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 <https://down‐
16 loads.haskell.org/ghc/latest/docs/users_guide.pdf> and HTML
17 <https://downloads.haskell.org/ghc/latest/docs/html/>.
18 Each of GHC's command line options is classified as either static or
20 dynamic. A static flag may only be specified on the command line,
21 whereas a dynamic flag may also be given in an OPTIONS pragma in a
22 source file or set from the GHCi command-line with :set .
23 As a rule of thumb, all the language options are dynamic, as are the
25 warning options and the debugging options.
26 The rest are static, with the notable exceptions of -v, -cpp, -fasm,
28 -fvia-C, -fllvm, and -#include. The OPTIONS sections lists the status
29 of each flag.
30 Common suffixes of file names for Haskell are:
32 .hs Haskell source code; preprocess, compile
34 .lhs literate Haskell source; unlit, preprocess, compile
36 .hi Interface file; contains information about exported symbols
38 .hc intermediate C files
40 .⟨way⟩_o
42 object files for "way" ⟨way⟩; common ways are:
43 dyn dynamically-linked
45 p built with profiling
47 .⟨way⟩_hi
49 interface files for "way" ⟨way⟩; common ways are:
50
52 Code generation
53 -dynamic-too -fasm -fllvm -fbyte-code -fbyte-code-and-ob‐
54 ject-code -fexpose-internal-symbols -fexternal-dynamic-refs
55 -fllvm -fasm -fno-code -fobject-code -fPIC -fPIE -fpre‐
56 fer-byte-code -fwrite-if-simplified-core -fwrite-interface
57 -split-objs
58 Debugging the compiler
60 -dasm-lint -dcmm-lint -dcore-lint -ddisable-js-minifier
61 -ddump-asm -ddump-asm-conflicts -ddump-asm-liveness
62 -ddump-asm-native -ddump-asm-regalloc -ddump-asm-regalloc-stages
63 -ddump-asm-stats -ddump-bcos -ddump-c-backend -ddump-call-arity
64 -ddump-cfg-weights -ddump-cmm -ddump-cmm-caf -ddump-cmm-cbe
65 -ddump-cmm-cfg -ddump-cmm-cps -ddump-cmm-from-stg
66 -ddump-cmm-info -ddump-cmm-opt -ddump-cmm-proc
67 -ddump-cmm-procmap -ddump-cmm-raw -ddump-cmm-sink -ddump-cmm-sp
68 -ddump-cmm-split -ddump-cmm-switch -ddump-cmm-thread-sanitizer
69 -ddump-cmm-verbose -ddump-cmm-verbose-by-proc -ddump-core-stats
70 -ddump-cpr-signatures -ddump-cpranal -ddump-cs-trace -ddump-cse
71 -ddump-debug -ddump-deriv -ddump-ds -ddump-ds-preopt
72 -ddump-ec-trace -ddump-exitify -ddump-faststrings
73 -ddump-file-prefix=⟨str⟩ -ddump-float-in -ddump-foreign
74 -ddump-full-laziness -ddump-float-out -ddump-hie -ddump-hpc
75 -ddump-if-trace -ddump-inlinings -ddump-js -ddump-json
76 -ddump-late-cc -ddump-liberate-case -ddump-llvm -ddump-mod-map
77 -ddump-occur-anal -ddump-opt-cmm -ddump-parsed -ddump-parsed-ast
78 -ddump-prep -ddump-rn -ddump-rn-ast -ddump-rn-stats
79 -ddump-rn-trace -ddump-rtti -ddump-rule-firings
80 -ddump-rule-rewrites -ddump-rules -ddump-simpl -ddump-simpl-it‐
81 erations -ddump-simpl-stats -ddump-simpl-trace -ddump-spec
82 -ddump-spec-constr -ddump-splices -ddump-static-argument-trans‐
83 formation -ddump-stg -ddump-stg-cg -ddump-stg-final
84 -ddump-stg-from-core -ddump-stg-tags -ddump-stg-unarised
85 -ddump-str-signatures -ddump-stranal -ddump-tc -ddump-tc-ast
86 -ddump-tc-trace -ddump-ticked -ddump-timings -ddump-to-file
87 -ddump-types -ddump-verbose-inlinings -ddump-view-pattern-com‐
88 moning -ddump-worker-wrapper -dfaststring-stats -dhex-word-lit‐
89 erals -dinitial-unique=⟨s⟩ -dinline-check=⟨str⟩ -dkeep-comments
90 -dlinear-core-lint -dlint -dno-debug-output -ddebug-output
91 -dno-typeable-binds -dppr-case-as-let -dppr-cols=⟨n⟩ -dppr-debug
92 -dppr-user-length -drule-check=⟨str⟩ -dshow-passes -dstg-lint
93 -dsuppress-all -dsuppress-coercion-types -dsuppress-coercions
94 -dsuppress-core-sizes -dsuppress-idinfo -dsuppress-module-pre‐
95 fixes -dsuppress-stg-free-vars -dsuppress-stg-reps -dsup‐
96 press-ticks -dsuppress-timestamps -dsuppress-type-applications
97 -dsuppress-type-signatures -dsuppress-unfoldings -dsup‐
98 press-uniques -dsuppress-var-kinds -dtag-inference-checks
99 -dth-dec-file -dunique-increment=⟨i⟩ -dverbose-core2core -dver‐
100 bose-stg2stg -falignment-sanitisation -fcatch-nonexhaus‐
101 tive-cases -fcheck-prim-bounds -fcmm-thread-sanitizer -fdis‐
102 tinct-constructor-tables -fdump-with-ways -finfo-table-map
103 -fllvm-fill-undef-with-garbage -fproc-alignment -funopti‐
104 mized-core-for-interpreter -fno-unoptimized-core-for-interpreter
105 -g -g⟨n⟩
106 C pre-processor
108 -cpp -D⟨symbol⟩[=⟨value⟩] -U⟨symbol⟩ -I⟨dir⟩ -U⟨symbol⟩
109 Finding imports
111 -i -i⟨dir⟩[:⟨dir⟩]*
112 Interactive mode
114 -fbreak-on-error -fno-break-on-error -fbreak-on-exception
115 -fno-break-on-exception -fbreak-points -fno-break-points
116 -fghci-hist-size=⟨n⟩ -fghci-leak-check -fno-ghci-leak-check
117 -fimplicit-import-qualified -fno-implicit-import-qualified -flo‐
118 cal-ghci-history -fno-local-ghci-history -fno-it -fno-no-it
119 -fprint-bind-result -fno-print-bind-result
120 -fprint-evld-with-show -fshow-loaded-modules -ghci-script -ig‐
121 nore-dot-ghci -no-ignore-dot-ghci -interactive-print ⟨name⟩
122 Interface files
124 --show-iface ⟨file⟩ -ddump-hi -ddump-hi-diffs -ddump-minimal-im‐
125 ports
126 Keeping intermediate files
128 -keep-hc-file -keep-hc-files -keep-hi-files -no-keep-hi-files
129 -keep-hscpp-file -keep-hscpp-files -keep-llvm-file
130 -keep-llvm-files -keep-o-files -no-keep-o-files -keep-s-file
131 -keep-s-files -keep-tmp-files
132 Language options
134 -XAllowAmbiguousTypes -XApplicativeDo -XArrows -XBangPatterns
135 -XBinaryLiterals -XBlockArguments -XCApiFFI -XConstrainedClass‐
136 Methods -XConstraintKinds -XCPP -XCUSKs -XDataKinds -XDatatype‐
137 Contexts -XDeepSubsumption -XDefaultSignatures -XDeriveAnyClass
138 -XDeriveDataTypeable -XDeriveFoldable -XDeriveFunctor -XDeriveG‐
139 eneric -XDeriveLift -XDeriveTraversable -XDerivingStrategies
140 -XDerivingVia -XDisambiguateRecordFields -XDuplicateRecordFields
141 -XEmptyCase -XEmptyDataDecls -XEmptyDataDeriving -XExisten‐
142 tialQuantification -XExplicitForAll -XExplicitNamespaces -XEx‐
143 tendedDefaultRules -XExtendedLiterals -XFieldSelectors -XFlexi‐
144 bleContexts -XFlexibleInstances -XForeignFunctionInterface
145 -XFunctionalDependencies -XGADTs -XGADTSyntax -XGeneralisedNew‐
146 typeDeriving -XGeneralizedNewtypeDeriving -XGHC2021 -XGHCFor‐
147 eignImportPrim -XHaskell2010 -XHaskell98 -XHexFloatLiterals
148 -XImplicitParams -XImportQualifiedPost -XImpredicativeTypes
149 -XIncoherentInstances -XInstanceSigs -XInterruptibleFFI
150 -XKindSignatures -XLambdaCase -XLexicalNegation -XLiberalType‐
151 Synonyms -XLinearTypes -XMagicHash -XMonadComprehensions
152 -XMonoLocalBinds -XMultiParamTypeClasses -XMultiWayIf -XNamed‐
153 FieldPuns -XNamedWildCards -XNegativeLiterals -XNoImplicitPre‐
154 lude -XNoMonomorphismRestriction -XNondecreasingIndentation
155 -XNoPatternGuards -XNoTraditionalRecordSyntax -XNPlusKPatterns
156 -XNullaryTypeClasses -XNumDecimals -XNumericUnderscores -XOver‐
157 lappingInstances -XOverloadedLabels -XOverloadedLists -XOver‐
158 loadedRecordDot -XOverloadedRecordUpdate -XOverloadedStrings
159 -XPackageImports -XParallelListComp -XPartialTypeSignatures
160 -XPatternSynonyms -XPolyKinds -XPostfixOperators -XQualifiedDo
161 -XQuantifiedConstraints -XQuasiQuotes -XRank2Types -XRankNTypes
162 -XRebindableSyntax -XRecordWildCards -XRecursiveDo -XRoleAnnota‐
163 tions -XSafe -XScopedTypeVariables -XStandaloneDeriving -XStan‐
164 daloneKindSignatures -XStarIsType -XStaticPointers -XStrict
165 -XStrictData -XTemplateHaskell -XTemplateHaskellQuotes -XTrans‐
166 formListComp -XTrustworthy -XTupleSections -XTypeAbstractions
167 -XTypeApplications -XTypeData -XTypeFamilies -XTypeFamilyDepen‐
168 dencies -XTypeInType -XTypeOperators -XTypeSynonymInstances
169 -XUnboxedSums -XUnboxedTuples -XUndecidableInstances -XUndecid‐
170 ableSuperClasses -XUnicodeSyntax -XUnliftedDatatypes -XUnlift‐
171 edFFITypes -XUnliftedNewtypes -XUnsafe -XViewPatterns
172 Linking options
174 -c -debug -dylib-install-name ⟨path⟩ -dynamic -dynload -eventlog
175 -fcompact-unwind -fkeep-cafs -flink-rts -fno-embed-manifest
176 -fno-gen-manifest -fno-shared-implib -framework ⟨name⟩ -frame‐
177 work-path ⟨dir⟩ -fsplit-sections -split-sections -fno-split-sec‐
178 tions -fuse-rpaths -fwhole-archive-hs-libs -L ⟨dir⟩ -l ⟨lib⟩
179 -main-is ⟨thing⟩ -no-hs-main -no-pie -pie -no-rtsopts-sugges‐
180 tions -package ⟨name⟩ -pie -no-pie -rdynamic -rt‐
181 sopts[=⟨none|some|all|ignore|ignoreAll⟩] -shared -sin‐
182 gle-threaded -threaded -static -staticlib -threaded -sin‐
183 gle-threaded -with-rtsopts=⟨opts⟩
184 Miscellaneous options
186 -ddump-mod-cycles -fdefer-out-of-scope-variables -fno-de‐
187 fer-out-of-scope-variables -fdefer-type-errors -fno-de‐
188 fer-type-errors -fdefer-typed-holes -fno-defer-typed-holes -fex‐
189 ternal-interpreter -ffamily-application-cache -fno-family-appli‐
190 cation-cache -fglasgow-exts -fno-glasgow-exts -fno-safe-haskell
191 -ghcversion-file ⟨path to ghcversion.h⟩ -H ⟨size⟩ -hidden-module
192 ⟨module name⟩ -j[⟨n⟩] -jsem -reexported-module ⟨module name⟩
193 -this-package-name ⟨unit-id⟩ -unit @⟨filename⟩ -working-dir
194 ⟨dir⟩
195 Modes of operation
197 --frontend ⟨module⟩ --help -? --info --interactive --make --nu‐
198 meric-version --print-booter-version --print-build-platform
199 --print-c-compiler-flags --print-c-compiler-link-flags
200 --print-debug-on --print-global-package-db --print-have-inter‐
201 preter --print-have-native-code-generator --print-host-platform
202 --print-ld-flags --print-leading-underscore --print-libdir
203 --print-object-splitting-supported --print-project-git-commit-id
204 --print-project-version --print-rts-ways --print-stage
205 --print-support-smp --print-tables-next-to-code --print-tar‐
206 get-platform --print-unregisterised --run ⟨file⟩ --show-iface
207 ⟨file⟩ --show-options --supported-extensions --supported-lan‐
208 guages --version -V -e ⟨expr⟩ -M -shared
209 Individual optimizations
211 -fasm-shortcutting -fno-asm-shortcutting -fbinary-blob-thresh‐
212 old=⟨n⟩ -fblock-layout-cfg -fno-block-layout-cfg -fblock-lay‐
213 out-weightless -fno-block-layout-weightless -fblock-lay‐
214 out-weights -fcall-arity -fno-call-arity -fcase-folding
215 -fno-case-folding -fcase-merge -fno-case-merge -fcmm-con‐
216 trol-flow -fno-cmm-control-flow -fcmm-elim-common-blocks
217 -fno-cmm-elim-common-blocks -fcmm-sink -fno-cmm-sink
218 -fcmm-static-pred -fno-cmm-static-pred -fcore-constant-folding
219 -fno-core-constant-folding -fcpr-anal -fno-cpr-anal -fcross-mod‐
220 ule-specialise -fno-cross-module-specialise -fcse -fno-cse
221 -fdicts-cheap -fno-dicts-cheap -fdicts-strict -fno-dicts-strict
222 -fdmd-tx-dict-sel -fno-dmd-tx-dict-sel -fdmd-unbox-width=⟨n⟩
223 -fdo-eta-reduction -fno-do-eta-reduction -fdo-lambda-eta-expan‐
224 sion -fno-do-lambda-eta-expansion -feager-blackholing -fen‐
225 able-rewrite-rules -fno-enable-rewrite-rules -fexcess-precision
226 -fno-excess-precision -fexitification -fno-exitification -fex‐
227 pose-all-unfoldings -fno-expose-all-unfoldings -ffloat-in
228 -fno-float-in -ffull-laziness -fno-full-laziness -ffun-to-thunk
229 -fno-fun-to-thunk -fignore-asserts -fno-ignore-asserts -fig‐
230 nore-interface-pragmas -fno-ignore-interface-pragmas -fin‐
231 line-generics -fno-inline-generics -finline-generics-aggres‐
232 sively -fno-inline-generics-aggressively -flate-dmd-anal
233 -fno-late-dmd-anal -flate-specialise -fno-late-specialise -flib‐
234 erate-case -fno-liberate-case -fliberate-case-threshold=⟨n⟩
235 -fno-liberate-case-threshold -fllvm-pass-vectors-in-regs -flo‐
236 cal-float-out -fno-local-float-out -flocal-float-out-top-level
237 -fno-local-float-out-top-level -floopification -fno-loopifica‐
238 tion -fmax-inline-alloc-size=⟨n⟩ -fmax-inline-memcpy-insns=⟨n⟩
239 -fmax-inline-memset-insns=⟨n⟩ -fmax-simplifier-iterations=⟨n⟩
240 -fmax-uncovered-patterns=⟨n⟩ -fmax-worker-args=⟨n⟩ -fno-opt-co‐
241 ercion -fno-pre-inlining -fno-state-hack -fomit-interface-prag‐
242 mas -fno-omit-interface-pragmas -fomit-yields -fno-omit-yields
243 -foptimal-applicative-do -fno-optimal-applicative-do -fpedan‐
244 tic-bottoms -fno-pedantic-bottoms -fpolymorphic-specialisation
245 -fno-polymorphic-specialisation -fregs-graph -fno-regs-graph
246 -fregs-iterative -fno-regs-iterative -fsimpl-tick-factor=⟨n⟩
247 -fsimplifier-phases=⟨n⟩ -fsolve-constant-dicts -fno-solve-con‐
248 stant-dicts -fspec-constr -fno-spec-constr -fspec-con‐
249 str-count=⟨n⟩ -fno-spec-constr-count -fspec-constr-keen
250 -fno-spec-constr-keen -fspec-constr-threshold=⟨n⟩ -fno-spec-con‐
251 str-threshold -fspecialise -fno-specialise -fspecialise-aggres‐
252 sively -fno-specialise-aggressively -fspecialise-incoherents
253 -fno-specialise-incoherents -fstatic-argument-transformation
254 -fno-static-argument-transformation -fstg-cse -fno-stg-cse
255 -fstg-lift-lams -fno-stg-lift-lams -fstg-lift-lams-known
256 -fno-stg-lift-lams-known -fstg-lift-lams-non-rec-args
257 -fstg-lift-lams-non-rec-args-any -fstg-lift-lams-rec-args
258 -fstg-lift-lams-rec-args-any -fstrictness -fno-strictness
259 -fstrictness-before=⟨n⟩ -funbox-small-strict-fields -fno-un‐
260 box-small-strict-fields -funbox-strict-fields -fno-un‐
261 box-strict-fields -funfolding-case-scaling=⟨n⟩ -funfold‐
262 ing-case-threshold=⟨n⟩ -funfolding-creation-threshold=⟨n⟩ -fun‐
263 folding-dict-discount=⟨n⟩ -funfolding-fun-discount=⟨n⟩ -funfold‐
264 ing-keeness-factor=⟨n⟩ -funfolding-use-threshold=⟨n⟩
265 -fworker-wrapper -fworker-wrapper-cbv
266 Optimization levels
268 -O -O1 -O0 -O0 -O2 -O0 -O⟨n⟩ -O0
269 Package options
271 -clear-package-db -distrust ⟨pkg⟩ -distrust-all-packages -fpack‐
272 age-trust -global-package-db -hide-all-packages -hide-package
273 ⟨pkg⟩ -ignore-package ⟨pkg⟩ -no-auto-link-packages
274 -no-global-package-db -no-user-package-db -package ⟨pkg⟩ -pack‐
275 age-db ⟨file⟩ -package-env ⟨file⟩|⟨name⟩ -package-id ⟨unit-id⟩
276 -this-unit-id ⟨unit-id⟩ -trust ⟨pkg⟩ -user-package-db
277 Phases of compilation
279 --merge-objs -C -c -E -F -S -x ⟨suffix⟩
280 Overriding external programs
282 -pgma ⟨cmd⟩ -pgmc ⟨cmd⟩ -pgmcxx ⟨cmd⟩ -pgmdll ⟨cmd⟩ -pgmF ⟨cmd⟩
283 -pgmi ⟨cmd⟩ -pgminstall_name_tool ⟨cmd⟩ -pgmL ⟨cmd⟩ -pgml ⟨cmd⟩
284 -pgmlc ⟨cmd⟩ -pgmlm ⟨cmd⟩ -pgmlo ⟨cmd⟩ -pgmotool ⟨cmd⟩ -pgmP
285 ⟨cmd⟩ -pgms ⟨cmd⟩ -pgmwindres ⟨cmd⟩
286 Phase-specific options
288 -opta ⟨option⟩ -optc ⟨option⟩ -optcxx ⟨option⟩ -optF ⟨option⟩
289 -opti ⟨option⟩ -optL ⟨option⟩ -optl ⟨option⟩ -optlc ⟨option⟩
290 -optlm ⟨option⟩ -optlo ⟨option⟩ -optP ⟨option⟩ -optwindres ⟨op‐
291 tion⟩ -pgmc-supports-no-pie -pgml-supports-no-pie
292 Platform-specific options
294 -mavx -mavx2 -mavx512cd -mavx512er -mavx512f -mavx512pf -mbmi
295 -mbmi2 -mfma -msse -msse2 -msse3 -msse4 -msse4.2
296 Compiler plugins
298 -fclear-plugins -fplugin-library=⟨file-path⟩;⟨unit-id⟩;⟨mod‐
299 ule⟩;⟨args⟩ -fplugin-opt=⟨module⟩:⟨args⟩ -fplugin-trustworthy
300 -fplugin=⟨module⟩ -hide-all-plugin-packages -plugin-package
301 ⟨pkg⟩ -plugin-package-id ⟨pkg-id⟩
302 Profiling
304 -auto -auto-all -caf-all -fno-prof-count-entries
305 -fprof-count-entries -fprof-auto -fno-prof-auto
306 -fprof-auto-calls -fno-prof-auto -fprof-auto-exported
307 -fno-prof-auto -fprof-auto-top -fno-prof-auto -fprof-cafs
308 -fno-prof-cafs -fprof-callers=⟨name⟩ -fprof-late -fno-prof-late
309 -fprof-late-inline -fno-prof-late-inline -fprof-manual
310 -fno-prof-manual -no-auto -no-auto-all -no-caf-all -prof -ticky
311 -ticky-allocd -ticky-ap-thunk -ticky-dyn-thunk -ticky-LNE
312 -ticky-tag-checks
313 Program coverage
315 -fhpc -hpcdir⟨dir⟩
316 Recompilation checking
318 -exclude-module=⟨file⟩ -fforce-recomp -fno-force-recomp -fig‐
319 nore-hpc-changes -fno-ignore-hpc-changes -fignore-optim-changes
320 -fno-ignore-optim-changes -include-cpp-deps -include-pkg-deps
321 Redirecting output
323 -dep-makefile ⟨file⟩ -dep-suffix ⟨suffix⟩ -dumpdir ⟨dir⟩ -dyn‐
324 hisuf ⟨suffix⟩ -dyno ⟨file⟩ -dynohi ⟨file⟩ -dynosuf ⟨suffix⟩
325 -hcsuf ⟨suffix⟩ -hidir ⟨dir⟩ -hiedir ⟨dir⟩ -hiesuf ⟨suffix⟩
326 -hisuf ⟨suffix⟩ -o ⟨file⟩ -odir ⟨dir⟩ -ohi ⟨file⟩ -osuf ⟨suffix⟩
327 -outputdir ⟨dir⟩ -stubdir ⟨dir⟩
328 Temporary files
330 -tmpdir ⟨dir⟩
331 Verbosity options
333 -fabstract-refinement-hole-fits -fno-abstract-refine‐
334 ment-hole-fits -fdefer-diagnostics -fdiagnostics-color=⟨al‐
335 ways|auto|never⟩ -fdiagnostics-show-caret -fno-diagnos‐
336 tics-show-caret -ferror-spans -fhide-source-paths -fkeep-going
337 -fmax-refinement-hole-fits=⟨n⟩ -fno-max-refinement-hole-fits
338 -fmax-relevant-binds=⟨n⟩ -fno-max-relevant-binds
339 -fmax-valid-hole-fits=⟨n⟩ -fno-max-valid-hole-fits
340 -fno-show-valid-hole-fits -fno-sort-valid-hole-fits
341 -fsort-valid-hole-fits -fprint-axiom-incomps -fno-print-ax‐
342 iom-incomps -fprint-equality-relations -fno-print-equality-rela‐
343 tions -fprint-expanded-synonyms -fno-print-expanded-synonyms
344 -fprint-explicit-coercions -fno-print-explicit-coercions
345 -fprint-explicit-foralls -fno-print-explicit-foralls -fprint-ex‐
346 plicit-kinds -fno-print-explicit-kinds -fprint-explicit-run‐
347 time-reps -fno-print-explicit-runtime-reps -fprint-potential-in‐
348 stances -fno-print-potential-instances -fprint-redundant-promo‐
349 tion-ticks -fno-print-redundant-promotion-ticks -fprint-type‐
350 checker-elaboration -fno-print-typechecker-elaboration
351 -fprint-unicode-syntax -fno-print-unicode-syntax -frefine‐
352 ment-level-hole-fits=⟨n⟩ -fno-refinement-level-hole-fits -fre‐
353 verse-errors -fno-reverse-errors -fshow-docs-of-hole-fits
354 -fno-show-docs-of-hole-fits -fshow-error-context -fno-show-er‐
355 ror-context -fshow-hole-constraints
356 -fshow-hole-matches-of-hole-fits
357 -fno-show-hole-matches-of-hole-fits -fshow-prove‐
358 nance-of-hole-fits -fno-show-provenance-of-hole-fits
359 -fshow-type-app-of-hole-fits -fno-show-type-app-of-hole-fits
360 -fshow-type-app-vars-of-hole-fits
361 -fno-show-type-app-vars-of-hole-fits -fshow-type-of-hole-fits
362 -fno-show-type-of-hole-fits -fsort-by-size-hole-fits
363 -fno-sort-by-size-hole-fits -fsort-by-subsumption-hole-fits
364 -fno-sort-by-subsumption-hole-fits -funclutter-valid-hole-fits
365 -Rghc-timing -v -v⟨n⟩
366 Warnings
368 -fenable-th-splice-warnings -fno-enable-th-splice-warnings
369 -fhelpful-errors -fno-helpful-errors -fmax-pmcheck-models=⟨n⟩
370 -fshow-warning-groups -fno-show-warning-groups -fvia-C -W
371 -Wno-extra -w -Wall -Wno-all -Wall-missed-specialisations
372 -Wno-all-missed-specialisations -Wall-missed-specializations
373 -Wno-all-missed-specializations -Wambiguous-fields -Wauto-or‐
374 phans -Wcompat -Wno-compat -Wcompat-unqualified-imports
375 -Wno-compat-unqualified-imports -Wcpp-undef -Wdefault -Wno-de‐
376 fault -Wdeferred-out-of-scope-variables -Wno-de‐
377 ferred-out-of-scope-variables -Wdeferred-type-errors -Wno-de‐
378 ferred-type-errors -Wdeprecated-flags -Wno-deprecated-flags
379 -Wdeprecations -Wno-deprecations -Wderiving-defaults -Wno-deriv‐
380 ing-defaults -Wderiving-typeable -Wno-deriving-typeable
381 -Wdodgy-exports -Wno-dodgy-exports -Wdodgy-foreign-imports
382 -Wno-dodgy-foreign-imports -Wdodgy-imports -Wno-dodgy-imports
383 -Wduplicate-constraints -Wno-duplicate-constraints -Wdupli‐
384 cate-exports -Wno-duplicate-exports -Wempty-enumerations
385 -Wno-empty-enumerations -Werror -Wwarn -Weverything -w -Wex‐
386 tended-warnings -Wno-extended-warnings -Wextra -Wno-extra
387 -Wforall-identifier -Wno-forall-identifier -Wgadt-mono-lo‐
388 cal-binds -Wno-gadt-mono-local-binds -Whi-shadowing
389 -Wno-hi-shadowing -Widentities -Wno-identities -Wim‐
390 plicit-kind-vars -Wno-implicit-kind-vars -Wimplicit-lift
391 -Wno-implicit-lift -Wimplicit-prelude -Wno-implicit-prelude
392 -Wimplicit-rhs-quantification -Wno-implicit-rhs-quantification
393 -Winaccessible-code -Wno-inaccessible-code -Wincomplete-ex‐
394 port-warnings -Wno-incomplete-export-warnings -Wincomplete-pat‐
395 terns -Wno-incomplete-patterns -Wincomplete-record-updates
396 -Wno-incomplete-record-updates -Wincomplete-uni-patterns
397 -Wno-incomplete-uni-patterns -Winconsistent-flags -Wno-inconsis‐
398 tent-flags -Winconsistent-flags -Wno-inconsistent-flags -Win‐
399 ferred-safe-imports -Wno-inferred-safe-imports -Win‐
400 line-rule-shadowing -Wno-inline-rule-shadowing -Winvalid-haddock
401 -Wno-invalid-haddock -Wloopy-superclass-solve -Wno-loopy-super‐
402 class-solve -Wmisplaced-pragmas -Wno-misplaced-pragmas
403 -Wmissed-extra-shared-lib -Wno-missed-extra-shared-lib
404 -Wmissed-specialisations -Wno-missed-specialisations
405 -Wmissed-specializations -Wno-missed-specializations -Wmiss‐
406 ing-deriving-strategies -Wno-missing-deriving-strategies -Wmiss‐
407 ing-export-lists -Wno-missing-export-lists -Wmissing-ex‐
408 ported-pattern-synonym-signatures -Wno-missing-exported-pat‐
409 tern-synonym-signatures -Wmissing-exported-signatures -Wno-miss‐
410 ing-exported-signatures -Wmissing-exported-sigs -Wno-missing-ex‐
411 ported-sigs -Wmissing-fields -Wno-missing-fields -Wmiss‐
412 ing-home-modules -Wno-missing-home-modules -Wmissing-im‐
413 port-lists -Wno-missing-import-lists -Wmissing-kind-signatures
414 -Wno-missing-kind-signatures -Wmissing-local-signatures
415 -Wno-missing-local-signatures -Wmissing-local-sigs -Wno-miss‐
416 ing-local-sigs -Wmissing-methods -Wno-missing-methods -Wmiss‐
417 ing-monadfail-instances -Wno-missing-monadfail-instances -Wmiss‐
418 ing-pattern-synonym-signatures -Wno-missing-pattern-synonym-sig‐
419 natures -Wmissing-poly-kind-signatures -Wno-miss‐
420 ing-poly-kind-signatures -Wmissing-role-annotations
421 -Wno-role-annotations-signatures -Wmissing-safe-haskell-mode
422 -Wno-missing-safe-haskell-mode -Wmissing-signatures -Wno-miss‐
423 ing-signatures -Wmissing-space-after-bang -Wmonomorphism-re‐
424 striction -Wno-monomorphism-restriction -Wname-shadowing
425 -Wno-name-shadowing -Wnoncanonical-monad-instances -Wno-non‐
426 canonical-monad-instances -Wnoncanonical-monadfail-instances
427 -Wno-noncanonical-monadfail-instances -Wnoncanonical-monoid-in‐
428 stances -Wno-noncanonical-monoid-instances -Wnot -Wopera‐
429 tor-whitespace -Wno-operator-whitespace -Woperator-white‐
430 space-ext-conflict -Wno-operator-whitespace-ext-conflict -Wor‐
431 phans -Wno-orphans -Woverflowed-literals -Wno-overflowed-liter‐
432 als -Woverlapping-patterns -Wno-overlapping-patterns -Wpar‐
433 tial-fields -Wno-partial-fields -Wpartial-type-signatures
434 -Wno-partial-type-signatures -Wprepositive-qualified-module
435 -Wno-prepositive-qualified-module -Wredundant-bang-patterns
436 -Wno-redundant-bang-patterns -Wredundant-constraints -Wno-redun‐
437 dant-constraints -Wredundant-record-wildcards -Wno-redun‐
438 dant-record-wildcards -Wredundant-strictness-flags -Wno-redun‐
439 dant-strictness-flags -Wsafe -Wno-safe -Wsemigroup -Wno-semi‐
440 group -Wsimplifiable-class-constraints -Wno-simplifi‐
441 able-class-constraints -Wstar-binder -Wno-star-binder
442 -Wstar-is-type -Wno-star-is-type -Wtabs -Wno-tabs -Wterm-vari‐
443 able-capture -Wtrustworthy-safe -Wno-safe -Wtype-defaults
444 -Wno-type-defaults -Wtype-equality-out-of-scope -Wno-type-equal‐
445 ity-out-of-scope -Wtype-equality-requires-operators
446 -Wno-type-equality-requires-operators -Wtyped-holes
447 -Wno-typed-holes -Wunbanged-strict-patterns -Wno-un‐
448 banged-strict-patterns -Wunicode-bidirectional-format-characters
449 -Wunrecognised-pragmas -Wno-unrecognised-pragmas -Wunrecog‐
450 nised-warning-flags -Wno-unrecognised-warning-flags -Wunsafe
451 -Wno-unsafe -Wunsupported-calling-conventions -Wno-unsup‐
452 ported-calling-conventions -Wunsupported-llvm-version -Wno-un‐
453 supported-llvm-version -Wunticked-promoted-constructors
454 -Wno-unticked-promoted-constructors -Wunused-binds -Wno-un‐
455 used-binds -Wunused-do-bind -Wno-unused-do-bind -Wunused-foralls
456 -Wno-unused-foralls -Wunused-imports -Wno-unused-imports
457 -Wunused-local-binds -Wno-unused-local-binds -Wunused-matches
458 -Wno-unused-matches -Wunused-packages -Wno-unused-packages
459 -Wunused-pattern-binds -Wno-unused-pattern-binds
460 -Wunused-record-wildcards -Wno-unused-record-wildcards
461 -Wunused-top-binds -Wno-unused-top-binds -Wunused-type-patterns
462 -Wno-unused-type-patterns -Wwarn -Werror -Wwarnings-deprecations
463 -Wno-warnings-deprecations -Wwrong-do-bind -Wno-wrong-do-bind
464 -Wx-⟨category⟩ -Wno-x-⟨category⟩
465 Code generation
467 -dynamic-too
468 Build dynamic object files as well as static object files during
469 compilation
470 -fasm Use the native code generator
472 -fbyte-code
474 Generate byte-code
475 -fbyte-code-and-object-code
477 Generate object code and byte-code
478 -fexpose-internal-symbols
480 Produce symbols for all functions, including internal functions.
481 -fexternal-dynamic-refs
483 Generate code for linking against dynamic libraries
484 -fllvm Compile using the LLVM code generator
486 -fno-code
488 Omit code generation
489 -fobject-code
491 Generate object code
492 -fPIC Generate position-independent code (where available)
494 -fPIE Generate code for a position-independent executable (where
496 available)
497 -fprefer-byte-code
499 Use byte-code if it is available to evaluate TH splices
500 -fwrite-if-simplified-core
502 Write an interface file containing the simplified core of the
503 module.
504 -fwrite-interface
506 Always write interface files
507 -split-objs
509 Split generated object files into smaller files
510 Debugging the compiler
512 -dasm-lint
513 ASM pass sanity checking
514 -dcmm-lint
516 C-\- pass sanity checking
517 -dcore-lint
519 Turn on internal sanity checking
520 -ddisable-js-minifier
522 Generate pretty-printed JavaScript code instead of minified
523 (compacted) code.
524 -ddump-asm
526 Dump final assembly
527 -ddump-asm-conflicts
529 Dump register conflicts from the register allocator.
530 -ddump-asm-liveness
532 Dump assembly augmented with register liveness
533 -ddump-asm-native
535 Dump initial assembly
536 -ddump-asm-regalloc
538 Dump the result of register allocation
539 -ddump-asm-regalloc-stages
541 Dump the build/spill stages of the -fregs-graph register alloca‐
542 tor.
543 -ddump-asm-stats
545 Dump statistics from the register allocator.
546 -ddump-bcos
548 Dump interpreter byte code
549 -ddump-c-backend
551 Dump C code produced by the C (unregisterised) backend.
552 -ddump-call-arity
554 Dump output of the call arity analysis pass.
555 -ddump-cfg-weights
557 Dump the assumed weights of the CFG.
558 -ddump-cmm
560 Dump the final C-\- output
561 -ddump-cmm-caf
563 Dump the results of the C-\- CAF analysis pass.
564 -ddump-cmm-cbe
566 Dump the results of common block elimination
567 -ddump-cmm-cfg
569 Dump the results of the C-\- control flow optimisation pass.
570 -ddump-cmm-cps
572 Dump the results of the CPS pass
573 -ddump-cmm-from-stg
575 Dump STG-to-C-\- output
576 -ddump-cmm-info
578 Dump the results of the C-\- info table augmentation pass.
579 -ddump-cmm-opt
581 Dump the results of C-\- to C-\- optimising passes
582 -ddump-cmm-proc
584 Dump the results of proc-point analysis
585 -ddump-cmm-procmap
587 Dump the results of the C-\- proc-point map pass.
588 -ddump-cmm-raw
590 Dump raw C-\-
591 -ddump-cmm-sink
593 Dump the results of the C-\- sinking pass.
594 -ddump-cmm-sp
596 Dump the results of the C-\- stack layout pass.
597 -ddump-cmm-split
599 Dump the results of the C-\- proc-point splitting pass.
600 -ddump-cmm-switch
602 Dump the results of switch lowering passes
603 -ddump-cmm-thread-sanitizer
605 Dump the results of the C-\- ThreadSanitizer elaboration pass.
606 -ddump-cmm-verbose
608 Write output from main C-\- pipeline passes to files
609 -ddump-cmm-verbose-by-proc
611 Show output from main C-\- pipeline passes (grouped by proc)
612 -ddump-core-stats
614 Print a one-line summary of the size of the Core program at the
615 end of the optimisation pipeline
616 -ddump-cpr-signatures
618 Dump CPR signatures
619 -ddump-cpranal
621 Dump CPR analysis output
622 -ddump-cs-trace
624 Trace constraint solver
625 -ddump-cse
627 Dump CSE output
628 -ddump-debug
630 Dump generated DWARF debug information
631 -ddump-deriv
633 Dump deriving output
634 -ddump-ds
636 Dump desugarer output.
637 -ddump-ec-trace
639 Trace exhaustiveness checker
640 -ddump-exitify
642 Dump output of the exitification pass.
643 -ddump-faststrings
645 Dump the whole FastString table when finished
646 -ddump-file-prefix=⟨str⟩
648 Set the prefix of the filenames used for debugging output.
649 -ddump-float-in
651 Dump float in output
652 -ddump-foreign
654 Dump foreign export stubs
655 -ddump-full-laziness
657 Dump full laziness pass output
658 -ddump-hie
660 Dump the hie file syntax tree
661 -ddump-hpc
663 An alias for -ddump-ticked.
664 -ddump-if-trace
666 Trace interface files
667 -ddump-inlinings
669 Dump inlinings performed by the simplifier.
670 -ddump-js
672 Dump final JavaScript code
673 -ddump-json
675 Dump error messages as JSON documents
676 -ddump-late-cc
678 Dump core with late cost centres added
679 -ddump-liberate-case
681 Dump liberate case output
682 -ddump-llvm
684 Dump LLVM intermediate code.
685 -ddump-mod-map
687 Dump the state of the module mapping database.
688 -ddump-occur-anal
690 Dump occurrence analysis output
691 -ddump-opt-cmm
693 Dump the results of C-\- to C-\- optimising passes
694 -ddump-parsed
696 Dump parse tree
697 -ddump-parsed-ast
699 Dump parser output as a syntax tree
700 -ddump-prep
702 Dump prepared core
703 -ddump-rn
705 Dump renamer output
706 -ddump-rn-ast
708 Dump renamer output as a syntax tree
709 -ddump-rn-stats
711 Renamer stats
712 -ddump-rn-trace
714 Trace renamer
715 -ddump-rtti
717 Trace runtime type inference
718 -ddump-rule-firings
720 Dump rule firing info
721 -ddump-rule-rewrites
723 Dump detailed rule firing info
724 -ddump-rules
726 Dump rewrite rules
727 -ddump-simpl
729 Dump final simplifier output
730 -ddump-simpl-iterations
732 Dump output from each simplifier iteration
733 -ddump-simpl-stats
735 Dump simplifier stats
736 -ddump-simpl-trace
738 Dump trace messages in simplifier
739 -ddump-spec
741 Dump specialiser output
742 -ddump-spec-constr
744 Dump specialiser output from SpecConstr
745 -ddump-splices
747 Dump TH spliced expressions, and what they evaluate to
748 -ddump-static-argument-transformation
750 Dump static argument transformation output
751 -ddump-stg
753 (deprecated) Alias for -ddump-stg-from-core
754 -ddump-stg-cg
756 Show output after Stg2Stg
757 -ddump-stg-final
759 Show output of last STG pass.
760 -ddump-stg-from-core
762 Show CoreToStg output
763 -ddump-stg-tags
765 Show output of the tag inference pass.
766 -ddump-stg-unarised
768 Show unarised STG
769 -ddump-str-signatures
771 Dump top-level demand signatures
772 -ddump-stranal
774 Dump demand analysis output
775 -ddump-tc
777 Dump typechecker output
778 -ddump-tc-ast
780 Dump typechecker output as a syntax tree
781 -ddump-tc-trace
783 Trace typechecker
784 -ddump-ticked
786 Dump the code instrumented by HPC (Observing Code Coverage).
787 -ddump-timings
789 Dump per-pass timing and allocation statistics
790 -ddump-to-file
792 Dump to files instead of stdout
793 -ddump-types
795 Dump type signatures
796 -ddump-verbose-inlinings
798 Dump all considered inlinings
799 -ddump-view-pattern-commoning
801 Dump commoned view patterns
802 -ddump-worker-wrapper
804 Dump worker-wrapper output
805 -dfaststring-stats
807 Show statistics for fast string usage when finished
808 -dhex-word-literals
810 Print values of type Word# in hexadecimal.
811 -dinitial-unique=⟨s⟩
813 Start UniqSupply allocation from ⟨s⟩.
814 -dinline-check=⟨str⟩
816 Dump information about inlining decisions
817 -dkeep-comments
819 Include comments in the parser. Useful in combination with
820 -ddump-parsed-ast.
821 -dlinear-core-lint
823 Turn on internal sanity checking
824 -dlint Enable several common internal sanity checkers
826 -dno-debug-output
828 Suppress unsolicited debugging output
829 -dno-typeable-binds
831 Don't generate bindings for Typeable methods
832 -dppr-case-as-let
834 Print single alternative case expressions as strict lets.
835 -dppr-cols=⟨n⟩
837 Set the width of debugging output. For example -dppr-cols200
838 -dppr-debug
840 Turn on debug printing (more verbose)
841 -dppr-user-length
843 Set the depth for printing expressions in error msgs
844 -drule-check=⟨str⟩
846 Dump information about potential rule application
847 -dshow-passes
849 Print out each pass name as it happens
850 -dstg-lint
852 STG pass sanity checking
853 -dsuppress-all
855 In dumps, suppress everything (except for uniques) that is sup‐
856 pressible.
857 -dsuppress-coercion-types
859 Suppress the printing of coercion types in Core dumps to make
860 them shorter
861 -dsuppress-coercions
863 Suppress the printing of coercions in Core dumps to make them
864 shorter
865 -dsuppress-core-sizes
867 Suppress the printing of core size stats per binding (since 9.4)
868 -dsuppress-idinfo
870 Suppress extended information about identifiers where they are
871 bound
872 -dsuppress-module-prefixes
874 Suppress the printing of module qualification prefixes
875 -dsuppress-stg-free-vars
877 Suppress the printing of closure free variable lists in STG out‐
878 put
879 -dsuppress-stg-reps
881 Suppress rep annotations on STG args.
882 -dsuppress-ticks
884 Suppress "ticks" in the pretty-printer output.
885 -dsuppress-timestamps
887 Suppress timestamps in dumps
888 -dsuppress-type-applications
890 Suppress type applications
891 -dsuppress-type-signatures
893 Suppress type signatures
894 -dsuppress-unfoldings
896 Suppress the printing of the stable unfolding of a variable at
897 its binding site
898 -dsuppress-uniques
900 Suppress the printing of uniques in debug output (easier to use
901 diff)
902 -dsuppress-var-kinds
904 Suppress the printing of variable kinds
905 -dtag-inference-checks
907 Affirm tag inference results are correct at runtime.
908 -dth-dec-file
910 Dump evaluated TH declarations into *.th.hs files
911 -dunique-increment=⟨i⟩
913 Set the increment for the generated Unique's to ⟨i⟩.
914 -dverbose-core2core
916 Show output from each core-to-core pass
917 -dverbose-stg2stg
919 Show output from each STG-to-STG pass
920 -falignment-sanitisation
922 Compile with alignment checks for all info table dereferences.
923 -fcatch-nonexhaustive-cases
925 Add a default error alternative to case expressions without a
926 default alternative.
927 -fcheck-prim-bounds
929 Instrument array primops with bounds checks.
930 -fcmm-thread-sanitizer
932 Enable ThreadSanitizer instrumentation of memory accesses.
933 -fdistinct-constructor-tables
935 Generate a fresh info table for each usage of a data construc‐
936 tor.
937 -fdump-with-ways
939 Include the tag of the enabled ways in the extension of dump
940 files.
941 -finfo-table-map
943 Embed a lookup table in the generated binary which maps the ad‐
944 dress of an info table to the source position the closure origi‐
945 nated from.
946 -fllvm-fill-undef-with-garbage
948 Intruct LLVM to fill dead STG registers with garbage
949 -fproc-alignment
951 Align functions at given boundary.
952 -funoptimized-core-for-interpreter
954 Disable optimizations with the interpreter
955 -g Produce DWARF debug information in compiled object files. ⟨n⟩
957 can be 0, 1, or 2, with higher numbers producing richer output.
958 If ⟨n⟩ is omitted, level 2 is assumed.
959 C pre-processor
961 -cpp Run the C pre-processor on Haskell source files
962 -D⟨symbol⟩[=⟨value⟩]
964 Define a symbol in the C pre-processor
965 -I⟨dir⟩
967 Add ⟨dir⟩ to the directory search list for #include files
968 -U⟨symbol⟩
970 Undefine a symbol in the C pre-processor
971 Finding imports
973 -i Empty the import directory list
974 -i⟨dir⟩[:⟨dir⟩]*
976 add ⟨dir⟩, ⟨dir2⟩, etc. to import path
977 Interactive mode
979 -fbreak-on-error
980 Break on uncaught exceptions and errors
981 -fbreak-on-exception
983 Break on any exception thrown
984 -fbreak-points
986 Insert breakpoints in the GHCi debugger
987 -fghci-hist-size=⟨n⟩
989 Set the number of entries GHCi keeps for :history. See The GHCi
990 Debugger.
991 -fghci-leak-check
993 (Debugging only) check for space leaks when loading new modules
994 in GHCi.
995 -fimplicit-import-qualified
997 Put in scope qualified identifiers for every loaded module
998 -flocal-ghci-history
1000 Use current directory for the GHCi command history file
1001 .ghci-history.
1002 -fno-it
1004 No longer set the special variable it.
1005 -fprint-bind-result
1007 Turn on printing of binding results in GHCi
1008 -fprint-evld-with-show
1010 Instruct :print to use Show instances where possible.
1011 -fshow-loaded-modules
1013 Show the names of modules that GHCi loaded after a :load com‐
1014 mand.
1015 -ghci-script
1017 Read additional .ghci files
1018 -ignore-dot-ghci
1020 Disable reading of .ghci files
1021 -interactive-print ⟨name⟩
1023 Select the function to use for printing evaluated expressions in
1024 GHCi
1025 Interface files
1027 --show-iface ⟨file⟩
1028 See Modes of operation.
1029 -ddump-hi
1031 Dump the new interface to stdout
1032 -ddump-hi-diffs
1034 Show the differences vs. the old interface
1035 -ddump-minimal-imports
1037 Dump a minimal set of imports
1038 Keeping intermediate files
1040 -keep-hc-file
1041 Retain intermediate .hc files.
1042 -keep-hi-files
1044 Retain intermediate .hi files (the default).
1045 -keep-hscpp-file
1047 Retain intermediate .hscpp files.
1048 -keep-llvm-file
1050 Retain intermediate LLVM .ll files. Implies -fllvm.
1051 -keep-o-files
1053 Retain intermediate .o files (the default).
1054 -keep-s-file
1056 Retain intermediate .s files.
1057 -keep-tmp-files
1059 Retain all intermediate temporary files.
1060 Language options
1062 -XAllowAmbiguousTypes
1063 Allow the user to write ambiguous types, and the type inference
1064 engine to infer them.
1065 -XApplicativeDo
1067 Enable Applicative do-notation desugaring
1068 -XArrows
1070 Enable arrow notation extension
1071 -XBangPatterns
1073 Enable bang patterns.
1074 -XBinaryLiterals
1076 Enable support for binary literals.
1077 -XBlockArguments
1079 Allow do blocks and other constructs as function arguments.
1080 -XCApiFFI
1082 Enable the CAPI calling convention.
1083 -XConstrainedClassMethods
1085 Enable constrained class methods.
1086 -XConstraintKinds
1088 Enable a kind of constraints.
1089 -XCPP Enable the C preprocessor.
1091 -XCUSKs
1093 Enable detection of complete user-supplied kind signatures.
1094 -XDataKinds
1096 Enable datatype promotion.
1097 -XDatatypeContexts
1099 Allow contexts on data types.
1100 -XDeepSubsumption
1102 Enable deep subsumption
1103 -XDefaultSignatures
1105 Enable default signatures.
1106 -XDeriveAnyClass
1108 Enable deriving for any class.
1109 -XDeriveDataTypeable
1111 Enable deriving for the Data class.
1112 -XDeriveFoldable
1114 Enable deriving for the Foldable class. Implied by
1115 DeriveTraversable.
1116 -XDeriveFunctor
1118 Enable deriving for the Functor class. Implied by
1119 DeriveTraversable.
1120 -XDeriveGeneric
1122 Enable deriving for the Generic class.
1123 -XDeriveLift
1125 Enable deriving for the Lift class
1126 -XDeriveTraversable
1128 Enable deriving for the Traversable class. Implies
1129 DeriveFunctor and DeriveFoldable.
1130 -XDerivingStrategies
1132 Enables deriving strategies.
1133 -XDerivingVia
1135 Enable deriving instances via types of the same runtime repre‐
1136 sentation. Implies DerivingStrategies.
1137 -XDisambiguateRecordFields
1139 Enable record field disambiguation. Implied by RecordWildCards.
1140 -XDuplicateRecordFields
1142 Allow definition of record types with identically-named fields.
1143 -XEmptyCase
1145 Allow empty case alternatives.
1146 -XEmptyDataDecls
1148 Allow definition of empty data types.
1149 -XEmptyDataDeriving
1151 Allow deriving instances of standard type classes for empty data
1152 types.
1153 -XExistentialQuantification
1155 Enable liberalised type synonyms.
1156 -XExplicitForAll
1158 Enable explicit universal quantification. Implied by
1159 ScopedTypeVariables, LiberalTypeSynonyms, RankNTypes and
1160 ExistentialQuantification.
1161 -XExplicitNamespaces
1163 Enable using the keyword type to specify the namespace of en‐
1164 tries in imports and exports (Explicit namespaces in import/ex‐
1165 port). Implied by TypeOperators and TypeFamilies.
1166 -XExtendedDefaultRules
1168 Use GHCi's extended default rules in a normal module.
1169 -XExtendedLiterals
1171 Enable numeric literal postfix syntax for unboxed integers.
1172 -XFieldSelectors
1174 Control visibility of field selector functions.
1175 -XFlexibleContexts
1177 Remove some restrictions on class contexts
1178 -XFlexibleInstances
1180 Enable flexible instances. Implies TypeSynonymInstances.
1181 -XForeignFunctionInterface
1183 Enable foreign function interface.
1184 -XFunctionalDependencies
1186 Enable functional dependencies. Implies MultiParamTypeClasses.
1187 -XGADTs
1189 Enable generalised algebraic data types. Implies GADTSyntax and
1190 MonoLocalBinds.
1191 -XGADTSyntax
1193 Enable generalised algebraic data type syntax.
1194 -XGeneralisedNewtypeDeriving
1196 Enable newtype deriving.
1197 -XGeneralizedNewtypeDeriving
1199 Enable newtype deriving.
1200 -XGHC2021
1202 Use GHC’s set of default language extensions from 2021
1203 -XGHCForeignImportPrim
1205 Enable prim calling convention. Intended for internal use only.
1206 -XHaskell2010
1208 Use the Haskell 2010 language variant.
1209 -XHaskell98
1211 Use the Haskell 98 language variant.
1212 -XHexFloatLiterals
1214 Enable support for hexadecimal floating point literals.
1215 -XImplicitParams
1217 Enable Implicit Parameters.
1218 -XImportQualifiedPost
1220 ImportQualifiedPost allows the syntax import M qualified
1221 -XImpredicativeTypes
1223 Enable impredicative types. Implies RankNTypes.
1224 -XIncoherentInstances
1226 Enable incoherent instances. Implies OverlappingInstances.
1227 -XInstanceSigs
1229 Enable instance signatures.
1230 -XInterruptibleFFI
1232 Enable interruptible FFI.
1233 -XKindSignatures
1235 Enable kind signatures. Implied by TypeFamilies and PolyKinds.
1236 -XLambdaCase
1238 Enable lambda-case expressions.
1239 -XLexicalNegation
1241 Use whitespace to determine whether the minus sign stands for
1242 negation or subtraction.
1243 -XLiberalTypeSynonyms
1245 Enable liberalised type synonyms.
1246 -XLinearTypes
1248 Enable linear types.
1249 -XMagicHash
1251 Allow # as a postfix modifier on identifiers.
1252 -XMonadComprehensions
1254 Enable monad comprehensions.
1255 -XMonoLocalBinds
1257 Enable do not generalise local bindings. Implied by
1258 TypeFamilies and GADTs.
1259 -XMultiParamTypeClasses
1261 Enable multi parameter type classes. Implied by
1262 FunctionalDependencies.
1263 -XMultiWayIf
1265 Enable multi-way if-expressions.
1266 -XNamedFieldPuns
1268 Enable record puns.
1269 -XNamedWildCards
1271 Enable named wildcards.
1272 -XNegativeLiterals
1274 Enable support for negative literals.
1275 -XNoImplicitPrelude
1277 Don't implicitly import Prelude. Implied by RebindableSyntax.
1278 -XNoMonomorphismRestriction
1280 Disable the monomorphism restriction.
1281 -XNondecreasingIndentation
1283 Allow nested contexts to be at the same indentation level as its
1284 enclosing context.
1285 -XNoPatternGuards
1287 Disable pattern guards. Implied by Haskell98.
1288 -XNoTraditionalRecordSyntax
1290 Disable support for traditional record syntax (as supported by
1291 Haskell 98) C {f = x}
1292 -XNPlusKPatterns
1294 Enable support for n+k patterns. Implied by Haskell98.
1295 -XNullaryTypeClasses
1297 Deprecated, does nothing. nullary (no parameter) type classes
1298 are now enabled using MultiParamTypeClasses.
1299 -XNumDecimals
1301 Enable support for 'fractional' integer literals.
1302 -XNumericUnderscores
1304 Enable support for numeric underscores.
1305 -XOverlappingInstances
1307 Enable overlapping instances.
1308 -XOverloadedLabels
1310 Enable overloaded labels.
1311 -XOverloadedLists
1313 Enable overloaded lists.
1314 -XOverloadedRecordDot
1316 Record '.' syntax
1317 -XOverloadedRecordUpdate
1319 Record '.' syntax record updates
1320 -XOverloadedStrings
1322 Enable overloaded string literals.
1323 -XPackageImports
1325 Enable package-qualified imports.
1326 -XParallelListComp
1328 Enable parallel list comprehensions.
1329 -XPartialTypeSignatures
1331 Enable partial type signatures.
1332 -XPatternSynonyms
1334 Enable pattern synonyms.
1335 -XPolyKinds
1337 Enable kind polymorphism. Implies KindSignatures.
1338 -XPostfixOperators
1340 Enable postfix operators.
1341 -XQualifiedDo
1343 Enable qualified do-notation desugaring.
1344 -XQuantifiedConstraints
1346 Allow forall quantifiers in constraints.
1347 -XQuasiQuotes
1349 Enable quasiquotation.
1350 -XRank2Types
1352 Enable rank-2 types. Synonym for RankNTypes.
1353 -XRankNTypes
1355 Enable rank-N types. Implied by ImpredicativeTypes.
1356 -XRebindableSyntax
1358 Employ rebindable syntax. Implies NoImplicitPrelude.
1359 -XRecordWildCards
1361 Enable record wildcards. Implies DisambiguateRecordFields.
1362 -XRecursiveDo
1364 Enable recursive do (mdo) notation.
1365 -XRoleAnnotations
1367 Enable role annotations.
1368 -XSafe Enable the Safe Haskell Safe mode.
1370 -XScopedTypeVariables
1372 Enable lexically-scoped type variables.
1373 -XStandaloneDeriving
1375 Enable standalone deriving.
1376 -XStandaloneKindSignatures
1378 Allow the use of standalone kind signatures.
1379 -XStarIsType
1381 Treat * as Data.Kind.Type.
1382 -XStaticPointers
1384 Enable static pointers.
1385 -XStrict
1387 Make bindings in the current module strict by default.
1388 -XStrictData
1390 Enable default strict datatype fields.
1391 -XTemplateHaskell
1393 Enable Template Haskell.
1394 -XTemplateHaskellQuotes
1396 Enable quotation subset of Template Haskell.
1397 -XTransformListComp
1399 Enable generalised list comprehensions.
1400 -XTrustworthy
1402 Enable the Safe Haskell Trustworthy mode.
1403 -XTupleSections
1405 Enable tuple sections.
1406 -XTypeAbstractions
1408 Enable type abstraction syntax in patterns and type variable
1409 binders.
1410 -XTypeApplications
1412 Enable type application syntax in terms and types.
1413 -XTypeData
1415 Enable type data declarations.
1416 -XTypeFamilies
1418 Enable type families. Implies ExplicitNamespaces,
1419 KindSignatures, and MonoLocalBinds.
1420 -XTypeFamilyDependencies
1422 Enable injective type families. Implies TypeFamilies.
1423 -XTypeInType
1425 Deprecated. Enable kind polymorphism and datatype promotion.
1426 -XTypeOperators
1428 Enable type operators. Implies ExplicitNamespaces.
1429 -XTypeSynonymInstances
1431 Enable type synonyms in instance heads. Implied by
1432 FlexibleInstances.
1433 -XUnboxedSums
1435 Enable unboxed sums.
1436 -XUnboxedTuples
1438 Enable the use of unboxed tuple syntax.
1439 -XUndecidableInstances
1441 Enable undecidable instances.
1442 -XUndecidableSuperClasses
1444 Allow all superclass constraints, including those that may re‐
1445 sult in non-termination of the typechecker.
1446 -XUnicodeSyntax
1448 Enable unicode syntax.
1449 -XUnliftedDatatypes
1451 Enable unlifted data types.
1452 -XUnliftedFFITypes
1454 Enable unlifted FFI types
1455 -XUnliftedNewtypes
1457 Enable unlifted newtypes.
1458 -XUnsafe
1460 Enable Safe Haskell Unsafe mode.
1461 -XViewPatterns
1463 Enable view patterns.
1464 Linking options
1466 -c Stop after generating object (.o) file
1467 -debug Use the debugging runtime
1469 -dylib-install-name ⟨path⟩
1471 Set the install name (via -install_name passed to Apple's
1472 linker), specifying the full install path of the library file.
1473 Any libraries or executables that link with it later will pick
1474 up that path as their runtime search location for it. (Dar‐
1475 win/OS X only)
1476 -dynamic
1478 Build dynamically-linked object files and executables
1479 -dynload
1481 Selects one of a number of modes for finding shared libraries at
1482 runtime.
1483 -eventlog
1485 Enable runtime event tracing
1486 -fcompact-unwind
1488 Instruct the linker to produce a __compact_unwind section.
1489 -fkeep-cafs
1491 Do not garbage-collect CAFs (top-level expressions) at runtime
1492 -flink-rts
1494 Link the runtime when generating a shared or static library
1495 -fno-embed-manifest
1497 Do not embed the manifest in the executable (Windows only)
1498 -fno-gen-manifest
1500 Do not generate a manifest file (Windows only)
1501 -fno-shared-implib
1503 Don't generate an import library for a DLL (Windows only)
1504 -framework ⟨name⟩
1506 On Darwin/OS X/iOS only, link in the framework ⟨name⟩. This op‐
1507 tion corresponds to the -framework option for Apple's Linker.
1508 -framework-path ⟨dir⟩
1510 On Darwin/OS X/iOS only, add ⟨dir⟩ to the list of directories
1511 searched for frameworks. This option corresponds to the -F op‐
1512 tion for Apple's Linker.
1513 -fsplit-sections
1515 Split sections for link-time dead-code stripping
1516 -fuse-rpaths
1518 Set the rpath based on -L flags
1519 -fwhole-archive-hs-libs
1521 When linking a binary executable, this inserts the flag
1522 -Wl,--whole-archive before any -l flags for Haskell libraries,
1523 and -Wl,--no-whole-archive afterwards
1524 -L ⟨dir⟩
1526 Add ⟨dir⟩ to the list of directories searched for libraries
1527 -l ⟨lib⟩
1529 Link in library ⟨lib⟩
1530 -main-is ⟨thing⟩
1532 Set main module and function
1533 -no-hs-main
1535 Don't assume this program contains main
1536 -no-pie
1538 Don't instruct the linker to produce a position-independent exe‐
1539 cutable.
1540 -no-rtsopts-suggestions
1542 Don't print RTS suggestions about linking with
1543 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩].
1544 -package ⟨name⟩
1546 Expose package ⟨pkg⟩
1547 -pie Instruct the linker to produce a position-independent exe‐
1549 cutable.
1550 -rdynamic
1552 This instructs the linker to add all symbols, not only used
1553 ones, to the dynamic symbol table. Currently Linux and Win‐
1554 dows/MinGW32 only. This is equivalent to using -optl -rdynamic
1555 on Linux, and -optl -export-all-symbols on Windows.
1556 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩]
1558 Control whether the RTS behaviour can be tweaked via com‐
1559 mand-line flags and the GHCRTS environment variable. Using none
1560 means no RTS flags can be given; some means only a minimum of
1561 safe options can be given (the default); all (or no argument at
1562 all) means that all RTS flags are permitted; ignore means RTS
1563 flags can be given, but are treated as regular arguments and
1564 passed to the Haskell program as arguments; ignoreAll is the
1565 same as ignore, but GHCRTS is also ignored. -rtsopts does not
1566 affect -with-rtsopts behavior; flags passed via -with-rtsopts
1567 are used regardless of -rtsopts.
1568 -shared
1570 Generate a shared library (as opposed to an executable)
1571 -single-threaded
1573 Use the single-threaded runtime
1574 -static
1576 Use static Haskell libraries
1577 -staticlib
1579 Generate a standalone static library (as opposed to an exe‐
1580 cutable). This is useful when cross compiling. The library to‐
1581 gether with all its dependencies ends up in in a single static
1582 library that can be linked against.
1583 -threaded
1585 Use the threaded runtime
1586 -with-rtsopts=⟨opts⟩
1588 Set the default RTS options to ⟨opts⟩.
1589 Miscellaneous options
1591 -ddump-mod-cycles
1592 Dump module cycles
1593 -fdefer-out-of-scope-variables
1595 Convert variable out of scope variables errors into warnings.
1596 Implied by -fdefer-type-errors. See also
1597 -Wdeferred-out-of-scope-variables.
1598 -fdefer-type-errors
1600 Turn type errors into warnings, deferring the error until run‐
1601 time. Implies -fdefer-typed-holes and
1602 -fdefer-out-of-scope-variables. See also
1603 -Wdeferred-type-errors.
1604 -fdefer-typed-holes
1606 Convert typed hole errors into warnings, deferring the error un‐
1607 til runtime. Implied by -fdefer-type-errors. See also
1608 -Wtyped-holes.
1609 -fexternal-interpreter
1611 Run interpreted code in a separate process
1612 -ffamily-application-cache
1614 Use a cache when reducing type family applications
1615 -fglasgow-exts
1617 Deprecated. Enable most language extensions; see Controlling ex‐
1618 tensions for exactly which ones.
1619 -fno-safe-haskell
1621 Disable Safe Haskell
1622 -ghcversion-file ⟨path to ghcversion.h⟩
1624 (GHC as a C compiler only) Use this ghcversion.h file
1625 -H ⟨size⟩
1627 Set the minimum size of the heap to ⟨size⟩
1628 -hidden-module ⟨module name⟩
1630 A module which should not be visible outside its unit.
1631 -j[⟨n⟩]
1633 When compiling with --make, compile ⟨n⟩ modules in parallel.
1634 -jsem When compiling with --make, coordinate with other processes
1636 through the semaphore ⟨sem⟩ to compile modules in parallel.
1637 -reexported-module ⟨module name⟩
1639 A module which should be reexported from this unit.
1640 -this-package-name ⟨unit-id⟩
1642 The name of the package which this module would be part of when
1643 installed.
1644 -unit @⟨filename⟩
1646 Specify the options to build a specific unit.
1647 -working-dir ⟨dir⟩
1649 Specify the directory a unit is expected to be compiled in.
1650 Modes of operation
1652 --frontend ⟨module⟩
1653 run GHC with the given frontend plugin; see Frontend plugins for
1654 details.
1655 --help Display help
1657 --info display information about the compiler
1659 --interactive
1661 Interactive mode - normally used by just running ghci; see Using
1662 GHCi for details.
1663 --make Build a multi-module Haskell program, automatically figuring out
1665 dependencies. Likely to be much easier, and faster, than using
1666 make; see Using ghc --make for details.
1667 --numeric-version
1669 display GHC version (numeric only)
1670 --print-booter-version
1672 display bootstrap compiler version
1673 --print-build-platform
1675 display platform on which GHC was built
1676 --print-c-compiler-flags
1678 C compiler flags used to build GHC
1679 --print-c-compiler-link-flags
1681 C linker flags used to build GHC
1682 --print-debug-on
1684 print whether GHC was built with -DDEBUG
1685 --print-global-package-db
1687 display GHC's global package database directory
1688 --print-have-interpreter
1690 display whether GHC was built with interactive support
1691 --print-have-native-code-generator
1693 display whether target platform has NCG support
1694 --print-host-platform
1696 display host platform of GHC
1697 --print-ld-flags
1699 display linker flags used to compile GHC
1700 --print-leading-underscore
1702 display use of leading underscores on symbol names
1703 --print-libdir
1705 display GHC library directory
1706 --print-object-splitting-supported
1708 display whether GHC supports object splitting
1709 --print-project-git-commit-id
1711 display Git commit id GHC is built from
1712 --print-project-version
1714 display GHC version
1715 --print-rts-ways
1717 display which way RTS was built
1718 --print-stage
1720 display stage number of GHC
1721 --print-support-smp
1723 display whether GHC was compiled with SMP support
1724 --print-tables-next-to-code
1726 display whether GHC was compiled with --enable-ta‐
1727 bles-next-to-code
1728 --print-target-platform
1730 display target platform of GHC
1731 --print-unregisterised
1733 display whether this GHC was built in unregisterised mode
1734 --run ⟨file⟩
1736 Run a Haskell program.
1737 --show-iface ⟨file⟩
1739 display the contents of an interface file.
1740 --show-options
1742 display the supported command line options
1743 --supported-extensions
1745 display the supported language extensions
1746 --version
1748 display GHC version
1749 -e ⟨expr⟩
1751 Evaluate expr; see Expression evaluation mode for details.
1752 -M generate dependency information suitable for use in a Makefile;
1754 see Dependency generation for details.
1755 -shared
1757 Create a shared object.
1758 Individual optimizations
1760 -fasm-shortcutting
1761 Enable shortcutting on assembly. Implied by -O2.
1762 -fbinary-blob-threshold=⟨n⟩
1764 default: 500K. Tweak assembly generator for binary blobs.
1765 -fblock-layout-cfg
1767 Use the new cfg based block layout algorithm. Implied by -O.
1768 -fblock-layout-weightless
1770 Ignore cfg weights for code layout.
1771 -fblock-layout-weights
1773 Sets edge weights used by the new code layout algorithm.
1774 -fcall-arity
1776 Enable call-arity optimisation. Implied by -O.
1777 -fcase-folding
1779 Enable constant folding in case expressions. Implied by -O.
1780 -fcase-merge
1782 Enable case-merging. Implied by -O.
1783 -fcmm-control-flow
1785 Enable control flow optimisation in the Cmm backend. Implied by
1786 -O.
1787 -fcmm-elim-common-blocks
1789 Enable Cmm common block elimination. Implied by -O.
1790 -fcmm-sink
1792 Enable Cmm sinking. Implied by -O.
1793 -fcmm-static-pred
1795 Enable static control flow prediction. Implied by -O.
1796 -fcore-constant-folding
1798 Enable constant folding in Core. Implied by -O.
1799 -fcpr-anal
1801 Turn on Constructed Product Result analysis. Implied by -O.
1802 -fcross-module-specialise
1804 Turn on specialisation of overloaded functions imported from
1805 other modules. Implied by -O.
1806 -fcse Enable common sub-expression elimination. Implied by -O.
1808 -fdicts-cheap
1810 Make dictionary-valued expressions seem cheap to the optimiser.
1811 -fdicts-strict
1813 Make dictionaries strict. Implied by -O2.
1814 -fdmd-tx-dict-sel
1816 (deprecated) Use a special demand transformer for dictionary se‐
1817 lectors.
1818 -fdmd-unbox-width=⟨n⟩
1820 default: 3. Boxity analysis pretends that returned records with
1821 this many fields can be unboxed.
1822 -fdo-eta-reduction
1824 Enable eta-reduction. Always enabled by default.
1825 -fdo-lambda-eta-expansion
1827 Enable lambda eta-expansion. Always enabled by default.
1828 -feager-blackholing
1830 Turn on eager blackholing
1831 -fenable-rewrite-rules
1833 Switch on all rewrite rules (including rules generated by auto‐
1834 matic specialisation of overloaded functions). Implied by -O.
1835 -fexcess-precision
1837 Enable excess intermediate precision
1838 -fexitification
1840 Enables exitification optimisation. Implied by -O.
1841 -fexpose-all-unfoldings
1843 Expose all unfoldings, even for very large or recursive func‐
1844 tions.
1845 -ffloat-in
1847 Turn on the float-in transformation. Implied by -O.
1848 -ffull-laziness
1850 Turn on full laziness (floating bindings outwards). Implied by
1851 -O.
1852 -ffun-to-thunk
1854 (deprecated) superseded by -ffull-laziness.
1855 -fignore-asserts
1857 Ignore assertions in the source. Implied by -O.
1858 -fignore-interface-pragmas
1860 Ignore pragmas in interface files. Implied by -O0 only.
1861 -finline-generics
1863 Annotate methods of derived Generic and Generic1 instances with
1864 INLINE[1] pragmas based on heuristics. Implied by -O.
1865 -finline-generics-aggressively
1867 Annotate methods of all derived Generic and Generic1 instances
1868 with INLINE[1] pragmas.
1869 -flate-dmd-anal
1871 Run demand analysis again, at the end of the simplification
1872 pipeline
1873 -flate-specialise
1875 Run a late specialisation pass
1876 -fliberate-case
1878 Turn on the liberate-case transformation. Implied by -O2.
1879 -fliberate-case-threshold=⟨n⟩
1881 default: 2000. Set the size threshold for the liberate-case
1882 transformation to ⟨n⟩
1883 -fllvm-pass-vectors-in-regs
1885 (deprecated) Does nothing
1886 -flocal-float-out
1888 Enable local floating definitions out of let-binds.
1889 -flocal-float-out-top-level
1891 Enable local floating to float top-level bindings
1892 -floopification
1894 Turn saturated self-recursive tail-calls into local jumps in the
1895 generated assembly. Implied by -O.
1896 -fmax-inline-alloc-size=⟨n⟩
1898 default: 128. Set the maximum size of inline array allocations
1899 to ⟨n⟩ bytes (default: 128).
1900 -fmax-inline-memcpy-insns=⟨n⟩
1902 default: 32. Inline memcpy calls if they would generate no more
1903 than ⟨n⟩ pseudo instructions.
1904 -fmax-inline-memset-insns=⟨n⟩
1906 default: 32. Inline memset calls if they would generate no more
1907 than ⟨n⟩ pseudo instructions
1908 -fmax-simplifier-iterations=⟨n⟩
1910 default: 4. Set the max iterations for the simplifier.
1911 -fmax-uncovered-patterns=⟨n⟩
1913 default: 4. Set the maximum number of patterns to display in
1914 warnings about non-exhaustive ones.
1915 -fmax-worker-args=⟨n⟩
1917 default: 10. Maximum number of value arguments for a worker.
1918 -fno-opt-coercion
1920 Turn off the coercion optimiser
1921 -fno-pre-inlining
1923 Turn off pre-inlining
1924 -fno-state-hack
1926 Turn off the state hackwhereby any lambda with a real-world
1927 state token as argument is considered to be single-entry. Hence
1928 OK to inline things inside it.
1929 -fomit-interface-pragmas
1931 Don't generate interface pragmas. Implied by -O0 only.
1932 -fomit-yields
1934 Omit heap checks when no allocation is being performed.
1935 -foptimal-applicative-do
1937 Use a slower but better algorithm for ApplicativeDo
1938 -fpedantic-bottoms
1940 Make GHC be more precise about its treatment of bottom (but see
1941 also -fno-state-hack). In particular, GHC will not eta-expand
1942 through a case expression.
1943 -fpolymorphic-specialisation
1945 Allow specialisation to abstract over free type variables
1946 -fregs-graph
1948 Use the graph colouring register allocator for register alloca‐
1949 tion in the native code generator.
1950 -fregs-iterative
1952 Use the iterative coalescing graph colouring register allocator
1953 in the native code generator.
1954 -fsimpl-tick-factor=⟨n⟩
1956 default: 100. Set the percentage factor for simplifier ticks.
1957 -fsimplifier-phases=⟨n⟩
1959 default: 2. Set the number of phases for the simplifier. Ig‐
1960 nored with -O0.
1961 -fsolve-constant-dicts
1963 When solving constraints, try to eagerly solve super classes us‐
1964 ing available dictionaries. Implied by -O.
1965 -fspec-constr
1967 Turn on the SpecConstr transformation. Implied by -O2.
1968 -fspec-constr-count=⟨n⟩
1970 default: 3.* Set to ⟨n⟩ the maximum number of specialisations
1971 that will be created for any one function by the SpecConstr
1972 transformation.
1973 -fspec-constr-keen
1975 Specialize a call with an explicit constructor argument, even if
1976 the argument is not scrutinised in the body of the function
1977 -fspec-constr-threshold=⟨n⟩
1979 default: 2000. Set the size threshold for the SpecConstr trans‐
1980 formation to ⟨n⟩.
1981 -fspecialise
1983 Turn on specialisation of overloaded functions. Implied by -O.
1984 -fspecialise-aggressively
1986 Turn on specialisation of overloaded functions regardless of
1987 size, if unfolding is available
1988 -fspecialise-incoherents
1990 Enable specialisation on incoherent instances
1991 -fstatic-argument-transformation
1993 Turn on the static argument transformation.
1994 -fstg-cse
1996 Enable common sub-expression elimination on the STG intermediate
1997 language. Implied by -O.
1998 -fstg-lift-lams
2000 Enable late lambda lifting on the STG intermediate language. Im‐
2001 plied by -O2.
2002 -fstg-lift-lams-known
2004 Allow turning known into unknown calls while performing late
2005 lambda lifting.
2006 -fstg-lift-lams-non-rec-args
2008 Create top-level non-recursive functions with at most <n> param‐
2009 eters while performing late lambda lifting.
2010 -fstg-lift-lams-rec-args
2012 Create top-level recursive functions with at most <n> parameters
2013 while performing late lambda lifting.
2014 -fstrictness
2016 Turn on demand analysis. Implied by -O. Implies
2017 -fworker-wrapper
2018 -fstrictness-before=⟨n⟩
2020 Run an additional demand analysis before simplifier phase ⟨n⟩
2021 -funbox-small-strict-fields
2023 Flatten strict constructor fields with a pointer-sized represen‐
2024 tation. Implied by -O.
2025 -funbox-strict-fields
2027 Flatten strict constructor fields
2028 -funfolding-case-scaling=⟨n⟩
2030 default: 30. Apply a penalty of (inlining_cost * 1/n) for each
2031 level of case nesting.
2032 -funfolding-case-threshold=⟨n⟩
2034 default: 2. Reduce inlining for cases nested deeper than n.
2035 -funfolding-creation-threshold=⟨n⟩
2037 default: 750. Tweak unfolding settings.
2038 -funfolding-dict-discount=⟨n⟩
2040 default: 30. Tweak unfolding settings.
2041 -funfolding-fun-discount=⟨n⟩
2043 default: 60. Tweak unfolding settings.
2044 -funfolding-keeness-factor=⟨n⟩
2046 This has been deprecated in GHC 9.0.1.
2047 -funfolding-use-threshold=⟨n⟩
2049 default: 80. Tweak unfolding settings.
2050 -fworker-wrapper
2052 Enable the worker/wrapper transformation. Implied by -O and by
2053 -fstrictness.
2054 -fworker-wrapper-cbv
2056 Enable w/w splits for wrappers whos sole purpose is evaluating
2057 arguments.
2058 Optimization levels
2060 -O Enable level 1 optimisations
2061 -O0 Disable optimisations (default)
2063 -O2 Enable level 2 optimisations
2065 -O⟨n⟩ Any -On where n > 2 is the same as -O2.
2067 Package options
2069 -clear-package-db
2070 Clear the package db stack.
2071 -distrust ⟨pkg⟩
2073 Expose package ⟨pkg⟩ and set it to be distrusted. See Safe
2074 Haskell.
2075 -distrust-all-packages
2077 Distrust all packages by default. See Safe Haskell.
2078 -fpackage-trust
2080 Enable Safe Haskell trusted package requirement for trustworthy
2081 modules.
2082 -global-package-db
2084 Add the global package db to the stack.
2085 -hide-all-packages
2087 Hide all packages by default
2088 -hide-package ⟨pkg⟩
2090 Hide package ⟨pkg⟩
2091 -ignore-package ⟨pkg⟩
2093 Ignore package ⟨pkg⟩
2094 -no-auto-link-packages
2096 Don't automatically link in the base and rts packages.
2097 -no-global-package-db
2099 Remove the global package db from the stack.
2100 -no-user-package-db
2102 Remove the user's package db from the stack.
2103 -package ⟨pkg⟩
2105 Expose package ⟨pkg⟩
2106 -package-db ⟨file⟩
2108 Add ⟨file⟩ to the package db stack.
2109 -package-env ⟨file⟩|⟨name⟩
2111 Use the specified package environment.
2112 -package-id ⟨unit-id⟩
2114 Expose package by id ⟨unit-id⟩
2115 -this-unit-id ⟨unit-id⟩
2117 Compile to be part of unit (i.e. package) ⟨unit-id⟩
2118 -trust ⟨pkg⟩
2120 Expose package ⟨pkg⟩ and set it to be trusted. See Safe Haskell.
2121 -user-package-db
2123 Add the user's package db to the stack.
2124 Phases of compilation
2126 --merge-objs
2127 Merge a set of objects into a GHCi library.
2128 -C Stop after generating C (.hc file)
2130 -c Stop after generating object (.o) file
2132 -E Stop after preprocessing (.hspp file)
2134 -F Enable the use of a pre-processor (set with -pgmF ⟨cmd⟩)
2136 -S Stop after generating assembly (.s file)
2138 -x ⟨suffix⟩
2140 Override default behaviour for source files
2141 Overriding external programs
2143 -pgma ⟨cmd⟩
2144 Use ⟨cmd⟩ as the assembler
2145 -pgmc ⟨cmd⟩
2147 Use ⟨cmd⟩ as the C compiler
2148 -pgmcxx ⟨cmd⟩
2150 Use ⟨cmd⟩ as the C++ compiler
2151 -pgmdll ⟨cmd⟩
2153 Use ⟨cmd⟩ as the DLL generator
2154 -pgmF ⟨cmd⟩
2156 Use ⟨cmd⟩ as the pre-processor (with -F only)
2157 -pgmi ⟨cmd⟩
2159 Use ⟨cmd⟩ as the external interpreter command.
2160 -pgminstall_name_tool ⟨cmd⟩
2162 Use ⟨cmd⟩ as the program to inject runpath into mach-o dylibs on
2163 macOS
2164 -pgmL ⟨cmd⟩
2166 Use ⟨cmd⟩ as the literate pre-processor
2167 -pgml ⟨cmd⟩
2169 Use ⟨cmd⟩ as the linker
2170 -pgmlc ⟨cmd⟩
2172 Use ⟨cmd⟩ as the LLVM compiler
2173 -pgmlm ⟨cmd⟩
2175 Use ⟨cmd⟩ as the linker when merging object files
2176 -pgmlo ⟨cmd⟩
2178 Use ⟨cmd⟩ as the LLVM optimiser
2179 -pgmotool ⟨cmd⟩
2181 Use ⟨cmd⟩ as the program to inspect mach-o dylibs on macOS
2182 -pgmP ⟨cmd⟩
2184 Use ⟨cmd⟩ as the C pre-processor (with -cpp only)
2185 -pgms ⟨cmd⟩
2187 Use ⟨cmd⟩ as the splitter
2188 -pgmwindres ⟨cmd⟩
2190 Use ⟨cmd⟩ as the program for embedding manifests on Windows.
2191 Phase-specific options
2193 -opta ⟨option⟩
2194 pass ⟨option⟩ to the assembler
2195 -optc ⟨option⟩
2197 pass ⟨option⟩ to the C compiler
2198 -optcxx ⟨option⟩
2200 pass ⟨option⟩ to the C++ compiler
2201 -optF ⟨option⟩
2203 pass ⟨option⟩ to the custom pre-processor
2204 -opti ⟨option⟩
2206 pass ⟨option⟩ to the interpreter sub-process.
2207 -optL ⟨option⟩
2209 pass ⟨option⟩ to the literate pre-processor
2210 -optl ⟨option⟩
2212 pass ⟨option⟩ to the linker
2213 -optlc ⟨option⟩
2215 pass ⟨option⟩ to the LLVM compiler
2216 -optlm ⟨option⟩
2218 pass ⟨option⟩ to the linker when merging object files.
2219 -optlo ⟨option⟩
2221 pass ⟨option⟩ to the LLVM optimiser
2222 -optP ⟨option⟩
2224 pass ⟨option⟩ to cpp (with -cpp only)
2225 -optwindres ⟨option⟩
2227 pass ⟨option⟩ to windres.
2228 -pgmc-supports-no-pie
2230 (deprecated) Indicate that the linker supports -no-pie
2231 -pgml-supports-no-pie
2233 Indicate that the linker supports -no-pie
2234 Platform-specific options
2236 -mavx (x86 only) Enable support for AVX SIMD extensions
2237 -mavx2 (x86 only) Enable support for AVX2 SIMD extensions
2239 -mavx512cd
2241 (x86 only) Enable support for AVX512-CD SIMD extensions
2242 -mavx512er
2244 (x86 only) Enable support for AVX512-ER SIMD extensions
2245 -mavx512f
2247 (x86 only) Enable support for AVX512-F SIMD extensions
2248 -mavx512pf
2250 (x86 only) Enable support for AVX512-PF SIMD extensions
2251 -mbmi (x86 only) Use BMI1 for bit manipulation operations
2253 -mbmi2 (x86 only) Use BMI2 for bit manipulation operations
2255 -mfma Use native FMA instructions for fused multiply-add float‐
2257 ing-point operations
2258 -msse (x86 only) Use SSE for floating-point operations
2260 -msse2 (x86 only) Use SSE2 for floating-point operations
2262 -msse3 (x86 only) Use SSE3 for floating-point operations
2264 -msse4 (x86 only) Use SSE4 for floating-point operations
2266 -msse4.2
2268 (x86 only) Use SSE4.2 for floating-point operations
2269 Compiler plugins
2271 -fclear-plugins
2272 Clear the list of active plugins
2273 -fplugin-library=⟨file-path⟩;⟨unit-id⟩;⟨module⟩;⟨args⟩
2275 Load a pre-compiled static plugin from an external library
2276 -fplugin-opt=⟨module⟩:⟨args⟩
2278 Give arguments to a plugin module; module must be specified with
2279 -fplugin=⟨module⟩
2280 -fplugin-trustworthy
2282 Trust the used plugins and no longer mark the compiled module as
2283 unsafe
2284 -fplugin=⟨module⟩
2286 Load a plugin exported by a given module
2287 -hide-all-plugin-packages
2289 Hide all packages for plugins by default
2290 -plugin-package ⟨pkg⟩
2292 Expose ⟨pkg⟩ for plugins
2293 -plugin-package-id ⟨pkg-id⟩
2295 Expose ⟨pkg-id⟩ for plugins
2296 Profiling
2298 -auto (deprecated) Alias for -fprof-auto-exported
2299 -auto-all
2301 (deprecated) Alias for -fprof-auto
2302 -caf-all
2304 (deprecated) Alias for -fprof-cafs
2305 -fno-prof-count-entries
2307 Do not collect entry counts
2308 -fprof-auto
2310 Auto-add SCC\ s to all bindings not marked INLINE
2311 -fprof-auto-calls
2313 Auto-add SCC\ s to all call sites
2314 -fprof-auto-exported
2316 Auto-add SCC\ s to all exported bindings not marked INLINE
2317 -fprof-auto-top
2319 Auto-add SCC\ s to all top-level bindings not marked INLINE
2320 -fprof-cafs
2322 Auto-add SCC\ s to all CAFs
2323 -fprof-callers=⟨name⟩
2325 Auto-add SCC\ s to all call-sites of the named function.
2326 -fprof-late
2328 Auto-add SCC\ s to all top level bindings after the core pipe‐
2329 line has run.
2330 -fprof-late-inline
2332 Auto-add SCC\ s to all top level bindings after the optimizer
2333 has run and retain them when inlining.
2334 -fprof-manual
2336 Process manual SCC annotations.
2337 -no-auto
2339 (deprecated) Alias for -fno-prof-auto
2340 -no-auto-all
2342 (deprecated) Alias for -fno-prof-auto
2343 -no-caf-all
2345 (deprecated) Alias for -fno-prof-cafs
2346 -prof Turn on profiling
2348 -ticky Turn on ticky-ticky profiling
2350 -ticky-allocd
2352 Track the number of times each closure type is allocated.
2353 -ticky-ap-thunk
2355 Don't use standard AP thunks on order to get more reliable entry
2356 counters.
2357 -ticky-dyn-thunk
2359 Track allocations of dynamic thunks
2360 -ticky-LNE
2362 Treat join point binders similar to thunks/functions.
2363 -ticky-tag-checks
2365 Emit dummy ticky counters to record how many tag-inference
2366 checks tag inference avoided.
2367 Program coverage
2369 -fhpc Turn on Haskell program coverage instrumentation
2370 -hpcdir⟨dir⟩
2372 Set the directory where GHC places .mix files.
2373 Recompilation checking
2375 -exclude-module=⟨file⟩
2376 Regard ⟨file⟩ as "stable"; i.e., exclude it from having depen‐
2377 dencies on it.
2378 -fforce-recomp
2380 Turn off recompilation checking. This is implied by any -ddump-X
2381 option when compiling a single file (i.e. when using -c).
2382 -fignore-hpc-changes
2384 Do not recompile modules just to match changes to HPC flags.
2385 This is especially useful for avoiding recompilation when using
2386 GHCi, and is enabled by default for GHCi.
2387 -fignore-optim-changes
2389 Do not recompile modules just to match changes to optimisation
2390 flags. This is especially useful for avoiding recompilation when
2391 using GHCi, and is enabled by default for GHCi.
2392 -include-cpp-deps
2394 Include preprocessor dependencies
2395 -include-pkg-deps
2397 Regard modules imported from packages as unstable
2398 Redirecting output
2400 -dep-makefile ⟨file⟩
2401 Use ⟨file⟩ as the makefile
2402 -dep-suffix ⟨suffix⟩
2404 Make dependencies that declare that files with suffix
2405 .⟨suf⟩⟨osuf⟩ depend on interface files with suffix .⟨suf⟩hi
2406 -dumpdir ⟨dir⟩
2408 redirect dump files
2409 -dynhisuf ⟨suffix⟩
2411 set the suffix to use for dynamic interface files
2412 -dyno ⟨file⟩
2414 set dynamic output filename
2415 -dynohi ⟨file⟩
2417 set the filename in which to put the dynamic interface
2418 -dynosuf ⟨suffix⟩
2420 set the dynamic output file suffix
2421 -hcsuf ⟨suffix⟩
2423 set the suffix to use for intermediate C files
2424 -hidir ⟨dir⟩
2426 set directory for interface files
2427 -hiedir ⟨dir⟩
2429 set directory for extended interface files
2430 -hiesuf ⟨suffix⟩
2432 set the suffix to use for extended interface files
2433 -hisuf ⟨suffix⟩
2435 set the suffix to use for interface files
2436 -o ⟨file⟩
2438 set output filename
2439 -odir ⟨dir⟩
2441 set directory for object files
2442 -ohi ⟨file⟩
2444 set the filename in which to put the interface
2445 -osuf ⟨suffix⟩
2447 set the output file suffix
2448 -outputdir ⟨dir⟩
2450 set output directory
2451 -stubdir ⟨dir⟩
2453 redirect FFI stub files
2454 Temporary files
2456 -tmpdir ⟨dir⟩
2457 set the directory for temporary files
2458 Verbosity options
2460 -fabstract-refinement-hole-fits
2461 default: off. Toggles whether refinements where one or more of
2462 the holes are abstract are reported.
2463 -fdefer-diagnostics
2465 Defer and group diagnostic messages by severity
2466 -fdiagnostics-color=⟨always|auto|never⟩
2468 Use colors in error messages
2469 -fdiagnostics-show-caret
2471 Whether to show snippets of original source code
2472 -ferror-spans
2474 Output full span in error messages
2475 -fhide-source-paths
2477 hide module source and object paths
2478 -fkeep-going
2480 Continue compilation as far as possible on errors
2481 -fmax-refinement-hole-fits=⟨n⟩
2483 default: 6. Set the maximum number of refinement hole fits for
2484 typed holes to display in type error messages.
2485 -fmax-relevant-binds=⟨n⟩
2487 default: 6. Set the maximum number of bindings to display in
2488 type error messages.
2489 -fmax-valid-hole-fits=⟨n⟩
2491 default: 6. Set the maximum number of valid hole fits for typed
2492 holes to display in type error messages.
2493 -fno-show-valid-hole-fits
2495 Disables showing a list of valid hole fits for typed holes in
2496 type error messages.
2497 -fno-sort-valid-hole-fits
2499 Disables the sorting of the list of valid hole fits for typed
2500 holes in type error messages.
2501 -fprint-axiom-incomps
2503 Display equation incompatibilities in closed type families
2504 -fprint-equality-relations
2506 Distinguish between equality relations when printing
2507 -fprint-expanded-synonyms
2509 In type errors, also print type-synonym-expanded types.
2510 -fprint-explicit-coercions
2512 Print coercions in types
2513 -fprint-explicit-foralls
2515 Print explicit forall quantification in types. See also
2516 ExplicitForAll
2517 -fprint-explicit-kinds
2519 Print explicit kind foralls and kind arguments in types. See
2520 also KindSignatures
2521 -fprint-explicit-runtime-reps
2523 Print RuntimeRep and Levity variables in types which are run‐
2524 time-representation polymorphic.
2525 -fprint-potential-instances
2527 display all available instances in type error messages
2528 -fprint-redundant-promotion-ticks
2530 Print redundant DataKinds promotion ticks
2531 -fprint-typechecker-elaboration
2533 Print extra information from typechecker.
2534 -fprint-unicode-syntax
2536 Use unicode syntax when printing expressions, types and kinds.
2537 See also UnicodeSyntax
2538 -frefinement-level-hole-fits=⟨n⟩
2540 default: off. Sets the level of refinement of the refinement
2541 hole fits, where level n means that hole fits of up to n holes
2542 will be considered.
2543 -freverse-errors
2545 Output errors in reverse order
2546 -fshow-docs-of-hole-fits
2548 Toggles whether to show the documentation of the valid hole fits
2549 in the output.
2550 -fshow-error-context
2552 Whether to show textual information about error context
2553 -fshow-hole-constraints
2555 Show constraints when reporting typed holes.
2556 -fshow-hole-matches-of-hole-fits
2558 Toggles whether to show the type of the additional holes in re‐
2559 finement hole fits.
2560 -fshow-provenance-of-hole-fits
2562 Toggles whether to show the provenance of the valid hole fits in
2563 the output.
2564 -fshow-type-app-of-hole-fits
2566 Toggles whether to show the type application of the valid hole
2567 fits in the output.
2568 -fshow-type-app-vars-of-hole-fits
2570 Toggles whether to show what type each quantified variable takes
2571 in a valid hole fit.
2572 -fshow-type-of-hole-fits
2574 Toggles whether to show the type of the valid hole fits in the
2575 output.
2576 -fsort-by-size-hole-fits
2578 Sort valid hole fits by size.
2579 -fsort-by-subsumption-hole-fits
2581 Sort valid hole fits by subsumption.
2582 -funclutter-valid-hole-fits
2584 Unclutter the list of valid hole fits by not showing provenance
2585 nor type applications of suggestions.
2586 -Rghc-timing
2588 Summarise timing stats for GHC (same as +RTS -tstderr).
2589 -v verbose mode (equivalent to -v3)
2591 -v⟨n⟩ set verbosity level
2593 Warnings
2595 -fenable-th-splice-warnings
2596 Generate warnings for Template Haskell splices
2597 -fhelpful-errors
2599 Make suggestions for mis-spelled names.
2600 -fmax-pmcheck-models=⟨n⟩
2602 soft limit on the number of parallel models the pattern match
2603 checker should check a pattern match clause against
2604 -fshow-warning-groups
2606 show which group an emitted warning belongs to.
2607 -fvia-C
2609 use the C code generator
2610 -W enable normal warnings
2612 -w disable all warnings
2614 -Wall enable almost all warnings (details in Warnings and san‐
2616 ity-checking)
2617 -Wall-missed-specialisations
2619 warn when specialisation of any overloaded function fails.
2620 -Wall-missed-specializations
2622 alias for -Wall-missed-specialisations
2623 -Wambiguous-fields
2625 warn about ambiguous field selectors or updates
2626 -Wauto-orphans
2628 (deprecated) Does nothing
2629 -Wcompat
2631 enable future compatibility warnings (details in Warnings and
2632 sanity-checking)
2633 -Wcompat-unqualified-imports
2635 Report unqualified imports of core libraries which are expected
2636 to cause compatibility problems in future releases.
2637 -Wcpp-undef
2639 warn on uses of the #if directive on undefined identifiers
2640 -Wdefault
2642 enable default flags
2643 -Wdeferred-out-of-scope-variables
2645 Report warnings when variable out-of-scope errors are deferred
2646 until runtime. See -fdefer-out-of-scope-variables.
2647 -Wdeferred-type-errors
2649 Report warnings when deferred type errors are enabled. This op‐
2650 tion is enabled by default. See -fdefer-type-errors.
2651 -Wdeprecated-flags
2653 warn about uses of commandline flags that are deprecated
2654 -Wdeprecations
2656 warn about uses of functions & types that have DEPRECATED prag‐
2657 mas, or WARNING pragmas with the deprecated category.
2658 -Wderiving-defaults
2660 warn about default deriving when using both DeriveAnyClass and
2661 GeneralizedNewtypeDeriving
2662 -Wderiving-typeable
2664 warn when Typeable is derived
2665 -Wdodgy-exports
2667 warn about dodgy exports
2668 -Wdodgy-foreign-imports
2670 warn about dodgy foreign imports
2671 -Wdodgy-imports
2673 warn about dodgy imports
2674 -Wduplicate-constraints
2676 warn when a constraint appears duplicated in a type signature
2677 -Wduplicate-exports
2679 warn when an entity is exported multiple times
2680 -Wempty-enumerations
2682 warn about enumerations that are empty
2683 -Werror
2685 make warnings fatal
2686 -Weverything
2688 enable all warnings supported by GHC
2689 -Wextended-warnings
2691 warn about uses of functions & types that have WARNING or DEPRE‐
2692 CATED pragmas, across all categories
2693 -Wextra
2695 alias for -W
2696 -Wforall-identifier
2698 warn when forall is used as an identifier (at definition sites)
2699 -Wgadt-mono-local-binds
2701 warn when pattern matching on a GADT without MonoLocalBinds
2702 -Whi-shadowing
2704 (deprecated) warn when a .hi file in the current directory shad‐
2705 ows a library
2706 -Widentities
2708 warn about uses of Prelude numeric conversions that are probably
2709 the identity (and hence could be omitted)
2710 -Wimplicit-kind-vars
2712 (deprecated) warn when kind variables are implicitly quantified
2713 over.
2714 -Wimplicit-lift
2716 warn about implicit lift in Template Haskell quotes
2717 -Wimplicit-prelude
2719 warn when the Prelude is implicitly imported
2720 -Wimplicit-rhs-quantification
2722 warn when type variables on the RHS of a type synonym are im‐
2723 plicitly quantified
2724 -Winaccessible-code
2726 warn about inaccessible code
2727 -Wincomplete-export-warnings
2729 warn when some but not all of exports for a name are warned
2730 about
2731 -Wincomplete-patterns
2733 warn when a pattern match could fail
2734 -Wincomplete-record-updates
2736 warn when a record update could fail
2737 -Wincomplete-uni-patterns
2739 warn when a pattern match in a lambda expression, pattern bind‐
2740 ing or a lazy pattern could fail
2741 -Winconsistent-flags
2743 warn when command line options are inconsistent in some way.
2744 -Winconsistent-flags
2746 warn when command line options are inconsistent in some way.
2747 -Winferred-safe-imports
2749 warn when an explicitly Safe Haskell module imports a Safe-In‐
2750 ferred one
2751 -Winline-rule-shadowing
2753 Warn if a rewrite RULE might fail to fire because the function
2754 might be inlined before the rule has a chance to fire. See How
2755 rules interact with INLINE/NOINLINE pragmas.
2756 -Winvalid-haddock
2758 warn when a Haddock comment occurs in an invalid position
2759 -Wloopy-superclass-solve
2761 warn when creating potentially-loopy superclass constraint evi‐
2762 dence
2763 -Wmisplaced-pragmas
2765 warn about uses of file header pragmas in the module body
2766 -Wmissed-extra-shared-lib
2768 Warn when GHCi can't load a shared lib.
2769 -Wmissed-specialisations
2771 warn when specialisation of an imported, overloaded function
2772 fails.
2773 -Wmissed-specializations
2775 alias for -Wmissed-specialisations
2776 -Wmissing-deriving-strategies
2778 warn when a deriving clause is missing a deriving strategy
2779 -Wmissing-export-lists
2781 warn when a module declaration does not explicitly list all ex‐
2782 ports
2783 -Wmissing-exported-pattern-synonym-signatures
2785 warn about pattern synonyms without signatures, only if they are
2786 exported
2787 -Wmissing-exported-signatures
2789 warn about top-level functions without signatures, only if they
2790 are exported
2791 -Wmissing-exported-sigs
2793 (deprecated) warn about top-level functions without signatures,
2794 only if they are exported. takes precedence over -Wmissing-sig‐
2795 natures
2796 -Wmissing-fields
2798 warn when fields of a record are uninitialised
2799 -Wmissing-home-modules
2801 warn when encountering a home module imported, but not listed on
2802 the command line. Useful for cabal to ensure GHC won't pick up
2803 modules, not listed neither in exposed-modules, nor in
2804 other-modules.
2805 -Wmissing-import-lists
2807 warn when an import declaration does not explicitly list all the
2808 names brought into scope
2809 -Wmissing-kind-signatures
2811 warn when type declarations don't have kind signatures nor CUSKs
2812 -Wmissing-local-signatures
2814 warn about polymorphic local bindings without signatures
2815 -Wmissing-local-sigs
2817 (deprecated) warn about polymorphic local bindings without sig‐
2818 natures
2819 -Wmissing-methods
2821 warn when class methods are undefined
2822 -Wmissing-monadfail-instances
2824 (deprecated) Warn when a failable pattern is used in a do-block
2825 that does not have a MonadFail instance.
2826 -Wmissing-pattern-synonym-signatures
2828 warn when pattern synonyms do not have type signatures
2829 -Wmissing-poly-kind-signatures
2831 warn when inferred polykinded type or class declaration don't
2832 have kind signatures nor CUSKs
2833 -Wmissing-role-annotations
2835 warn when type declarations don't have role annotations
2836 -Wmissing-safe-haskell-mode
2838 warn when the Safe Haskell mode is not explicitly specified.
2839 -Wmissing-signatures
2841 warn about top-level functions without signatures
2842 -Wmissing-space-after-bang
2844 (deprecated) Does nothing
2845 -Wmonomorphism-restriction
2847 warn when the Monomorphism Restriction is applied
2848 -Wname-shadowing
2850 warn when names are shadowed
2851 -Wnoncanonical-monad-instances
2853 warn when Applicative or Monad instances have noncanonical defi‐
2854 nitions of return, pure, (>>), or (*>). See flag description in
2855 Warnings and sanity-checking for more details.
2856 -Wnoncanonical-monadfail-instances
2858 (deprecated) warn when Monad or MonadFail instances have non‐
2859 canonical definitions of fail.
2860 -Wnoncanonical-monoid-instances
2862 warn when Semigroup or Monoid instances have noncanonical defi‐
2863 nitions of (<>) or mappend. See flag description in Warnings
2864 and sanity-checking for more details.
2865 -Wnot (deprecated) Alias for -w
2867 -Woperator-whitespace
2869 warn on prefix, suffix, and tight infix uses of infix operators
2870 -Woperator-whitespace-ext-conflict
2872 warn on uses of infix operators that would be parsed differently
2873 were a particular GHC extension enabled
2874 -Worphans
2876 warn when the module contains orphan instance declarations or
2877 rewrite rules
2878 -Woverflowed-literals
2880 warn about literals that will overflow their type
2881 -Woverlapping-patterns
2883 warn about overlapping patterns
2884 -Wpartial-fields
2886 warn when defining a partial record field.
2887 -Wpartial-type-signatures
2889 warn about holes in partial type signatures when
2890 PartialTypeSignatures is enabled. Not applicable when
2891 PartialTypeSignatures is not enabled, in which case errors are
2892 generated for such holes.
2893 -Wprepositive-qualified-module
2895 Report imports with a leading/prepositive "qualified"
2896 -Wredundant-bang-patterns
2898 Warn about redundant bang patterns.
2899 -Wredundant-constraints
2901 Have the compiler warn about redundant constraints in type sig‐
2902 natures.
2903 -Wredundant-record-wildcards
2905 Warn about record wildcard matches when the wildcard binds no
2906 patterns.
2907 -Wredundant-strictness-flags
2909 Warn about redundant strictness flags.
2910 -Wsafe warn if the module being compiled is regarded to be safe.
2912 -Wsemigroup
2914 warn when a Monoid is not Semigroup, and on non- Semigroup defi‐
2915 nitions of (<>)?
2916 -Wsimplifiable-class-constraints
2918 Warn about class constraints in a type signature that can be
2919 simplified using a top-level instance declaration.
2920 -Wstar-binder
2922 warn about binding the (*) type operator despite StarIsType
2923 -Wstar-is-type
2925 warn when * is used to mean Data.Kind.Type
2926 -Wtabs warn if there are tabs in the source file
2928 -Wterm-variable-capture
2930 warn when an implicitly quantified type variable captures a
2931 term's name
2932 -Wtrustworthy-safe
2934 warn if the module being compiled is marked as Trustworthy but
2935 it could instead be marked as Safe, a more informative bound.
2936 -Wtype-defaults
2938 warn when defaulting happens
2939 -Wtype-equality-out-of-scope
2941 warn when type equality a ~ b is used despite being out of scope
2942 -Wtype-equality-requires-operators
2944 warn when type equality a ~ b is used despite being out of scope
2945 -Wtyped-holes
2947 Report warnings when typed hole errors are deferred until run‐
2948 time. See -fdefer-typed-holes.
2949 -Wunbanged-strict-patterns
2951 warn on pattern bind of unlifted variable that is neither bare
2952 nor banged
2953 -Wunicode-bidirectional-format-characters
2955 warn about the usage of unicode bidirectional layout override
2956 characters
2957 -Wunrecognised-pragmas
2959 warn about uses of pragmas that GHC doesn't recognise
2960 -Wunrecognised-warning-flags
2962 throw a warning when an unrecognised -W... flag is encountered
2963 on the command line.
2964 -Wunsafe
2966 warn if the module being compiled is regarded to be unsafe. See
2967 Safe Haskell
2968 -Wunsupported-calling-conventions
2970 warn about use of an unsupported calling convention
2971 -Wunsupported-llvm-version
2973 Warn when using -fllvm with an unsupported version of LLVM.
2974 -Wunticked-promoted-constructors
2976 warn if promoted constructors are not ticked
2977 -Wunused-binds
2979 warn about bindings that are unused. Alias for
2980 -Wunused-top-binds, -Wunused-local-binds and
2981 -Wunused-pattern-binds
2982 -Wunused-do-bind
2984 warn about do bindings that appear to throw away values of types
2985 other than ()
2986 -Wunused-foralls
2988 warn about type variables in user-written forall\s that are un‐
2989 used
2990 -Wunused-imports
2992 warn about unnecessary imports
2993 -Wunused-local-binds
2995 warn about local bindings that are unused
2996 -Wunused-matches
2998 warn about variables in patterns that aren't used
2999 -Wunused-packages
3001 warn when package is requested on command line, but not needed.
3002 -Wunused-pattern-binds
3004 warn about pattern match bindings that are unused
3005 -Wunused-record-wildcards
3007 Warn about record wildcard matches when none of the bound vari‐
3008 ables are used.
3009 -Wunused-top-binds
3011 warn about top-level bindings that are unused
3012 -Wunused-type-patterns
3014 warn about unused type variables which arise from patterns in in
3015 type family and data family instances
3016 -Wwarn make warnings non-fatal
3018 -Wwarnings-deprecations
3020 warn about uses of functions & types that have DEPRECATED prag‐
3021 mas, or WARNING pragmas with the deprecated category. Alias for
3022 -Wdeprecations.
3023 -Wwrong-do-bind
3025 warn about do bindings that appear to throw away monadic values
3026 that you should have bound instead
3027 -Wx-⟨category⟩
3029 warn about uses of functions & types that have WARNING pragmas
3030 with the given category
3031
3033 Copyright 2015. The University Court of the University of Glasgow. All
3034 rights reserved.
3035
3037 https://www.haskell.org/ghc the GHC homepage
3038
3040 The GHC Team
3041
3043 2023, GHC Team
30449.8.1 Nov 12, 2023 GHC(1)