebraic data type syntax.
976 -XGeneralisedNewtypeDeriving
978 Enable newtype deriving.
979 -XGeneralizedNewtypeDeriving
981 Enable newtype deriving.
982 -XHaskell2010
984 Use the Haskell 2010 language variant.
985 -XHaskell98
987 Use the Haskell 2010 language variant.
988 -XHexFloatLiterals
990 Enable support for hexadecimal floating point literals.
991 -XImplicitParams
993 Enable Implicit Parameters.
994 -XImportQualifiedPost
996 ImportQualifiedPost allows the syntax import M qualified
997 -XImpredicativeTypes
999 Enable impredicative types. Implies RankNTypes.
1000 -XIncoherentInstances
1002 Enable incoherent instances. Implies OverlappingInstances.
1003 -XInstanceSigs
1005 Enable instance signatures.
1006 -XInterruptibleFFI
1008 Enable interruptible FFI.
1009 -XKindSignatures
1011 Enable kind signatures. Implied by TypeFamilies and PolyKinds.
1012 -XLambdaCase
1014 Enable lambda-case expressions.
1015 -XLiberalTypeSynonyms
1017 Enable liberalised type synonyms.
1018 -XMagicHash
1020 Allow # as a postfix modifier on identifiers.
1021 -XMonadComprehensions
1023 Enable monad comprehensions.
1024 -XMonadFailDesugaring
1026 Enable monadfail desugaring.
1027 -XMonoLocalBinds
1029 Enable do not generalise local bindings. Implied by TypeFami‐
1030 lies and GADTs.
1031 -XMultiParamTypeClasses
1033 Enable multi parameter type classes. Implied by FunctionalDe‐
1034 pendencies.
1035 -XMultiWayIf
1037 Enable multi-way if-expressions.
1038 -XNamedFieldPuns
1040 Enable record puns.
1041 -XNamedWildCards
1043 Enable named wildcards.
1044 -XNegativeLiterals
1046 Enable support for negative literals.
1047 -XNoImplicitPrelude
1049 Don't implicitly import Prelude. Implied by RebindableSyntax.
1050 -XNoMonomorphismRestriction
1052 Disable the monomorphism restriction.
1053 -XNondecreasingIndentation
1055 Allow nested contexts to be at the same indentation level as its
1056 enclosing context.
1057 -XNoPatternGuards
1059 Disable pattern guards. Implied by Haskell98.
1060 -XNoTraditionalRecordSyntax
1062 Disable support for traditional record syntax (as supported by
1063 Haskell 98) C {f = x}
1064 -XNPlusKPatterns
1066 Enable support for n+k patterns. Implied by Haskell98.
1067 -XNullaryTypeClasses
1069 Deprecated, does nothing. nullary (no parameter) type classes
1070 are now enabled using MultiParamTypeClasses.
1071 -XNumDecimals
1073 Enable support for 'fractional' integer literals.
1074 -XNumericUnderscores
1076 Enable support for numeric underscores.
1077 -XOverlappingInstances
1079 Enable overlapping instances.
1080 -XOverloadedLabels
1082 Enable overloaded labels.
1083 -XOverloadedLists
1085 Enable overloaded lists.
1086 -XOverloadedStrings
1088 Enable overloaded string literals.
1089 -XPackageImports
1091 Enable package-qualified imports.
1092 -XParallelListComp
1094 Enable parallel list comprehensions.
1095 -XPartialTypeSignatures
1097 Enable partial type signatures.
1098 -XPatternSynonyms
1100 Enable pattern synonyms.
1101 -XPolyKinds
1103 Enable kind polymorphism. Implies KindSignatures.
1104 -XPostfixOperators
1106 Enable postfix operators.
1107 -XQuantifiedConstraints
1109 Allow forall quantifiers in constraints.
1110 -XQuasiQuotes
1112 Enable quasiquotation.
1113 -XRank2Types
1115 Enable rank-2 types. Synonym for RankNTypes.
1116 -XRankNTypes
1118 Enable rank-N types. Implied by ImpredicativeTypes.
1119 -XRebindableSyntax
1121 Employ rebindable syntax. Implies NoImplicitPrelude.
1122 -XRecordWildCards
1124 Enable record wildcards. Implies DisambiguateRecordFields.
1125 -XRecursiveDo
1127 Enable recursive do (mdo) notation.
1128 -XRoleAnnotations
1130 Enable role annotations.
1131 -XSafe Enable the Safe Haskell Safe mode.
1133 -XScopedTypeVariables
1135 Enable lexically-scoped type variables.
1136 -XStandaloneDeriving
1138 Enable standalone deriving.
1139 -XStandaloneKindSignatures
1141 Allow the use of standalone kind signatures.
1142 -XStarIsType
1144 Treat * as Data.Kind.Type.
1145 -XStaticPointers
1147 Enable static pointers.
1148 -XStrict
1150 Make bindings in the current module strict by default.
1151 -XStrictData
1153 Enable default strict datatype fields.
1154 -XTemplateHaskell
1156 Enable Template Haskell.
1157 -XTemplateHaskellQuotes
1159 Enable quotation subset of Template Haskell.
1160 -XTransformListComp
1162 Enable generalised list comprehensions.
1163 -XTrustworthy
1165 Enable the Safe Haskell Trustworthy mode.
1166 -XTupleSections
1168 Enable tuple sections.
1169 -XTypeApplications
1171 Enable type application syntax in terms and types.
1172 -XTypeFamilies
1174 Enable type families. Implies ExplicitNamespaces, KindSigna‐
1175 tures, and MonoLocalBinds.
1176 -XTypeFamilyDependencies
1178 Enable injective type families. Implies TypeFamilies.
1179 -XTypeInType
1181 Deprecated. Enable kind polymorphism and datatype promotion.
1182 -XTypeOperators
1184 Enable type operators. Implies ExplicitNamespaces.
1185 -XTypeSynonymInstances
1187 Enable type synonyms in instance heads. Implied by FlexibleIn‐
1188 stances.
1189 -XUnboxedSums
1191 Enable unboxed sums.
1192 -XUnboxedTuples
1194 Enable the use of unboxed tuple syntax.
1195 -XUndecidableInstances
1197 Enable undecidable instances.
1198 -XUndecidableSuperClasses
1200 Allow all superclass constraints, including those that may re‐
1201 sult in non-termination of the typechecker.
1202 -XUnicodeSyntax
1204 Enable unicode syntax.
1205 -XUnliftedFFITypes
1207 Enable unlifted FFI types
1208 -XUnliftedNewtypes
1210 Enable unlifted newtypes.
1211 -XUnsafe
1213 Enable Safe Haskell Unsafe mode.
1214 -XViewPatterns
1216 Enable view patterns.
1217 Linking options
1219 -c Stop after generating object (.o) file
1220 -debug Use the debugging runtime
1222 -dylib-install-name ⟨path⟩
1224 Set the install name (via -install_name passed to Apple's
1225 linker), specifying the full install path of the library file.
1226 Any libraries or executables that link with it later will pick
1227 up that path as their runtime search location for it. (Dar‐
1228 win/OS X only)
1229 -dynamic
1231 Build dynamically-linked object files and executables
1232 -dynload
1234 Selects one of a number of modes for finding shared libraries at
1235 runtime.
1236 -eventlog
1238 Enable runtime event tracing
1239 -fno-embed-manifest
1241 Do not embed the manifest in the executable (Windows only)
1242 -fno-gen-manifest
1244 Do not generate a manifest file (Windows only)
1245 -fno-shared-implib
1247 Don't generate an import library for a DLL (Windows only)
1248 -framework ⟨name⟩
1250 On Darwin/OS X/iOS only, link in the framework ⟨name⟩. This op‐
1251 tion corresponds to the -framework option for Apple's Linker.
1252 -framework-path ⟨dir⟩
1254 On Darwin/OS X/iOS only, add ⟨dir⟩ to the list of directories
1255 searched for frameworks. This option corresponds to the -F op‐
1256 tion for Apple's Linker.
1257 -fwhole-archive-hs-libs
1259 When linking a binary executable, this inserts the flag
1260 -Wl,--whole-archive before any -l flags for Haskell libraries,
1261 and -Wl,--no-whole-archive afterwards
1262 -keep-cafs
1264 Do not garbage-collect CAFs (top-level expressions) at runtime
1265 -L ⟨dir⟩
1267 Add ⟨dir⟩ to the list of directories searched for libraries
1268 -l ⟨lib⟩
1270 Link in library ⟨lib⟩
1271 -main-is ⟨thing⟩
1273 Set main module and function
1274 -no-hs-main
1276 Don't assume this program contains main
1277 -no-rtsopts-suggestions
1279 Don't print RTS suggestions about linking with -rt‐
1280 sopts[=⟨none|some|all|ignore|ignoreAll⟩].
1281 -package ⟨name⟩
1283 Expose package ⟨pkg⟩
1284 -pie Instruct the linker to produce a position-independent exe‐
1286 cutable.
1287 -rdynamic
1289 This instructs the linker to add all symbols, not only used
1290 ones, to the dynamic symbol table. Currently Linux and Win‐
1291 dows/MinGW32 only. This is equivalent to using -optl -rdynamic
1292 on Linux, and -optl -export-all-symbols on Windows.
1293 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩]
1295 Control whether the RTS behaviour can be tweaked via com‐
1296 mand-line flags and the GHCRTS environment variable. Using none
1297 means no RTS flags can be given; some means only a minimum of
1298 safe options can be given (the default); all (or no argument at
1299 all) means that all RTS flags are permitted; ignore means RTS
1300 flags can be given, but are treated as regular arguments and
1301 passed to the Haskell program as arguments; ignoreAll is the
1302 same as ignore, but GHCRTS is also ignored. -rtsopts does not
1303 affect -with-rtsopts behavior; flags passed via -with-rtsopts
1304 are used regardless of -rtsopts.
1305 -shared
1307 Generate a shared library (as opposed to an executable)
1308 -split-sections
1310 Split sections for link-time dead-code stripping
1311 -static
1313 Use static Haskell libraries
1314 -staticlib
1316 Generate a standalone static library (as opposed to an exe‐
1317 cutable). This is useful when cross compiling. The library to‐
1318 gether with all its dependencies ends up in in a single static
1319 library that can be linked against.
1320 -threaded
1322 Use the threaded runtime
1323 -with-rtsopts=⟨opts⟩
1325 Set the default RTS options to ⟨opts⟩.
1326 Miscellaneous options
1328 -fexternal-interpreter
1329 Run interpreted code in a separate process
1330 -fglasgow-exts
1332 Deprecated. Enable most language extensions; see options-lan‐
1333 guage for exactly which ones.
1334 -ghcversion-file ⟨path to ghcversion.h⟩
1336 (GHC as a C compiler only) Use this ghcversion.h file
1337 -H ⟨size⟩
1339 Set the minimum size of the heap to ⟨size⟩
1340 -j[⟨n⟩]
1342 When compiling with --make, compile ⟨n⟩ modules in parallel.
1343 Modes of operation
1345 --frontend ⟨module⟩
1346 run GHC with the given frontend plugin; see frontend_plugins for
1347 details.
1348 --help Display help
1350 --info display information about the compiler
1352 --interactive
1354 Interactive mode - normally used by just running ghci; see ghci
1355 for details.
1356 --make Build a multi-module Haskell program, automatically figuring out
1358 dependencies. Likely to be much easier, and faster, than using
1359 make; see make-mode for details.
1360 --mk-dll
1362 DLL-creation mode (Windows only)
1363 --numeric-version
1365 display GHC version (numeric only)
1366 --print-libdir
1368 display GHC library directory
1369 --show-iface ⟨file⟩
1371 display the contents of an interface file.
1372 --show-options
1374 display the supported command line options
1375 --supported-extensions
1377 display the supported language extensions
1378 --version
1380 display GHC version
1381 -e ⟨expr⟩
1383 Evaluate expr; see eval-mode for details.
1384 -M generate dependency information suitable for use in a Makefile;
1386 see makefile-dependencies for details.
1387 Individual optimizations
1389 -fasm-shortcutting
1390 Enable shortcutting on assembly. Implied by -O2.
1391 -fbinary-blob-threshold=⟨n⟩
1393 default: 500K. Tweak assembly generator for binary blobs.
1394 -fblock-layout-cfg
1396 Use the new cfg based block layout algorithm.
1397 -fblock-layout-weightless
1399 Ignore cfg weights for code layout.
1400 -fblock-layout-weights
1402 Sets edge weights used by the new code layout algorithm.
1403 -fcall-arity
1405 Enable call-arity optimisation. Implied by -O.
1406 -fcase-folding
1408 Enable constant folding in case expressions. Implied by -O.
1409 -fcase-merge
1411 Enable case-merging. Implied by -O.
1412 -fcmm-elim-common-blocks
1414 Enable Cmm common block elimination. Implied by -O.
1415 -fcmm-sink
1417 Enable Cmm sinking. Implied by -O.
1418 -fcpr-anal
1420 Turn on CPR analysis in the demand analyser. Implied by -O.
1421 -fcross-module-specialise
1423 Turn on specialisation of overloaded functions imported from
1424 other modules.
1425 -fcse Enable common sub-expression elimination. Implied by -O.
1427 -fdicts-cheap
1429 Make dictionary-valued expressions seem cheap to the optimiser.
1430 -fdicts-strict
1432 Make dictionaries strict
1433 -fdmd-tx-dict-sel
1435 Use a special demand transformer for dictionary selectors. Al‐
1436 ways enabled by default.
1437 -fdo-eta-reduction
1439 Enable eta-reduction. Implied by -O.
1440 -fdo-lambda-eta-expansion
1442 Enable lambda eta-expansion. Always enabled by default.
1443 -feager-blackholing
1445 Turn on eager blackholing
1446 -fenable-rewrite-rules
1448 Switch on all rewrite rules (including rules generated by auto‐
1449 matic specialisation of overloaded functions). Implied by -O.
1450 -fexcess-precision
1452 Enable excess intermediate precision
1453 -fexitification
1455 Enables exitification optimisation. Implied by -O.
1456 -fexpose-all-unfoldings
1458 Expose all unfoldings, even for very large or recursive func‐
1459 tions.
1460 -ffloat-in
1462 Turn on the float-in transformation. Implied by -O.
1463 -ffull-laziness
1465 Turn on full laziness (floating bindings outwards). Implied by
1466 -O.
1467 -ffun-to-thunk
1469 Allow worker-wrapper to convert a function closure into a thunk
1470 if the function does not use any of its arguments. Off by de‐
1471 fault.
1472 -fignore-asserts
1474 Ignore assertions in the source. Implied by -O.
1475 -fignore-interface-pragmas
1477 Ignore pragmas in interface files. Implied by -O0 only.
1478 -flate-dmd-anal
1480 Run demand analysis again, at the end of the simplification
1481 pipeline
1482 -flate-specialise
1484 Run a late specialisation pass
1485 -fliberate-case
1487 Turn on the liberate-case transformation. Implied by -O2.
1488 -fliberate-case-threshold=⟨n⟩
1490 default: 2000. Set the size threshold for the liberate-case
1491 transformation to ⟨n⟩
1492 -fllvm-pass-vectors-in-regs
1494 Pass vector value in vector registers for function calls
1495 -floopification
1497 Turn saturated self-recursive tail-calls into local jumps in the
1498 generated assembly. Implied by -O.
1499 -fmax-inline-alloc-size=⟨n⟩
1501 default: 128. Set the maximum size of inline array allocations
1502 to ⟨n⟩ bytes (default: 128).
1503 -fmax-inline-memcpy-insns=⟨n⟩
1505 default: 32. Inline memcpy calls if they would generate no more
1506 than ⟨n⟩ pseudo instructions.
1507 -fmax-inline-memset-insns=⟨n⟩
1509 default: 32. Inline memset calls if they would generate no more
1510 than ⟨n⟩ pseudo instructions
1511 -fmax-simplifier-iterations=⟨n⟩
1513 default: 4. Set the max iterations for the simplifier.
1514 -fmax-uncovered-patterns=⟨n⟩
1516 default: 4. Set the maximum number of patterns to display in
1517 warnings about non-exhaustive ones.
1518 -fmax-worker-args=⟨n⟩
1520 default: 10. If a worker has that many arguments, none will be
1521 unpacked anymore.
1522 -fno-opt-coercion
1524 Turn off the coercion optimiser
1525 -fno-pre-inlining
1527 Turn off pre-inlining
1528 -fno-state-hack
1530 Turn off the state hackwhereby any lambda with a real-world
1531 state token as argument is considered to be single-entry. Hence
1532 OK to inline things inside it.
1533 -fomit-interface-pragmas
1535 Don't generate interface pragmas. Implied by -O0 only.
1536 -fomit-yields
1538 Omit heap checks when no allocation is being performed.
1539 -foptimal-applicative-do
1541 Use a slower but better algorithm for ApplicativeDo
1542 -fpedantic-bottoms
1544 Make GHC be more precise about its treatment of bottom (but see
1545 also -fno-state-hack). In particular, GHC will not eta-expand
1546 through a case expression.
1547 -fregs-graph
1549 Use the graph colouring register allocator for register alloca‐
1550 tion in the native code generator. Implied by -O2.
1551 -fregs-iterative
1553 Use the iterative coalescing graph colouring register allocator
1554 in the native code generator.
1555 -fsimpl-tick-factor=⟨n⟩
1557 default: 100. Set the percentage factor for simplifier ticks.
1558 -fsimplifier-phases=⟨n⟩
1560 default: 2. Set the number of phases for the simplifier. Ig‐
1561 nored with -O0.
1562 -fsolve-constant-dicts
1564 When solving constraints, try to eagerly solve super classes us‐
1565 ing available dictionaries.
1566 -fspec-constr
1568 Turn on the SpecConstr transformation. Implied by -O2.
1569 -fspec-constr-count=⟨n⟩
1571 default: 3.* Set to ⟨n⟩ the maximum number of specialisations
1572 that will be created for any one function by the SpecConstr
1573 transformation.
1574 -fspec-constr-keen
1576 Specialize a call with an explicit constructor argument, even if
1577 the argument is not scrutinised in the body of the function
1578 -fspec-constr-threshold=⟨n⟩
1580 default: 2000. Set the size threshold for the SpecConstr trans‐
1581 formation to ⟨n⟩.
1582 -fspecialise
1584 Turn on specialisation of overloaded functions. Implied by -O.
1585 -fspecialise-aggressively
1587 Turn on specialisation of overloaded functions regardless of
1588 size, if unfolding is available
1589 -fstatic-argument-transformation
1591 Turn on the static argument transformation.
1592 -fstg-cse
1594 Enable common sub-expression elimination on the STG intermediate
1595 language
1596 -fstg-lift-lams
1598 Enable late lambda lifting on the STG intermediate language. Im‐
1599 plied by -O2.
1600 -fstg-lift-lams-known
1602 Allow turning known into unknown calls while performing late
1603 lambda lifting.
1604 -fstg-lift-lams-non-rec-args
1606 Create top-level non-recursive functions with at most <n> param‐
1607 eters while performing late lambda lifting.
1608 -fstg-lift-lams-rec-args
1610 Create top-level recursive functions with at most <n> parameters
1611 while performing late lambda lifting.
1612 -fstrictness
1614 Turn on strictness analysis. Implied by -O. Implies
1615 -fworker-wrapper
1616 -fstrictness-before=⟨n⟩
1618 Run an additional strictness analysis before simplifier phase
1619 ⟨n⟩
1620 -funbox-small-strict-fields
1622 Flatten strict constructor fields with a pointer-sized represen‐
1623 tation. Implied by -O.
1624 -funbox-strict-fields
1626 Flatten strict constructor fields
1627 -funfolding-creation-threshold=⟨n⟩
1629 default: 750. Tweak unfolding settings.
1630 -funfolding-dict-discount=⟨n⟩
1632 default: 30. Tweak unfolding settings.
1633 -funfolding-fun-discount=⟨n⟩
1635 default: 60. Tweak unfolding settings.
1636 -funfolding-keeness-factor=⟨n⟩
1638 default: 1.5. Tweak unfolding settings.
1639 -funfolding-use-threshold=⟨n⟩
1641 default: 60. Tweak unfolding settings.
1642 -fworker-wrapper
1644 Enable the worker-wrapper transformation.
1645 Optimization levels
1647 -O Enable level 1 optimisations
1648 -O0 Disable optimisations (default)
1650 -O2 Enable level 2 optimisations
1652 -O⟨n⟩ Any -On where n > 2 is the same as -O2.
1654 Package options
1656 -clear-package-db
1657 Clear the package db stack.
1658 -distrust ⟨pkg⟩
1660 Expose package ⟨pkg⟩ and set it to be distrusted. See
1661 safe-haskell.
1662 -distrust-all-packages
1664 Distrust all packages by default. See safe-haskell.
1665 -fpackage-trust
1667 Enable Safe Haskell trusted package requirement for trustworthy
1668 modules.
1669 -global-package-db
1671 Add the global package db to the stack.
1672 -hide-all-packages
1674 Hide all packages by default
1675 -hide-package ⟨pkg⟩
1677 Hide package ⟨pkg⟩
1678 -ignore-package ⟨pkg⟩
1680 Ignore package ⟨pkg⟩
1681 -no-auto-link-packages
1683 Don't automatically link in the base and rts packages.
1684 -no-global-package-db
1686 Remove the global package db from the stack.
1687 -no-user-package-db
1689 Remove the user's package db from the stack.
1690 -package ⟨pkg⟩
1692 Expose package ⟨pkg⟩
1693 -package-db ⟨file⟩
1695 Add ⟨file⟩ to the package db stack.
1696 -package-env ⟨file⟩|⟨name⟩
1698 Use the specified package environment.
1699 -package-id ⟨unit-id⟩
1701 Expose package by id ⟨unit-id⟩
1702 -this-unit-id ⟨unit-id⟩
1704 Compile to be part of unit (i.e. package) ⟨unit-id⟩
1705 -trust ⟨pkg⟩
1707 Expose package ⟨pkg⟩ and set it to be trusted. See safe-haskell.
1708 -user-package-db
1710 Add the user's package db to the stack.
1711 Phases of compilation
1713 -C Stop after generating C (.hc file)
1714 -c Stop after generating object (.o) file
1716 -E Stop after preprocessing (.hspp file)
1718 -F Enable the use of a pre-processor (set with -pgmF ⟨cmd⟩)
1720 -S Stop after generating assembly (.s file)
1722 -x ⟨suffix⟩
1724 Override default behaviour for source files
1725 Overriding external programs
1727 -pgma ⟨cmd⟩
1728 Use ⟨cmd⟩ as the assembler
1729 -pgmc ⟨cmd⟩
1731 Use ⟨cmd⟩ as the C compiler
1732 -pgmdll ⟨cmd⟩
1734 Use ⟨cmd⟩ as the DLL generator
1735 -pgmF ⟨cmd⟩
1737 Use ⟨cmd⟩ as the pre-processor (with -F only)
1738 -pgmi ⟨cmd⟩
1740 Use ⟨cmd⟩ as the external interpreter command.
1741 -pgminstall_name_tool ⟨cmd⟩
1743 Use ⟨cmd⟩ as the program to inject runpath into mach-o dylibs on
1744 macOS
1745 -pgmL ⟨cmd⟩
1747 Use ⟨cmd⟩ as the literate pre-processor
1748 -pgml ⟨cmd⟩
1750 Use ⟨cmd⟩ as the linker
1751 -pgmlc ⟨cmd⟩
1753 Use ⟨cmd⟩ as the LLVM compiler
1754 -pgmlibtool ⟨cmd⟩
1756 Use ⟨cmd⟩ as the command for libtool (with -staticlib only).
1757 -pgmlm ⟨cmd⟩
1759 Use ⟨cmd⟩ as the linker when merging object files
1760 -pgmlo ⟨cmd⟩
1762 Use ⟨cmd⟩ as the LLVM optimiser
1763 -pgmotool ⟨cmd⟩
1765 Use ⟨cmd⟩ as the program to inspect mach-o dylibs on macOS
1766 -pgmP ⟨cmd⟩
1768 Use ⟨cmd⟩ as the C pre-processor (with -cpp only)
1769 -pgms ⟨cmd⟩
1771 Use ⟨cmd⟩ as the splitter
1772 -pgmwindres ⟨cmd⟩
1774 Use ⟨cmd⟩ as the program for embedding manifests on Windows.
1775 Phase-specific options
1777 -opta ⟨option⟩
1778 pass ⟨option⟩ to the assembler
1779 -optc ⟨option⟩
1781 pass ⟨option⟩ to the C compiler
1782 -optcxx ⟨option⟩
1784 pass ⟨option⟩ to the C++ compiler
1785 -optdll ⟨option⟩
1787 pass ⟨option⟩ to the DLL generator
1788 -optF ⟨option⟩
1790 pass ⟨option⟩ to the custom pre-processor
1791 -opti ⟨option⟩
1793 pass ⟨option⟩ to the interpreter sub-process.
1794 -optL ⟨option⟩
1796 pass ⟨option⟩ to the literate pre-processor
1797 -optl ⟨option⟩
1799 pass ⟨option⟩ to the linker
1800 -optlc ⟨option⟩
1802 pass ⟨option⟩ to the LLVM compiler
1803 -optlm ⟨option⟩
1805 pass ⟨option⟩ to the linker when merging object files.
1806 -optlo ⟨option⟩
1808 pass ⟨option⟩ to the LLVM optimiser
1809 -optP ⟨option⟩
1811 pass ⟨option⟩ to cpp (with -cpp only)
1812 -optwindres ⟨option⟩
1814 pass ⟨option⟩ to windres.
1815 -pgmc-supports-no-pie
1817 Indicate that the C compiler supports -no-pie
1818 Platform-specific options
1820 -mbmi2 (x86 only) Use BMI2 for bit manipulation operations
1821 -msse2 (x86 only) Use SSE2 for floating-point operations
1823 -msse4.2
1825 (x86 only) Use SSE4.2 for floating-point operations
1826 Compiler plugins
1828 -fclear-plugins
1829 Clear the list of active plugins
1830 -fplugin-opt=⟨module⟩:⟨args⟩
1832 Give arguments to a plugin module; module must be specified with
1833 -fplugin=⟨module⟩
1834 -fplugin-trustworthy
1836 Trust the used plugins and no longer mark the compiled module as
1837 unsafe
1838 -fplugin=⟨module⟩
1840 Load a plugin exported by a given module
1841 -hide-all-plugin-packages
1843 Hide all packages for plugins by default
1844 -plugin-package ⟨pkg⟩
1846 Expose ⟨pkg⟩ for plugins
1847 -plugin-package-id ⟨pkg-id⟩
1849 Expose ⟨pkg-id⟩ for plugins
1850 Profiling
1852 -fno-prof-auto
1853 Disables any previous -fprof-auto, -fprof-auto-top, or
1854 -fprof-auto-exported options.
1855 -fno-prof-cafs
1857 Disables any previous -fprof-cafs option.
1858 -fno-prof-count-entries
1860 Do not collect entry counts
1861 -fprof-auto
1863 Auto-add SCC\ s to all bindings not marked INLINE
1864 -fprof-auto-calls
1866 Auto-add SCC\ s to all call sites
1867 -fprof-auto-exported
1869 Auto-add SCC\ s to all exported bindings not marked INLINE
1870 -fprof-auto-top
1872 Auto-add SCC\ s to all top-level bindings not marked INLINE
1873 -fprof-cafs
1875 Auto-add SCC\ s to all CAFs
1876 -prof Turn on profiling
1878 -ticky Turn on ticky-ticky profiling
1880 Program coverage
1882 -fhpc Turn on Haskell program coverage instrumentation
1883 Recompilation checking
1885 -fforce-recomp
1886 Turn off recompilation checking. This is implied by any -ddump-X
1887 option when compiling a single file (i.e. when using -c).
1888 -fignore-hpc-changes
1890 Do not recompile modules just to match changes to HPC flags.
1891 This is especially useful for avoiding recompilation when using
1892 GHCi, and is enabled by default for GHCi.
1893 -fignore-optim-changes
1895 Do not recompile modules just to match changes to optimisation
1896 flags. This is especially useful for avoiding recompilation when
1897 using GHCi, and is enabled by default for GHCi.
1898 Redirecting output
1900 --exclude-module=⟨file⟩
1901 Regard ⟨file⟩ as "stable"; i.e., exclude it from having depen‐
1902 dencies on it.
1903 -ddump-mod-cycles
1905 Dump module cycles
1906 -dep-makefile ⟨file⟩
1908 Use ⟨file⟩ as the makefile
1909 -dep-suffix ⟨suffix⟩
1911 Make dependencies that declare that files with suffix
1912 .⟨suf⟩⟨osuf⟩ depend on interface files with suffix .⟨suf⟩hi
1913 -dumpdir ⟨dir⟩
1915 redirect dump files
1916 -hcsuf ⟨suffix⟩
1918 set the suffix to use for intermediate C files
1919 -hidir ⟨dir⟩
1921 set directory for interface files
1922 -hiedir ⟨dir⟩
1924 set directory for extended interface files
1925 -hiesuf ⟨suffix⟩
1927 set the suffix to use for extended interface files
1928 -hisuf ⟨suffix⟩
1930 set the suffix to use for interface files
1931 -include-cpp-deps
1933 Include preprocessor dependencies
1934 -include-pkg-deps
1936 Regard modules imported from packages as unstable
1937 -o ⟨file⟩
1939 set output filename
1940 -odir ⟨dir⟩
1942 set directory for object files
1943 -ohi ⟨file⟩
1945 set the filename in which to put the interface
1946 -osuf ⟨suffix⟩
1948 set the output file suffix
1949 -outputdir ⟨dir⟩
1951 set output directory
1952 -stubdir ⟨dir⟩
1954 redirect FFI stub files
1955 Temporary files
1957 -tmpdir ⟨dir⟩
1958 set the directory for temporary files
1959 Verbosity options
1961 -fabstract-refinement-hole-fits
1962 default: off. Toggles whether refinements where one or more of
1963 the holes are abstract are reported.
1964 -fdefer-diagnostics
1966 Defer and group diagnostic messages by severity
1967 -fdiagnostics-color=⟨always|auto|never⟩
1969 Use colors in error messages
1970 -fdiagnostics-show-caret
1972 Whether to show snippets of original source code
1973 -ferror-spans
1975 Output full span in error messages
1976 -fhide-source-paths
1978 hide module source and object paths
1979 -fkeep-going
1981 Continue compilation as far as possible on errors
1982 -fmax-refinement-hole-fits=⟨n⟩
1984 default: 6. Set the maximum number of refinement hole fits for
1985 typed holes to display in type error messages.
1986 -fmax-relevant-binds=⟨n⟩
1988 default: 6. Set the maximum number of bindings to display in
1989 type error messages.
1990 -fmax-valid-hole-fits=⟨n⟩
1992 default: 6. Set the maximum number of valid hole fits for typed
1993 holes to display in type error messages.
1994 -fno-show-valid-hole-fits
1996 Disables showing a list of valid hole fits for typed holes in
1997 type error messages.
1998 -fno-sort-valid-hole-fits
2000 Disables the sorting of the list of valid hole fits for typed
2001 holes in type error messages.
2002 -fprint-axiom-incomps
2004 Display equation incompatibilities in closed type families
2005 -fprint-equality-relations
2007 Distinguish between equality relations when printing
2008 -fprint-expanded-synonyms
2010 In type errors, also print type-synonym-expanded types.
2011 -fprint-explicit-coercions
2013 Print coercions in types
2014 -fprint-explicit-foralls
2016 Print explicit forall quantification in types. See also Explic‐
2017 itForAll
2018 -fprint-explicit-kinds
2020 Print explicit kind foralls and kind arguments in types. See
2021 also KindSignatures
2022 -fprint-explicit-runtime-reps
2024 Print RuntimeRep variables in types which are runtime-represen‐
2025 tation polymorphic.
2026 -fprint-potential-instances
2028 display all available instances in type error messages
2029 -fprint-typechecker-elaboration
2031 Print extra information from typechecker.
2032 -fprint-unicode-syntax
2034 Use unicode syntax when printing expressions, types and kinds.
2035 See also UnicodeSyntax
2036 -frefinement-level-hole-fits=⟨n⟩
2038 default: off. Sets the level of refinement of the refinement
2039 hole fits, where level n means that hole fits of up to n holes
2040 will be considered.
2041 -freverse-errors
2043 Output errors in reverse order
2044 -fshow-docs-of-hole-fits
2046 Toggles whether to show the documentation of the valid hole fits
2047 in the output.
2048 -fshow-hole-constraints
2050 Show constraints when reporting typed holes.
2051 -fshow-hole-matches-of-hole-fits
2053 Toggles whether to show the type of the additional holes in re‐
2054 finement hole fits.
2055 -fshow-provenance-of-hole-fits
2057 Toggles whether to show the provenance of the valid hole fits in
2058 the output.
2059 -fshow-type-app-of-hole-fits
2061 Toggles whether to show the type application of the valid hole
2062 fits in the output.
2063 -fshow-type-app-vars-of-hole-fits
2065 Toggles whether to show what type each quantified variable takes
2066 in a valid hole fit.
2067 -fshow-type-of-hole-fits
2069 Toggles whether to show the type of the valid hole fits in the
2070 output.
2071 -funclutter-valid-hole-fits
2073 Unclutter the list of valid hole fits by not showing provenance
2074 nor type applications of suggestions.
2075 -Rghc-timing
2077 Summarise timing stats for GHC (same as +RTS -tstderr).
2078 -v verbose mode (equivalent to -v3)
2080 -v⟨n⟩ set verbosity level
2082 Warnings
2084 -fdefer-out-of-scope-variables
2085 Convert variable out of scope variables errors into warnings.
2086 Implied by -fdefer-type-errors. See also -Wde‐
2087 ferred-out-of-scope-variables.
2088 -fdefer-type-errors
2090 Turn type errors into warnings, deferring the error until run‐
2091 time. Implies -fdefer-typed-holes and -fdefer-out-of-scope-vari‐
2092 ables. See also -Wdeferred-type-errors
2093 -fdefer-typed-holes
2095 Convert typed hole errors into warnings, deferring the error un‐
2096 til runtime. Implied by -fdefer-type-errors. See also
2097 -Wtyped-holes.
2098 -fenable-th-splice-warnings
2100 Generate warnings for Template Haskell splices
2101 -fhelpful-errors
2103 Make suggestions for mis-spelled names.
2104 -fmax-pmcheck-models=⟨n⟩
2106 soft limit on the number of parallel models the pattern match
2107 checker should check a pattern match clause against
2108 -fshow-warning-groups
2110 show which group an emitted warning belongs to.
2111 -fvia-C
2113 use the C code generator
2114 -W enable normal warnings
2116 -w disable all warnings
2118 -Wall enable almost all warnings (details in options-sanity)
2120 -Wall-missed-specialisations
2122 warn when specialisation of any overloaded function fails.
2123 -Wcompat
2125 enable future compatibility warnings (details in options-sanity)
2126 -Wcompat-unqualified-imports
2128 Report unqualified imports of core libraries which are expected
2129 to cause compatibility problems in future releases.
2130 -Wcpp-undef
2132 warn on uses of the #if directive on undefined identifiers
2133 -Wdeferred-out-of-scope-variables
2135 Report warnings when variable out-of-scope errors are deferred
2136 until runtime. See -fdefer-out-of-scope-variables.
2137 -Wdeferred-type-errors
2139 Report warnings when deferred type errors are enabled. This op‐
2140 tion is enabled by default. See -fdefer-type-errors.
2141 -Wdeprecated-flags
2143 warn about uses of commandline flags that are deprecated
2144 -Wdeprecations
2146 warn about uses of functions & types that have warnings or dep‐
2147 recated pragmas. Alias for -Wwarnings-deprecations
2148 -Wderiving-defaults
2150 warn about default deriving when using both DeriveAnyClass and
2151 GeneralizedNewtypeDeriving
2152 -Wdodgy-exports
2154 warn about dodgy exports
2155 -Wdodgy-foreign-imports
2157 warn about dodgy foreign imports
2158 -Wdodgy-imports
2160 warn about dodgy imports
2161 -Wduplicate-constraints
2163 warn when a constraint appears duplicated in a type signature
2164 -Wduplicate-exports
2166 warn when an entity is exported multiple times
2167 -Wempty-enumerations
2169 warn about enumerations that are empty
2170 -Werror
2172 make warnings fatal
2173 -Weverything
2175 enable all warnings supported by GHC
2176 -Whi-shadowing
2178 (deprecated) warn when a .hi file in the current directory shad‐
2179 ows a library
2180 -Widentities
2182 warn about uses of Prelude numeric conversions that are probably
2183 the identity (and hence could be omitted)
2184 -Wimplicit-kind-vars
2186 warn when kind variables are implicitly quantified over.
2187 -Wimplicit-prelude
2189 warn when the Prelude is implicitly imported
2190 -Winaccessible-code
2192 warn about inaccessible code
2193 -Wincomplete-patterns
2195 warn when a pattern match could fail
2196 -Wincomplete-record-updates
2198 warn when a record update could fail
2199 -Wincomplete-uni-patterns
2201 warn when a pattern match in a lambda expression or pattern
2202 binding could fail
2203 -Winline-rule-shadowing
2205 Warn if a rewrite RULE might fail to fire because the function
2206 might be inlined before the rule has a chance to fire. See
2207 rules-inline.
2208 -Wmissed-extra-shared-lib
2210 Warn when GHCi can't load a shared lib.
2211 -Wmissed-specialisations
2213 warn when specialisation of an imported, overloaded function
2214 fails.
2215 -Wmissing-deriving-strategies
2217 warn when a deriving clause is missing a deriving strategy
2218 -Wmissing-export-lists
2220 warn when a module declaration does not explicitly list all ex‐
2221 ports
2222 -Wmissing-exported-signatures
2224 warn about top-level functions without signatures, only if they
2225 are exported. takes precedence over -Wmissing-signatures
2226 -Wmissing-exported-sigs
2228 (deprecated) warn about top-level functions without signatures,
2229 only if they are exported. takes precedence over -Wmissing-sig‐
2230 natures
2231 -Wmissing-fields
2233 warn when fields of a record are uninitialised
2234 -Wmissing-home-modules
2236 warn when encountering a home module imported, but not listed on
2237 the command line. Useful for cabal to ensure GHC won't pick up
2238 modules, not listed neither in exposed-modules, nor in
2239 other-modules.
2240 -Wmissing-import-lists
2242 warn when an import declaration does not explicitly list all the
2243 names brought into scope
2244 -Wmissing-local-signatures
2246 warn about polymorphic local bindings without signatures
2247 -Wmissing-local-sigs
2249 (deprecated) warn about polymorphic local bindings without sig‐
2250 natures
2251 -Wmissing-methods
2253 warn when class methods are undefined
2254 -Wmissing-monadfail-instances
2256 Warn when a failable pattern is used in a do-block that does not
2257 have a MonadFail instance.
2258 -Wmissing-pattern-synonym-signatures
2260 warn when pattern synonyms do not have type signatures
2261 -Wmissing-signatures
2263 warn about top-level functions without signatures
2264 -Wmonomorphism-restriction
2266 warn when the Monomorphism Restriction is applied
2267 -Wname-shadowing
2269 warn when names are shadowed
2270 -Wno-compat
2272 Disables all warnings enabled by -Wcompat.
2273 -Wnoncanonical-monad-instances
2275 warn when Applicative or Monad instances have noncanonical defi‐
2276 nitions of return, pure, (>>), or (*>). See flag description in
2277 options-sanity for more details.
2278 -Wnoncanonical-monadfail-instances
2280 warn when Monad or MonadFail instances have noncanonical defini‐
2281 tions of fail. See flag description in options-sanity for more
2282 details.
2283 -Wnoncanonical-monoid-instances
2285 warn when Semigroup or Monoid instances have noncanonical defi‐
2286 nitions of (<>) or mappend. See flag description in op‐
2287 tions-sanity for more details.
2288 -Worphans
2290 warn when the module contains orphan instance declarations or
2291 rewrite rules
2292 -Woverflowed-literals
2294 warn about literals that will overflow their type
2295 -Woverlapping-patterns
2297 warn about overlapping patterns
2298 -Wpartial-fields
2300 warn when defining a partial record field.
2301 -Wpartial-type-signatures
2303 warn about holes in partial type signatures when PartialTypeSig‐
2304 natures is enabled. Not applicable when PartialTypeSignatures is
2305 not enabled, in which case errors are generated for such holes.
2306 -Wredundant-constraints
2308 Have the compiler warn about redundant constraints in type sig‐
2309 natures.
2310 -Wredundant-record-wildcards
2312 Warn about record wildcard matches when the wildcard binds no
2313 patterns.
2314 -Wsafe warn if the module being compiled is regarded to be safe.
2316 -Wsemigroup
2318 warn when a Monoid is not Semigroup, and on non- Semigroup defi‐
2319 nitions of (<>)?
2320 -Wsimplifiable-class-constraints
2322 Warn about class constraints in a type signature that can be
2323 simplified using a top-level instance declaration.
2324 -Wspace-after-bang
2326 warn for missing space before the second argument of an infix
2327 definition of (!) when BangPatterns are not enabled
2328 -Wstar-binder
2330 warn about binding the (*) type operator despite StarIsType
2331 -Wstar-is-type
2333 warn when * is used to mean Data.Kind.Type
2334 -Wtabs warn if there are tabs in the source file
2336 -Wtrustworthy-safe
2338 warn if the module being compiled is marked as Trustworthy but
2339 it could instead be marked as Safe, a more informative bound.
2340 -Wtype-defaults
2342 warn when defaulting happens
2343 -Wtyped-holes
2345 Report warnings when typed hole errors are deferred until run‐
2346 time. See -fdefer-typed-holes.
2347 -Wunbanged-strict-patterns
2349 warn on pattern bind of unlifted variable that is neither bare
2350 nor banged
2351 -Wunrecognised-pragmas
2353 warn about uses of pragmas that GHC doesn't recognise
2354 -Wunrecognised-warning-flags
2356 throw a warning when an unrecognised -W... flag is encountered
2357 on the command line.
2358 -Wunsafe
2360 warn if the module being compiled is regarded to be unsafe. See
2361 safe-haskell
2362 -Wunsupported-calling-conventions
2364 warn about use of an unsupported calling convention
2365 -Wunsupported-llvm-version
2367 Warn when using -fllvm with an unsupported version of LLVM.
2368 -Wunticked-promoted-constructors
2370 warn if promoted constructors are not ticked
2371 -Wunused-binds
2373 warn about bindings that are unused. Alias for
2374 -Wunused-top-binds, -Wunused-local-binds and -Wunused-pat‐
2375 tern-binds
2376 -Wunused-do-bind
2378 warn about do bindings that appear to throw away values of types
2379 other than ()
2380 -Wunused-foralls
2382 warn about type variables in user-written forall\s that are un‐
2383 used
2384 -Wunused-imports
2386 warn about unnecessary imports
2387 -Wunused-local-binds
2389 warn about local bindings that are unused
2390 -Wunused-matches
2392 warn about variables in patterns that aren't used
2393 -Wunused-packages
2395 warn when package is requested on command line, but was never
2396 loaded.
2397 -Wunused-pattern-binds
2399 warn about pattern match bindings that are unused
2400 -Wunused-record-wildcards
2402 Warn about record wildcard matches when none of the bound vari‐
2403 ables are used.
2404 -Wunused-top-binds
2406 warn about top-level bindings that are unused
2407 -Wunused-type-patterns
2409 warn about unused type variables which arise from patterns in in
2410 type family and data family instances
2411 -Wwarn make warnings non-fatal
2413 -Wwarnings-deprecations
2415 warn about uses of functions & types that have warnings or dep‐
2416 recated pragmas
2417 -Wwrong-do-bind
2419 warn about do bindings that appear to throw away monadic values
2420 that you should have bound instead
2421
2423 Copyright 2015. The University Court of the University of Glasgow. All
2424 rights reserved.
2425
2427 The GHC Team
2428
2430 2021, GHC Team
24318.10.5 Jul 22, 2021 GHC(1)