1GHC(1) Glasgow Haskell Compiler GHC(1)
2
6 ghc - the Glasgow Haskell Compiler
7
9 ghc [option|filename]
10 ghci [option|filename]
11
13 This manual page documents briefly the ghc and ghci commands. Note that
14 ghci is not yet available on all architectures. Extensive documentation
15 is available in various other formats including PDF and HTML; see
16 below.
17 Each of GHC's command line options is classified as either static or
19 dynamic. A static flag may only be specified on the command line,
20 whereas a dynamic flag may also be given in an OPTIONS pragma in a
21 source file or set from the GHCi command-line with :set .
22 As a rule of thumb, all the language options are dynamic, as are the
24 warning options and the debugging options.
25 The rest are static, with the notable exceptions of -v, -cpp, -fasm,
27 -fvia-C, -fllvm, and -#include. The OPTIONS sections lists the status
28 of each flag.
29 Common suffixes of file names for Haskell are:
31 .hs Haskell source code; preprocess, compile
33 .lhs literate Haskell source; unlit, preprocess, compile
35 .hi Interface file; contains information about exported symbols
37 .hc intermediate C files
39 .⟨way⟩_o
41 object files for "way" ⟨way⟩; common ways are:
42 dyn dynamically-linked
44 p built with profiling
46 .⟨way⟩_hi
48 interface files for "way" ⟨way⟩; common ways are:
49
51 Code generation
52 -dynamic-too -fasm -fbyte-code -fllvm -fno-code -fobject-code
53 -fPIC -fPIE -fwrite-interface
54 Debugging the compiler
56 -dcmm-lint -dcore-lint -ddump-asm -ddump-asm-expanded
57 -ddump-asm-liveness -ddump-asm-native -ddump-asm-regalloc
58 -ddump-asm-regalloc-stages -ddump-asm-stats -ddump-bcos
59 -ddump-cmm -ddump-cmm-caf -ddump-cmm-cbe -ddump-cmm-cfg
60 -ddump-cmm-cps -ddump-cmm-from-stg -ddump-cmm-info
61 -ddump-cmm-proc -ddump-cmm-procmap -ddump-cmm-raw
62 -ddump-cmm-sink -ddump-cmm-sp -ddump-cmm-split -ddump-cmm-switch
63 -ddump-cmm-verbose -ddump-core-stats -ddump-cse -ddump-deriv
64 -ddump-ds -ddump-ec-trace -ddump-foreign -ddump-if-trace
65 -ddump-inlinings -ddump-json -ddump-llvm -ddump-occur-anal
66 -ddump-opt-cmm -ddump-parsed -ddump-parsed-ast -ddump-prep
67 -ddump-rn -ddump-rn-ast -ddump-rn-stats -ddump-rn-trace
68 -ddump-rule-firings -ddump-rule-rewrites -ddump-rules
69 -ddump-simpl -ddump-simpl-iterations -ddump-simpl-stats
70 -ddump-spec -ddump-splices -ddump-stg -ddump-str-signatures
71 -ddump-stranal -ddump-tc -ddump-tc-ast -ddump-tc-trace
72 -ddump-timings -ddump-to-file -ddump-types -ddump-vect
73 -ddump-vt-trace -ddump-worker-wrapper -dfaststring-stats -dini‐
74 tial-unique=⟨s⟩ -dno-debug-output -dppr-case-as-let
75 -dppr-cols=⟨n⟩ -dppr-debug -dppr-user-length -dshow-passes
76 -dstg-lint -dsuppress-all -dsuppress-coercions -dsuppress-idinfo
77 -dsuppress-module-prefixes -dsuppress-stg-free-vars -dsup‐
78 press-ticks -dsuppress-type-applications -dsuppress-type-signa‐
79 tures -dsuppress-unfoldings -dsuppress-uniques -dsup‐
80 press-var-kinds -dth-dec-file=⟨file⟩ -dunique-increment=⟨i⟩
81 -dverbose-core2core -dverbose-stg2stg -falignment-sanitisation
82 -fcatch-bottoms -fllvm-fill-undef-with-garbage -g -g⟨n⟩
83 C pre-processor
85 -cpp -D⟨symbol⟩[=⟨value⟩] -I⟨dir⟩ -U⟨symbol⟩
86 Finding imports
88 -i -i⟨dir⟩[:⟨dir⟩]*
89 Interactive mode
91 -fbreak-on-error -fbreak-on-exception -fghci-hist-size=⟨n⟩ -flo‐
92 cal-ghci-history -fprint-bind-result -fshow-loaded-modules
93 -ghci-script -ignore-dot-ghci -interactive-print ⟨expr⟩
94 Interface files
96 --show-iface ⟨file⟩ -ddump-hi -ddump-hi-diffs -ddump-mini‐
97 mal-imports
98 Keeping intermediate files
100 -keep-hc-file -keep-hc-files -keep-hi-files -keep-llvm-file
101 -keep-llvm-files -keep-o-files -keep-s-file -keep-s-files
102 -keep-tmp-files
103 Language options
105 -XAllowAmbiguousTypes -XApplicativeDo -XArrows -XBangPatterns
106 -XBinaryLiterals -XCApiFFI -XConstrainedClassMethods -XCon‐
107 straintKinds -XCPP -XDataKinds -XDatatypeContexts -XDefaultSig‐
108 natures -XDeriveAnyClass -XDeriveDataTypeable -XDeriveFoldable
109 -XDeriveFunctor -XDeriveGeneric -XDeriveLift -XDeriveTraversable
110 -XDerivingStrategies -XDisambiguateRecordFields -XDuplicateRe‐
111 cordFields -XEmptyCase -XEmptyDataDecls -XEmptyDataDeriving
112 -XExistentialQuantification -XExplicitForAll -XExplicitNames‐
113 paces -XExtendedDefaultRules -XFlexibleContexts -XFlexibleIn‐
114 stances -XForeignFunctionInterface -XFunctionalDependencies
115 -XGADTs -XGADTSyntax -XGeneralisedNewtypeDeriving -XGeneralized‐
116 NewtypeDeriving -XHexFloatLiterals -XImplicitParams -XImpredica‐
117 tiveTypes -XIncoherentInstances -XInstanceSigs -XInterrupt‐
118 ibleFFI -XKindSignatures -XLambdaCase -XLiberalTypeSynonyms
119 -XMagicHash -XMonadComprehensions -XMonadFailDesugaring
120 -XMonoLocalBinds -XMultiParamTypeClasses -XMultiWayIf -XNamed‐
121 FieldPuns -XNamedWildCards -XNegativeLiterals -XNoImplicitPre‐
122 lude -XNoMonomorphismRestriction -XNoPatternGuards -XNoTradi‐
123 tionalRecordSyntax -XNPlusKPatterns -XNullaryTypeClasses
124 -XNumDecimals -XOverlappingInstances -XOverloadedLabels -XOver‐
125 loadedLists -XOverloadedStrings -XPackageImports -XParallelList‐
126 Comp -XPartialTypeSignatures -XPatternSynonyms -XPolyKinds
127 -XPostfixOperators -XQuasiQuotes -XRank2Types -XRankNTypes -XRe‐
128 bindableSyntax -XRecordWildCards -XRecursiveDo -XRoleAnnotations
129 -XSafe -XScopedTypeVariables -XStandaloneDeriving -XStaticPoint‐
130 ers -XStrict -XStrictData -XTemplateHaskell -XTemplateHaskel‐
131 lQuotes -XTransformListComp -XTrustworthy -XTupleSections -XTy‐
132 peApplications -XTypeFamilies -XTypeFamilyDependencies -XTypeIn‐
133 Type -XTypeOperators -XTypeSynonymInstances -XUnboxedSums -XUn‐
134 boxedTuples -XUndecidableInstances -XUndecidableSuperClasses
135 -XUnicodeSyntax -XUnsafe -XViewPatterns
136 Linking options
138 -c -debug -dylib-install-name ⟨path⟩ -dynamic -dynload -eventlog
139 -fno-embed-manifest -fno-gen-manifest -fno-shared-implib -frame‐
140 work ⟨name⟩ -framework-path ⟨dir⟩ -fwhole-archive-hs-libs -L
141 ⟨dir⟩ -l ⟨lib⟩ -main-is ⟨thing⟩ -no-hs-main -no-rtsopts-sugges‐
142 tions -package ⟨name⟩ -pie -rdynamic -rtsopts[=⟨none|some|all⟩]
143 -shared -split-objs -split-sections -static -staticlib -threaded
144 -with-rtsopts=⟨opts⟩
145 Miscellaneous options
147 -fexternal-interpreter -fglasgow-exts -ghcversion-file ⟨path to
148 ghcversion.h⟩ -H ⟨size⟩ -j[⟨n⟩]
149 Modes of operation
151 --frontend ⟨module⟩ --help -? --info --interactive --make
152 --mk-dll --numeric-version --print-libdir --show-iface ⟨file⟩
153 --show-options --supported-extensions --supported-languages
154 --version -V -e ⟨expr⟩ -M
155 Individual optimizations
157 -fcall-arity -fcase-folding -fcase-merge -fcmm-elim-com‐
158 mon-blocks -fcmm-sink -fcpr-anal -fcross-module-specialise -fcse
159 -fdicts-cheap -fdicts-strict -fdmd-tx-dict-sel -fdo-eta-reduc‐
160 tion -fdo-lambda-eta-expansion -feager-blackholing -fenable-re‐
161 write-rules -fexcess-precision -fexitification -fex‐
162 pose-all-unfoldings -ffloat-in -ffull-laziness -ffun-to-thunk
163 -fignore-asserts -fignore-interface-pragmas -flate-dmd-anal
164 -fliberate-case -fliberate-case-threshold=⟨n⟩ -fllvm-pass-vec‐
165 tors-in-regs -floopification -fmax-inline-alloc-size=⟨n⟩
166 -fmax-inline-memcpy-insns=⟨n⟩ -fmax-inline-memset-insns=⟨n⟩
167 -fmax-relevant-binds=⟨n⟩ -fmax-simplifier-iterations=⟨n⟩
168 -fmax-uncovered-patterns=⟨n⟩ -fmax-valid-substitutions=⟨n⟩
169 -fmax-worker-args=⟨n⟩ -fno-opt-coercion -fno-pre-inlining
170 -fno-state-hack -fomit-interface-pragmas -fomit-yields -fopti‐
171 mal-applicative-do -fpedantic-bottoms -fregs-graph -fregs-itera‐
172 tive -fsimpl-tick-factor=⟨n⟩ -fsimplifier-phases=⟨n⟩
173 -fsolve-constant-dicts -fspec-constr -fspec-constr-count=⟨n⟩
174 -fspec-constr-keen -fspec-constr-threshold=⟨n⟩ -fspecialise
175 -fspecialise-aggressively -fstatic-argument-transformation
176 -fstg-cse -fstrictness -fstrictness-before=⟨n⟩ -fun‐
177 box-small-strict-fields -funbox-strict-fields -funfolding-cre‐
178 ation-threshold=⟨n⟩ -funfolding-dict-discount=⟨n⟩ -funfold‐
179 ing-fun-discount=⟨n⟩ -funfolding-keeness-factor=⟨n⟩ -funfold‐
180 ing-use-threshold=⟨n⟩ -fvectorisation-avoidance -fvectorise
181 Optimization levels
183 -O -O1 -O0 -O2 -Odph
184 Package options
186 -clear-package-db -distrust ⟨pkg⟩ -distrust-all-packages -fpack‐
187 age-trust -global-package-db -hide-all-packages -hide-package
188 ⟨pkg⟩ -ignore-package ⟨pkg⟩ -no-auto-link-packages
189 -no-global-package-db -no-user-package-db -package ⟨pkg⟩ -pack‐
190 age-db ⟨file⟩ -package-env ⟨file⟩|⟨name⟩ -package-id ⟨unit-id⟩
191 -this-unit-id ⟨unit-id⟩ -trust ⟨pkg⟩ -user-package-db
192 Phases of compilation
194 -C -c -E -F -S -x ⟨suffix⟩
195 Overriding external programs
197 -pgma ⟨cmd⟩ -pgmc ⟨cmd⟩ -pgmdll ⟨cmd⟩ -pgmF ⟨cmd⟩ -pgmi ⟨cmd⟩
198 -pgmL ⟨cmd⟩ -pgml ⟨cmd⟩ -pgmlc ⟨cmd⟩ -pgmlibtool ⟨cmd⟩ -pgmlo
199 ⟨cmd⟩ -pgmP ⟨cmd⟩ -pgms ⟨cmd⟩ -pgmwindres ⟨cmd⟩
200 Phase-specific options
202 -opta ⟨option⟩ -optc ⟨option⟩ -optdll ⟨option⟩ -optF ⟨option⟩
203 -opti ⟨option⟩ -optL ⟨option⟩ -optl ⟨option⟩ -optlc ⟨option⟩
204 -optlo ⟨option⟩ -optP ⟨option⟩ -optwindres ⟨option⟩
205 Platform-specific options
207 -msse2 -msse4.2
208 Compiler plugins
210 -fplugin-opt=⟨module⟩:⟨args⟩ -fplugin=⟨module⟩ -hide-all-plug‐
211 in-packages -plugin-package ⟨pkg⟩ -plugin-package-id ⟨pkg-id⟩
212 Profiling
214 -fno-prof-auto -fno-prof-cafs -fno-prof-count-entries
215 -fprof-auto -fprof-auto-calls -fprof-auto-exported
216 -fprof-auto-top -fprof-cafs -prof -ticky
217 Program coverage
219 -fhpc
220 Recompilation checking
222 -fforce-recomp -fignore-hpc-changes -fignore-optim-changes
223 Redirecting output
225 --exclude-module=⟨file⟩ -ddump-mod-cycles -dep-makefile ⟨file⟩
226 -dep-suffix ⟨suffix⟩ -dumpdir ⟨dir⟩ -hcsuf ⟨suffix⟩ -hidir ⟨dir⟩
227 -hisuf ⟨suffix⟩ -include-pkg-deps -o ⟨file⟩ -odir ⟨dir⟩ -ohi
228 ⟨file⟩ -osuf ⟨suffix⟩ -outputdir ⟨dir⟩ -stubdir ⟨dir⟩
229 Temporary files
231 -tmpdir ⟨dir⟩
232 Verbosity options
234 -fdiagnostics-color=⟨always|auto|never⟩ -fdiagnostics-show-caret
235 -ferror-spans -fhide-source-paths -fprint-equality-relations
236 -fprint-expanded-synonyms -fprint-explicit-coercions
237 -fprint-explicit-foralls -fprint-explicit-kinds
238 -fprint-explicit-runtime-rep -fprint-explicit-runtime-reps
239 -fprint-potential-instances -fprint-typechecker-elaboration
240 -fprint-unicode-syntax -fshow-hole-constraints -Rghc-timing -v
241 -v⟨n⟩
242 Warnings
244 -fdefer-out-of-scope-variables -fdefer-type-errors -fde‐
245 fer-typed-holes -fhelpful-errors -fmax-pmcheck-iterations=⟨n⟩
246 -fshow-warning-groups -W -w -Wall -Wall-missed-specialisations
247 -Wamp -Wcompat -Wcpp-undef -Wdeferred-out-of-scope-variables
248 -Wdeferred-type-errors -Wdeprecated-flags -Wdeprecations
249 -Wdodgy-exports -Wdodgy-foreign-imports -Wdodgy-imports -Wdupli‐
250 cate-constraints -Wduplicate-exports -Wempty-enumerations -Wer‐
251 ror -Weverything -Whi-shadowing -Widentities -Wimplicit-prelude
252 -Wincomplete-patterns -Wincomplete-record-updates -Wincom‐
253 plete-uni-patterns -Winline-rule-shadowing -Wmissed-specialisa‐
254 tions -Wmissing-export-lists -Wmissing-exported-signatures
255 -Wmissing-exported-sigs -Wmissing-fields -Wmissing-home-modules
256 -Wmissing-import-lists -Wmissing-local-signatures -Wmiss‐
257 ing-local-sigs -Wmissing-methods -Wmissing-monadfail-instances
258 -Wmissing-pattern-synonym-signatures -Wmissing-signatures
259 -Wmonomorphism-restriction -Wname-shadowing -Wno-compat -Wnon‐
260 canonical-monad-instances -Wnoncanonical-monadfail-instances
261 -Wnoncanonical-monoid-instances -Worphans -Woverflowed-literals
262 -Woverlapping-patterns -Wpartial-fields -Wpartial-type-signa‐
263 tures -Wredundant-constraints -Wsafe -Wsemigroup -Wsimplifi‐
264 able-class-constraints -Wtabs -Wtrustworthy-safe -Wtype-defaults
265 -Wtyped-holes -Wunbanged-strict-patterns -Wunrecognised-pragmas
266 -Wunrecognised-warning-flags -Wunsafe -Wunsupported-calling-con‐
267 ventions -Wunsupported-llvm-version -Wunticked-promoted-con‐
268 structors -Wunused-binds -Wunused-do-bind -Wunused-foralls
269 -Wunused-imports -Wunused-local-binds -Wunused-matches
270 -Wunused-pattern-binds -Wunused-top-binds -Wunused-type-patterns
271 -Wwarn -Wwarnings-deprecations -Wwrong-do-bind
272 Code generation
274 -dynamic-too
275 Build dynamic object files as well as static object files during
276 compilation
277 -fasm Use the native code generator
279 -fbyte-code
281 Generate byte-code
282 -fllvm Compile using the LLVM code generator
284 -fno-code
286 Omit code generation
287 -fobject-code
289 Generate object code
290 -fPIC Generate position-independent code (where available)
292 -fPIE Generate code for a position-independent executable (where
294 available)
295 -fwrite-interface
297 Always write interface files
298 Debugging the compiler
300 -dcmm-lint
301 C-- pass sanity checking
302 -dcore-lint
304 Turn on internal sanity checking
305 -ddump-asm
307 Dump final assembly
308 -ddump-asm-expanded
310 Dump the result of the synthetic instruction expansion pass.
311 -ddump-asm-liveness
313 Dump assembly augmented with register liveness
314 -ddump-asm-native
316 Dump initial assembly
317 -ddump-asm-regalloc
319 Dump the result of register allocation
320 -ddump-asm-regalloc-stages
322 Dump the build/spill stages of the -fregs-graph register alloca‐
323 tor.
324 -ddump-asm-stats
326 Dump statistics from the register allocator.
327 -ddump-bcos
329 Dump interpreter byte code
330 -ddump-cmm
332 Dump the final C-- output
333 -ddump-cmm-caf
335 Dump the results of the C-- CAF analysis pass.
336 -ddump-cmm-cbe
338 Dump the results of common block elimination
339 -ddump-cmm-cfg
341 Dump the results of the C-- control flow optimisation pass.
342 -ddump-cmm-cps
344 Dump the results of the CPS pass
345 -ddump-cmm-from-stg
347 Dump STG-to-C-- output
348 -ddump-cmm-info
350 Dump the results of the C-- info table augmentation pass.
351 -ddump-cmm-proc
353 Dump the results of proc-point analysis
354 -ddump-cmm-procmap
356 Dump the results of the C-- proc-point map pass.
357 -ddump-cmm-raw
359 Dump raw C--
360 -ddump-cmm-sink
362 Dump the results of the C-- sinking pass.
363 -ddump-cmm-sp
365 Dump the results of the C-- stack layout pass.
366 -ddump-cmm-split
368 Dump the results of the C-- proc-point splitting pass.
369 -ddump-cmm-switch
371 Dump the results of switch lowering passes
372 -ddump-cmm-verbose
374 Show output from each C-- pipeline pass
375 -ddump-core-stats
377 Print a one-line summary of the size of the Core program at the
378 end of the optimisation pipeline
379 -ddump-cse
381 Dump CSE output
382 -ddump-deriv
384 Dump deriving output
385 -ddump-ds
387 Dump desugarer output
388 -ddump-ec-trace
390 Trace exhaustiveness checker
391 -ddump-foreign
393 Dump foreign export stubs
394 -ddump-if-trace
396 Trace interface files
397 -ddump-inlinings
399 Dump inlining info
400 -ddump-json
402 Dump error messages as JSON documents
403 -ddump-llvm
405 Dump LLVM intermediate code.
406 -ddump-occur-anal
408 Dump occurrence analysis output
409 -ddump-opt-cmm
411 Dump the results of C-- to C-- optimising passes
412 -ddump-parsed
414 Dump parse tree
415 -ddump-parsed-ast
417 Dump parser output as a syntax tree
418 -ddump-prep
420 Dump prepared core
421 -ddump-rn
423 Dump renamer output
424 -ddump-rn-ast
426 Dump renamer output as a syntax tree
427 -ddump-rn-stats
429 Renamer stats
430 -ddump-rn-trace
432 Trace renamer
433 -ddump-rule-firings
435 Dump rule firing info
436 -ddump-rule-rewrites
438 Dump detailed rule firing info
439 -ddump-rules
441 Dump rewrite rules
442 -ddump-simpl
444 Dump final simplifier output
445 -ddump-simpl-iterations
447 Dump output from each simplifier iteration
448 -ddump-simpl-stats
450 Dump simplifier stats
451 -ddump-spec
453 Dump specialiser output
454 -ddump-splices
456 Dump TH spliced expressions, and what they evaluate to
457 -ddump-stg
459 Dump final STG
460 -ddump-str-signatures
462 Dump strictness signatures
463 -ddump-stranal
465 Dump strictness analyser output
466 -ddump-tc
468 Dump typechecker output
469 -ddump-tc-ast
471 Dump typechecker output as a syntax tree
472 -ddump-tc-trace
474 Trace typechecker
475 -ddump-timings
477 Dump per-pass timing and allocation statistics
478 -ddump-to-file
480 Dump to files instead of stdout
481 -ddump-types
483 Dump type signatures
484 -ddump-vect
486 Dump vectoriser input and output
487 -ddump-vt-trace
489 Trace vectoriser
490 -ddump-worker-wrapper
492 Dump worker-wrapper output
493 -dfaststring-stats
495 Show statistics for fast string usage when finished
496 -dinitial-unique=⟨s⟩
498 Start UniqSupply allocation from ⟨s⟩.
499 -dno-debug-output
501 Suppress unsolicited debugging output
502 -dppr-case-as-let
504 Print single alternative case expressions as strict lets.
505 -dppr-cols=⟨n⟩
507 Set the width of debugging output. For example -dppr-cols200
508 -dppr-debug
510 Turn on debug printing (more verbose)
511 -dppr-user-length
513 Set the depth for printing expressions in error msgs
514 -dshow-passes
516 Print out each pass name as it happens
517 -dstg-lint
519 STG pass sanity checking
520 -dsuppress-all
522 In core dumps, suppress everything (except for uniques) that is
523 suppressible.
524 -dsuppress-coercions
526 Suppress the printing of coercions in Core dumps to make them
527 shorter
528 -dsuppress-idinfo
530 Suppress extended information about identifiers where they are
531 bound
532 -dsuppress-module-prefixes
534 Suppress the printing of module qualification prefixes
535 -dsuppress-stg-free-vars
537 Suppress the printing of closure free variable lists in STG out‐
538 put
539 -dsuppress-ticks
541 Suppress "ticks" in the pretty-printer output.
542 -dsuppress-type-applications
544 Suppress type applications
545 -dsuppress-type-signatures
547 Suppress type signatures
548 -dsuppress-unfoldings
550 Suppress the printing of the stable unfolding of a variable at
551 its binding site
552 -dsuppress-uniques
554 Suppress the printing of uniques in debug output (easier to use
555 diff)
556 -dsuppress-var-kinds
558 Suppress the printing of variable kinds
559 -dth-dec-file=⟨file⟩
561 Show evaluated TH declarations in a .th.hs file
562 -dunique-increment=⟨i⟩
564 Set the increment for the generated Unique's to ⟨i⟩.
565 -dverbose-core2core
567 Show output from each core-to-core pass
568 -dverbose-stg2stg
570 Show output from each STG-to-STG pass
571 -falignment-sanitisation
573 Compile with alignment checks for all info table dereferences.
574 -fcatch-bottoms
576 Insert error expressions after bottoming expressions; useful
577 when debugging the compiler.
578 -fllvm-fill-undef-with-garbage
580 Intruct LLVM to fill dead STG registers with garbage
581 -g Produce DWARF debug information in compiled object files. ⟨n⟩
583 can be 0, 1, or 2, with higher numbers producing richer output.
584 If ⟨n⟩ is omitted level 2 is assumed.
585 C pre-processor
587 -cpp Run the C pre-processor on Haskell source files
588 -D⟨symbol⟩[=⟨value⟩]
590 Define a symbol in the C pre-processor
591 -I⟨dir⟩
593 Add ⟨dir⟩ to the directory search list for #include files
594 -U⟨symbol⟩
596 Undefine a symbol in the C pre-processor
597 Finding imports
599 -i Empty the import directory list
600 -i⟨dir⟩[:⟨dir⟩]*
602 add ⟨dir⟩, ⟨dir2⟩, etc. to import path
603 Interactive mode
605 -fbreak-on-error
606 Break on uncaught exceptions and errors
607 -fbreak-on-exception
609 Break on any exception thrown
610 -fghci-hist-size=⟨n⟩
612 Set the number of entries GHCi keeps for :history. See
613 ghci-debugger.
614 -flocal-ghci-history
616 Use current directory for the GHCi command history file
617 .ghci-history.
618 -fprint-bind-result
620 Turn on printing of binding results in GHCi
621 -fshow-loaded-modules
623 Show the names of modules that GHCi loaded after a :load com‐
624 mand.
625 -ghci-script
627 Read additional .ghci files
628 -ignore-dot-ghci
630 Disable reading of .ghci files
631 -interactive-print ⟨expr⟩
633 Select the function to use for printing evaluated expressions in
634 GHCi
635 Interface files
637 --show-iface ⟨file⟩
638 See modes.
639 -ddump-hi
641 Dump the new interface to stdout
642 -ddump-hi-diffs
644 Show the differences vs. the old interface
645 -ddump-minimal-imports
647 Dump a minimal set of imports
648 Keeping intermediate files
650 -keep-hc-file
651 Retain intermediate .hc files.
652 -keep-hi-files
654 Retain intermediate .hi files (the default).
655 -keep-llvm-file
657 Retain intermediate LLVM .ll files. Implies -fllvm.
658 -keep-o-files
660 Retain intermediate .o files (the default).
661 -keep-s-file
663 Retain intermediate .s files.
664 -keep-tmp-files
666 Retain all intermediate temporary files.
667 Language options
669 -XAllowAmbiguousTypes
670 Allow the user to write ambiguous types, and the type inference
671 engine to infer them.
672 -XApplicativeDo
674 Enable Applicative do-notation desugaring
675 -XArrows
677 Enable arrow notation extension
678 -XBangPatterns
680 Enable bang patterns.
681 -XBinaryLiterals
683 Enable support for binary literals.
684 -XCApiFFI
686 Enable the CAPI calling convention.
687 -XConstrainedClassMethods
689 Enable constrained class methods.
690 -XConstraintKinds
692 Enable a kind of constraints.
693 -XCPP Enable the C preprocessor.
695 -XDataKinds
697 Enable datatype promotion.
698 -XDatatypeContexts
700 Allow contexts on data types.
701 -XDefaultSignatures
703 Enable default signatures.
704 -XDeriveAnyClass
706 Enable deriving for any class.
707 -XDeriveDataTypeable
709 Enable deriving for the Data class. Implied by AutoDeriveTy‐
710 peable.
711 -XDeriveFoldable
713 Enable deriving for the Foldable class. Implied by Derive‐
714 Traversable.
715 -XDeriveFunctor
717 Enable deriving for the Functor class. Implied by Derive‐
718 Traversable.
719 -XDeriveGeneric
721 Enable deriving for the Generic class.
722 -XDeriveLift
724 Enable deriving for the Lift class
725 -XDeriveTraversable
727 Enable deriving for the Traversable class. Implies DeriveFunc‐
728 tor and DeriveFoldable.
729 -XDerivingStrategies
731 Enables deriving strategies.
732 -XDisambiguateRecordFields
734 Enable record field disambiguation. Implied by RecordWildCards.
735 -XDuplicateRecordFields
737 Allow definition of record types with identically-named fields.
738 -XEmptyCase
740 Allow empty case alternatives.
741 -XEmptyDataDecls
743 Allow definition of empty data types.
744 -XEmptyDataDeriving
746 Allow deriving instances of standard type classes for empty data
747 types.
748 -XExistentialQuantification
750 Enable liberalised type synonyms.
751 -XExplicitForAll
753 Enable explicit universal quantification. Implied by Scoped‐
754 TypeVariables, LiberalTypeSynonyms, RankNTypes and Existen‐
755 tialQuantification.
756 -XExplicitNamespaces
758 Enable using the keyword type to specify the namespace of
759 entries in imports and exports (explicit-namespaces). Implied
760 by TypeOperators and TypeFamilies.
761 -XExtendedDefaultRules
763 Use GHCi's extended default rules in a normal module.
764 -XFlexibleContexts
766 Enable flexible contexts. Implied by ImplicitParams.
767 -XFlexibleInstances
769 Enable flexible instances. Implies TypeSynonymInstances.
770 Implied by ImplicitParams.
771 -XForeignFunctionInterface
773 Enable foreign function interface.
774 -XFunctionalDependencies
776 Enable functional dependencies. Implies MultiParamTypeClasses.
777 -XGADTs
779 Enable generalised algebraic data types. Implies GADTSyntax and
780 MonoLocalBinds.
781 -XGADTSyntax
783 Enable generalised algebraic data type syntax.
784 -XGeneralisedNewtypeDeriving
786 Enable newtype deriving.
787 -XGeneralizedNewtypeDeriving
789 Enable newtype deriving.
790 -XHexFloatLiterals
792 Enable support for hexadecimal floating point literals.
793 -XImplicitParams
795 Enable Implicit Parameters. Implies FlexibleContexts and Flexi‐
796 bleInstances.
797 -XImpredicativeTypes
799 Enable impredicative types. Implies RankNTypes.
800 -XIncoherentInstances
802 Enable incoherent instances. Implies OverlappingInstances.
803 -XInstanceSigs
805 Enable instance signatures.
806 -XInterruptibleFFI
808 Enable interruptible FFI.
809 -XKindSignatures
811 Enable kind signatures. Implied by TypeFamilies and PolyKinds.
812 -XLambdaCase
814 Enable lambda-case expressions.
815 -XLiberalTypeSynonyms
817 Enable liberalised type synonyms.
818 -XMagicHash
820 Allow # as a postfix modifier on identifiers.
821 -XMonadComprehensions
823 Enable monad comprehensions.
824 -XMonadFailDesugaring
826 Enable monadfail desugaring.
827 -XMonoLocalBinds
829 Enable do not generalise local bindings. Implied by TypeFami‐
830 lies and GADTs.
831 -XMultiParamTypeClasses
833 Enable multi parameter type classes. Implied by FunctionalDe‐
834 pendencies.
835 -XMultiWayIf
837 Enable multi-way if-expressions.
838 -XNamedFieldPuns
840 Enable record puns.
841 -XNamedWildCards
843 Enable named wildcards.
844 -XNegativeLiterals
846 Enable support for negative literals.
847 -XNoImplicitPrelude
849 Don't implicitly import Prelude. Implied by RebindableSyntax.
850 -XNoMonomorphismRestriction
852 Disable the monomorphism restriction.
853 -XNoPatternGuards
855 Disable pattern guards. Implied by Haskell98.
856 -XNoTraditionalRecordSyntax
858 Disable support for traditional record syntax (as supported by
859 Haskell 98) C {f = x}
860 -XNPlusKPatterns
862 Enable support for n+k patterns. Implied by Haskell98.
863 -XNullaryTypeClasses
865 Deprecated, does nothing. nullary (no parameter) type classes
866 are now enabled using MultiParamTypeClasses.
867 -XNumDecimals
869 Enable support for 'fractional' integer literals.
870 -XOverlappingInstances
872 Enable overlapping instances.
873 -XOverloadedLabels
875 Enable overloaded labels.
876 -XOverloadedLists
878 Enable overloaded lists.
879 -XOverloadedStrings
881 Enable overloaded string literals.
882 -XPackageImports
884 Enable package-qualified imports.
885 -XParallelListComp
887 Enable parallel list comprehensions. Implied by ParallelArrays.
888 -XPartialTypeSignatures
890 Enable partial type signatures.
891 -XPatternSynonyms
893 Enable pattern synonyms.
894 -XPolyKinds
896 Enable kind polymorphism. Implies KindSignatures.
897 -XPostfixOperators
899 Enable postfix operators.
900 -XQuasiQuotes
902 Enable quasiquotation.
903 -XRank2Types
905 Enable rank-2 types. Synonym for RankNTypes.
906 -XRankNTypes
908 Enable rank-N types. Implied by ImpredicativeTypes.
909 -XRebindableSyntax
911 Employ rebindable syntax. Implies NoImplicitPrelude.
912 -XRecordWildCards
914 Enable record wildcards. Implies DisambiguateRecordFields.
915 -XRecursiveDo
917 Enable recursive do (mdo) notation.
918 -XRoleAnnotations
920 Enable role annotations.
921 -XSafe Enable the Safe Haskell Safe mode.
923 -XScopedTypeVariables
925 Enable lexically-scoped type variables.
926 -XStandaloneDeriving
928 Enable standalone deriving.
929 -XStaticPointers
931 Enable static pointers.
932 -XStrict
934 Make bindings in the current module strict by default.
935 -XStrictData
937 Enable default strict datatype fields.
938 -XTemplateHaskell
940 Enable Template Haskell.
941 -XTemplateHaskellQuotes
943 Enable quotation subset of Template Haskell.
944 -XTransformListComp
946 Enable generalised list comprehensions.
947 -XTrustworthy
949 Enable the Safe Haskell Trustworthy mode.
950 -XTupleSections
952 Enable tuple sections.
953 -XTypeApplications
955 Enable type application syntax.
956 -XTypeFamilies
958 Enable type families. Implies ExplicitNamespaces, KindSigna‐
959 tures, and MonoLocalBinds.
960 -XTypeFamilyDependencies
962 Enable injective type families. Implies TypeFamilies.
963 -XTypeInType
965 Allow kinds to be used as types, including explicit kind vari‐
966 able quantification, higher-rank kinds, kind synonyms, and kind
967 families. Implies DataKinds, KindSignatures, and PolyKinds.
968 -XTypeOperators
970 Enable type operators. Implies ExplicitNamespaces.
971 -XTypeSynonymInstances
973 Enable type synonyms in instance heads. Implied by FlexibleIn‐
974 stances.
975 -XUnboxedSums
977 Enable unboxed sums.
978 -XUnboxedTuples
980 Enable the use of unboxed tuple syntax.
981 -XUndecidableInstances
983 Enable undecidable instances.
984 -XUndecidableSuperClasses
986 Allow all superclass constraints, including those that may
987 result in non-termination of the typechecker.
988 -XUnicodeSyntax
990 Enable unicode syntax.
991 -XUnsafe
993 Enable Safe Haskell Unsafe mode.
994 -XViewPatterns
996 Enable view patterns.
997 Linking options
999 -c Stop after generating object (.o) file
1000 -debug Use the debugging runtime
1002 -dylib-install-name ⟨path⟩
1004 Set the install name (via -install_name passed to Apple's
1005 linker), specifying the full install path of the library file.
1006 Any libraries or executables that link with it later will pick
1007 up that path as their runtime search location for it. (Dar‐
1008 win/OS X only)
1009 -dynamic
1011 Build dynamically-linked object files and executables
1012 -dynload
1014 Selects one of a number of modes for finding shared libraries at
1015 runtime.
1016 -eventlog
1018 Enable runtime event tracing
1019 -fno-embed-manifest
1021 Do not embed the manifest in the executable (Windows only)
1022 -fno-gen-manifest
1024 Do not generate a manifest file (Windows only)
1025 -fno-shared-implib
1027 Don't generate an import library for a DLL (Windows only)
1028 -framework ⟨name⟩
1030 On Darwin/OS X/iOS only, link in the framework ⟨name⟩. This
1031 option corresponds to the -framework option for Apple's Linker.
1032 -framework-path ⟨dir⟩
1034 On Darwin/OS X/iOS only, add ⟨dir⟩ to the list of directories
1035 searched for frameworks. This option corresponds to the -F
1036 option for Apple's Linker.
1037 -fwhole-archive-hs-libs
1039 When linking a binary executable, this inserts the flag
1040 -Wl,--whole-archive before any -l flags for Haskell libraries,
1041 and -Wl,--no-whole-archive afterwards
1042 -L ⟨dir⟩
1044 Add ⟨dir⟩ to the list of directories searched for libraries
1045 -l ⟨lib⟩
1047 Link in library ⟨lib⟩
1048 -main-is ⟨thing⟩
1050 Set main module and function
1051 -no-hs-main
1053 Don't assume this program contains main
1054 -no-rtsopts-suggestions
1056 Don't print RTS suggestions about linking with
1057 -rtsopts[=⟨none|some|all⟩].
1058 -package ⟨name⟩
1060 Expose package ⟨pkg⟩
1061 -pie Instruct the linker to produce a position-independent exe‐
1063 cutable.
1064 -rdynamic
1066 This instructs the linker to add all symbols, not only used
1067 ones, to the dynamic symbol table. Currently Linux and Win‐
1068 dows/MinGW32 only. This is equivalent to using -optl -rdynamic
1069 on Linux, and -optl -export-all-symbols on Windows.
1070 -rtsopts[=⟨none|some|all⟩]
1072 Control whether the RTS behaviour can be tweaked via com‐
1073 mand-line flags and the GHCRTS environment variable. Using none
1074 means no RTS flags can be given; some means only a minimum of
1075 safe options can be given (the default), and all (or no argument
1076 at all) means that all RTS flags are permitted.
1077 -shared
1079 Generate a shared library (as opposed to an executable)
1080 -split-objs
1082 Split objects (for libraries)
1083 -split-sections
1085 Split sections for link-time dead-code stripping
1086 -static
1088 Use static Haskell libraries
1089 -staticlib
1091 Generate a standalone static library (as opposed to an exe‐
1092 cutable). This is useful when cross compiling. The library
1093 together with all its dependencies ends up in in a single static
1094 library that can be linked against.
1095 -threaded
1097 Use the threaded runtime
1098 -with-rtsopts=⟨opts⟩
1100 Set the default RTS options to ⟨opts⟩.
1101 Miscellaneous options
1103 -fexternal-interpreter
1104 Run interpreted code in a separate process
1105 -fglasgow-exts
1107 Deprecated. Enable most language extensions; see options-lan‐
1108 guage for exactly which ones.
1109 -ghcversion-file ⟨path to ghcversion.h⟩
1111 (GHC as a C compiler only) Use this ghcversion.h file
1112 -H ⟨size⟩
1114 Set the minimum size of the heap to ⟨size⟩
1115 -j[⟨n⟩]
1117 When compiling with --make, compile ⟨n⟩ modules in parallel.
1118 Modes of operation
1120 --frontend ⟨module⟩
1121 run GHC with the given frontend plugin; see frontend_plugins for
1122 details.
1123 --help Display help
1125 --info display information about the compiler
1127 --interactive
1129 Interactive mode - normally used by just running ghci; see ghci
1130 for details.
1131 --make Build a multi-module Haskell program, automatically figuring out
1133 dependencies. Likely to be much easier, and faster, than using
1134 make; see make-mode for details.
1135 --mk-dll
1137 DLL-creation mode (Windows only)
1138 --numeric-version
1140 display GHC version (numeric only)
1141 --print-libdir
1143 display GHC library directory
1144 --show-iface ⟨file⟩
1146 display the contents of an interface file.
1147 --show-options
1149 display the supported command line options
1150 --supported-extensions
1152 display the supported language extensions
1153 --version
1155 display GHC version
1156 -e ⟨expr⟩
1158 Evaluate expr; see eval-mode for details.
1159 -M generate dependency information suitable for use in a Makefile;
1161 see makefile-dependencies for details.
1162 Individual optimizations
1164 -fcall-arity
1165 Enable call-arity optimisation. Implied by -O.
1166 -fcase-folding
1168 Enable constant folding in case expressions. Implied by -O.
1169 -fcase-merge
1171 Enable case-merging. Implied by -O.
1172 -fcmm-elim-common-blocks
1174 Enable Cmm common block elimination. Implied by -O.
1175 -fcmm-sink
1177 Enable Cmm sinking. Implied by -O.
1178 -fcpr-anal
1180 Turn on CPR analysis in the demand analyser. Implied by -O.
1181 -fcross-module-specialise
1183 Turn on specialisation of overloaded functions imported from
1184 other modules.
1185 -fcse Enable common sub-expression elimination. Implied by -O.
1187 -fdicts-cheap
1189 Make dictionary-valued expressions seem cheap to the optimiser.
1190 -fdicts-strict
1192 Make dictionaries strict
1193 -fdmd-tx-dict-sel
1195 Use a special demand transformer for dictionary selectors.
1196 Always enabled by default.
1197 -fdo-eta-reduction
1199 Enable eta-reduction. Implied by -O.
1200 -fdo-lambda-eta-expansion
1202 Enable lambda eta-expansion. Always enabled by default.
1203 -feager-blackholing
1205 Turn on eager blackholing
1206 -fenable-rewrite-rules
1208 Switch on all rewrite rules (including rules generated by auto‐
1209 matic specialisation of overloaded functions). Implied by -O.
1210 -fexcess-precision
1212 Enable excess intermediate precision
1213 -fexitification
1215 Enables exitification optimisation. Implied by -O.
1216 -fexpose-all-unfoldings
1218 Expose all unfoldings, even for very large or recursive func‐
1219 tions.
1220 -ffloat-in
1222 Turn on the float-in transformation. Implied by -O.
1223 -ffull-laziness
1225 Turn on full laziness (floating bindings outwards). Implied by
1226 -O.
1227 -ffun-to-thunk
1229 Allow worker-wrapper to convert a function closure into a thunk
1230 if the function does not use any of its arguments. Off by
1231 default.
1232 -fignore-asserts
1234 Ignore assertions in the source. Implied by -O.
1235 -fignore-interface-pragmas
1237 Ignore pragmas in interface files. Implied by -O0 only.
1238 -flate-dmd-anal
1240 Run demand analysis again, at the end of the simplification
1241 pipeline
1242 -fliberate-case
1244 Turn on the liberate-case transformation. Implied by -O2.
1245 -fliberate-case-threshold=⟨n⟩
1247 default: 2000. Set the size threshold for the liberate-case
1248 transformation to ⟨n⟩
1249 -fllvm-pass-vectors-in-regs
1251 Pass vector value in vector registers for function calls
1252 -floopification
1254 Turn saturated self-recursive tail-calls into local jumps in the
1255 generated assembly. Implied by -O.
1256 -fmax-inline-alloc-size=⟨n⟩
1258 default: 128. Set the maximum size of inline array allocations
1259 to ⟨n⟩ bytes (default: 128).
1260 -fmax-inline-memcpy-insns=⟨n⟩
1262 default: 32. Inline memcpy calls if they would generate no more
1263 than ⟨n⟩ pseudo instructions.
1264 -fmax-inline-memset-insns=⟨n⟩
1266 default: 32. Inline memset calls if they would generate no more
1267 than ⟨n⟩ pseudo instructions
1268 -fmax-relevant-binds=⟨n⟩
1270 default: 6. Set the maximum number of bindings to display in
1271 type error messages.
1272 -fmax-simplifier-iterations=⟨n⟩
1274 default: 4. Set the max iterations for the simplifier.
1275 -fmax-uncovered-patterns=⟨n⟩
1277 default: 4. Set the maximum number of patterns to display in
1278 warnings about non-exhaustive ones.
1279 -fmax-valid-substitutions=⟨n⟩
1281 default: 6. Set the maximum number of valid substitutions for
1282 typed holes to display in type error messages.
1283 -fmax-worker-args=⟨n⟩
1285 default: 10. If a worker has that many arguments, none will be
1286 unpacked anymore.
1287 -fno-opt-coercion
1289 Turn off the coercion optimiser
1290 -fno-pre-inlining
1292 Turn off pre-inlining
1293 -fno-state-hack
1295 Turn off the state hackwhereby any lambda with a real-world
1296 state token as argument is considered to be single-entry. Hence
1297 OK to inline things inside it.
1298 -fomit-interface-pragmas
1300 Don't generate interface pragmas. Implied by -O0 only.
1301 -fomit-yields
1303 Omit heap checks when no allocation is being performed.
1304 -foptimal-applicative-do
1306 Use a slower but better algorithm for ApplicativeDo
1307 -fpedantic-bottoms
1309 Make GHC be more precise about its treatment of bottom (but see
1310 also -fno-state-hack). In particular, GHC will not eta-expand
1311 through a case expression.
1312 -fregs-graph
1314 Use the graph colouring register allocator for register alloca‐
1315 tion in the native code generator. Implied by -O2.
1316 -fregs-iterative
1318 Use the iterative coalescing graph colouring register allocator
1319 in the native code generator.
1320 -fsimpl-tick-factor=⟨n⟩
1322 default: 100. Set the percentage factor for simplifier ticks.
1323 -fsimplifier-phases=⟨n⟩
1325 default: 2. Set the number of phases for the simplifier.
1326 Ignored with -O0.
1327 -fsolve-constant-dicts
1329 When solving constraints, try to eagerly solve super classes
1330 using available dictionaries.
1331 -fspec-constr
1333 Turn on the SpecConstr transformation. Implied by -O2.
1334 -fspec-constr-count=⟨n⟩
1336 default: 3.* Set to ⟨n⟩ the maximum number of specialisations
1337 that will be created for any one function by the SpecConstr
1338 transformation.
1339 -fspec-constr-keen
1341 Specialize a call with an explicit constructor argument, even if
1342 the argument is not scrutinised in the body of the function
1343 -fspec-constr-threshold=⟨n⟩
1345 default: 2000. Set the size threshold for the SpecConstr trans‐
1346 formation to ⟨n⟩.
1347 -fspecialise
1349 Turn on specialisation of overloaded functions. Implied by -O.
1350 -fspecialise-aggressively
1352 Turn on specialisation of overloaded functions regardless of
1353 size, if unfolding is available
1354 -fstatic-argument-transformation
1356 Turn on the static argument transformation.
1357 -fstg-cse
1359 Enable common sub-expression elimination on the STG intermediate
1360 language
1361 -fstrictness
1363 Turn on strictness analysis. Implied by -O. Implies
1364 -fworker-wrapper
1365 -fstrictness-before=⟨n⟩
1367 Run an additional strictness analysis before simplifier phase
1368 ⟨n⟩
1369 -funbox-small-strict-fields
1371 Flatten strict constructor fields with a pointer-sized represen‐
1372 tation. Implied by -O.
1373 -funbox-strict-fields
1375 Flatten strict constructor fields
1376 -funfolding-creation-threshold=⟨n⟩
1378 default: 750. Tweak unfolding settings.
1379 -funfolding-dict-discount=⟨n⟩
1381 default: 30. Tweak unfolding settings.
1382 -funfolding-fun-discount=⟨n⟩
1384 default: 60. Tweak unfolding settings.
1385 -funfolding-keeness-factor=⟨n⟩
1387 default: 1.5. Tweak unfolding settings.
1388 -funfolding-use-threshold=⟨n⟩
1390 default: 60. Tweak unfolding settings.
1391 -fvectorisation-avoidance
1393 Enable vectorisation avoidance. Always enabled by default.
1394 -fvectorise
1396 Enable vectorisation of nested data parallelism
1397 Optimization levels
1399 -O Enable level 1 optimisations
1400 -O0 Disable optimisations (default)
1402 -O2 Enable level 2 optimisations
1404 -Odph Enable level 2 optimisations, set -fmax-simplifier-iterations=20
1406 and -fsimplifier-phases=3.
1407 Package options
1409 -clear-package-db
1410 Clear the package db stack.
1411 -distrust ⟨pkg⟩
1413 Expose package ⟨pkg⟩ and set it to be distrusted. See
1414 safe-haskell.
1415 -distrust-all-packages
1417 Distrust all packages by default. See safe-haskell.
1418 -fpackage-trust
1420 Enable Safe Haskell trusted package requirement for trustworthy
1421 modules.
1422 -global-package-db
1424 Add the global package db to the stack.
1425 -hide-all-packages
1427 Hide all packages by default
1428 -hide-package ⟨pkg⟩
1430 Hide package ⟨pkg⟩
1431 -ignore-package ⟨pkg⟩
1433 Ignore package ⟨pkg⟩
1434 -no-auto-link-packages
1436 Don't automatically link in the base and rts packages.
1437 -no-global-package-db
1439 Remove the global package db from the stack.
1440 -no-user-package-db
1442 Remove the user's package db from the stack.
1443 -package ⟨pkg⟩
1445 Expose package ⟨pkg⟩
1446 -package-db ⟨file⟩
1448 Add ⟨file⟩ to the package db stack.
1449 -package-env ⟨file⟩|⟨name⟩
1451 Use the specified package environment.
1452 -package-id ⟨unit-id⟩
1454 Expose package by id ⟨unit-id⟩
1455 -this-unit-id ⟨unit-id⟩
1457 Compile to be part of unit (i.e. package) ⟨unit-id⟩
1458 -trust ⟨pkg⟩
1460 Expose package ⟨pkg⟩ and set it to be trusted. See safe-haskell.
1461 -user-package-db
1463 Add the user's package db to the stack.
1464 Phases of compilation
1466 -C Stop after generating C (.hc file)
1467 -c Stop after generating object (.o) file
1469 -E Stop after preprocessing (.hspp file)
1471 -F Enable the use of a pre-processor (set with -pgmF ⟨cmd⟩)
1473 -S Stop after generating assembly (.s file)
1475 -x ⟨suffix⟩
1477 Override default behaviour for source files
1478 Overriding external programs
1480 -pgma ⟨cmd⟩
1481 Use ⟨cmd⟩ as the assembler
1482 -pgmc ⟨cmd⟩
1484 Use ⟨cmd⟩ as the C compiler
1485 -pgmdll ⟨cmd⟩
1487 Use ⟨cmd⟩ as the DLL generator
1488 -pgmF ⟨cmd⟩
1490 Use ⟨cmd⟩ as the pre-processor (with -F only)
1491 -pgmi ⟨cmd⟩
1493 Use ⟨cmd⟩ as the external interpreter command.
1494 -pgmL ⟨cmd⟩
1496 Use ⟨cmd⟩ as the literate pre-processor
1497 -pgml ⟨cmd⟩
1499 Use ⟨cmd⟩ as the linker
1500 -pgmlc ⟨cmd⟩
1502 Use ⟨cmd⟩ as the LLVM compiler
1503 -pgmlibtool ⟨cmd⟩
1505 Use ⟨cmd⟩ as the command for libtool (with -staticlib only).
1506 -pgmlo ⟨cmd⟩
1508 Use ⟨cmd⟩ as the LLVM optimiser
1509 -pgmP ⟨cmd⟩
1511 Use ⟨cmd⟩ as the C pre-processor (with -cpp only)
1512 -pgms ⟨cmd⟩
1514 Use ⟨cmd⟩ as the splitter
1515 -pgmwindres ⟨cmd⟩
1517 Use ⟨cmd⟩ as the program for embedding manifests on Windows.
1518 Phase-specific options
1520 -opta ⟨option⟩
1521 pass ⟨option⟩ to the assembler
1522 -optc ⟨option⟩
1524 pass ⟨option⟩ to the C compiler
1525 -optdll ⟨option⟩
1527 pass ⟨option⟩ to the DLL generator
1528 -optF ⟨option⟩
1530 pass ⟨option⟩ to the custom pre-processor
1531 -opti ⟨option⟩
1533 pass ⟨option⟩ to the interpreter sub-process.
1534 -optL ⟨option⟩
1536 pass ⟨option⟩ to the literate pre-processor
1537 -optl ⟨option⟩
1539 pass ⟨option⟩ to the linker
1540 -optlc ⟨option⟩
1542 pass ⟨option⟩ to the LLVM compiler
1543 -optlo ⟨option⟩
1545 pass ⟨option⟩ to the LLVM optimiser
1546 -optP ⟨option⟩
1548 pass ⟨option⟩ to cpp (with -cpp only)
1549 -optwindres ⟨option⟩
1551 pass ⟨option⟩ to windres.
1552 Platform-specific options
1554 -msse2 (x86 only) Use SSE2 for floating-point operations
1555 -msse4.2
1557 (x86 only) Use SSE4.2 for floating-point operations
1558 Compiler plugins
1560 -fplugin-opt=⟨module⟩:⟨args⟩
1561 Give arguments to a plugin module; module must be specified with
1562 -fplugin=⟨module⟩
1563 -fplugin=⟨module⟩
1565 Load a plugin exported by a given module
1566 -hide-all-plugin-packages
1568 Hide all packages for plugins by default
1569 -plugin-package ⟨pkg⟩
1571 Expose ⟨pkg⟩ for plugins
1572 -plugin-package-id ⟨pkg-id⟩
1574 Expose ⟨pkg-id⟩ for plugins
1575 Profiling
1577 -fno-prof-auto
1578 Disables any previous -fprof-auto, -fprof-auto-top, or
1579 -fprof-auto-exported options.
1580 -fno-prof-cafs
1582 Disables any previous -fprof-cafs option.
1583 -fno-prof-count-entries
1585 Do not collect entry counts
1586 -fprof-auto
1588 Auto-add SCC\ s to all bindings not marked INLINE
1589 -fprof-auto-calls
1591 Auto-add SCC\ s to all call sites
1592 -fprof-auto-exported
1594 Auto-add SCC\ s to all exported bindings not marked INLINE
1595 -fprof-auto-top
1597 Auto-add SCC\ s to all top-level bindings not marked INLINE
1598 -fprof-cafs
1600 Auto-add SCC\ s to all CAFs
1601 -prof Turn on profiling
1603 -ticky Turn on ticky-ticky profiling
1605 Program coverage
1607 -fhpc Turn on Haskell program coverage instrumentation
1608 Recompilation checking
1610 -fforce-recomp
1611 Turn off recompilation checking. This is implied by any -ddump-X
1612 option when compiling a single file (i.e. when using -c).
1613 -fignore-hpc-changes
1615 Do not recompile modules just to match changes to HPC flags.
1616 This is especially useful for avoiding recompilation when using
1617 GHCi, and is enabled by default for GHCi.
1618 -fignore-optim-changes
1620 Do not recompile modules just to match changes to optimisation
1621 flags. This is especially useful for avoiding recompilation when
1622 using GHCi, and is enabled by default for GHCi.
1623 Redirecting output
1625 --exclude-module=⟨file⟩
1626 Regard ⟨file⟩ as "stable"; i.e., exclude it from having depen‐
1627 dencies on it.
1628 -ddump-mod-cycles
1630 Dump module cycles
1631 -dep-makefile ⟨file⟩
1633 Use ⟨file⟩ as the makefile
1634 -dep-suffix ⟨suffix⟩
1636 Make dependencies that declare that files with suffix
1637 .⟨suf⟩⟨osuf⟩ depend on interface files with suffix .⟨suf⟩hi
1638 -dumpdir ⟨dir⟩
1640 redirect dump files
1641 -hcsuf ⟨suffix⟩
1643 set the suffix to use for intermediate C files
1644 -hidir ⟨dir⟩
1646 set directory for interface files
1647 -hisuf ⟨suffix⟩
1649 set the suffix to use for interface files
1650 -include-pkg-deps
1652 Regard modules imported from packages as unstable
1653 -o ⟨file⟩
1655 set output filename
1656 -odir ⟨dir⟩
1658 set directory for object files
1659 -ohi ⟨file⟩
1661 set the filename in which to put the interface
1662 -osuf ⟨suffix⟩
1664 set the output file suffix
1665 -outputdir ⟨dir⟩
1667 set output directory
1668 -stubdir ⟨dir⟩
1670 redirect FFI stub files
1671 Temporary files
1673 -tmpdir ⟨dir⟩
1674 set the directory for temporary files
1675 Verbosity options
1677 -fdiagnostics-color=⟨always|auto|never⟩
1678 Use colors in error messages
1679 -fdiagnostics-show-caret
1681 Whether to show snippets of original source code
1682 -ferror-spans
1684 Output full span in error messages
1685 -fhide-source-paths
1687 hide module source and object paths
1688 -fprint-equality-relations
1690 Distinguish between equality relations when printing
1691 -fprint-expanded-synonyms
1693 In type errors, also print type-synonym-expanded types.
1694 -fprint-explicit-coercions
1696 Print coercions in types
1697 -fprint-explicit-foralls
1699 Print explicit forall quantification in types. See also -XEx‐
1700 plicitForAll
1701 -fprint-explicit-kinds
1703 Print explicit kind foralls and kind arguments in types. See
1704 also -XKindSignatures
1705 -fprint-explicit-runtime-rep
1707 Print RuntimeRep variables in types which are runtime-represen‐
1708 tation polymorphic.
1709 -fprint-explicit-runtime-reps
1711 Print RuntimeRep variables in types which are runtime-represen‐
1712 tation polymorphic.
1713 -fprint-potential-instances
1715 display all available instances in type error messages
1716 -fprint-typechecker-elaboration
1718 Print extra information from typechecker.
1719 -fprint-unicode-syntax
1721 Use unicode syntax when printing expressions, types and kinds.
1722 See also -XUnicodeSyntax
1723 -fshow-hole-constraints
1725 Show constraints when reporting typed holes
1726 -Rghc-timing
1728 Summarise timing stats for GHC (same as +RTS -tstderr).
1729 -v verbose mode (equivalent to -v3)
1731 -v⟨n⟩ set verbosity level
1733 Warnings
1735 -fdefer-out-of-scope-variables
1736 Convert variable out of scope variables errors into warnings.
1737 Implied by -fdefer-type-errors. See also -Wde‐
1738 ferred-out-of-scope-variables.
1739 -fdefer-type-errors
1741 Turn type errors into warnings, deferring the error until run‐
1742 time. Implies -fdefer-typed-holes and -fdefer-out-of-scope-vari‐
1743 ables. See also -Wdeferred-type-errors
1744 -fdefer-typed-holes
1746 Convert typed hole errors into warnings, deferring the error
1747 until runtime. Implied by -fdefer-type-errors. See also
1748 -Wtyped-holes.
1749 -fhelpful-errors
1751 Make suggestions for mis-spelled names.
1752 -fmax-pmcheck-iterations=⟨n⟩
1754 the iteration limit for the pattern match checker
1755 -fshow-warning-groups
1757 show which group an emitted warning belongs to.
1758 -W enable normal warnings
1760 -w disable all warnings
1762 -Wall enable almost all warnings (details in options-sanity)
1764 -Wall-missed-specialisations
1766 warn when specialisation of any overloaded function fails.
1767 -Wamp (deprecated) warn on definitions conflicting with the Applica‐
1769 tive-Monad Proposal (AMP)
1770 -Wcompat
1772 enable future compatibility warnings (details in options-sanity)
1773 -Wcpp-undef
1775 warn on uses of the #if directive on undefined identifiers
1776 -Wdeferred-out-of-scope-variables
1778 Report warnings when variable out-of-scope errors are deferred
1779 until runtime. See -fdefer-out-of-scope-variables.
1780 -Wdeferred-type-errors
1782 Report warnings when deferred type errors are enabled. This
1783 option is enabled by default. See -fdefer-type-errors.
1784 -Wdeprecated-flags
1786 warn about uses of commandline flags that are deprecated
1787 -Wdeprecations
1789 warn about uses of functions & types that have warnings or dep‐
1790 recated pragmas. Alias for -Wwarnings-deprecations
1791 -Wdodgy-exports
1793 warn about dodgy exports
1794 -Wdodgy-foreign-imports
1796 warn about dodgy foreign imports
1797 -Wdodgy-imports
1799 warn about dodgy imports
1800 -Wduplicate-constraints
1802 warn when a constraint appears duplicated in a type signature
1803 -Wduplicate-exports
1805 warn when an entity is exported multiple times
1806 -Wempty-enumerations
1808 warn about enumerations that are empty
1809 -Werror
1811 make warnings fatal
1812 -Weverything
1814 enable all warnings supported by GHC
1815 -Whi-shadowing
1817 warn when a .hi file in the current directory shadows a library
1818 -Widentities
1820 warn about uses of Prelude numeric conversions that are probably
1821 the identity (and hence could be omitted)
1822 -Wimplicit-prelude
1824 warn when the Prelude is implicitly imported
1825 -Wincomplete-patterns
1827 warn when a pattern match could fail
1828 -Wincomplete-record-updates
1830 warn when a record update could fail
1831 -Wincomplete-uni-patterns
1833 warn when a pattern match in a lambda expression or pattern
1834 binding could fail
1835 -Winline-rule-shadowing
1837 Warn if a rewrite RULE might fail to fire because the function
1838 might be inlined before the rule has a chance to fire. See
1839 rules-inline.
1840 -Wmissed-specialisations
1842 warn when specialisation of an imported, overloaded function
1843 fails.
1844 -Wmissing-export-lists
1846 warn when a module declaration does not explicitly list all
1847 exports
1848 -Wmissing-exported-signatures
1850 warn about top-level functions without signatures, only if they
1851 are exported. takes precedence over -Wmissing-signatures
1852 -Wmissing-exported-sigs
1854 (deprecated) warn about top-level functions without signatures,
1855 only if they are exported. takes precedence over -Wmissing-sig‐
1856 natures
1857 -Wmissing-fields
1859 warn when fields of a record are uninitialised
1860 -Wmissing-home-modules
1862 warn when encountering a home module imported, but not listed on
1863 the command line. Useful for cabal to ensure GHC won't pick up
1864 modules, not listed neither in exposed-modules, nor in
1865 other-modules.
1866 -Wmissing-import-lists
1868 warn when an import declaration does not explicitly list all the
1869 names brought into scope
1870 -Wmissing-local-signatures
1872 warn about polymorphic local bindings without signatures
1873 -Wmissing-local-sigs
1875 (deprecated) warn about polymorphic local bindings without sig‐
1876 natures
1877 -Wmissing-methods
1879 warn when class methods are undefined
1880 -Wmissing-monadfail-instances
1882 Warn when a failable pattern is used in a do-block that does not
1883 have a MonadFail instance.
1884 -Wmissing-pattern-synonym-signatures
1886 warn when pattern synonyms do not have type signatures
1887 -Wmissing-signatures
1889 warn about top-level functions without signatures
1890 -Wmonomorphism-restriction
1892 warn when the Monomorphism Restriction is applied
1893 -Wname-shadowing
1895 warn when names are shadowed
1896 -Wno-compat
1898 Disables all warnings enabled by -Wcompat.
1899 -Wnoncanonical-monad-instances
1901 warn when Applicative or Monad instances have noncanonical defi‐
1902 nitions of return, pure, (>>), or (*>). See flag description in
1903 options-sanity for more details.
1904 -Wnoncanonical-monadfail-instances
1906 warn when Monad or MonadFail instances have noncanonical defini‐
1907 tions of fail. See flag description in options-sanity for more
1908 details.
1909 -Wnoncanonical-monoid-instances
1911 warn when Semigroup or Monoid instances have noncanonical defi‐
1912 nitions of (<>) or mappend. See flag description in
1913 options-sanity for more details.
1914 -Worphans
1916 warn when the module contains orphan instance declarations or
1917 rewrite rules
1918 -Woverflowed-literals
1920 warn about literals that will overflow their type
1921 -Woverlapping-patterns
1923 warn about overlapping patterns
1924 -Wpartial-fields
1926 warn when defining a partial record field.
1927 -Wpartial-type-signatures
1929 warn about holes in partial type signatures when -XPartialTypeS‐
1930 ignatures is enabled. Not applicable when -XPartialTypesigna‐
1931 tures is not enabled, in which case errors are generated for
1932 such holes. See partial-type-signatures.
1933 -Wredundant-constraints
1935 Have the compiler warn about redundant constraints in type sig‐
1936 natures.
1937 -Wsafe warn if the module being compiled is regarded to be safe.
1939 -Wsemigroup
1941 warn when a Monoid is not Semigroup, and on non- Semigroup defi‐
1942 nitions of (<>)?
1943 -Wsimplifiable-class-constraints
1945 2arn about class constraints in a type signature that can be
1946 simplified using a top-level instance declaration.
1947 -Wtabs warn if there are tabs in the source file
1949 -Wtrustworthy-safe
1951 warn if the module being compiled is marked as Trustworthy but
1952 it could instead be marked as Safe, a more informative bound.
1953 -Wtype-defaults
1955 warn when defaulting happens
1956 -Wtyped-holes
1958 Report warnings when typed hole errors are deferred until run‐
1959 time. See -fdefer-typed-holes.
1960 -Wunbanged-strict-patterns
1962 warn on pattern bind of unlifted variable that is neither bare
1963 nor banged
1964 -Wunrecognised-pragmas
1966 warn about uses of pragmas that GHC doesn't recognise
1967 -Wunrecognised-warning-flags
1969 throw a warning when an unreconised -W... flag is encountered on
1970 the command line.
1971 -Wunsafe
1973 warn if the module being compiled is regarded to be unsafe. See
1974 safe-haskell
1975 -Wunsupported-calling-conventions
1977 warn about use of an unsupported calling convention
1978 -Wunsupported-llvm-version
1980 Warn when using -fllvm with an unsupported version of LLVM.
1981 -Wunticked-promoted-constructors
1983 warn if promoted constructors are not ticked
1984 -Wunused-binds
1986 warn about bindings that are unused. Alias for
1987 -Wunused-top-binds, -Wunused-local-binds and -Wunused-pat‐
1988 tern-binds
1989 -Wunused-do-bind
1991 warn about do bindings that appear to throw away values of types
1992 other than ()
1993 -Wunused-foralls
1995 warn about type variables in user-written forall\s that are
1996 unused
1997 -Wunused-imports
1999 warn about unnecessary imports
2000 -Wunused-local-binds
2002 warn about local bindings that are unused
2003 -Wunused-matches
2005 warn about variables in patterns that aren't used
2006 -Wunused-pattern-binds
2008 warn about pattern match bindings that are unused
2009 -Wunused-top-binds
2011 warn about top-level bindings that are unused
2012 -Wunused-type-patterns
2014 warn about unused type variables which arise from patterns in
2015 type family and data family instances
2016 -Wwarn make warnings non-fatal
2018 -Wwarnings-deprecations
2020 warn about uses of functions & types that have warnings or dep‐
2021 recated pragmas
2022 -Wwrong-do-bind
2024 warn about do bindings that appear to throw away monadic values
2025 that you should have bound instead
2026
2028 Copyright 2015. The University Court of the University of Glasgow. All
2029 rights reserved.
2030
2032 The GHC Team
2033
2035 2015, GHC Team
20368.4.4 Mar 04, 2019 GHC(1)