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 -ddump-asm -ddump-asm-con‐
61 flicts -ddump-asm-liveness -ddump-asm-native -ddump-asm-regalloc
62 -ddump-asm-regalloc-stages -ddump-asm-stats -ddump-bcos
63 -ddump-c-backend -ddump-call-arity -ddump-cfg-weights -ddump-cmm
64 -ddump-cmm-caf -ddump-cmm-cbe -ddump-cmm-cfg -ddump-cmm-cps
65 -ddump-cmm-from-stg -ddump-cmm-info -ddump-cmm-opt
66 -ddump-cmm-proc -ddump-cmm-procmap -ddump-cmm-raw
67 -ddump-cmm-sink -ddump-cmm-sp -ddump-cmm-split -ddump-cmm-switch
68 -ddump-cmm-thread-sanitizer -ddump-cmm-verbose -ddump-cmm-ver‐
69 bose-by-proc -ddump-core-stats -ddump-cpr-signatures
70 -ddump-cpranal -ddump-cs-trace -ddump-cse -ddump-debug
71 -ddump-deriv -ddump-ds -ddump-ds-preopt -ddump-ec-trace
72 -ddump-exitify -ddump-faststrings -ddump-file-prefix=⟨str⟩
73 -ddump-foreign -ddump-hie -ddump-hpc -ddump-if-trace -ddump-in‐
74 linings -ddump-js -ddump-json -ddump-late-cc -ddump-llvm
75 -ddump-mod-map -ddump-occur-anal -ddump-opt-cmm -ddump-parsed
76 -ddump-parsed-ast -ddump-prep -ddump-rn -ddump-rn-ast
77 -ddump-rn-stats -ddump-rn-trace -ddump-rtti -ddump-rule-firings
78 -ddump-rule-rewrites -ddump-rules -ddump-simpl -ddump-simpl-it‐
79 erations -ddump-simpl-stats -ddump-simpl-trace -ddump-spec
80 -ddump-splices -ddump-stg -ddump-stg-cg -ddump-stg-final
81 -ddump-stg-from-core -ddump-stg-tags -ddump-stg-unarised
82 -ddump-str-signatures -ddump-stranal -ddump-tc -ddump-tc-ast
83 -ddump-tc-trace -ddump-ticked -ddump-timings -ddump-to-file
84 -ddump-types -ddump-verbose-inlinings -ddump-view-pattern-com‐
85 moning -ddump-worker-wrapper -dfaststring-stats -dhex-word-lit‐
86 erals -dinitial-unique=⟨s⟩ -dinline-check=⟨str⟩ -dipe-stats
87 -dkeep-comments -dlinear-core-lint -dlint -dno-debug-output
88 -ddebug-output -dno-typeable-binds -dppr-case-as-let
89 -dppr-cols=⟨n⟩ -dppr-debug -dppr-user-length -drule-check=⟨str⟩
90 -dshow-passes -dstg-lint -dsuppress-all -dsuppress-coer‐
91 cion-types -dsuppress-coercions -dsuppress-core-sizes -dsup‐
92 press-idinfo -dsuppress-module-prefixes -dsuppress-stg-free-vars
93 -dsuppress-stg-reps -dsuppress-ticks -dsuppress-timestamps
94 -dsuppress-type-applications -dsuppress-type-signatures -dsup‐
95 press-unfoldings -dsuppress-uniques -dsuppress-var-kinds
96 -dtag-inference-checks -dth-dec-file -dunique-increment=⟨i⟩
97 -dverbose-core2core -dverbose-stg2stg -falignment-sanitisation
98 -fcatch-nonexhaustive-cases -fcheck-prim-bounds
99 -fcmm-thread-sanitizer -fdistinct-constructor-tables
100 -fdump-with-ways -finfo-table-map -finfo-table-map-with-fallback
101 -fno-info-table-map-with-fallback -finfo-table-map-with-stack
102 -fno-info-table-map-with-stack -fllvm-fill-undef-with-garbage
103 -fno-info-table-map-with-fallback -finfo-table-map-with-fallback
104 -fno-info-table-map-with-stack -finfo-table-map-with-stack
105 -fproc-alignment -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 -fghci-hist-size=⟨n⟩ -fghci-leak-check
116 -fno-ghci-leak-check -fimplicit-import-qualified -fno-im‐
117 plicit-import-qualified -flocal-ghci-history -fno-lo‐
118 cal-ghci-history -fno-it -fno-no-it -fprint-bind-result
119 -fno-print-bind-result -fprint-evld-with-show -fshow-loaded-mod‐
120 ules -ghci-script -ignore-dot-ghci -no-ignore-dot-ghci -interac‐
121 tive-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 -XFieldSelectors -XFlexibleContexts -XFlexi‐
144 bleInstances -XForeignFunctionInterface -XFunctionalDependencies
145 -XGADTs -XGADTSyntax -XGeneralisedNewtypeDeriving -XGeneralized‐
146 NewtypeDeriving -XGHC2021 -XGHCForeignImportPrim -XHaskell2010
147 -XHaskell98 -XHexFloatLiterals -XImplicitParams -XImportQuali‐
148 fiedPost -XImpredicativeTypes -XIncoherentInstances -XInstance‐
149 Sigs -XInterruptibleFFI -XKindSignatures -XLambdaCase -XLexical‐
150 Negation -XLiberalTypeSynonyms -XLinearTypes -XMagicHash -XMon‐
151 adComprehensions -XMonoLocalBinds -XMultiParamTypeClasses -XMul‐
152 tiWayIf -XNamedFieldPuns -XNamedWildCards -XNegativeLiterals
153 -XNoImplicitPrelude -XNoMonomorphismRestriction -XNonde‐
154 creasingIndentation -XNoPatternGuards -XNoTraditionalRecordSyn‐
155 tax -XNPlusKPatterns -XNullaryTypeClasses -XNumDecimals -XNumer‐
156 icUnderscores -XOverlappingInstances -XOverloadedLabels -XOver‐
157 loadedLists -XOverloadedRecordDot -XOverloadedRecordUpdate
158 -XOverloadedStrings -XPackageImports -XParallelListComp -XPar‐
159 tialTypeSignatures -XPatternSynonyms -XPolyKinds -XPostfixOpera‐
160 tors -XQualifiedDo -XQuantifiedConstraints -XQuasiQuotes
161 -XRank2Types -XRankNTypes -XRebindableSyntax -XRecordWildCards
162 -XRecursiveDo -XRoleAnnotations -XSafe -XScopedTypeVariables
163 -XStandaloneDeriving -XStandaloneKindSignatures -XStarIsType
164 -XStaticPointers -XStrict -XStrictData -XTemplateHaskell -XTem‐
165 plateHaskellQuotes -XTransformListComp -XTrustworthy -XTupleSec‐
166 tions -XTypeApplications -XTypeData -XTypeFamilies -XTypeFamily‐
167 Dependencies -XTypeInType -XTypeOperators -XTypeSynonymInstances
168 -XUnboxedSums -XUnboxedTuples -XUndecidableInstances -XUndecid‐
169 ableSuperClasses -XUnicodeSyntax -XUnliftedDatatypes -XUnlift‐
170 edFFITypes -XUnliftedNewtypes -XUnsafe -XViewPatterns
171 Linking options
173 -c -debug -dylib-install-name ⟨path⟩ -dynamic -dynload -eventlog
174 -fcompact-unwind -fkeep-cafs -flink-rts -fno-embed-manifest
175 -fno-gen-manifest -fno-shared-implib -framework ⟨name⟩ -frame‐
176 work-path ⟨dir⟩ -fsplit-sections -split-sections -fno-split-sec‐
177 tions -fuse-rpaths -fwhole-archive-hs-libs -L ⟨dir⟩ -l ⟨lib⟩
178 -main-is ⟨thing⟩ -no-hs-main -no-pie -pie -no-rtsopts-sugges‐
179 tions -package ⟨name⟩ -pie -no-pie -rdynamic -rt‐
180 sopts[=⟨none|some|all|ignore|ignoreAll⟩] -shared -static -stati‐
181 clib -threaded -with-rtsopts=⟨opts⟩
182 Miscellaneous options
184 -ddump-mod-cycles -fexternal-interpreter -ffamily-applica‐
185 tion-cache -fno-family-application-cache -fglasgow-exts
186 -fno-glasgow-exts -fno-safe-haskell -ghcversion-file ⟨path to
187 ghcversion.h⟩ -H ⟨size⟩ -hidden-module ⟨module name⟩ -j[⟨n⟩]
188 -reexported-module ⟨module name⟩ -this-package-name ⟨unit-id⟩
189 -unit @⟨filename⟩ -working-dir ⟨dir⟩
190 Modes of operation
192 --frontend ⟨module⟩ --help -? --info --interactive --make --nu‐
193 meric-version --print-booter-version --print-build-platform
194 --print-c-compiler-flags --print-c-compiler-link-flags
195 --print-debug-on --print-global-package-db --print-have-inter‐
196 preter --print-have-native-code-generator --print-host-platform
197 --print-ld-flags --print-leading-underscore --print-libdir
198 --print-object-splitting-supported --print-project-git-commit-id
199 --print-project-version --print-rts-ways --print-stage
200 --print-support-smp --print-tables-next-to-code --print-tar‐
201 get-platform --print-unregisterised --run ⟨file⟩ --show-iface
202 ⟨file⟩ --show-options --supported-extensions --supported-lan‐
203 guages --version -V -e ⟨expr⟩ -M -shared
204 Individual optimizations
206 -fasm-shortcutting -fno-asm-shortcutting -fbinary-blob-thresh‐
207 old=⟨n⟩ -fblock-layout-cfg -fno-block-layout-cfg -fblock-lay‐
208 out-weightless -fno-block-layout-weightless -fblock-lay‐
209 out-weights -fcall-arity -fno-call-arity -fcase-folding
210 -fno-case-folding -fcase-merge -fno-case-merge -fcmm-con‐
211 trol-flow -fno-cmm-control-flow -fcmm-elim-common-blocks
212 -fno-cmm-elim-common-blocks -fcmm-sink -fno-cmm-sink
213 -fcmm-static-pred -fno-cmm-static-pred -fcore-constant-folding
214 -fno-core-constant-folding -fcpr-anal -fno-cpr-anal -fcross-mod‐
215 ule-specialise -fno-cross-module-specialise -fcse -fno-cse
216 -fdicts-cheap -fno-dicts-cheap -fdicts-strict -fno-dicts-strict
217 -fdmd-tx-dict-sel -fno-dmd-tx-dict-sel -fdmd-unbox-width=⟨n⟩
218 -fdo-eta-reduction -fno-do-eta-reduction -fdo-lambda-eta-expan‐
219 sion -fno-do-lambda-eta-expansion -feager-blackholing -fen‐
220 able-rewrite-rules -fno-enable-rewrite-rules -fexcess-precision
221 -fno-excess-precision -fexitification -fno-exitification -fex‐
222 pose-all-unfoldings -fno-expose-all-unfoldings -ffloat-in
223 -fno-float-in -ffull-laziness -fno-full-laziness -ffun-to-thunk
224 -fno-fun-to-thunk -fignore-asserts -fno-ignore-asserts -fig‐
225 nore-interface-pragmas -fno-ignore-interface-pragmas -fin‐
226 line-generics -fno-inline-generics -finline-generics-aggres‐
227 sively -fno-inline-generics-aggressively -flate-dmd-anal
228 -fno-late-dmd-anal -flate-specialise -fno-late-specialise -flib‐
229 erate-case -fno-liberate-case -fliberate-case-threshold=⟨n⟩
230 -fno-liberate-case-threshold -fllvm-pass-vectors-in-regs -flo‐
231 cal-float-out -fno-local-float-out -flocal-float-out-top-level
232 -fno-local-float-out-top-level -floopification -fno-loopifica‐
233 tion -fmax-inline-alloc-size=⟨n⟩ -fmax-inline-memcpy-insns=⟨n⟩
234 -fmax-inline-memset-insns=⟨n⟩ -fmax-simplifier-iterations=⟨n⟩
235 -fmax-uncovered-patterns=⟨n⟩ -fmax-worker-args=⟨n⟩ -fno-opt-co‐
236 ercion -fno-pre-inlining -fno-state-hack -fomit-interface-prag‐
237 mas -fno-omit-interface-pragmas -fomit-yields -fno-omit-yields
238 -foptimal-applicative-do -fno-optimal-applicative-do -fpedan‐
239 tic-bottoms -fno-pedantic-bottoms -fpolymorphic-specialisation
240 -fno-polymorphic-specialisation -fregs-graph -fno-regs-graph
241 -fregs-iterative -fno-regs-iterative -fsimpl-tick-factor=⟨n⟩
242 -fsimplifier-phases=⟨n⟩ -fsolve-constant-dicts -fno-solve-con‐
243 stant-dicts -fspec-constr -fno-spec-constr -fspec-con‐
244 str-count=⟨n⟩ -fno-spec-constr-count -fspec-constr-keen
245 -fno-spec-constr-keen -fspec-constr-threshold=⟨n⟩ -fno-spec-con‐
246 str-threshold -fspecialise -fno-specialise -fspecialise-aggres‐
247 sively -fno-specialise-aggressively -fstatic-argument-transfor‐
248 mation -fno-static-argument-transformation -fstg-cse
249 -fno-stg-cse -fstg-lift-lams -fno-stg-lift-lams
250 -fstg-lift-lams-known -fno-stg-lift-lams-known
251 -fstg-lift-lams-non-rec-args -fstg-lift-lams-non-rec-args-any
252 -fstg-lift-lams-rec-args -fstg-lift-lams-rec-args-any -fstrict‐
253 ness -fno-strictness -fstrictness-before=⟨n⟩ -fun‐
254 box-small-strict-fields -fno-unbox-small-strict-fields -fun‐
255 box-strict-fields -fno-unbox-strict-fields -funfold‐
256 ing-case-scaling=⟨n⟩ -funfolding-case-threshold=⟨n⟩ -funfold‐
257 ing-creation-threshold=⟨n⟩ -funfolding-dict-discount=⟨n⟩ -fun‐
258 folding-fun-discount=⟨n⟩ -funfolding-keeness-factor=⟨n⟩ -fun‐
259 folding-use-threshold=⟨n⟩ -fworker-wrapper -fworker-wrapper-cbv
260 Optimization levels
262 -O -O1 -O0 -O0 -O2 -O0 -O⟨n⟩ -O0
263 Package options
265 -clear-package-db -distrust ⟨pkg⟩ -distrust-all-packages -fpack‐
266 age-trust -global-package-db -hide-all-packages -hide-package
267 ⟨pkg⟩ -ignore-package ⟨pkg⟩ -no-auto-link-packages
268 -no-global-package-db -no-user-package-db -package ⟨pkg⟩ -pack‐
269 age-db ⟨file⟩ -package-env ⟨file⟩|⟨name⟩ -package-id ⟨unit-id⟩
270 -this-unit-id ⟨unit-id⟩ -trust ⟨pkg⟩ -user-package-db
271 Phases of compilation
273 --merge-objs -C -c -E -F -S -x ⟨suffix⟩
274 Overriding external programs
276 -pgma ⟨cmd⟩ -pgmc ⟨cmd⟩ -pgmcxx ⟨cmd⟩ -pgmdll ⟨cmd⟩ -pgmF ⟨cmd⟩
277 -pgmi ⟨cmd⟩ -pgminstall_name_tool ⟨cmd⟩ -pgmL ⟨cmd⟩ -pgml ⟨cmd⟩
278 -pgmlc ⟨cmd⟩ -pgmlm ⟨cmd⟩ -pgmlo ⟨cmd⟩ -pgmotool ⟨cmd⟩ -pgmP
279 ⟨cmd⟩ -pgms ⟨cmd⟩ -pgmwindres ⟨cmd⟩
280 Phase-specific options
282 -opta ⟨option⟩ -optc ⟨option⟩ -optcxx ⟨option⟩ -optdll ⟨option⟩
283 -optF ⟨option⟩ -opti ⟨option⟩ -optL ⟨option⟩ -optl ⟨option⟩
284 -optlc ⟨option⟩ -optlm ⟨option⟩ -optlo ⟨option⟩ -optP ⟨option⟩
285 -optwindres ⟨option⟩ -pgmc-supports-no-pie -pgml-supports-no-pie
286 Platform-specific options
288 -mavx -mavx2 -mavx512cd -mavx512er -mavx512f -mavx512pf -mbmi
289 -mbmi2 -msse -msse2 -msse3 -msse4 -msse4.2
290 Compiler plugins
292 -fclear-plugins -fplugin-library=⟨file-path⟩;⟨unit-id⟩;⟨mod‐
293 ule⟩;⟨args⟩ -fplugin-opt=⟨module⟩:⟨args⟩ -fplugin-trustworthy
294 -fplugin=⟨module⟩ -hide-all-plugin-packages -plugin-package
295 ⟨pkg⟩ -plugin-package-id ⟨pkg-id⟩
296 Profiling
298 -auto -auto-all -caf-all -fno-prof-count-entries
299 -fprof-count-entries -fprof-auto -fno-prof-auto
300 -fprof-auto-calls -fno-prof-auto -fprof-auto-exported
301 -fno-prof-auto -fprof-auto-top -fno-prof-auto -fprof-cafs
302 -fno-prof-cafs -fprof-callers=⟨name⟩ -fprof-late -fno-prof-late
303 -fprof-late-inline -fno-prof-late-inline -fprof-manual
304 -fno-prof-manual -no-auto -no-auto-all -no-caf-all -prof -ticky
305 -ticky-allocd -ticky-ap-thunk -ticky-dyn-thunk -ticky-LNE
306 -ticky-tag-checks
307 Program coverage
309 -fhpc -hpcdir⟨dir⟩
310 Recompilation checking
312 -exclude-module=⟨file⟩ -fforce-recomp -fno-force-recomp -fig‐
313 nore-hpc-changes -fno-ignore-hpc-changes -fignore-optim-changes
314 -fno-ignore-optim-changes -include-cpp-deps -include-pkg-deps
315 Redirecting output
317 -dep-makefile ⟨file⟩ -dep-suffix ⟨suffix⟩ -dumpdir ⟨dir⟩ -dyn‐
318 hisuf ⟨suffix⟩ -dyno ⟨file⟩ -dynohi ⟨file⟩ -dynosuf ⟨suffix⟩
319 -hcsuf ⟨suffix⟩ -hidir ⟨dir⟩ -hiedir ⟨dir⟩ -hiesuf ⟨suffix⟩
320 -hisuf ⟨suffix⟩ -o ⟨file⟩ -odir ⟨dir⟩ -ohi ⟨file⟩ -osuf ⟨suffix⟩
321 -outputdir ⟨dir⟩ -stubdir ⟨dir⟩
322 Temporary files
324 -tmpdir ⟨dir⟩
325 Verbosity options
327 -fabstract-refinement-hole-fits -fno-abstract-refine‐
328 ment-hole-fits -fdefer-diagnostics -fdiagnostics-color=⟨al‐
329 ways|auto|never⟩ -fdiagnostics-show-caret -fno-diagnos‐
330 tics-show-caret -ferror-spans -fhide-source-paths -fkeep-going
331 -fmax-refinement-hole-fits=⟨n⟩ -fno-max-refinement-hole-fits
332 -fmax-relevant-binds=⟨n⟩ -fno-max-relevant-binds
333 -fmax-valid-hole-fits=⟨n⟩ -fno-max-valid-hole-fits
334 -fno-show-valid-hole-fits -fno-sort-valid-hole-fits
335 -fsort-valid-hole-fits -fprint-axiom-incomps -fno-print-ax‐
336 iom-incomps -fprint-equality-relations -fno-print-equality-rela‐
337 tions -fprint-expanded-synonyms -fno-print-expanded-synonyms
338 -fprint-explicit-coercions -fno-print-explicit-coercions
339 -fprint-explicit-foralls -fno-print-explicit-foralls -fprint-ex‐
340 plicit-kinds -fno-print-explicit-kinds -fprint-explicit-run‐
341 time-reps -fno-print-explicit-runtime-reps -fprint-potential-in‐
342 stances -fno-print-potential-instances -fprint-redundant-promo‐
343 tion-ticks -fno-print-redundant-promotion-ticks -fprint-type‐
344 checker-elaboration -fno-print-typechecker-elaboration
345 -fprint-unicode-syntax -fno-print-unicode-syntax -frefine‐
346 ment-level-hole-fits=⟨n⟩ -fno-refinement-level-hole-fits -fre‐
347 verse-errors -fno-reverse-errors -fshow-docs-of-hole-fits
348 -fno-show-docs-of-hole-fits -fshow-error-context -fno-show-er‐
349 ror-context -fshow-hole-constraints
350 -fshow-hole-matches-of-hole-fits
351 -fno-show-hole-matches-of-hole-fits -fshow-prove‐
352 nance-of-hole-fits -fno-show-provenance-of-hole-fits
353 -fshow-type-app-of-hole-fits -fno-show-type-app-of-hole-fits
354 -fshow-type-app-vars-of-hole-fits
355 -fno-show-type-app-vars-of-hole-fits -fshow-type-of-hole-fits
356 -fno-show-type-of-hole-fits -fsort-by-size-hole-fits
357 -fno-sort-by-size-hole-fits -fsort-by-subsumption-hole-fits
358 -fno-sort-by-subsumption-hole-fits -funclutter-valid-hole-fits
359 -Rghc-timing -v -v⟨n⟩
360 Warnings
362 -fdefer-out-of-scope-variables -fno-defer-out-of-scope-variables
363 -fdefer-type-errors -fno-defer-type-errors -fdefer-typed-holes
364 -fno-defer-typed-holes -fenable-th-splice-warnings -fno-en‐
365 able-th-splice-warnings -fhelpful-errors -fno-helpful-errors
366 -fmax-pmcheck-models=⟨n⟩ -fshow-warning-groups -fno-show-warn‐
367 ing-groups -fvia-C -W -w -w -Wall -w -Wall-missed-specialisa‐
368 tions -Wno-all-missed-specialisations -Wall-missed-specializa‐
369 tions -Wno-all-missed-specializations -Wambiguous-fields
370 -Wauto-orphans -Wcompat -Wno-compat -Wcompat-unqualified-imports
371 -Wno-compat-unqualified-imports -Wcpp-undef -Wdefault -Wde‐
372 ferred-out-of-scope-variables -Wno-deferred-out-of-scope-vari‐
373 ables -Wdeferred-type-errors -Wno-deferred-type-errors -Wdepre‐
374 cated-flags -Wno-deprecated-flags -Wdeprecations -Wno-depreca‐
375 tions -Wderiving-defaults -Wno-deriving-defaults -Wderiving-ty‐
376 peable -Wno-deriving-typeable -Wdodgy-exports -Wno-dodgy-exports
377 -Wdodgy-foreign-imports -Wno-dodgy-foreign-imports -Wdodgy-im‐
378 ports -Wno-dodgy-imports -Wduplicate-constraints -Wno-dupli‐
379 cate-constraints -Wduplicate-exports -Wno-duplicate-exports
380 -Wempty-enumerations -Wno-empty-enumerations -Werror -Wwarn
381 -Weverything -Wextra -w -Wforall-identifier -Wno-forall-identi‐
382 fier -Wgadt-mono-local-binds -Wno-gadt-mono-local-binds
383 -Whi-shadowing -Wno-hi-shadowing -Widentities -Wno-identities
384 -Wimplicit-kind-vars -Wno-implicit-kind-vars -Wimplicit-lift
385 -Wno-implicit-lift -Wimplicit-prelude -Wno-implicit-prelude
386 -Winaccessible-code -Wno-inaccessible-code -Wincomplete-patterns
387 -Wno-incomplete-patterns -Wincomplete-record-updates -Wno-incom‐
388 plete-record-updates -Wincomplete-uni-patterns -Wno-incom‐
389 plete-uni-patterns -Winferred-safe-imports -Wno-in‐
390 ferred-safe-imports -Winline-rule-shadowing -Wno-in‐
391 line-rule-shadowing -Winvalid-haddock -Wno-invalid-haddock
392 -Wloopy-superclass-solve -Wno-loopy-superclass-solve -Wmis‐
393 placed-pragmas -Wno-misplaced-pragmas -Wmissed-extra-shared-lib
394 -Wno-missed-extra-shared-lib -Wmissed-specialisations
395 -Wno-missed-specialisations -Wmissed-specializations
396 -Wno-missed-specializations -Wmissing-deriving-strategies
397 -Wno-missing-deriving-strategies -Wmissing-export-lists
398 -Wno-missing-export-lists -Wmissing-exported-pattern-syn‐
399 onym-signatures -Wno-missing-exported-pattern-synonym-signatures
400 -Wmissing-exported-signatures -Wno-missing-exported-signatures
401 -Wmissing-exported-sigs -Wno-missing-exported-sigs -Wmiss‐
402 ing-fields -Wno-missing-fields -Wmissing-home-modules -Wno-miss‐
403 ing-home-modules -Wmissing-import-lists -Wno-missing-im‐
404 port-lists -Wmissing-kind-signatures -Wno-missing-kind-signa‐
405 tures -Wmissing-local-signatures -Wno-missing-local-signatures
406 -Wmissing-local-sigs -Wno-missing-local-sigs -Wmissing-methods
407 -Wno-missing-methods -Wmissing-monadfail-instances -Wno-miss‐
408 ing-monadfail-instances -Wmissing-pattern-synonym-signatures
409 -Wno-missing-pattern-synonym-signatures -Wmiss‐
410 ing-safe-haskell-mode -Wno-missing-safe-haskell-mode -Wmiss‐
411 ing-signatures -Wno-missing-signatures -Wmissing-space-af‐
412 ter-bang -Wmonomorphism-restriction -Wno-monomorphism-restric‐
413 tion -Wname-shadowing -Wno-name-shadowing -Wno-compat -Wcompat
414 -Wnoncanonical-monad-instances -Wno-noncanonical-monad-instances
415 -Wnoncanonical-monadfail-instances -Wno-noncanonical-monad‐
416 fail-instances -Wnoncanonical-monoid-instances -Wno-noncanoni‐
417 cal-monoid-instances -Wnot -Woperator-whitespace -Wno-opera‐
418 tor-whitespace -Woperator-whitespace-ext-conflict -Wno-opera‐
419 tor-whitespace-ext-conflict -Worphans -Wno-orphans -Wover‐
420 flowed-literals -Wno-overflowed-literals -Woverlapping-patterns
421 -Wno-overlapping-patterns -Wpartial-fields -Wno-partial-fields
422 -Wpartial-type-signatures -Wno-partial-type-signatures -Wprepos‐
423 itive-qualified-module -Wno-prepositive-qualified-module -Wre‐
424 dundant-bang-patterns -Wno-redundant-bang-patterns -Wredun‐
425 dant-constraints -Wno-redundant-constraints -Wredun‐
426 dant-record-wildcards -Wno-redundant-record-wildcards -Wredun‐
427 dant-strictness-flags -Wno-redundant-strictness-flags -Wsafe
428 -Wno-safe -Wsemigroup -Wno-semigroup -Wsimplifiable-class-con‐
429 straints -Wno-simplifiable-class-constraints -Wstar-binder
430 -Wno-star-binder -Wstar-is-type -Wno-star-is-type -Wtabs
431 -Wno-tabs -Wtrustworthy-safe -Wno-safe -Wtype-defaults
432 -Wno-type-defaults -Wtype-equality-out-of-scope -Wno-type-equal‐
433 ity-out-of-scope -Wtype-equality-requires-operators
434 -Wno-type-equality-requires-operators -Wtyped-holes
435 -Wno-typed-holes -Wunbanged-strict-patterns -Wno-un‐
436 banged-strict-patterns -Wunicode-bidirectional-format-characters
437 -Wunrecognised-pragmas -Wno-unrecognised-pragmas -Wunrecog‐
438 nised-warning-flags -Wno-unrecognised-warning-flags -Wunsafe
439 -Wno-unsafe -Wunsupported-calling-conventions -Wno-unsup‐
440 ported-calling-conventions -Wunsupported-llvm-version
441 -Wno-monomorphism-restriction -Wunticked-promoted-constructors
442 -Wno-unticked-promoted-constructors -Wunused-binds -Wno-un‐
443 used-binds -Wunused-do-bind -Wno-unused-do-bind -Wunused-foralls
444 -Wno-unused-foralls -Wunused-imports -Wno-unused-imports
445 -Wunused-local-binds -Wno-unused-local-binds -Wunused-matches
446 -Wno-unused-matches -Wunused-packages -Wno-unused-packages
447 -Wunused-pattern-binds -Wno-unused-pattern-binds
448 -Wunused-record-wildcards -Wno-unused-record-wildcards
449 -Wunused-top-binds -Wno-unused-top-binds -Wunused-type-patterns
450 -Wno-unused-type-patterns -Wwarn -Werror -Wwarnings-deprecations
451 -Wno-warnings-deprecations -Wwrong-do-bind -Wno-wrong-do-bind
452 Code generation
454 -dynamic-too
455 Build dynamic object files as well as static object files during
456 compilation
457 -fasm Use the native code generator
459 -fbyte-code
461 Generate byte-code
462 -fbyte-code-and-object-code
464 Generate object code and byte-code
465 -fexpose-internal-symbols
467 Produce symbols for all functions, including internal functions.
468 -fexternal-dynamic-refs
470 Generate code for linking against dynamic libraries
471 -fllvm Compile using the LLVM code generator
473 -fno-code
475 Omit code generation
476 -fobject-code
478 Generate object code
479 -fPIC Generate position-independent code (where available)
481 -fPIE Generate code for a position-independent executable (where
483 available)
484 -fprefer-byte-code
486 Use byte-code if it is available to evaluate TH splices
487 -fwrite-if-simplified-core
489 Write an interface file containing the simplified core of the
490 module.
491 -fwrite-interface
493 Always write interface files
494 -split-objs
496 Split generated object files into smaller files
497 Debugging the compiler
499 -dasm-lint
500 ASM pass sanity checking
501 -dcmm-lint
503 C-\- pass sanity checking
504 -dcore-lint
506 Turn on internal sanity checking
507 -ddump-asm
509 Dump final assembly
510 -ddump-asm-conflicts
512 Dump register conflicts from the register allocator.
513 -ddump-asm-liveness
515 Dump assembly augmented with register liveness
516 -ddump-asm-native
518 Dump initial assembly
519 -ddump-asm-regalloc
521 Dump the result of register allocation
522 -ddump-asm-regalloc-stages
524 Dump the build/spill stages of the -fregs-graph register alloca‐
525 tor.
526 -ddump-asm-stats
528 Dump statistics from the register allocator.
529 -ddump-bcos
531 Dump interpreter byte code
532 -ddump-c-backend
534 Dump C code produced by the C (unregisterised) backend.
535 -ddump-call-arity
537 Dump output of the call arity analysis pass.
538 -ddump-cfg-weights
540 Dump the assumed weights of the CFG.
541 -ddump-cmm
543 Dump the final C-\- output
544 -ddump-cmm-caf
546 Dump the results of the C-\- CAF analysis pass.
547 -ddump-cmm-cbe
549 Dump the results of common block elimination
550 -ddump-cmm-cfg
552 Dump the results of the C-\- control flow optimisation pass.
553 -ddump-cmm-cps
555 Dump the results of the CPS pass
556 -ddump-cmm-from-stg
558 Dump STG-to-C-\- output
559 -ddump-cmm-info
561 Dump the results of the C-\- info table augmentation pass.
562 -ddump-cmm-opt
564 Dump the results of C-\- to C-\- optimising passes
565 -ddump-cmm-proc
567 Dump the results of proc-point analysis
568 -ddump-cmm-procmap
570 Dump the results of the C-\- proc-point map pass.
571 -ddump-cmm-raw
573 Dump raw C-\-
574 -ddump-cmm-sink
576 Dump the results of the C-\- sinking pass.
577 -ddump-cmm-sp
579 Dump the results of the C-\- stack layout pass.
580 -ddump-cmm-split
582 Dump the results of the C-\- proc-point splitting pass.
583 -ddump-cmm-switch
585 Dump the results of switch lowering passes
586 -ddump-cmm-thread-sanitizer
588 Dump the results of the C-\- ThreadSanitizer elaboration pass.
589 -ddump-cmm-verbose
591 Write output from main C-\- pipeline passes to files
592 -ddump-cmm-verbose-by-proc
594 Show output from main C-\- pipeline passes (grouped by proc)
595 -ddump-core-stats
597 Print a one-line summary of the size of the Core program at the
598 end of the optimisation pipeline
599 -ddump-cpr-signatures
601 Dump CPR signatures
602 -ddump-cpranal
604 Dump CPR analysis output
605 -ddump-cs-trace
607 Trace constraint solver
608 -ddump-cse
610 Dump CSE output
611 -ddump-debug
613 Dump generated DWARF debug information
614 -ddump-deriv
616 Dump deriving output
617 -ddump-ds
619 Dump desugarer output.
620 -ddump-ec-trace
622 Trace exhaustiveness checker
623 -ddump-exitify
625 Dump output of the exitification pass.
626 -ddump-faststrings
628 Dump the whole FastString table when finished
629 -ddump-file-prefix=⟨str⟩
631 Set the prefix of the filenames used for debugging output.
632 -ddump-foreign
634 Dump foreign export stubs
635 -ddump-hie
637 Dump the hie file syntax tree
638 -ddump-hpc
640 An alias for -ddump-ticked.
641 -ddump-if-trace
643 Trace interface files
644 -ddump-inlinings
646 Dump inlinings performed by the simplifier.
647 -ddump-js
649 Dump final JavaScript code
650 -ddump-json
652 Dump error messages as JSON documents
653 -ddump-late-cc
655 Dump core with late cost centres added
656 -ddump-llvm
658 Dump LLVM intermediate code.
659 -ddump-mod-map
661 Dump the state of the module mapping database.
662 -ddump-occur-anal
664 Dump occurrence analysis output
665 -ddump-opt-cmm
667 Dump the results of C-\- to C-\- optimising passes
668 -ddump-parsed
670 Dump parse tree
671 -ddump-parsed-ast
673 Dump parser output as a syntax tree
674 -ddump-prep
676 Dump prepared core
677 -ddump-rn
679 Dump renamer output
680 -ddump-rn-ast
682 Dump renamer output as a syntax tree
683 -ddump-rn-stats
685 Renamer stats
686 -ddump-rn-trace
688 Trace renamer
689 -ddump-rtti
691 Trace runtime type inference
692 -ddump-rule-firings
694 Dump rule firing info
695 -ddump-rule-rewrites
697 Dump detailed rule firing info
698 -ddump-rules
700 Dump rewrite rules
701 -ddump-simpl
703 Dump final simplifier output
704 -ddump-simpl-iterations
706 Dump output from each simplifier iteration
707 -ddump-simpl-stats
709 Dump simplifier stats
710 -ddump-simpl-trace
712 Dump trace messages in simplifier
713 -ddump-spec
715 Dump specialiser output
716 -ddump-splices
718 Dump TH spliced expressions, and what they evaluate to
719 -ddump-stg
721 (deprecated) Alias for -ddump-stg-from-core
722 -ddump-stg-cg
724 Show output after Stg2Stg
725 -ddump-stg-final
727 Show output of last STG pass.
728 -ddump-stg-from-core
730 Show CoreToStg output
731 -ddump-stg-tags
733 Show output of the tag inference pass.
734 -ddump-stg-unarised
736 Show unarised STG
737 -ddump-str-signatures
739 Dump top-level demand signatures
740 -ddump-stranal
742 Dump demand analysis output
743 -ddump-tc
745 Dump typechecker output
746 -ddump-tc-ast
748 Dump typechecker output as a syntax tree
749 -ddump-tc-trace
751 Trace typechecker
752 -ddump-ticked
754 Dump the code instrumented by HPC (Observing Code Coverage).
755 -ddump-timings
757 Dump per-pass timing and allocation statistics
758 -ddump-to-file
760 Dump to files instead of stdout
761 -ddump-types
763 Dump type signatures
764 -ddump-verbose-inlinings
766 Dump all considered inlinings
767 -ddump-view-pattern-commoning
769 Dump commoned view patterns
770 -ddump-worker-wrapper
772 Dump worker-wrapper output
773 -dfaststring-stats
775 Show statistics for fast string usage when finished
776 -dhex-word-literals
778 Print values of type Word# in hexadecimal.
779 -dinitial-unique=⟨s⟩
781 Start UniqSupply allocation from ⟨s⟩.
782 -dinline-check=⟨str⟩
784 Dump information about inlining decisions
785 -dipe-stats
787 Show statistics about IPE information
788 -dkeep-comments
790 Include comments in the parser. Useful in combination with
791 -ddump-parsed-ast.
792 -dlinear-core-lint
794 Turn on internal sanity checking
795 -dlint Enable several common internal sanity checkers
797 -dno-debug-output
799 Suppress unsolicited debugging output
800 -dno-typeable-binds
802 Don't generate bindings for Typeable methods
803 -dppr-case-as-let
805 Print single alternative case expressions as strict lets.
806 -dppr-cols=⟨n⟩
808 Set the width of debugging output. For example -dppr-cols200
809 -dppr-debug
811 Turn on debug printing (more verbose)
812 -dppr-user-length
814 Set the depth for printing expressions in error msgs
815 -drule-check=⟨str⟩
817 Dump information about potential rule application
818 -dshow-passes
820 Print out each pass name as it happens
821 -dstg-lint
823 STG pass sanity checking
824 -dsuppress-all
826 In dumps, suppress everything (except for uniques) that is sup‐
827 pressible.
828 -dsuppress-coercion-types
830 Suppress the printing of coercion types in Core dumps to make
831 them shorter
832 -dsuppress-coercions
834 Suppress the printing of coercions in Core dumps to make them
835 shorter
836 -dsuppress-core-sizes
838 Suppress the printing of core size stats per binding (since 9.4)
839 -dsuppress-idinfo
841 Suppress extended information about identifiers where they are
842 bound
843 -dsuppress-module-prefixes
845 Suppress the printing of module qualification prefixes
846 -dsuppress-stg-free-vars
848 Suppress the printing of closure free variable lists in STG out‐
849 put
850 -dsuppress-stg-reps
852 Suppress rep annotations on STG args.
853 -dsuppress-ticks
855 Suppress "ticks" in the pretty-printer output.
856 -dsuppress-timestamps
858 Suppress timestamps in dumps
859 -dsuppress-type-applications
861 Suppress type applications
862 -dsuppress-type-signatures
864 Suppress type signatures
865 -dsuppress-unfoldings
867 Suppress the printing of the stable unfolding of a variable at
868 its binding site
869 -dsuppress-uniques
871 Suppress the printing of uniques in debug output (easier to use
872 diff)
873 -dsuppress-var-kinds
875 Suppress the printing of variable kinds
876 -dtag-inference-checks
878 Affirm tag inference results are correct at runtime.
879 -dth-dec-file
881 Dump evaluated TH declarations into *.th.hs files
882 -dunique-increment=⟨i⟩
884 Set the increment for the generated Unique's to ⟨i⟩.
885 -dverbose-core2core
887 Show output from each core-to-core pass
888 -dverbose-stg2stg
890 Show output from each STG-to-STG pass
891 -falignment-sanitisation
893 Compile with alignment checks for all info table dereferences.
894 -fcatch-nonexhaustive-cases
896 Add a default error alternative to case expressions without a
897 default alternative.
898 -fcheck-prim-bounds
900 Instrument array primops with bounds checks.
901 -fcmm-thread-sanitizer
903 Enable ThreadSanitizer instrumentation of memory accesses.
904 -fdistinct-constructor-tables
906 Generate a fresh info table for each usage of a data construc‐
907 tor.
908 -fdump-with-ways
910 Include the tag of the enabled ways in the extension of dump
911 files.
912 -finfo-table-map
914 Embed a lookup table in the generated binary which maps the ad‐
915 dress of an info table to the source position the closure origi‐
916 nated from.
917 -finfo-table-map-with-fallback
919 Include info tables with no source location information in the
920 info table map.
921 -finfo-table-map-with-stack
923 Include info tables for STACK closures in the info table map.
924 -fllvm-fill-undef-with-garbage
926 Intruct LLVM to fill dead STG registers with garbage
927 -fno-info-table-map-with-fallback
929 Omit info tables with no source location information from the
930 info table map.
931 -fno-info-table-map-with-stack
933 Omit info tables for STACK closures from the info table map.
934 -fproc-alignment
936 Align functions at given boundary.
937 -g Produce DWARF debug information in compiled object files. ⟨n⟩
939 can be 0, 1, or 2, with higher numbers producing richer output.
940 If ⟨n⟩ is omitted, level 2 is assumed.
941 C pre-processor
943 -cpp Run the C pre-processor on Haskell source files
944 -D⟨symbol⟩[=⟨value⟩]
946 Define a symbol in the C pre-processor
947 -I⟨dir⟩
949 Add ⟨dir⟩ to the directory search list for #include files
950 -U⟨symbol⟩
952 Undefine a symbol in the C pre-processor
953 Finding imports
955 -i Empty the import directory list
956 -i⟨dir⟩[:⟨dir⟩]*
958 add ⟨dir⟩, ⟨dir2⟩, etc. to import path
959 Interactive mode
961 -fbreak-on-error
962 Break on uncaught exceptions and errors
963 -fbreak-on-exception
965 Break on any exception thrown
966 -fghci-hist-size=⟨n⟩
968 Set the number of entries GHCi keeps for :history. See The GHCi
969 Debugger.
970 -fghci-leak-check
972 (Debugging only) check for space leaks when loading new modules
973 in GHCi.
974 -fimplicit-import-qualified
976 Put in scope qualified identifiers for every loaded module
977 -flocal-ghci-history
979 Use current directory for the GHCi command history file
980 .ghci-history.
981 -fno-it
983 No longer set the special variable it.
984 -fprint-bind-result
986 Turn on printing of binding results in GHCi
987 -fprint-evld-with-show
989 Instruct :print to use Show instances where possible.
990 -fshow-loaded-modules
992 Show the names of modules that GHCi loaded after a :load com‐
993 mand.
994 -ghci-script
996 Read additional .ghci files
997 -ignore-dot-ghci
999 Disable reading of .ghci files
1000 -interactive-print ⟨name⟩
1002 Select the function to use for printing evaluated expressions in
1003 GHCi
1004 Interface files
1006 --show-iface ⟨file⟩
1007 See Modes of operation.
1008 -ddump-hi
1010 Dump the new interface to stdout
1011 -ddump-hi-diffs
1013 Show the differences vs. the old interface
1014 -ddump-minimal-imports
1016 Dump a minimal set of imports
1017 Keeping intermediate files
1019 -keep-hc-file
1020 Retain intermediate .hc files.
1021 -keep-hi-files
1023 Retain intermediate .hi files (the default).
1024 -keep-hscpp-file
1026 Retain intermediate .hscpp files.
1027 -keep-llvm-file
1029 Retain intermediate LLVM .ll files. Implies -fllvm.
1030 -keep-o-files
1032 Retain intermediate .o files (the default).
1033 -keep-s-file
1035 Retain intermediate .s files.
1036 -keep-tmp-files
1038 Retain all intermediate temporary files.
1039 Language options
1041 -XAllowAmbiguousTypes
1042 Allow the user to write ambiguous types, and the type inference
1043 engine to infer them.
1044 -XApplicativeDo
1046 Enable Applicative do-notation desugaring
1047 -XArrows
1049 Enable arrow notation extension
1050 -XBangPatterns
1052 Enable bang patterns.
1053 -XBinaryLiterals
1055 Enable support for binary literals.
1056 -XBlockArguments
1058 Allow do blocks and other constructs as function arguments.
1059 -XCApiFFI
1061 Enable the CAPI calling convention.
1062 -XConstrainedClassMethods
1064 Enable constrained class methods.
1065 -XConstraintKinds
1067 Enable a kind of constraints.
1068 -XCPP Enable the C preprocessor.
1070 -XCUSKs
1072 Enable detection of complete user-supplied kind signatures.
1073 -XDataKinds
1075 Enable datatype promotion.
1076 -XDatatypeContexts
1078 Allow contexts on data types.
1079 -XDeepSubsumption
1081 Enable deep subsumption
1082 -XDefaultSignatures
1084 Enable default signatures.
1085 -XDeriveAnyClass
1087 Enable deriving for any class.
1088 -XDeriveDataTypeable
1090 Enable deriving for the Data class.
1091 -XDeriveFoldable
1093 Enable deriving for the Foldable class. Implied by
1094 DeriveTraversable.
1095 -XDeriveFunctor
1097 Enable deriving for the Functor class. Implied by
1098 DeriveTraversable.
1099 -XDeriveGeneric
1101 Enable deriving for the Generic class.
1102 -XDeriveLift
1104 Enable deriving for the Lift class
1105 -XDeriveTraversable
1107 Enable deriving for the Traversable class. Implies
1108 DeriveFunctor and DeriveFoldable.
1109 -XDerivingStrategies
1111 Enables deriving strategies.
1112 -XDerivingVia
1114 Enable deriving instances via types of the same runtime repre‐
1115 sentation. Implies DerivingStrategies.
1116 -XDisambiguateRecordFields
1118 Enable record field disambiguation. Implied by RecordWildCards.
1119 -XDuplicateRecordFields
1121 Allow definition of record types with identically-named fields.
1122 -XEmptyCase
1124 Allow empty case alternatives.
1125 -XEmptyDataDecls
1127 Allow definition of empty data types.
1128 -XEmptyDataDeriving
1130 Allow deriving instances of standard type classes for empty data
1131 types.
1132 -XExistentialQuantification
1134 Enable liberalised type synonyms.
1135 -XExplicitForAll
1137 Enable explicit universal quantification. Implied by
1138 ScopedTypeVariables, LiberalTypeSynonyms, RankNTypes and
1139 ExistentialQuantification.
1140 -XExplicitNamespaces
1142 Enable using the keyword type to specify the namespace of en‐
1143 tries in imports and exports (Explicit namespaces in import/ex‐
1144 port). Implied by TypeOperators and TypeFamilies.
1145 -XExtendedDefaultRules
1147 Use GHCi's extended default rules in a normal module.
1148 -XFieldSelectors
1150 Control visibility of field selector functions.
1151 -XFlexibleContexts
1153 Remove some restrictions on class contexts
1154 -XFlexibleInstances
1156 Enable flexible instances. Implies TypeSynonymInstances.
1157 -XForeignFunctionInterface
1159 Enable foreign function interface.
1160 -XFunctionalDependencies
1162 Enable functional dependencies. Implies MultiParamTypeClasses.
1163 -XGADTs
1165 Enable generalised algebraic data types. Implies GADTSyntax and
1166 MonoLocalBinds.
1167 -XGADTSyntax
1169 Enable generalised algebraic data type syntax.
1170 -XGeneralisedNewtypeDeriving
1172 Enable newtype deriving.
1173 -XGeneralizedNewtypeDeriving
1175 Enable newtype deriving.
1176 -XGHC2021
1178 Use GHC’s set of default language extensions from 2021
1179 -XGHCForeignImportPrim
1181 Enable prim calling convention. Intended for internal use only.
1182 -XHaskell2010
1184 Use the Haskell 2010 language variant.
1185 -XHaskell98
1187 Use the Haskell 98 language variant.
1188 -XHexFloatLiterals
1190 Enable support for hexadecimal floating point literals.
1191 -XImplicitParams
1193 Enable Implicit Parameters.
1194 -XImportQualifiedPost
1196 ImportQualifiedPost allows the syntax import M qualified
1197 -XImpredicativeTypes
1199 Enable impredicative types. Implies RankNTypes.
1200 -XIncoherentInstances
1202 Enable incoherent instances. Implies OverlappingInstances.
1203 -XInstanceSigs
1205 Enable instance signatures.
1206 -XInterruptibleFFI
1208 Enable interruptible FFI.
1209 -XKindSignatures
1211 Enable kind signatures. Implied by TypeFamilies and PolyKinds.
1212 -XLambdaCase
1214 Enable lambda-case expressions.
1215 -XLexicalNegation
1217 Use whitespace to determine whether the minus sign stands for
1218 negation or subtraction.
1219 -XLiberalTypeSynonyms
1221 Enable liberalised type synonyms.
1222 -XLinearTypes
1224 Enable linear types.
1225 -XMagicHash
1227 Allow # as a postfix modifier on identifiers.
1228 -XMonadComprehensions
1230 Enable monad comprehensions.
1231 -XMonoLocalBinds
1233 Enable do not generalise local bindings. Implied by
1234 TypeFamilies and GADTs.
1235 -XMultiParamTypeClasses
1237 Enable multi parameter type classes. Implied by
1238 FunctionalDependencies.
1239 -XMultiWayIf
1241 Enable multi-way if-expressions.
1242 -XNamedFieldPuns
1244 Enable record puns.
1245 -XNamedWildCards
1247 Enable named wildcards.
1248 -XNegativeLiterals
1250 Enable support for negative literals.
1251 -XNoImplicitPrelude
1253 Don't implicitly import Prelude. Implied by RebindableSyntax.
1254 -XNoMonomorphismRestriction
1256 Disable the monomorphism restriction.
1257 -XNondecreasingIndentation
1259 Allow nested contexts to be at the same indentation level as its
1260 enclosing context.
1261 -XNoPatternGuards
1263 Disable pattern guards. Implied by Haskell98.
1264 -XNoTraditionalRecordSyntax
1266 Disable support for traditional record syntax (as supported by
1267 Haskell 98) C {f = x}
1268 -XNPlusKPatterns
1270 Enable support for n+k patterns. Implied by Haskell98.
1271 -XNullaryTypeClasses
1273 Deprecated, does nothing. nullary (no parameter) type classes
1274 are now enabled using MultiParamTypeClasses.
1275 -XNumDecimals
1277 Enable support for 'fractional' integer literals.
1278 -XNumericUnderscores
1280 Enable support for numeric underscores.
1281 -XOverlappingInstances
1283 Enable overlapping instances.
1284 -XOverloadedLabels
1286 Enable overloaded labels.
1287 -XOverloadedLists
1289 Enable overloaded lists.
1290 -XOverloadedRecordDot
1292 Record '.' syntax
1293 -XOverloadedRecordUpdate
1295 Record '.' syntax record updates
1296 -XOverloadedStrings
1298 Enable overloaded string literals.
1299 -XPackageImports
1301 Enable package-qualified imports.
1302 -XParallelListComp
1304 Enable parallel list comprehensions.
1305 -XPartialTypeSignatures
1307 Enable partial type signatures.
1308 -XPatternSynonyms
1310 Enable pattern synonyms.
1311 -XPolyKinds
1313 Enable kind polymorphism. Implies KindSignatures.
1314 -XPostfixOperators
1316 Enable postfix operators.
1317 -XQualifiedDo
1319 Enable qualified do-notation desugaring.
1320 -XQuantifiedConstraints
1322 Allow forall quantifiers in constraints.
1323 -XQuasiQuotes
1325 Enable quasiquotation.
1326 -XRank2Types
1328 Enable rank-2 types. Synonym for RankNTypes.
1329 -XRankNTypes
1331 Enable rank-N types. Implied by ImpredicativeTypes.
1332 -XRebindableSyntax
1334 Employ rebindable syntax. Implies NoImplicitPrelude.
1335 -XRecordWildCards
1337 Enable record wildcards. Implies DisambiguateRecordFields.
1338 -XRecursiveDo
1340 Enable recursive do (mdo) notation.
1341 -XRoleAnnotations
1343 Enable role annotations.
1344 -XSafe Enable the Safe Haskell Safe mode.
1346 -XScopedTypeVariables
1348 Enable lexically-scoped type variables.
1349 -XStandaloneDeriving
1351 Enable standalone deriving.
1352 -XStandaloneKindSignatures
1354 Allow the use of standalone kind signatures.
1355 -XStarIsType
1357 Treat * as Data.Kind.Type.
1358 -XStaticPointers
1360 Enable static pointers.
1361 -XStrict
1363 Make bindings in the current module strict by default.
1364 -XStrictData
1366 Enable default strict datatype fields.
1367 -XTemplateHaskell
1369 Enable Template Haskell.
1370 -XTemplateHaskellQuotes
1372 Enable quotation subset of Template Haskell.
1373 -XTransformListComp
1375 Enable generalised list comprehensions.
1376 -XTrustworthy
1378 Enable the Safe Haskell Trustworthy mode.
1379 -XTupleSections
1381 Enable tuple sections.
1382 -XTypeApplications
1384 Enable type application syntax in terms, patterns and types.
1385 -XTypeData
1387 Enable type data declarations.
1388 -XTypeFamilies
1390 Enable type families. Implies ExplicitNamespaces,
1391 KindSignatures, and MonoLocalBinds.
1392 -XTypeFamilyDependencies
1394 Enable injective type families. Implies TypeFamilies.
1395 -XTypeInType
1397 Deprecated. Enable kind polymorphism and datatype promotion.
1398 -XTypeOperators
1400 Enable type operators. Implies ExplicitNamespaces.
1401 -XTypeSynonymInstances
1403 Enable type synonyms in instance heads. Implied by
1404 FlexibleInstances.
1405 -XUnboxedSums
1407 Enable unboxed sums.
1408 -XUnboxedTuples
1410 Enable the use of unboxed tuple syntax.
1411 -XUndecidableInstances
1413 Enable undecidable instances.
1414 -XUndecidableSuperClasses
1416 Allow all superclass constraints, including those that may re‐
1417 sult in non-termination of the typechecker.
1418 -XUnicodeSyntax
1420 Enable unicode syntax.
1421 -XUnliftedDatatypes
1423 Enable unlifted data types.
1424 -XUnliftedFFITypes
1426 Enable unlifted FFI types
1427 -XUnliftedNewtypes
1429 Enable unlifted newtypes.
1430 -XUnsafe
1432 Enable Safe Haskell Unsafe mode.
1433 -XViewPatterns
1435 Enable view patterns.
1436 Linking options
1438 -c Stop after generating object (.o) file
1439 -debug Use the debugging runtime
1441 -dylib-install-name ⟨path⟩
1443 Set the install name (via -install_name passed to Apple's
1444 linker), specifying the full install path of the library file.
1445 Any libraries or executables that link with it later will pick
1446 up that path as their runtime search location for it. (Dar‐
1447 win/OS X only)
1448 -dynamic
1450 Build dynamically-linked object files and executables
1451 -dynload
1453 Selects one of a number of modes for finding shared libraries at
1454 runtime.
1455 -eventlog
1457 Enable runtime event tracing
1458 -fcompact-unwind
1460 Instruct the linker to produce a __compact_unwind section.
1461 -fkeep-cafs
1463 Do not garbage-collect CAFs (top-level expressions) at runtime
1464 -flink-rts
1466 Link the runtime when generating a shared or static library
1467 -fno-embed-manifest
1469 Do not embed the manifest in the executable (Windows only)
1470 -fno-gen-manifest
1472 Do not generate a manifest file (Windows only)
1473 -fno-shared-implib
1475 Don't generate an import library for a DLL (Windows only)
1476 -framework ⟨name⟩
1478 On Darwin/OS X/iOS only, link in the framework ⟨name⟩. This op‐
1479 tion corresponds to the -framework option for Apple's Linker.
1480 -framework-path ⟨dir⟩
1482 On Darwin/OS X/iOS only, add ⟨dir⟩ to the list of directories
1483 searched for frameworks. This option corresponds to the -F op‐
1484 tion for Apple's Linker.
1485 -fsplit-sections
1487 Split sections for link-time dead-code stripping
1488 -fuse-rpaths
1490 Set the rpath based on -L flags
1491 -fwhole-archive-hs-libs
1493 When linking a binary executable, this inserts the flag
1494 -Wl,--whole-archive before any -l flags for Haskell libraries,
1495 and -Wl,--no-whole-archive afterwards
1496 -L ⟨dir⟩
1498 Add ⟨dir⟩ to the list of directories searched for libraries
1499 -l ⟨lib⟩
1501 Link in library ⟨lib⟩
1502 -main-is ⟨thing⟩
1504 Set main module and function
1505 -no-hs-main
1507 Don't assume this program contains main
1508 -no-pie
1510 Don't instruct the linker to produce a position-independent exe‐
1511 cutable.
1512 -no-rtsopts-suggestions
1514 Don't print RTS suggestions about linking with
1515 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩].
1516 -package ⟨name⟩
1518 Expose package ⟨pkg⟩
1519 -pie Instruct the linker to produce a position-independent exe‐
1521 cutable.
1522 -rdynamic
1524 This instructs the linker to add all symbols, not only used
1525 ones, to the dynamic symbol table. Currently Linux and Win‐
1526 dows/MinGW32 only. This is equivalent to using -optl -rdynamic
1527 on Linux, and -optl -export-all-symbols on Windows.
1528 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩]
1530 Control whether the RTS behaviour can be tweaked via com‐
1531 mand-line flags and the GHCRTS environment variable. Using none
1532 means no RTS flags can be given; some means only a minimum of
1533 safe options can be given (the default); all (or no argument at
1534 all) means that all RTS flags are permitted; ignore means RTS
1535 flags can be given, but are treated as regular arguments and
1536 passed to the Haskell program as arguments; ignoreAll is the
1537 same as ignore, but GHCRTS is also ignored. -rtsopts does not
1538 affect -with-rtsopts behavior; flags passed via -with-rtsopts
1539 are used regardless of -rtsopts.
1540 -shared
1542 Generate a shared library (as opposed to an executable)
1543 -static
1545 Use static Haskell libraries
1546 -staticlib
1548 Generate a standalone static library (as opposed to an exe‐
1549 cutable). This is useful when cross compiling. The library to‐
1550 gether with all its dependencies ends up in in a single static
1551 library that can be linked against.
1552 -threaded
1554 Use the threaded runtime
1555 -with-rtsopts=⟨opts⟩
1557 Set the default RTS options to ⟨opts⟩.
1558 Miscellaneous options
1560 -ddump-mod-cycles
1561 Dump module cycles
1562 -fexternal-interpreter
1564 Run interpreted code in a separate process
1565 -ffamily-application-cache
1567 Use a cache when reducing type family applications
1568 -fglasgow-exts
1570 Deprecated. Enable most language extensions; see Controlling ex‐
1571 tensions for exactly which ones.
1572 -fno-safe-haskell
1574 Disable Safe Haskell
1575 -ghcversion-file ⟨path to ghcversion.h⟩
1577 (GHC as a C compiler only) Use this ghcversion.h file
1578 -H ⟨size⟩
1580 Set the minimum size of the heap to ⟨size⟩
1581 -hidden-module ⟨module name⟩
1583 A module which should not be visible outside its unit.
1584 -j[⟨n⟩]
1586 When compiling with --make, compile ⟨n⟩ modules in parallel.
1587 -reexported-module ⟨module name⟩
1589 A module which should be reexported from this unit.
1590 -this-package-name ⟨unit-id⟩
1592 The name of the package which this module would be part of when
1593 installed.
1594 -unit @⟨filename⟩
1596 Specify the options to build a specific unit.
1597 -working-dir ⟨dir⟩
1599 Specify the directory a unit is expected to be compiled in.
1600 Modes of operation
1602 --frontend ⟨module⟩
1603 run GHC with the given frontend plugin; see Frontend plugins for
1604 details.
1605 --help Display help
1607 --info display information about the compiler
1609 --interactive
1611 Interactive mode - normally used by just running ghci; see Using
1612 GHCi for details.
1613 --make Build a multi-module Haskell program, automatically figuring out
1615 dependencies. Likely to be much easier, and faster, than using
1616 make; see Using ghc --make for details.
1617 --numeric-version
1619 display GHC version (numeric only)
1620 --print-booter-version
1622 display bootstrap compiler version
1623 --print-build-platform
1625 display platform on which GHC was built
1626 --print-c-compiler-flags
1628 C compiler flags used to build GHC
1629 --print-c-compiler-link-flags
1631 C linker flags used to build GHC
1632 --print-debug-on
1634 print whether GHC was built with -DDEBUG
1635 --print-global-package-db
1637 display GHC's global package database directory
1638 --print-have-interpreter
1640 display whether GHC was built with interactive support
1641 --print-have-native-code-generator
1643 display whether target platform has NCG support
1644 --print-host-platform
1646 display host platform of GHC
1647 --print-ld-flags
1649 display linker flags used to compile GHC
1650 --print-leading-underscore
1652 display use of leading underscores on symbol names
1653 --print-libdir
1655 display GHC library directory
1656 --print-object-splitting-supported
1658 display whether GHC supports object splitting
1659 --print-project-git-commit-id
1661 display Git commit id GHC is built from
1662 --print-project-version
1664 display GHC version
1665 --print-rts-ways
1667 display which way RTS was built
1668 --print-stage
1670 display stage number of GHC
1671 --print-support-smp
1673 display whether GHC was compiled with SMP support
1674 --print-tables-next-to-code
1676 display whether GHC was compiled with --enable-ta‐
1677 bles-next-to-code
1678 --print-target-platform
1680 display target platform of GHC
1681 --print-unregisterised
1683 display whether this GHC was built in unregisterised mode
1684 --run ⟨file⟩
1686 Run a Haskell program.
1687 --show-iface ⟨file⟩
1689 display the contents of an interface file.
1690 --show-options
1692 display the supported command line options
1693 --supported-extensions
1695 display the supported language extensions
1696 --version
1698 display GHC version
1699 -e ⟨expr⟩
1701 Evaluate expr; see Expression evaluation mode for details.
1702 -M generate dependency information suitable for use in a Makefile;
1704 see Dependency generation for details.
1705 -shared
1707 Create a shared object.
1708 Individual optimizations
1710 -fasm-shortcutting
1711 Enable shortcutting on assembly. Implied by -O2.
1712 -fbinary-blob-threshold=⟨n⟩
1714 default: 500K. Tweak assembly generator for binary blobs.
1715 -fblock-layout-cfg
1717 Use the new cfg based block layout algorithm.
1718 -fblock-layout-weightless
1720 Ignore cfg weights for code layout.
1721 -fblock-layout-weights
1723 Sets edge weights used by the new code layout algorithm.
1724 -fcall-arity
1726 Enable call-arity optimisation. Implied by -O.
1727 -fcase-folding
1729 Enable constant folding in case expressions. Implied by -O.
1730 -fcase-merge
1732 Enable case-merging. Implied by -O.
1733 -fcmm-control-flow
1735 Enable control flow optimisation in the Cmm backend. Implied by
1736 -O.
1737 -fcmm-elim-common-blocks
1739 Enable Cmm common block elimination. Implied by -O.
1740 -fcmm-sink
1742 Enable Cmm sinking. Implied by -O.
1743 -fcmm-static-pred
1745 Enable static control flow prediction. Implied by -O.
1746 -fcore-constant-folding
1748 Enable constant folding in Core. Implied by -O.
1749 -fcpr-anal
1751 Turn on Constructed Product Result analysis. Implied by -O.
1752 -fcross-module-specialise
1754 Turn on specialisation of overloaded functions imported from
1755 other modules.
1756 -fcse Enable common sub-expression elimination. Implied by -O.
1758 -fdicts-cheap
1760 Make dictionary-valued expressions seem cheap to the optimiser.
1761 -fdicts-strict
1763 Make dictionaries strict. Implied by -O2.
1764 -fdmd-tx-dict-sel
1766 (deprecated) Use a special demand transformer for dictionary se‐
1767 lectors.
1768 -fdmd-unbox-width=⟨n⟩
1770 default: 3. Boxity analysis pretends that returned records with
1771 this many fields can be unboxed.
1772 -fdo-eta-reduction
1774 Enable eta-reduction. Implied by -O.
1775 -fdo-lambda-eta-expansion
1777 Enable lambda eta-expansion. Always enabled by default.
1778 -feager-blackholing
1780 Turn on eager blackholing
1781 -fenable-rewrite-rules
1783 Switch on all rewrite rules (including rules generated by auto‐
1784 matic specialisation of overloaded functions). Implied by -O.
1785 -fexcess-precision
1787 Enable excess intermediate precision
1788 -fexitification
1790 Enables exitification optimisation. Implied by -O.
1791 -fexpose-all-unfoldings
1793 Expose all unfoldings, even for very large or recursive func‐
1794 tions.
1795 -ffloat-in
1797 Turn on the float-in transformation. Implied by -O.
1798 -ffull-laziness
1800 Turn on full laziness (floating bindings outwards). Implied by
1801 -O.
1802 -ffun-to-thunk
1804 (deprecated) superseded by -ffull-laziness.
1805 -fignore-asserts
1807 Ignore assertions in the source. Implied by -O.
1808 -fignore-interface-pragmas
1810 Ignore pragmas in interface files. Implied by -O0 only.
1811 -finline-generics
1813 Annotate methods of derived Generic and Generic1 instances with
1814 INLINE[1] pragmas based on heuristics. Implied by -O.
1815 -finline-generics-aggressively
1817 Annotate methods of all derived Generic and Generic1 instances
1818 with INLINE[1] pragmas.
1819 -flate-dmd-anal
1821 Run demand analysis again, at the end of the simplification
1822 pipeline
1823 -flate-specialise
1825 Run a late specialisation pass
1826 -fliberate-case
1828 Turn on the liberate-case transformation. Implied by -O2.
1829 -fliberate-case-threshold=⟨n⟩
1831 default: 2000. Set the size threshold for the liberate-case
1832 transformation to ⟨n⟩
1833 -fllvm-pass-vectors-in-regs
1835 (deprecated) Does nothing
1836 -flocal-float-out
1838 Enable local floating definitions out of let-binds.
1839 -flocal-float-out-top-level
1841 Enable local floating to float top-level bindings
1842 -floopification
1844 Turn saturated self-recursive tail-calls into local jumps in the
1845 generated assembly. Implied by -O.
1846 -fmax-inline-alloc-size=⟨n⟩
1848 default: 128. Set the maximum size of inline array allocations
1849 to ⟨n⟩ bytes (default: 128).
1850 -fmax-inline-memcpy-insns=⟨n⟩
1852 default: 32. Inline memcpy calls if they would generate no more
1853 than ⟨n⟩ pseudo instructions.
1854 -fmax-inline-memset-insns=⟨n⟩
1856 default: 32. Inline memset calls if they would generate no more
1857 than ⟨n⟩ pseudo instructions
1858 -fmax-simplifier-iterations=⟨n⟩
1860 default: 4. Set the max iterations for the simplifier.
1861 -fmax-uncovered-patterns=⟨n⟩
1863 default: 4. Set the maximum number of patterns to display in
1864 warnings about non-exhaustive ones.
1865 -fmax-worker-args=⟨n⟩
1867 default: 10. Maximum number of value arguments for a worker.
1868 -fno-opt-coercion
1870 Turn off the coercion optimiser
1871 -fno-pre-inlining
1873 Turn off pre-inlining
1874 -fno-state-hack
1876 Turn off the state hackwhereby any lambda with a real-world
1877 state token as argument is considered to be single-entry. Hence
1878 OK to inline things inside it.
1879 -fomit-interface-pragmas
1881 Don't generate interface pragmas. Implied by -O0 only.
1882 -fomit-yields
1884 Omit heap checks when no allocation is being performed.
1885 -foptimal-applicative-do
1887 Use a slower but better algorithm for ApplicativeDo
1888 -fpedantic-bottoms
1890 Make GHC be more precise about its treatment of bottom (but see
1891 also -fno-state-hack). In particular, GHC will not eta-expand
1892 through a case expression.
1893 -fpolymorphic-specialisation
1895 Allow specialisation to abstract over free type variables
1896 -fregs-graph
1898 Use the graph colouring register allocator for register alloca‐
1899 tion in the native code generator.
1900 -fregs-iterative
1902 Use the iterative coalescing graph colouring register allocator
1903 in the native code generator.
1904 -fsimpl-tick-factor=⟨n⟩
1906 default: 100. Set the percentage factor for simplifier ticks.
1907 -fsimplifier-phases=⟨n⟩
1909 default: 2. Set the number of phases for the simplifier. Ig‐
1910 nored with -O0.
1911 -fsolve-constant-dicts
1913 When solving constraints, try to eagerly solve super classes us‐
1914 ing available dictionaries.
1915 -fspec-constr
1917 Turn on the SpecConstr transformation. Implied by -O2.
1918 -fspec-constr-count=⟨n⟩
1920 default: 3.* Set to ⟨n⟩ the maximum number of specialisations
1921 that will be created for any one function by the SpecConstr
1922 transformation.
1923 -fspec-constr-keen
1925 Specialize a call with an explicit constructor argument, even if
1926 the argument is not scrutinised in the body of the function
1927 -fspec-constr-threshold=⟨n⟩
1929 default: 2000. Set the size threshold for the SpecConstr trans‐
1930 formation to ⟨n⟩.
1931 -fspecialise
1933 Turn on specialisation of overloaded functions. Implied by -O.
1934 -fspecialise-aggressively
1936 Turn on specialisation of overloaded functions regardless of
1937 size, if unfolding is available
1938 -fstatic-argument-transformation
1940 Turn on the static argument transformation.
1941 -fstg-cse
1943 Enable common sub-expression elimination on the STG intermediate
1944 language
1945 -fstg-lift-lams
1947 Enable late lambda lifting on the STG intermediate language. Im‐
1948 plied by -O2.
1949 -fstg-lift-lams-known
1951 Allow turning known into unknown calls while performing late
1952 lambda lifting.
1953 -fstg-lift-lams-non-rec-args
1955 Create top-level non-recursive functions with at most <n> param‐
1956 eters while performing late lambda lifting.
1957 -fstg-lift-lams-rec-args
1959 Create top-level recursive functions with at most <n> parameters
1960 while performing late lambda lifting.
1961 -fstrictness
1963 Turn on demand analysis. Implied by -O. Implies
1964 -fworker-wrapper
1965 -fstrictness-before=⟨n⟩
1967 Run an additional demand analysis before simplifier phase ⟨n⟩
1968 -funbox-small-strict-fields
1970 Flatten strict constructor fields with a pointer-sized represen‐
1971 tation. Implied by -O.
1972 -funbox-strict-fields
1974 Flatten strict constructor fields
1975 -funfolding-case-scaling=⟨n⟩
1977 default: 30. Apply a penalty of (inlining_cost * 1/n) for each
1978 level of case nesting.
1979 -funfolding-case-threshold=⟨n⟩
1981 default: 2. Reduce inlining for cases nested deeper than n.
1982 -funfolding-creation-threshold=⟨n⟩
1984 default: 750. Tweak unfolding settings.
1985 -funfolding-dict-discount=⟨n⟩
1987 default: 30. Tweak unfolding settings.
1988 -funfolding-fun-discount=⟨n⟩
1990 default: 60. Tweak unfolding settings.
1991 -funfolding-keeness-factor=⟨n⟩
1993 This has been deprecated in GHC 9.0.1.
1994 -funfolding-use-threshold=⟨n⟩
1996 default: 80. Tweak unfolding settings.
1997 -fworker-wrapper
1999 Enable the worker/wrapper transformation.
2000 -fworker-wrapper-cbv
2002 Enable w/w splits for wrappers whos sole purpose is evaluating
2003 arguments.
2004 Optimization levels
2006 -O Enable level 1 optimisations
2007 -O0 Disable optimisations (default)
2009 -O2 Enable level 2 optimisations
2011 -O⟨n⟩ Any -On where n > 2 is the same as -O2.
2013 Package options
2015 -clear-package-db
2016 Clear the package db stack.
2017 -distrust ⟨pkg⟩
2019 Expose package ⟨pkg⟩ and set it to be distrusted. See Safe
2020 Haskell.
2021 -distrust-all-packages
2023 Distrust all packages by default. See Safe Haskell.
2024 -fpackage-trust
2026 Enable Safe Haskell trusted package requirement for trustworthy
2027 modules.
2028 -global-package-db
2030 Add the global package db to the stack.
2031 -hide-all-packages
2033 Hide all packages by default
2034 -hide-package ⟨pkg⟩
2036 Hide package ⟨pkg⟩
2037 -ignore-package ⟨pkg⟩
2039 Ignore package ⟨pkg⟩
2040 -no-auto-link-packages
2042 Don't automatically link in the base and rts packages.
2043 -no-global-package-db
2045 Remove the global package db from the stack.
2046 -no-user-package-db
2048 Remove the user's package db from the stack.
2049 -package ⟨pkg⟩
2051 Expose package ⟨pkg⟩
2052 -package-db ⟨file⟩
2054 Add ⟨file⟩ to the package db stack.
2055 -package-env ⟨file⟩|⟨name⟩
2057 Use the specified package environment.
2058 -package-id ⟨unit-id⟩
2060 Expose package by id ⟨unit-id⟩
2061 -this-unit-id ⟨unit-id⟩
2063 Compile to be part of unit (i.e. package) ⟨unit-id⟩
2064 -trust ⟨pkg⟩
2066 Expose package ⟨pkg⟩ and set it to be trusted. See Safe Haskell.
2067 -user-package-db
2069 Add the user's package db to the stack.
2070 Phases of compilation
2072 --merge-objs
2073 Merge a set of objects into a GHCi library.
2074 -C Stop after generating C (.hc file)
2076 -c Stop after generating object (.o) file
2078 -E Stop after preprocessing (.hspp file)
2080 -F Enable the use of a pre-processor (set with -pgmF ⟨cmd⟩)
2082 -S Stop after generating assembly (.s file)
2084 -x ⟨suffix⟩
2086 Override default behaviour for source files
2087 Overriding external programs
2089 -pgma ⟨cmd⟩
2090 Use ⟨cmd⟩ as the assembler
2091 -pgmc ⟨cmd⟩
2093 Use ⟨cmd⟩ as the C compiler
2094 -pgmcxx ⟨cmd⟩
2096 Use ⟨cmd⟩ as the C++ compiler
2097 -pgmdll ⟨cmd⟩
2099 Use ⟨cmd⟩ as the DLL generator
2100 -pgmF ⟨cmd⟩
2102 Use ⟨cmd⟩ as the pre-processor (with -F only)
2103 -pgmi ⟨cmd⟩
2105 Use ⟨cmd⟩ as the external interpreter command.
2106 -pgminstall_name_tool ⟨cmd⟩
2108 Use ⟨cmd⟩ as the program to inject runpath into mach-o dylibs on
2109 macOS
2110 -pgmL ⟨cmd⟩
2112 Use ⟨cmd⟩ as the literate pre-processor
2113 -pgml ⟨cmd⟩
2115 Use ⟨cmd⟩ as the linker
2116 -pgmlc ⟨cmd⟩
2118 Use ⟨cmd⟩ as the LLVM compiler
2119 -pgmlm ⟨cmd⟩
2121 Use ⟨cmd⟩ as the linker when merging object files
2122 -pgmlo ⟨cmd⟩
2124 Use ⟨cmd⟩ as the LLVM optimiser
2125 -pgmotool ⟨cmd⟩
2127 Use ⟨cmd⟩ as the program to inspect mach-o dylibs on macOS
2128 -pgmP ⟨cmd⟩
2130 Use ⟨cmd⟩ as the C pre-processor (with -cpp only)
2131 -pgms ⟨cmd⟩
2133 Use ⟨cmd⟩ as the splitter
2134 -pgmwindres ⟨cmd⟩
2136 Use ⟨cmd⟩ as the program for embedding manifests on Windows.
2137 Phase-specific options
2139 -opta ⟨option⟩
2140 pass ⟨option⟩ to the assembler
2141 -optc ⟨option⟩
2143 pass ⟨option⟩ to the C compiler
2144 -optcxx ⟨option⟩
2146 pass ⟨option⟩ to the C++ compiler
2147 -optdll ⟨option⟩
2149 pass ⟨option⟩ to the DLL generator
2150 -optF ⟨option⟩
2152 pass ⟨option⟩ to the custom pre-processor
2153 -opti ⟨option⟩
2155 pass ⟨option⟩ to the interpreter sub-process.
2156 -optL ⟨option⟩
2158 pass ⟨option⟩ to the literate pre-processor
2159 -optl ⟨option⟩
2161 pass ⟨option⟩ to the linker
2162 -optlc ⟨option⟩
2164 pass ⟨option⟩ to the LLVM compiler
2165 -optlm ⟨option⟩
2167 pass ⟨option⟩ to the linker when merging object files.
2168 -optlo ⟨option⟩
2170 pass ⟨option⟩ to the LLVM optimiser
2171 -optP ⟨option⟩
2173 pass ⟨option⟩ to cpp (with -cpp only)
2174 -optwindres ⟨option⟩
2176 pass ⟨option⟩ to windres.
2177 -pgmc-supports-no-pie
2179 (deprecated) Indicate that the linker supports -no-pie
2180 -pgml-supports-no-pie
2182 Indicate that the linker supports -no-pie
2183 Platform-specific options
2185 -mavx (x86 only) Enable support for AVX SIMD extensions
2186 -mavx2 (x86 only) Enable support for AVX2 SIMD extensions
2188 -mavx512cd
2190 (x86 only) Enable support for AVX512-CD SIMD extensions
2191 -mavx512er
2193 (x86 only) Enable support for AVX512-ER SIMD extensions
2194 -mavx512f
2196 (x86 only) Enable support for AVX512-F SIMD extensions
2197 -mavx512pf
2199 (x86 only) Enable support for AVX512-PF SIMD extensions
2200 -mbmi (x86 only) Use BMI1 for bit manipulation operations
2202 -mbmi2 (x86 only) Use BMI2 for bit manipulation operations
2204 -msse (x86 only) Use SSE for floating-point operations
2206 -msse2 (x86 only) Use SSE2 for floating-point operations
2208 -msse3 (x86 only) Use SSE3 for floating-point operations
2210 -msse4 (x86 only) Use SSE4 for floating-point operations
2212 -msse4.2
2214 (x86 only) Use SSE4.2 for floating-point operations
2215 Compiler plugins
2217 -fclear-plugins
2218 Clear the list of active plugins
2219 -fplugin-library=⟨file-path⟩;⟨unit-id⟩;⟨module⟩;⟨args⟩
2221 Load a pre-compiled static plugin from an external library
2222 -fplugin-opt=⟨module⟩:⟨args⟩
2224 Give arguments to a plugin module; module must be specified with
2225 -fplugin=⟨module⟩
2226 -fplugin-trustworthy
2228 Trust the used plugins and no longer mark the compiled module as
2229 unsafe
2230 -fplugin=⟨module⟩
2232 Load a plugin exported by a given module
2233 -hide-all-plugin-packages
2235 Hide all packages for plugins by default
2236 -plugin-package ⟨pkg⟩
2238 Expose ⟨pkg⟩ for plugins
2239 -plugin-package-id ⟨pkg-id⟩
2241 Expose ⟨pkg-id⟩ for plugins
2242 Profiling
2244 -auto (deprecated) Alias for -fprof-auto-exported
2245 -auto-all
2247 (deprecated) Alias for -fprof-auto
2248 -caf-all
2250 (deprecated) Alias for -fprof-cafs
2251 -fno-prof-count-entries
2253 Do not collect entry counts
2254 -fprof-auto
2256 Auto-add SCC\ s to all bindings not marked INLINE
2257 -fprof-auto-calls
2259 Auto-add SCC\ s to all call sites
2260 -fprof-auto-exported
2262 Auto-add SCC\ s to all exported bindings not marked INLINE
2263 -fprof-auto-top
2265 Auto-add SCC\ s to all top-level bindings not marked INLINE
2266 -fprof-cafs
2268 Auto-add SCC\ s to all CAFs
2269 -fprof-callers=⟨name⟩
2271 Auto-add SCC\ s to all call-sites of the named function.
2272 -fprof-late
2274 Auto-add SCC\ s to all top level bindings after the core pipe‐
2275 line has run.
2276 -fprof-late-inline
2278 Auto-add SCC\ s to all top level bindings after the optimizer
2279 has run and retain them when inlining.
2280 -fprof-manual
2282 Process manual SCC annotations.
2283 -no-auto
2285 (deprecated) Alias for -fno-prof-auto
2286 -no-auto-all
2288 (deprecated) Alias for -fno-prof-auto
2289 -no-caf-all
2291 (deprecated) Alias for -fno-prof-cafs
2292 -prof Turn on profiling
2294 -ticky Turn on ticky-ticky profiling
2296 -ticky-allocd
2298 Track the number of times each closure type is allocated.
2299 -ticky-ap-thunk
2301 Don't use standard AP thunks on order to get more reliable entry
2302 counters.
2303 -ticky-dyn-thunk
2305 Track allocations of dynamic thunks
2306 -ticky-LNE
2308 Treat join point binders similar to thunks/functions.
2309 -ticky-tag-checks
2311 Emit dummy ticky counters to record how many tag-inference
2312 checks tag inference avoided.
2313 Program coverage
2315 -fhpc Turn on Haskell program coverage instrumentation
2316 -hpcdir⟨dir⟩
2318 Set the directory where GHC places .mix files.
2319 Recompilation checking
2321 -exclude-module=⟨file⟩
2322 Regard ⟨file⟩ as "stable"; i.e., exclude it from having depen‐
2323 dencies on it.
2324 -fforce-recomp
2326 Turn off recompilation checking. This is implied by any -ddump-X
2327 option when compiling a single file (i.e. when using -c).
2328 -fignore-hpc-changes
2330 Do not recompile modules just to match changes to HPC flags.
2331 This is especially useful for avoiding recompilation when using
2332 GHCi, and is enabled by default for GHCi.
2333 -fignore-optim-changes
2335 Do not recompile modules just to match changes to optimisation
2336 flags. This is especially useful for avoiding recompilation when
2337 using GHCi, and is enabled by default for GHCi.
2338 -include-cpp-deps
2340 Include preprocessor dependencies
2341 -include-pkg-deps
2343 Regard modules imported from packages as unstable
2344 Redirecting output
2346 -dep-makefile ⟨file⟩
2347 Use ⟨file⟩ as the makefile
2348 -dep-suffix ⟨suffix⟩
2350 Make dependencies that declare that files with suffix
2351 .⟨suf⟩⟨osuf⟩ depend on interface files with suffix .⟨suf⟩hi
2352 -dumpdir ⟨dir⟩
2354 redirect dump files
2355 -dynhisuf ⟨suffix⟩
2357 set the suffix to use for dynamic interface files
2358 -dyno ⟨file⟩
2360 set dynamic output filename
2361 -dynohi ⟨file⟩
2363 set the filename in which to put the dynamic interface
2364 -dynosuf ⟨suffix⟩
2366 set the dynamic output file suffix
2367 -hcsuf ⟨suffix⟩
2369 set the suffix to use for intermediate C files
2370 -hidir ⟨dir⟩
2372 set directory for interface files
2373 -hiedir ⟨dir⟩
2375 set directory for extended interface files
2376 -hiesuf ⟨suffix⟩
2378 set the suffix to use for extended interface files
2379 -hisuf ⟨suffix⟩
2381 set the suffix to use for interface files
2382 -o ⟨file⟩
2384 set output filename
2385 -odir ⟨dir⟩
2387 set directory for object files
2388 -ohi ⟨file⟩
2390 set the filename in which to put the interface
2391 -osuf ⟨suffix⟩
2393 set the output file suffix
2394 -outputdir ⟨dir⟩
2396 set output directory
2397 -stubdir ⟨dir⟩
2399 redirect FFI stub files
2400 Temporary files
2402 -tmpdir ⟨dir⟩
2403 set the directory for temporary files
2404 Verbosity options
2406 -fabstract-refinement-hole-fits
2407 default: off. Toggles whether refinements where one or more of
2408 the holes are abstract are reported.
2409 -fdefer-diagnostics
2411 Defer and group diagnostic messages by severity
2412 -fdiagnostics-color=⟨always|auto|never⟩
2414 Use colors in error messages
2415 -fdiagnostics-show-caret
2417 Whether to show snippets of original source code
2418 -ferror-spans
2420 Output full span in error messages
2421 -fhide-source-paths
2423 hide module source and object paths
2424 -fkeep-going
2426 Continue compilation as far as possible on errors
2427 -fmax-refinement-hole-fits=⟨n⟩
2429 default: 6. Set the maximum number of refinement hole fits for
2430 typed holes to display in type error messages.
2431 -fmax-relevant-binds=⟨n⟩
2433 default: 6. Set the maximum number of bindings to display in
2434 type error messages.
2435 -fmax-valid-hole-fits=⟨n⟩
2437 default: 6. Set the maximum number of valid hole fits for typed
2438 holes to display in type error messages.
2439 -fno-show-valid-hole-fits
2441 Disables showing a list of valid hole fits for typed holes in
2442 type error messages.
2443 -fno-sort-valid-hole-fits
2445 Disables the sorting of the list of valid hole fits for typed
2446 holes in type error messages.
2447 -fprint-axiom-incomps
2449 Display equation incompatibilities in closed type families
2450 -fprint-equality-relations
2452 Distinguish between equality relations when printing
2453 -fprint-expanded-synonyms
2455 In type errors, also print type-synonym-expanded types.
2456 -fprint-explicit-coercions
2458 Print coercions in types
2459 -fprint-explicit-foralls
2461 Print explicit forall quantification in types. See also
2462 ExplicitForAll
2463 -fprint-explicit-kinds
2465 Print explicit kind foralls and kind arguments in types. See
2466 also KindSignatures
2467 -fprint-explicit-runtime-reps
2469 Print RuntimeRep and Levity variables in types which are run‐
2470 time-representation polymorphic.
2471 -fprint-potential-instances
2473 display all available instances in type error messages
2474 -fprint-redundant-promotion-ticks
2476 Print redundant DataKinds promotion ticks
2477 -fprint-typechecker-elaboration
2479 Print extra information from typechecker.
2480 -fprint-unicode-syntax
2482 Use unicode syntax when printing expressions, types and kinds.
2483 See also UnicodeSyntax
2484 -frefinement-level-hole-fits=⟨n⟩
2486 default: off. Sets the level of refinement of the refinement
2487 hole fits, where level n means that hole fits of up to n holes
2488 will be considered.
2489 -freverse-errors
2491 Output errors in reverse order
2492 -fshow-docs-of-hole-fits
2494 Toggles whether to show the documentation of the valid hole fits
2495 in the output.
2496 -fshow-error-context
2498 Whether to show textual information about error context
2499 -fshow-hole-constraints
2501 Show constraints when reporting typed holes.
2502 -fshow-hole-matches-of-hole-fits
2504 Toggles whether to show the type of the additional holes in re‐
2505 finement hole fits.
2506 -fshow-provenance-of-hole-fits
2508 Toggles whether to show the provenance of the valid hole fits in
2509 the output.
2510 -fshow-type-app-of-hole-fits
2512 Toggles whether to show the type application of the valid hole
2513 fits in the output.
2514 -fshow-type-app-vars-of-hole-fits
2516 Toggles whether to show what type each quantified variable takes
2517 in a valid hole fit.
2518 -fshow-type-of-hole-fits
2520 Toggles whether to show the type of the valid hole fits in the
2521 output.
2522 -fsort-by-size-hole-fits
2524 Sort valid hole fits by size.
2525 -fsort-by-subsumption-hole-fits
2527 Sort valid hole fits by subsumption.
2528 -funclutter-valid-hole-fits
2530 Unclutter the list of valid hole fits by not showing provenance
2531 nor type applications of suggestions.
2532 -Rghc-timing
2534 Summarise timing stats for GHC (same as +RTS -tstderr).
2535 -v verbose mode (equivalent to -v3)
2537 -v⟨n⟩ set verbosity level
2539 Warnings
2541 -fdefer-out-of-scope-variables
2542 Convert variable out of scope variables errors into warnings.
2543 Implied by -fdefer-type-errors. See also
2544 -Wdeferred-out-of-scope-variables.
2545 -fdefer-type-errors
2547 Turn type errors into warnings, deferring the error until run‐
2548 time. Implies -fdefer-typed-holes and
2549 -fdefer-out-of-scope-variables. See also -Wdeferred-type-errors
2550 -fdefer-typed-holes
2552 Convert typed hole errors into warnings, deferring the error un‐
2553 til runtime. Implied by -fdefer-type-errors. See also
2554 -Wtyped-holes.
2555 -fenable-th-splice-warnings
2557 Generate warnings for Template Haskell splices
2558 -fhelpful-errors
2560 Make suggestions for mis-spelled names.
2561 -fmax-pmcheck-models=⟨n⟩
2563 soft limit on the number of parallel models the pattern match
2564 checker should check a pattern match clause against
2565 -fshow-warning-groups
2567 show which group an emitted warning belongs to.
2568 -fvia-C
2570 use the C code generator
2571 -W enable normal warnings
2573 -w disable all warnings
2575 -Wall enable almost all warnings (details in Warnings and san‐
2577 ity-checking)
2578 -Wall-missed-specialisations
2580 warn when specialisation of any overloaded function fails.
2581 -Wall-missed-specializations
2583 alias for -Wall-missed-specialisations
2584 -Wambiguous-fields
2586 warn about ambiguous field selectors or updates
2587 -Wauto-orphans
2589 (deprecated) Does nothing
2590 -Wcompat
2592 enable future compatibility warnings (details in Warnings and
2593 sanity-checking)
2594 -Wcompat-unqualified-imports
2596 Report unqualified imports of core libraries which are expected
2597 to cause compatibility problems in future releases.
2598 -Wcpp-undef
2600 warn on uses of the #if directive on undefined identifiers
2601 -Wdefault
2603 enable default flags
2604 -Wdeferred-out-of-scope-variables
2606 Report warnings when variable out-of-scope errors are deferred
2607 until runtime. See -fdefer-out-of-scope-variables.
2608 -Wdeferred-type-errors
2610 Report warnings when deferred type errors are enabled. This op‐
2611 tion is enabled by default. See -fdefer-type-errors.
2612 -Wdeprecated-flags
2614 warn about uses of commandline flags that are deprecated
2615 -Wdeprecations
2617 warn about uses of functions & types that have warnings or dep‐
2618 recated pragmas. Alias for -Wwarnings-deprecations
2619 -Wderiving-defaults
2621 warn about default deriving when using both DeriveAnyClass and
2622 GeneralizedNewtypeDeriving
2623 -Wderiving-typeable
2625 warn when Typeable is derived
2626 -Wdodgy-exports
2628 warn about dodgy exports
2629 -Wdodgy-foreign-imports
2631 warn about dodgy foreign imports
2632 -Wdodgy-imports
2634 warn about dodgy imports
2635 -Wduplicate-constraints
2637 warn when a constraint appears duplicated in a type signature
2638 -Wduplicate-exports
2640 warn when an entity is exported multiple times
2641 -Wempty-enumerations
2643 warn about enumerations that are empty
2644 -Werror
2646 make warnings fatal
2647 -Weverything
2649 enable all warnings supported by GHC
2650 -Wextra
2652 alias for -W
2653 -Wforall-identifier
2655 warn when forall is used as an identifier (at definition sites)
2656 -Wgadt-mono-local-binds
2658 warn when pattern matching on a GADT without MonoLocalBinds
2659 -Whi-shadowing
2661 (deprecated) warn when a .hi file in the current directory shad‐
2662 ows a library
2663 -Widentities
2665 warn about uses of Prelude numeric conversions that are probably
2666 the identity (and hence could be omitted)
2667 -Wimplicit-kind-vars
2669 (deprecated) warn when kind variables are implicitly quantified
2670 over.
2671 -Wimplicit-lift
2673 warn about implicit lift in Template Haskell quotes
2674 -Wimplicit-prelude
2676 warn when the Prelude is implicitly imported
2677 -Winaccessible-code
2679 warn about inaccessible code
2680 -Wincomplete-patterns
2682 warn when a pattern match could fail
2683 -Wincomplete-record-updates
2685 warn when a record update could fail
2686 -Wincomplete-uni-patterns
2688 warn when a pattern match in a lambda expression, pattern bind‐
2689 ing or a lazy pattern could fail
2690 -Winferred-safe-imports
2692 warn when an explicitly Safe Haskell module imports a Safe-In‐
2693 ferred one
2694 -Winline-rule-shadowing
2696 Warn if a rewrite RULE might fail to fire because the function
2697 might be inlined before the rule has a chance to fire. See How
2698 rules interact with INLINE/NOINLINE pragmas.
2699 -Winvalid-haddock
2701 warn when a Haddock comment occurs in an invalid position
2702 -Wloopy-superclass-solve
2704 warn when creating potentially-loopy superclass constraint evi‐
2705 dence
2706 -Wmisplaced-pragmas
2708 warn about uses of file header pragmas in the module body
2709 -Wmissed-extra-shared-lib
2711 Warn when GHCi can't load a shared lib.
2712 -Wmissed-specialisations
2714 warn when specialisation of an imported, overloaded function
2715 fails.
2716 -Wmissed-specializations
2718 alias for -Wmissed-specialisations
2719 -Wmissing-deriving-strategies
2721 warn when a deriving clause is missing a deriving strategy
2722 -Wmissing-export-lists
2724 warn when a module declaration does not explicitly list all ex‐
2725 ports
2726 -Wmissing-exported-pattern-synonym-signatures
2728 warn about pattern synonyms without signatures, only if they are
2729 exported
2730 -Wmissing-exported-signatures
2732 warn about top-level functions without signatures, only if they
2733 are exported
2734 -Wmissing-exported-sigs
2736 (deprecated) warn about top-level functions without signatures,
2737 only if they are exported. takes precedence over -Wmissing-sig‐
2738 natures
2739 -Wmissing-fields
2741 warn when fields of a record are uninitialised
2742 -Wmissing-home-modules
2744 warn when encountering a home module imported, but not listed on
2745 the command line. Useful for cabal to ensure GHC won't pick up
2746 modules, not listed neither in exposed-modules, nor in
2747 other-modules.
2748 -Wmissing-import-lists
2750 warn when an import declaration does not explicitly list all the
2751 names brought into scope
2752 -Wmissing-kind-signatures
2754 warn when type declarations don't have kind signatures nor CUSKs
2755 -Wmissing-local-signatures
2757 warn about polymorphic local bindings without signatures
2758 -Wmissing-local-sigs
2760 (deprecated) warn about polymorphic local bindings without sig‐
2761 natures
2762 -Wmissing-methods
2764 warn when class methods are undefined
2765 -Wmissing-monadfail-instances
2767 (deprecated) Warn when a failable pattern is used in a do-block
2768 that does not have a MonadFail instance.
2769 -Wmissing-pattern-synonym-signatures
2771 warn when pattern synonyms do not have type signatures
2772 -Wmissing-safe-haskell-mode
2774 warn when the Safe Haskell mode is not explicitly specified.
2775 -Wmissing-signatures
2777 warn about top-level functions without signatures
2778 -Wmissing-space-after-bang
2780 (deprecated) Does nothing
2781 -Wmonomorphism-restriction
2783 warn when the Monomorphism Restriction is applied
2784 -Wname-shadowing
2786 warn when names are shadowed
2787 -Wno-compat
2789 Disables all warnings enabled by -Wcompat.
2790 -Wnoncanonical-monad-instances
2792 warn when Applicative or Monad instances have noncanonical defi‐
2793 nitions of return, pure, (>>), or (*>). See flag description in
2794 Warnings and sanity-checking for more details.
2795 -Wnoncanonical-monadfail-instances
2797 (deprecated) warn when Monad or MonadFail instances have non‐
2798 canonical definitions of fail.
2799 -Wnoncanonical-monoid-instances
2801 warn when Semigroup or Monoid instances have noncanonical defi‐
2802 nitions of (<>) or mappend. See flag description in Warnings
2803 and sanity-checking for more details.
2804 -Wnot (deprecated) Alias for -w
2806 -Woperator-whitespace
2808 warn on prefix, suffix, and tight infix uses of infix operators
2809 -Woperator-whitespace-ext-conflict
2811 warn on uses of infix operators that would be parsed differently
2812 were a particular GHC extension enabled
2813 -Worphans
2815 warn when the module contains orphan instance declarations or
2816 rewrite rules
2817 -Woverflowed-literals
2819 warn about literals that will overflow their type
2820 -Woverlapping-patterns
2822 warn about overlapping patterns
2823 -Wpartial-fields
2825 warn when defining a partial record field.
2826 -Wpartial-type-signatures
2828 warn about holes in partial type signatures when
2829 PartialTypeSignatures is enabled. Not applicable when
2830 PartialTypeSignatures is not enabled, in which case errors are
2831 generated for such holes.
2832 -Wprepositive-qualified-module
2834 Report imports with a leading/prepositive "qualified"
2835 -Wredundant-bang-patterns
2837 Warn about redundant bang patterns.
2838 -Wredundant-constraints
2840 Have the compiler warn about redundant constraints in type sig‐
2841 natures.
2842 -Wredundant-record-wildcards
2844 Warn about record wildcard matches when the wildcard binds no
2845 patterns.
2846 -Wredundant-strictness-flags
2848 Warn about redundant strictness flags.
2849 -Wsafe warn if the module being compiled is regarded to be safe.
2851 -Wsemigroup
2853 warn when a Monoid is not Semigroup, and on non- Semigroup defi‐
2854 nitions of (<>)?
2855 -Wsimplifiable-class-constraints
2857 Warn about class constraints in a type signature that can be
2858 simplified using a top-level instance declaration.
2859 -Wstar-binder
2861 warn about binding the (*) type operator despite StarIsType
2862 -Wstar-is-type
2864 warn when * is used to mean Data.Kind.Type
2865 -Wtabs warn if there are tabs in the source file
2867 -Wtrustworthy-safe
2869 warn if the module being compiled is marked as Trustworthy but
2870 it could instead be marked as Safe, a more informative bound.
2871 -Wtype-defaults
2873 warn when defaulting happens
2874 -Wtype-equality-out-of-scope
2876 warn when type equality a ~ b is used despite being out of scope
2877 -Wtype-equality-requires-operators
2879 warn when type equality a ~ b is used despite being out of scope
2880 -Wtyped-holes
2882 Report warnings when typed hole errors are deferred until run‐
2883 time. See -fdefer-typed-holes.
2884 -Wunbanged-strict-patterns
2886 warn on pattern bind of unlifted variable that is neither bare
2887 nor banged
2888 -Wunicode-bidirectional-format-characters
2890 warn about the usage of unicode bidirectional layout override
2891 characters
2892 -Wunrecognised-pragmas
2894 warn about uses of pragmas that GHC doesn't recognise
2895 -Wunrecognised-warning-flags
2897 throw a warning when an unrecognised -W... flag is encountered
2898 on the command line.
2899 -Wunsafe
2901 warn if the module being compiled is regarded to be unsafe. See
2902 Safe Haskell
2903 -Wunsupported-calling-conventions
2905 warn about use of an unsupported calling convention
2906 -Wunsupported-llvm-version
2908 Warn when using -fllvm with an unsupported version of LLVM.
2909 -Wunticked-promoted-constructors
2911 warn if promoted constructors are not ticked
2912 -Wunused-binds
2914 warn about bindings that are unused. Alias for
2915 -Wunused-top-binds, -Wunused-local-binds and
2916 -Wunused-pattern-binds
2917 -Wunused-do-bind
2919 warn about do bindings that appear to throw away values of types
2920 other than ()
2921 -Wunused-foralls
2923 warn about type variables in user-written forall\s that are un‐
2924 used
2925 -Wunused-imports
2927 warn about unnecessary imports
2928 -Wunused-local-binds
2930 warn about local bindings that are unused
2931 -Wunused-matches
2933 warn about variables in patterns that aren't used
2934 -Wunused-packages
2936 warn when package is requested on command line, but not needed.
2937 -Wunused-pattern-binds
2939 warn about pattern match bindings that are unused
2940 -Wunused-record-wildcards
2942 Warn about record wildcard matches when none of the bound vari‐
2943 ables are used.
2944 -Wunused-top-binds
2946 warn about top-level bindings that are unused
2947 -Wunused-type-patterns
2949 warn about unused type variables which arise from patterns in in
2950 type family and data family instances
2951 -Wwarn make warnings non-fatal
2953 -Wwarnings-deprecations
2955 warn about uses of functions & types that have warnings or dep‐
2956 recated pragmas
2957 -Wwrong-do-bind
2959 warn about do bindings that appear to throw away monadic values
2960 that you should have bound instead
2961
2963 Copyright 2015. The University Court of the University of Glasgow. All
2964 rights reserved.
2965
2967 https://www.haskell.org/ghc the GHC homepage
2968
2970 The GHC Team
2971
2973 2023, GHC Team
29749.6.3 Sep 25, 2023 GHC(1)