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-cfg-weights -ddump-cmm -ddump-cmm-caf -ddump-cmm-cbe
60 -ddump-cmm-cfg -ddump-cmm-cps -ddump-cmm-from-stg
61 -ddump-cmm-info -ddump-cmm-proc -ddump-cmm-procmap
62 -ddump-cmm-raw -ddump-cmm-sink -ddump-cmm-sp -ddump-cmm-split
63 -ddump-cmm-switch -ddump-cmm-verbose -ddump-core-stats
64 -ddump-cse -ddump-deriv -ddump-ds -ddump-ds-preopt
65 -ddump-ec-trace -ddump-file-prefix=⟨str⟩ -ddump-foreign
66 -ddump-hpc -ddump-if-trace -ddump-inlinings -ddump-json
67 -ddump-llvm -ddump-mod-map -ddump-occur-anal -ddump-opt-cmm
68 -ddump-parsed -ddump-parsed-ast -ddump-prep -ddump-rn
69 -ddump-rn-ast -ddump-rn-stats -ddump-rn-trace -ddump-rtti
70 -ddump-rule-firings -ddump-rule-rewrites -ddump-rules
71 -ddump-simpl -ddump-simpl-iterations -ddump-simpl-stats
72 -ddump-spec -ddump-splices -ddump-stg -ddump-str-signatures
73 -ddump-stranal -ddump-tc -ddump-tc-ast -ddump-tc-trace
74 -ddump-ticked -ddump-timings -ddump-to-file -ddump-types
75 -ddump-worker-wrapper -dfaststring-stats -dhex-word-literals
76 -dinitial-unique=⟨s⟩ -dinline-check=⟨str⟩ -dno-debug-output
77 -dppr-case-as-let -dppr-cols=⟨n⟩ -dppr-debug -dppr-user-length
78 -drule-check=⟨str⟩ -dshow-passes -dstg-lint -dsuppress-all
79 -dsuppress-coercions -dsuppress-idinfo -dsuppress-module-pre‐
80 fixes -dsuppress-stg-free-vars -dsuppress-ticks -dsuppress-time‐
81 stamps -dsuppress-type-applications -dsuppress-type-signatures
82 -dsuppress-unfoldings -dsuppress-uniques -dsuppress-var-kinds
83 -dth-dec-file -dunique-increment=⟨i⟩ -dverbose-core2core -dver‐
84 bose-stg2stg -falignment-sanitisation -fcatch-bottoms
85 -fllvm-fill-undef-with-garbage -fproc-alignment -g -g⟨n⟩
86 C pre-processor
88 -cpp -D⟨symbol⟩[=⟨value⟩] -I⟨dir⟩ -U⟨symbol⟩
89 Finding imports
91 -i -i⟨dir⟩[:⟨dir⟩]*
92 Interactive mode
94 -fbreak-on-error -fbreak-on-exception -fghci-hist-size=⟨n⟩
95 -fghci-leak-check -flocal-ghci-history -fno-it
96 -fprint-bind-result -fshow-loaded-modules -ghci-script
97 -ignore-dot-ghci -interactive-print ⟨expr⟩
98 Interface files
100 --show-iface ⟨file⟩ -ddump-hi -ddump-hi-diffs -ddump-mini‐
101 mal-imports
102 Keeping intermediate files
104 -keep-hc-file -keep-hc-files -keep-hi-files -keep-hscpp-file
105 -keep-hscpp-files -keep-llvm-file -keep-llvm-files -keep-o-files
106 -keep-s-file -keep-s-files -keep-tmp-files
107 Language options
109 -fno-safe-haskell -fsort-by-size-hole-fits -fsort-by-subsump‐
110 tion-hole-fits -XAllowAmbiguousTypes -XApplicativeDo -XArrows
111 -XBangPatterns -XBinaryLiterals -XBlockArguments -XCApiFFI
112 -XConstrainedClassMethods -XConstraintKinds -XCPP -XDataKinds
113 -XDatatypeContexts -XDefaultSignatures -XDeriveAnyClass
114 -XDeriveDataTypeable -XDeriveFoldable -XDeriveFunctor -XDeriveG‐
115 eneric -XDeriveLift -XDeriveTraversable -XDerivingStrategies
116 -XDerivingVia -XDisambiguateRecordFields -XDuplicateRecordFields
117 -XEmptyCase -XEmptyDataDecls -XEmptyDataDeriving -XExisten‐
118 tialQuantification -XExplicitForAll -XExplicitNamespaces -XEx‐
119 tendedDefaultRules -XFlexibleContexts -XFlexibleInstances -XFor‐
120 eignFunctionInterface -XFunctionalDependencies -XGADTs -XGADT‐
121 Syntax -XGeneralisedNewtypeDeriving -XGeneralizedNewtypeDeriving
122 -XHexFloatLiterals -XImplicitParams -XImpredicativeTypes -XInco‐
123 herentInstances -XInstanceSigs -XInterruptibleFFI -XKindSigna‐
124 tures -XLambdaCase -XLiberalTypeSynonyms -XMagicHash -XMonadCom‐
125 prehensions -XMonadFailDesugaring -XMonoLocalBinds -XMultiParam‐
126 TypeClasses -XMultiWayIf -XNamedFieldPuns -XNamedWildCards
127 -XNegativeLiterals -XNoImplicitPrelude -XNoMonomorphismRestric‐
128 tion -XNoPatternGuards -XNoTraditionalRecordSyntax -XNPlusKPat‐
129 terns -XNullaryTypeClasses -XNumDecimals -XNumericUnderscores
130 -XOverlappingInstances -XOverloadedLabels -XOverloadedLists
131 -XOverloadedStrings -XPackageImports -XParallelListComp -XPar‐
132 tialTypeSignatures -XPatternSynonyms -XPolyKinds -XPostfixOpera‐
133 tors -XQuantifiedConstraints -XQuasiQuotes -XRank2Types -XRankN‐
134 Types -XRebindableSyntax -XRecordWildCards -XRecursiveDo
135 -XRoleAnnotations -XSafe -XScopedTypeVariables -XStandaloneD‐
136 eriving -XStarIsType -XStaticPointers -XStrict -XStrictData
137 -XTemplateHaskell -XTemplateHaskellQuotes -XTransformListComp
138 -XTrustworthy -XTupleSections -XTypeApplications -XTypeFamilies
139 -XTypeFamilyDependencies -XTypeInType -XTypeOperators -XTypeSyn‐
140 onymInstances -XUnboxedSums -XUnboxedTuples -XUndecidableIn‐
141 stances -XUndecidableSuperClasses -XUnicodeSyntax -XUnsafe
142 -XViewPatterns
143 Linking options
145 -c -debug -dylib-install-name ⟨path⟩ -dynamic -dynload -eventlog
146 -fno-embed-manifest -fno-gen-manifest -fno-shared-implib -frame‐
147 work ⟨name⟩ -framework-path ⟨dir⟩ -fwhole-archive-hs-libs
148 -keep-cafs -L ⟨dir⟩ -l ⟨lib⟩ -main-is ⟨thing⟩ -no-hs-main
149 -no-rtsopts-suggestions -package ⟨name⟩ -pie -rdynamic
150 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩] -shared -split-objs
151 -split-sections -static -staticlib -threaded
152 -with-rtsopts=⟨opts⟩
153 Miscellaneous options
155 -fexternal-interpreter -fglasgow-exts -ghcversion-file ⟨path to
156 ghcversion.h⟩ -H ⟨size⟩ -j[⟨n⟩]
157 Modes of operation
159 --frontend ⟨module⟩ --help -? --info --interactive --make
160 --mk-dll --numeric-version --print-libdir --show-iface ⟨file⟩
161 --show-options --supported-extensions --supported-languages
162 --version -V -e ⟨expr⟩ -M
163 Individual optimizations
165 -fasm-shortcutting -fblock-layout-cfg -fblock-layout-weightless
166 -fblock-layout-weights -fcall-arity -fcase-folding -fcase-merge
167 -fcmm-elim-common-blocks -fcmm-sink -fcpr-anal -fcross-mod‐
168 ule-specialise -fcse -fdicts-cheap -fdicts-strict
169 -fdmd-tx-dict-sel -fdo-eta-reduction -fdo-lambda-eta-expansion
170 -feager-blackholing -fenable-rewrite-rules -fexcess-precision
171 -fexitification -fexpose-all-unfoldings -ffloat-in -ffull-lazi‐
172 ness -ffun-to-thunk -fignore-asserts -fignore-interface-pragmas
173 -flate-dmd-anal -flate-specialise -fliberate-case -fliber‐
174 ate-case-threshold=⟨n⟩ -fllvm-pass-vectors-in-regs -floopifica‐
175 tion -fmax-inline-alloc-size=⟨n⟩ -fmax-inline-memcpy-insns=⟨n⟩
176 -fmax-inline-memset-insns=⟨n⟩ -fmax-simplifier-iterations=⟨n⟩
177 -fmax-uncovered-patterns=⟨n⟩ -fmax-worker-args=⟨n⟩
178 -fno-opt-coercion -fno-pre-inlining -fno-state-hack
179 -fomit-interface-pragmas -fomit-yields -foptimal-applicative-do
180 -fpedantic-bottoms -fregs-graph -fregs-iterative
181 -fsimpl-tick-factor=⟨n⟩ -fsimplifier-phases=⟨n⟩ -fsolve-con‐
182 stant-dicts -fspec-constr -fspec-constr-count=⟨n⟩ -fspec-con‐
183 str-keen -fspec-constr-threshold=⟨n⟩ -fspecialise -fspe‐
184 cialise-aggressively -fstatic-argument-transformation -fstg-cse
185 -fstg-lift-lams -fstg-lift-lams-known
186 -fstg-lift-lams-non-rec-args -fstg-lift-lams-rec-args -fstrict‐
187 ness -fstrictness-before=⟨n⟩ -funbox-small-strict-fields -fun‐
188 box-strict-fields -funfolding-creation-threshold=⟨n⟩ -funfold‐
189 ing-dict-discount=⟨n⟩ -funfolding-fun-discount=⟨n⟩ -funfold‐
190 ing-keeness-factor=⟨n⟩ -funfolding-use-threshold=⟨n⟩
191 Optimization levels
193 -O -O1 -O0 -O2
194 Package options
196 -clear-package-db -distrust ⟨pkg⟩ -distrust-all-packages -fpack‐
197 age-trust -global-package-db -hide-all-packages -hide-package
198 ⟨pkg⟩ -ignore-package ⟨pkg⟩ -no-auto-link-packages
199 -no-global-package-db -no-user-package-db -package ⟨pkg⟩ -pack‐
200 age-db ⟨file⟩ -package-env ⟨file⟩|⟨name⟩ -package-id ⟨unit-id⟩
201 -this-unit-id ⟨unit-id⟩ -trust ⟨pkg⟩ -user-package-db
202 Phases of compilation
204 -C -c -E -F -S -x ⟨suffix⟩
205 Overriding external programs
207 -pgma ⟨cmd⟩ -pgmc ⟨cmd⟩ -pgmdll ⟨cmd⟩ -pgmF ⟨cmd⟩ -pgmi ⟨cmd⟩
208 -pgmL ⟨cmd⟩ -pgml ⟨cmd⟩ -pgmlc ⟨cmd⟩ -pgmlibtool ⟨cmd⟩ -pgmlo
209 ⟨cmd⟩ -pgmP ⟨cmd⟩ -pgms ⟨cmd⟩ -pgmwindres ⟨cmd⟩
210 Phase-specific options
212 -opta ⟨option⟩ -optc ⟨option⟩ -optdll ⟨option⟩ -optF ⟨option⟩
213 -opti ⟨option⟩ -optL ⟨option⟩ -optl ⟨option⟩ -optlc ⟨option⟩
214 -optlo ⟨option⟩ -optP ⟨option⟩ -optwindres ⟨option⟩
215 Platform-specific options
217 -msse2 -msse4.2
218 Compiler plugins
220 -fclear-plugins -fplugin-opt=⟨module⟩:⟨args⟩ -fplugin=⟨module⟩
221 -hide-all-plugin-packages -plugin-package ⟨pkg⟩ -plugin-pack‐
222 age-id ⟨pkg-id⟩
223 Profiling
225 -fno-prof-auto -fno-prof-cafs -fno-prof-count-entries
226 -fprof-auto -fprof-auto-calls -fprof-auto-exported
227 -fprof-auto-top -fprof-cafs -prof -ticky
228 Program coverage
230 -fhpc
231 Recompilation checking
233 -fforce-recomp -fignore-hpc-changes -fignore-optim-changes
234 Redirecting output
236 --exclude-module=⟨file⟩ -ddump-mod-cycles -dep-makefile ⟨file⟩
237 -dep-suffix ⟨suffix⟩ -dumpdir ⟨dir⟩ -hcsuf ⟨suffix⟩ -hidir ⟨dir⟩
238 -hiedir ⟨dir⟩ -hiesuf ⟨suffix⟩ -hisuf ⟨suffix⟩ -include-pkg-deps
239 -o ⟨file⟩ -odir ⟨dir⟩ -ohi ⟨file⟩ -osuf ⟨suffix⟩ -outputdir
240 ⟨dir⟩ -stubdir ⟨dir⟩
241 Temporary files
243 -tmpdir ⟨dir⟩
244 Verbosity options
246 -fabstract-refinement-hole-fits -fdiagnos‐
247 tics-color=⟨always|auto|never⟩ -fdiagnostics-show-caret -fer‐
248 ror-spans -fhide-source-paths -fmax-refinement-hole-fits=⟨n⟩
249 -fmax-relevant-binds=⟨n⟩ -fmax-valid-hole-fits=⟨n⟩
250 -fno-show-valid-hole-fits -fno-sort-valid-hole-fits
251 -fprint-equality-relations -fprint-expanded-synonyms
252 -fprint-explicit-coercions -fprint-explicit-foralls
253 -fprint-explicit-kinds -fprint-explicit-runtime-reps
254 -fprint-explicit-runtime-reps -fprint-potential-instances
255 -fprint-typechecker-elaboration -fprint-unicode-syntax -frefine‐
256 ment-level-hole-fits=⟨n⟩ -freverse-errors
257 -fshow-docs-of-hole-fits -fshow-hole-constraints
258 -fshow-hole-matches-of-hole-fits -fshow-provenance-of-hole-fits
259 -fshow-type-app-of-hole-fits -fshow-type-app-vars-of-hole-fits
260 -fshow-type-of-hole-fits -funclutter-valid-hole-fits -Rghc-tim‐
261 ing -v -v⟨n⟩
262 Warnings
264 -fdefer-out-of-scope-variables -fdefer-type-errors -fde‐
265 fer-typed-holes -fhelpful-errors -fmax-pmcheck-iterations=⟨n⟩
266 -fshow-warning-groups -W -w -Wall -Wall-missed-specialisations
267 -Wcompat -Wcpp-undef -Wdeferred-out-of-scope-variables -Wde‐
268 ferred-type-errors -Wdeprecated-flags -Wdeprecations
269 -Wdodgy-exports -Wdodgy-foreign-imports -Wdodgy-imports -Wdupli‐
270 cate-constraints -Wduplicate-exports -Wempty-enumerations -Wer‐
271 ror -Weverything -Whi-shadowing -Widentities -Wim‐
272 plicit-kind-vars -Wimplicit-prelude -Winaccessible-code -Wincom‐
273 plete-patterns -Wincomplete-record-updates -Wincomplete-uni-pat‐
274 terns -Winline-rule-shadowing -Wmissed-extra-shared-lib
275 -Wmissed-specialisations -Wmissing-deriving-strategies -Wmiss‐
276 ing-export-lists -Wmissing-exported-signatures -Wmiss‐
277 ing-exported-sigs -Wmissing-fields -Wmissing-home-modules
278 -Wmissing-import-lists -Wmissing-local-signatures -Wmiss‐
279 ing-local-sigs -Wmissing-methods -Wmissing-monadfail-instances
280 -Wmissing-pattern-synonym-signatures -Wmissing-signatures
281 -Wmonomorphism-restriction -Wname-shadowing -Wno-compat -Wnon‐
282 canonical-monad-instances -Wnoncanonical-monadfail-instances
283 -Wnoncanonical-monoid-instances -Worphans -Woverflowed-literals
284 -Woverlapping-patterns -Wpartial-fields -Wpartial-type-signa‐
285 tures -Wredundant-constraints -Wsafe -Wsemigroup -Wsimplifi‐
286 able-class-constraints -Wspace-after-bang -Wstar-binder
287 -Wstar-is-type -Wtabs -Wtrustworthy-safe -Wtype-defaults
288 -Wtyped-holes -Wunbanged-strict-patterns -Wunrecognised-pragmas
289 -Wunrecognised-warning-flags -Wunsafe -Wunsupported-calling-con‐
290 ventions -Wunsupported-llvm-version -Wunticked-promoted-con‐
291 structors -Wunused-binds -Wunused-do-bind -Wunused-foralls
292 -Wunused-imports -Wunused-local-binds -Wunused-matches
293 -Wunused-pattern-binds -Wunused-top-binds -Wunused-type-patterns
294 -Wwarn -Wwarnings-deprecations -Wwrong-do-bind
295 Code generation
297 -dynamic-too
298 Build dynamic object files as well as static object files during
299 compilation
300 -fasm Use the native code generator
302 -fbyte-code
304 Generate byte-code
305 -fexternal-dynamic-refs
307 Generate code for linking against dynamic libraries
308 -fllvm Compile using the LLVM code generator
310 -fno-code
312 Omit code generation
313 -fobject-code
315 Generate object code
316 -fPIC Generate position-independent code (where available)
318 -fPIE Generate code for a position-independent executable (where
320 available)
321 -fwrite-interface
323 Always write interface files
324 Debugging the compiler
326 -dcmm-lint
327 C-\- pass sanity checking
328 -dcore-lint
330 Turn on internal sanity checking
331 -ddump-asm
333 Dump final assembly
334 -ddump-asm-expanded
336 Dump the result of the synthetic instruction expansion pass.
337 -ddump-asm-liveness
339 Dump assembly augmented with register liveness
340 -ddump-asm-native
342 Dump initial assembly
343 -ddump-asm-regalloc
345 Dump the result of register allocation
346 -ddump-asm-regalloc-stages
348 Dump the build/spill stages of the -fregs-graph register alloca‐
349 tor.
350 -ddump-asm-stats
352 Dump statistics from the register allocator.
353 -ddump-bcos
355 Dump interpreter byte code
356 -ddump-cfg-weights
358 Dump the assumed weights of the CFG.
359 -ddump-cmm
361 Dump the final C-\- output
362 -ddump-cmm-caf
364 Dump the results of the C-\- CAF analysis pass.
365 -ddump-cmm-cbe
367 Dump the results of common block elimination
368 -ddump-cmm-cfg
370 Dump the results of the C-\- control flow optimisation pass.
371 -ddump-cmm-cps
373 Dump the results of the CPS pass
374 -ddump-cmm-from-stg
376 Dump STG-to-C-\- output
377 -ddump-cmm-info
379 Dump the results of the C-\- info table augmentation pass.
380 -ddump-cmm-proc
382 Dump the results of proc-point analysis
383 -ddump-cmm-procmap
385 Dump the results of the C-\- proc-point map pass.
386 -ddump-cmm-raw
388 Dump raw C-\-
389 -ddump-cmm-sink
391 Dump the results of the C-\- sinking pass.
392 -ddump-cmm-sp
394 Dump the results of the C-\- stack layout pass.
395 -ddump-cmm-split
397 Dump the results of the C-\- proc-point splitting pass.
398 -ddump-cmm-switch
400 Dump the results of switch lowering passes
401 -ddump-cmm-verbose
403 Show output from main C-\- pipeline passes
404 -ddump-core-stats
406 Print a one-line summary of the size of the Core program at the
407 end of the optimisation pipeline
408 -ddump-cse
410 Dump CSE output
411 -ddump-deriv
413 Dump deriving output
414 -ddump-ds
416 Dump desugarer output.
417 -ddump-ec-trace
419 Trace exhaustiveness checker
420 -ddump-file-prefix=⟨str⟩
422 Set the prefix of the filenames used for debugging output.
423 -ddump-foreign
425 Dump foreign export stubs
426 -ddump-hpc
428 An alias for -ddump-ticked.
429 -ddump-if-trace
431 Trace interface files
432 -ddump-inlinings
434 Dump inlining info
435 -ddump-json
437 Dump error messages as JSON documents
438 -ddump-llvm
440 Dump LLVM intermediate code.
441 -ddump-mod-map
443 Dump the state of the module mapping database.
444 -ddump-occur-anal
446 Dump occurrence analysis output
447 -ddump-opt-cmm
449 Dump the results of C-\- to C-\- optimising passes
450 -ddump-parsed
452 Dump parse tree
453 -ddump-parsed-ast
455 Dump parser output as a syntax tree
456 -ddump-prep
458 Dump prepared core
459 -ddump-rn
461 Dump renamer output
462 -ddump-rn-ast
464 Dump renamer output as a syntax tree
465 -ddump-rn-stats
467 Renamer stats
468 -ddump-rn-trace
470 Trace renamer
471 -ddump-rtti
473 Trace runtime type inference
474 -ddump-rule-firings
476 Dump rule firing info
477 -ddump-rule-rewrites
479 Dump detailed rule firing info
480 -ddump-rules
482 Dump rewrite rules
483 -ddump-simpl
485 Dump final simplifier output
486 -ddump-simpl-iterations
488 Dump output from each simplifier iteration
489 -ddump-simpl-stats
491 Dump simplifier stats
492 -ddump-spec
494 Dump specialiser output
495 -ddump-splices
497 Dump TH spliced expressions, and what they evaluate to
498 -ddump-stg
500 Dump final STG
501 -ddump-str-signatures
503 Dump strictness signatures
504 -ddump-stranal
506 Dump strictness analyser output
507 -ddump-tc
509 Dump typechecker output
510 -ddump-tc-ast
512 Dump typechecker output as a syntax tree
513 -ddump-tc-trace
515 Trace typechecker
516 -ddump-ticked
518 Dump the code instrumented by HPC (hpc).
519 -ddump-timings
521 Dump per-pass timing and allocation statistics
522 -ddump-to-file
524 Dump to files instead of stdout
525 -ddump-types
527 Dump type signatures
528 -ddump-worker-wrapper
530 Dump worker-wrapper output
531 -dfaststring-stats
533 Show statistics for fast string usage when finished
534 -dhex-word-literals
536 Print values of type Word# in hexadecimal.
537 -dinitial-unique=⟨s⟩
539 Start UniqSupply allocation from ⟨s⟩.
540 -dinline-check=⟨str⟩
542 Dump information about inlining decisions
543 -dno-debug-output
545 Suppress unsolicited debugging output
546 -dppr-case-as-let
548 Print single alternative case expressions as strict lets.
549 -dppr-cols=⟨n⟩
551 Set the width of debugging output. For example -dppr-cols200
552 -dppr-debug
554 Turn on debug printing (more verbose)
555 -dppr-user-length
557 Set the depth for printing expressions in error msgs
558 -drule-check=⟨str⟩
560 Dump information about potential rule application
561 -dshow-passes
563 Print out each pass name as it happens
564 -dstg-lint
566 STG pass sanity checking
567 -dsuppress-all
569 In dumps, suppress everything (except for uniques) that is sup‐
570 pressible.
571 -dsuppress-coercions
573 Suppress the printing of coercions in Core dumps to make them
574 shorter
575 -dsuppress-idinfo
577 Suppress extended information about identifiers where they are
578 bound
579 -dsuppress-module-prefixes
581 Suppress the printing of module qualification prefixes
582 -dsuppress-stg-free-vars
584 Suppress the printing of closure free variable lists in STG out‐
585 put
586 -dsuppress-ticks
588 Suppress "ticks" in the pretty-printer output.
589 -dsuppress-timestamps
591 Suppress timestamps in dumps
592 -dsuppress-type-applications
594 Suppress type applications
595 -dsuppress-type-signatures
597 Suppress type signatures
598 -dsuppress-unfoldings
600 Suppress the printing of the stable unfolding of a variable at
601 its binding site
602 -dsuppress-uniques
604 Suppress the printing of uniques in debug output (easier to use
605 diff)
606 -dsuppress-var-kinds
608 Suppress the printing of variable kinds
609 -dth-dec-file
611 Dump evaluated TH declarations into *.th.hs files
612 -dunique-increment=⟨i⟩
614 Set the increment for the generated Unique's to ⟨i⟩.
615 -dverbose-core2core
617 Show output from each core-to-core pass
618 -dverbose-stg2stg
620 Show output from each STG-to-STG pass
621 -falignment-sanitisation
623 Compile with alignment checks for all info table dereferences.
624 -fcatch-bottoms
626 Insert error expressions after bottoming expressions; useful
627 when debugging the compiler.
628 -fllvm-fill-undef-with-garbage
630 Intruct LLVM to fill dead STG registers with garbage
631 -fproc-alignment
633 Align functions at given boundary.
634 -g Produce DWARF debug information in compiled object files. ⟨n⟩
636 can be 0, 1, or 2, with higher numbers producing richer output.
637 If ⟨n⟩ is omitted, level 2 is assumed.
638 C pre-processor
640 -cpp Run the C pre-processor on Haskell source files
641 -D⟨symbol⟩[=⟨value⟩]
643 Define a symbol in the C pre-processor
644 -I⟨dir⟩
646 Add ⟨dir⟩ to the directory search list for #include files
647 -U⟨symbol⟩
649 Undefine a symbol in the C pre-processor
650 Finding imports
652 -i Empty the import directory list
653 -i⟨dir⟩[:⟨dir⟩]*
655 add ⟨dir⟩, ⟨dir2⟩, etc. to import path
656 Interactive mode
658 -fbreak-on-error
659 Break on uncaught exceptions and errors
660 -fbreak-on-exception
662 Break on any exception thrown
663 -fghci-hist-size=⟨n⟩
665 Set the number of entries GHCi keeps for :history. See
666 ghci-debugger.
667 -fghci-leak-check
669 (Debugging only) check for space leaks when loading new modules
670 in GHCi.
671 -flocal-ghci-history
673 Use current directory for the GHCi command history file
674 .ghci-history.
675 -fno-it
677 No longer set the special variable it.
678 -fprint-bind-result
680 Turn on printing of binding results in GHCi
681 -fshow-loaded-modules
683 Show the names of modules that GHCi loaded after a :load com‐
684 mand.
685 -ghci-script
687 Read additional .ghci files
688 -ignore-dot-ghci
690 Disable reading of .ghci files
691 -interactive-print ⟨expr⟩
693 Select the function to use for printing evaluated expressions in
694 GHCi
695 Interface files
697 --show-iface ⟨file⟩
698 See modes.
699 -ddump-hi
701 Dump the new interface to stdout
702 -ddump-hi-diffs
704 Show the differences vs. the old interface
705 -ddump-minimal-imports
707 Dump a minimal set of imports
708 Keeping intermediate files
710 -keep-hc-file
711 Retain intermediate .hc files.
712 -keep-hi-files
714 Retain intermediate .hi files (the default).
715 -keep-hscpp-file
717 Retain intermediate .hscpp files.
718 -keep-llvm-file
720 Retain intermediate LLVM .ll files. Implies -fllvm.
721 -keep-o-files
723 Retain intermediate .o files (the default).
724 -keep-s-file
726 Retain intermediate .s files.
727 -keep-tmp-files
729 Retain all intermediate temporary files.
730 Language options
732 -fno-safe-haskell
733 Disable Safe Haskell
734 -fsort-by-size-hole-fits
736 Sort valid hole fits by size.
737 -fsort-by-subsumption-hole-fits
739 Sort valid hole fits by subsumption.
740 -XAllowAmbiguousTypes
742 Allow the user to write ambiguous types, and the type inference
743 engine to infer them.
744 -XApplicativeDo
746 Enable Applicative do-notation desugaring
747 -XArrows
749 Enable arrow notation extension
750 -XBangPatterns
752 Enable bang patterns.
753 -XBinaryLiterals
755 Enable support for binary literals.
756 -XBlockArguments
758 Allow do blocks and other constructs as function arguments.
759 -XCApiFFI
761 Enable the CAPI calling convention.
762 -XConstrainedClassMethods
764 Enable constrained class methods.
765 -XConstraintKinds
767 Enable a kind of constraints.
768 -XCPP Enable the C preprocessor.
770 -XDataKinds
772 Enable datatype promotion.
773 -XDatatypeContexts
775 Allow contexts on data types.
776 -XDefaultSignatures
778 Enable default signatures.
779 -XDeriveAnyClass
781 Enable deriving for any class.
782 -XDeriveDataTypeable
784 Enable deriving for the Data class. Implied by (deprecated)
785 AutoDeriveTypeable.
786 -XDeriveFoldable
788 Enable deriving for the Foldable class. Implied by Derive‐
789 Traversable.
790 -XDeriveFunctor
792 Enable deriving for the Functor class. Implied by Derive‐
793 Traversable.
794 -XDeriveGeneric
796 Enable deriving for the Generic class.
797 -XDeriveLift
799 Enable deriving for the Lift class
800 -XDeriveTraversable
802 Enable deriving for the Traversable class. Implies DeriveFunc‐
803 tor and DeriveFoldable.
804 -XDerivingStrategies
806 Enables deriving strategies.
807 -XDerivingVia
809 Enable deriving instances via types of the same runtime repre‐
810 sentation. Implies DerivingStrategies.
811 -XDisambiguateRecordFields
813 Enable record field disambiguation. Implied by RecordWildCards.
814 -XDuplicateRecordFields
816 Allow definition of record types with identically-named fields.
817 -XEmptyCase
819 Allow empty case alternatives.
820 -XEmptyDataDecls
822 Allow definition of empty data types.
823 -XEmptyDataDeriving
825 Allow deriving instances of standard type classes for empty data
826 types.
827 -XExistentialQuantification
829 Enable liberalised type synonyms.
830 -XExplicitForAll
832 Enable explicit universal quantification. Implied by Scoped‐
833 TypeVariables, LiberalTypeSynonyms, RankNTypes and Existen‐
834 tialQuantification.
835 -XExplicitNamespaces
837 Enable using the keyword type to specify the namespace of
838 entries in imports and exports (explicit-namespaces). Implied
839 by TypeOperators and TypeFamilies.
840 -XExtendedDefaultRules
842 Use GHCi's extended default rules in a normal module.
843 -XFlexibleContexts
845 Enable flexible contexts. Implied by ImplicitParams.
846 -XFlexibleInstances
848 Enable flexible instances. Implies TypeSynonymInstances.
849 Implied by ImplicitParams.
850 -XForeignFunctionInterface
852 Enable foreign function interface.
853 -XFunctionalDependencies
855 Enable functional dependencies. Implies MultiParamTypeClasses.
856 -XGADTs
858 Enable generalised algebraic data types. Implies GADTSyntax and
859 MonoLocalBinds.
860 -XGADTSyntax
862 Enable generalised algebraic data type syntax.
863 -XGeneralisedNewtypeDeriving
865 Enable newtype deriving.
866 -XGeneralizedNewtypeDeriving
868 Enable newtype deriving.
869 -XHexFloatLiterals
871 Enable support for hexadecimal floating point literals.
872 -XImplicitParams
874 Enable Implicit Parameters. Implies FlexibleContexts and Flexi‐
875 bleInstances.
876 -XImpredicativeTypes
878 Enable impredicative types. Implies RankNTypes.
879 -XIncoherentInstances
881 Enable incoherent instances. Implies OverlappingInstances.
882 -XInstanceSigs
884 Enable instance signatures.
885 -XInterruptibleFFI
887 Enable interruptible FFI.
888 -XKindSignatures
890 Enable kind signatures. Implied by TypeFamilies and PolyKinds.
891 -XLambdaCase
893 Enable lambda-case expressions.
894 -XLiberalTypeSynonyms
896 Enable liberalised type synonyms.
897 -XMagicHash
899 Allow # as a postfix modifier on identifiers.
900 -XMonadComprehensions
902 Enable monad comprehensions.
903 -XMonadFailDesugaring
905 Enable monadfail desugaring.
906 -XMonoLocalBinds
908 Enable do not generalise local bindings. Implied by TypeFami‐
909 lies and GADTs.
910 -XMultiParamTypeClasses
912 Enable multi parameter type classes. Implied by FunctionalDe‐
913 pendencies.
914 -XMultiWayIf
916 Enable multi-way if-expressions.
917 -XNamedFieldPuns
919 Enable record puns.
920 -XNamedWildCards
922 Enable named wildcards.
923 -XNegativeLiterals
925 Enable support for negative literals.
926 -XNoImplicitPrelude
928 Don't implicitly import Prelude. Implied by RebindableSyntax.
929 -XNoMonomorphismRestriction
931 Disable the monomorphism restriction.
932 -XNoPatternGuards
934 Disable pattern guards. Implied by Haskell98.
935 -XNoTraditionalRecordSyntax
937 Disable support for traditional record syntax (as supported by
938 Haskell 98) C {f = x}
939 -XNPlusKPatterns
941 Enable support for n+k patterns. Implied by Haskell98.
942 -XNullaryTypeClasses
944 Deprecated, does nothing. nullary (no parameter) type classes
945 are now enabled using MultiParamTypeClasses.
946 -XNumDecimals
948 Enable support for 'fractional' integer literals.
949 -XNumericUnderscores
951 Enable support for numeric underscores.
952 -XOverlappingInstances
954 Enable overlapping instances.
955 -XOverloadedLabels
957 Enable overloaded labels.
958 -XOverloadedLists
960 Enable overloaded lists.
961 -XOverloadedStrings
963 Enable overloaded string literals.
964 -XPackageImports
966 Enable package-qualified imports.
967 -XParallelListComp
969 Enable parallel list comprehensions.
970 -XPartialTypeSignatures
972 Enable partial type signatures.
973 -XPatternSynonyms
975 Enable pattern synonyms.
976 -XPolyKinds
978 Enable kind polymorphism. Implies KindSignatures.
979 -XPostfixOperators
981 Enable postfix operators.
982 -XQuantifiedConstraints
984 Allow forall quantifiers in constraints.
985 -XQuasiQuotes
987 Enable quasiquotation.
988 -XRank2Types
990 Enable rank-2 types. Synonym for RankNTypes.
991 -XRankNTypes
993 Enable rank-N types. Implied by ImpredicativeTypes.
994 -XRebindableSyntax
996 Employ rebindable syntax. Implies NoImplicitPrelude.
997 -XRecordWildCards
999 Enable record wildcards. Implies DisambiguateRecordFields.
1000 -XRecursiveDo
1002 Enable recursive do (mdo) notation.
1003 -XRoleAnnotations
1005 Enable role annotations.
1006 -XSafe Enable the Safe Haskell Safe mode.
1008 -XScopedTypeVariables
1010 Enable lexically-scoped type variables.
1011 -XStandaloneDeriving
1013 Enable standalone deriving.
1014 -XStarIsType
1016 Treat * as Data.Kind.Type.
1017 -XStaticPointers
1019 Enable static pointers.
1020 -XStrict
1022 Make bindings in the current module strict by default.
1023 -XStrictData
1025 Enable default strict datatype fields.
1026 -XTemplateHaskell
1028 Enable Template Haskell.
1029 -XTemplateHaskellQuotes
1031 Enable quotation subset of Template Haskell.
1032 -XTransformListComp
1034 Enable generalised list comprehensions.
1035 -XTrustworthy
1037 Enable the Safe Haskell Trustworthy mode.
1038 -XTupleSections
1040 Enable tuple sections.
1041 -XTypeApplications
1043 Enable type application syntax in terms and types.
1044 -XTypeFamilies
1046 Enable type families. Implies ExplicitNamespaces, KindSigna‐
1047 tures, and MonoLocalBinds.
1048 -XTypeFamilyDependencies
1050 Enable injective type families. Implies TypeFamilies.
1051 -XTypeInType
1053 Deprecated. Enable kind polymorphism and datatype promotion.
1054 -XTypeOperators
1056 Enable type operators. Implies ExplicitNamespaces.
1057 -XTypeSynonymInstances
1059 Enable type synonyms in instance heads. Implied by FlexibleIn‐
1060 stances.
1061 -XUnboxedSums
1063 Enable unboxed sums.
1064 -XUnboxedTuples
1066 Enable the use of unboxed tuple syntax.
1067 -XUndecidableInstances
1069 Enable undecidable instances.
1070 -XUndecidableSuperClasses
1072 Allow all superclass constraints, including those that may
1073 result in non-termination of the typechecker.
1074 -XUnicodeSyntax
1076 Enable unicode syntax.
1077 -XUnsafe
1079 Enable Safe Haskell Unsafe mode.
1080 -XViewPatterns
1082 Enable view patterns.
1083 Linking options
1085 -c Stop after generating object (.o) file
1086 -debug Use the debugging runtime
1088 -dylib-install-name ⟨path⟩
1090 Set the install name (via -install_name passed to Apple's
1091 linker), specifying the full install path of the library file.
1092 Any libraries or executables that link with it later will pick
1093 up that path as their runtime search location for it. (Dar‐
1094 win/OS X only)
1095 -dynamic
1097 Build dynamically-linked object files and executables
1098 -dynload
1100 Selects one of a number of modes for finding shared libraries at
1101 runtime.
1102 -eventlog
1104 Enable runtime event tracing
1105 -fno-embed-manifest
1107 Do not embed the manifest in the executable (Windows only)
1108 -fno-gen-manifest
1110 Do not generate a manifest file (Windows only)
1111 -fno-shared-implib
1113 Don't generate an import library for a DLL (Windows only)
1114 -framework ⟨name⟩
1116 On Darwin/OS X/iOS only, link in the framework ⟨name⟩. This
1117 option corresponds to the -framework option for Apple's Linker.
1118 -framework-path ⟨dir⟩
1120 On Darwin/OS X/iOS only, add ⟨dir⟩ to the list of directories
1121 searched for frameworks. This option corresponds to the -F
1122 option for Apple's Linker.
1123 -fwhole-archive-hs-libs
1125 When linking a binary executable, this inserts the flag
1126 -Wl,--whole-archive before any -l flags for Haskell libraries,
1127 and -Wl,--no-whole-archive afterwards
1128 -keep-cafs
1130 Do not garbage-collect CAFs (top-level expressions) at runtime
1131 -L ⟨dir⟩
1133 Add ⟨dir⟩ to the list of directories searched for libraries
1134 -l ⟨lib⟩
1136 Link in library ⟨lib⟩
1137 -main-is ⟨thing⟩
1139 Set main module and function
1140 -no-hs-main
1142 Don't assume this program contains main
1143 -no-rtsopts-suggestions
1145 Don't print RTS suggestions about linking with
1146 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩].
1147 -package ⟨name⟩
1149 Expose package ⟨pkg⟩
1150 -pie Instruct the linker to produce a position-independent exe‐
1152 cutable.
1153 -rdynamic
1155 This instructs the linker to add all symbols, not only used
1156 ones, to the dynamic symbol table. Currently Linux and Win‐
1157 dows/MinGW32 only. This is equivalent to using -optl -rdynamic
1158 on Linux, and -optl -export-all-symbols on Windows.
1159 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩]
1161 Control whether the RTS behaviour can be tweaked via com‐
1162 mand-line flags and the GHCRTS environment variable. Using none
1163 means no RTS flags can be given; some means only a minimum of
1164 safe options can be given (the default); all (or no argument at
1165 all) means that all RTS flags are permitted; ignore means RTS
1166 flags can be given, but are treated as regular arguments and
1167 passed to the Haskell program as arguments; ignoreAll is the
1168 same as ignore, but GHCRTS is also ignored. -rtsopts does not
1169 affect -with-rtsopts behavior; flags passed via -with-rtsopts
1170 are used regardless of -rtsopts.
1171 -shared
1173 Generate a shared library (as opposed to an executable)
1174 -split-objs
1176 Split objects (for libraries)
1177 -split-sections
1179 Split sections for link-time dead-code stripping
1180 -static
1182 Use static Haskell libraries
1183 -staticlib
1185 Generate a standalone static library (as opposed to an exe‐
1186 cutable). This is useful when cross compiling. The library
1187 together with all its dependencies ends up in in a single static
1188 library that can be linked against.
1189 -threaded
1191 Use the threaded runtime
1192 -with-rtsopts=⟨opts⟩
1194 Set the default RTS options to ⟨opts⟩.
1195 Miscellaneous options
1197 -fexternal-interpreter
1198 Run interpreted code in a separate process
1199 -fglasgow-exts
1201 Deprecated. Enable most language extensions; see options-lan‐
1202 guage for exactly which ones.
1203 -ghcversion-file ⟨path to ghcversion.h⟩
1205 (GHC as a C compiler only) Use this ghcversion.h file
1206 -H ⟨size⟩
1208 Set the minimum size of the heap to ⟨size⟩
1209 -j[⟨n⟩]
1211 When compiling with --make, compile ⟨n⟩ modules in parallel.
1212 Modes of operation
1214 --frontend ⟨module⟩
1215 run GHC with the given frontend plugin; see frontend_plugins for
1216 details.
1217 --help Display help
1219 --info display information about the compiler
1221 --interactive
1223 Interactive mode - normally used by just running ghci; see ghci
1224 for details.
1225 --make Build a multi-module Haskell program, automatically figuring out
1227 dependencies. Likely to be much easier, and faster, than using
1228 make; see make-mode for details.
1229 --mk-dll
1231 DLL-creation mode (Windows only)
1232 --numeric-version
1234 display GHC version (numeric only)
1235 --print-libdir
1237 display GHC library directory
1238 --show-iface ⟨file⟩
1240 display the contents of an interface file.
1241 --show-options
1243 display the supported command line options
1244 --supported-extensions
1246 display the supported language extensions
1247 --version
1249 display GHC version
1250 -e ⟨expr⟩
1252 Evaluate expr; see eval-mode for details.
1253 -M generate dependency information suitable for use in a Makefile;
1255 see makefile-dependencies for details.
1256 Individual optimizations
1258 -fasm-shortcutting
1259 Enable shortcutting on assembly. Implied by -O2.
1260 -fblock-layout-cfg
1262 Use the new cfg based block layout algorithm.
1263 -fblock-layout-weightless
1265 Ignore cfg weights for code layout.
1266 -fblock-layout-weights
1268 Sets edge weights used by the new code layout algorithm.
1269 -fcall-arity
1271 Enable call-arity optimisation. Implied by -O.
1272 -fcase-folding
1274 Enable constant folding in case expressions. Implied by -O.
1275 -fcase-merge
1277 Enable case-merging. Implied by -O.
1278 -fcmm-elim-common-blocks
1280 Enable Cmm common block elimination. Implied by -O.
1281 -fcmm-sink
1283 Enable Cmm sinking. Implied by -O.
1284 -fcpr-anal
1286 Turn on CPR analysis in the demand analyser. Implied by -O.
1287 -fcross-module-specialise
1289 Turn on specialisation of overloaded functions imported from
1290 other modules.
1291 -fcse Enable common sub-expression elimination. Implied by -O.
1293 -fdicts-cheap
1295 Make dictionary-valued expressions seem cheap to the optimiser.
1296 -fdicts-strict
1298 Make dictionaries strict
1299 -fdmd-tx-dict-sel
1301 Use a special demand transformer for dictionary selectors.
1302 Always enabled by default.
1303 -fdo-eta-reduction
1305 Enable eta-reduction. Implied by -O.
1306 -fdo-lambda-eta-expansion
1308 Enable lambda eta-expansion. Always enabled by default.
1309 -feager-blackholing
1311 Turn on eager blackholing
1312 -fenable-rewrite-rules
1314 Switch on all rewrite rules (including rules generated by auto‐
1315 matic specialisation of overloaded functions). Implied by -O.
1316 -fexcess-precision
1318 Enable excess intermediate precision
1319 -fexitification
1321 Enables exitification optimisation. Implied by -O.
1322 -fexpose-all-unfoldings
1324 Expose all unfoldings, even for very large or recursive func‐
1325 tions.
1326 -ffloat-in
1328 Turn on the float-in transformation. Implied by -O.
1329 -ffull-laziness
1331 Turn on full laziness (floating bindings outwards). Implied by
1332 -O.
1333 -ffun-to-thunk
1335 Allow worker-wrapper to convert a function closure into a thunk
1336 if the function does not use any of its arguments. Off by
1337 default.
1338 -fignore-asserts
1340 Ignore assertions in the source. Implied by -O.
1341 -fignore-interface-pragmas
1343 Ignore pragmas in interface files. Implied by -O0 only.
1344 -flate-dmd-anal
1346 Run demand analysis again, at the end of the simplification
1347 pipeline
1348 -flate-specialise
1350 Run a late specialisation pass
1351 -fliberate-case
1353 Turn on the liberate-case transformation. Implied by -O2.
1354 -fliberate-case-threshold=⟨n⟩
1356 default: 2000. Set the size threshold for the liberate-case
1357 transformation to ⟨n⟩
1358 -fllvm-pass-vectors-in-regs
1360 Pass vector value in vector registers for function calls
1361 -floopification
1363 Turn saturated self-recursive tail-calls into local jumps in the
1364 generated assembly. Implied by -O.
1365 -fmax-inline-alloc-size=⟨n⟩
1367 default: 128. Set the maximum size of inline array allocations
1368 to ⟨n⟩ bytes (default: 128).
1369 -fmax-inline-memcpy-insns=⟨n⟩
1371 default: 32. Inline memcpy calls if they would generate no more
1372 than ⟨n⟩ pseudo instructions.
1373 -fmax-inline-memset-insns=⟨n⟩
1375 default: 32. Inline memset calls if they would generate no more
1376 than ⟨n⟩ pseudo instructions
1377 -fmax-simplifier-iterations=⟨n⟩
1379 default: 4. Set the max iterations for the simplifier.
1380 -fmax-uncovered-patterns=⟨n⟩
1382 default: 4. Set the maximum number of patterns to display in
1383 warnings about non-exhaustive ones.
1384 -fmax-worker-args=⟨n⟩
1386 default: 10. If a worker has that many arguments, none will be
1387 unpacked anymore.
1388 -fno-opt-coercion
1390 Turn off the coercion optimiser
1391 -fno-pre-inlining
1393 Turn off pre-inlining
1394 -fno-state-hack
1396 Turn off the state hackwhereby any lambda with a real-world
1397 state token as argument is considered to be single-entry. Hence
1398 OK to inline things inside it.
1399 -fomit-interface-pragmas
1401 Don't generate interface pragmas. Implied by -O0 only.
1402 -fomit-yields
1404 Omit heap checks when no allocation is being performed.
1405 -foptimal-applicative-do
1407 Use a slower but better algorithm for ApplicativeDo
1408 -fpedantic-bottoms
1410 Make GHC be more precise about its treatment of bottom (but see
1411 also -fno-state-hack). In particular, GHC will not eta-expand
1412 through a case expression.
1413 -fregs-graph
1415 Use the graph colouring register allocator for register alloca‐
1416 tion in the native code generator. Implied by -O2.
1417 -fregs-iterative
1419 Use the iterative coalescing graph colouring register allocator
1420 in the native code generator.
1421 -fsimpl-tick-factor=⟨n⟩
1423 default: 100. Set the percentage factor for simplifier ticks.
1424 -fsimplifier-phases=⟨n⟩
1426 default: 2. Set the number of phases for the simplifier.
1427 Ignored with -O0.
1428 -fsolve-constant-dicts
1430 When solving constraints, try to eagerly solve super classes
1431 using available dictionaries.
1432 -fspec-constr
1434 Turn on the SpecConstr transformation. Implied by -O2.
1435 -fspec-constr-count=⟨n⟩
1437 default: 3.* Set to ⟨n⟩ the maximum number of specialisations
1438 that will be created for any one function by the SpecConstr
1439 transformation.
1440 -fspec-constr-keen
1442 Specialize a call with an explicit constructor argument, even if
1443 the argument is not scrutinised in the body of the function
1444 -fspec-constr-threshold=⟨n⟩
1446 default: 2000. Set the size threshold for the SpecConstr trans‐
1447 formation to ⟨n⟩.
1448 -fspecialise
1450 Turn on specialisation of overloaded functions. Implied by -O.
1451 -fspecialise-aggressively
1453 Turn on specialisation of overloaded functions regardless of
1454 size, if unfolding is available
1455 -fstatic-argument-transformation
1457 Turn on the static argument transformation.
1458 -fstg-cse
1460 Enable common sub-expression elimination on the STG intermediate
1461 language
1462 -fstg-lift-lams
1464 Enable late lambda lifting on the STG intermediate language.
1465 Implied by -O2.
1466 -fstg-lift-lams-known
1468 Allow turning known into unknown calls while performing late
1469 lambda lifting.
1470 -fstg-lift-lams-non-rec-args
1472 Create top-level non-recursive functions with at most <n> param‐
1473 eters while performing late lambda lifting.
1474 -fstg-lift-lams-rec-args
1476 Create top-level recursive functions with at most <n> parameters
1477 while performing late lambda lifting.
1478 -fstrictness
1480 Turn on strictness analysis. Implied by -O. Implies
1481 -fworker-wrapper
1482 -fstrictness-before=⟨n⟩
1484 Run an additional strictness analysis before simplifier phase
1485 ⟨n⟩
1486 -funbox-small-strict-fields
1488 Flatten strict constructor fields with a pointer-sized represen‐
1489 tation. Implied by -O.
1490 -funbox-strict-fields
1492 Flatten strict constructor fields
1493 -funfolding-creation-threshold=⟨n⟩
1495 default: 750. Tweak unfolding settings.
1496 -funfolding-dict-discount=⟨n⟩
1498 default: 30. Tweak unfolding settings.
1499 -funfolding-fun-discount=⟨n⟩
1501 default: 60. Tweak unfolding settings.
1502 -funfolding-keeness-factor=⟨n⟩
1504 default: 1.5. Tweak unfolding settings.
1505 -funfolding-use-threshold=⟨n⟩
1507 default: 60. Tweak unfolding settings.
1508 Optimization levels
1510 -O Enable level 1 optimisations
1511 -O0 Disable optimisations (default)
1513 -O2 Enable level 2 optimisations
1515 Package options
1517 -clear-package-db
1518 Clear the package db stack.
1519 -distrust ⟨pkg⟩
1521 Expose package ⟨pkg⟩ and set it to be distrusted. See
1522 safe-haskell.
1523 -distrust-all-packages
1525 Distrust all packages by default. See safe-haskell.
1526 -fpackage-trust
1528 Enable Safe Haskell trusted package requirement for trustworthy
1529 modules.
1530 -global-package-db
1532 Add the global package db to the stack.
1533 -hide-all-packages
1535 Hide all packages by default
1536 -hide-package ⟨pkg⟩
1538 Hide package ⟨pkg⟩
1539 -ignore-package ⟨pkg⟩
1541 Ignore package ⟨pkg⟩
1542 -no-auto-link-packages
1544 Don't automatically link in the base and rts packages.
1545 -no-global-package-db
1547 Remove the global package db from the stack.
1548 -no-user-package-db
1550 Remove the user's package db from the stack.
1551 -package ⟨pkg⟩
1553 Expose package ⟨pkg⟩
1554 -package-db ⟨file⟩
1556 Add ⟨file⟩ to the package db stack.
1557 -package-env ⟨file⟩|⟨name⟩
1559 Use the specified package environment.
1560 -package-id ⟨unit-id⟩
1562 Expose package by id ⟨unit-id⟩
1563 -this-unit-id ⟨unit-id⟩
1565 Compile to be part of unit (i.e. package) ⟨unit-id⟩
1566 -trust ⟨pkg⟩
1568 Expose package ⟨pkg⟩ and set it to be trusted. See safe-haskell.
1569 -user-package-db
1571 Add the user's package db to the stack.
1572 Phases of compilation
1574 -C Stop after generating C (.hc file)
1575 -c Stop after generating object (.o) file
1577 -E Stop after preprocessing (.hspp file)
1579 -F Enable the use of a pre-processor (set with -pgmF ⟨cmd⟩)
1581 -S Stop after generating assembly (.s file)
1583 -x ⟨suffix⟩
1585 Override default behaviour for source files
1586 Overriding external programs
1588 -pgma ⟨cmd⟩
1589 Use ⟨cmd⟩ as the assembler
1590 -pgmc ⟨cmd⟩
1592 Use ⟨cmd⟩ as the C compiler
1593 -pgmdll ⟨cmd⟩
1595 Use ⟨cmd⟩ as the DLL generator
1596 -pgmF ⟨cmd⟩
1598 Use ⟨cmd⟩ as the pre-processor (with -F only)
1599 -pgmi ⟨cmd⟩
1601 Use ⟨cmd⟩ as the external interpreter command.
1602 -pgmL ⟨cmd⟩
1604 Use ⟨cmd⟩ as the literate pre-processor
1605 -pgml ⟨cmd⟩
1607 Use ⟨cmd⟩ as the linker
1608 -pgmlc ⟨cmd⟩
1610 Use ⟨cmd⟩ as the LLVM compiler
1611 -pgmlibtool ⟨cmd⟩
1613 Use ⟨cmd⟩ as the command for libtool (with -staticlib only).
1614 -pgmlo ⟨cmd⟩
1616 Use ⟨cmd⟩ as the LLVM optimiser
1617 -pgmP ⟨cmd⟩
1619 Use ⟨cmd⟩ as the C pre-processor (with -cpp only)
1620 -pgms ⟨cmd⟩
1622 Use ⟨cmd⟩ as the splitter
1623 -pgmwindres ⟨cmd⟩
1625 Use ⟨cmd⟩ as the program for embedding manifests on Windows.
1626 Phase-specific options
1628 -opta ⟨option⟩
1629 pass ⟨option⟩ to the assembler
1630 -optc ⟨option⟩
1632 pass ⟨option⟩ to the C compiler
1633 -optdll ⟨option⟩
1635 pass ⟨option⟩ to the DLL generator
1636 -optF ⟨option⟩
1638 pass ⟨option⟩ to the custom pre-processor
1639 -opti ⟨option⟩
1641 pass ⟨option⟩ to the interpreter sub-process.
1642 -optL ⟨option⟩
1644 pass ⟨option⟩ to the literate pre-processor
1645 -optl ⟨option⟩
1647 pass ⟨option⟩ to the linker
1648 -optlc ⟨option⟩
1650 pass ⟨option⟩ to the LLVM compiler
1651 -optlo ⟨option⟩
1653 pass ⟨option⟩ to the LLVM optimiser
1654 -optP ⟨option⟩
1656 pass ⟨option⟩ to cpp (with -cpp only)
1657 -optwindres ⟨option⟩
1659 pass ⟨option⟩ to windres.
1660 Platform-specific options
1662 -msse2 (x86 only) Use SSE2 for floating-point operations
1663 -msse4.2
1665 (x86 only) Use SSE4.2 for floating-point operations
1666 Compiler plugins
1668 -fclear-plugins
1669 Clear the list of active plugins
1670 -fplugin-opt=⟨module⟩:⟨args⟩
1672 Give arguments to a plugin module; module must be specified with
1673 -fplugin=⟨module⟩
1674 -fplugin=⟨module⟩
1676 Load a plugin exported by a given module
1677 -hide-all-plugin-packages
1679 Hide all packages for plugins by default
1680 -plugin-package ⟨pkg⟩
1682 Expose ⟨pkg⟩ for plugins
1683 -plugin-package-id ⟨pkg-id⟩
1685 Expose ⟨pkg-id⟩ for plugins
1686 Profiling
1688 -fno-prof-auto
1689 Disables any previous -fprof-auto, -fprof-auto-top, or
1690 -fprof-auto-exported options.
1691 -fno-prof-cafs
1693 Disables any previous -fprof-cafs option.
1694 -fno-prof-count-entries
1696 Do not collect entry counts
1697 -fprof-auto
1699 Auto-add SCC\ s to all bindings not marked INLINE
1700 -fprof-auto-calls
1702 Auto-add SCC\ s to all call sites
1703 -fprof-auto-exported
1705 Auto-add SCC\ s to all exported bindings not marked INLINE
1706 -fprof-auto-top
1708 Auto-add SCC\ s to all top-level bindings not marked INLINE
1709 -fprof-cafs
1711 Auto-add SCC\ s to all CAFs
1712 -prof Turn on profiling
1714 -ticky Turn on ticky-ticky profiling
1716 Program coverage
1718 -fhpc Turn on Haskell program coverage instrumentation
1719 Recompilation checking
1721 -fforce-recomp
1722 Turn off recompilation checking. This is implied by any -ddump-X
1723 option when compiling a single file (i.e. when using -c).
1724 -fignore-hpc-changes
1726 Do not recompile modules just to match changes to HPC flags.
1727 This is especially useful for avoiding recompilation when using
1728 GHCi, and is enabled by default for GHCi.
1729 -fignore-optim-changes
1731 Do not recompile modules just to match changes to optimisation
1732 flags. This is especially useful for avoiding recompilation when
1733 using GHCi, and is enabled by default for GHCi.
1734 Redirecting output
1736 --exclude-module=⟨file⟩
1737 Regard ⟨file⟩ as "stable"; i.e., exclude it from having depen‐
1738 dencies on it.
1739 -ddump-mod-cycles
1741 Dump module cycles
1742 -dep-makefile ⟨file⟩
1744 Use ⟨file⟩ as the makefile
1745 -dep-suffix ⟨suffix⟩
1747 Make dependencies that declare that files with suffix
1748 .⟨suf⟩⟨osuf⟩ depend on interface files with suffix .⟨suf⟩hi
1749 -dumpdir ⟨dir⟩
1751 redirect dump files
1752 -hcsuf ⟨suffix⟩
1754 set the suffix to use for intermediate C files
1755 -hidir ⟨dir⟩
1757 set directory for interface files
1758 -hiedir ⟨dir⟩
1760 set directory for extended interface files
1761 -hiesuf ⟨suffix⟩
1763 set the suffix to use for extended interface files
1764 -hisuf ⟨suffix⟩
1766 set the suffix to use for interface files
1767 -include-pkg-deps
1769 Regard modules imported from packages as unstable
1770 -o ⟨file⟩
1772 set output filename
1773 -odir ⟨dir⟩
1775 set directory for object files
1776 -ohi ⟨file⟩
1778 set the filename in which to put the interface
1779 -osuf ⟨suffix⟩
1781 set the output file suffix
1782 -outputdir ⟨dir⟩
1784 set output directory
1785 -stubdir ⟨dir⟩
1787 redirect FFI stub files
1788 Temporary files
1790 -tmpdir ⟨dir⟩
1791 set the directory for temporary files
1792 Verbosity options
1794 -fabstract-refinement-hole-fits
1795 default: off. Toggles whether refinements where one or more of
1796 the holes are abstract are reported.
1797 -fdiagnostics-color=⟨always|auto|never⟩
1799 Use colors in error messages
1800 -fdiagnostics-show-caret
1802 Whether to show snippets of original source code
1803 -ferror-spans
1805 Output full span in error messages
1806 -fhide-source-paths
1808 hide module source and object paths
1809 -fmax-refinement-hole-fits=⟨n⟩
1811 default: 6. Set the maximum number of refinement hole fits for
1812 typed holes to display in type error messages.
1813 -fmax-relevant-binds=⟨n⟩
1815 default: 6. Set the maximum number of bindings to display in
1816 type error messages.
1817 -fmax-valid-hole-fits=⟨n⟩
1819 default: 6. Set the maximum number of valid hole fits for typed
1820 holes to display in type error messages.
1821 -fno-show-valid-hole-fits
1823 Disables showing a list of valid hole fits for typed holes in
1824 type error messages.
1825 -fno-sort-valid-hole-fits
1827 Disables the sorting of the list of valid hole fits for typed
1828 holes in type error messages.
1829 -fprint-equality-relations
1831 Distinguish between equality relations when printing
1832 -fprint-expanded-synonyms
1834 In type errors, also print type-synonym-expanded types.
1835 -fprint-explicit-coercions
1837 Print coercions in types
1838 -fprint-explicit-foralls
1840 Print explicit forall quantification in types. See also -XEx‐
1841 plicitForAll
1842 -fprint-explicit-kinds
1844 Print explicit kind foralls and kind arguments in types. See
1845 also -XKindSignatures
1846 -fprint-explicit-runtime-reps
1848 Print RuntimeRep variables in types which are runtime-represen‐
1849 tation polymorphic.
1850 -fprint-explicit-runtime-reps
1852 Print RuntimeRep variables in types which are runtime-represen‐
1853 tation polymorphic.
1854 -fprint-potential-instances
1856 display all available instances in type error messages
1857 -fprint-typechecker-elaboration
1859 Print extra information from typechecker.
1860 -fprint-unicode-syntax
1862 Use unicode syntax when printing expressions, types and kinds.
1863 See also -XUnicodeSyntax
1864 -frefinement-level-hole-fits=⟨n⟩
1866 default: off. Sets the level of refinement of the refinement
1867 hole fits, where level n means that hole fits of up to n holes
1868 will be considered.
1869 -freverse-errors
1871 Output errors in reverse order
1872 -fshow-docs-of-hole-fits
1874 Toggles whether to show the documentation of the valid hole fits
1875 in the output.
1876 -fshow-hole-constraints
1878 Show constraints when reporting typed holes.
1879 -fshow-hole-matches-of-hole-fits
1881 Toggles whether to show the type of the additional holes in
1882 refinement hole fits.
1883 -fshow-provenance-of-hole-fits
1885 Toggles whether to show the provenance of the valid hole fits in
1886 the output.
1887 -fshow-type-app-of-hole-fits
1889 Toggles whether to show the type application of the valid hole
1890 fits in the output.
1891 -fshow-type-app-vars-of-hole-fits
1893 Toggles whether to show what type each quantified variable takes
1894 in a valid hole fit.
1895 -fshow-type-of-hole-fits
1897 Toggles whether to show the type of the valid hole fits in the
1898 output.
1899 -funclutter-valid-hole-fits
1901 Unclutter the list of valid hole fits by not showing provenance
1902 nor type applications of suggestions.
1903 -Rghc-timing
1905 Summarise timing stats for GHC (same as +RTS -tstderr).
1906 -v verbose mode (equivalent to -v3)
1908 -v⟨n⟩ set verbosity level
1910 Warnings
1912 -fdefer-out-of-scope-variables
1913 Convert variable out of scope variables errors into warnings.
1914 Implied by -fdefer-type-errors. See also -Wde‐
1915 ferred-out-of-scope-variables.
1916 -fdefer-type-errors
1918 Turn type errors into warnings, deferring the error until run‐
1919 time. Implies -fdefer-typed-holes and -fdefer-out-of-scope-vari‐
1920 ables. See also -Wdeferred-type-errors
1921 -fdefer-typed-holes
1923 Convert typed hole errors into warnings, deferring the error
1924 until runtime. Implied by -fdefer-type-errors. See also
1925 -Wtyped-holes.
1926 -fhelpful-errors
1928 Make suggestions for mis-spelled names.
1929 -fmax-pmcheck-iterations=⟨n⟩
1931 the iteration limit for the pattern match checker
1932 -fshow-warning-groups
1934 show which group an emitted warning belongs to.
1935 -W enable normal warnings
1937 -w disable all warnings
1939 -Wall enable almost all warnings (details in options-sanity)
1941 -Wall-missed-specialisations
1943 warn when specialisation of any overloaded function fails.
1944 -Wcompat
1946 enable future compatibility warnings (details in options-sanity)
1947 -Wcpp-undef
1949 warn on uses of the #if directive on undefined identifiers
1950 -Wdeferred-out-of-scope-variables
1952 Report warnings when variable out-of-scope errors are deferred
1953 until runtime. See -fdefer-out-of-scope-variables.
1954 -Wdeferred-type-errors
1956 Report warnings when deferred type errors are enabled. This
1957 option is enabled by default. See -fdefer-type-errors.
1958 -Wdeprecated-flags
1960 warn about uses of commandline flags that are deprecated
1961 -Wdeprecations
1963 warn about uses of functions & types that have warnings or dep‐
1964 recated pragmas. Alias for -Wwarnings-deprecations
1965 -Wdodgy-exports
1967 warn about dodgy exports
1968 -Wdodgy-foreign-imports
1970 warn about dodgy foreign imports
1971 -Wdodgy-imports
1973 warn about dodgy imports
1974 -Wduplicate-constraints
1976 warn when a constraint appears duplicated in a type signature
1977 -Wduplicate-exports
1979 warn when an entity is exported multiple times
1980 -Wempty-enumerations
1982 warn about enumerations that are empty
1983 -Werror
1985 make warnings fatal
1986 -Weverything
1988 enable all warnings supported by GHC
1989 -Whi-shadowing
1991 warn when a .hi file in the current directory shadows a library
1992 -Widentities
1994 warn about uses of Prelude numeric conversions that are probably
1995 the identity (and hence could be omitted)
1996 -Wimplicit-kind-vars
1998 warn when kind variables are brought into scope implicitly
1999 despite the "forall-or-nothing" rule
2000 -Wimplicit-prelude
2002 warn when the Prelude is implicitly imported
2003 -Winaccessible-code
2005 warn about inaccessible code
2006 -Wincomplete-patterns
2008 warn when a pattern match could fail
2009 -Wincomplete-record-updates
2011 warn when a record update could fail
2012 -Wincomplete-uni-patterns
2014 warn when a pattern match in a lambda expression or pattern
2015 binding could fail
2016 -Winline-rule-shadowing
2018 Warn if a rewrite RULE might fail to fire because the function
2019 might be inlined before the rule has a chance to fire. See
2020 rules-inline.
2021 -Wmissed-extra-shared-lib
2023 Warn when GHCi can't load a shared lib.
2024 -Wmissed-specialisations
2026 warn when specialisation of an imported, overloaded function
2027 fails.
2028 -Wmissing-deriving-strategies
2030 warn when a deriving clause is missing a deriving strategy
2031 -Wmissing-export-lists
2033 warn when a module declaration does not explicitly list all
2034 exports
2035 -Wmissing-exported-signatures
2037 warn about top-level functions without signatures, only if they
2038 are exported. takes precedence over -Wmissing-signatures
2039 -Wmissing-exported-sigs
2041 (deprecated) warn about top-level functions without signatures,
2042 only if they are exported. takes precedence over -Wmissing-sig‐
2043 natures
2044 -Wmissing-fields
2046 warn when fields of a record are uninitialised
2047 -Wmissing-home-modules
2049 warn when encountering a home module imported, but not listed on
2050 the command line. Useful for cabal to ensure GHC won't pick up
2051 modules, not listed neither in exposed-modules, nor in
2052 other-modules.
2053 -Wmissing-import-lists
2055 warn when an import declaration does not explicitly list all the
2056 names brought into scope
2057 -Wmissing-local-signatures
2059 warn about polymorphic local bindings without signatures
2060 -Wmissing-local-sigs
2062 (deprecated) warn about polymorphic local bindings without sig‐
2063 natures
2064 -Wmissing-methods
2066 warn when class methods are undefined
2067 -Wmissing-monadfail-instances
2069 Warn when a failable pattern is used in a do-block that does not
2070 have a MonadFail instance.
2071 -Wmissing-pattern-synonym-signatures
2073 warn when pattern synonyms do not have type signatures
2074 -Wmissing-signatures
2076 warn about top-level functions without signatures
2077 -Wmonomorphism-restriction
2079 warn when the Monomorphism Restriction is applied
2080 -Wname-shadowing
2082 warn when names are shadowed
2083 -Wno-compat
2085 Disables all warnings enabled by -Wcompat.
2086 -Wnoncanonical-monad-instances
2088 warn when Applicative or Monad instances have noncanonical defi‐
2089 nitions of return, pure, (>>), or (*>). See flag description in
2090 options-sanity for more details.
2091 -Wnoncanonical-monadfail-instances
2093 warn when Monad or MonadFail instances have noncanonical defini‐
2094 tions of fail. See flag description in options-sanity for more
2095 details.
2096 -Wnoncanonical-monoid-instances
2098 warn when Semigroup or Monoid instances have noncanonical defi‐
2099 nitions of (<>) or mappend. See flag description in
2100 options-sanity for more details.
2101 -Worphans
2103 warn when the module contains orphan instance declarations or
2104 rewrite rules
2105 -Woverflowed-literals
2107 warn about literals that will overflow their type
2108 -Woverlapping-patterns
2110 warn about overlapping patterns
2111 -Wpartial-fields
2113 warn when defining a partial record field.
2114 -Wpartial-type-signatures
2116 warn about holes in partial type signatures when -XPartialTypeS‐
2117 ignatures is enabled. Not applicable when -XPartialTypesigna‐
2118 tures is not enabled, in which case errors are generated for
2119 such holes. See partial-type-signatures.
2120 -Wredundant-constraints
2122 Have the compiler warn about redundant constraints in type sig‐
2123 natures.
2124 -Wsafe warn if the module being compiled is regarded to be safe.
2126 -Wsemigroup
2128 warn when a Monoid is not Semigroup, and on non- Semigroup defi‐
2129 nitions of (<>)?
2130 -Wsimplifiable-class-constraints
2132 Warn about class constraints in a type signature that can be
2133 simplified using a top-level instance declaration.
2134 -Wspace-after-bang
2136 warn for missing space before the second argument of an infix
2137 definition of (!) when -XBangPatterns are not enabled
2138 -Wstar-binder
2140 warn about binding the (*) type operator despite -XStarIsType
2141 -Wstar-is-type
2143 warn when * is used to mean Data.Kind.Type
2144 -Wtabs warn if there are tabs in the source file
2146 -Wtrustworthy-safe
2148 warn if the module being compiled is marked as Trustworthy but
2149 it could instead be marked as Safe, a more informative bound.
2150 -Wtype-defaults
2152 warn when defaulting happens
2153 -Wtyped-holes
2155 Report warnings when typed hole errors are deferred until run‐
2156 time. See -fdefer-typed-holes.
2157 -Wunbanged-strict-patterns
2159 warn on pattern bind of unlifted variable that is neither bare
2160 nor banged
2161 -Wunrecognised-pragmas
2163 warn about uses of pragmas that GHC doesn't recognise
2164 -Wunrecognised-warning-flags
2166 throw a warning when an unreconised -W... flag is encountered on
2167 the command line.
2168 -Wunsafe
2170 warn if the module being compiled is regarded to be unsafe. See
2171 safe-haskell
2172 -Wunsupported-calling-conventions
2174 warn about use of an unsupported calling convention
2175 -Wunsupported-llvm-version
2177 Warn when using -fllvm with an unsupported version of LLVM.
2178 -Wunticked-promoted-constructors
2180 warn if promoted constructors are not ticked
2181 -Wunused-binds
2183 warn about bindings that are unused. Alias for
2184 -Wunused-top-binds, -Wunused-local-binds and -Wunused-pat‐
2185 tern-binds
2186 -Wunused-do-bind
2188 warn about do bindings that appear to throw away values of types
2189 other than ()
2190 -Wunused-foralls
2192 warn about type variables in user-written forall\s that are
2193 unused
2194 -Wunused-imports
2196 warn about unnecessary imports
2197 -Wunused-local-binds
2199 warn about local bindings that are unused
2200 -Wunused-matches
2202 warn about variables in patterns that aren't used
2203 -Wunused-pattern-binds
2205 warn about pattern match bindings that are unused
2206 -Wunused-top-binds
2208 warn about top-level bindings that are unused
2209 -Wunused-type-patterns
2211 warn about unused type variables which arise from patterns in in
2212 type family and data family instances
2213 -Wwarn make warnings non-fatal
2215 -Wwarnings-deprecations
2217 warn about uses of functions & types that have warnings or dep‐
2218 recated pragmas
2219 -Wwrong-do-bind
2221 warn about do bindings that appear to throw away monadic values
2222 that you should have bound instead
2223
2225 Copyright 2015. The University Court of the University of Glasgow. All
2226 rights reserved.
2227
2229 The GHC Team
2230
2232 2020, GHC Team
22338.8.4 Jul 27, 2020 GHC(1)