1GHC(1) Glasgow Haskell Compiler GHC(1)
2
6 ghc - the Glasgow Haskell Compiler
7
9 ghc [option|filename]
10 ghci [option|filename]
11
13 This manual page documents briefly the ghc and ghci commands. Note that
14 ghci is not yet available on all architectures. Extensive documentation
15 is available in various other formats including PDF and HTML; see
16 below.
17 Each of GHC's command line options is classified as either static or
19 dynamic. A static flag may only be specified on the command line,
20 whereas a dynamic flag may also be given in an OPTIONS pragma in a
21 source file or set from the GHCi command-line with :set .
22 As a rule of thumb, all the language options are dynamic, as are the
24 warning options and the debugging options.
25 The rest are static, with the notable exceptions of -v, -cpp, -fasm,
27 -fvia-C, -fllvm, and -#include. The OPTIONS sections lists the status
28 of each flag.
29 Common suffixes of file names for Haskell are:
31 .hs Haskell source code; preprocess, compile
33 .lhs literate Haskell source; unlit, preprocess, compile
35 .hi Interface file; contains information about exported symbols
37 .hc intermediate C files
39 .⟨way⟩_o
41 object files for "way" ⟨way⟩; common ways are:
42 dyn dynamically-linked
44 p built with profiling
46 .⟨way⟩_hi
48 interface files for "way" ⟨way⟩; common ways are:
49
51 Code generation
52 -dynamic-too -fasm -fbyte-code -fexternal-dynamic-refs -fllvm
53 -fno-code -fobject-code -fPIC -fPIE -fwrite-interface
54 Debugging the compiler
56 -dcmm-lint -dcore-lint -ddump-asm -ddump-asm-expanded
57 -ddump-asm-liveness -ddump-asm-native -ddump-asm-regalloc
58 -ddump-asm-regalloc-stages -ddump-asm-stats -ddump-bcos
59 -ddump-cmm -ddump-cmm-caf -ddump-cmm-cbe -ddump-cmm-cfg
60 -ddump-cmm-cps -ddump-cmm-from-stg -ddump-cmm-info
61 -ddump-cmm-proc -ddump-cmm-procmap -ddump-cmm-raw
62 -ddump-cmm-sink -ddump-cmm-sp -ddump-cmm-split -ddump-cmm-switch
63 -ddump-cmm-verbose -ddump-core-stats -ddump-cse -ddump-deriv
64 -ddump-ds -ddump-ds-preopt -ddump-ec-trace -ddump-foreign
65 -ddump-if-trace -ddump-inlinings -ddump-json -ddump-llvm
66 -ddump-occur-anal -ddump-opt-cmm -ddump-parsed -ddump-parsed-ast
67 -ddump-prep -ddump-rn -ddump-rn-ast -ddump-rn-stats
68 -ddump-rn-trace -ddump-rule-firings -ddump-rule-rewrites
69 -ddump-rules -ddump-simpl -ddump-simpl-iterations
70 -ddump-simpl-stats -ddump-spec -ddump-splices -ddump-stg
71 -ddump-str-signatures -ddump-stranal -ddump-tc -ddump-tc-ast
72 -ddump-tc-trace -ddump-timings -ddump-to-file -ddump-types
73 -ddump-worker-wrapper -dfaststring-stats -dhex-word-literals
74 -dinitial-unique=⟨s⟩ -dinline-check=⟨str⟩ -dno-debug-output
75 -dppr-case-as-let -dppr-cols=⟨n⟩ -dppr-debug -dppr-user-length
76 -drule-check=⟨str⟩ -dshow-passes -dstg-lint -dsuppress-all
77 -dsuppress-coercions -dsuppress-idinfo -dsuppress-module-pre‐
78 fixes -dsuppress-stg-free-vars -dsuppress-ticks -dsuppress-time‐
79 stamps -dsuppress-type-applications -dsuppress-type-signatures
80 -dsuppress-unfoldings -dsuppress-uniques -dsuppress-var-kinds
81 -dth-dec-file -dunique-increment=⟨i⟩ -dverbose-core2core -dver‐
82 bose-stg2stg -falignment-sanitisation -fcatch-bottoms
83 -fllvm-fill-undef-with-garbage -fproc-alignment -g -g⟨n⟩
84 C pre-processor
86 -cpp -D⟨symbol⟩[=⟨value⟩] -I⟨dir⟩ -U⟨symbol⟩
87 Finding imports
89 -i -i⟨dir⟩[:⟨dir⟩]*
90 Interactive mode
92 -fbreak-on-error -fbreak-on-exception -fghci-hist-size=⟨n⟩
93 -fghci-leak-check -flocal-ghci-history -fno-it
94 -fprint-bind-result -fshow-loaded-modules -ghci-script
95 -ignore-dot-ghci -interactive-print ⟨expr⟩
96 Interface files
98 --show-iface ⟨file⟩ -ddump-hi -ddump-hi-diffs -ddump-mini‐
99 mal-imports
100 Keeping intermediate files
102 -keep-hc-file -keep-hc-files -keep-hi-files -keep-llvm-file
103 -keep-llvm-files -keep-o-files -keep-s-file -keep-s-files
104 -keep-tmp-files
105 Language options
107 -fsort-by-size-hole-fits -fsort-by-subsumption-hole-fits -XAl‐
108 lowAmbiguousTypes -XApplicativeDo -XArrows -XBangPatterns -XBi‐
109 naryLiterals -XBlockArguments -XCApiFFI -XConstrainedClassMeth‐
110 ods -XConstraintKinds -XCPP -XDataKinds -XDatatypeContexts -XDe‐
111 faultSignatures -XDeriveAnyClass -XDeriveDataTypeable -XDerive‐
112 Foldable -XDeriveFunctor -XDeriveGeneric -XDeriveLift -XDerive‐
113 Traversable -XDerivingStrategies -XDerivingVia -XDisambiguateRe‐
114 cordFields -XDuplicateRecordFields -XEmptyCase -XEmptyDataDecls
115 -XEmptyDataDeriving -XExistentialQuantification -XExplicitForAll
116 -XExplicitNamespaces -XExtendedDefaultRules -XFlexibleContexts
117 -XFlexibleInstances -XForeignFunctionInterface -XFunctionalDe‐
118 pendencies -XGADTs -XGADTSyntax -XGeneralisedNewtypeDeriving
119 -XGeneralizedNewtypeDeriving -XHexFloatLiterals -XImplicitParams
120 -XImpredicativeTypes -XIncoherentInstances -XInstanceSigs -XIn‐
121 terruptibleFFI -XKindSignatures -XLambdaCase -XLiberalTypeSyn‐
122 onyms -XMagicHash -XMonadComprehensions -XMonadFailDesugaring
123 -XMonoLocalBinds -XMultiParamTypeClasses -XMultiWayIf -XNamed‐
124 FieldPuns -XNamedWildCards -XNegativeLiterals -XNoImplicitPre‐
125 lude -XNoMonomorphismRestriction -XNoPatternGuards -XNoTradi‐
126 tionalRecordSyntax -XNPlusKPatterns -XNullaryTypeClasses
127 -XNumDecimals -XNumericUnderscores -XOverlappingInstances
128 -XOverloadedLabels -XOverloadedLists -XOverloadedStrings -XPack‐
129 ageImports -XParallelListComp -XPartialTypeSignatures -XPattern‐
130 Synonyms -XPolyKinds -XPostfixOperators -XQuantifiedConstraints
131 -XQuasiQuotes -XRank2Types -XRankNTypes -XRebindableSyntax
132 -XRecordWildCards -XRecursiveDo -XRoleAnnotations -XSafe
133 -XScopedTypeVariables -XStandaloneDeriving -XStarIsType -XStat‐
134 icPointers -XStrict -XStrictData -XTemplateHaskell -XTemplate‐
135 HaskellQuotes -XTransformListComp -XTrustworthy -XTupleSections
136 -XTypeApplications -XTypeFamilies -XTypeFamilyDependencies
137 -XTypeInType -XTypeOperators -XTypeSynonymInstances -XUnboxed‐
138 Sums -XUnboxedTuples -XUndecidableInstances -XUndecidableSuper‐
139 Classes -XUnicodeSyntax -XUnsafe -XViewPatterns
140 Linking options
142 -c -debug -dylib-install-name ⟨path⟩ -dynamic -dynload -eventlog
143 -fno-embed-manifest -fno-gen-manifest -fno-shared-implib -frame‐
144 work ⟨name⟩ -framework-path ⟨dir⟩ -fwhole-archive-hs-libs -L
145 ⟨dir⟩ -l ⟨lib⟩ -main-is ⟨thing⟩ -no-hs-main -no-rtsopts-sugges‐
146 tions -package ⟨name⟩ -pie -rdynamic
147 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩] -shared -split-objs
148 -split-sections -static -staticlib -threaded
149 -with-rtsopts=⟨opts⟩
150 Miscellaneous options
152 -fexternal-interpreter -fglasgow-exts -ghcversion-file ⟨path to
153 ghcversion.h⟩ -H ⟨size⟩ -j[⟨n⟩]
154 Modes of operation
156 --frontend ⟨module⟩ --help -? --info --interactive --make
157 --mk-dll --numeric-version --print-libdir --show-iface ⟨file⟩
158 --show-options --supported-extensions --supported-languages
159 --version -V -e ⟨expr⟩ -M
160 Individual optimizations
162 -fasm-shortcutting -fcall-arity -fcase-folding -fcase-merge
163 -fcmm-elim-common-blocks -fcmm-sink -fcpr-anal -fcross-mod‐
164 ule-specialise -fcse -fdicts-cheap -fdicts-strict
165 -fdmd-tx-dict-sel -fdo-eta-reduction -fdo-lambda-eta-expansion
166 -feager-blackholing -fenable-rewrite-rules -fexcess-precision
167 -fexitification -fexpose-all-unfoldings -ffloat-in -ffull-lazi‐
168 ness -ffun-to-thunk -fignore-asserts -fignore-interface-pragmas
169 -flate-dmd-anal -flate-specialise -fliberate-case -fliber‐
170 ate-case-threshold=⟨n⟩ -fllvm-pass-vectors-in-regs -floopifica‐
171 tion -fmax-inline-alloc-size=⟨n⟩ -fmax-inline-memcpy-insns=⟨n⟩
172 -fmax-inline-memset-insns=⟨n⟩ -fmax-simplifier-iterations=⟨n⟩
173 -fmax-uncovered-patterns=⟨n⟩ -fmax-worker-args=⟨n⟩
174 -fno-opt-coercion -fno-pre-inlining -fno-state-hack
175 -fomit-interface-pragmas -fomit-yields -foptimal-applicative-do
176 -fpedantic-bottoms -fregs-graph -fregs-iterative
177 -fsimpl-tick-factor=⟨n⟩ -fsimplifier-phases=⟨n⟩ -fsolve-con‐
178 stant-dicts -fspec-constr -fspec-constr-count=⟨n⟩ -fspec-con‐
179 str-keen -fspec-constr-threshold=⟨n⟩ -fspecialise -fspe‐
180 cialise-aggressively -fstatic-argument-transformation -fstg-cse
181 -fstrictness -fstrictness-before=⟨n⟩ -funbox-small-strict-fields
182 -funbox-strict-fields -funfolding-creation-threshold=⟨n⟩ -fun‐
183 folding-dict-discount=⟨n⟩ -funfolding-fun-discount=⟨n⟩ -funfold‐
184 ing-keeness-factor=⟨n⟩ -funfolding-use-threshold=⟨n⟩
185 Optimization levels
187 -O -O1 -O0 -O2
188 Package options
190 -clear-package-db -distrust ⟨pkg⟩ -distrust-all-packages -fpack‐
191 age-trust -global-package-db -hide-all-packages -hide-package
192 ⟨pkg⟩ -ignore-package ⟨pkg⟩ -no-auto-link-packages
193 -no-global-package-db -no-user-package-db -package ⟨pkg⟩ -pack‐
194 age-db ⟨file⟩ -package-env ⟨file⟩|⟨name⟩ -package-id ⟨unit-id⟩
195 -this-unit-id ⟨unit-id⟩ -trust ⟨pkg⟩ -user-package-db
196 Phases of compilation
198 -C -c -E -F -S -x ⟨suffix⟩
199 Overriding external programs
201 -pgma ⟨cmd⟩ -pgmc ⟨cmd⟩ -pgmdll ⟨cmd⟩ -pgmF ⟨cmd⟩ -pgmi ⟨cmd⟩
202 -pgmL ⟨cmd⟩ -pgml ⟨cmd⟩ -pgmlc ⟨cmd⟩ -pgmlibtool ⟨cmd⟩ -pgmlo
203 ⟨cmd⟩ -pgmP ⟨cmd⟩ -pgms ⟨cmd⟩ -pgmwindres ⟨cmd⟩
204 Phase-specific options
206 -opta ⟨option⟩ -optc ⟨option⟩ -optdll ⟨option⟩ -optF ⟨option⟩
207 -opti ⟨option⟩ -optL ⟨option⟩ -optl ⟨option⟩ -optlc ⟨option⟩
208 -optlo ⟨option⟩ -optP ⟨option⟩ -optwindres ⟨option⟩
209 Platform-specific options
211 -msse2 -msse4.2
212 Compiler plugins
214 -fplugin-opt=⟨module⟩:⟨args⟩ -fplugin=⟨module⟩ -hide-all-plug‐
215 in-packages -plugin-package ⟨pkg⟩ -plugin-package-id ⟨pkg-id⟩
216 Profiling
218 -fno-prof-auto -fno-prof-cafs -fno-prof-count-entries
219 -fprof-auto -fprof-auto-calls -fprof-auto-exported
220 -fprof-auto-top -fprof-cafs -prof -ticky
221 Program coverage
223 -fhpc
224 Recompilation checking
226 -fforce-recomp -fignore-hpc-changes -fignore-optim-changes
227 Redirecting output
229 --exclude-module=⟨file⟩ -ddump-mod-cycles -dep-makefile ⟨file⟩
230 -dep-suffix ⟨suffix⟩ -dumpdir ⟨dir⟩ -hcsuf ⟨suffix⟩ -hidir ⟨dir⟩
231 -hisuf ⟨suffix⟩ -include-pkg-deps -o ⟨file⟩ -odir ⟨dir⟩ -ohi
232 ⟨file⟩ -osuf ⟨suffix⟩ -outputdir ⟨dir⟩ -stubdir ⟨dir⟩
233 Temporary files
235 -tmpdir ⟨dir⟩
236 Verbosity options
238 -fabstract-refinement-hole-fits -fdiagnos‐
239 tics-color=⟨always|auto|never⟩ -fdiagnostics-show-caret -fer‐
240 ror-spans -fhide-source-paths -fmax-refinement-hole-fits=⟨n⟩
241 -fmax-relevant-binds=⟨n⟩ -fmax-valid-hole-fits=⟨n⟩
242 -fno-show-valid-hole-fits -fno-sort-valid-hole-fits
243 -fprint-equality-relations -fprint-expanded-synonyms
244 -fprint-explicit-coercions -fprint-explicit-foralls
245 -fprint-explicit-kinds -fprint-explicit-runtime-reps
246 -fprint-explicit-runtime-reps -fprint-potential-instances
247 -fprint-typechecker-elaboration -fprint-unicode-syntax -frefine‐
248 ment-level-hole-fits=⟨n⟩ -fshow-hole-constraints
249 -fshow-hole-matches-of-hole-fits -fshow-provenance-of-hole-fits
250 -fshow-type-app-of-hole-fits -fshow-type-app-vars-of-hole-fits
251 -fshow-type-of-hole-fits -funclutter-valid-hole-fits -Rghc-tim‐
252 ing -v -v⟨n⟩
253 Warnings
255 -fdefer-out-of-scope-variables -fdefer-type-errors -fde‐
256 fer-typed-holes -fhelpful-errors -fmax-pmcheck-iterations=⟨n⟩
257 -fshow-warning-groups -W -w -Wall -Wall-missed-specialisations
258 -Wamp -Wcompat -Wcpp-undef -Wdeferred-out-of-scope-variables
259 -Wdeferred-type-errors -Wdeprecated-flags -Wdeprecations
260 -Wdodgy-exports -Wdodgy-foreign-imports -Wdodgy-imports -Wdupli‐
261 cate-constraints -Wduplicate-exports -Wempty-enumerations -Wer‐
262 ror -Weverything -Whi-shadowing -Widentities -Wim‐
263 plicit-kind-vars -Wimplicit-prelude -Winaccessible-code -Wincom‐
264 plete-patterns -Wincomplete-record-updates -Wincomplete-uni-pat‐
265 terns -Winline-rule-shadowing -Wmissed-specialisations -Wmiss‐
266 ing-export-lists -Wmissing-exported-signatures -Wmiss‐
267 ing-exported-sigs -Wmissing-fields -Wmissing-home-modules
268 -Wmissing-import-lists -Wmissing-local-signatures -Wmiss‐
269 ing-local-sigs -Wmissing-methods -Wmissing-monadfail-instances
270 -Wmissing-pattern-synonym-signatures -Wmissing-signatures
271 -Wmonomorphism-restriction -Wname-shadowing -Wno-compat -Wnon‐
272 canonical-monad-instances -Wnoncanonical-monadfail-instances
273 -Wnoncanonical-monoid-instances -Worphans -Woverflowed-literals
274 -Woverlapping-patterns -Wpartial-fields -Wpartial-type-signa‐
275 tures -Wredundant-constraints -Wsafe -Wsemigroup -Wsimplifi‐
276 able-class-constraints -Wstar-binder -Wstar-is-type -Wtabs
277 -Wtrustworthy-safe -Wtype-defaults -Wtyped-holes -Wun‐
278 banged-strict-patterns -Wunrecognised-pragmas -Wunrecog‐
279 nised-warning-flags -Wunsafe -Wunsupported-calling-conventions
280 -Wunsupported-llvm-version -Wunticked-promoted-constructors
281 -Wunused-binds -Wunused-do-bind -Wunused-foralls
282 -Wunused-imports -Wunused-local-binds -Wunused-matches
283 -Wunused-pattern-binds -Wunused-top-binds -Wunused-type-patterns
284 -Wwarn -Wwarnings-deprecations -Wwrong-do-bind
285 Code generation
287 -dynamic-too
288 Build dynamic object files as well as static object files during
289 compilation
290 -fasm Use the native code generator
292 -fbyte-code
294 Generate byte-code
295 -fexternal-dynamic-refs
297 Generate code for linking against dynamic libraries
298 -fllvm Compile using the LLVM code generator
300 -fno-code
302 Omit code generation
303 -fobject-code
305 Generate object code
306 -fPIC Generate position-independent code (where available)
308 -fPIE Generate code for a position-independent executable (where
310 available)
311 -fwrite-interface
313 Always write interface files
314 Debugging the compiler
316 -dcmm-lint
317 C-\- pass sanity checking
318 -dcore-lint
320 Turn on internal sanity checking
321 -ddump-asm
323 Dump final assembly
324 -ddump-asm-expanded
326 Dump the result of the synthetic instruction expansion pass.
327 -ddump-asm-liveness
329 Dump assembly augmented with register liveness
330 -ddump-asm-native
332 Dump initial assembly
333 -ddump-asm-regalloc
335 Dump the result of register allocation
336 -ddump-asm-regalloc-stages
338 Dump the build/spill stages of the -fregs-graph register alloca‐
339 tor.
340 -ddump-asm-stats
342 Dump statistics from the register allocator.
343 -ddump-bcos
345 Dump interpreter byte code
346 -ddump-cmm
348 Dump the final C-\- output
349 -ddump-cmm-caf
351 Dump the results of the C-\- CAF analysis pass.
352 -ddump-cmm-cbe
354 Dump the results of common block elimination
355 -ddump-cmm-cfg
357 Dump the results of the C-\- control flow optimisation pass.
358 -ddump-cmm-cps
360 Dump the results of the CPS pass
361 -ddump-cmm-from-stg
363 Dump STG-to-C-\- output
364 -ddump-cmm-info
366 Dump the results of the C-\- info table augmentation pass.
367 -ddump-cmm-proc
369 Dump the results of proc-point analysis
370 -ddump-cmm-procmap
372 Dump the results of the C-\- proc-point map pass.
373 -ddump-cmm-raw
375 Dump raw C-\-
376 -ddump-cmm-sink
378 Dump the results of the C-\- sinking pass.
379 -ddump-cmm-sp
381 Dump the results of the C-\- stack layout pass.
382 -ddump-cmm-split
384 Dump the results of the C-\- proc-point splitting pass.
385 -ddump-cmm-switch
387 Dump the results of switch lowering passes
388 -ddump-cmm-verbose
390 Show output from each C-\- pipeline pass
391 -ddump-core-stats
393 Print a one-line summary of the size of the Core program at the
394 end of the optimisation pipeline
395 -ddump-cse
397 Dump CSE output
398 -ddump-deriv
400 Dump deriving output
401 -ddump-ds -ddump-ds-preopt
403 Dump desugarer output.
404 -ddump-ec-trace
406 Trace exhaustiveness checker
407 -ddump-foreign
409 Dump foreign export stubs
410 -ddump-if-trace
412 Trace interface files
413 -ddump-inlinings
415 Dump inlining info
416 -ddump-json
418 Dump error messages as JSON documents
419 -ddump-llvm
421 Dump LLVM intermediate code.
422 -ddump-occur-anal
424 Dump occurrence analysis output
425 -ddump-opt-cmm
427 Dump the results of C-\- to C-\- optimising passes
428 -ddump-parsed
430 Dump parse tree
431 -ddump-parsed-ast
433 Dump parser output as a syntax tree
434 -ddump-prep
436 Dump prepared core
437 -ddump-rn
439 Dump renamer output
440 -ddump-rn-ast
442 Dump renamer output as a syntax tree
443 -ddump-rn-stats
445 Renamer stats
446 -ddump-rn-trace
448 Trace renamer
449 -ddump-rule-firings
451 Dump rule firing info
452 -ddump-rule-rewrites
454 Dump detailed rule firing info
455 -ddump-rules
457 Dump rewrite rules
458 -ddump-simpl
460 Dump final simplifier output
461 -ddump-simpl-iterations
463 Dump output from each simplifier iteration
464 -ddump-simpl-stats
466 Dump simplifier stats
467 -ddump-spec
469 Dump specialiser output
470 -ddump-splices
472 Dump TH spliced expressions, and what they evaluate to
473 -ddump-stg
475 Dump final STG
476 -ddump-str-signatures
478 Dump strictness signatures
479 -ddump-stranal
481 Dump strictness analyser output
482 -ddump-tc
484 Dump typechecker output
485 -ddump-tc-ast
487 Dump typechecker output as a syntax tree
488 -ddump-tc-trace
490 Trace typechecker
491 -ddump-timings
493 Dump per-pass timing and allocation statistics
494 -ddump-to-file
496 Dump to files instead of stdout
497 -ddump-types
499 Dump type signatures
500 -ddump-worker-wrapper
502 Dump worker-wrapper output
503 -dfaststring-stats
505 Show statistics for fast string usage when finished
506 -dhex-word-literals
508 Print values of type Word# in hexadecimal.
509 -dinitial-unique=⟨s⟩
511 Start UniqSupply allocation from ⟨s⟩.
512 -dinline-check=⟨str⟩
514 Dump information about inlining decisions
515 -dno-debug-output
517 Suppress unsolicited debugging output
518 -dppr-case-as-let
520 Print single alternative case expressions as strict lets.
521 -dppr-cols=⟨n⟩
523 Set the width of debugging output. For example -dppr-cols200
524 -dppr-debug
526 Turn on debug printing (more verbose)
527 -dppr-user-length
529 Set the depth for printing expressions in error msgs
530 -drule-check=⟨str⟩
532 Dump information about potential rule application
533 -dshow-passes
535 Print out each pass name as it happens
536 -dstg-lint
538 STG pass sanity checking
539 -dsuppress-all
541 In dumps, suppress everything (except for uniques) that is sup‐
542 pressible.
543 -dsuppress-coercions
545 Suppress the printing of coercions in Core dumps to make them
546 shorter
547 -dsuppress-idinfo
549 Suppress extended information about identifiers where they are
550 bound
551 -dsuppress-module-prefixes
553 Suppress the printing of module qualification prefixes
554 -dsuppress-stg-free-vars
556 Suppress the printing of closure free variable lists in STG out‐
557 put
558 -dsuppress-ticks
560 Suppress "ticks" in the pretty-printer output.
561 -dsuppress-timestamps
563 Suppress timestamps in dumps
564 -dsuppress-type-applications
566 Suppress type applications
567 -dsuppress-type-signatures
569 Suppress type signatures
570 -dsuppress-unfoldings
572 Suppress the printing of the stable unfolding of a variable at
573 its binding site
574 -dsuppress-uniques
576 Suppress the printing of uniques in debug output (easier to use
577 diff)
578 -dsuppress-var-kinds
580 Suppress the printing of variable kinds
581 -dth-dec-file
583 Dump evaluated TH declarations into *.th.hs files
584 -dunique-increment=⟨i⟩
586 Set the increment for the generated Unique's to ⟨i⟩.
587 -dverbose-core2core
589 Show output from each core-to-core pass
590 -dverbose-stg2stg
592 Show output from each STG-to-STG pass
593 -falignment-sanitisation
595 Compile with alignment checks for all info table dereferences.
596 -fcatch-bottoms
598 Insert error expressions after bottoming expressions; useful
599 when debugging the compiler.
600 -fllvm-fill-undef-with-garbage
602 Intruct LLVM to fill dead STG registers with garbage
603 -fproc-alignment
605 Align functions at given boundary.
606 -g Produce DWARF debug information in compiled object files. ⟨n⟩
608 can be 0, 1, or 2, with higher numbers producing richer output.
609 If ⟨n⟩ is omitted, level 2 is assumed.
610 C pre-processor
612 -cpp Run the C pre-processor on Haskell source files
613 -D⟨symbol⟩[=⟨value⟩]
615 Define a symbol in the C pre-processor
616 -I⟨dir⟩
618 Add ⟨dir⟩ to the directory search list for #include files
619 -U⟨symbol⟩
621 Undefine a symbol in the C pre-processor
622 Finding imports
624 -i Empty the import directory list
625 -i⟨dir⟩[:⟨dir⟩]*
627 add ⟨dir⟩, ⟨dir2⟩, etc. to import path
628 Interactive mode
630 -fbreak-on-error
631 Break on uncaught exceptions and errors
632 -fbreak-on-exception
634 Break on any exception thrown
635 -fghci-hist-size=⟨n⟩
637 Set the number of entries GHCi keeps for :history. See
638 ghci-debugger.
639 -fghci-leak-check
641 (Debugging only) check for space leaks when loading new modules
642 in GHCi.
643 -flocal-ghci-history
645 Use current directory for the GHCi command history file
646 .ghci-history.
647 -fno-it
649 No longer set the special variable it.
650 -fprint-bind-result
652 Turn on printing of binding results in GHCi
653 -fshow-loaded-modules
655 Show the names of modules that GHCi loaded after a :load com‐
656 mand.
657 -ghci-script
659 Read additional .ghci files
660 -ignore-dot-ghci
662 Disable reading of .ghci files
663 -interactive-print ⟨expr⟩
665 Select the function to use for printing evaluated expressions in
666 GHCi
667 Interface files
669 --show-iface ⟨file⟩
670 See modes.
671 -ddump-hi
673 Dump the new interface to stdout
674 -ddump-hi-diffs
676 Show the differences vs. the old interface
677 -ddump-minimal-imports
679 Dump a minimal set of imports
680 Keeping intermediate files
682 -keep-hc-file
683 Retain intermediate .hc files.
684 -keep-hi-files
686 Retain intermediate .hi files (the default).
687 -keep-llvm-file
689 Retain intermediate LLVM .ll files. Implies -fllvm.
690 -keep-o-files
692 Retain intermediate .o files (the default).
693 -keep-s-file
695 Retain intermediate .s files.
696 -keep-tmp-files
698 Retain all intermediate temporary files.
699 Language options
701 -fsort-by-size-hole-fits
702 Sort valid hole fits by size.
703 -fsort-by-subsumption-hole-fits
705 Sort valid hole fits by subsumption.
706 -XAllowAmbiguousTypes
708 Allow the user to write ambiguous types, and the type inference
709 engine to infer them.
710 -XApplicativeDo
712 Enable Applicative do-notation desugaring
713 -XArrows
715 Enable arrow notation extension
716 -XBangPatterns
718 Enable bang patterns.
719 -XBinaryLiterals
721 Enable support for binary literals.
722 -XBlockArguments
724 Allow do blocks and other constructs as function arguments.
725 -XCApiFFI
727 Enable the CAPI calling convention.
728 -XConstrainedClassMethods
730 Enable constrained class methods.
731 -XConstraintKinds
733 Enable a kind of constraints.
734 -XCPP Enable the C preprocessor.
736 -XDataKinds
738 Enable datatype promotion.
739 -XDatatypeContexts
741 Allow contexts on data types.
742 -XDefaultSignatures
744 Enable default signatures.
745 -XDeriveAnyClass
747 Enable deriving for any class.
748 -XDeriveDataTypeable
750 Enable deriving for the Data class. Implied by AutoDeriveTy‐
751 peable.
752 -XDeriveFoldable
754 Enable deriving for the Foldable class. Implied by Derive‐
755 Traversable.
756 -XDeriveFunctor
758 Enable deriving for the Functor class. Implied by Derive‐
759 Traversable.
760 -XDeriveGeneric
762 Enable deriving for the Generic class.
763 -XDeriveLift
765 Enable deriving for the Lift class
766 -XDeriveTraversable
768 Enable deriving for the Traversable class. Implies DeriveFunc‐
769 tor and DeriveFoldable.
770 -XDerivingStrategies
772 Enables deriving strategies.
773 -XDerivingVia
775 Enable deriving instances via types of the same runtime repre‐
776 sentation. Implies DerivingStrategies.
777 -XDisambiguateRecordFields
779 Enable record field disambiguation. Implied by RecordWildCards.
780 -XDuplicateRecordFields
782 Allow definition of record types with identically-named fields.
783 -XEmptyCase
785 Allow empty case alternatives.
786 -XEmptyDataDecls
788 Allow definition of empty data types.
789 -XEmptyDataDeriving
791 Allow deriving instances of standard type classes for empty data
792 types.
793 -XExistentialQuantification
795 Enable liberalised type synonyms.
796 -XExplicitForAll
798 Enable explicit universal quantification. Implied by Scoped‐
799 TypeVariables, LiberalTypeSynonyms, RankNTypes and Existen‐
800 tialQuantification.
801 -XExplicitNamespaces
803 Enable using the keyword type to specify the namespace of
804 entries in imports and exports (explicit-namespaces). Implied
805 by TypeOperators and TypeFamilies.
806 -XExtendedDefaultRules
808 Use GHCi's extended default rules in a normal module.
809 -XFlexibleContexts
811 Enable flexible contexts. Implied by ImplicitParams.
812 -XFlexibleInstances
814 Enable flexible instances. Implies TypeSynonymInstances.
815 Implied by ImplicitParams.
816 -XForeignFunctionInterface
818 Enable foreign function interface.
819 -XFunctionalDependencies
821 Enable functional dependencies. Implies MultiParamTypeClasses.
822 -XGADTs
824 Enable generalised algebraic data types. Implies GADTSyntax and
825 MonoLocalBinds.
826 -XGADTSyntax
828 Enable generalised algebraic data type syntax.
829 -XGeneralisedNewtypeDeriving
831 Enable newtype deriving.
832 -XGeneralizedNewtypeDeriving
834 Enable newtype deriving.
835 -XHexFloatLiterals
837 Enable support for hexadecimal floating point literals.
838 -XImplicitParams
840 Enable Implicit Parameters. Implies FlexibleContexts and Flexi‐
841 bleInstances.
842 -XImpredicativeTypes
844 Enable impredicative types. Implies RankNTypes.
845 -XIncoherentInstances
847 Enable incoherent instances. Implies OverlappingInstances.
848 -XInstanceSigs
850 Enable instance signatures.
851 -XInterruptibleFFI
853 Enable interruptible FFI.
854 -XKindSignatures
856 Enable kind signatures. Implied by TypeFamilies and PolyKinds.
857 -XLambdaCase
859 Enable lambda-case expressions.
860 -XLiberalTypeSynonyms
862 Enable liberalised type synonyms.
863 -XMagicHash
865 Allow # as a postfix modifier on identifiers.
866 -XMonadComprehensions
868 Enable monad comprehensions.
869 -XMonadFailDesugaring
871 Enable monadfail desugaring.
872 -XMonoLocalBinds
874 Enable do not generalise local bindings. Implied by TypeFami‐
875 lies and GADTs.
876 -XMultiParamTypeClasses
878 Enable multi parameter type classes. Implied by FunctionalDe‐
879 pendencies.
880 -XMultiWayIf
882 Enable multi-way if-expressions.
883 -XNamedFieldPuns
885 Enable record puns.
886 -XNamedWildCards
888 Enable named wildcards.
889 -XNegativeLiterals
891 Enable support for negative literals.
892 -XNoImplicitPrelude
894 Don't implicitly import Prelude. Implied by RebindableSyntax.
895 -XNoMonomorphismRestriction
897 Disable the monomorphism restriction.
898 -XNoPatternGuards
900 Disable pattern guards. Implied by Haskell98.
901 -XNoTraditionalRecordSyntax
903 Disable support for traditional record syntax (as supported by
904 Haskell 98) C {f = x}
905 -XNPlusKPatterns
907 Enable support for n+k patterns. Implied by Haskell98.
908 -XNullaryTypeClasses
910 Deprecated, does nothing. nullary (no parameter) type classes
911 are now enabled using MultiParamTypeClasses.
912 -XNumDecimals
914 Enable support for 'fractional' integer literals.
915 -XNumericUnderscores
917 Enable support for numeric underscores.
918 -XOverlappingInstances
920 Enable overlapping instances.
921 -XOverloadedLabels
923 Enable overloaded labels.
924 -XOverloadedLists
926 Enable overloaded lists.
927 -XOverloadedStrings
929 Enable overloaded string literals.
930 -XPackageImports
932 Enable package-qualified imports.
933 -XParallelListComp
935 Enable parallel list comprehensions.
936 -XPartialTypeSignatures
938 Enable partial type signatures.
939 -XPatternSynonyms
941 Enable pattern synonyms.
942 -XPolyKinds
944 Enable kind polymorphism. Implies KindSignatures.
945 -XPostfixOperators
947 Enable postfix operators.
948 -XQuantifiedConstraints
950 Allow forall quantifiers in constraints.
951 -XQuasiQuotes
953 Enable quasiquotation.
954 -XRank2Types
956 Enable rank-2 types. Synonym for RankNTypes.
957 -XRankNTypes
959 Enable rank-N types. Implied by ImpredicativeTypes.
960 -XRebindableSyntax
962 Employ rebindable syntax. Implies NoImplicitPrelude.
963 -XRecordWildCards
965 Enable record wildcards. Implies DisambiguateRecordFields.
966 -XRecursiveDo
968 Enable recursive do (mdo) notation.
969 -XRoleAnnotations
971 Enable role annotations.
972 -XSafe Enable the Safe Haskell Safe mode.
974 -XScopedTypeVariables
976 Enable lexically-scoped type variables.
977 -XStandaloneDeriving
979 Enable standalone deriving.
980 -XStarIsType
982 Treat * as Data.Kind.Type.
983 -XStaticPointers
985 Enable static pointers.
986 -XStrict
988 Make bindings in the current module strict by default.
989 -XStrictData
991 Enable default strict datatype fields.
992 -XTemplateHaskell
994 Enable Template Haskell.
995 -XTemplateHaskellQuotes
997 Enable quotation subset of Template Haskell.
998 -XTransformListComp
1000 Enable generalised list comprehensions.
1001 -XTrustworthy
1003 Enable the Safe Haskell Trustworthy mode.
1004 -XTupleSections
1006 Enable tuple sections.
1007 -XTypeApplications
1009 Enable type application syntax.
1010 -XTypeFamilies
1012 Enable type families. Implies ExplicitNamespaces, KindSigna‐
1013 tures, and MonoLocalBinds.
1014 -XTypeFamilyDependencies
1016 Enable injective type families. Implies TypeFamilies.
1017 -XTypeInType
1019 Deprecated. Enable kind polymorphism and datatype promotion.
1020 -XTypeOperators
1022 Enable type operators. Implies ExplicitNamespaces.
1023 -XTypeSynonymInstances
1025 Enable type synonyms in instance heads. Implied by FlexibleIn‐
1026 stances.
1027 -XUnboxedSums
1029 Enable unboxed sums.
1030 -XUnboxedTuples
1032 Enable the use of unboxed tuple syntax.
1033 -XUndecidableInstances
1035 Enable undecidable instances.
1036 -XUndecidableSuperClasses
1038 Allow all superclass constraints, including those that may
1039 result in non-termination of the typechecker.
1040 -XUnicodeSyntax
1042 Enable unicode syntax.
1043 -XUnsafe
1045 Enable Safe Haskell Unsafe mode.
1046 -XViewPatterns
1048 Enable view patterns.
1049 Linking options
1051 -c Stop after generating object (.o) file
1052 -debug Use the debugging runtime
1054 -dylib-install-name ⟨path⟩
1056 Set the install name (via -install_name passed to Apple's
1057 linker), specifying the full install path of the library file.
1058 Any libraries or executables that link with it later will pick
1059 up that path as their runtime search location for it. (Dar‐
1060 win/OS X only)
1061 -dynamic
1063 Build dynamically-linked object files and executables
1064 -dynload
1066 Selects one of a number of modes for finding shared libraries at
1067 runtime.
1068 -eventlog
1070 Enable runtime event tracing
1071 -fno-embed-manifest
1073 Do not embed the manifest in the executable (Windows only)
1074 -fno-gen-manifest
1076 Do not generate a manifest file (Windows only)
1077 -fno-shared-implib
1079 Don't generate an import library for a DLL (Windows only)
1080 -framework ⟨name⟩
1082 On Darwin/OS X/iOS only, link in the framework ⟨name⟩. This
1083 option corresponds to the -framework option for Apple's Linker.
1084 -framework-path ⟨dir⟩
1086 On Darwin/OS X/iOS only, add ⟨dir⟩ to the list of directories
1087 searched for frameworks. This option corresponds to the -F
1088 option for Apple's Linker.
1089 -fwhole-archive-hs-libs
1091 When linking a binary executable, this inserts the flag
1092 -Wl,--whole-archive before any -l flags for Haskell libraries,
1093 and -Wl,--no-whole-archive afterwards
1094 -L ⟨dir⟩
1096 Add ⟨dir⟩ to the list of directories searched for libraries
1097 -l ⟨lib⟩
1099 Link in library ⟨lib⟩
1100 -main-is ⟨thing⟩
1102 Set main module and function
1103 -no-hs-main
1105 Don't assume this program contains main
1106 -no-rtsopts-suggestions
1108 Don't print RTS suggestions about linking with
1109 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩].
1110 -package ⟨name⟩
1112 Expose package ⟨pkg⟩
1113 -pie Instruct the linker to produce a position-independent exe‐
1115 cutable.
1116 -rdynamic
1118 This instructs the linker to add all symbols, not only used
1119 ones, to the dynamic symbol table. Currently Linux and Win‐
1120 dows/MinGW32 only. This is equivalent to using -optl -rdynamic
1121 on Linux, and -optl -export-all-symbols on Windows.
1122 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩]
1124 Control whether the RTS behaviour can be tweaked via com‐
1125 mand-line flags and the GHCRTS environment variable. Using none
1126 means no RTS flags can be given; some means only a minimum of
1127 safe options can be given (the default); all (or no argument at
1128 all) means that all RTS flags are permitted; ignore means RTS
1129 flags can be given, but are treated as regular arguments and
1130 passed to the Haskell program as arguments; ignoreAll is the
1131 same as ignore, but GHCRTS is also ignored. -rtsopts does not
1132 affect -with-rtsopts behavior; flags passed via -with-rtsopts
1133 are used regardless of -rtsopts.
1134 -shared
1136 Generate a shared library (as opposed to an executable)
1137 -split-objs
1139 Split objects (for libraries)
1140 -split-sections
1142 Split sections for link-time dead-code stripping
1143 -static
1145 Use static Haskell libraries
1146 -staticlib
1148 Generate a standalone static library (as opposed to an exe‐
1149 cutable). This is useful when cross compiling. The library
1150 together with all its dependencies ends up in in a single static
1151 library that can be linked against.
1152 -threaded
1154 Use the threaded runtime
1155 -with-rtsopts=⟨opts⟩
1157 Set the default RTS options to ⟨opts⟩.
1158 Miscellaneous options
1160 -fexternal-interpreter
1161 Run interpreted code in a separate process
1162 -fglasgow-exts
1164 Deprecated. Enable most language extensions; see options-lan‐
1165 guage for exactly which ones.
1166 -ghcversion-file ⟨path to ghcversion.h⟩
1168 (GHC as a C compiler only) Use this ghcversion.h file
1169 -H ⟨size⟩
1171 Set the minimum size of the heap to ⟨size⟩
1172 -j[⟨n⟩]
1174 When compiling with --make, compile ⟨n⟩ modules in parallel.
1175 Modes of operation
1177 --frontend ⟨module⟩
1178 run GHC with the given frontend plugin; see frontend_plugins for
1179 details.
1180 --help Display help
1182 --info display information about the compiler
1184 --interactive
1186 Interactive mode - normally used by just running ghci; see ghci
1187 for details.
1188 --make Build a multi-module Haskell program, automatically figuring out
1190 dependencies. Likely to be much easier, and faster, than using
1191 make; see make-mode for details.
1192 --mk-dll
1194 DLL-creation mode (Windows only)
1195 --numeric-version
1197 display GHC version (numeric only)
1198 --print-libdir
1200 display GHC library directory
1201 --show-iface ⟨file⟩
1203 display the contents of an interface file.
1204 --show-options
1206 display the supported command line options
1207 --supported-extensions
1209 display the supported language extensions
1210 --version
1212 display GHC version
1213 -e ⟨expr⟩
1215 Evaluate expr; see eval-mode for details.
1216 -M generate dependency information suitable for use in a Makefile;
1218 see makefile-dependencies for details.
1219 Individual optimizations
1221 -fasm-shortcutting
1222 Enable shortcutting on assembly. Implied by -O2.
1223 -fcall-arity
1225 Enable call-arity optimisation. Implied by -O.
1226 -fcase-folding
1228 Enable constant folding in case expressions. Implied by -O.
1229 -fcase-merge
1231 Enable case-merging. Implied by -O.
1232 -fcmm-elim-common-blocks
1234 Enable Cmm common block elimination. Implied by -O.
1235 -fcmm-sink
1237 Enable Cmm sinking. Implied by -O.
1238 -fcpr-anal
1240 Turn on CPR analysis in the demand analyser. Implied by -O.
1241 -fcross-module-specialise
1243 Turn on specialisation of overloaded functions imported from
1244 other modules.
1245 -fcse Enable common sub-expression elimination. Implied by -O.
1247 -fdicts-cheap
1249 Make dictionary-valued expressions seem cheap to the optimiser.
1250 -fdicts-strict
1252 Make dictionaries strict
1253 -fdmd-tx-dict-sel
1255 Use a special demand transformer for dictionary selectors.
1256 Always enabled by default.
1257 -fdo-eta-reduction
1259 Enable eta-reduction. Implied by -O.
1260 -fdo-lambda-eta-expansion
1262 Enable lambda eta-expansion. Always enabled by default.
1263 -feager-blackholing
1265 Turn on eager blackholing
1266 -fenable-rewrite-rules
1268 Switch on all rewrite rules (including rules generated by auto‐
1269 matic specialisation of overloaded functions). Implied by -O.
1270 -fexcess-precision
1272 Enable excess intermediate precision
1273 -fexitification
1275 Enables exitification optimisation. Implied by -O.
1276 -fexpose-all-unfoldings
1278 Expose all unfoldings, even for very large or recursive func‐
1279 tions.
1280 -ffloat-in
1282 Turn on the float-in transformation. Implied by -O.
1283 -ffull-laziness
1285 Turn on full laziness (floating bindings outwards). Implied by
1286 -O.
1287 -ffun-to-thunk
1289 Allow worker-wrapper to convert a function closure into a thunk
1290 if the function does not use any of its arguments. Off by
1291 default.
1292 -fignore-asserts
1294 Ignore assertions in the source. Implied by -O.
1295 -fignore-interface-pragmas
1297 Ignore pragmas in interface files. Implied by -O0 only.
1298 -flate-dmd-anal
1300 Run demand analysis again, at the end of the simplification
1301 pipeline
1302 -flate-specialise
1304 Run a late specialisation pass
1305 -fliberate-case
1307 Turn on the liberate-case transformation. Implied by -O2.
1308 -fliberate-case-threshold=⟨n⟩
1310 default: 2000. Set the size threshold for the liberate-case
1311 transformation to ⟨n⟩
1312 -fllvm-pass-vectors-in-regs
1314 Pass vector value in vector registers for function calls
1315 -floopification
1317 Turn saturated self-recursive tail-calls into local jumps in the
1318 generated assembly. Implied by -O.
1319 -fmax-inline-alloc-size=⟨n⟩
1321 default: 128. Set the maximum size of inline array allocations
1322 to ⟨n⟩ bytes (default: 128).
1323 -fmax-inline-memcpy-insns=⟨n⟩
1325 default: 32. Inline memcpy calls if they would generate no more
1326 than ⟨n⟩ pseudo instructions.
1327 -fmax-inline-memset-insns=⟨n⟩
1329 default: 32. Inline memset calls if they would generate no more
1330 than ⟨n⟩ pseudo instructions
1331 -fmax-simplifier-iterations=⟨n⟩
1333 default: 4. Set the max iterations for the simplifier.
1334 -fmax-uncovered-patterns=⟨n⟩
1336 default: 4. Set the maximum number of patterns to display in
1337 warnings about non-exhaustive ones.
1338 -fmax-worker-args=⟨n⟩
1340 default: 10. If a worker has that many arguments, none will be
1341 unpacked anymore.
1342 -fno-opt-coercion
1344 Turn off the coercion optimiser
1345 -fno-pre-inlining
1347 Turn off pre-inlining
1348 -fno-state-hack
1350 Turn off the state hackwhereby any lambda with a real-world
1351 state token as argument is considered to be single-entry. Hence
1352 OK to inline things inside it.
1353 -fomit-interface-pragmas
1355 Don't generate interface pragmas. Implied by -O0 only.
1356 -fomit-yields
1358 Omit heap checks when no allocation is being performed.
1359 -foptimal-applicative-do
1361 Use a slower but better algorithm for ApplicativeDo
1362 -fpedantic-bottoms
1364 Make GHC be more precise about its treatment of bottom (but see
1365 also -fno-state-hack). In particular, GHC will not eta-expand
1366 through a case expression.
1367 -fregs-graph
1369 Use the graph colouring register allocator for register alloca‐
1370 tion in the native code generator. Implied by -O2.
1371 -fregs-iterative
1373 Use the iterative coalescing graph colouring register allocator
1374 in the native code generator.
1375 -fsimpl-tick-factor=⟨n⟩
1377 default: 100. Set the percentage factor for simplifier ticks.
1378 -fsimplifier-phases=⟨n⟩
1380 default: 2. Set the number of phases for the simplifier.
1381 Ignored with -O0.
1382 -fsolve-constant-dicts
1384 When solving constraints, try to eagerly solve super classes
1385 using available dictionaries.
1386 -fspec-constr
1388 Turn on the SpecConstr transformation. Implied by -O2.
1389 -fspec-constr-count=⟨n⟩
1391 default: 3.* Set to ⟨n⟩ the maximum number of specialisations
1392 that will be created for any one function by the SpecConstr
1393 transformation.
1394 -fspec-constr-keen
1396 Specialize a call with an explicit constructor argument, even if
1397 the argument is not scrutinised in the body of the function
1398 -fspec-constr-threshold=⟨n⟩
1400 default: 2000. Set the size threshold for the SpecConstr trans‐
1401 formation to ⟨n⟩.
1402 -fspecialise
1404 Turn on specialisation of overloaded functions. Implied by -O.
1405 -fspecialise-aggressively
1407 Turn on specialisation of overloaded functions regardless of
1408 size, if unfolding is available
1409 -fstatic-argument-transformation
1411 Turn on the static argument transformation.
1412 -fstg-cse
1414 Enable common sub-expression elimination on the STG intermediate
1415 language
1416 -fstrictness
1418 Turn on strictness analysis. Implied by -O. Implies
1419 -fworker-wrapper
1420 -fstrictness-before=⟨n⟩
1422 Run an additional strictness analysis before simplifier phase
1423 ⟨n⟩
1424 -funbox-small-strict-fields
1426 Flatten strict constructor fields with a pointer-sized represen‐
1427 tation. Implied by -O.
1428 -funbox-strict-fields
1430 Flatten strict constructor fields
1431 -funfolding-creation-threshold=⟨n⟩
1433 default: 750. Tweak unfolding settings.
1434 -funfolding-dict-discount=⟨n⟩
1436 default: 30. Tweak unfolding settings.
1437 -funfolding-fun-discount=⟨n⟩
1439 default: 60. Tweak unfolding settings.
1440 -funfolding-keeness-factor=⟨n⟩
1442 default: 1.5. Tweak unfolding settings.
1443 -funfolding-use-threshold=⟨n⟩
1445 default: 60. Tweak unfolding settings.
1446 Optimization levels
1448 -O Enable level 1 optimisations
1449 -O0 Disable optimisations (default)
1451 -O2 Enable level 2 optimisations
1453 Package options
1455 -clear-package-db
1456 Clear the package db stack.
1457 -distrust ⟨pkg⟩
1459 Expose package ⟨pkg⟩ and set it to be distrusted. See
1460 safe-haskell.
1461 -distrust-all-packages
1463 Distrust all packages by default. See safe-haskell.
1464 -fpackage-trust
1466 Enable Safe Haskell trusted package requirement for trustworthy
1467 modules.
1468 -global-package-db
1470 Add the global package db to the stack.
1471 -hide-all-packages
1473 Hide all packages by default
1474 -hide-package ⟨pkg⟩
1476 Hide package ⟨pkg⟩
1477 -ignore-package ⟨pkg⟩
1479 Ignore package ⟨pkg⟩
1480 -no-auto-link-packages
1482 Don't automatically link in the base and rts packages.
1483 -no-global-package-db
1485 Remove the global package db from the stack.
1486 -no-user-package-db
1488 Remove the user's package db from the stack.
1489 -package ⟨pkg⟩
1491 Expose package ⟨pkg⟩
1492 -package-db ⟨file⟩
1494 Add ⟨file⟩ to the package db stack.
1495 -package-env ⟨file⟩|⟨name⟩
1497 Use the specified package environment.
1498 -package-id ⟨unit-id⟩
1500 Expose package by id ⟨unit-id⟩
1501 -this-unit-id ⟨unit-id⟩
1503 Compile to be part of unit (i.e. package) ⟨unit-id⟩
1504 -trust ⟨pkg⟩
1506 Expose package ⟨pkg⟩ and set it to be trusted. See safe-haskell.
1507 -user-package-db
1509 Add the user's package db to the stack.
1510 Phases of compilation
1512 -C Stop after generating C (.hc file)
1513 -c Stop after generating object (.o) file
1515 -E Stop after preprocessing (.hspp file)
1517 -F Enable the use of a pre-processor (set with -pgmF ⟨cmd⟩)
1519 -S Stop after generating assembly (.s file)
1521 -x ⟨suffix⟩
1523 Override default behaviour for source files
1524 Overriding external programs
1526 -pgma ⟨cmd⟩
1527 Use ⟨cmd⟩ as the assembler
1528 -pgmc ⟨cmd⟩
1530 Use ⟨cmd⟩ as the C compiler
1531 -pgmdll ⟨cmd⟩
1533 Use ⟨cmd⟩ as the DLL generator
1534 -pgmF ⟨cmd⟩
1536 Use ⟨cmd⟩ as the pre-processor (with -F only)
1537 -pgmi ⟨cmd⟩
1539 Use ⟨cmd⟩ as the external interpreter command.
1540 -pgmL ⟨cmd⟩
1542 Use ⟨cmd⟩ as the literate pre-processor
1543 -pgml ⟨cmd⟩
1545 Use ⟨cmd⟩ as the linker
1546 -pgmlc ⟨cmd⟩
1548 Use ⟨cmd⟩ as the LLVM compiler
1549 -pgmlibtool ⟨cmd⟩
1551 Use ⟨cmd⟩ as the command for libtool (with -staticlib only).
1552 -pgmlo ⟨cmd⟩
1554 Use ⟨cmd⟩ as the LLVM optimiser
1555 -pgmP ⟨cmd⟩
1557 Use ⟨cmd⟩ as the C pre-processor (with -cpp only)
1558 -pgms ⟨cmd⟩
1560 Use ⟨cmd⟩ as the splitter
1561 -pgmwindres ⟨cmd⟩
1563 Use ⟨cmd⟩ as the program for embedding manifests on Windows.
1564 Phase-specific options
1566 -opta ⟨option⟩
1567 pass ⟨option⟩ to the assembler
1568 -optc ⟨option⟩
1570 pass ⟨option⟩ to the C compiler
1571 -optdll ⟨option⟩
1573 pass ⟨option⟩ to the DLL generator
1574 -optF ⟨option⟩
1576 pass ⟨option⟩ to the custom pre-processor
1577 -opti ⟨option⟩
1579 pass ⟨option⟩ to the interpreter sub-process.
1580 -optL ⟨option⟩
1582 pass ⟨option⟩ to the literate pre-processor
1583 -optl ⟨option⟩
1585 pass ⟨option⟩ to the linker
1586 -optlc ⟨option⟩
1588 pass ⟨option⟩ to the LLVM compiler
1589 -optlo ⟨option⟩
1591 pass ⟨option⟩ to the LLVM optimiser
1592 -optP ⟨option⟩
1594 pass ⟨option⟩ to cpp (with -cpp only)
1595 -optwindres ⟨option⟩
1597 pass ⟨option⟩ to windres.
1598 Platform-specific options
1600 -msse2 (x86 only) Use SSE2 for floating-point operations
1601 -msse4.2
1603 (x86 only) Use SSE4.2 for floating-point operations
1604 Compiler plugins
1606 -fplugin-opt=⟨module⟩:⟨args⟩
1607 Give arguments to a plugin module; module must be specified with
1608 -fplugin=⟨module⟩
1609 -fplugin=⟨module⟩
1611 Load a plugin exported by a given module
1612 -hide-all-plugin-packages
1614 Hide all packages for plugins by default
1615 -plugin-package ⟨pkg⟩
1617 Expose ⟨pkg⟩ for plugins
1618 -plugin-package-id ⟨pkg-id⟩
1620 Expose ⟨pkg-id⟩ for plugins
1621 Profiling
1623 -fno-prof-auto
1624 Disables any previous -fprof-auto, -fprof-auto-top, or
1625 -fprof-auto-exported options.
1626 -fno-prof-cafs
1628 Disables any previous -fprof-cafs option.
1629 -fno-prof-count-entries
1631 Do not collect entry counts
1632 -fprof-auto
1634 Auto-add SCC\ s to all bindings not marked INLINE
1635 -fprof-auto-calls
1637 Auto-add SCC\ s to all call sites
1638 -fprof-auto-exported
1640 Auto-add SCC\ s to all exported bindings not marked INLINE
1641 -fprof-auto-top
1643 Auto-add SCC\ s to all top-level bindings not marked INLINE
1644 -fprof-cafs
1646 Auto-add SCC\ s to all CAFs
1647 -prof Turn on profiling
1649 -ticky Turn on ticky-ticky profiling
1651 Program coverage
1653 -fhpc Turn on Haskell program coverage instrumentation
1654 Recompilation checking
1656 -fforce-recomp
1657 Turn off recompilation checking. This is implied by any -ddump-X
1658 option when compiling a single file (i.e. when using -c).
1659 -fignore-hpc-changes
1661 Do not recompile modules just to match changes to HPC flags.
1662 This is especially useful for avoiding recompilation when using
1663 GHCi, and is enabled by default for GHCi.
1664 -fignore-optim-changes
1666 Do not recompile modules just to match changes to optimisation
1667 flags. This is especially useful for avoiding recompilation when
1668 using GHCi, and is enabled by default for GHCi.
1669 Redirecting output
1671 --exclude-module=⟨file⟩
1672 Regard ⟨file⟩ as "stable"; i.e., exclude it from having depen‐
1673 dencies on it.
1674 -ddump-mod-cycles
1676 Dump module cycles
1677 -dep-makefile ⟨file⟩
1679 Use ⟨file⟩ as the makefile
1680 -dep-suffix ⟨suffix⟩
1682 Make dependencies that declare that files with suffix
1683 .⟨suf⟩⟨osuf⟩ depend on interface files with suffix .⟨suf⟩hi
1684 -dumpdir ⟨dir⟩
1686 redirect dump files
1687 -hcsuf ⟨suffix⟩
1689 set the suffix to use for intermediate C files
1690 -hidir ⟨dir⟩
1692 set directory for interface files
1693 -hisuf ⟨suffix⟩
1695 set the suffix to use for interface files
1696 -include-pkg-deps
1698 Regard modules imported from packages as unstable
1699 -o ⟨file⟩
1701 set output filename
1702 -odir ⟨dir⟩
1704 set directory for object files
1705 -ohi ⟨file⟩
1707 set the filename in which to put the interface
1708 -osuf ⟨suffix⟩
1710 set the output file suffix
1711 -outputdir ⟨dir⟩
1713 set output directory
1714 -stubdir ⟨dir⟩
1716 redirect FFI stub files
1717 Temporary files
1719 -tmpdir ⟨dir⟩
1720 set the directory for temporary files
1721 Verbosity options
1723 -fabstract-refinement-hole-fits
1724 default: off. Toggles whether refinements where one or more or
1725 more of the holes are abstract are reported.
1726 -fdiagnostics-color=⟨always|auto|never⟩
1728 Use colors in error messages
1729 -fdiagnostics-show-caret
1731 Whether to show snippets of original source code
1732 -ferror-spans
1734 Output full span in error messages
1735 -fhide-source-paths
1737 hide module source and object paths
1738 -fmax-refinement-hole-fits=⟨n⟩
1740 default: 6. Set the maximum number of refinement hole fits for
1741 typed holes to display in type error messages.
1742 -fmax-relevant-binds=⟨n⟩
1744 default: 6. Set the maximum number of bindings to display in
1745 type error messages.
1746 -fmax-valid-hole-fits=⟨n⟩
1748 default: 6. Set the maximum number of valid hole fits for typed
1749 holes to display in type error messages.
1750 -fno-show-valid-hole-fits
1752 Disables showing a list of valid hole fits for typed holes in
1753 type error messages.
1754 -fno-sort-valid-hole-fits
1756 Disables the sorting of the list of valid hole fits for typed
1757 holes in type error messages.
1758 -fprint-equality-relations
1760 Distinguish between equality relations when printing
1761 -fprint-expanded-synonyms
1763 In type errors, also print type-synonym-expanded types.
1764 -fprint-explicit-coercions
1766 Print coercions in types
1767 -fprint-explicit-foralls
1769 Print explicit forall quantification in types. See also -XEx‐
1770 plicitForAll
1771 -fprint-explicit-kinds
1773 Print explicit kind foralls and kind arguments in types. See
1774 also -XKindSignatures
1775 -fprint-explicit-runtime-reps
1777 Print RuntimeRep variables in types which are runtime-represen‐
1778 tation polymorphic.
1779 -fprint-explicit-runtime-reps
1781 Print RuntimeRep variables in types which are runtime-represen‐
1782 tation polymorphic.
1783 -fprint-potential-instances
1785 display all available instances in type error messages
1786 -fprint-typechecker-elaboration
1788 Print extra information from typechecker.
1789 -fprint-unicode-syntax
1791 Use unicode syntax when printing expressions, types and kinds.
1792 See also -XUnicodeSyntax
1793 -frefinement-level-hole-fits=⟨n⟩
1795 default: off. Sets the level of refinement of the refinement
1796 hole fits, where level n means that hole fits of up to n holes
1797 will be considered.
1798 -fshow-hole-constraints
1800 Show constraints when reporting typed holes.
1801 -fshow-hole-matches-of-hole-fits
1803 Toggles whether to show the type of the additional holes in
1804 refinement hole fits.
1805 -fshow-provenance-of-hole-fits
1807 Toggles whether to show the provenance of the valid hole fits in
1808 the output.
1809 -fshow-type-app-of-hole-fits
1811 Toggles whether to show the type application of the valid hole
1812 fits in the output.
1813 -fshow-type-app-vars-of-hole-fits
1815 Toggles whether to show what type each quantified variable takes
1816 in a valid hole fit.
1817 -fshow-type-of-hole-fits
1819 Toggles whether to show the type of the valid hole fits in the
1820 output.
1821 -funclutter-valid-hole-fits
1823 Unclutter the list of valid hole fits by not showing provenance
1824 nor type applications of suggestions.
1825 -Rghc-timing
1827 Summarise timing stats for GHC (same as +RTS -tstderr).
1828 -v verbose mode (equivalent to -v3)
1830 -v⟨n⟩ set verbosity level
1832 Warnings
1834 -fdefer-out-of-scope-variables
1835 Convert variable out of scope variables errors into warnings.
1836 Implied by -fdefer-type-errors. See also -Wde‐
1837 ferred-out-of-scope-variables.
1838 -fdefer-type-errors
1840 Turn type errors into warnings, deferring the error until run‐
1841 time. Implies -fdefer-typed-holes and -fdefer-out-of-scope-vari‐
1842 ables. See also -Wdeferred-type-errors
1843 -fdefer-typed-holes
1845 Convert typed hole errors into warnings, deferring the error
1846 until runtime. Implied by -fdefer-type-errors. See also
1847 -Wtyped-holes.
1848 -fhelpful-errors
1850 Make suggestions for mis-spelled names.
1851 -fmax-pmcheck-iterations=⟨n⟩
1853 the iteration limit for the pattern match checker
1854 -fshow-warning-groups
1856 show which group an emitted warning belongs to.
1857 -W enable normal warnings
1859 -w disable all warnings
1861 -Wall enable almost all warnings (details in options-sanity)
1863 -Wall-missed-specialisations
1865 warn when specialisation of any overloaded function fails.
1866 -Wamp (deprecated) warn on definitions conflicting with the Applica‐
1868 tive-Monad Proposal (AMP)
1869 -Wcompat
1871 enable future compatibility warnings (details in options-sanity)
1872 -Wcpp-undef
1874 warn on uses of the #if directive on undefined identifiers
1875 -Wdeferred-out-of-scope-variables
1877 Report warnings when variable out-of-scope errors are deferred
1878 until runtime. See -fdefer-out-of-scope-variables.
1879 -Wdeferred-type-errors
1881 Report warnings when deferred type errors are enabled. This
1882 option is enabled by default. See -fdefer-type-errors.
1883 -Wdeprecated-flags
1885 warn about uses of commandline flags that are deprecated
1886 -Wdeprecations
1888 warn about uses of functions & types that have warnings or dep‐
1889 recated pragmas. Alias for -Wwarnings-deprecations
1890 -Wdodgy-exports
1892 warn about dodgy exports
1893 -Wdodgy-foreign-imports
1895 warn about dodgy foreign imports
1896 -Wdodgy-imports
1898 warn about dodgy imports
1899 -Wduplicate-constraints
1901 warn when a constraint appears duplicated in a type signature
1902 -Wduplicate-exports
1904 warn when an entity is exported multiple times
1905 -Wempty-enumerations
1907 warn about enumerations that are empty
1908 -Werror
1910 make warnings fatal
1911 -Weverything
1913 enable all warnings supported by GHC
1914 -Whi-shadowing
1916 warn when a .hi file in the current directory shadows a library
1917 -Widentities
1919 warn about uses of Prelude numeric conversions that are probably
1920 the identity (and hence could be omitted)
1921 -Wimplicit-kind-vars
1923 warn when kind variables are brought into scope implicitly
1924 despite the "forall-or-nothing" rule
1925 -Wimplicit-prelude
1927 warn when the Prelude is implicitly imported
1928 -Winaccessible-code
1930 warn about inaccessible code
1931 -Wincomplete-patterns
1933 warn when a pattern match could fail
1934 -Wincomplete-record-updates
1936 warn when a record update could fail
1937 -Wincomplete-uni-patterns
1939 warn when a pattern match in a lambda expression or pattern
1940 binding could fail
1941 -Winline-rule-shadowing
1943 Warn if a rewrite RULE might fail to fire because the function
1944 might be inlined before the rule has a chance to fire. See
1945 rules-inline.
1946 -Wmissed-specialisations
1948 warn when specialisation of an imported, overloaded function
1949 fails.
1950 -Wmissing-export-lists
1952 warn when a module declaration does not explicitly list all
1953 exports
1954 -Wmissing-exported-signatures
1956 warn about top-level functions without signatures, only if they
1957 are exported. takes precedence over -Wmissing-signatures
1958 -Wmissing-exported-sigs
1960 (deprecated) warn about top-level functions without signatures,
1961 only if they are exported. takes precedence over -Wmissing-sig‐
1962 natures
1963 -Wmissing-fields
1965 warn when fields of a record are uninitialised
1966 -Wmissing-home-modules
1968 warn when encountering a home module imported, but not listed on
1969 the command line. Useful for cabal to ensure GHC won't pick up
1970 modules, not listed neither in exposed-modules, nor in
1971 other-modules.
1972 -Wmissing-import-lists
1974 warn when an import declaration does not explicitly list all the
1975 names brought into scope
1976 -Wmissing-local-signatures
1978 warn about polymorphic local bindings without signatures
1979 -Wmissing-local-sigs
1981 (deprecated) warn about polymorphic local bindings without sig‐
1982 natures
1983 -Wmissing-methods
1985 warn when class methods are undefined
1986 -Wmissing-monadfail-instances
1988 Warn when a failable pattern is used in a do-block that does not
1989 have a MonadFail instance.
1990 -Wmissing-pattern-synonym-signatures
1992 warn when pattern synonyms do not have type signatures
1993 -Wmissing-signatures
1995 warn about top-level functions without signatures
1996 -Wmonomorphism-restriction
1998 warn when the Monomorphism Restriction is applied
1999 -Wname-shadowing
2001 warn when names are shadowed
2002 -Wno-compat
2004 Disables all warnings enabled by -Wcompat.
2005 -Wnoncanonical-monad-instances
2007 warn when Applicative or Monad instances have noncanonical defi‐
2008 nitions of return, pure, (>>), or (*>). See flag description in
2009 options-sanity for more details.
2010 -Wnoncanonical-monadfail-instances
2012 warn when Monad or MonadFail instances have noncanonical defini‐
2013 tions of fail. See flag description in options-sanity for more
2014 details.
2015 -Wnoncanonical-monoid-instances
2017 warn when Semigroup or Monoid instances have noncanonical defi‐
2018 nitions of (<>) or mappend. See flag description in
2019 options-sanity for more details.
2020 -Worphans
2022 warn when the module contains orphan instance declarations or
2023 rewrite rules
2024 -Woverflowed-literals
2026 warn about literals that will overflow their type
2027 -Woverlapping-patterns
2029 warn about overlapping patterns
2030 -Wpartial-fields
2032 warn when defining a partial record field.
2033 -Wpartial-type-signatures
2035 warn about holes in partial type signatures when -XPartialTypeS‐
2036 ignatures is enabled. Not applicable when -XPartialTypesigna‐
2037 tures is not enabled, in which case errors are generated for
2038 such holes. See partial-type-signatures.
2039 -Wredundant-constraints
2041 Have the compiler warn about redundant constraints in type sig‐
2042 natures.
2043 -Wsafe warn if the module being compiled is regarded to be safe.
2045 -Wsemigroup
2047 warn when a Monoid is not Semigroup, and on non- Semigroup defi‐
2048 nitions of (<>)?
2049 -Wsimplifiable-class-constraints
2051 2arn about class constraints in a type signature that can be
2052 simplified using a top-level instance declaration.
2053 -Wstar-binder
2055 warn about binding the (*) type operator despite -XStarIsType
2056 -Wstar-is-type
2058 warn when * is used to mean Data.Kind.Type
2059 -Wtabs warn if there are tabs in the source file
2061 -Wtrustworthy-safe
2063 warn if the module being compiled is marked as Trustworthy but
2064 it could instead be marked as Safe, a more informative bound.
2065 -Wtype-defaults
2067 warn when defaulting happens
2068 -Wtyped-holes
2070 Report warnings when typed hole errors are deferred until run‐
2071 time. See -fdefer-typed-holes.
2072 -Wunbanged-strict-patterns
2074 warn on pattern bind of unlifted variable that is neither bare
2075 nor banged
2076 -Wunrecognised-pragmas
2078 warn about uses of pragmas that GHC doesn't recognise
2079 -Wunrecognised-warning-flags
2081 throw a warning when an unreconised -W... flag is encountered on
2082 the command line.
2083 -Wunsafe
2085 warn if the module being compiled is regarded to be unsafe. See
2086 safe-haskell
2087 -Wunsupported-calling-conventions
2089 warn about use of an unsupported calling convention
2090 -Wunsupported-llvm-version
2092 Warn when using -fllvm with an unsupported version of LLVM.
2093 -Wunticked-promoted-constructors
2095 warn if promoted constructors are not ticked
2096 -Wunused-binds
2098 warn about bindings that are unused. Alias for
2099 -Wunused-top-binds, -Wunused-local-binds and -Wunused-pat‐
2100 tern-binds
2101 -Wunused-do-bind
2103 warn about do bindings that appear to throw away values of types
2104 other than ()
2105 -Wunused-foralls
2107 warn about type variables in user-written forall\s that are
2108 unused
2109 -Wunused-imports
2111 warn about unnecessary imports
2112 -Wunused-local-binds
2114 warn about local bindings that are unused
2115 -Wunused-matches
2117 warn about variables in patterns that aren't used
2118 -Wunused-pattern-binds
2120 warn about pattern match bindings that are unused
2121 -Wunused-top-binds
2123 warn about top-level bindings that are unused
2124 -Wunused-type-patterns
2126 warn about unused type variables which arise from patterns in
2127 type family and data family instances
2128 -Wwarn make warnings non-fatal
2130 -Wwarnings-deprecations
2132 warn about uses of functions & types that have warnings or dep‐
2133 recated pragmas
2134 -Wwrong-do-bind
2136 warn about do bindings that appear to throw away monadic values
2137 that you should have bound instead
2138
2140 Copyright 2015. The University Court of the University of Glasgow. All
2141 rights reserved.
2142
2144 The GHC Team
2145
2147 2019, GHC Team
21488.6.5 Jul 31, 2019 GHC(1)