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 -fasm -fllvm -fno-code -fwrite-interface -fbyte-code -fob‐
53 ject-code -g⟨n⟩ -dynamic -dynamic-too
54 Debugging the compiler
56 -dcore-lint -ddump-to-file -ddump-asm -ddump-bcos
57 -ddump-cmm-from-stg -ddump-cmm-verbose -ddump-cmm
58 -ddump-core-stats -ddump-cse -ddump-deriv -ddump-ds -ddump-for‐
59 eign -ddump-hpc -ddump-inlinings -ddump-llvm -ddump-occur-anal
60 -ddump-opt-cmm -ddump-parsed -ddump-prep -ddump-rn
61 -ddump-rule-firings -ddump-rule-rewrites -ddump-rules
62 -ddump-vect -ddump-simpl -ddump-simpl-iterations -ddump-spec
63 -ddump-splices -ddump-stg -ddump-stranal -ddump-str-signatures
64 -ddump-tc -dth-dec-file=⟨file⟩ -ddump-types -ddump-worker-wrap‐
65 per -ddump-if-trace -ddump-tc-trace -ddump-vt-trace
66 -ddump-rn-trace -ddump-rn-stats -ddump-simpl-stats
67 -dno-debug-output -dppr-debug -dppr-user-length -dppr-cols=⟨n⟩
68 -dppr-case-as-let -dsuppress-all -dsuppress-uniques -dsup‐
69 press-idinfo -dsuppress-unfoldings -dsuppress-module-prefixes
70 -dsuppress-type-signatures -dsuppress-type-applications -dsup‐
71 press-coercions -dsource-stats -dcmm-lint -dstg-lint -dstg-stats
72 -dverbose-core2core -dverbose-stg2stg -dshow-passes -dfast‐
73 string-stats -frule-check
74 C pre-processor
76 -cpp -D⟨symbol⟩[=⟨value⟩] -U⟨symbol⟩ -I⟨dir⟩
77 Finding imports
79 -i⟨dir⟩[:⟨dir⟩]* -i
80 Interactive mode
82 -ignore-dot-ghci -ghci-script -fbreak-on-error -fbreak-on-excep‐
83 tion -fghci-hist-size=⟨n⟩ -fprint-evld-with-show
84 -fprint-bind-result -fno-print-bind-contents
85 -fno-implicit-import-qualified -interactive-print ⟨expr⟩
86 Interface files
88 -ddump-hi -ddump-hi-diffs -ddump-minimal-imports --show-iface
89 ⟨file⟩
90 Keeping intermediate files
92 -keep-hc-file, -keep-hc-files -keep-hi-files -keep-llvm-file,
93 -keep-llvm-files -keep-o-files -keep-s-file, -keep-s-files
94 -keep-tmp-files
95 Language options
97 -fconstraint-solver-iterations=⟨n⟩ -freduction-depth=⟨n⟩ -fcon‐
98 text-stack=⟨n⟩ -fglasgow-exts -firrefutable-tuples -fpack‐
99 age-trust -ftype-function-depth=⟨n⟩ -XAllowAmbiguousTypes -XAr‐
100 rows -XApplicativeDo -XAutoDeriveTypeable -XBangPatterns -XBina‐
101 ryLiterals -XCApiFFI -XConstrainedClassMethods -XConstraintKinds
102 -XCPP -XDataKinds -XDefaultSignatures -XDeriveAnyClass -XDerive‐
103 DataTypeable -XDeriveFunctor -XDeriveFoldable -XDeriveGeneric
104 -XDeriveGeneric -XDeriveLift -XDeriveTraversable -XDeriv‐
105 ingStrategies -XDisambiguateRecordFields -XEmptyCase -XEmpty‐
106 DataDecls -XExistentialQuantification -XExplicitForAll -XExplic‐
107 itNamespaces -XExtendedDefaultRules -XFlexibleContexts -XFlexi‐
108 bleInstances -XForeignFunctionInterface -XFunctionalDependencies
109 -XGADTs -XGADTSyntax -XGeneralizedNewtypeDeriving -XGenerics
110 -XImplicitParams -XNoImplicitPrelude -XImpredicativeTypes -XIn‐
111 coherentInstances -XTypeFamilyDependencies -XInstanceSigs -XIn‐
112 terruptibleFFI -XKindSignatures -XLambdaCase -XLiberalTypeSyn‐
113 onyms -XMagicHash -XMonadComprehensions -XMonoLocalBinds
114 -XNoMonomorphismRestriction -XMultiParamTypeClasses -XMultiWayIf
115 -XNamedFieldPuns -XNamedWildCards -XNegativeLiterals
116 -XNPlusKPatterns -XNullaryTypeClasses -XNumDecimals -XOverlap‐
117 pingInstances -XOverloadedLabels -XOverloadedLists -XOverloaded‐
118 Strings -XPackageImports -XParallelArrays -XParallelListComp
119 -XPartialTypeSignatures -XNoPatternGuards -XPatternSynonyms
120 -XPolyKinds -XPolymorphicComponents -XPostfixOperators
121 -XQuasiQuotes -XRank2Types -XRankNTypes -XRebindableSyntax
122 -XRecordWildCards -XRecursiveDo -XRoleAnnotations -XSafe
123 -XScopedTypeVariables -XStandaloneDeriving -XStaticPointers
124 -XStrictData -XTemplateHaskell -XTemplateHaskellQuotes -XNoTra‐
125 ditionalRecordSyntax -XTransformListComp -XTrustworthy -XTuple‐
126 Sections -XTypeFamilies -XTypeInType -XTypeOperators -XTypeSyn‐
127 onymInstances -XUnboxedTuples -XUnboxedSums -XUndecidableIn‐
128 stances -XUnicodeSyntax -XUnliftedFFITypes -XUnsafe -XViewPat‐
129 terns
130 Linking options
132 -shared -staticlib -fPIC -fPIE -pie -dynload -framework ⟨name⟩
133 -framework-path ⟨dir⟩ -l ⟨lib⟩ -L ⟨dir⟩ -main-is ⟨thing⟩
134 --mk-dll -no-hs-main -rtsopts[=⟨none|some|all⟩]
135 -with-rtsopts=⟨opts⟩ -no-rtsopts-suggestions -no-link
136 -split-objs -split-sections -static -threaded -debug -ticky
137 -eventlog -fno-gen-manifest -fno-embed-manifest
138 -fno-shared-implib -dylib-install-name ⟨path⟩ -rdynamic
139 Miscellaneous options
141 -j[⟨n⟩] -fno-hi-version-check -fhistory-size -fno-ghci-history
142 -fno-ghci-sandbox -flocal-ghci-history
143 Modes of operation
145 --help,-? --interactive --make -e ⟨expr⟩ --show-iface ⟨file⟩ -M
146 --frontend ⟨module⟩ --supported-extensions, --supported-lan‐
147 guages --show-options --info --version, -V --numeric-version
148 --print-libdir
149 Individual optimizations
151 -fcall-arity -fcase-merge -fcase-folding -fcmm-elim-com‐
152 mon-blocks -fcmm-sink -fcpr-anal -fcse -fdicts-cheap
153 -fdicts-strict -fdmd-tx-dict-sel -fdo-eta-reduction
154 -fdo-lambda-eta-expansion -feager-blackholing -fenable-re‐
155 write-rules -fexcess-precision -fexpose-all-unfoldings
156 -ffloat-in -ffull-laziness -ffun-to-thunk -fignore-asserts -fig‐
157 nore-interface-pragmas -flate-dmd-anal -fliberate-case -fliber‐
158 ate-case-threshold=⟨n⟩ -floopification
159 -fmax-inline-alloc-size=⟨n⟩ -fmax-inline-memcpy-insns=⟨n⟩
160 -fmax-inline-memset-insns=⟨n⟩ -fmax-relevant-binds=⟨n⟩
161 -fmax-uncovered-patterns=⟨n⟩ -fmax-simplifier-iterations=⟨n⟩
162 -fmax-worker-args=⟨n⟩ -fno-opt-coercion -fno-pre-inlining
163 -fno-state-hack -fomit-interface-pragmas -fomit-yields -fopti‐
164 mal-applicative-do -fpedantic-bottoms -fregs-graph -fregs-itera‐
165 tive -fsimplifier-phases=⟨n⟩ -fsimpl-tick-factor=⟨n⟩ -fspec-con‐
166 str -fspec-constr-count=⟨n⟩ -fspec-constr-threshold=⟨n⟩ -fspe‐
167 cialise -fcross-module-specialise -fstatic-argument-transforma‐
168 tion -fstrictness -fstrictness-before=⟨n⟩ -fun‐
169 box-small-strict-fields -funbox-strict-fields -funfolding-cre‐
170 ation-threshold=⟨n⟩ -funfolding-dict-discount=⟨n⟩ -funfold‐
171 ing-fun-discount=⟨n⟩ -funfolding-keeness-factor=⟨n⟩ -funfold‐
172 ing-use-threshold=⟨n⟩ -fvectorisation-avoidance -fvectorise
173 -fworker-wrapper
174 Optimization levels
176 -O0 -O, -O1 -O2 -Odph
177 Package options
179 -this-unit-id ⟨unit-id⟩ -package ⟨pkg⟩ -hide-all-packages
180 -hide-package ⟨pkg⟩ -ignore-package ⟨pkg⟩ -package-db ⟨file⟩
181 -clear-package-db -no-global-package-db -global-package-db
182 -no-user-package-db -user-package-db -no-auto-link-packages
183 -trust ⟨pkg⟩ -distrust ⟨pkg⟩ -distrust-all -package-env
184 ⟨file⟩|⟨name⟩
185 Phases of compilation
187 -F -E -C -S -c -x ⟨suffix⟩
188 Overriding external programs
190 -pgmL ⟨cmd⟩ -pgmP ⟨cmd⟩ -pgmc ⟨cmd⟩ -pgmlo ⟨cmd⟩ -pgmlc ⟨cmd⟩
191 -pgms ⟨cmd⟩ -pgma ⟨cmd⟩ -pgml ⟨cmd⟩ -pgmdll ⟨cmd⟩ -pgmF ⟨cmd⟩
192 -pgmwindres ⟨cmd⟩ -pgmlibtool ⟨cmd⟩
193 Phase-specific options
195 -optL ⟨option⟩ -optP ⟨option⟩ -optF ⟨option⟩ -optc ⟨option⟩
196 -optlo ⟨option⟩ -optlc ⟨option⟩ -opta ⟨option⟩ -optl ⟨option⟩
197 -optdll ⟨option⟩ -optwindres ⟨option⟩
198 Platform-specific options
200 -msse2 -msse4.2
201 Compiler plugins
203 -fplugin=⟨module⟩ -fplugin-opt=⟨module⟩:⟨args⟩
204 Profiling
206 -prof -fprof-auto -fprof-auto-top -fprof-auto-exported
207 -fprof-cafs -fno-prof-count-entries -ticky
208 Program coverage
210 -fhpc -hpcdir ⟨dir⟩
211 Recompilation checking
213 -fforce-recomp
214 Redirecting output
216 -hcsuf ⟨suffix⟩ -hidir ⟨dir⟩ -hisuf ⟨suffix⟩ -o ⟨file⟩ -odir
217 ⟨dir⟩ -ohi ⟨file⟩ -osuf ⟨suffix⟩ -stubdir ⟨dir⟩ -dumpdir ⟨dir⟩
218 -outputdir ⟨dir⟩ -dyno ⟨file⟩ -dynosuf ⟨suffix⟩ -dynhisuf ⟨suf‐
219 fix⟩
220 Temporary files
222 -tmpdir ⟨dir⟩
223 Verbosity options
225 -v -v ⟨n⟩ -fhide-source-paths -fprint-potential-instances
226 -fprint-explicit-foralls -fprint-explicit-kinds
227 -fprint-explicit-runtime-reps -fprint-unicode-syntax
228 -fprint-expanded-synonyms -fprint-typechecker-elaboration -fdi‐
229 agnostics-color=(always|auto|never) -f[no-]diagnos‐
230 tics-show-caret -ferror-spans -Rghc-timing -fshow-hole-con‐
231 straints -fshow-loaded-modules
232 Warnings
234 -W -w -Wall -Wcompat -Werror -Werror=⟨wflag⟩ -Wwarn
235 -Wwarn=⟨wflag⟩ -Wunrecognised-warning-flags -fshow-warn‐
236 ing-groups -fdefer-type-errors -fdefer-typed-holes -fde‐
237 fer-out-of-scope-variables -fhelpful-errors -freverse-errors
238 -fmax-errors -Wdeprecated-flags -Wduplicate-constraints -Wdupli‐
239 cate-exports -Whi-shadowing -Widentities -Wimplicit-prelude
240 -Wincomplete-patterns -Wincomplete-uni-patterns
241 -fmax-pmcheck-iterations=⟨n⟩ -Wincomplete-record-updates -Wmiss‐
242 ing-fields -Wmissing-import-lists -Wmissing-methods -Wmiss‐
243 ing-signatures -Wmissing-exported-sigs -Wmissing-exported-signa‐
244 tures -Wmissing-local-sigs -Wmissing-local-signatures -Wmiss‐
245 ing-monadfail-instances -Wsemigroup -Wmissed-specialisations
246 -Wall-missed-specialisations -Wmonomorphism-restriction
247 -Wname-shadowing -Wnoncanonical-monad-instances -Wnoncanoni‐
248 cal-monadfail-instances -Wnoncanonical-monoid-instances -Wor‐
249 phans -Woverlapping-patterns -Wtabs -Wtype-defaults -Wunrecog‐
250 nised-pragmas -Wunticked-promoted-constructors -Wunused-binds
251 -Wunused-top-binds -Wunused-local-binds -Wunused-pattern-binds
252 -Wunused-imports -Wunused-matches -Wunused-foralls
253 -Wunused-type-variables -Wunused-do-bind -Wwrong-do-bind -Wun‐
254 safe -Wsafe -Wtrustworthy-safe -Wwarnings-deprecations -Wdepre‐
255 cations -Wamp -Wredundant-constraints -Wdeferred-type-errors
256 -Wtyped-holes -Wdeferred-out-of-scope-variables -Wpar‐
257 tial-type-signatures -Wderiving-typeable -Wmissing-home-modules
258 Code generation
260 -fasm Use the native code generator
261 -fllvm Compile using the LLVM code generator
263 -fno-code
265 Omit code generation
266 -fwrite-interface
268 Always write interface files
269 -fbyte-code
271 Generate byte-code
272 -fobject-code
274 Generate object code
275 -g⟨n⟩ Produce DWARF debug information in compiled object files.⟨n⟩ can
277 be 0, 1, or 2, with higher numbers producing richer output. If
278 ⟨n⟩ is omitted level 2 is assumed.
279 -dynamic
281 Build dynamically-linked object files and executables
282 -dynamic-too
284 Build dynamic object files as well as static object files during
285 compilation
286 Debugging the compiler
288 -dcore-lint
289 Turn on internal sanity checking
290 -ddump-to-file
292 Dump to files instead of stdout
293 -ddump-asm
295 Dump assembly
296 -ddump-bcos
298 Dump interpreter byte code
299 -ddump-cmm-from-stg
301 Dump STG-to-C-- output
302 -ddump-cmm-verbose
304 Show output from each C-- pipeline pass
305 -ddump-cmm
307 Dump the final C-- output
308 -ddump-core-stats
310 Print a one-line summary of the size of the Core program at the
311 end of the optimisation pipeline
312 -ddump-cse
314 Dump CSE output
315 -ddump-deriv
317 Dump deriving output
318 -ddump-ds
320 Dump desugarer output
321 -ddump-foreign
323 Dump foreign export stubs
324 -ddump-hpc
326 Dump after instrumentation for program coverage
327 -ddump-inlinings
329 Dump inlining info
330 -ddump-llvm
332 Dump LLVM intermediate code. Implies -fllvm.
333 -ddump-occur-anal
335 Dump occurrence analysis output
336 -ddump-opt-cmm
338 Dump the results of C-- to C-- optimising passes
339 -ddump-parsed
341 Dump parse tree
342 -ddump-prep
344 Dump prepared core
345 -ddump-rn
347 Dump renamer output
348 -ddump-rule-firings
350 Dump rule firing info
351 -ddump-rule-rewrites
353 Dump detailed rule firing info
354 -ddump-rules
356 Dump rules
357 -ddump-vect
359 Dump vectoriser input and output
360 -ddump-simpl
362 Dump final simplifier output
363 -ddump-simpl-iterations
365 Dump output from each simplifier iteration
366 -ddump-spec
368 Dump specialiser output
369 -ddump-splices
371 Dump TH spliced expressions, and what they evaluate to
372 -ddump-stg
374 Dump final STG
375 -ddump-stranal
377 Dump strictness analyser output
378 -ddump-str-signatures
380 Dump strictness signatures
381 -ddump-tc
383 Dump typechecker output
384 -dth-dec-file=⟨file⟩
386 Show evaluated TH declarations in a .th.hs file
387 -ddump-types
389 Dump type signatures
390 -ddump-worker-wrapper
392 Dump worker-wrapper output
393 -ddump-if-trace
395 Trace interface files
396 -ddump-tc-trace
398 Trace typechecker
399 -ddump-vt-trace
401 Trace vectoriser
402 -ddump-rn-trace
404 Trace renamer
405 -ddump-rn-stats
407 Renamer stats
408 -ddump-simpl-stats
410 Dump simplifier stats
411 -dno-debug-output
413 Suppress unsolicited debugging output
414 -dppr-debug
416 Turn on debug printing (more verbose)
417 -dppr-user-length
419 Set the depth for printing expressions in error msgs
420 -dppr-cols=⟨n⟩
422 Set the width of debugging output. For example -dppr-cols200
423 -dppr-case-as-let
425 Print single alternative case expressions as strict lets.
426 -dsuppress-all
428 In core dumps, suppress everything (except for uniques) that is
429 suppressible.
430 -dsuppress-uniques
432 Suppress the printing of uniques in debug output (easier to use
433 diff)
434 -dsuppress-idinfo
436 Suppress extended information about identifiers where they are
437 bound
438 -dsuppress-unfoldings
440 Suppress the printing of the stable unfolding of a variable at
441 its binding site
442 -dsuppress-module-prefixes
444 Suppress the printing of module qualification prefixes
445 -dsuppress-type-signatures
447 Suppress type signatures
448 -dsuppress-type-applications
450 Suppress type applications
451 -dsuppress-coercions
453 Suppress the printing of coercions in Core dumps to make them
454 shorter
455 -dsource-stats
457 Dump haskell source stats
458 -dcmm-lint
460 C-- pass sanity checking
461 -dstg-lint
463 STG pass sanity checking
464 -dstg-stats
466 Dump STG stats
467 -dverbose-core2core
469 Show output from each core-to-core pass
470 -dverbose-stg2stg
472 Show output from each STG-to-STG pass
473 -dshow-passes
475 Print out each pass name as it happens
476 -dfaststring-stats
478 Show statistics for fast string usage when finished
479 -frule-check
481 Report sites with rules that could have fired but didn't. Takes
482 a string argument.
483 C pre-processor
485 -cpp Run the C pre-processor on Haskell source files
486 -D⟨symbol⟩[=⟨value⟩]
488 Define a symbol in the C pre-processor
489 -U⟨symbol⟩
491 Undefine a symbol in the C pre-processor
492 -I⟨dir⟩
494 Add ⟨dir⟩ to the directory search list for #include files
495 Finding imports
497 -i⟨dir⟩[:⟨dir⟩]*
498 add ⟨dir⟩, ⟨dir2⟩, etc. to import path
499 -i Empty the import directory list
501 Interactive mode
503 -ignore-dot-ghci
504 Disable reading of .ghci files
505 -ghci-script
507 Read additional .ghci files
508 -fbreak-on-error
510 Break on uncaught exceptions and errors
511 -fbreak-on-exception
513 Break on any exception thrown
514 -fghci-hist-size=⟨n⟩
516 Set the number of entries GHCi keeps for :history. See
517 ghci-debugger.
518 -fprint-evld-with-show
520 Enable usage of Show instances in :print. See breakpoints.
521 -fprint-bind-result
523 Turn on printing of binding results in GHCi
524 -fno-print-bind-contents
526 Turn off printing of binding contents in GHCi
527 -fno-implicit-import-qualified
529 Turn off implicit qualified import of everything in GHCi
530 -interactive-print ⟨expr⟩
532 Select the function to use for printing evaluated expressions in
533 GHCi
534 Interface files
536 -ddump-hi
537 Dump the new interface to stdout
538 -ddump-hi-diffs
540 Show the differences vs. the old interface
541 -ddump-minimal-imports
543 Dump a minimal set of imports
544 --show-iface ⟨file⟩
546 See modes.
547 Keeping intermediate files
549 -keep-hc-file, -keep-hc-files
550 Retain intermediate .hc files.
551 -keep-hi-files
553 Retain intermediate .hi files (the default).
554 -keep-llvm-file, -keep-llvm-files
556 Retain intermediate LLVM .ll files. Implies -fllvm.
557 -keep-o-files
559 Retain intermediate .o files (the default).
560 -keep-s-file, -keep-s-files
562 Retain intermediate .s files.
563 -keep-tmp-files
565 Retain all intermediate temporary files.
566 Language options
568 -fconstraint-solver-iterations=⟨n⟩
569 default: 4. Set the iteration limit for the type-constraint
570 solver. Typically one iteration suffices; so please yell if you
571 find you need to set it higher than the default. Zero means
572 infinity.
573 -freduction-depth=⟨n⟩
575 default: 200. Set the limit for type simplification. Zero means
576 infinity.
577 -fcontext-stack=⟨n⟩
579 Deprecated. Use -freduction-depth=⟨n⟩ instead.
580 -fglasgow-exts
582 Deprecated. Enable most language extensions; see options-lan‐
583 guage for exactly which ones.
584 -firrefutable-tuples
586 Make tuple pattern matching irrefutable
587 -fpackage-trust
589 Enable Safe Haskell trusted package requirement for trustworthy
590 modules.
591 -ftype-function-depth=⟨n⟩
593 Deprecated. Use -freduction-depth=⟨n⟩ instead.
594 -XAllowAmbiguousTypes
596 Allow the user to write ambiguous types, and the type inference
597 engine to infer them.
598 -XArrows
600 Enable arrow notation extension
601 -XApplicativeDo
603 Enable Applicative do-notation desugaring
604 -XAutoDeriveTypeable
606 As of GHC 7.10, this option is not needed, and should not be
607 used. Previously this would automatically derive Typeable
608 instances for every datatype and type class declaration. Implies
609 -XDeriveDataTypeable.
610 -XBangPatterns
612 Enable bang patterns.
613 -XBinaryLiterals
615 Enable support for binary literals.
616 -XCApiFFI
618 Enable the CAPI calling convention.
619 -XConstrainedClassMethods
621 Enable constrained class methods.
622 -XConstraintKinds
624 Enable a kind of constraints.
625 -XCPP Enable the C preprocessor.
627 -XDataKinds
629 Enable datatype promotion.
630 -XDefaultSignatures
632 Enable default signatures.
633 -XDeriveAnyClass
635 Enable deriving for any class.
636 -XDeriveDataTypeable
638 Enable deriving for the Data class. Implied by -XAutoDeriveTy‐
639 peable.
640 -XDeriveFunctor
642 Enable deriving for the Functor class. Implied by -XDerive‐
643 Traversable.
644 -XDeriveFoldable
646 Enable deriving for the Foldable class. Implied by -XDerive‐
647 Traversable.
648 -XDeriveGeneric
650 Enable deriving for the Generic class.
651 -XDeriveGeneric
653 Enable deriving for the Generic class.
654 -XDeriveLift
656 Enable deriving for the Lift class
657 -XDeriveTraversable
659 Enable deriving for the Traversable class. Implies -XDeriveFunc‐
660 tor and -XDeriveFoldable.
661 -XDerivingStrategies
663 Enables deriving strategies.
664 -XDisambiguateRecordFields
666 Enable record field disambiguation. Implied by -XRecordWild‐
667 Cards.
668 -XEmptyCase
670 Allow empty case alternatives.
671 -XEmptyDataDecls
673 Enable empty data declarations.
674 -XExistentialQuantification
676 Enable existential quantification.
677 -XExplicitForAll
679 Enable explicit universal quantification. Implied by -XScoped‐
680 TypeVariables, -XLiberalTypeSynonyms, -XRankNTypes and -XExis‐
681 tentialQuantification.
682 -XExplicitNamespaces
684 Enable using the keyword type to specify the namespace of
685 entries in imports and exports (explicit-namespaces). Implied by
686 -XTypeOperators and -XTypeFamilies.
687 -XExtendedDefaultRules
689 Use GHCi's extended default rules in a normal module.
690 -XFlexibleContexts
692 Enable flexible contexts. Implied by -XImplicitParams.
693 -XFlexibleInstances
695 Enable flexible instances. Implies -XTypeSynonymInstances.
696 Implied by -XImplicitParams.
697 -XForeignFunctionInterface
699 Enable foreign function interface.
700 -XFunctionalDependencies
702 Enable functional dependencies. Implies -XMultiParamTypeClasses.
703 -XGADTs
705 Enable generalised algebraic data types. Implies -XGADTSyntax
706 and -XMonoLocalBinds.
707 -XGADTSyntax
709 Enable generalised algebraic data type syntax.
710 -XGeneralizedNewtypeDeriving
712 Enable newtype deriving.
713 -XGenerics
715 Deprecated, does nothing. No longer enables generic classes. See
716 also GHC's support for generic programming.
717 -XImplicitParams
719 Enable Implicit Parameters. Implies -XFlexibleContexts and
720 -XFlexibleInstances.
721 -XNoImplicitPrelude
723 Don't implicitly import Prelude. Implied by -XRebindableSyntax.
724 -XImpredicativeTypes
726 Enable impredicative types. Implies -XRankNTypes.
727 -XIncoherentInstances
729 Enable incoherent instances. Implies -XOverlappingInstances.
730 -XTypeFamilyDependencies
732 Enable injective type families. Implies -XTypeFamilies.
733 -XInstanceSigs
735 Enable instance signatures.
736 -XInterruptibleFFI
738 Enable interruptible FFI.
739 -XKindSignatures
741 Enable kind signatures. Implied by -XTypeFamilies and
742 -XPolyKinds.
743 -XLambdaCase
745 Enable lambda-case expressions.
746 -XLiberalTypeSynonyms
748 Enable liberalised type synonyms.
749 -XMagicHash
751 Allow # as a postfix modifier on identifiers.
752 -XMonadComprehensions
754 Enable monad comprehensions.
755 -XMonoLocalBinds
757 Enable do not generalise local bindings. Implied by -XTypeFami‐
758 lies and -XGADTs.
759 -XNoMonomorphismRestriction
761 Disable the monomorphism restriction.
762 -XMultiParamTypeClasses
764 Enable multi parameter type classes. Implied by -XFunctionalDe‐
765 pendencies.
766 -XMultiWayIf
768 Enable multi-way if-expressions.
769 -XNamedFieldPuns
771 Enable record puns.
772 -XNamedWildCards
774 Enable named wildcards.
775 -XNegativeLiterals
777 Enable support for negative literals.
778 -XNPlusKPatterns
780 Enable support for n+k patterns. Implied by -XHaskell98.
781 -XNullaryTypeClasses
783 Deprecated, does nothing. nullary (no parameter) type classes
784 are now enabled using -XMultiParamTypeClasses.
785 -XNumDecimals
787 Enable support for 'fractional' integer literals.
788 -XOverlappingInstances
790 Enable overlapping instances.
791 -XOverloadedLabels
793 Enable overloaded labels.
794 -XOverloadedLists
796 Enable overloaded lists.
797 -XOverloadedStrings
799 Enable overloaded string literals.
800 -XPackageImports
802 Enable package-qualified imports.
803 -XParallelArrays
805 Enable parallel arrays. Implies -XParallelListComp.
806 -XParallelListComp
808 Enable parallel list comprehensions. Implied by -XParallelAr‐
809 rays.
810 -XPartialTypeSignatures
812 Enable partial type signatures.
813 -XNoPatternGuards
815 Disable pattern guards. Implied by -XHaskell98.
816 -XPatternSynonyms
818 Enable pattern synonyms.
819 -XPolyKinds
821 Enable kind polymorphism. Implies -XKindSignatures.
822 -XPolymorphicComponents
824 Enable polymorphic components for data constructors. Synonym for
825 -XRankNTypes.
826 -XPostfixOperators
828 Enable postfix operators.
829 -XQuasiQuotes
831 Enable quasiquotation.
832 -XRank2Types
834 Enable rank-2 types. Synonym for -XRankNTypes.
835 -XRankNTypes
837 Enable rank-N types. Implied by -XImpredicativeTypes.
838 -XRebindableSyntax
840 Employ rebindable syntax. Implies -XNoImplicitPrelude.
841 -XRecordWildCards
843 Enable record wildcards. Implies -XDisambiguateRecordFields.
844 -XRecursiveDo
846 Enable recursive do (mdo) notation.
847 -XRoleAnnotations
849 Enable role annotations.
850 -XSafe Enable the Safe Haskell Safe mode.
852 -XScopedTypeVariables
854 Enable lexically-scoped type variables.
855 -XStandaloneDeriving
857 Enable standalone deriving.
858 -XStaticPointers
860 Enable static pointers.
861 -XStrictData
863 Enable default strict datatype fields.
864 -XTemplateHaskell
866 Enable Template Haskell.
867 -XTemplateHaskellQuotes
869 Enable quotation subset of Template Haskell.
870 -XNoTraditionalRecordSyntax
872 Disable support for traditional record syntax (as supported by
873 Haskell 98) C {f = x}
874 -XTransformListComp
876 Enable generalised list comprehensions.
877 -XTrustworthy
879 Enable the Safe Haskell Trustworthy mode.
880 -XTupleSections
882 Enable tuple sections.
883 -XTypeFamilies
885 Enable type families. Implies -XExplicitNamespaces, -XKindSigna‐
886 tures, and -XMonoLocalBinds.
887 -XTypeInType
889 Allow kinds to be used as types, including explicit kind vari‐
890 able quantification, higher-rank kinds, kind synonyms, and kind
891 families. Implies -XDataKinds, -XKindSignatures, and
892 -XPolyKinds.
893 -XTypeOperators
895 Enable type operators. Implies -XExplicitNamespaces.
896 -XTypeSynonymInstances
898 Enable type synonyms in instance heads. Implied by -XFlexibleIn‐
899 stances.
900 -XUnboxedTuples
902 Enable unboxed tuples.
903 -XUnboxedSums
905 Enable :ref: unboxed sums <unboxed-sums>.
906 -XUndecidableInstances
908 Enable undecidable instances.
909 -XUnicodeSyntax
911 Enable unicode syntax.
912 -XUnliftedFFITypes
914 Enable unlifted FFI types.
915 -XUnsafe
917 Enable Safe Haskell Unsafe mode.
918 -XViewPatterns
920 Enable view patterns.
921 Linking options
923 -shared
924 Generate a shared library (as opposed to an executable)
925 -staticlib
927 On Darwin/OS X/iOS only, generate a standalone static library
928 (as opposed to an executable). This is the usual way to compile
929 for iOS.
930 -fPIC Generate position-independent code (where available)
932 -fPIE Generate code for a position-independent executable (where
934 available)
935 -pie Instruct the linker to produce a position-independent exe‐
937 cutable.
938 -dynload
940 Selects one of a number of modes for finding shared libraries at
941 runtime.
942 -framework ⟨name⟩
944 On Darwin/OS X/iOS only, link in the framework ⟨name⟩. This
945 option corresponds to the -framework option for Apple's Linker.
946 -framework-path ⟨dir⟩
948 On Darwin/OS X/iOS only, add ⟨dir⟩ to the list of directories
949 searched for frameworks. This option corresponds to the -F
950 option for Apple's Linker.
951 -l ⟨lib⟩
953 Link in library ⟨lib⟩
954 -L ⟨dir⟩
956 Add ⟨dir⟩ to the list of directories searched for libraries
957 -main-is ⟨thing⟩
959 Set main module and function
960 --mk-dll
962 DLL-creation mode (Windows only)
963 -no-hs-main
965 Don't assume this program contains main
966 -rtsopts[=⟨none|some|all⟩]
968 Control whether the RTS behaviour can be tweaked via com‐
969 mand-lineflags and the GHCRTS environment variable. Using none
970 means no RTS flags can be given; some means only a minimum of
971 safe options can be given (the default), and all (or no argument
972 at all) means that all RTS flags are permitted.
973 -with-rtsopts=⟨opts⟩
975 Set the default RTS options to ⟨opts⟩.
976 -no-rtsopts-suggestions
978 Don't print RTS suggestions about linking with
979 -rtsopts[=⟨none|some|all⟩].
980 -no-link
982 Omit linking
983 -split-objs
985 Split objects (for libraries)
986 -split-sections
988 Split sections for link-time dead-code stripping
989 -static
991 Use static Haskell libraries
992 -threaded
994 Use the threaded runtime
995 -debug Use the debugging runtime
997 -ticky For linking, this simply implies -debug; see ticky-ticky.
999 -eventlog
1001 Enable runtime event tracing
1002 -fno-gen-manifest
1004 Do not generate a manifest file (Windows only)
1005 -fno-embed-manifest
1007 Do not embed the manifest in the executable (Windows only)
1008 -fno-shared-implib
1010 Don't generate an import library for a DLL (Windows only)
1011 -dylib-install-name ⟨path⟩
1013 Set the install name (via -install_name passed to Apple's
1014 linker), specifying the full install path of the library file.
1015 Any libraries or executables that link with it later will pick
1016 up that path as their runtime search location for it. (Darwin/OS
1017 X only)
1018 -rdynamic
1020 This instructs the linker to add all symbols, not only used
1021 ones, to the dynamic symbol table. Currently Linux and Win‐
1022 dows/MinGW32 only. This is equivalent to using -optl -rdynamic
1023 on Linux, and -optl -export-all-symbols on Windows.
1024 Miscellaneous options
1026 -j[⟨n⟩]
1027 When compiling with --make, compile ⟨n⟩ modules in parallel.
1028 -fno-hi-version-check
1030 Don't complain about .hi file mismatches
1031 -fhistory-size
1033 Set simplification history size
1034 -fno-ghci-history
1036 Do not use the load/store the GHCi command history from/to
1037 ghci_history.
1038 -fno-ghci-sandbox
1040 Turn off the GHCi sandbox. Means computations are run in the
1041 main thread, rather than a forked thread.
1042 -flocal-ghci-history
1044 Use current directory for the GHCi command history file
1045 .ghci-history.
1046 Modes of operation
1048 --help,-?
1049 Display help
1050 --interactive
1052 Interactive mode - normally used by just running ghci; see ghci
1053 for details.
1054 --make Build a multi-module Haskell program, automatically figuring out
1056 dependencies. Likely to be much easier, and faster, than using
1057 make; see make-mode for details.
1058 -e ⟨expr⟩
1060 Evaluate expr; see eval-mode for details.
1061 --show-iface ⟨file⟩
1063 display the contents of an interface file.
1064 -M generate dependency information suitable for use in a Makefile;
1066 see makefile-dependencies for details.
1067 --frontend ⟨module⟩
1069 run GHC with the given frontend plugin; see frontend_plugins for
1070 details.
1071 --supported-extensions, --supported-languages
1073 display the supported language extensions
1074 --show-options
1076 display the supported command line options
1077 --info display information about the compiler
1079 --version, -V
1081 display GHC version
1082 --numeric-version
1084 display GHC version (numeric only)
1085 --print-libdir
1087 display GHC library directory
1088 Individual optimizations
1090 -fcall-arity
1091 Enable call-arity optimisation. Implied by -O.
1092 -fcase-merge
1094 Enable case-merging. Implied by -O.
1095 -fcase-folding
1097 Enable constant folding in case expressions. Implied by -O.
1098 -fcmm-elim-common-blocks
1100 Enable Cmm common block elimination. Implied by -O.
1101 -fcmm-sink
1103 Enable Cmm sinking. Implied by -O.
1104 -fcpr-anal
1106 Turn on CPR analysis in the demand analyser. Implied by -O.
1107 -fcse Enable common sub-expression elimination. Implied by -O.
1109 -fdicts-cheap
1111 Make dictionary-valued expressions seem cheap to the optimiser.
1112 -fdicts-strict
1114 Make dictionaries strict
1115 -fdmd-tx-dict-sel
1117 Use a special demand transformer for dictionary selectors.
1118 Always enabled by default.
1119 -fdo-eta-reduction
1121 Enable eta-reduction. Implied by -O.
1122 -fdo-lambda-eta-expansion
1124 Enable lambda eta-expansion. Always enabled by default.
1125 -feager-blackholing
1127 Turn on eager blackholing
1128 -fenable-rewrite-rules
1130 Switch on all rewrite rules (including rules generated by auto‐
1131 matic specialisation of overloaded functions). Implied by -O.
1132 -fexcess-precision
1134 Enable excess intermediate precision
1135 -fexpose-all-unfoldings
1137 Expose all unfoldings, even for very large or recursive func‐
1138 tions.
1139 -ffloat-in
1141 Turn on the float-in transformation. Implied by -O.
1142 -ffull-laziness
1144 Turn on full laziness (floating bindings outwards). Implied by
1145 -O.
1146 -ffun-to-thunk
1148 Allow worker-wrapper to convert a function closure into a thunk
1149 if the function does not use any of its arguments. Off by
1150 default.
1151 -fignore-asserts
1153 Ignore assertions in the source. Implied by -O.
1154 -fignore-interface-pragmas
1156 Ignore pragmas in interface files. Implied by -O0 only.
1157 -flate-dmd-anal
1159 Run demand analysis again, at the end of the simplification
1160 pipeline
1161 -fliberate-case
1163 Turn on the liberate-case transformation. Implied by -O2.
1164 -fliberate-case-threshold=⟨n⟩
1166 default: 2000. Set the size threshold for the liberate-case
1167 transformation to ⟨n⟩
1168 -floopification
1170 Turn saturated self-recursive tail-calls into local jumps in the
1171 generated assembly. Implied by -O.
1172 -fmax-inline-alloc-size=⟨n⟩
1174 default: 128. Set the maximum size of inline array allocations
1175 to ⟨n⟩ bytes (default: 128). GHC will allocate non-pinned arrays
1176 of statically known size in the current nursery block if they're
1177 no bigger than ⟨n⟩ bytes, ignoring GC overheap. This value
1178 should be quite a bit smaller than the block size (typically:
1179 4096).
1180 -fmax-inline-memcpy-insns=⟨n⟩
1182 default: 32. Inline memcpy calls if they would generate no more
1183 than ⟨n⟩ pseudo instructions.
1184 -fmax-inline-memset-insns=⟨n⟩
1186 default: 32. Inline memset calls if they would generate no more
1187 than ⟨n⟩ pseudo instructions
1188 -fmax-relevant-binds=⟨n⟩
1190 default: 6. Set the maximum number of bindings to display in
1191 type error messages.
1192 -fmax-uncovered-patterns=⟨n⟩
1194 default: 4. Set the maximum number of patterns to display in
1195 warnings about non-exhaustive ones.
1196 -fmax-simplifier-iterations=⟨n⟩
1198 default: 4. Set the max iterations for the simplifier.
1199 -fmax-worker-args=⟨n⟩
1201 default: 10. If a worker has that many arguments, none will be
1202 unpacked anymore.
1203 -fno-opt-coercion
1205 Turn off the coercion optimiser
1206 -fno-pre-inlining
1208 Turn off pre-inlining
1209 -fno-state-hack
1211 Turn off the "state hack" whereby any lambda with a real-world
1212 state token as argument is considered to be single-entry. Hence
1213 OK to inline things inside it.
1214 -fomit-interface-pragmas
1216 Don't generate interface pragmas. Implied by -O0 only.
1217 -fomit-yields
1219 Omit heap checks when no allocation is being performed.
1220 -foptimal-applicative-do
1222 Use a slower but better algorithm for ApplicativeDo
1223 -fpedantic-bottoms
1225 Make GHC be more precise about its treatment of bottom (but see
1226 also -fno-state-hack). In particular, GHC will not eta-expand
1227 through a case expression.
1228 -fregs-graph
1230 Use the graph colouring register allocator for register alloca‐
1231 tion in the native code generator. Implied by -O2.
1232 -fregs-iterative
1234 Use the iterative coalescing graph colouring register allocator
1235 in the native code generator.
1236 -fsimplifier-phases=⟨n⟩
1238 default: 2. Set the number of phases for the simplifier. Ignored
1239 with -O0.
1240 -fsimpl-tick-factor=⟨n⟩
1242 default: 100. Set the percentage factor for simplifier ticks.
1243 -fspec-constr
1245 Turn on the SpecConstr transformation. Implied by -O2.
1246 -fspec-constr-count=⟨n⟩
1248 default: 3.* Set to ⟨n⟩ the maximum number of specialisations
1249 that will be created for any one function by the SpecConstr
1250 transformation.
1251 -fspec-constr-threshold=⟨n⟩
1253 default: 2000. Set the size threshold for the SpecConstr trans‐
1254 formation to ⟨n⟩.
1255 -fspecialise
1257 Turn on specialisation of overloaded functions. Implied by -O.
1258 -fcross-module-specialise
1260 Turn on specialisation of overloaded functions imported from
1261 other modules.
1262 -fstatic-argument-transformation
1264 Turn on the static argument transformation.
1265 -fstrictness
1267 Turn on strictness analysis. Implied by -O. Implies
1268 -fworker-wrapper
1269 -fstrictness-before=⟨n⟩
1271 Run an additional strictness analysis before simplifier phase
1272 ⟨n⟩
1273 -funbox-small-strict-fields
1275 Flatten strict constructor fields with a pointer-sized represen‐
1276 tation. Implied by -O.
1277 -funbox-strict-fields
1279 Flatten strict constructor fields
1280 -funfolding-creation-threshold=⟨n⟩
1282 default: 750. Tweak unfolding settings.
1283 -funfolding-dict-discount=⟨n⟩
1285 default: 30. Tweak unfolding settings.
1286 -funfolding-fun-discount=⟨n⟩
1288 default: 60. Tweak unfolding settings.
1289 -funfolding-keeness-factor=⟨n⟩
1291 default: 1.5. Tweak unfolding settings.
1292 -funfolding-use-threshold=⟨n⟩
1294 default: 60. Tweak unfolding settings.
1295 -fvectorisation-avoidance
1297 Enable vectorisation avoidance. Always enabled by default.
1298 -fvectorise
1300 Enable vectorisation of nested data parallelism
1301 -fworker-wrapper
1303 Enable the worker-wrapper transformation after a strictness
1304 analysis pass. Implied by -O, and by -fstrictness. Disabled by
1305 -fno-strictness. Enabling -fworker-wrapper while strictness
1306 analysis is disabled (by -fno-strictness) has no effect.
1307 Optimization levels
1309 -O0 Disable optimisations (default)
1310 -O, -O1
1312 Enable level 1 optimisations
1313 -O2 Enable level 2 optimisations
1315 -Odph Enable level 2 optimisations, set -fmax-simplifier-iterations=20
1317 and -fsimplifier-phases=3.
1318 Package options
1320 -this-unit-id ⟨unit-id⟩
1321 Compile to be part of unit (i.e. package) ⟨unit-id⟩
1322 -package ⟨pkg⟩
1324 Expose package ⟨pkg⟩
1325 -hide-all-packages
1327 Hide all packages by default
1328 -hide-package ⟨pkg⟩
1330 Hide package ⟨pkg⟩
1331 -ignore-package ⟨pkg⟩
1333 Ignore package ⟨pkg⟩
1334 -package-db ⟨file⟩
1336 Add ⟨file⟩ to the package db stack.
1337 -clear-package-db
1339 Clear the package db stack.
1340 -no-global-package-db
1342 Remove the global package db from the stack.
1343 -global-package-db
1345 Add the global package db to the stack.
1346 -no-user-package-db
1348 Remove the user's package db from the stack.
1349 -user-package-db
1351 Add the user's package db to the stack.
1352 -no-auto-link-packages
1354 Don't automatically link in the base and rts packages.
1355 -trust ⟨pkg⟩
1357 Expose package ⟨pkg⟩ and set it to be trusted
1358 -distrust ⟨pkg⟩
1360 Expose package ⟨pkg⟩ and set it to be distrusted
1361 -distrust-all
1363 Distrust all packages by default
1364 -package-env ⟨file⟩|⟨name⟩
1366 Use the specified package environment.
1367 Phases of compilation
1369 -F Enable the use of a pre-processor (set with -pgmF ⟨cmd⟩)
1370 -E Stop after preprocessing (.hspp file)
1372 -C Stop after generating C (.hc file)
1374 -S Stop after generating assembly (.s file)
1376 -c Stop after generating object (.o) file
1378 -x ⟨suffix⟩
1380 Override default behaviour for source files
1381 Overriding external programs
1383 -pgmL ⟨cmd⟩
1384 Use ⟨cmd⟩ as the literate pre-processor
1385 -pgmP ⟨cmd⟩
1387 Use ⟨cmd⟩ as the C pre-processor (with -cpp only)
1388 -pgmc ⟨cmd⟩
1390 Use ⟨cmd⟩ as the C compiler
1391 -pgmlo ⟨cmd⟩
1393 Use ⟨cmd⟩ as the LLVM optimiser
1394 -pgmlc ⟨cmd⟩
1396 Use ⟨cmd⟩ as the LLVM compiler
1397 -pgms ⟨cmd⟩
1399 Use ⟨cmd⟩ as the splitter
1400 -pgma ⟨cmd⟩
1402 Use ⟨cmd⟩ as the assembler
1403 -pgml ⟨cmd⟩
1405 Use ⟨cmd⟩ as the linker
1406 -pgmdll ⟨cmd⟩
1408 Use ⟨cmd⟩ as the DLL generator
1409 -pgmF ⟨cmd⟩
1411 Use ⟨cmd⟩ as the pre-processor (with -F only)
1412 -pgmwindres ⟨cmd⟩
1414 Use ⟨cmd⟩ as the program for embedding manifests on Windows.
1415 -pgmlibtool ⟨cmd⟩
1417 Use ⟨cmd⟩ as the command for libtool (with -staticlib only).
1418 Phase-specific options
1420 -optL ⟨option⟩
1421 pass ⟨option⟩ to the literate pre-processor
1422 -optP ⟨option⟩
1424 pass ⟨option⟩ to cpp (with -cpp only)
1425 -optF ⟨option⟩
1427 pass ⟨option⟩ to the custom pre-processor
1428 -optc ⟨option⟩
1430 pass ⟨option⟩ to the C compiler
1431 -optlo ⟨option⟩
1433 pass ⟨option⟩ to the LLVM optimiser
1434 -optlc ⟨option⟩
1436 pass ⟨option⟩ to the LLVM compiler
1437 -opta ⟨option⟩
1439 pass ⟨option⟩ to the assembler
1440 -optl ⟨option⟩
1442 pass ⟨option⟩ to the linker
1443 -optdll ⟨option⟩
1445 pass ⟨option⟩ to the DLL generator
1446 -optwindres ⟨option⟩
1448 pass ⟨option⟩ to windres.
1449 Platform-specific options
1451 -msse2 (x86 only) Use SSE2 for floating-point operations
1452 -msse4.2
1454 (x86 only) Use SSE4.2 for floating-point operations
1455 Compiler plugins
1457 -fplugin=⟨module⟩
1458 Load a plugin exported by a given module
1459 -fplugin-opt=⟨module⟩:⟨args⟩
1461 Give arguments to a plugin module; module must be specified with
1462 -fplugin
1463 Profiling
1465 -prof Turn on profiling
1466 -fprof-auto
1468 Auto-add SCCs to all bindings not marked INLINE
1469 -fprof-auto-top
1471 Auto-add SCCs to all top-level bindings not marked INLINE
1472 -fprof-auto-exported
1474 Auto-add SCCs to all exported bindings not marked INLINE
1475 -fprof-cafs
1477 Auto-add SCCs to all CAFs
1478 -fno-prof-count-entries
1480 Do not collect entry counts
1481 -ticky Turn on ticky-ticky profiling
1483 Program coverage
1485 -fhpc Turn on Haskell program coverage instrumentation
1486 -hpcdir ⟨dir⟩
1488 Directory to deposit .mix files during compilation (default is
1489 .hpc)
1490 Recompilation checking
1492 -fforce-recomp
1493 Turn off recompilation checking. This is implied by any -ddump-X
1494 option when compiling a single file (i.e. when using -c).
1495 Redirecting output
1497 -hcsuf ⟨suffix⟩
1498 set the suffix to use for intermediate C files
1499 -hidir ⟨dir⟩
1501 set directory for interface files
1502 -hisuf ⟨suffix⟩
1504 set the suffix to use for interface files
1505 -o ⟨file⟩
1507 set output filename
1508 -odir ⟨dir⟩
1510 set directory for object files
1511 -ohi ⟨file⟩
1513 set the filename in which to put the interface
1514 -osuf ⟨suffix⟩
1516 set the output file suffix
1517 -stubdir ⟨dir⟩
1519 redirect FFI stub files
1520 -dumpdir ⟨dir⟩
1522 redirect dump files
1523 -outputdir ⟨dir⟩
1525 set output directory
1526 -dyno ⟨file⟩
1528 Set the output filename for dynamic object files (see
1529 -dynamic-too)
1530 -dynosuf ⟨suffix⟩
1532 Set the object suffix for dynamic object files (see
1533 -dynamic-too)
1534 -dynhisuf ⟨suffix⟩
1536 Set the hi suffix for dynamic object files (see -dynamic-too)
1537 Temporary files
1539 -tmpdir ⟨dir⟩
1540 set the directory for temporary files
1541 Verbosity options
1543 -v verbose mode (equivalent to -v3)
1544 -v ⟨n⟩ set verbosity level
1546 -fhide-source-paths
1548 hide module source and object paths
1549 -fprint-potential-instances
1551 display all available instances in type error messages
1552 -fprint-explicit-foralls
1554 Print explicit forall quantification in types. See also -XEx‐
1555 plicitForAll
1556 -fprint-explicit-kinds
1558 Print explicit kind foralls and kind arguments in types. See
1559 also -XKindSignatures
1560 -fprint-explicit-runtime-reps
1562 Print RuntimeRep variables in types which are runtime-represen‐
1563 tation polymorphic.
1564 -fprint-unicode-syntax
1566 Use unicode syntax when printing expressions, types and kinds.
1567 See also -XUnicodeSyntax
1568 -fprint-expanded-synonyms
1570 In type errors, also print type-synonym-expanded types.
1571 -fprint-typechecker-elaboration
1573 Print extra information from typechecker.
1574 -fdiagnostics-color=(always|auto|never)
1576 Use colors in error messages
1577 -f[no-]diagnostics-show-caret
1579 Whether to show snippets of original source code
1580 -ferror-spans
1582 Output full span in error messages
1583 -Rghc-timing
1585 Summarise timing stats for GHC (same as +RTS -tstderr).
1586 -fshow-hole-constraints
1588 Show constraints when reporting typed holes
1589 -fshow-loaded-modules
1591 Show the names of modules that GHCi loaded after a :load com‐
1592 mand.
1593 Warnings
1595 -W enable normal warnings
1596 -w disable all warnings
1598 -Wall enable almost all warnings (details in options-sanity)
1600 -Wcompat
1602 enable future compatibility warnings (details in options-sanity)
1603 -Werror
1605 make warnings fatal
1606 -Werror=⟨wflag⟩
1608 make a specific warning fatal
1609 -Wwarn make warnings non-fatal
1611 -Wwarn=⟨wflag⟩
1613 make a specific warning non-fatal
1614 -Wunrecognised-warning-flags
1616 throw a warning when an unreconised -W... flag is encountered on
1617 the command line.
1618 -fshow-warning-groups
1620 show which group an emitted warning belongs to.
1621 -fdefer-type-errors
1623 Turn type errors into warnings, deferring the error until run‐
1624 time. Implies -fdefer-typed-holes and -fdefer-out-of-scope-vari‐
1625 ables. See also -Wdeferred-type-errors
1626 -fdefer-typed-holes
1628 Convert typed hole errors into warnings, deferring the error
1629 until runtime. Implied by -fdefer-type-errors. See also
1630 -Wtyped-holes.
1631 -fdefer-out-of-scope-variables
1633 Convert variable out of scope variables errors into warnings.
1634 Implied by -fdefer-type-errors. See also -Wde‐
1635 ferred-out-of-scope-variables.
1636 -fhelpful-errors
1638 Make suggestions for mis-spelled names.
1639 -freverse-errors
1641 Display errors in GHC/GHCi sorted by reverse order of source
1642 code line numbers.
1643 -fmax-errors
1645 Limit the number of errors displayed in GHC/GHCi.
1646 -Wdeprecated-flags
1648 warn about uses of commandline flags that are deprecated
1649 -Wduplicate-constraints
1651 warn when a constraint appears duplicated in a type signature
1652 -Wduplicate-exports
1654 warn when an entity is exported multiple times
1655 -Whi-shadowing
1657 warn when a .hi file in the current directory shadows a library
1658 -Widentities
1660 warn about uses of Prelude numeric conversions that are probably
1661 the identity (and hence could be omitted)
1662 -Wimplicit-prelude
1664 warn when the Prelude is implicitly imported
1665 -Wincomplete-patterns
1667 warn when a pattern match could fail
1668 -Wincomplete-uni-patterns
1670 warn when a pattern match in a lambda expression or pattern
1671 binding could fail
1672 -fmax-pmcheck-iterations=⟨n⟩
1674 the iteration limit for the pattern match checker
1675 -Wincomplete-record-updates
1677 warn when a record update could fail
1678 -Wmissing-fields
1680 warn when fields of a record are uninitialised
1681 -Wmissing-import-lists
1683 warn when an import declaration does not explicitly list all
1684 thenames brought into scope
1685 -Wmissing-methods
1687 warn when class methods are undefined
1688 -Wmissing-signatures
1690 warn about top-level functions without signatures
1691 -Wmissing-exported-sigs
1693 (deprecated) warn about top-level functions without signatures,
1694 only if they are exported. takes precedence over -Wmissing-sig‐
1695 natures
1696 -Wmissing-exported-signatures
1698 warn about top-level functions without signatures, only if they
1699 are exported. takes precedence over -Wmissing-signatures
1700 -Wmissing-local-sigs
1702 (deprecated) warn about polymorphic local bindings without sig‐
1703 natures
1704 -Wmissing-local-signatures
1706 warn about polymorphic local bindings without signatures
1707 -Wmissing-monadfail-instances
1709 warn when a failable pattern is used in a do-block that does not
1710 have a MonadFail instance.
1711 -Wsemigroup
1713 warn when a Monoid is not Semigroup, and on non-Semigroup defi‐
1714 nitions of (<>)?
1715 -Wmissed-specialisations
1717 warn when specialisation of an imported, overloaded function
1718 fails.
1719 -Wall-missed-specialisations
1721 warn when specialisation of any overloaded function fails.
1722 -Wmonomorphism-restriction
1724 warn when the Monomorphism Restriction is applied
1725 -Wname-shadowing
1727 warn when names are shadowed
1728 -Wnoncanonical-monad-instances
1730 warn when Applicative or Monad instances have noncanonical defi‐
1731 nitions of return, pure, (>>), or (*>). See flag description in
1732 options-sanity for more details.
1733 -Wnoncanonical-monadfail-instances
1735 warn when Monad or MonadFail instances have noncanonical defini‐
1736 tions of fail.See flag description in options-sanity for more
1737 details.
1738 -Wnoncanonical-monoid-instances
1740 warn when Semigroup or Monoid instances have noncanonical defi‐
1741 nitions of (<>) or mappend. See flag description in options-san‐
1742 ity for more details.
1743 -Worphans
1745 warn when the module contains orphan instance declarations or
1746 rewrite rules
1747 -Woverlapping-patterns
1749 warn about overlapping patterns
1750 -Wtabs warn if there are tabs in the source file
1752 -Wtype-defaults
1754 warn when defaulting happens
1755 -Wunrecognised-pragmas
1757 warn about uses of pragmas that GHC doesn't recognise
1758 -Wunticked-promoted-constructors
1760 warn if promoted constructors are not ticked
1761 -Wunused-binds
1763 warn about bindings that are unused. Alias for
1764 -Wunused-top-binds, -Wunused-local-binds and -Wunused-pat‐
1765 tern-binds
1766 -Wunused-top-binds
1768 warn about top-level bindings that are unused
1769 -Wunused-local-binds
1771 warn about local bindings that are unused
1772 -Wunused-pattern-binds
1774 warn about pattern match bindings that are unused
1775 -Wunused-imports
1777 warn about unnecessary imports
1778 -Wunused-matches
1780 warn about variables in patterns that aren't used
1781 -Wunused-foralls
1783 warn about type variables in user-written foralls that are
1784 unused
1785 -Wunused-type-variables
1787 warn about variables in type family or data family instances
1788 that are unused
1789 -Wunused-do-bind
1791 warn about do bindings that appear to throw away values of types
1792 other than ()
1793 -Wwrong-do-bind
1795 warn about do bindings that appear to throw away monadic values
1796 that you should have bound instead
1797 -Wunsafe
1799 warn if the module being compiled is regarded to be unsafe.
1800 Should be used to check the safety status of modules when using
1801 safe inference. Works on all module types, even those using
1802 explicit Safe Haskell modes (such as -XTrustworthy) and so can
1803 be used to have the compiler check any assumptions made.
1804 -Wsafe warn if the module being compiled is regarded to be safe. Should
1806 be used to check the safety status of modules when using safe
1807 inference. Works on all module types, even those using explicit
1808 Safe Haskell modes (such as -XTrustworthy) and so can be used to
1809 have the compiler check any assumptions made.
1810 -Wtrustworthy-safe
1812 warn if the module being compiled is marked as -XTrustworthy but
1813 it could instead be marked as -XSafe, a more informative bound.
1814 Can be used to detectonce a Safe Haskell bound can be improved
1815 as dependencies are updated.
1816 -Wwarnings-deprecations
1818 warn about uses of functions & types that have warnings or dep‐
1819 recated pragmas
1820 -Wdeprecations
1822 warn about uses of functions & types that have warnings or dep‐
1823 recated pragmas. Alias for -Wwarnings-deprecations
1824 -Wamp (deprecated) warn on definitions conflicting with the Applica‐
1826 tive-Monad Proposal (AMP)
1827 -Wredundant-constraints
1829 Have the compiler warn about redundant constraints in typesigna‐
1830 tures.
1831 -Wdeferred-type-errors
1833 Report warnings when deferred type errors are enabled. This
1834 option is enabled by default. See -fdefer-type-errors.
1835 -Wtyped-holes
1837 Report warnings when typed hole errors are deferred until run‐
1838 time. See -fdefer-typed-holes.
1839 -Wdeferred-out-of-scope-variables
1841 Report warnings when variable out-of-scope errors are deferred
1842 until runtime. See :ghc-flag:-fdefer-out-of-scope-variables`.
1843 -Wpartial-type-signatures
1845 warn about holes in partial type signatures when -XPartialTypeS‐
1846 ignatures is enabled. Not applicable when -XPartialTypesigna‐
1847 tures is not enabled, in which case errors are generated for
1848 such holes. See partial-type-signatures.
1849 -Wderiving-typeable
1851 warn when encountering a request to derive an instance of class
1852 Typeable. As of GHC 7.10, such declarations are unnecessary and
1853 are ignored by the compiler because GHC has a custom solver for
1854 discharging this type of constraint.
1855 -Wmissing-home-modules
1857 warn when encountering a home module imported, but not listed on
1858 the command line. Useful for cabal to ensure GHC won't pick up
1859 modules, not listed neither in exposed-modules, nor in
1860 other-modules.
1861
1863 Copyright 2015. The University Court of the University of Glasgow. All
1864 rights reserved.
1865
1867 The GHC Team
1868
1870 2015, GHC Team
18718.2.2 Oct 17, 2018 GHC(1)