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 be‐
16 low.
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 -fprint-bind-re‐
96 sult -fshow-loaded-modules -ghci-script -ignore-dot-ghci -inter‐
97 active-print ⟨expr⟩
98 Interface files
100 --show-iface ⟨file⟩ -ddump-hi -ddump-hi-diffs -ddump-minimal-im‐
101 ports
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 -rt‐
150 sopts[=⟨none|some|all|ignore|ignoreAll⟩] -shared -split-objs
151 -split-sections -static -staticlib -threaded -with-rt‐
152 sopts=⟨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⟩ -fno-opt-co‐
178 ercion -fno-pre-inlining -fno-state-hack -fomit-interface-prag‐
179 mas -fomit-yields -foptimal-applicative-do -fpedantic-bottoms
180 -fregs-graph -fregs-iterative -fsimpl-tick-factor=⟨n⟩ -fsimpli‐
181 fier-phases=⟨n⟩ -fsolve-constant-dicts -fspec-constr -fspec-con‐
182 str-count=⟨n⟩ -fspec-constr-keen -fspec-constr-threshold=⟨n⟩
183 -fspecialise -fspecialise-aggressively -fstatic-argument-trans‐
184 formation -fstg-cse -fstg-lift-lams -fstg-lift-lams-known
185 -fstg-lift-lams-non-rec-args -fstg-lift-lams-rec-args -fstrict‐
186 ness -fstrictness-before=⟨n⟩ -funbox-small-strict-fields -fun‐
187 box-strict-fields -funfolding-creation-threshold=⟨n⟩ -funfold‐
188 ing-dict-discount=⟨n⟩ -funfolding-fun-discount=⟨n⟩ -funfold‐
189 ing-keeness-factor=⟨n⟩ -funfolding-use-threshold=⟨n⟩
190 Optimization levels
192 -O -O1 -O0 -O2
193 Package options
195 -clear-package-db -distrust ⟨pkg⟩ -distrust-all-packages -fpack‐
196 age-trust -global-package-db -hide-all-packages -hide-package
197 ⟨pkg⟩ -ignore-package ⟨pkg⟩ -no-auto-link-packages
198 -no-global-package-db -no-user-package-db -package ⟨pkg⟩ -pack‐
199 age-db ⟨file⟩ -package-env ⟨file⟩|⟨name⟩ -package-id ⟨unit-id⟩
200 -this-unit-id ⟨unit-id⟩ -trust ⟨pkg⟩ -user-package-db
201 Phases of compilation
203 -C -c -E -F -S -x ⟨suffix⟩
204 Overriding external programs
206 -pgma ⟨cmd⟩ -pgmc ⟨cmd⟩ -pgmdll ⟨cmd⟩ -pgmF ⟨cmd⟩ -pgmi ⟨cmd⟩
207 -pgmL ⟨cmd⟩ -pgml ⟨cmd⟩ -pgmlc ⟨cmd⟩ -pgmlibtool ⟨cmd⟩ -pgmlo
208 ⟨cmd⟩ -pgmP ⟨cmd⟩ -pgms ⟨cmd⟩ -pgmwindres ⟨cmd⟩
209 Phase-specific options
211 -opta ⟨option⟩ -optc ⟨option⟩ -optdll ⟨option⟩ -optF ⟨option⟩
212 -opti ⟨option⟩ -optL ⟨option⟩ -optl ⟨option⟩ -optlc ⟨option⟩
213 -optlo ⟨option⟩ -optP ⟨option⟩ -optwindres ⟨option⟩
214 Platform-specific options
216 -msse2 -msse4.2
217 Compiler plugins
219 -fclear-plugins -fplugin-opt=⟨module⟩:⟨args⟩ -fplugin=⟨module⟩
220 -hide-all-plugin-packages -plugin-package ⟨pkg⟩ -plugin-pack‐
221 age-id ⟨pkg-id⟩
222 Profiling
224 -fno-prof-auto -fno-prof-cafs -fno-prof-count-entries
225 -fprof-auto -fprof-auto-calls -fprof-auto-exported
226 -fprof-auto-top -fprof-cafs -prof -ticky
227 Program coverage
229 -fhpc
230 Recompilation checking
232 -fforce-recomp -fignore-hpc-changes -fignore-optim-changes
233 Redirecting output
235 --exclude-module=⟨file⟩ -ddump-mod-cycles -dep-makefile ⟨file⟩
236 -dep-suffix ⟨suffix⟩ -dumpdir ⟨dir⟩ -hcsuf ⟨suffix⟩ -hidir ⟨dir⟩
237 -hiedir ⟨dir⟩ -hiesuf ⟨suffix⟩ -hisuf ⟨suffix⟩ -include-pkg-deps
238 -o ⟨file⟩ -odir ⟨dir⟩ -ohi ⟨file⟩ -osuf ⟨suffix⟩ -outputdir
239 ⟨dir⟩ -stubdir ⟨dir⟩
240 Temporary files
242 -tmpdir ⟨dir⟩
243 Verbosity options
245 -fabstract-refinement-hole-fits -fdiagnostics-color=⟨al‐
246 ways|auto|never⟩ -fdiagnostics-show-caret -ferror-spans
247 -fhide-source-paths -fmax-refinement-hole-fits=⟨n⟩ -fmax-rele‐
248 vant-binds=⟨n⟩ -fmax-valid-hole-fits=⟨n⟩
249 -fno-show-valid-hole-fits -fno-sort-valid-hole-fits
250 -fprint-equality-relations -fprint-expanded-synonyms -fprint-ex‐
251 plicit-coercions -fprint-explicit-foralls -fprint-explicit-kinds
252 -fprint-explicit-runtime-reps -fprint-explicit-runtime-reps
253 -fprint-potential-instances -fprint-typechecker-elaboration
254 -fprint-unicode-syntax -frefinement-level-hole-fits=⟨n⟩ -fre‐
255 verse-errors -fshow-docs-of-hole-fits -fshow-hole-constraints
256 -fshow-hole-matches-of-hole-fits -fshow-provenance-of-hole-fits
257 -fshow-type-app-of-hole-fits -fshow-type-app-vars-of-hole-fits
258 -fshow-type-of-hole-fits -funclutter-valid-hole-fits -Rghc-tim‐
259 ing -v -v⟨n⟩
260 Warnings
262 -fdefer-out-of-scope-variables -fdefer-type-errors -fde‐
263 fer-typed-holes -fhelpful-errors -fmax-pmcheck-iterations=⟨n⟩
264 -fshow-warning-groups -W -w -Wall -Wall-missed-specialisations
265 -Wcompat -Wcpp-undef -Wdeferred-out-of-scope-variables -Wde‐
266 ferred-type-errors -Wdeprecated-flags -Wdeprecations -Wdodgy-ex‐
267 ports -Wdodgy-foreign-imports -Wdodgy-imports -Wduplicate-con‐
268 straints -Wduplicate-exports -Wempty-enumerations -Werror -Wev‐
269 erything -Whi-shadowing -Widentities -Wimplicit-kind-vars -Wim‐
270 plicit-prelude -Winaccessible-code -Wincomplete-patterns -Win‐
271 complete-record-updates -Wincomplete-uni-patterns -Win‐
272 line-rule-shadowing -Wmissed-extra-shared-lib -Wmissed-speciali‐
273 sations -Wmissing-deriving-strategies -Wmissing-export-lists
274 -Wmissing-exported-signatures -Wmissing-exported-sigs -Wmiss‐
275 ing-fields -Wmissing-home-modules -Wmissing-import-lists -Wmiss‐
276 ing-local-signatures -Wmissing-local-sigs -Wmissing-methods
277 -Wmissing-monadfail-instances -Wmissing-pattern-synonym-signa‐
278 tures -Wmissing-signatures -Wmonomorphism-restriction
279 -Wname-shadowing -Wno-compat -Wnoncanonical-monad-instances
280 -Wnoncanonical-monadfail-instances -Wnoncanonical-monoid-in‐
281 stances -Worphans -Woverflowed-literals -Woverlapping-patterns
282 -Wpartial-fields -Wpartial-type-signatures -Wredundant-con‐
283 straints -Wsafe -Wsemigroup -Wsimplifiable-class-constraints
284 -Wspace-after-bang -Wstar-binder -Wstar-is-type -Wtabs -Wtrust‐
285 worthy-safe -Wtype-defaults -Wtyped-holes -Wunbanged-strict-pat‐
286 terns -Wunrecognised-pragmas -Wunrecognised-warning-flags -Wun‐
287 safe -Wunsupported-calling-conventions -Wunsupported-llvm-ver‐
288 sion -Wunticked-promoted-constructors -Wunused-binds
289 -Wunused-do-bind -Wunused-foralls -Wunused-imports -Wunused-lo‐
290 cal-binds -Wunused-matches -Wunused-pattern-binds
291 -Wunused-top-binds -Wunused-type-patterns -Wwarn -Wwarnings-dep‐
292 recations -Wwrong-do-bind
293 Code generation
295 -dynamic-too
296 Build dynamic object files as well as static object files during
297 compilation
298 -fasm Use the native code generator
300 -fbyte-code
302 Generate byte-code
303 -fexternal-dynamic-refs
305 Generate code for linking against dynamic libraries
306 -fllvm Compile using the LLVM code generator
308 -fno-code
310 Omit code generation
311 -fobject-code
313 Generate object code
314 -fPIC Generate position-independent code (where available)
316 -fPIE Generate code for a position-independent executable (where
318 available)
319 -fwrite-interface
321 Always write interface files
322 Debugging the compiler
324 -dcmm-lint
325 C-\- pass sanity checking
326 -dcore-lint
328 Turn on internal sanity checking
329 -ddump-asm
331 Dump final assembly
332 -ddump-asm-expanded
334 Dump the result of the synthetic instruction expansion pass.
335 -ddump-asm-liveness
337 Dump assembly augmented with register liveness
338 -ddump-asm-native
340 Dump initial assembly
341 -ddump-asm-regalloc
343 Dump the result of register allocation
344 -ddump-asm-regalloc-stages
346 Dump the build/spill stages of the -fregs-graph register alloca‐
347 tor.
348 -ddump-asm-stats
350 Dump statistics from the register allocator.
351 -ddump-bcos
353 Dump interpreter byte code
354 -ddump-cfg-weights
356 Dump the assumed weights of the CFG.
357 -ddump-cmm
359 Dump the final C-\- output
360 -ddump-cmm-caf
362 Dump the results of the C-\- CAF analysis pass.
363 -ddump-cmm-cbe
365 Dump the results of common block elimination
366 -ddump-cmm-cfg
368 Dump the results of the C-\- control flow optimisation pass.
369 -ddump-cmm-cps
371 Dump the results of the CPS pass
372 -ddump-cmm-from-stg
374 Dump STG-to-C-\- output
375 -ddump-cmm-info
377 Dump the results of the C-\- info table augmentation pass.
378 -ddump-cmm-proc
380 Dump the results of proc-point analysis
381 -ddump-cmm-procmap
383 Dump the results of the C-\- proc-point map pass.
384 -ddump-cmm-raw
386 Dump raw C-\-
387 -ddump-cmm-sink
389 Dump the results of the C-\- sinking pass.
390 -ddump-cmm-sp
392 Dump the results of the C-\- stack layout pass.
393 -ddump-cmm-split
395 Dump the results of the C-\- proc-point splitting pass.
396 -ddump-cmm-switch
398 Dump the results of switch lowering passes
399 -ddump-cmm-verbose
401 Show output from main C-\- pipeline passes
402 -ddump-core-stats
404 Print a one-line summary of the size of the Core program at the
405 end of the optimisation pipeline
406 -ddump-cse
408 Dump CSE output
409 -ddump-deriv
411 Dump deriving output
412 -ddump-ds
414 Dump desugarer output.
415 -ddump-ec-trace
417 Trace exhaustiveness checker
418 -ddump-file-prefix=⟨str⟩
420 Set the prefix of the filenames used for debugging output.
421 -ddump-foreign
423 Dump foreign export stubs
424 -ddump-hpc
426 An alias for -ddump-ticked.
427 -ddump-if-trace
429 Trace interface files
430 -ddump-inlinings
432 Dump inlining info
433 -ddump-json
435 Dump error messages as JSON documents
436 -ddump-llvm
438 Dump LLVM intermediate code.
439 -ddump-mod-map
441 Dump the state of the module mapping database.
442 -ddump-occur-anal
444 Dump occurrence analysis output
445 -ddump-opt-cmm
447 Dump the results of C-\- to C-\- optimising passes
448 -ddump-parsed
450 Dump parse tree
451 -ddump-parsed-ast
453 Dump parser output as a syntax tree
454 -ddump-prep
456 Dump prepared core
457 -ddump-rn
459 Dump renamer output
460 -ddump-rn-ast
462 Dump renamer output as a syntax tree
463 -ddump-rn-stats
465 Renamer stats
466 -ddump-rn-trace
468 Trace renamer
469 -ddump-rtti
471 Trace runtime type inference
472 -ddump-rule-firings
474 Dump rule firing info
475 -ddump-rule-rewrites
477 Dump detailed rule firing info
478 -ddump-rules
480 Dump rewrite rules
481 -ddump-simpl
483 Dump final simplifier output
484 -ddump-simpl-iterations
486 Dump output from each simplifier iteration
487 -ddump-simpl-stats
489 Dump simplifier stats
490 -ddump-spec
492 Dump specialiser output
493 -ddump-splices
495 Dump TH spliced expressions, and what they evaluate to
496 -ddump-stg
498 Dump final STG
499 -ddump-str-signatures
501 Dump strictness signatures
502 -ddump-stranal
504 Dump strictness analyser output
505 -ddump-tc
507 Dump typechecker output
508 -ddump-tc-ast
510 Dump typechecker output as a syntax tree
511 -ddump-tc-trace
513 Trace typechecker
514 -ddump-ticked
516 Dump the code instrumented by HPC (hpc).
517 -ddump-timings
519 Dump per-pass timing and allocation statistics
520 -ddump-to-file
522 Dump to files instead of stdout
523 -ddump-types
525 Dump type signatures
526 -ddump-worker-wrapper
528 Dump worker-wrapper output
529 -dfaststring-stats
531 Show statistics for fast string usage when finished
532 -dhex-word-literals
534 Print values of type Word# in hexadecimal.
535 -dinitial-unique=⟨s⟩
537 Start UniqSupply allocation from ⟨s⟩.
538 -dinline-check=⟨str⟩
540 Dump information about inlining decisions
541 -dno-debug-output
543 Suppress unsolicited debugging output
544 -dppr-case-as-let
546 Print single alternative case expressions as strict lets.
547 -dppr-cols=⟨n⟩
549 Set the width of debugging output. For example -dppr-cols200
550 -dppr-debug
552 Turn on debug printing (more verbose)
553 -dppr-user-length
555 Set the depth for printing expressions in error msgs
556 -drule-check=⟨str⟩
558 Dump information about potential rule application
559 -dshow-passes
561 Print out each pass name as it happens
562 -dstg-lint
564 STG pass sanity checking
565 -dsuppress-all
567 In dumps, suppress everything (except for uniques) that is sup‐
568 pressible.
569 -dsuppress-coercions
571 Suppress the printing of coercions in Core dumps to make them
572 shorter
573 -dsuppress-idinfo
575 Suppress extended information about identifiers where they are
576 bound
577 -dsuppress-module-prefixes
579 Suppress the printing of module qualification prefixes
580 -dsuppress-stg-free-vars
582 Suppress the printing of closure free variable lists in STG out‐
583 put
584 -dsuppress-ticks
586 Suppress "ticks" in the pretty-printer output.
587 -dsuppress-timestamps
589 Suppress timestamps in dumps
590 -dsuppress-type-applications
592 Suppress type applications
593 -dsuppress-type-signatures
595 Suppress type signatures
596 -dsuppress-unfoldings
598 Suppress the printing of the stable unfolding of a variable at
599 its binding site
600 -dsuppress-uniques
602 Suppress the printing of uniques in debug output (easier to use
603 diff)
604 -dsuppress-var-kinds
606 Suppress the printing of variable kinds
607 -dth-dec-file
609 Dump evaluated TH declarations into *.th.hs files
610 -dunique-increment=⟨i⟩
612 Set the increment for the generated Unique's to ⟨i⟩.
613 -dverbose-core2core
615 Show output from each core-to-core pass
616 -dverbose-stg2stg
618 Show output from each STG-to-STG pass
619 -falignment-sanitisation
621 Compile with alignment checks for all info table dereferences.
622 -fcatch-bottoms
624 Insert error expressions after bottoming expressions; useful
625 when debugging the compiler.
626 -fllvm-fill-undef-with-garbage
628 Intruct LLVM to fill dead STG registers with garbage
629 -fproc-alignment
631 Align functions at given boundary.
632 -g Produce DWARF debug information in compiled object files. ⟨n⟩
634 can be 0, 1, or 2, with higher numbers producing richer output.
635 If ⟨n⟩ is omitted, level 2 is assumed.
636 C pre-processor
638 -cpp Run the C pre-processor on Haskell source files
639 -D⟨symbol⟩[=⟨value⟩]
641 Define a symbol in the C pre-processor
642 -I⟨dir⟩
644 Add ⟨dir⟩ to the directory search list for #include files
645 -U⟨symbol⟩
647 Undefine a symbol in the C pre-processor
648 Finding imports
650 -i Empty the import directory list
651 -i⟨dir⟩[:⟨dir⟩]*
653 add ⟨dir⟩, ⟨dir2⟩, etc. to import path
654 Interactive mode
656 -fbreak-on-error
657 Break on uncaught exceptions and errors
658 -fbreak-on-exception
660 Break on any exception thrown
661 -fghci-hist-size=⟨n⟩
663 Set the number of entries GHCi keeps for :history. See ghci-de‐
664 bugger.
665 -fghci-leak-check
667 (Debugging only) check for space leaks when loading new modules
668 in GHCi.
669 -flocal-ghci-history
671 Use current directory for the GHCi command history file
672 .ghci-history.
673 -fno-it
675 No longer set the special variable it.
676 -fprint-bind-result
678 Turn on printing of binding results in GHCi
679 -fshow-loaded-modules
681 Show the names of modules that GHCi loaded after a :load com‐
682 mand.
683 -ghci-script
685 Read additional .ghci files
686 -ignore-dot-ghci
688 Disable reading of .ghci files
689 -interactive-print ⟨expr⟩
691 Select the function to use for printing evaluated expressions in
692 GHCi
693 Interface files
695 --show-iface ⟨file⟩
696 See modes.
697 -ddump-hi
699 Dump the new interface to stdout
700 -ddump-hi-diffs
702 Show the differences vs. the old interface
703 -ddump-minimal-imports
705 Dump a minimal set of imports
706 Keeping intermediate files
708 -keep-hc-file
709 Retain intermediate .hc files.
710 -keep-hi-files
712 Retain intermediate .hi files (the default).
713 -keep-hscpp-file
715 Retain intermediate .hscpp files.
716 -keep-llvm-file
718 Retain intermediate LLVM .ll files. Implies -fllvm.
719 -keep-o-files
721 Retain intermediate .o files (the default).
722 -keep-s-file
724 Retain intermediate .s files.
725 -keep-tmp-files
727 Retain all intermediate temporary files.
728 Language options
730 -fno-safe-haskell
731 Disable Safe Haskell
732 -fsort-by-size-hole-fits
734 Sort valid hole fits by size.
735 -fsort-by-subsumption-hole-fits
737 Sort valid hole fits by subsumption.
738 -XAllowAmbiguousTypes
740 Allow the user to write ambiguous types, and the type inference
741 engine to infer them.
742 -XApplicativeDo
744 Enable Applicative do-notation desugaring
745 -XArrows
747 Enable arrow notation extension
748 -XBangPatterns
750 Enable bang patterns.
751 -XBinaryLiterals
753 Enable support for binary literals.
754 -XBlockArguments
756 Allow do blocks and other constructs as function arguments.
757 -XCApiFFI
759 Enable the CAPI calling convention.
760 -XConstrainedClassMethods
762 Enable constrained class methods.
763 -XConstraintKinds
765 Enable a kind of constraints.
766 -XCPP Enable the C preprocessor.
768 -XDataKinds
770 Enable datatype promotion.
771 -XDatatypeContexts
773 Allow contexts on data types.
774 -XDefaultSignatures
776 Enable default signatures.
777 -XDeriveAnyClass
779 Enable deriving for any class.
780 -XDeriveDataTypeable
782 Enable deriving for the Data class. Implied by (deprecated) Au‐
783 toDeriveTypeable.
784 -XDeriveFoldable
786 Enable deriving for the Foldable class. Implied by Derive‐
787 Traversable.
788 -XDeriveFunctor
790 Enable deriving for the Functor class. Implied by Derive‐
791 Traversable.
792 -XDeriveGeneric
794 Enable deriving for the Generic class.
795 -XDeriveLift
797 Enable deriving for the Lift class
798 -XDeriveTraversable
800 Enable deriving for the Traversable class. Implies DeriveFunc‐
801 tor and DeriveFoldable.
802 -XDerivingStrategies
804 Enables deriving strategies.
805 -XDerivingVia
807 Enable deriving instances via types of the same runtime repre‐
808 sentation. Implies DerivingStrategies.
809 -XDisambiguateRecordFields
811 Enable record field disambiguation. Implied by RecordWildCards.
812 -XDuplicateRecordFields
814 Allow definition of record types with identically-named fields.
815 -XEmptyCase
817 Allow empty case alternatives.
818 -XEmptyDataDecls
820 Allow definition of empty data types.
821 -XEmptyDataDeriving
823 Allow deriving instances of standard type classes for empty data
824 types.
825 -XExistentialQuantification
827 Enable liberalised type synonyms.
828 -XExplicitForAll
830 Enable explicit universal quantification. Implied by Scoped‐
831 TypeVariables, LiberalTypeSynonyms, RankNTypes and Existen‐
832 tialQuantification.
833 -XExplicitNamespaces
835 Enable using the keyword type to specify the namespace of en‐
836 tries in imports and exports (explicit-namespaces). Implied by
837 TypeOperators and TypeFamilies.
838 -XExtendedDefaultRules
840 Use GHCi's extended default rules in a normal module.
841 -XFlexibleContexts
843 Enable flexible contexts. Implied by ImplicitParams.
844 -XFlexibleInstances
846 Enable flexible instances. Implies TypeSynonymInstances. Im‐
847 plied by ImplicitParams.
848 -XForeignFunctionInterface
850 Enable foreign function interface.
851 -XFunctionalDependencies
853 Enable functional dependencies. Implies MultiParamTypeClasses.
854 -XGADTs
856 Enable generalised algebraic data types. Implies GADTSyntax and
857 MonoLocalBinds.
858 -XGADTSyntax
860 Enable generalised algebraic data type syntax.
861 -XGeneralisedNewtypeDeriving
863 Enable newtype deriving.
864 -XGeneralizedNewtypeDeriving
866 Enable newtype deriving.
867 -XHexFloatLiterals
869 Enable support for hexadecimal floating point literals.
870 -XImplicitParams
872 Enable Implicit Parameters. Implies FlexibleContexts and Flexi‐
873 bleInstances.
874 -XImpredicativeTypes
876 Enable impredicative types. Implies RankNTypes.
877 -XIncoherentInstances
879 Enable incoherent instances. Implies OverlappingInstances.
880 -XInstanceSigs
882 Enable instance signatures.
883 -XInterruptibleFFI
885 Enable interruptible FFI.
886 -XKindSignatures
888 Enable kind signatures. Implied by TypeFamilies and PolyKinds.
889 -XLambdaCase
891 Enable lambda-case expressions.
892 -XLiberalTypeSynonyms
894 Enable liberalised type synonyms.
895 -XMagicHash
897 Allow # as a postfix modifier on identifiers.
898 -XMonadComprehensions
900 Enable monad comprehensions.
901 -XMonadFailDesugaring
903 Enable monadfail desugaring.
904 -XMonoLocalBinds
906 Enable do not generalise local bindings. Implied by TypeFami‐
907 lies and GADTs.
908 -XMultiParamTypeClasses
910 Enable multi parameter type classes. Implied by FunctionalDe‐
911 pendencies.
912 -XMultiWayIf
914 Enable multi-way if-expressions.
915 -XNamedFieldPuns
917 Enable record puns.
918 -XNamedWildCards
920 Enable named wildcards.
921 -XNegativeLiterals
923 Enable support for negative literals.
924 -XNoImplicitPrelude
926 Don't implicitly import Prelude. Implied by RebindableSyntax.
927 -XNoMonomorphismRestriction
929 Disable the monomorphism restriction.
930 -XNoPatternGuards
932 Disable pattern guards. Implied by Haskell98.
933 -XNoTraditionalRecordSyntax
935 Disable support for traditional record syntax (as supported by
936 Haskell 98) C {f = x}
937 -XNPlusKPatterns
939 Enable support for n+k patterns. Implied by Haskell98.
940 -XNullaryTypeClasses
942 Deprecated, does nothing. nullary (no parameter) type classes
943 are now enabled using MultiParamTypeClasses.
944 -XNumDecimals
946 Enable support for 'fractional' integer literals.
947 -XNumericUnderscores
949 Enable support for numeric underscores.
950 -XOverlappingInstances
952 Enable overlapping instances.
953 -XOverloadedLabels
955 Enable overloaded labels.
956 -XOverloadedLists
958 Enable overloaded lists.
959 -XOverloadedStrings
961 Enable overloaded string literals.
962 -XPackageImports
964 Enable package-qualified imports.
965 -XParallelListComp
967 Enable parallel list comprehensions.
968 -XPartialTypeSignatures
970 Enable partial type signatures.
971 -XPatternSynonyms
973 Enable pattern synonyms.
974 -XPolyKinds
976 Enable kind polymorphism. Implies KindSignatures.
977 -XPostfixOperators
979 Enable postfix operators.
980 -XQuantifiedConstraints
982 Allow forall quantifiers in constraints.
983 -XQuasiQuotes
985 Enable quasiquotation.
986 -XRank2Types
988 Enable rank-2 types. Synonym for RankNTypes.
989 -XRankNTypes
991 Enable rank-N types. Implied by ImpredicativeTypes.
992 -XRebindableSyntax
994 Employ rebindable syntax. Implies NoImplicitPrelude.
995 -XRecordWildCards
997 Enable record wildcards. Implies DisambiguateRecordFields.
998 -XRecursiveDo
1000 Enable recursive do (mdo) notation.
1001 -XRoleAnnotations
1003 Enable role annotations.
1004 -XSafe Enable the Safe Haskell Safe mode.
1006 -XScopedTypeVariables
1008 Enable lexically-scoped type variables.
1009 -XStandaloneDeriving
1011 Enable standalone deriving.
1012 -XStarIsType
1014 Treat * as Data.Kind.Type.
1015 -XStaticPointers
1017 Enable static pointers.
1018 -XStrict
1020 Make bindings in the current module strict by default.
1021 -XStrictData
1023 Enable default strict datatype fields.
1024 -XTemplateHaskell
1026 Enable Template Haskell.
1027 -XTemplateHaskellQuotes
1029 Enable quotation subset of Template Haskell.
1030 -XTransformListComp
1032 Enable generalised list comprehensions.
1033 -XTrustworthy
1035 Enable the Safe Haskell Trustworthy mode.
1036 -XTupleSections
1038 Enable tuple sections.
1039 -XTypeApplications
1041 Enable type application syntax in terms and types.
1042 -XTypeFamilies
1044 Enable type families. Implies ExplicitNamespaces, KindSigna‐
1045 tures, and MonoLocalBinds.
1046 -XTypeFamilyDependencies
1048 Enable injective type families. Implies TypeFamilies.
1049 -XTypeInType
1051 Deprecated. Enable kind polymorphism and datatype promotion.
1052 -XTypeOperators
1054 Enable type operators. Implies ExplicitNamespaces.
1055 -XTypeSynonymInstances
1057 Enable type synonyms in instance heads. Implied by FlexibleIn‐
1058 stances.
1059 -XUnboxedSums
1061 Enable unboxed sums.
1062 -XUnboxedTuples
1064 Enable the use of unboxed tuple syntax.
1065 -XUndecidableInstances
1067 Enable undecidable instances.
1068 -XUndecidableSuperClasses
1070 Allow all superclass constraints, including those that may re‐
1071 sult in non-termination of the typechecker.
1072 -XUnicodeSyntax
1074 Enable unicode syntax.
1075 -XUnsafe
1077 Enable Safe Haskell Unsafe mode.
1078 -XViewPatterns
1080 Enable view patterns.
1081 Linking options
1083 -c Stop after generating object (.o) file
1084 -debug Use the debugging runtime
1086 -dylib-install-name ⟨path⟩
1088 Set the install name (via -install_name passed to Apple's
1089 linker), specifying the full install path of the library file.
1090 Any libraries or executables that link with it later will pick
1091 up that path as their runtime search location for it. (Dar‐
1092 win/OS X only)
1093 -dynamic
1095 Build dynamically-linked object files and executables
1096 -dynload
1098 Selects one of a number of modes for finding shared libraries at
1099 runtime.
1100 -eventlog
1102 Enable runtime event tracing
1103 -fno-embed-manifest
1105 Do not embed the manifest in the executable (Windows only)
1106 -fno-gen-manifest
1108 Do not generate a manifest file (Windows only)
1109 -fno-shared-implib
1111 Don't generate an import library for a DLL (Windows only)
1112 -framework ⟨name⟩
1114 On Darwin/OS X/iOS only, link in the framework ⟨name⟩. This op‐
1115 tion corresponds to the -framework option for Apple's Linker.
1116 -framework-path ⟨dir⟩
1118 On Darwin/OS X/iOS only, add ⟨dir⟩ to the list of directories
1119 searched for frameworks. This option corresponds to the -F op‐
1120 tion for Apple's Linker.
1121 -fwhole-archive-hs-libs
1123 When linking a binary executable, this inserts the flag
1124 -Wl,--whole-archive before any -l flags for Haskell libraries,
1125 and -Wl,--no-whole-archive afterwards
1126 -keep-cafs
1128 Do not garbage-collect CAFs (top-level expressions) at runtime
1129 -L ⟨dir⟩
1131 Add ⟨dir⟩ to the list of directories searched for libraries
1132 -l ⟨lib⟩
1134 Link in library ⟨lib⟩
1135 -main-is ⟨thing⟩
1137 Set main module and function
1138 -no-hs-main
1140 Don't assume this program contains main
1141 -no-rtsopts-suggestions
1143 Don't print RTS suggestions about linking with -rt‐
1144 sopts[=⟨none|some|all|ignore|ignoreAll⟩].
1145 -package ⟨name⟩
1147 Expose package ⟨pkg⟩
1148 -pie Instruct the linker to produce a position-independent exe‐
1150 cutable.
1151 -rdynamic
1153 This instructs the linker to add all symbols, not only used
1154 ones, to the dynamic symbol table. Currently Linux and Win‐
1155 dows/MinGW32 only. This is equivalent to using -optl -rdynamic
1156 on Linux, and -optl -export-all-symbols on Windows.
1157 -rtsopts[=⟨none|some|all|ignore|ignoreAll⟩]
1159 Control whether the RTS behaviour can be tweaked via com‐
1160 mand-line flags and the GHCRTS environment variable. Using none
1161 means no RTS flags can be given; some means only a minimum of
1162 safe options can be given (the default); all (or no argument at
1163 all) means that all RTS flags are permitted; ignore means RTS
1164 flags can be given, but are treated as regular arguments and
1165 passed to the Haskell program as arguments; ignoreAll is the
1166 same as ignore, but GHCRTS is also ignored. -rtsopts does not
1167 affect -with-rtsopts behavior; flags passed via -with-rtsopts
1168 are used regardless of -rtsopts.
1169 -shared
1171 Generate a shared library (as opposed to an executable)
1172 -split-objs
1174 Split objects (for libraries)
1175 -split-sections
1177 Split sections for link-time dead-code stripping
1178 -static
1180 Use static Haskell libraries
1181 -staticlib
1183 Generate a standalone static library (as opposed to an exe‐
1184 cutable). This is useful when cross compiling. The library to‐
1185 gether with all its dependencies ends up in in a single static
1186 library that can be linked against.
1187 -threaded
1189 Use the threaded runtime
1190 -with-rtsopts=⟨opts⟩
1192 Set the default RTS options to ⟨opts⟩.
1193 Miscellaneous options
1195 -fexternal-interpreter
1196 Run interpreted code in a separate process
1197 -fglasgow-exts
1199 Deprecated. Enable most language extensions; see options-lan‐
1200 guage for exactly which ones.
1201 -ghcversion-file ⟨path to ghcversion.h⟩
1203 (GHC as a C compiler only) Use this ghcversion.h file
1204 -H ⟨size⟩
1206 Set the minimum size of the heap to ⟨size⟩
1207 -j[⟨n⟩]
1209 When compiling with --make, compile ⟨n⟩ modules in parallel.
1210 Modes of operation
1212 --frontend ⟨module⟩
1213 run GHC with the given frontend plugin; see frontend_plugins for
1214 details.
1215 --help Display help
1217 --info display information about the compiler
1219 --interactive
1221 Interactive mode - normally used by just running ghci; see ghci
1222 for details.
1223 --make Build a multi-module Haskell program, automatically figuring out
1225 dependencies. Likely to be much easier, and faster, than using
1226 make; see make-mode for details.
1227 --mk-dll
1229 DLL-creation mode (Windows only)
1230 --numeric-version
1232 display GHC version (numeric only)
1233 --print-libdir
1235 display GHC library directory
1236 --show-iface ⟨file⟩
1238 display the contents of an interface file.
1239 --show-options
1241 display the supported command line options
1242 --supported-extensions
1244 display the supported language extensions
1245 --version
1247 display GHC version
1248 -e ⟨expr⟩
1250 Evaluate expr; see eval-mode for details.
1251 -M generate dependency information suitable for use in a Makefile;
1253 see makefile-dependencies for details.
1254 Individual optimizations
1256 -fasm-shortcutting
1257 Enable shortcutting on assembly. Implied by -O2.
1258 -fblock-layout-cfg
1260 Use the new cfg based block layout algorithm.
1261 -fblock-layout-weightless
1263 Ignore cfg weights for code layout.
1264 -fblock-layout-weights
1266 Sets edge weights used by the new code layout algorithm.
1267 -fcall-arity
1269 Enable call-arity optimisation. Implied by -O.
1270 -fcase-folding
1272 Enable constant folding in case expressions. Implied by -O.
1273 -fcase-merge
1275 Enable case-merging. Implied by -O.
1276 -fcmm-elim-common-blocks
1278 Enable Cmm common block elimination. Implied by -O.
1279 -fcmm-sink
1281 Enable Cmm sinking. Implied by -O.
1282 -fcpr-anal
1284 Turn on CPR analysis in the demand analyser. Implied by -O.
1285 -fcross-module-specialise
1287 Turn on specialisation of overloaded functions imported from
1288 other modules.
1289 -fcse Enable common sub-expression elimination. Implied by -O.
1291 -fdicts-cheap
1293 Make dictionary-valued expressions seem cheap to the optimiser.
1294 -fdicts-strict
1296 Make dictionaries strict
1297 -fdmd-tx-dict-sel
1299 Use a special demand transformer for dictionary selectors. Al‐
1300 ways enabled by default.
1301 -fdo-eta-reduction
1303 Enable eta-reduction. Implied by -O.
1304 -fdo-lambda-eta-expansion
1306 Enable lambda eta-expansion. Always enabled by default.
1307 -feager-blackholing
1309 Turn on eager blackholing
1310 -fenable-rewrite-rules
1312 Switch on all rewrite rules (including rules generated by auto‐
1313 matic specialisation of overloaded functions). Implied by -O.
1314 -fexcess-precision
1316 Enable excess intermediate precision
1317 -fexitification
1319 Enables exitification optimisation. Implied by -O.
1320 -fexpose-all-unfoldings
1322 Expose all unfoldings, even for very large or recursive func‐
1323 tions.
1324 -ffloat-in
1326 Turn on the float-in transformation. Implied by -O.
1327 -ffull-laziness
1329 Turn on full laziness (floating bindings outwards). Implied by
1330 -O.
1331 -ffun-to-thunk
1333 Allow worker-wrapper to convert a function closure into a thunk
1334 if the function does not use any of its arguments. Off by de‐
1335 fault.
1336 -fignore-asserts
1338 Ignore assertions in the source. Implied by -O.
1339 -fignore-interface-pragmas
1341 Ignore pragmas in interface files. Implied by -O0 only.
1342 -flate-dmd-anal
1344 Run demand analysis again, at the end of the simplification
1345 pipeline
1346 -flate-specialise
1348 Run a late specialisation pass
1349 -fliberate-case
1351 Turn on the liberate-case transformation. Implied by -O2.
1352 -fliberate-case-threshold=⟨n⟩
1354 default: 2000. Set the size threshold for the liberate-case
1355 transformation to ⟨n⟩
1356 -fllvm-pass-vectors-in-regs
1358 Pass vector value in vector registers for function calls
1359 -floopification
1361 Turn saturated self-recursive tail-calls into local jumps in the
1362 generated assembly. Implied by -O.
1363 -fmax-inline-alloc-size=⟨n⟩
1365 default: 128. Set the maximum size of inline array allocations
1366 to ⟨n⟩ bytes (default: 128).
1367 -fmax-inline-memcpy-insns=⟨n⟩
1369 default: 32. Inline memcpy calls if they would generate no more
1370 than ⟨n⟩ pseudo instructions.
1371 -fmax-inline-memset-insns=⟨n⟩
1373 default: 32. Inline memset calls if they would generate no more
1374 than ⟨n⟩ pseudo instructions
1375 -fmax-simplifier-iterations=⟨n⟩
1377 default: 4. Set the max iterations for the simplifier.
1378 -fmax-uncovered-patterns=⟨n⟩
1380 default: 4. Set the maximum number of patterns to display in
1381 warnings about non-exhaustive ones.
1382 -fmax-worker-args=⟨n⟩
1384 default: 10. If a worker has that many arguments, none will be
1385 unpacked anymore.
1386 -fno-opt-coercion
1388 Turn off the coercion optimiser
1389 -fno-pre-inlining
1391 Turn off pre-inlining
1392 -fno-state-hack
1394 Turn off the state hackwhereby any lambda with a real-world
1395 state token as argument is considered to be single-entry. Hence
1396 OK to inline things inside it.
1397 -fomit-interface-pragmas
1399 Don't generate interface pragmas. Implied by -O0 only.
1400 -fomit-yields
1402 Omit heap checks when no allocation is being performed.
1403 -foptimal-applicative-do
1405 Use a slower but better algorithm for ApplicativeDo
1406 -fpedantic-bottoms
1408 Make GHC be more precise about its treatment of bottom (but see
1409 also -fno-state-hack). In particular, GHC will not eta-expand
1410 through a case expression.
1411 -fregs-graph
1413 Use the graph colouring register allocator for register alloca‐
1414 tion in the native code generator. Implied by -O2.
1415 -fregs-iterative
1417 Use the iterative coalescing graph colouring register allocator
1418 in the native code generator.
1419 -fsimpl-tick-factor=⟨n⟩
1421 default: 100. Set the percentage factor for simplifier ticks.
1422 -fsimplifier-phases=⟨n⟩
1424 default: 2. Set the number of phases for the simplifier. Ig‐
1425 nored with -O0.
1426 -fsolve-constant-dicts
1428 When solving constraints, try to eagerly solve super classes us‐
1429 ing available dictionaries.
1430 -fspec-constr
1432 Turn on the SpecConstr transformation. Implied by -O2.
1433 -fspec-constr-count=⟨n⟩
1435 default: 3.* Set to ⟨n⟩ the maximum number of specialisations
1436 that will be created for any one function by the SpecConstr
1437 transformation.
1438 -fspec-constr-keen
1440 Specialize a call with an explicit constructor argument, even if
1441 the argument is not scrutinised in the body of the function
1442 -fspec-constr-threshold=⟨n⟩
1444 default: 2000. Set the size threshold for the SpecConstr trans‐
1445 formation to ⟨n⟩.
1446 -fspecialise
1448 Turn on specialisation of overloaded functions. Implied by -O.
1449 -fspecialise-aggressively
1451 Turn on specialisation of overloaded functions regardless of
1452 size, if unfolding is available
1453 -fstatic-argument-transformation
1455 Turn on the static argument transformation.
1456 -fstg-cse
1458 Enable common sub-expression elimination on the STG intermediate
1459 language
1460 -fstg-lift-lams
1462 Enable late lambda lifting on the STG intermediate language. Im‐
1463 plied by -O2.
1464 -fstg-lift-lams-known
1466 Allow turning known into unknown calls while performing late
1467 lambda lifting.
1468 -fstg-lift-lams-non-rec-args
1470 Create top-level non-recursive functions with at most <n> param‐
1471 eters while performing late lambda lifting.
1472 -fstg-lift-lams-rec-args
1474 Create top-level recursive functions with at most <n> parameters
1475 while performing late lambda lifting.
1476 -fstrictness
1478 Turn on strictness analysis. Implied by -O. Implies
1479 -fworker-wrapper
1480 -fstrictness-before=⟨n⟩
1482 Run an additional strictness analysis before simplifier phase
1483 ⟨n⟩
1484 -funbox-small-strict-fields
1486 Flatten strict constructor fields with a pointer-sized represen‐
1487 tation. Implied by -O.
1488 -funbox-strict-fields
1490 Flatten strict constructor fields
1491 -funfolding-creation-threshold=⟨n⟩
1493 default: 750. Tweak unfolding settings.
1494 -funfolding-dict-discount=⟨n⟩
1496 default: 30. Tweak unfolding settings.
1497 -funfolding-fun-discount=⟨n⟩
1499 default: 60. Tweak unfolding settings.
1500 -funfolding-keeness-factor=⟨n⟩
1502 default: 1.5. Tweak unfolding settings.
1503 -funfolding-use-threshold=⟨n⟩
1505 default: 60. Tweak unfolding settings.
1506 Optimization levels
1508 -O Enable level 1 optimisations
1509 -O0 Disable optimisations (default)
1511 -O2 Enable level 2 optimisations
1513 Package options
1515 -clear-package-db
1516 Clear the package db stack.
1517 -distrust ⟨pkg⟩
1519 Expose package ⟨pkg⟩ and set it to be distrusted. See
1520 safe-haskell.
1521 -distrust-all-packages
1523 Distrust all packages by default. See safe-haskell.
1524 -fpackage-trust
1526 Enable Safe Haskell trusted package requirement for trustworthy
1527 modules.
1528 -global-package-db
1530 Add the global package db to the stack.
1531 -hide-all-packages
1533 Hide all packages by default
1534 -hide-package ⟨pkg⟩
1536 Hide package ⟨pkg⟩
1537 -ignore-package ⟨pkg⟩
1539 Ignore package ⟨pkg⟩
1540 -no-auto-link-packages
1542 Don't automatically link in the base and rts packages.
1543 -no-global-package-db
1545 Remove the global package db from the stack.
1546 -no-user-package-db
1548 Remove the user's package db from the stack.
1549 -package ⟨pkg⟩
1551 Expose package ⟨pkg⟩
1552 -package-db ⟨file⟩
1554 Add ⟨file⟩ to the package db stack.
1555 -package-env ⟨file⟩|⟨name⟩
1557 Use the specified package environment.
1558 -package-id ⟨unit-id⟩
1560 Expose package by id ⟨unit-id⟩
1561 -this-unit-id ⟨unit-id⟩
1563 Compile to be part of unit (i.e. package) ⟨unit-id⟩
1564 -trust ⟨pkg⟩
1566 Expose package ⟨pkg⟩ and set it to be trusted. See safe-haskell.
1567 -user-package-db
1569 Add the user's package db to the stack.
1570 Phases of compilation
1572 -C Stop after generating C (.hc file)
1573 -c Stop after generating object (.o) file
1575 -E Stop after preprocessing (.hspp file)
1577 -F Enable the use of a pre-processor (set with -pgmF ⟨cmd⟩)
1579 -S Stop after generating assembly (.s file)
1581 -x ⟨suffix⟩
1583 Override default behaviour for source files
1584 Overriding external programs
1586 -pgma ⟨cmd⟩
1587 Use ⟨cmd⟩ as the assembler
1588 -pgmc ⟨cmd⟩
1590 Use ⟨cmd⟩ as the C compiler
1591 -pgmdll ⟨cmd⟩
1593 Use ⟨cmd⟩ as the DLL generator
1594 -pgmF ⟨cmd⟩
1596 Use ⟨cmd⟩ as the pre-processor (with -F only)
1597 -pgmi ⟨cmd⟩
1599 Use ⟨cmd⟩ as the external interpreter command.
1600 -pgmL ⟨cmd⟩
1602 Use ⟨cmd⟩ as the literate pre-processor
1603 -pgml ⟨cmd⟩
1605 Use ⟨cmd⟩ as the linker
1606 -pgmlc ⟨cmd⟩
1608 Use ⟨cmd⟩ as the LLVM compiler
1609 -pgmlibtool ⟨cmd⟩
1611 Use ⟨cmd⟩ as the command for libtool (with -staticlib only).
1612 -pgmlo ⟨cmd⟩
1614 Use ⟨cmd⟩ as the LLVM optimiser
1615 -pgmP ⟨cmd⟩
1617 Use ⟨cmd⟩ as the C pre-processor (with -cpp only)
1618 -pgms ⟨cmd⟩
1620 Use ⟨cmd⟩ as the splitter
1621 -pgmwindres ⟨cmd⟩
1623 Use ⟨cmd⟩ as the program for embedding manifests on Windows.
1624 Phase-specific options
1626 -opta ⟨option⟩
1627 pass ⟨option⟩ to the assembler
1628 -optc ⟨option⟩
1630 pass ⟨option⟩ to the C compiler
1631 -optdll ⟨option⟩
1633 pass ⟨option⟩ to the DLL generator
1634 -optF ⟨option⟩
1636 pass ⟨option⟩ to the custom pre-processor
1637 -opti ⟨option⟩
1639 pass ⟨option⟩ to the interpreter sub-process.
1640 -optL ⟨option⟩
1642 pass ⟨option⟩ to the literate pre-processor
1643 -optl ⟨option⟩
1645 pass ⟨option⟩ to the linker
1646 -optlc ⟨option⟩
1648 pass ⟨option⟩ to the LLVM compiler
1649 -optlo ⟨option⟩
1651 pass ⟨option⟩ to the LLVM optimiser
1652 -optP ⟨option⟩
1654 pass ⟨option⟩ to cpp (with -cpp only)
1655 -optwindres ⟨option⟩
1657 pass ⟨option⟩ to windres.
1658 Platform-specific options
1660 -msse2 (x86 only) Use SSE2 for floating-point operations
1661 -msse4.2
1663 (x86 only) Use SSE4.2 for floating-point operations
1664 Compiler plugins
1666 -fclear-plugins
1667 Clear the list of active plugins
1668 -fplugin-opt=⟨module⟩:⟨args⟩
1670 Give arguments to a plugin module; module must be specified with
1671 -fplugin=⟨module⟩
1672 -fplugin=⟨module⟩
1674 Load a plugin exported by a given module
1675 -hide-all-plugin-packages
1677 Hide all packages for plugins by default
1678 -plugin-package ⟨pkg⟩
1680 Expose ⟨pkg⟩ for plugins
1681 -plugin-package-id ⟨pkg-id⟩
1683 Expose ⟨pkg-id⟩ for plugins
1684 Profiling
1686 -fno-prof-auto
1687 Disables any previous -fprof-auto, -fprof-auto-top, or
1688 -fprof-auto-exported options.
1689 -fno-prof-cafs
1691 Disables any previous -fprof-cafs option.
1692 -fno-prof-count-entries
1694 Do not collect entry counts
1695 -fprof-auto
1697 Auto-add SCC\ s to all bindings not marked INLINE
1698 -fprof-auto-calls
1700 Auto-add SCC\ s to all call sites
1701 -fprof-auto-exported
1703 Auto-add SCC\ s to all exported bindings not marked INLINE
1704 -fprof-auto-top
1706 Auto-add SCC\ s to all top-level bindings not marked INLINE
1707 -fprof-cafs
1709 Auto-add SCC\ s to all CAFs
1710 -prof Turn on profiling
1712 -ticky Turn on ticky-ticky profiling
1714 Program coverage
1716 -fhpc Turn on Haskell program coverage instrumentation
1717 Recompilation checking
1719 -fforce-recomp
1720 Turn off recompilation checking. This is implied by any -ddump-X
1721 option when compiling a single file (i.e. when using -c).
1722 -fignore-hpc-changes
1724 Do not recompile modules just to match changes to HPC flags.
1725 This is especially useful for avoiding recompilation when using
1726 GHCi, and is enabled by default for GHCi.
1727 -fignore-optim-changes
1729 Do not recompile modules just to match changes to optimisation
1730 flags. This is especially useful for avoiding recompilation when
1731 using GHCi, and is enabled by default for GHCi.
1732 Redirecting output
1734 --exclude-module=⟨file⟩
1735 Regard ⟨file⟩ as "stable"; i.e., exclude it from having depen‐
1736 dencies on it.
1737 -ddump-mod-cycles
1739 Dump module cycles
1740 -dep-makefile ⟨file⟩
1742 Use ⟨file⟩ as the makefile
1743 -dep-suffix ⟨suffix⟩
1745 Make dependencies that declare that files with suffix
1746 .⟨suf⟩⟨osuf⟩ depend on interface files with suffix .⟨suf⟩hi
1747 -dumpdir ⟨dir⟩
1749 redirect dump files
1750 -hcsuf ⟨suffix⟩
1752 set the suffix to use for intermediate C files
1753 -hidir ⟨dir⟩
1755 set directory for interface files
1756 -hiedir ⟨dir⟩
1758 set directory for extended interface files
1759 -hiesuf ⟨suffix⟩
1761 set the suffix to use for extended interface files
1762 -hisuf ⟨suffix⟩
1764 set the suffix to use for interface files
1765 -include-pkg-deps
1767 Regard modules imported from packages as unstable
1768 -o ⟨file⟩
1770 set output filename
1771 -odir ⟨dir⟩
1773 set directory for object files
1774 -ohi ⟨file⟩
1776 set the filename in which to put the interface
1777 -osuf ⟨suffix⟩
1779 set the output file suffix
1780 -outputdir ⟨dir⟩
1782 set output directory
1783 -stubdir ⟨dir⟩
1785 redirect FFI stub files
1786 Temporary files
1788 -tmpdir ⟨dir⟩
1789 set the directory for temporary files
1790 Verbosity options
1792 -fabstract-refinement-hole-fits
1793 default: off. Toggles whether refinements where one or more of
1794 the holes are abstract are reported.
1795 -fdiagnostics-color=⟨always|auto|never⟩
1797 Use colors in error messages
1798 -fdiagnostics-show-caret
1800 Whether to show snippets of original source code
1801 -ferror-spans
1803 Output full span in error messages
1804 -fhide-source-paths
1806 hide module source and object paths
1807 -fmax-refinement-hole-fits=⟨n⟩
1809 default: 6. Set the maximum number of refinement hole fits for
1810 typed holes to display in type error messages.
1811 -fmax-relevant-binds=⟨n⟩
1813 default: 6. Set the maximum number of bindings to display in
1814 type error messages.
1815 -fmax-valid-hole-fits=⟨n⟩
1817 default: 6. Set the maximum number of valid hole fits for typed
1818 holes to display in type error messages.
1819 -fno-show-valid-hole-fits
1821 Disables showing a list of valid hole fits for typed holes in
1822 type error messages.
1823 -fno-sort-valid-hole-fits
1825 Disables the sorting of the list of valid hole fits for typed
1826 holes in type error messages.
1827 -fprint-equality-relations
1829 Distinguish between equality relations when printing
1830 -fprint-expanded-synonyms
1832 In type errors, also print type-synonym-expanded types.
1833 -fprint-explicit-coercions
1835 Print coercions in types
1836 -fprint-explicit-foralls
1838 Print explicit forall quantification in types. See also -XEx‐
1839 plicitForAll
1840 -fprint-explicit-kinds
1842 Print explicit kind foralls and kind arguments in types. See
1843 also -XKindSignatures
1844 -fprint-explicit-runtime-reps
1846 Print RuntimeRep variables in types which are runtime-represen‐
1847 tation polymorphic.
1848 -fprint-explicit-runtime-reps
1850 Print RuntimeRep variables in types which are runtime-represen‐
1851 tation polymorphic.
1852 -fprint-potential-instances
1854 display all available instances in type error messages
1855 -fprint-typechecker-elaboration
1857 Print extra information from typechecker.
1858 -fprint-unicode-syntax
1860 Use unicode syntax when printing expressions, types and kinds.
1861 See also -XUnicodeSyntax
1862 -frefinement-level-hole-fits=⟨n⟩
1864 default: off. Sets the level of refinement of the refinement
1865 hole fits, where level n means that hole fits of up to n holes
1866 will be considered.
1867 -freverse-errors
1869 Output errors in reverse order
1870 -fshow-docs-of-hole-fits
1872 Toggles whether to show the documentation of the valid hole fits
1873 in the output.
1874 -fshow-hole-constraints
1876 Show constraints when reporting typed holes.
1877 -fshow-hole-matches-of-hole-fits
1879 Toggles whether to show the type of the additional holes in re‐
1880 finement hole fits.
1881 -fshow-provenance-of-hole-fits
1883 Toggles whether to show the provenance of the valid hole fits in
1884 the output.
1885 -fshow-type-app-of-hole-fits
1887 Toggles whether to show the type application of the valid hole
1888 fits in the output.
1889 -fshow-type-app-vars-of-hole-fits
1891 Toggles whether to show what type each quantified variable takes
1892 in a valid hole fit.
1893 -fshow-type-of-hole-fits
1895 Toggles whether to show the type of the valid hole fits in the
1896 output.
1897 -funclutter-valid-hole-fits
1899 Unclutter the list of valid hole fits by not showing provenance
1900 nor type applications of suggestions.
1901 -Rghc-timing
1903 Summarise timing stats for GHC (same as +RTS -tstderr).
1904 -v verbose mode (equivalent to -v3)
1906 -v⟨n⟩ set verbosity level
1908 Warnings
1910 -fdefer-out-of-scope-variables
1911 Convert variable out of scope variables errors into warnings.
1912 Implied by -fdefer-type-errors. See also -Wde‐
1913 ferred-out-of-scope-variables.
1914 -fdefer-type-errors
1916 Turn type errors into warnings, deferring the error until run‐
1917 time. Implies -fdefer-typed-holes and -fdefer-out-of-scope-vari‐
1918 ables. See also -Wdeferred-type-errors
1919 -fdefer-typed-holes
1921 Convert typed hole errors into warnings, deferring the error un‐
1922 til runtime. Implied by -fdefer-type-errors. See also
1923 -Wtyped-holes.
1924 -fhelpful-errors
1926 Make suggestions for mis-spelled names.
1927 -fmax-pmcheck-iterations=⟨n⟩
1929 the iteration limit for the pattern match checker
1930 -fshow-warning-groups
1932 show which group an emitted warning belongs to.
1933 -W enable normal warnings
1935 -w disable all warnings
1937 -Wall enable almost all warnings (details in options-sanity)
1939 -Wall-missed-specialisations
1941 warn when specialisation of any overloaded function fails.
1942 -Wcompat
1944 enable future compatibility warnings (details in options-sanity)
1945 -Wcpp-undef
1947 warn on uses of the #if directive on undefined identifiers
1948 -Wdeferred-out-of-scope-variables
1950 Report warnings when variable out-of-scope errors are deferred
1951 until runtime. See -fdefer-out-of-scope-variables.
1952 -Wdeferred-type-errors
1954 Report warnings when deferred type errors are enabled. This op‐
1955 tion is enabled by default. See -fdefer-type-errors.
1956 -Wdeprecated-flags
1958 warn about uses of commandline flags that are deprecated
1959 -Wdeprecations
1961 warn about uses of functions & types that have warnings or dep‐
1962 recated pragmas. Alias for -Wwarnings-deprecations
1963 -Wdodgy-exports
1965 warn about dodgy exports
1966 -Wdodgy-foreign-imports
1968 warn about dodgy foreign imports
1969 -Wdodgy-imports
1971 warn about dodgy imports
1972 -Wduplicate-constraints
1974 warn when a constraint appears duplicated in a type signature
1975 -Wduplicate-exports
1977 warn when an entity is exported multiple times
1978 -Wempty-enumerations
1980 warn about enumerations that are empty
1981 -Werror
1983 make warnings fatal
1984 -Weverything
1986 enable all warnings supported by GHC
1987 -Whi-shadowing
1989 warn when a .hi file in the current directory shadows a library
1990 -Widentities
1992 warn about uses of Prelude numeric conversions that are probably
1993 the identity (and hence could be omitted)
1994 -Wimplicit-kind-vars
1996 warn when kind variables are brought into scope implicitly de‐
1997 spite the "forall-or-nothing" rule
1998 -Wimplicit-prelude
2000 warn when the Prelude is implicitly imported
2001 -Winaccessible-code
2003 warn about inaccessible code
2004 -Wincomplete-patterns
2006 warn when a pattern match could fail
2007 -Wincomplete-record-updates
2009 warn when a record update could fail
2010 -Wincomplete-uni-patterns
2012 warn when a pattern match in a lambda expression or pattern
2013 binding could fail
2014 -Winline-rule-shadowing
2016 Warn if a rewrite RULE might fail to fire because the function
2017 might be inlined before the rule has a chance to fire. See
2018 rules-inline.
2019 -Wmissed-extra-shared-lib
2021 Warn when GHCi can't load a shared lib.
2022 -Wmissed-specialisations
2024 warn when specialisation of an imported, overloaded function
2025 fails.
2026 -Wmissing-deriving-strategies
2028 warn when a deriving clause is missing a deriving strategy
2029 -Wmissing-export-lists
2031 warn when a module declaration does not explicitly list all ex‐
2032 ports
2033 -Wmissing-exported-signatures
2035 warn about top-level functions without signatures, only if they
2036 are exported. takes precedence over -Wmissing-signatures
2037 -Wmissing-exported-sigs
2039 (deprecated) warn about top-level functions without signatures,
2040 only if they are exported. takes precedence over -Wmissing-sig‐
2041 natures
2042 -Wmissing-fields
2044 warn when fields of a record are uninitialised
2045 -Wmissing-home-modules
2047 warn when encountering a home module imported, but not listed on
2048 the command line. Useful for cabal to ensure GHC won't pick up
2049 modules, not listed neither in exposed-modules, nor in
2050 other-modules.
2051 -Wmissing-import-lists
2053 warn when an import declaration does not explicitly list all the
2054 names brought into scope
2055 -Wmissing-local-signatures
2057 warn about polymorphic local bindings without signatures
2058 -Wmissing-local-sigs
2060 (deprecated) warn about polymorphic local bindings without sig‐
2061 natures
2062 -Wmissing-methods
2064 warn when class methods are undefined
2065 -Wmissing-monadfail-instances
2067 Warn when a failable pattern is used in a do-block that does not
2068 have a MonadFail instance.
2069 -Wmissing-pattern-synonym-signatures
2071 warn when pattern synonyms do not have type signatures
2072 -Wmissing-signatures
2074 warn about top-level functions without signatures
2075 -Wmonomorphism-restriction
2077 warn when the Monomorphism Restriction is applied
2078 -Wname-shadowing
2080 warn when names are shadowed
2081 -Wno-compat
2083 Disables all warnings enabled by -Wcompat.
2084 -Wnoncanonical-monad-instances
2086 warn when Applicative or Monad instances have noncanonical defi‐
2087 nitions of return, pure, (>>), or (*>). See flag description in
2088 options-sanity for more details.
2089 -Wnoncanonical-monadfail-instances
2091 warn when Monad or MonadFail instances have noncanonical defini‐
2092 tions of fail. See flag description in options-sanity for more
2093 details.
2094 -Wnoncanonical-monoid-instances
2096 warn when Semigroup or Monoid instances have noncanonical defi‐
2097 nitions of (<>) or mappend. See flag description in op‐
2098 tions-sanity for more details.
2099 -Worphans
2101 warn when the module contains orphan instance declarations or
2102 rewrite rules
2103 -Woverflowed-literals
2105 warn about literals that will overflow their type
2106 -Woverlapping-patterns
2108 warn about overlapping patterns
2109 -Wpartial-fields
2111 warn when defining a partial record field.
2112 -Wpartial-type-signatures
2114 warn about holes in partial type signatures when -XPartialTypeS‐
2115 ignatures is enabled. Not applicable when -XPartialTypesigna‐
2116 tures is not enabled, in which case errors are generated for
2117 such holes. See partial-type-signatures.
2118 -Wredundant-constraints
2120 Have the compiler warn about redundant constraints in type sig‐
2121 natures.
2122 -Wsafe warn if the module being compiled is regarded to be safe.
2124 -Wsemigroup
2126 warn when a Monoid is not Semigroup, and on non- Semigroup defi‐
2127 nitions of (<>)?
2128 -Wsimplifiable-class-constraints
2130 Warn about class constraints in a type signature that can be
2131 simplified using a top-level instance declaration.
2132 -Wspace-after-bang
2134 warn for missing space before the second argument of an infix
2135 definition of (!) when -XBangPatterns are not enabled
2136 -Wstar-binder
2138 warn about binding the (*) type operator despite -XStarIsType
2139 -Wstar-is-type
2141 warn when * is used to mean Data.Kind.Type
2142 -Wtabs warn if there are tabs in the source file
2144 -Wtrustworthy-safe
2146 warn if the module being compiled is marked as Trustworthy but
2147 it could instead be marked as Safe, a more informative bound.
2148 -Wtype-defaults
2150 warn when defaulting happens
2151 -Wtyped-holes
2153 Report warnings when typed hole errors are deferred until run‐
2154 time. See -fdefer-typed-holes.
2155 -Wunbanged-strict-patterns
2157 warn on pattern bind of unlifted variable that is neither bare
2158 nor banged
2159 -Wunrecognised-pragmas
2161 warn about uses of pragmas that GHC doesn't recognise
2162 -Wunrecognised-warning-flags
2164 throw a warning when an unreconised -W... flag is encountered on
2165 the command line.
2166 -Wunsafe
2168 warn if the module being compiled is regarded to be unsafe. See
2169 safe-haskell
2170 -Wunsupported-calling-conventions
2172 warn about use of an unsupported calling convention
2173 -Wunsupported-llvm-version
2175 Warn when using -fllvm with an unsupported version of LLVM.
2176 -Wunticked-promoted-constructors
2178 warn if promoted constructors are not ticked
2179 -Wunused-binds
2181 warn about bindings that are unused. Alias for
2182 -Wunused-top-binds, -Wunused-local-binds and -Wunused-pat‐
2183 tern-binds
2184 -Wunused-do-bind
2186 warn about do bindings that appear to throw away values of types
2187 other than ()
2188 -Wunused-foralls
2190 warn about type variables in user-written forall\s that are un‐
2191 used
2192 -Wunused-imports
2194 warn about unnecessary imports
2195 -Wunused-local-binds
2197 warn about local bindings that are unused
2198 -Wunused-matches
2200 warn about variables in patterns that aren't used
2201 -Wunused-pattern-binds
2203 warn about pattern match bindings that are unused
2204 -Wunused-top-binds
2206 warn about top-level bindings that are unused
2207 -Wunused-type-patterns
2209 warn about unused type variables which arise from patterns in in
2210 type family and data family instances
2211 -Wwarn make warnings non-fatal
2213 -Wwarnings-deprecations
2215 warn about uses of functions & types that have warnings or dep‐
2216 recated pragmas
2217 -Wwrong-do-bind
2219 warn about do bindings that appear to throw away monadic values
2220 that you should have bound instead
2221
2223 Copyright 2015. The University Court of the University of Glasgow. All
2224 rights reserved.
2225
2227 The GHC Team
2228
2230 2021, GHC Team
22318.8.4 Jan 26, 2021 GHC(1)