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 -fexpose-internal-symbols
54 -fexternal-dynamic-refs -fllvm -fasm -fno-code -fobject-code
55 -fPIC -fPIE -fwrite-interface -split-objs
56 Debugging the compiler
58 -dasm-lint -dcmm-lint -dcore-lint -ddump-asm -ddump-asm-expanded
59 -ddump-asm-liveness -ddump-asm-native -ddump-asm-regalloc
60 -ddump-asm-regalloc-stages -ddump-asm-stats -ddump-bcos
61 -ddump-c-backend -ddump-cfg-weights -ddump-cmm -ddump-cmm-caf
62 -ddump-cmm-cbe -ddump-cmm-cfg -ddump-cmm-cps -ddump-cmm-from-stg
63 -ddump-cmm-info -ddump-cmm-opt -ddump-cmm-proc
64 -ddump-cmm-procmap -ddump-cmm-raw -ddump-cmm-sink -ddump-cmm-sp
65 -ddump-cmm-split -ddump-cmm-switch -ddump-cmm-verbose
66 -ddump-cmm-verbose-by-proc -ddump-core-stats -ddump-cpr-signa‐
67 tures -ddump-cpranal -ddump-cse -ddump-deriv -ddump-ds
68 -ddump-ds-preopt -ddump-ec-trace -ddump-faststrings
69 -ddump-file-prefix=⟨str⟩ -ddump-foreign -ddump-hie -ddump-hpc
70 -ddump-if-trace -ddump-inlinings -ddump-json -ddump-llvm
71 -ddump-mod-map -ddump-occur-anal -ddump-opt-cmm -ddump-parsed
72 -ddump-parsed-ast -ddump-prep -ddump-rn -ddump-rn-ast
73 -ddump-rn-stats -ddump-rn-trace -ddump-rtti -ddump-rule-firings
74 -ddump-rule-rewrites -ddump-rules -ddump-simpl -ddump-simpl-it‐
75 erations -ddump-simpl-stats -ddump-spec -ddump-splices
76 -ddump-stg -ddump-stg-final -ddump-stg-from-core
77 -ddump-stg-unarised -ddump-str-signatures -ddump-stranal
78 -ddump-tc -ddump-tc-ast -ddump-tc-trace -ddump-ticked
79 -ddump-timings -ddump-to-file -ddump-types -ddump-worker-wrapper
80 -dfaststring-stats -dhex-word-literals -dinitial-unique=⟨s⟩
81 -dinline-check=⟨str⟩ -dlinear-core-lint -dno-debug-output -dde‐
82 bug-output -dno-typeable-binds -dppr-case-as-let -dppr-cols=⟨n⟩
83 -dppr-debug -dppr-user-length -drule-check=⟨str⟩ -dshow-passes
84 -dstg-lint -dsuppress-all -dsuppress-coercions -dsuppress-idinfo
85 -dsuppress-module-prefixes -dsuppress-stg-free-vars -dsup‐
86 press-ticks -dsuppress-timestamps -dsuppress-type-applications
87 -dsuppress-type-signatures -dsuppress-unfoldings -dsup‐
88 press-uniques -dsuppress-var-kinds -dth-dec-file -dunique-incre‐
89 ment=⟨i⟩ -dverbose-core2core -dverbose-stg2stg -falignment-sani‐
90 tisation -fcatch-bottoms -fcheck-prim-bounds -fdistinct-con‐
91 structor-tables -finfo-table-map -fllvm-fill-undef-with-garbage
92 -fproc-alignment -g -g⟨n⟩
93 C pre-processor
95 -cpp -D⟨symbol⟩[=⟨value⟩] -U⟨symbol⟩ -I⟨dir⟩ -U⟨symbol⟩
96 Finding imports
98 -i -i⟨dir⟩[:⟨dir⟩]*
99 Interactive mode
101 -fbreak-on-error -fno-break-on-error -fbreak-on-exception
102 -fno-break-on-exception -fghci-hist-size=⟨n⟩ -fghci-leak-check
103 -fno-ghci-leak-check -flocal-ghci-history -fno-local-ghci-his‐
104 tory -fno-it -fno-no-it -fprint-bind-result -fno-print-bind-re‐
105 sult -fprint-evld-with-show -fshow-loaded-modules -ghci-script
106 -ignore-dot-ghci -no-ignore-dot-ghci -interactive-print ⟨name⟩
107 Interface files
109 --show-iface ⟨file⟩ -ddump-hi -ddump-hi-diffs -ddump-minimal-im‐
110 ports
111 Keeping intermediate files
113 -keep-hc-file -keep-hc-files -keep-hi-files -no-keep-hi-files
114 -keep-hscpp-file -keep-hscpp-files -keep-llvm-file
115 -keep-llvm-files -keep-o-files -no-keep-o-files -keep-s-file
116 -keep-s-files -keep-tmp-files
117 Language options
119 -XAllowAmbiguousTypes -XApplicativeDo -XArrows -XBangPatterns
120 -XBinaryLiterals -XBlockArguments -XCApiFFI -XConstrainedClass‐
121 Methods -XConstraintKinds -XCPP -XCUSKs -XDataKinds -XDatatype‐
122 Contexts -XDeepSubsumption -XDefaultSignatures -XDeriveAnyClass
123 -XDeriveDataTypeable -XDeriveFoldable -XDeriveFunctor -XDeriveG‐
124 eneric -XDeriveLift -XDeriveTraversable -XDerivingStrategies
125 -XDerivingVia -XDisambiguateRecordFields -XDuplicateRecordFields
126 -XEmptyCase -XEmptyDataDecls -XEmptyDataDeriving -XExisten‐
127 tialQuantification -XExplicitForAll -XExplicitNamespaces -XEx‐
128 tendedDefaultRules -XFieldSelectors -XFlexibleContexts -XFlexi‐
129 bleInstances -XForeignFunctionInterface -XFunctionalDependencies
130 -XGADTs -XGADTSyntax -XGeneralisedNewtypeDeriving -XGeneralized‐
131 NewtypeDeriving -XGHC2021 -XGHCForeignImportPrim -XHaskell2010
132 -XHaskell98 -XHexFloatLiterals -XImplicitParams -XImportQuali‐
133 fiedPost -XImpredicativeTypes -XIncoherentInstances -XInstance‐
134 Sigs -XInterruptibleFFI -XKindSignatures -XLambdaCase -XLexical‐
135 Negation -XLiberalTypeSynonyms -XLinearTypes -XMagicHash -XMon‐
136 adComprehensions -XMonoLocalBinds -XMultiParamTypeClasses -XMul‐
137 tiWayIf -XNamedFieldPuns -XNamedWildCards -XNegativeLiterals
138 -XNoImplicitPrelude -XNoMonomorphismRestriction -XNonde‐
139 creasingIndentation -XNoPatternGuards -XNoTraditionalRecordSyn‐
140 tax -XNPlusKPatterns -XNullaryTypeClasses -XNumDecimals -XNumer‐
141 icUnderscores -XOverlappingInstances -XOverloadedLabels -XOver‐
142 loadedLists -XOverloadedRecordDot -XOverloadedRecordUpdate
143 -XOverloadedStrings -XPackageImports -XParallelListComp -XPar‐
144 tialTypeSignatures -XPatternSynonyms -XPolyKinds -XPostfixOpera‐
145 tors -XQualifiedDo -XQuantifiedConstraints -XQuasiQuotes
146 -XRank2Types -XRankNTypes -XRebindableSyntax -XRecordWildCards
147 -XRecursiveDo -XRoleAnnotations -XSafe -XScopedTypeVariables
148 -XStandaloneDeriving -XStandaloneKindSignatures -XStarIsType
149 -XStaticPointers -XStrict -XStrictData -XTemplateHaskell -XTem‐
150 plateHaskellQuotes -XTransformListComp -XTrustworthy -XTupleSec‐
151 tions -XTypeApplications -XTypeFamilies -XTypeFamilyDependencies
152 -XTypeInType -XTypeOperators -XTypeSynonymInstances -XUnboxed‐
153 Sums -XUnboxedTuples -XUndecidableInstances -XUndecidableSuper‐
154 Classes -XUnicodeSyntax -XUnliftedDatatypes -XUnliftedFFITypes
155 -XUnliftedNewtypes -XUnsafe -XViewPatterns
156 Linking options
158 -c -debug -dylib-install-name ⟨path⟩ -dynamic -dynload -eventlog
159 -fcompact-unwind -fkeep-cafs -flink-rts -fno-embed-manifest
160 -fno-gen-manifest -fno-shared-implib -framework ⟨name⟩ -frame‐
161 work-path ⟨dir⟩ -fuse-rpaths -fwhole-archive-hs-libs -L ⟨dir⟩ -l
162 ⟨lib⟩ -main-is ⟨thing⟩ -no-hs-main -no-pie -pie -no-rtsopts-sug‐
163 gestions -package ⟨name⟩ -pie -no-pie -rdynamic -rt‐
164 sopts[=⟨none|some|all|ignore|ignoreAll⟩] -shared -split-sections
165 -static -staticlib -threaded -with-rtsopts=⟨opts⟩
166 Miscellaneous options
168 -fexternal-interpreter -ffamily-application-cache -fno-fam‐
169 ily-application-cache -fglasgow-exts -fno-glasgow-exts
170 -fno-safe-haskell -ghcversion-file ⟨path to ghcversion.h⟩ -H
171 ⟨size⟩ -j[⟨n⟩]
172 Modes of operation
174 --frontend ⟨module⟩ --help -? --info --interactive --make
175 --mk-dll --numeric-version --print-booter-version
176 --print-build-platform --print-c-compiler-flags --print-c-com‐
177 piler-link-flags --print-debug-on --print-global-package-db
178 --print-have-interpreter --print-have-native-code-generator
179 --print-host-platform --print-ld-flags --print-leading-under‐
180 score --print-libdir --print-object-splitting-supported
181 --print-project-git-commit-id --print-project-version
182 --print-rts-ways --print-stage --print-support-smp --print-ta‐
183 bles-next-to-code --print-target-platform --print-unregisterised
184 --run ⟨file⟩ --show-iface ⟨file⟩ --show-options --supported-ex‐
185 tensions --supported-languages --version -V -e ⟨expr⟩ -M
186 Individual optimizations
188 -fasm-shortcutting -fno-asm-shortcutting -fbinary-blob-thresh‐
189 old=⟨n⟩ -fblock-layout-cfg -fno-block-layout-cfg -fblock-lay‐
190 out-weightless -fno-block-layout-weightless -fblock-lay‐
191 out-weights -fcall-arity -fno-call-arity -fcase-folding
192 -fno-case-folding -fcase-merge -fno-case-merge -fcmm-elim-com‐
193 mon-blocks -fno-cmm-elim-common-blocks -fcmm-sink -fno-cmm-sink
194 -fcmm-static-pred -fno-cmm-static-pred -fcpr-anal -fno-cpr-anal
195 -fcross-module-specialise -fno-cross-module-specialise -fcse
196 -fno-cse -fdicts-cheap -fno-dicts-cheap -fdicts-strict
197 -fno-dicts-strict -fdmd-tx-dict-sel -fno-dmd-tx-dict-sel
198 -fdo-eta-reduction -fno-do-eta-reduction -fdo-lambda-eta-expan‐
199 sion -fno-do-lambda-eta-expansion -feager-blackholing -fen‐
200 able-rewrite-rules -fno-enable-rewrite-rules -fexcess-precision
201 -fno-excess-precision -fexitification -fno-exitification -fex‐
202 pose-all-unfoldings -fno-expose-all-unfoldings -ffloat-in
203 -fno-float-in -ffull-laziness -fno-full-laziness -ffun-to-thunk
204 -fno-fun-to-thunk -fignore-asserts -fno-ignore-asserts -fig‐
205 nore-interface-pragmas -fno-ignore-interface-pragmas -fin‐
206 line-generics -fno-inline-generics -finline-generics-aggres‐
207 sively -fno-inline-generics-aggressively -flate-dmd-anal
208 -fno-late-dmd-anal -flate-specialise -fno-late-specialise -flib‐
209 erate-case -fno-liberate-case -fliberate-case-threshold=⟨n⟩
210 -fno-liberate-case-threshold -fllvm-pass-vectors-in-regs -floop‐
211 ification -fno-loopification -fmax-inline-alloc-size=⟨n⟩
212 -fmax-inline-memcpy-insns=⟨n⟩ -fmax-inline-memset-insns=⟨n⟩
213 -fmax-simplifier-iterations=⟨n⟩ -fmax-uncovered-patterns=⟨n⟩
214 -fmax-worker-args=⟨n⟩ -fno-opt-coercion -fno-pre-inlining
215 -fno-state-hack -fomit-interface-pragmas -fno-omit-inter‐
216 face-pragmas -fomit-yields -fno-omit-yields -foptimal-applica‐
217 tive-do -fno-optimal-applicative-do -fpedantic-bottoms
218 -fno-pedantic-bottoms -fregs-graph -fno-regs-graph -fregs-itera‐
219 tive -fno-regs-iterative -fsimpl-tick-factor=⟨n⟩ -fsimpli‐
220 fier-phases=⟨n⟩ -fsolve-constant-dicts -fno-solve-constant-dicts
221 -fspec-constr -fno-spec-constr -fspec-constr-count=⟨n⟩
222 -fno-spec-constr-count -fspec-constr-keen -fno-spec-constr-keen
223 -fspec-constr-threshold=⟨n⟩ -fno-spec-constr-threshold -fspe‐
224 cialise -fno-specialise -fspecialise-aggressively -fno-spe‐
225 cialise-aggressively -fstatic-argument-transformation
226 -fno-static-argument-transformation -fstg-cse -fno-stg-cse
227 -fstg-lift-lams -fno-stg-lift-lams -fstg-lift-lams-known
228 -fno-stg-lift-lams-known -fstg-lift-lams-non-rec-args
229 -fstg-lift-lams-non-rec-args-any -fstg-lift-lams-rec-args
230 -fstg-lift-lams-rec-args-any -fstrictness -fno-strictness
231 -fstrictness-before=⟨n⟩ -funbox-small-strict-fields -fno-un‐
232 box-small-strict-fields -funbox-strict-fields -fno-un‐
233 box-strict-fields -funfolding-case-scaling=⟨n⟩ -funfold‐
234 ing-case-threshold=⟨n⟩ -funfolding-creation-threshold=⟨n⟩ -fun‐
235 folding-dict-discount=⟨n⟩ -funfolding-fun-discount=⟨n⟩ -funfold‐
236 ing-keeness-factor=⟨n⟩ -funfolding-use-threshold=⟨n⟩
237 -fworker-wrapper
238 Optimization levels
240 -O -O1 -O0 -O0 -O2 -O0 -O⟨n⟩ -O0
241 Package options
243 -clear-package-db -distrust ⟨pkg⟩ -distrust-all-packages -fpack‐
244 age-trust -global-package-db -hide-all-packages -hide-package
245 ⟨pkg⟩ -ignore-package ⟨pkg⟩ -no-auto-link-packages
246 -no-global-package-db -no-user-package-db -package ⟨pkg⟩ -pack‐
247 age-db ⟨file⟩ -package-env ⟨file⟩|⟨name⟩ -package-id ⟨unit-id⟩
248 -this-unit-id ⟨unit-id⟩ -trust ⟨pkg⟩ -user-package-db
249 Phases of compilation
251 -C -c -E -F -S -x ⟨suffix⟩
252 Overriding external programs
254 -pgma ⟨cmd⟩ -pgmc ⟨cmd⟩ -pgmdll ⟨cmd⟩ -pgmF ⟨cmd⟩ -pgmi ⟨cmd⟩
255 -pgminstall_name_tool ⟨cmd⟩ -pgmL ⟨cmd⟩ -pgml ⟨cmd⟩ -pgmlc ⟨cmd⟩
256 -pgmlibtool ⟨cmd⟩ -pgmlm ⟨cmd⟩ -pgmlo ⟨cmd⟩ -pgmotool ⟨cmd⟩
257 -pgmP ⟨cmd⟩ -pgms ⟨cmd⟩ -pgmwindres ⟨cmd⟩
258 Phase-specific options
260 -opta ⟨option⟩ -optc ⟨option⟩ -optcxx ⟨option⟩ -optdll ⟨option⟩
261 -optF ⟨option⟩ -opti ⟨option⟩ -optL ⟨option⟩ -optl ⟨option⟩
262 -optlc ⟨option⟩ -optlm ⟨option⟩ -optlo ⟨option⟩ -optP ⟨option⟩
263 -optwindres ⟨option⟩ -pgmc-supports-no-pie
264 Platform-specific options
266 -mavx -mavx2 -mavx512cd -mavx512er -mavx512f -mavx512pf -mbmi
267 -mbmi2 -msse -msse2 -msse3 -msse4 -msse4.2
268 Compiler plugins
270 -fclear-plugins -fplugin-opt=⟨module⟩:⟨args⟩ -fplugin-trustwor‐
271 thy -fplugin=⟨module⟩ -hide-all-plugin-packages -plugin-package
272 ⟨pkg⟩ -plugin-package-id ⟨pkg-id⟩
273 Profiling
275 -auto -auto-all -caf-all -fno-prof-count-entries
276 -fprof-count-entries -fprof-auto -fno-prof-auto
277 -fprof-auto-calls -fno-prof-auto -fprof-auto-exported
278 -fno-prof-auto -fprof-auto-top -fno-prof-auto -fprof-cafs
279 -fno-prof-cafs -fprof-callers=⟨name⟩ -no-auto -no-auto-all
280 -no-caf-all -prof -ticky -ticky-allocd -ticky-dyn-thunk
281 Program coverage
283 -fhpc
284 Recompilation checking
286 -fforce-recomp -fno-force-recomp -fignore-hpc-changes -fno-ig‐
287 nore-hpc-changes -fignore-optim-changes -fno-ignore-op‐
288 tim-changes
289 Redirecting output
291 --exclude-module=⟨file⟩ -ddump-mod-cycles -dep-makefile ⟨file⟩
292 -dep-suffix ⟨suffix⟩ -dumpdir ⟨dir⟩ -dynhisuf ⟨suffix⟩ -dyno
293 ⟨file⟩ -dynohi ⟨file⟩ -dynosuf ⟨suffix⟩ -hcsuf ⟨suffix⟩ -hidir
294 ⟨dir⟩ -hiedir ⟨dir⟩ -hiesuf ⟨suffix⟩ -hisuf ⟨suffix⟩ -in‐
295 clude-cpp-deps -include-pkg-deps -o ⟨file⟩ -odir ⟨dir⟩ -ohi
296 ⟨file⟩ -osuf ⟨suffix⟩ -outputdir ⟨dir⟩ -stubdir ⟨dir⟩
297 Temporary files
299 -tmpdir ⟨dir⟩
300 Verbosity options
302 -fabstract-refinement-hole-fits -fno-abstract-refine‐
303 ment-hole-fits -fdefer-diagnostics -fdiagnostics-color=⟨al‐
304 ways|auto|never⟩ -fdiagnostics-show-caret -fno-diagnos‐
305 tics-show-caret -ferror-spans -fhide-source-paths -fkeep-going
306 -fmax-refinement-hole-fits=⟨n⟩ -fno-max-refinement-hole-fits
307 -fmax-relevant-binds=⟨n⟩ -fno-max-relevant-binds
308 -fmax-valid-hole-fits=⟨n⟩ -fno-max-valid-hole-fits
309 -fno-show-valid-hole-fits -fno-sort-valid-hole-fits
310 -fsort-valid-hole-fits -fprint-axiom-incomps -fno-print-ax‐
311 iom-incomps -fprint-equality-relations -fno-print-equality-rela‐
312 tions -fprint-expanded-synonyms -fno-print-expanded-synonyms
313 -fprint-explicit-coercions -fno-print-explicit-coercions
314 -fprint-explicit-foralls -fno-print-explicit-foralls -fprint-ex‐
315 plicit-kinds -fno-print-explicit-kinds -fprint-explicit-run‐
316 time-reps -fno-print-explicit-runtime-reps -fprint-potential-in‐
317 stances -fno-print-potential-instances -fprint-typechecker-elab‐
318 oration -fno-print-typechecker-elaboration -fprint-unicode-syn‐
319 tax -fno-print-unicode-syntax -frefinement-level-hole-fits=⟨n⟩
320 -fno-refinement-level-hole-fits -freverse-errors -fno-re‐
321 verse-errors -fshow-docs-of-hole-fits
322 -fno-show-docs-of-hole-fits -fshow-hole-constraints
323 -fshow-hole-matches-of-hole-fits
324 -fno-show-hole-matches-of-hole-fits -fshow-prove‐
325 nance-of-hole-fits -fno-show-provenance-of-hole-fits
326 -fshow-type-app-of-hole-fits -fno-show-type-app-of-hole-fits
327 -fshow-type-app-vars-of-hole-fits
328 -fno-show-type-app-vars-of-hole-fits -fshow-type-of-hole-fits
329 -fno-show-type-of-hole-fits -fsort-by-size-hole-fits
330 -fno-sort-by-size-hole-fits -fsort-by-subsumption-hole-fits
331 -fno-sort-by-subsumption-hole-fits -funclutter-valid-hole-fits
332 -Rghc-timing -v -v⟨n⟩
333 Warnings
335 -fdefer-out-of-scope-variables -fno-defer-out-of-scope-variables
336 -fdefer-type-errors -fno-defer-type-errors -fdefer-typed-holes
337 -fno-defer-typed-holes -fenable-th-splice-warnings -fno-en‐
338 able-th-splice-warnings -fhelpful-errors -fno-helpful-errors
339 -fmax-pmcheck-models=⟨n⟩ -fshow-warning-groups -fno-show-warn‐
340 ing-groups -fvia-C -W -w -w -Wall -w -Wall-missed-specialisa‐
341 tions -Wno-all-missed-specialisations -Wall-missed-specializa‐
342 tions -Wno-all-missed-specializations -Wambiguous-fields
343 -Wauto-orphans -Wcompat -Wno-compat -Wcompat-unqualified-imports
344 -Wno-compat-unqualified-imports -Wcpp-undef -Wdefault -Wde‐
345 ferred-out-of-scope-variables -Wno-deferred-out-of-scope-vari‐
346 ables -Wdeferred-type-errors -Wno-deferred-type-errors -Wdepre‐
347 cated-flags -Wno-deprecated-flags -Wdeprecations -Wno-depreca‐
348 tions -Wderiving-defaults -Wno-deriving-defaults -Wderiving-ty‐
349 peable -Wno-deriving-typeable -Wdodgy-exports -Wno-dodgy-exports
350 -Wdodgy-foreign-imports -Wno-dodgy-foreign-imports -Wdodgy-im‐
351 ports -Wno-dodgy-imports -Wduplicate-constraints -Wno-dupli‐
352 cate-constraints -Wduplicate-exports -Wno-duplicate-exports
353 -Wempty-enumerations -Wno-empty-enumerations -Werror -Wwarn
354 -Weverything -Wextra -w -Whi-shadowing -Wno-hi-shadowing -Widen‐
355 tities -Wno-identities -Wimplicit-kind-vars -Wno-im‐
356 plicit-kind-vars -Wimplicit-lift -Wno-implicit-lift -Wim‐
357 plicit-prelude -Wno-implicit-prelude -Winaccessible-code
358 -Wno-inaccessible-code -Wincomplete-patterns -Wno-incom‐
359 plete-patterns -Wincomplete-record-updates -Wno-incom‐
360 plete-record-updates -Wincomplete-uni-patterns -Wno-incom‐
361 plete-uni-patterns -Winferred-safe-imports -Wno-in‐
362 ferred-safe-imports -Winline-rule-shadowing -Wno-in‐
363 line-rule-shadowing -Winvalid-haddock -Wno-invalid-haddock
364 -Wmissed-extra-shared-lib -Wno-missed-extra-shared-lib
365 -Wmissed-specialisations -Wno-missed-specialisations
366 -Wmissed-specializations -Wno-missed-specializations -Wmiss‐
367 ing-deriving-strategies -Wno-missing-deriving-strategies -Wmiss‐
368 ing-export-lists -Wno-missing-export-lists -Wmissing-ex‐
369 ported-signatures -Wno-missing-exported-signatures -Wmissing-ex‐
370 ported-sigs -Wno-missing-exported-sigs -Wmissing-fields
371 -Wno-missing-fields -Wmissing-home-modules -Wno-miss‐
372 ing-home-modules -Wmissing-import-lists -Wno-missing-im‐
373 port-lists -Wmissing-kind-signatures -Wno-missing-kind-signa‐
374 tures -Wmissing-local-signatures -Wno-missing-local-signatures
375 -Wmissing-local-sigs -Wno-missing-local-sigs -Wmissing-methods
376 -Wno-missing-methods -Wmissing-monadfail-instances -Wno-miss‐
377 ing-monadfail-instances -Wmissing-pattern-synonym-signatures
378 -Wno-missing-pattern-synonym-signatures -Wmiss‐
379 ing-safe-haskell-mode -Wno-missing-safe-haskell-mode -Wmiss‐
380 ing-signatures -Wno-missing-signatures -Wmissing-space-af‐
381 ter-bang -Wmonomorphism-restriction -Wno-monomorphism-restric‐
382 tion -Wname-shadowing -Wno-name-shadowing -Wno-compat -Wcompat
383 -Wnoncanonical-monad-instances -Wno-noncanonical-monad-instances
384 -Wnoncanonical-monadfail-instances -Wno-noncanonical-monad‐
385 fail-instances -Wnoncanonical-monoid-instances -Wno-noncanoni‐
386 cal-monoid-instances -Wnot -Woperator-whitespace -Wno-opera‐
387 tor-whitespace -Woperator-whitespace-ext-conflict -Wno-opera‐
388 tor-whitespace-ext-conflict -Worphans -Wno-orphans -Wover‐
389 flowed-literals -Wno-overflowed-literals -Woverlapping-patterns
390 -Wno-overlapping-patterns -Wpartial-fields -Wno-partial-fields
391 -Wpartial-type-signatures -Wno-partial-type-signatures -Wprepos‐
392 itive-qualified-module -Wno-prepositive-qualified-module -Wre‐
393 dundant-bang-patterns -Wno-redundant-bang-patterns -Wredun‐
394 dant-constraints -Wno-redundant-constraints -Wredun‐
395 dant-record-wildcards -Wno-redundant-record-wildcards -Wsafe
396 -Wno-safe -Wsemigroup -Wno-semigroup -Wsimplifiable-class-con‐
397 straints -Wno-simplifiable-class-constraints -Wstar-binder
398 -Wno-star-binder -Wstar-is-type -Wno-star-is-type -Wtabs
399 -Wno-tabs -Wtrustworthy-safe -Wno-safe -Wtype-defaults
400 -Wno-type-defaults -Wtyped-holes -Wno-typed-holes -Wun‐
401 banged-strict-patterns -Wno-unbanged-strict-patterns -Wuni‐
402 code-bidirectional-format-characters -Wunrecognised-pragmas
403 -Wno-unrecognised-pragmas -Wunrecognised-warning-flags -Wno-un‐
404 recognised-warning-flags -Wunsafe -Wno-unsafe -Wunsup‐
405 ported-calling-conventions -Wno-unsupported-calling-conventions
406 -Wunsupported-llvm-version -Wno-monomorphism-restriction
407 -Wunticked-promoted-constructors -Wno-unticked-promoted-con‐
408 structors -Wunused-binds -Wno-unused-binds -Wunused-do-bind
409 -Wno-unused-do-bind -Wunused-foralls -Wno-unused-foralls
410 -Wunused-imports -Wno-unused-imports -Wunused-local-binds
411 -Wno-unused-local-binds -Wunused-matches -Wno-unused-matches
412 -Wunused-packages -Wno-unused-packages -Wunused-pattern-binds
413 -Wno-unused-pattern-binds -Wunused-record-wildcards -Wno-un‐
414 used-record-wildcards -Wunused-top-binds -Wno-unused-top-binds
415 -Wunused-type-patterns -Wno-unused-type-patterns -Wwarn -Werror
416 -Wwarnings-deprecations -Wno-warnings-deprecations
417 -Wwrong-do-bind -Wno-wrong-do-bind
418 Code generation
420 -dynamic-too
421 Build dynamic object files as well as static object files during
422 compilation
423 -fasm Use the native code generator
425 -fbyte-code
427 Generate byte-code
428 -fexpose-internal-symbols
430 Produce symbols for all functions, including internal functions.
431 -fexternal-dynamic-refs
433 Generate code for linking against dynamic libraries
434 -fllvm Compile using the LLVM code generator
436 -fno-code
438 Omit code generation
439 -fobject-code
441 Generate object code
442 -fPIC Generate position-independent code (where available)
444 -fPIE Generate code for a position-independent executable (where
446 available)
447 -fwrite-interface
449 Always write interface files
450 -split-objs
452 Split generated object files into smaller files
453 Debugging the compiler
455 -dasm-lint
456 ASM pass sanity checking
457 -dcmm-lint
459 C-\- pass sanity checking
460 -dcore-lint
462 Turn on internal sanity checking
463 -ddump-asm
465 Dump final assembly
466 -ddump-asm-expanded
468 Dump the result of the synthetic instruction expansion pass.
469 -ddump-asm-liveness
471 Dump assembly augmented with register liveness
472 -ddump-asm-native
474 Dump initial assembly
475 -ddump-asm-regalloc
477 Dump the result of register allocation
478 -ddump-asm-regalloc-stages
480 Dump the build/spill stages of the -fregs-graph register alloca‐
481 tor.
482 -ddump-asm-stats
484 Dump statistics from the register allocator.
485 -ddump-bcos
487 Dump interpreter byte code
488 -ddump-c-backend
490 Dump C code produced by the C (unregisterised) backend.
491 -ddump-cfg-weights
493 Dump the assumed weights of the CFG.
494 -ddump-cmm
496 Dump the final C-\- output
497 -ddump-cmm-caf
499 Dump the results of the C-\- CAF analysis pass.
500 -ddump-cmm-cbe
502 Dump the results of common block elimination
503 -ddump-cmm-cfg
505 Dump the results of the C-\- control flow optimisation pass.
506 -ddump-cmm-cps
508 Dump the results of the CPS pass
509 -ddump-cmm-from-stg
511 Dump STG-to-C-\- output
512 -ddump-cmm-info
514 Dump the results of the C-\- info table augmentation pass.
515 -ddump-cmm-opt
517 Dump the results of C-\- to C-\- optimising passes
518 -ddump-cmm-proc
520 Dump the results of proc-point analysis
521 -ddump-cmm-procmap
523 Dump the results of the C-\- proc-point map pass.
524 -ddump-cmm-raw
526 Dump raw C-\-
527 -ddump-cmm-sink
529 Dump the results of the C-\- sinking pass.
530 -ddump-cmm-sp
532 Dump the results of the C-\- stack layout pass.
533 -ddump-cmm-split
535 Dump the results of the C-\- proc-point splitting pass.
536 -ddump-cmm-switch
538 Dump the results of switch lowering passes
539 -ddump-cmm-verbose
541 Write output from main C-\- pipeline passes to files
542 -ddump-cmm-verbose-by-proc
544 Show output from main C-\- pipeline passes (grouped by proc)
545 -ddump-core-stats
547 Print a one-line summary of the size of the Core program at the
548 end of the optimisation pipeline
549 -ddump-cpr-signatures
551 Dump CPR signatures
552 -ddump-cpranal
554 Dump CPR analysis output
555 -ddump-cse
557 Dump CSE output
558 -ddump-deriv
560 Dump deriving output
561 -ddump-ds
563 Dump desugarer output.
564 -ddump-ec-trace
566 Trace exhaustiveness checker
567 -ddump-faststrings
569 Dump the whole FastString table when finished
570 -ddump-file-prefix=⟨str⟩
572 Set the prefix of the filenames used for debugging output.
573 -ddump-foreign
575 Dump foreign export stubs
576 -ddump-hie
578 Dump the hie file syntax tree
579 -ddump-hpc
581 An alias for -ddump-ticked.
582 -ddump-if-trace
584 Trace interface files
585 -ddump-inlinings
587 Dump inlining info
588 -ddump-json
590 Dump error messages as JSON documents
591 -ddump-llvm
593 Dump LLVM intermediate code.
594 -ddump-mod-map
596 Dump the state of the module mapping database.
597 -ddump-occur-anal
599 Dump occurrence analysis output
600 -ddump-opt-cmm
602 Dump the results of C-\- to C-\- optimising passes
603 -ddump-parsed
605 Dump parse tree
606 -ddump-parsed-ast
608 Dump parser output as a syntax tree
609 -ddump-prep
611 Dump prepared core
612 -ddump-rn
614 Dump renamer output
615 -ddump-rn-ast
617 Dump renamer output as a syntax tree
618 -ddump-rn-stats
620 Renamer stats
621 -ddump-rn-trace
623 Trace renamer
624 -ddump-rtti
626 Trace runtime type inference
627 -ddump-rule-firings
629 Dump rule firing info
630 -ddump-rule-rewrites
632 Dump detailed rule firing info
633 -ddump-rules
635 Dump rewrite rules
636 -ddump-simpl
638 Dump final simplifier output
639 -ddump-simpl-iterations
641 Dump output from each simplifier iteration
642 -ddump-simpl-stats
644 Dump simplifier stats
645 -ddump-spec
647 Dump specialiser output
648 -ddump-splices
650 Dump TH spliced expressions, and what they evaluate to
651 -ddump-stg
653 (deprecated) Alias for -ddump-stg-from-core
654 -ddump-stg-final
656 Show output of last STG pass.
657 -ddump-stg-from-core
659 Show CoreToStg output
660 -ddump-stg-unarised
662 Show unarised STG
663 -ddump-str-signatures
665 Dump top-level demand signatures
666 -ddump-stranal
668 Dump demand analysis output
669 -ddump-tc
671 Dump typechecker output
672 -ddump-tc-ast
674 Dump typechecker output as a syntax tree
675 -ddump-tc-trace
677 Trace typechecker
678 -ddump-ticked
680 Dump the code instrumented by HPC (Observing Code Coverage).
681 -ddump-timings
683 Dump per-pass timing and allocation statistics
684 -ddump-to-file
686 Dump to files instead of stdout
687 -ddump-types
689 Dump type signatures
690 -ddump-worker-wrapper
692 Dump worker-wrapper output
693 -dfaststring-stats
695 Show statistics for fast string usage when finished
696 -dhex-word-literals
698 Print values of type Word# in hexadecimal.
699 -dinitial-unique=⟨s⟩
701 Start UniqSupply allocation from ⟨s⟩.
702 -dinline-check=⟨str⟩
704 Dump information about inlining decisions
705 -dlinear-core-lint
707 Turn on internal sanity checking
708 -dno-debug-output
710 Suppress unsolicited debugging output
711 -dno-typeable-binds
713 Don't generate bindings for Typeable methods
714 -dppr-case-as-let
716 Print single alternative case expressions as strict lets.
717 -dppr-cols=⟨n⟩
719 Set the width of debugging output. For example -dppr-cols200
720 -dppr-debug
722 Turn on debug printing (more verbose)
723 -dppr-user-length
725 Set the depth for printing expressions in error msgs
726 -drule-check=⟨str⟩
728 Dump information about potential rule application
729 -dshow-passes
731 Print out each pass name as it happens
732 -dstg-lint
734 STG pass sanity checking
735 -dsuppress-all
737 In dumps, suppress everything (except for uniques) that is sup‐
738 pressible.
739 -dsuppress-coercions
741 Suppress the printing of coercions in Core dumps to make them
742 shorter
743 -dsuppress-idinfo
745 Suppress extended information about identifiers where they are
746 bound
747 -dsuppress-module-prefixes
749 Suppress the printing of module qualification prefixes
750 -dsuppress-stg-free-vars
752 Suppress the printing of closure free variable lists in STG out‐
753 put
754 -dsuppress-ticks
756 Suppress "ticks" in the pretty-printer output.
757 -dsuppress-timestamps
759 Suppress timestamps in dumps
760 -dsuppress-type-applications
762 Suppress type applications
763 -dsuppress-type-signatures
765 Suppress type signatures
766 -dsuppress-unfoldings
768 Suppress the printing of the stable unfolding of a variable at
769 its binding site
770 -dsuppress-uniques
772 Suppress the printing of uniques in debug output (easier to use
773 diff)
774 -dsuppress-var-kinds
776 Suppress the printing of variable kinds
777 -dth-dec-file
779 Dump evaluated TH declarations into *.th.hs files
780 -dunique-increment=⟨i⟩
782 Set the increment for the generated Unique's to ⟨i⟩.
783 -dverbose-core2core
785 Show output from each core-to-core pass
786 -dverbose-stg2stg
788 Show output from each STG-to-STG pass
789 -falignment-sanitisation
791 Compile with alignment checks for all info table dereferences.
792 -fcatch-bottoms
794 Add a default error alternative to case expressions without a
795 default alternative.
796 -fcheck-prim-bounds
798 Instrument array primops with bounds checks.
799 -fdistinct-constructor-tables
801 Generate a fresh info table for each usage of a data construc‐
802 tor.
803 -finfo-table-map
805 Embed a lookup table in the generated binary which maps the ad‐
806 dress of an info table to the source position the closure origi‐
807 nated from.
808 -fllvm-fill-undef-with-garbage
810 Intruct LLVM to fill dead STG registers with garbage
811 -fproc-alignment
813 Align functions at given boundary.
814 -g Produce DWARF debug information in compiled object files. ⟨n⟩
816 can be 0, 1, or 2, with higher numbers producing richer output.
817 If ⟨n⟩ is omitted, level 2 is assumed.
818 C pre-processor
820 -cpp Run the C pre-processor on Haskell source files
821 -D⟨symbol⟩[=⟨value⟩]
823 Define a symbol in the C pre-processor
824 -I⟨dir⟩
826 Add ⟨dir⟩ to the directory search list for #include files
827 -U⟨symbol⟩
829 Undefine a symbol in the C pre-processor
830 Finding imports
832 -i Empty the import directory list
833 -i⟨dir⟩[:⟨dir⟩]*
835 add ⟨dir⟩, ⟨dir2⟩, etc. to import path
836 Interactive mode
838 -fbreak-on-error
839 Break on uncaught exceptions and errors
840 -fbreak-on-exception
842 Break on any exception thrown
843 -fghci-hist-size=⟨n⟩
845 Set the number of entries GHCi keeps for :history. See The GHCi
846 Debugger.
847 -fghci-leak-check
849 (Debugging only) check for space leaks when loading new modules
850 in GHCi.
851 -flocal-ghci-history
853 Use current directory for the GHCi command history file
854 .ghci-history.
855 -fno-it
857 No longer set the special variable it.
858 -fprint-bind-result
860 Turn on printing of binding results in GHCi
861 -fprint-evld-with-show
863 Instruct :print to use Show instances where possible.
864 -fshow-loaded-modules
866 Show the names of modules that GHCi loaded after a :load com‐
867 mand.
868 -ghci-script
870 Read additional .ghci files
871 -ignore-dot-ghci
873 Disable reading of .ghci files
874 -interactive-print ⟨name⟩
876 Select the function to use for printing evaluated expressions in
877 GHCi
878 Interface files
880 --show-iface ⟨file⟩
881 See Modes of operation.
882 -ddump-hi
884 Dump the new interface to stdout
885 -ddump-hi-diffs
887 Show the differences vs. the old interface
888 -ddump-minimal-imports
890 Dump a minimal set of imports
891 Keeping intermediate files
893 -keep-hc-file
894 Retain intermediate .hc files.
895 -keep-hi-files
897 Retain intermediate .hi files (the default).
898 -keep-hscpp-file
900 Retain intermediate .hscpp files.
901 -keep-llvm-file
903 Retain intermediate LLVM .ll files. Implies -fllvm.
904 -keep-o-files
906 Retain intermediate .o files (the default).
907 -keep-s-file
909 Retain intermediate .s files.
910 -keep-tmp-files
912 Retain all intermediate temporary files.
913 Language options
915 -XAllowAmbiguousTypes
916 Allow the user to write ambiguous types, and the type inference
917 engine to infer them.
918 -XApplicativeDo
920 Enable Applicative do-notation desugaring
921 -XArrows
923 Enable arrow notation extension
924 -XBangPatterns
926 Enable bang patterns.
927 -XBinaryLiterals
929 Enable support for binary literals.
930 -XBlockArguments
932 Allow do blocks and other constructs as function arguments.
933 -XCApiFFI
935 Enable the CAPI calling convention.
936 -XConstrainedClassMethods
938 Enable constrained class methods.
939 -XConstraintKinds
941 Enable a kind of constraints.
942 -XCPP Enable the C preprocessor.
944 -XCUSKs
946 Enable detection of complete user-supplied kind signatures.
947 -XDataKinds
949 Enable datatype promotion.
950 -XDatatypeContexts
952 Allow contexts on data types.
953 -XDeepSubsumption
955 Enable deep subsumption
956 -XDefaultSignatures
958 Enable default signatures.
959 -XDeriveAnyClass
961 Enable deriving for any class.
962 -XDeriveDataTypeable
964 Enable deriving for the Data class. Implied by (deprecated) Au‐
965 toDeriveTypeable.
966 -XDeriveFoldable
968 Enable deriving for the Foldable class. Implied by
969 DeriveTraversable.
970 -XDeriveFunctor
972 Enable deriving for the Functor class. Implied by
973 DeriveTraversable.
974 -XDeriveGeneric
976 Enable deriving for the Generic class.
977 -XDeriveLift
979 Enable deriving for the Lift class
980 -XDeriveTraversable
982 Enable deriving for the Traversable class. Implies
983 DeriveFunctor and DeriveFoldable.
984 -XDerivingStrategies
986 Enables deriving strategies.
987 -XDerivingVia
989 Enable deriving instances via types of the same runtime repre‐
990 sentation. Implies DerivingStrategies.
991 -XDisambiguateRecordFields
993 Enable record field disambiguation. Implied by RecordWildCards.
994 -XDuplicateRecordFields
996 Allow definition of record types with identically-named fields.
997 -XEmptyCase
999 Allow empty case alternatives.
1000 -XEmptyDataDecls
1002 Allow definition of empty data types.
1003 -XEmptyDataDeriving
1005 Allow deriving instances of standard type classes for empty data
1006 types.
1007 -XExistentialQuantification
1009 Enable liberalised type synonyms.
1010 -XExplicitForAll
1012 Enable explicit universal quantification. Implied by
1013 ScopedTypeVariables, LiberalTypeSynonyms, RankNTypes and
1014 ExistentialQuantification.
1015 -XExplicitNamespaces
1017 Enable using the keyword type to specify the namespace of en‐
1018 tries in imports and exports (Explicit namespaces in import/ex‐
1019 port). Implied by TypeOperators and TypeFamilies.
1020 -XExtendedDefaultRules
1022 Use GHCi's extended default rules in a normal module.
1023 -XFieldSelectors
1025 Control visibility of field selector functions.
1026 -XFlexibleContexts
1028 Remove some restrictions on class contexts
1029 -XFlexibleInstances
1031 Enable flexible instances. Implies TypeSynonymInstances.
1032 -XForeignFunctionInterface
1034 Enable foreign function interface.
1035 -XFunctionalDependencies
1037 Enable functional dependencies. Implies MultiParamTypeClasses.
1038 -XGADTs
1040 Enable generalised algebraic data types. Implies GADTSyntax and
1041 MonoLocalBinds.
1042 -XGADTSyntax
1044 Enable generalised algebraic data type syntax.
1045 -XGeneralisedNewtypeDeriving
1047 Enable newtype deriving.
1048 -XGeneralizedNewtypeDeriving
1050 Enable newtype deriving.
1051 -XGHC2021
1053 Use GHC’s set of default language extensions from 2021
1054 -XGHCForeignImportPrim
1056 Enable prim calling convention. Intended for internal use only.
1057 -XHaskell2010
1059 Use the Haskell 2010 language variant.
1060 -XHaskell98
1062 Use the Haskell 98 language variant.
1063 -XHexFloatLiterals
1065 Enable support for hexadecimal floating point literals.
1066 -XImplicitParams
1068 Enable Implicit Parameters.
1069 -XImportQualifiedPost
1071 ImportQualifiedPost allows the syntax import M qualified
1072 -XImpredicativeTypes
1074 Enable impredicative types. Implies RankNTypes.
1075 -XIncoherentInstances
1077 Enable incoherent instances. Implies OverlappingInstances.
1078 -XInstanceSigs
1080 Enable instance signatures.
1081 -XInterruptibleFFI
1083 Enable interruptible FFI.
1084 -XKindSignatures
1086 Enable kind signatures. Implied by TypeFamilies and PolyKinds.
1087 -XLambdaCase
1089 Enable lambda-case expressions.
1090 -XLexicalNegation
1092 Use whitespace to determine whether the minus sign stands for
1093 negation or subtraction.
1094 -XLiberalTypeSynonyms
1096 Enable liberalised type synonyms.
1097 -XLinearTypes
1099 Enable linear types.
1100 -XMagicHash
1102 Allow # as a postfix modifier on identifiers.
1103 -XMonadComprehensions
1105 Enable monad comprehensions.
1106 -XMonoLocalBinds
1108 Enable do not generalise local bindings. Implied by
1109 TypeFamilies and GADTs.
1110 -XMultiParamTypeClasses
1112 Enable multi parameter type classes. Implied by
1113 FunctionalDependencies.
1114 -XMultiWayIf
1116 Enable multi-way if-expressions.
1117 -XNamedFieldPuns
1119 Enable record puns.
1120 -XNamedWildCards
1122 Enable named wildcards.
1123 -XNegativeLiterals
1125 Enable support for negative literals.
1126 -XNoImplicitPrelude
1128 Don't implicitly import Prelude. Implied by RebindableSyntax.
1129 -XNoMonomorphismRestriction
1131 Disable the monomorphism restriction.
1132 -XNondecreasingIndentation
1134 Allow nested contexts to be at the same indentation level as its
1135 enclosing context.
1136 -XNoPatternGuards
1138 Disable pattern guards. Implied by Haskell98.
1139 -XNoTraditionalRecordSyntax
1141 Disable support for traditional record syntax (as supported by
1142 Haskell 98) C {f = x}
1143 -XNPlusKPatterns
1145 Enable support for n+k patterns. Implied by Haskell98.
1146 -XNullaryTypeClasses
1148 Deprecated, does nothing. nullary (no parameter) type classes
1149 are now enabled using MultiParamTypeClasses.
1150 -XNumDecimals
1152 Enable support for 'fractional' integer literals.
1153 -XNumericUnderscores
1155 Enable support for numeric underscores.
1156 -XOverlappingInstances
1158 Enable overlapping instances.
1159 -XOverloadedLabels
1161 Enable overloaded labels.
1162 -XOverloadedLists
1164 Enable overloaded lists.
1165 -XOverloadedRecordDot
1167 Record '.' syntax
1168 -XOverloadedRecordUpdate
1170 Record '.' syntax record updates
1171 -XOverloadedStrings
1173 Enable overloaded string literals.
1174 -XPackageImports
1176 Enable package-qualified imports.
1177 -XParallelListComp
1179 Enable parallel list comprehensions.
1180 -XPartialTypeSignatures
1182 Enable partial type signatures.
1183 -XPatternSynonyms
1185 Enable pattern synonyms.
1186 -XPolyKinds
1188 Enable kind polymorphism. Implies KindSignatures.
1189 -XPostfixOperators
1191 Enable postfix operators.
1192 -XQualifiedDo
1194 Enable qualified do-notation desugaring.
1195 -XQuantifiedConstraints
1197 Allow forall quantifiers in constraints.
1198 -XQuasiQuotes
1200 Enable quasiquotation.
1201 -XRank2Types
1203 Enable rank-2 types. Synonym for RankNTypes.
1204 -XRankNTypes
1206 Enable rank-N types. Implied by ImpredicativeTypes.
1207 -XRebindableSyntax
1209 Employ rebindable syntax. Implies NoImplicitPrelude.
1210 -XRecordWildCards
1212 Enable record wildcards. Implies DisambiguateRecordFields.
1213 -XRecursiveDo
1215 Enable recursive do (mdo) notation.
1216 -XRoleAnnotations
1218 Enable role annotations.
1219 -XSafe Enable the Safe Haskell Safe mode.
1221 -XScopedTypeVariables
1223 Enable lexically-scoped type variables.
1224 -XStandaloneDeriving
1226 Enable standalone deriving.
1227 -XStandaloneKindSignatures
1229 Allow the use of standalone kind signatures.
1230 -XStarIsType
1232 Treat * as Data.Kind.Type.
1233 -XStaticPointers
1235 Enable static pointers.
1236 -XStrict
1238 Make bindings in the current module strict by default.
1239 -XStrictData
1241 Enable default strict datatype fields.
1242 -XTemplateHaskell
1244 Enable Template Haskell.
1245 -XTemplateHaskellQuotes
1247 Enable quotation subset of Template Haskell.
1248 -XTransformListComp
1250 Enable generalised list comprehensions.
1251 -XTrustworthy
1253 Enable the Safe Haskell Trustworthy mode.
1254 -XTupleSections
1256 Enable tuple sections.
1257 -XTypeApplications
1259 Enable type application syntax in terms, patterns and types.
1260 -XTypeFamilies
1262 Enable type families. Implies ExplicitNamespaces,
1263 KindSignatures, and MonoLocalBinds.
1264 -XTypeFamilyDependencies
1266 Enable injective type families. Implies TypeFamilies.
1267 -XTypeInType
1269 Deprecated. Enable kind polymorphism and datatype promotion.
1270 -XTypeOperators
1272 Enable type operators. Implies ExplicitNamespaces.
1273 -XTypeSynonymInstances
1275 Enable type synonyms in instance heads. Implied by
1276 FlexibleInstances.
1277 -XUnboxedSums
1279 Enable unboxed sums.
1280 -XUnboxedTuples
1282 Enable the use of unboxed tuple syntax.
1283 -XUndecidableInstances
1285 Enable undecidable instances.
1286 -XUndecidableSuperClasses
1288 Allow all superclass constraints, including those that may re‐
1289 sult in non-termination of the typechecker.
1290 -XUnicodeSyntax
1292 Enable unicode syntax.
1293 -XUnliftedDatatypes
1295 Enable unlifted data types.
1296 -XUnliftedFFITypes
1298 Enable unlifted FFI types
1299 -XUnliftedNewtypes
1301 Enable unlifted newtypes.
1302 -XUnsafe
1304 Enable Safe Haskell Unsafe mode.
1305 -XViewPatterns
1307 Enable view patterns.
1308 Linking options
1310 -c Stop after generating object (.o) file
1311 -debug Use the debugging runtime
1313 -dylib-install-name ⟨path⟩
1315 Set the install name (via -install_name passed to Apple's
1316 linker), specifying the full install path of the library file.
1317 Any libraries or executables that link with it later will pick
1318 up that path as their runtime search location for it. (Dar‐
1319 win/OS X only)
1320 -dynamic
1322 Build dynamically-linked object files and executables
1323 -dynload
1325 Selects one of a number of modes for finding shared libraries at
1326 runtime.
1327 -eventlog
1329 Enable runtime event tracing
1330 -fcompact-unwind
1332 Instruct the linker to produce a __compact_unwind section.
1333 -fkeep-cafs
1335 Do not garbage-collect CAFs (top-level expressions) at runtime
1336 -flink-rts
1338 Link the runtime when generating a shared or static library
1339 -fno-embed-manifest
1341 Do not embed the manifest in the executable (Windows only)
1342 -fno-gen-manifest
1344 Do not generate a manifest file (Windows only)
1345 -fno-shared-implib
1347 Don't generate an import library for a DLL (Windows only)
1348 -framework ⟨name⟩
1350 On Darwin/OS X/iOS only, link in the framework ⟨name⟩. This op‐
1351 tion corresponds to the -framework option for Apple's Linker.
1352 -framework-path ⟨dir⟩
1354 On Darwin/OS X/iOS only, add ⟨dir⟩ to the list of directories
1355 searched for frameworks. This option corresponds to the -F op‐
1356 tion for Apple's Linker.
1357 -fuse-rpaths
1359 Set the rpath based on -L flags
1360 -fwhole-archive-hs-libs
1362 When linking a binary executable, this inserts the flag
1363 -Wl,--whole-archive before any -l flags for Haskell libraries,
1364 and -Wl,--no-whole-archive afterwards
1365 -L ⟨dir⟩
1367 Add ⟨dir⟩ to the list of directories searched for libraries
1368 -l ⟨lib⟩
1370 Link in library ⟨lib⟩
1371 -main-is ⟨thing⟩
1373 Set main module and function
1374 -no-hs-main
1376 Don't assume this program contains main
1377 -no-pie
1379 Don't instruct the linker to produce a position-independent exe‐
1380 cutable.
1381 -no-rtsopts-suggestions
1383 Don't print RTS suggestions about linking with
1384 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩].
1385 -package ⟨name⟩
1387 Expose package ⟨pkg⟩
1388 -pie Instruct the linker to produce a position-independent exe‐
1390 cutable.
1391 -rdynamic
1393 This instructs the linker to add all symbols, not only used
1394 ones, to the dynamic symbol table. Currently Linux and Win‐
1395 dows/MinGW32 only. This is equivalent to using -optl -rdynamic
1396 on Linux, and -optl -export-all-symbols on Windows.
1397 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩]
1399 Control whether the RTS behaviour can be tweaked via com‐
1400 mand-line flags and the GHCRTS environment variable. Using none
1401 means no RTS flags can be given; some means only a minimum of
1402 safe options can be given (the default); all (or no argument at
1403 all) means that all RTS flags are permitted; ignore means RTS
1404 flags can be given, but are treated as regular arguments and
1405 passed to the Haskell program as arguments; ignoreAll is the
1406 same as ignore, but GHCRTS is also ignored. -rtsopts does not
1407 affect -with-rtsopts behavior; flags passed via -with-rtsopts
1408 are used regardless of -rtsopts.
1409 -shared
1411 Generate a shared library (as opposed to an executable)
1412 -split-sections
1414 Split sections for link-time dead-code stripping
1415 -static
1417 Use static Haskell libraries
1418 -staticlib
1420 Generate a standalone static library (as opposed to an exe‐
1421 cutable). This is useful when cross compiling. The library to‐
1422 gether with all its dependencies ends up in in a single static
1423 library that can be linked against.
1424 -threaded
1426 Use the threaded runtime
1427 -with-rtsopts=⟨opts⟩
1429 Set the default RTS options to ⟨opts⟩.
1430 Miscellaneous options
1432 -fexternal-interpreter
1433 Run interpreted code in a separate process
1434 -ffamily-application-cache
1436 Use a cache when reducing type family applications
1437 -fglasgow-exts
1439 Deprecated. Enable most language extensions; see Controlling ex‐
1440 tensions for exactly which ones.
1441 -fno-safe-haskell
1443 Disable Safe Haskell
1444 -ghcversion-file ⟨path to ghcversion.h⟩
1446 (GHC as a C compiler only) Use this ghcversion.h file
1447 -H ⟨size⟩
1449 Set the minimum size of the heap to ⟨size⟩
1450 -j[⟨n⟩]
1452 When compiling with --make, compile ⟨n⟩ modules in parallel.
1453 Modes of operation
1455 --frontend ⟨module⟩
1456 run GHC with the given frontend plugin; see Frontend plugins for
1457 details.
1458 --help Display help
1460 --info display information about the compiler
1462 --interactive
1464 Interactive mode - normally used by just running ghci; see Using
1465 GHCi for details.
1466 --make Build a multi-module Haskell program, automatically figuring out
1468 dependencies. Likely to be much easier, and faster, than using
1469 make; see Using ghc --make for details.
1470 --mk-dll
1472 DLL-creation mode (Windows only)
1473 --numeric-version
1475 display GHC version (numeric only)
1476 --print-booter-version
1478 display bootstrap compiler version
1479 --print-build-platform
1481 display platform on which GHC was built
1482 --print-c-compiler-flags
1484 C compiler flags used to build GHC
1485 --print-c-compiler-link-flags
1487 C linker flags used to build GHC
1488 --print-debug-on
1490 print whether GHC was built with -DDEBUG
1491 --print-global-package-db
1493 display GHC's global package database directory
1494 --print-have-interpreter
1496 display whether GHC was built with interactive support
1497 --print-have-native-code-generator
1499 display whether target platform has NCG support
1500 --print-host-platform
1502 display host platform of GHC
1503 --print-ld-flags
1505 display linker flags used to compile GHC
1506 --print-leading-underscore
1508 display use of leading underscores on symbol names
1509 --print-libdir
1511 display GHC library directory
1512 --print-object-splitting-supported
1514 display whether GHC supports object splitting
1515 --print-project-git-commit-id
1517 display Git commit id GHC is built from
1518 --print-project-version
1520 display GHC version
1521 --print-rts-ways
1523 display which way RTS was built
1524 --print-stage
1526 display stage number of GHC
1527 --print-support-smp
1529 display whether GHC was compiled with SMP support
1530 --print-tables-next-to-code
1532 display whether GHC was compiled with --enable-ta‐
1533 bles-next-to-code
1534 --print-target-platform
1536 display target platform of GHC
1537 --print-unregisterised
1539 display whether this GHC was built in unregisterised mode
1540 --run ⟨file⟩
1542 Run a Haskell program.
1543 --show-iface ⟨file⟩
1545 display the contents of an interface file.
1546 --show-options
1548 display the supported command line options
1549 --supported-extensions
1551 display the supported language extensions
1552 --version
1554 display GHC version
1555 -e ⟨expr⟩
1557 Evaluate expr; see Expression evaluation mode for details.
1558 -M generate dependency information suitable for use in a Makefile;
1560 see Dependency generation for details.
1561 Individual optimizations
1563 -fasm-shortcutting
1564 Enable shortcutting on assembly. Implied by -O2.
1565 -fbinary-blob-threshold=⟨n⟩
1567 default: 500K. Tweak assembly generator for binary blobs.
1568 -fblock-layout-cfg
1570 Use the new cfg based block layout algorithm.
1571 -fblock-layout-weightless
1573 Ignore cfg weights for code layout.
1574 -fblock-layout-weights
1576 Sets edge weights used by the new code layout algorithm.
1577 -fcall-arity
1579 Enable call-arity optimisation. Implied by -O.
1580 -fcase-folding
1582 Enable constant folding in case expressions. Implied by -O.
1583 -fcase-merge
1585 Enable case-merging. Implied by -O.
1586 -fcmm-elim-common-blocks
1588 Enable Cmm common block elimination. Implied by -O.
1589 -fcmm-sink
1591 Enable Cmm sinking. Implied by -O.
1592 -fcmm-static-pred
1594 Enable static control flow prediction. Implied by -O.
1595 -fcpr-anal
1597 Turn on CPR analysis in the demand analyser. Implied by -O.
1598 -fcross-module-specialise
1600 Turn on specialisation of overloaded functions imported from
1601 other modules.
1602 -fcse Enable common sub-expression elimination. Implied by -O.
1604 -fdicts-cheap
1606 Make dictionary-valued expressions seem cheap to the optimiser.
1607 -fdicts-strict
1609 Make dictionaries strict
1610 -fdmd-tx-dict-sel
1612 (deprecated) Use a special demand transformer for dictionary se‐
1613 lectors.
1614 -fdo-eta-reduction
1616 Enable eta-reduction. Implied by -O.
1617 -fdo-lambda-eta-expansion
1619 Enable lambda eta-expansion. Always enabled by default.
1620 -feager-blackholing
1622 Turn on eager blackholing
1623 -fenable-rewrite-rules
1625 Switch on all rewrite rules (including rules generated by auto‐
1626 matic specialisation of overloaded functions). Implied by -O.
1627 -fexcess-precision
1629 Enable excess intermediate precision
1630 -fexitification
1632 Enables exitification optimisation. Implied by -O.
1633 -fexpose-all-unfoldings
1635 Expose all unfoldings, even for very large or recursive func‐
1636 tions.
1637 -ffloat-in
1639 Turn on the float-in transformation. Implied by -O.
1640 -ffull-laziness
1642 Turn on full laziness (floating bindings outwards). Implied by
1643 -O.
1644 -ffun-to-thunk
1646 Allow worker-wrapper to convert a function closure into a thunk
1647 if the function does not use any of its arguments. Off by de‐
1648 fault.
1649 -fignore-asserts
1651 Ignore assertions in the source. Implied by -O.
1652 -fignore-interface-pragmas
1654 Ignore pragmas in interface files. Implied by -O0 only.
1655 -finline-generics
1657 Annotate methods of derived Generic and Generic1 instances with
1658 INLINE[1] pragmas based on heuristics. Implied by -O.
1659 -finline-generics-aggressively
1661 Annotate methods of all derived Generic and Generic1 instances
1662 with INLINE[1] pragmas.
1663 -flate-dmd-anal
1665 Run demand analysis again, at the end of the simplification
1666 pipeline
1667 -flate-specialise
1669 Run a late specialisation pass
1670 -fliberate-case
1672 Turn on the liberate-case transformation. Implied by -O2.
1673 -fliberate-case-threshold=⟨n⟩
1675 default: 2000. Set the size threshold for the liberate-case
1676 transformation to ⟨n⟩
1677 -fllvm-pass-vectors-in-regs
1679 (deprecated) Does nothing
1680 -floopification
1682 Turn saturated self-recursive tail-calls into local jumps in the
1683 generated assembly. Implied by -O.
1684 -fmax-inline-alloc-size=⟨n⟩
1686 default: 128. Set the maximum size of inline array allocations
1687 to ⟨n⟩ bytes (default: 128).
1688 -fmax-inline-memcpy-insns=⟨n⟩
1690 default: 32. Inline memcpy calls if they would generate no more
1691 than ⟨n⟩ pseudo instructions.
1692 -fmax-inline-memset-insns=⟨n⟩
1694 default: 32. Inline memset calls if they would generate no more
1695 than ⟨n⟩ pseudo instructions
1696 -fmax-simplifier-iterations=⟨n⟩
1698 default: 4. Set the max iterations for the simplifier.
1699 -fmax-uncovered-patterns=⟨n⟩
1701 default: 4. Set the maximum number of patterns to display in
1702 warnings about non-exhaustive ones.
1703 -fmax-worker-args=⟨n⟩
1705 default: 10. Maximum number of value arguments for a worker.
1706 -fno-opt-coercion
1708 Turn off the coercion optimiser
1709 -fno-pre-inlining
1711 Turn off pre-inlining
1712 -fno-state-hack
1714 Turn off the state hackwhereby any lambda with a real-world
1715 state token as argument is considered to be single-entry. Hence
1716 OK to inline things inside it.
1717 -fomit-interface-pragmas
1719 Don't generate interface pragmas. Implied by -O0 only.
1720 -fomit-yields
1722 Omit heap checks when no allocation is being performed.
1723 -foptimal-applicative-do
1725 Use a slower but better algorithm for ApplicativeDo
1726 -fpedantic-bottoms
1728 Make GHC be more precise about its treatment of bottom (but see
1729 also -fno-state-hack). In particular, GHC will not eta-expand
1730 through a case expression.
1731 -fregs-graph
1733 Use the graph colouring register allocator for register alloca‐
1734 tion in the native code generator.
1735 -fregs-iterative
1737 Use the iterative coalescing graph colouring register allocator
1738 in the native code generator.
1739 -fsimpl-tick-factor=⟨n⟩
1741 default: 100. Set the percentage factor for simplifier ticks.
1742 -fsimplifier-phases=⟨n⟩
1744 default: 2. Set the number of phases for the simplifier. Ig‐
1745 nored with -O0.
1746 -fsolve-constant-dicts
1748 When solving constraints, try to eagerly solve super classes us‐
1749 ing available dictionaries.
1750 -fspec-constr
1752 Turn on the SpecConstr transformation. Implied by -O2.
1753 -fspec-constr-count=⟨n⟩
1755 default: 3.* Set to ⟨n⟩ the maximum number of specialisations
1756 that will be created for any one function by the SpecConstr
1757 transformation.
1758 -fspec-constr-keen
1760 Specialize a call with an explicit constructor argument, even if
1761 the argument is not scrutinised in the body of the function
1762 -fspec-constr-threshold=⟨n⟩
1764 default: 2000. Set the size threshold for the SpecConstr trans‐
1765 formation to ⟨n⟩.
1766 -fspecialise
1768 Turn on specialisation of overloaded functions. Implied by -O.
1769 -fspecialise-aggressively
1771 Turn on specialisation of overloaded functions regardless of
1772 size, if unfolding is available
1773 -fstatic-argument-transformation
1775 Turn on the static argument transformation.
1776 -fstg-cse
1778 Enable common sub-expression elimination on the STG intermediate
1779 language
1780 -fstg-lift-lams
1782 Enable late lambda lifting on the STG intermediate language. Im‐
1783 plied by -O2.
1784 -fstg-lift-lams-known
1786 Allow turning known into unknown calls while performing late
1787 lambda lifting.
1788 -fstg-lift-lams-non-rec-args
1790 Create top-level non-recursive functions with at most <n> param‐
1791 eters while performing late lambda lifting.
1792 -fstg-lift-lams-rec-args
1794 Create top-level recursive functions with at most <n> parameters
1795 while performing late lambda lifting.
1796 -fstrictness
1798 Turn on demand analysis. Implied by -O. Implies
1799 -fworker-wrapper
1800 -fstrictness-before=⟨n⟩
1802 Run an additional demand analysis before simplifier phase ⟨n⟩
1803 -funbox-small-strict-fields
1805 Flatten strict constructor fields with a pointer-sized represen‐
1806 tation. Implied by -O.
1807 -funbox-strict-fields
1809 Flatten strict constructor fields
1810 -funfolding-case-scaling=⟨n⟩
1812 default: 30. Apply a penalty of (inlining_cost * 1/n) for each
1813 level of case nesting.
1814 -funfolding-case-threshold=⟨n⟩
1816 default: 2. Reduce inlining for cases nested deeper than n.
1817 -funfolding-creation-threshold=⟨n⟩
1819 default: 750. Tweak unfolding settings.
1820 -funfolding-dict-discount=⟨n⟩
1822 default: 30. Tweak unfolding settings.
1823 -funfolding-fun-discount=⟨n⟩
1825 default: 60. Tweak unfolding settings.
1826 -funfolding-keeness-factor=⟨n⟩
1828 This has been deprecated in GHC 9.0.1.
1829 -funfolding-use-threshold=⟨n⟩
1831 default: 80. Tweak unfolding settings.
1832 -fworker-wrapper
1834 Enable the worker/wrapper transformation.
1835 Optimization levels
1837 -O Enable level 1 optimisations
1838 -O0 Disable optimisations (default)
1840 -O2 Enable level 2 optimisations
1842 -O⟨n⟩ Any -On where n > 2 is the same as -O2.
1844 Package options
1846 -clear-package-db
1847 Clear the package db stack.
1848 -distrust ⟨pkg⟩
1850 Expose package ⟨pkg⟩ and set it to be distrusted. See Safe
1851 Haskell.
1852 -distrust-all-packages
1854 Distrust all packages by default. See Safe Haskell.
1855 -fpackage-trust
1857 Enable Safe Haskell trusted package requirement for trustworthy
1858 modules.
1859 -global-package-db
1861 Add the global package db to the stack.
1862 -hide-all-packages
1864 Hide all packages by default
1865 -hide-package ⟨pkg⟩
1867 Hide package ⟨pkg⟩
1868 -ignore-package ⟨pkg⟩
1870 Ignore package ⟨pkg⟩
1871 -no-auto-link-packages
1873 Don't automatically link in the base and rts packages.
1874 -no-global-package-db
1876 Remove the global package db from the stack.
1877 -no-user-package-db
1879 Remove the user's package db from the stack.
1880 -package ⟨pkg⟩
1882 Expose package ⟨pkg⟩
1883 -package-db ⟨file⟩
1885 Add ⟨file⟩ to the package db stack.
1886 -package-env ⟨file⟩|⟨name⟩
1888 Use the specified package environment.
1889 -package-id ⟨unit-id⟩
1891 Expose package by id ⟨unit-id⟩
1892 -this-unit-id ⟨unit-id⟩
1894 Compile to be part of unit (i.e. package) ⟨unit-id⟩
1895 -trust ⟨pkg⟩
1897 Expose package ⟨pkg⟩ and set it to be trusted. See Safe Haskell.
1898 -user-package-db
1900 Add the user's package db to the stack.
1901 Phases of compilation
1903 -C Stop after generating C (.hc file)
1904 -c Stop after generating object (.o) file
1906 -E Stop after preprocessing (.hspp file)
1908 -F Enable the use of a pre-processor (set with -pgmF ⟨cmd⟩)
1910 -S Stop after generating assembly (.s file)
1912 -x ⟨suffix⟩
1914 Override default behaviour for source files
1915 Overriding external programs
1917 -pgma ⟨cmd⟩
1918 Use ⟨cmd⟩ as the assembler
1919 -pgmc ⟨cmd⟩
1921 Use ⟨cmd⟩ as the C compiler
1922 -pgmdll ⟨cmd⟩
1924 Use ⟨cmd⟩ as the DLL generator
1925 -pgmF ⟨cmd⟩
1927 Use ⟨cmd⟩ as the pre-processor (with -F only)
1928 -pgmi ⟨cmd⟩
1930 Use ⟨cmd⟩ as the external interpreter command.
1931 -pgminstall_name_tool ⟨cmd⟩
1933 Use ⟨cmd⟩ as the program to inject runpath into mach-o dylibs on
1934 macOS
1935 -pgmL ⟨cmd⟩
1937 Use ⟨cmd⟩ as the literate pre-processor
1938 -pgml ⟨cmd⟩
1940 Use ⟨cmd⟩ as the linker
1941 -pgmlc ⟨cmd⟩
1943 Use ⟨cmd⟩ as the LLVM compiler
1944 -pgmlibtool ⟨cmd⟩
1946 Use ⟨cmd⟩ as the command for libtool (with -staticlib only).
1947 -pgmlm ⟨cmd⟩
1949 Use ⟨cmd⟩ as the linker when merging object files
1950 -pgmlo ⟨cmd⟩
1952 Use ⟨cmd⟩ as the LLVM optimiser
1953 -pgmotool ⟨cmd⟩
1955 Use ⟨cmd⟩ as the program to inspect mach-o dylibs on macOS
1956 -pgmP ⟨cmd⟩
1958 Use ⟨cmd⟩ as the C pre-processor (with -cpp only)
1959 -pgms ⟨cmd⟩
1961 Use ⟨cmd⟩ as the splitter
1962 -pgmwindres ⟨cmd⟩
1964 Use ⟨cmd⟩ as the program for embedding manifests on Windows.
1965 Phase-specific options
1967 -opta ⟨option⟩
1968 pass ⟨option⟩ to the assembler
1969 -optc ⟨option⟩
1971 pass ⟨option⟩ to the C compiler
1972 -optcxx ⟨option⟩
1974 pass ⟨option⟩ to the C++ compiler
1975 -optdll ⟨option⟩
1977 pass ⟨option⟩ to the DLL generator
1978 -optF ⟨option⟩
1980 pass ⟨option⟩ to the custom pre-processor
1981 -opti ⟨option⟩
1983 pass ⟨option⟩ to the interpreter sub-process.
1984 -optL ⟨option⟩
1986 pass ⟨option⟩ to the literate pre-processor
1987 -optl ⟨option⟩
1989 pass ⟨option⟩ to the linker
1990 -optlc ⟨option⟩
1992 pass ⟨option⟩ to the LLVM compiler
1993 -optlm ⟨option⟩
1995 pass ⟨option⟩ to the linker when merging object files.
1996 -optlo ⟨option⟩
1998 pass ⟨option⟩ to the LLVM optimiser
1999 -optP ⟨option⟩
2001 pass ⟨option⟩ to cpp (with -cpp only)
2002 -optwindres ⟨option⟩
2004 pass ⟨option⟩ to windres.
2005 -pgmc-supports-no-pie
2007 Indicate that the C compiler supports -no-pie
2008 Platform-specific options
2010 -mavx (x86 only) Enable support for AVX SIMD extensions
2011 -mavx2 (x86 only) Enable support for AVX2 SIMD extensions
2013 -mavx512cd
2015 (x86 only) Enable support for AVX512-CD SIMD extensions
2016 -mavx512er
2018 (x86 only) Enable support for AVX512-ER SIMD extensions
2019 -mavx512f
2021 (x86 only) Enable support for AVX512-F SIMD extensions
2022 -mavx512pf
2024 (x86 only) Enable support for AVX512-PF SIMD extensions
2025 -mbmi (x86 only) Use BMI1 for bit manipulation operations
2027 -mbmi2 (x86 only) Use BMI2 for bit manipulation operations
2029 -msse (x86 only) Use SSE for floating-point operations
2031 -msse2 (x86 only) Use SSE2 for floating-point operations
2033 -msse3 (x86 only) Use SSE3 for floating-point operations
2035 -msse4 (x86 only) Use SSE4 for floating-point operations
2037 -msse4.2
2039 (x86 only) Use SSE4.2 for floating-point operations
2040 Compiler plugins
2042 -fclear-plugins
2043 Clear the list of active plugins
2044 -fplugin-opt=⟨module⟩:⟨args⟩
2046 Give arguments to a plugin module; module must be specified with
2047 -fplugin=⟨module⟩
2048 -fplugin-trustworthy
2050 Trust the used plugins and no longer mark the compiled module as
2051 unsafe
2052 -fplugin=⟨module⟩
2054 Load a plugin exported by a given module
2055 -hide-all-plugin-packages
2057 Hide all packages for plugins by default
2058 -plugin-package ⟨pkg⟩
2060 Expose ⟨pkg⟩ for plugins
2061 -plugin-package-id ⟨pkg-id⟩
2063 Expose ⟨pkg-id⟩ for plugins
2064 Profiling
2066 -auto (deprecated) Alias for -fprof-auto-exported
2067 -auto-all
2069 (deprecated) Alias for -fprof-auto
2070 -caf-all
2072 (deprecated) Alias for -fprof-cafs
2073 -fno-prof-count-entries
2075 Do not collect entry counts
2076 -fprof-auto
2078 Auto-add SCC\ s to all bindings not marked INLINE
2079 -fprof-auto-calls
2081 Auto-add SCC\ s to all call sites
2082 -fprof-auto-exported
2084 Auto-add SCC\ s to all exported bindings not marked INLINE
2085 -fprof-auto-top
2087 Auto-add SCC\ s to all top-level bindings not marked INLINE
2088 -fprof-cafs
2090 Auto-add SCC\ s to all CAFs
2091 -fprof-callers=⟨name⟩
2093 Auto-add SCC\ s to all call-sites of the named function.
2094 -no-auto
2096 (deprecated) Alias for -fno-prof-auto
2097 -no-auto-all
2099 (deprecated) Alias for -fno-prof-auto
2100 -no-caf-all
2102 (deprecated) Alias for -fno-prof-cafs
2103 -prof Turn on profiling
2105 -ticky Turn on ticky-ticky profiling
2107 -ticky-allocd
2109 Track the number of times each closure type is allocated.
2110 -ticky-dyn-thunk
2112 Track allocations of dynamic thunks
2113 Program coverage
2115 -fhpc Turn on Haskell program coverage instrumentation
2116 Recompilation checking
2118 -fforce-recomp
2119 Turn off recompilation checking. This is implied by any -ddump-X
2120 option when compiling a single file (i.e. when using -c).
2121 -fignore-hpc-changes
2123 Do not recompile modules just to match changes to HPC flags.
2124 This is especially useful for avoiding recompilation when using
2125 GHCi, and is enabled by default for GHCi.
2126 -fignore-optim-changes
2128 Do not recompile modules just to match changes to optimisation
2129 flags. This is especially useful for avoiding recompilation when
2130 using GHCi, and is enabled by default for GHCi.
2131 Redirecting output
2133 --exclude-module=⟨file⟩
2134 Regard ⟨file⟩ as "stable"; i.e., exclude it from having depen‐
2135 dencies on it.
2136 -ddump-mod-cycles
2138 Dump module cycles
2139 -dep-makefile ⟨file⟩
2141 Use ⟨file⟩ as the makefile
2142 -dep-suffix ⟨suffix⟩
2144 Make dependencies that declare that files with suffix
2145 .⟨suf⟩⟨osuf⟩ depend on interface files with suffix .⟨suf⟩hi
2146 -dumpdir ⟨dir⟩
2148 redirect dump files
2149 -dynhisuf ⟨suffix⟩
2151 set the suffix to use for dynamic interface files
2152 -dyno ⟨file⟩
2154 set dynamic output filename
2155 -dynohi ⟨file⟩
2157 set the filename in which to put the dynamic interface
2158 -dynosuf ⟨suffix⟩
2160 set the dynamic output file suffix
2161 -hcsuf ⟨suffix⟩
2163 set the suffix to use for intermediate C files
2164 -hidir ⟨dir⟩
2166 set directory for interface files
2167 -hiedir ⟨dir⟩
2169 set directory for extended interface files
2170 -hiesuf ⟨suffix⟩
2172 set the suffix to use for extended interface files
2173 -hisuf ⟨suffix⟩
2175 set the suffix to use for interface files
2176 -include-cpp-deps
2178 Include preprocessor dependencies
2179 -include-pkg-deps
2181 Regard modules imported from packages as unstable
2182 -o ⟨file⟩
2184 set output filename
2185 -odir ⟨dir⟩
2187 set directory for object files
2188 -ohi ⟨file⟩
2190 set the filename in which to put the interface
2191 -osuf ⟨suffix⟩
2193 set the output file suffix
2194 -outputdir ⟨dir⟩
2196 set output directory
2197 -stubdir ⟨dir⟩
2199 redirect FFI stub files
2200 Temporary files
2202 -tmpdir ⟨dir⟩
2203 set the directory for temporary files
2204 Verbosity options
2206 -fabstract-refinement-hole-fits
2207 default: off. Toggles whether refinements where one or more of
2208 the holes are abstract are reported.
2209 -fdefer-diagnostics
2211 Defer and group diagnostic messages by severity
2212 -fdiagnostics-color=⟨always|auto|never⟩
2214 Use colors in error messages
2215 -fdiagnostics-show-caret
2217 Whether to show snippets of original source code
2218 -ferror-spans
2220 Output full span in error messages
2221 -fhide-source-paths
2223 hide module source and object paths
2224 -fkeep-going
2226 Continue compilation as far as possible on errors
2227 -fmax-refinement-hole-fits=⟨n⟩
2229 default: 6. Set the maximum number of refinement hole fits for
2230 typed holes to display in type error messages.
2231 -fmax-relevant-binds=⟨n⟩
2233 default: 6. Set the maximum number of bindings to display in
2234 type error messages.
2235 -fmax-valid-hole-fits=⟨n⟩
2237 default: 6. Set the maximum number of valid hole fits for typed
2238 holes to display in type error messages.
2239 -fno-show-valid-hole-fits
2241 Disables showing a list of valid hole fits for typed holes in
2242 type error messages.
2243 -fno-sort-valid-hole-fits
2245 Disables the sorting of the list of valid hole fits for typed
2246 holes in type error messages.
2247 -fprint-axiom-incomps
2249 Display equation incompatibilities in closed type families
2250 -fprint-equality-relations
2252 Distinguish between equality relations when printing
2253 -fprint-expanded-synonyms
2255 In type errors, also print type-synonym-expanded types.
2256 -fprint-explicit-coercions
2258 Print coercions in types
2259 -fprint-explicit-foralls
2261 Print explicit forall quantification in types. See also
2262 ExplicitForAll
2263 -fprint-explicit-kinds
2265 Print explicit kind foralls and kind arguments in types. See
2266 also KindSignatures
2267 -fprint-explicit-runtime-reps
2269 Print RuntimeRep variables in types which are runtime-represen‐
2270 tation polymorphic.
2271 -fprint-potential-instances
2273 display all available instances in type error messages
2274 -fprint-typechecker-elaboration
2276 Print extra information from typechecker.
2277 -fprint-unicode-syntax
2279 Use unicode syntax when printing expressions, types and kinds.
2280 See also UnicodeSyntax
2281 -frefinement-level-hole-fits=⟨n⟩
2283 default: off. Sets the level of refinement of the refinement
2284 hole fits, where level n means that hole fits of up to n holes
2285 will be considered.
2286 -freverse-errors
2288 Output errors in reverse order
2289 -fshow-docs-of-hole-fits
2291 Toggles whether to show the documentation of the valid hole fits
2292 in the output.
2293 -fshow-hole-constraints
2295 Show constraints when reporting typed holes.
2296 -fshow-hole-matches-of-hole-fits
2298 Toggles whether to show the type of the additional holes in re‐
2299 finement hole fits.
2300 -fshow-provenance-of-hole-fits
2302 Toggles whether to show the provenance of the valid hole fits in
2303 the output.
2304 -fshow-type-app-of-hole-fits
2306 Toggles whether to show the type application of the valid hole
2307 fits in the output.
2308 -fshow-type-app-vars-of-hole-fits
2310 Toggles whether to show what type each quantified variable takes
2311 in a valid hole fit.
2312 -fshow-type-of-hole-fits
2314 Toggles whether to show the type of the valid hole fits in the
2315 output.
2316 -fsort-by-size-hole-fits
2318 Sort valid hole fits by size.
2319 -fsort-by-subsumption-hole-fits
2321 Sort valid hole fits by subsumption.
2322 -funclutter-valid-hole-fits
2324 Unclutter the list of valid hole fits by not showing provenance
2325 nor type applications of suggestions.
2326 -Rghc-timing
2328 Summarise timing stats for GHC (same as +RTS -tstderr).
2329 -v verbose mode (equivalent to -v3)
2331 -v⟨n⟩ set verbosity level
2333 Warnings
2335 -fdefer-out-of-scope-variables
2336 Convert variable out of scope variables errors into warnings.
2337 Implied by -fdefer-type-errors. See also
2338 -Wdeferred-out-of-scope-variables.
2339 -fdefer-type-errors
2341 Turn type errors into warnings, deferring the error until run‐
2342 time. Implies -fdefer-typed-holes and
2343 -fdefer-out-of-scope-variables. See also -Wdeferred-type-errors
2344 -fdefer-typed-holes
2346 Convert typed hole errors into warnings, deferring the error un‐
2347 til runtime. Implied by -fdefer-type-errors. See also
2348 -Wtyped-holes.
2349 -fenable-th-splice-warnings
2351 Generate warnings for Template Haskell splices
2352 -fhelpful-errors
2354 Make suggestions for mis-spelled names.
2355 -fmax-pmcheck-models=⟨n⟩
2357 soft limit on the number of parallel models the pattern match
2358 checker should check a pattern match clause against
2359 -fshow-warning-groups
2361 show which group an emitted warning belongs to.
2362 -fvia-C
2364 use the C code generator
2365 -W enable normal warnings
2367 -w disable all warnings
2369 -Wall enable almost all warnings (details in Warnings and san‐
2371 ity-checking)
2372 -Wall-missed-specialisations
2374 warn when specialisation of any overloaded function fails.
2375 -Wall-missed-specializations
2377 alias for -Wall-missed-specialisations
2378 -Wambiguous-fields
2380 warn about ambiguous field selectors or updates
2381 -Wauto-orphans
2383 (deprecated) Does nothing
2384 -Wcompat
2386 enable future compatibility warnings (details in Warnings and
2387 sanity-checking)
2388 -Wcompat-unqualified-imports
2390 Report unqualified imports of core libraries which are expected
2391 to cause compatibility problems in future releases.
2392 -Wcpp-undef
2394 warn on uses of the #if directive on undefined identifiers
2395 -Wdefault
2397 enable default flags
2398 -Wdeferred-out-of-scope-variables
2400 Report warnings when variable out-of-scope errors are deferred
2401 until runtime. See -fdefer-out-of-scope-variables.
2402 -Wdeferred-type-errors
2404 Report warnings when deferred type errors are enabled. This op‐
2405 tion is enabled by default. See -fdefer-type-errors.
2406 -Wdeprecated-flags
2408 warn about uses of commandline flags that are deprecated
2409 -Wdeprecations
2411 warn about uses of functions & types that have warnings or dep‐
2412 recated pragmas. Alias for -Wwarnings-deprecations
2413 -Wderiving-defaults
2415 warn about default deriving when using both DeriveAnyClass and
2416 GeneralizedNewtypeDeriving
2417 -Wderiving-typeable
2419 warn when Typeable is derived
2420 -Wdodgy-exports
2422 warn about dodgy exports
2423 -Wdodgy-foreign-imports
2425 warn about dodgy foreign imports
2426 -Wdodgy-imports
2428 warn about dodgy imports
2429 -Wduplicate-constraints
2431 warn when a constraint appears duplicated in a type signature
2432 -Wduplicate-exports
2434 warn when an entity is exported multiple times
2435 -Wempty-enumerations
2437 warn about enumerations that are empty
2438 -Werror
2440 make warnings fatal
2441 -Weverything
2443 enable all warnings supported by GHC
2444 -Wextra
2446 alias for -W
2447 -Whi-shadowing
2449 (deprecated) warn when a .hi file in the current directory shad‐
2450 ows a library
2451 -Widentities
2453 warn about uses of Prelude numeric conversions that are probably
2454 the identity (and hence could be omitted)
2455 -Wimplicit-kind-vars
2457 warn when kind variables are implicitly quantified over.
2458 -Wimplicit-lift
2460 warn about implicit lift in Template Haskell quotes
2461 -Wimplicit-prelude
2463 warn when the Prelude is implicitly imported
2464 -Winaccessible-code
2466 warn about inaccessible code
2467 -Wincomplete-patterns
2469 warn when a pattern match could fail
2470 -Wincomplete-record-updates
2472 warn when a record update could fail
2473 -Wincomplete-uni-patterns
2475 warn when a pattern match in a lambda expression, pattern bind‐
2476 ing or a lazy pattern could fail
2477 -Winferred-safe-imports
2479 warn when an explicitly Safe Haskell module imports a Safe-In‐
2480 ferred one
2481 -Winline-rule-shadowing
2483 Warn if a rewrite RULE might fail to fire because the function
2484 might be inlined before the rule has a chance to fire. See How
2485 rules interact with INLINE/NOINLINE pragmas.
2486 -Winvalid-haddock
2488 warn when a Haddock comment occurs in an invalid position
2489 -Wmissed-extra-shared-lib
2491 Warn when GHCi can't load a shared lib.
2492 -Wmissed-specialisations
2494 warn when specialisation of an imported, overloaded function
2495 fails.
2496 -Wmissed-specializations
2498 alias for -Wmissed-specialisations
2499 -Wmissing-deriving-strategies
2501 warn when a deriving clause is missing a deriving strategy
2502 -Wmissing-export-lists
2504 warn when a module declaration does not explicitly list all ex‐
2505 ports
2506 -Wmissing-exported-signatures
2508 warn about top-level functions without signatures, only if they
2509 are exported
2510 -Wmissing-exported-sigs
2512 (deprecated) warn about top-level functions without signatures,
2513 only if they are exported. takes precedence over -Wmissing-sig‐
2514 natures
2515 -Wmissing-fields
2517 warn when fields of a record are uninitialised
2518 -Wmissing-home-modules
2520 warn when encountering a home module imported, but not listed on
2521 the command line. Useful for cabal to ensure GHC won't pick up
2522 modules, not listed neither in exposed-modules, nor in
2523 other-modules.
2524 -Wmissing-import-lists
2526 warn when an import declaration does not explicitly list all the
2527 names brought into scope
2528 -Wmissing-kind-signatures
2530 warn when type declarations don't have kind signatures nor CUSKs
2531 -Wmissing-local-signatures
2533 warn about polymorphic local bindings without signatures
2534 -Wmissing-local-sigs
2536 (deprecated) warn about polymorphic local bindings without sig‐
2537 natures
2538 -Wmissing-methods
2540 warn when class methods are undefined
2541 -Wmissing-monadfail-instances
2543 Warn when a failable pattern is used in a do-block that does not
2544 have a MonadFail instance.
2545 -Wmissing-pattern-synonym-signatures
2547 warn when pattern synonyms do not have type signatures
2548 -Wmissing-safe-haskell-mode
2550 warn when the Safe Haskell mode is not explicitly specified.
2551 -Wmissing-signatures
2553 warn about top-level functions without signatures
2554 -Wmissing-space-after-bang
2556 (deprecated) Does nothing
2557 -Wmonomorphism-restriction
2559 warn when the Monomorphism Restriction is applied
2560 -Wname-shadowing
2562 warn when names are shadowed
2563 -Wno-compat
2565 Disables all warnings enabled by -Wcompat.
2566 -Wnoncanonical-monad-instances
2568 warn when Applicative or Monad instances have noncanonical defi‐
2569 nitions of return, pure, (>>), or (*>). See flag description in
2570 Warnings and sanity-checking for more details.
2571 -Wnoncanonical-monadfail-instances
2573 (deprecated) warn when Monad or MonadFail instances have non‐
2574 canonical definitions of fail.
2575 -Wnoncanonical-monoid-instances
2577 warn when Semigroup or Monoid instances have noncanonical defi‐
2578 nitions of (<>) or mappend. See flag description in Warnings
2579 and sanity-checking for more details.
2580 -Wnot (deprecated) Alias for -w
2582 -Woperator-whitespace
2584 warn on prefix, suffix, and tight infix uses of infix operators
2585 -Woperator-whitespace-ext-conflict
2587 warn on uses of infix operators that would be parsed differently
2588 were a particular GHC extension enabled
2589 -Worphans
2591 warn when the module contains orphan instance declarations or
2592 rewrite rules
2593 -Woverflowed-literals
2595 warn about literals that will overflow their type
2596 -Woverlapping-patterns
2598 warn about overlapping patterns
2599 -Wpartial-fields
2601 warn when defining a partial record field.
2602 -Wpartial-type-signatures
2604 warn about holes in partial type signatures when
2605 PartialTypeSignatures is enabled. Not applicable when
2606 PartialTypeSignatures is not enabled, in which case errors are
2607 generated for such holes.
2608 -Wprepositive-qualified-module
2610 Report imports with a leading/prepositive "qualified"
2611 -Wredundant-bang-patterns
2613 Warn about redundant bang patterns.
2614 -Wredundant-constraints
2616 Have the compiler warn about redundant constraints in type sig‐
2617 natures.
2618 -Wredundant-record-wildcards
2620 Warn about record wildcard matches when the wildcard binds no
2621 patterns.
2622 -Wsafe warn if the module being compiled is regarded to be safe.
2624 -Wsemigroup
2626 warn when a Monoid is not Semigroup, and on non- Semigroup defi‐
2627 nitions of (<>)?
2628 -Wsimplifiable-class-constraints
2630 Warn about class constraints in a type signature that can be
2631 simplified using a top-level instance declaration.
2632 -Wstar-binder
2634 warn about binding the (*) type operator despite StarIsType
2635 -Wstar-is-type
2637 warn when * is used to mean Data.Kind.Type
2638 -Wtabs warn if there are tabs in the source file
2640 -Wtrustworthy-safe
2642 warn if the module being compiled is marked as Trustworthy but
2643 it could instead be marked as Safe, a more informative bound.
2644 -Wtype-defaults
2646 warn when defaulting happens
2647 -Wtyped-holes
2649 Report warnings when typed hole errors are deferred until run‐
2650 time. See -fdefer-typed-holes.
2651 -Wunbanged-strict-patterns
2653 warn on pattern bind of unlifted variable that is neither bare
2654 nor banged
2655 -Wunicode-bidirectional-format-characters
2657 warn about the usage of unicode bidirectional layout override
2658 characters
2659 -Wunrecognised-pragmas
2661 warn about uses of pragmas that GHC doesn't recognise
2662 -Wunrecognised-warning-flags
2664 throw a warning when an unrecognised -W... flag is encountered
2665 on the command line.
2666 -Wunsafe
2668 warn if the module being compiled is regarded to be unsafe. See
2669 Safe Haskell
2670 -Wunsupported-calling-conventions
2672 warn about use of an unsupported calling convention
2673 -Wunsupported-llvm-version
2675 Warn when using -fllvm with an unsupported version of LLVM.
2676 -Wunticked-promoted-constructors
2678 warn if promoted constructors are not ticked
2679 -Wunused-binds
2681 warn about bindings that are unused. Alias for
2682 -Wunused-top-binds, -Wunused-local-binds and
2683 -Wunused-pattern-binds
2684 -Wunused-do-bind
2686 warn about do bindings that appear to throw away values of types
2687 other than ()
2688 -Wunused-foralls
2690 warn about type variables in user-written forall\s that are un‐
2691 used
2692 -Wunused-imports
2694 warn about unnecessary imports
2695 -Wunused-local-binds
2697 warn about local bindings that are unused
2698 -Wunused-matches
2700 warn about variables in patterns that aren't used
2701 -Wunused-packages
2703 warn when package is requested on command line, but was never
2704 loaded.
2705 -Wunused-pattern-binds
2707 warn about pattern match bindings that are unused
2708 -Wunused-record-wildcards
2710 Warn about record wildcard matches when none of the bound vari‐
2711 ables are used.
2712 -Wunused-top-binds
2714 warn about top-level bindings that are unused
2715 -Wunused-type-patterns
2717 warn about unused type variables which arise from patterns in in
2718 type family and data family instances
2719 -Wwarn make warnings non-fatal
2721 -Wwarnings-deprecations
2723 warn about uses of functions & types that have warnings or dep‐
2724 recated pragmas
2725 -Wwrong-do-bind
2727 warn about do bindings that appear to throw away monadic values
2728 that you should have bound instead
2729
2731 Copyright 2015. The University Court of the University of Glasgow. All
2732 rights reserved.
2733
2735 https://www.haskell.org/ghc the GHC homepage
2736
2738 The GHC Team
2739
2741 2023, GHC Team
27429.2.6 Jul 25, 2023 GHC(1)