8.6. Flag reference — Glasgow Haskell Compiler 8.8.3 User's Guide

# Glasgow Haskell Compiler User's Guide

# 8.6. Flag reference

This section is a quick-reference for GHC’s command-line flags. For each flag, we also list its mode/dynamic status (see Dynamic and Mode options), and the flag’s opposite (if available).

## 8.6.1. Verbosity options

More details in Verbosity options

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-fabstract-refinement-hole-fits` | default: off. Toggles whether refinements where one or more of the holes are abstract are reported. | dynamic | `-fno-abstract-refinement-hole-fits`
`-fdiagnostics-color=⟨always|auto|never⟩` | Use colors in error messages | dynamic |
`-fdiagnostics-show-caret` | Whether to show snippets of original source code | dynamic | `-fno-diagnostics-show-caret`
`-ferror-spans` | Output full span in error messages | dynamic |
`-fhide-source-paths` | hide module source and object paths | dynamic |
`-fmax-refinement-hole-fits=⟨n⟩` | default: 6. Set the maximum number of refinement hole fits for typed holes to display in type error messages. | dynamic | `-fno-max-refinement-hole-fits`
`-fmax-relevant-binds=⟨n⟩` | default: 6. Set the maximum number of bindings to display in type error messages. | dynamic | `-fno-max-relevant-bindings`
`-fmax-valid-hole-fits=⟨n⟩` | default: 6. Set the maximum number of valid hole fits for typed holes to display in type error messages. | dynamic | `-fno-max-valid-hole-fits`
`-fno-show-valid-hole-fits` | Disables showing a list of valid hole fits for typed holes in type error messages. | dynamic |
`-fno-sort-valid-hole-fits` | Disables the sorting of the list of valid hole fits for typed holes in type error messages. | dynamic |
`-fprint-equality-relations` | Distinguish between equality relations when printing | dynamic | `-fno-print-equality-relations`
`-fprint-expanded-synonyms` | In type errors, also print type-synonym-expanded types. | dynamic | `-fno-print-expanded-synonyms`
`-fprint-explicit-coercions` | Print coercions in types | dynamic | `-fno-print-explicit-coercions`
`-fprint-explicit-foralls` | Print explicit `forall` quantification in types. See also `-XExplicitForAll` | dynamic | `-fno-print-explicit-foralls`
`-fprint-explicit-kinds` | Print explicit kind foralls and kind arguments in types. See also `-XKindSignatures` | dynamic | `-fno-print-explicit-kinds`
`-fprint-explicit-runtime-reps` | Print `RuntimeRep` variables in types which are runtime-representation polymorphic. | dynamic | `-fno-print-explicit-runtime-reps`
`-fprint-explicit-runtime-reps` | Print `RuntimeRep` variables in types which are runtime-representation polymorphic. | dynamic | `-fno-print-explicit-runtime-reps`
`-fprint-potential-instances` | display all available instances in type error messages | dynamic | `-fno-print-potential-instances`
`-fprint-typechecker-elaboration` | Print extra information from typechecker. | dynamic | `-fno-print-typechecker-elaboration`
`-fprint-unicode-syntax` | Use unicode syntax when printing expressions, types and kinds. See also `-XUnicodeSyntax` | dynamic | `-fno-print-unicode-syntax`
`-frefinement-level-hole-fits=⟨n⟩` | default: off. Sets the level of refinement of the refinement hole fits, where level `n` means that hole fits of up to `n` holes will be considered. | dynamic | `-fno-refinement-level-hole-fits`
`-freverse-errors` | Output errors in reverse order | dynamic | `-fno-reverse-errors`
`-fshow-docs-of-hole-fits` | Toggles whether to show the documentation of the valid hole fits in the output. | dynamic | `-fno-show-docs-of-hole-fits`
`-fshow-hole-constraints` | Show constraints when reporting typed holes. | dynamic |
`-fshow-hole-matches-of-hole-fits` | Toggles whether to show the type of the additional holes in refinement hole fits. | dynamic | `-fno-show-hole-matches-of-hole-fits`
`-fshow-provenance-of-hole-fits` | Toggles whether to show the provenance of the valid hole fits in the output. | dynamic | `-fno-show-provenance-of-hole-fits`
`-fshow-type-app-of-hole-fits` | Toggles whether to show the type application of the valid hole fits in the output. | dynamic | `-fno-show-type-app-of-hole-fits`
`-fshow-type-app-vars-of-hole-fits` | Toggles whether to show what type each quantified variable takes in a valid hole fit. | dynamic | `-fno-show-type-app-vars-of-hole-fits`
`-fshow-type-of-hole-fits` | Toggles whether to show the type of the valid hole fits in the output. | dynamic | `-fno-type-of-hole-fits`
`-funclutter-valid-hole-fits` | Unclutter the list of valid hole fits by not showing provenance nor type applications of suggestions. | dynamic |
`-Rghc-timing` | Summarise timing stats for GHC (same as `+RTS -tstderr`). | dynamic |
`-v` | verbose mode (equivalent to `-v3`) | dynamic |
`-v⟨n⟩` | set verbosity level | dynamic |

## 8.6.2. Alternative modes of operation

More details in Modes of operation

Flag | Description | Type | Reverse
--- | --- | --- | ---
`--frontend ⟨module⟩` | run GHC with the given frontend plugin; see Frontend plugins for details. | mode |
`--help`, `-?` | Display help | mode |
`--info` | display information about the compiler | mode |
`--interactive` | Interactive mode - normally used by just running `ghci`; see Using GHCi for details. | mode |
`--make` | Build a multi-module Haskell program, automatically figuring out dependencies. Likely to be much easier, and faster, than using `make`; see Using ghc –make for details. | mode |
`--mk-dll` | DLL-creation mode (Windows only) | mode |
`--numeric-version` | display GHC version (numeric only) | mode |
`--print-libdir` | display GHC library directory | mode |
`--show-iface ⟨file⟩` | display the contents of an interface file. | mode |
`--show-options` | display the supported command line options | mode |
`--supported-extensions`, `--supported-languages` | display the supported language extensions | mode |
`--version`, `-V` | display GHC version | mode |
`-e ⟨expr⟩` | Evaluate `expr`; see Expression evaluation mode for details. | mode |
`-M` | generate dependency information suitable for use in a `Makefile`; see Dependency generation for details. | mode |

## 8.6.3. Which phases to run

More details in Batch compiler mode

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-C` | Stop after generating C (`.hc` file) | mode |
`-c` | Stop after generating object (`.o`) file | mode |
`-E` | Stop after preprocessing (`.hspp` file) | mode |
`-F` | Enable the use of a pre-processor (set with `-pgmF ⟨cmd⟩`) | dynamic |
`-S` | Stop after generating assembly (`.s` file) | mode |
`-x ⟨suffix⟩` | Override default behaviour for source files | dynamic |

## 8.6.4. Redirecting output

More details in Redirecting the compilation output(s)

Flag | Description | Type | Reverse
--- | --- | --- | ---
`--exclude-module=⟨file⟩` | Regard `⟨file⟩` as “stable”; i.e., exclude it from having dependencies on it. | dynamic |
`-ddump-mod-cycles` | Dump module cycles | dynamic |
`-dep-makefile ⟨file⟩` | Use ⟨file⟩ as the makefile | dynamic |
`-dep-suffix ⟨suffix⟩` | Make dependencies that declare that files with suffix `.⟨suf⟩⟨osuf⟩` depend on interface files with suffix `.⟨suf⟩hi` | dynamic |
`-dumpdir ⟨dir⟩` | redirect dump files | dynamic |
`-hcsuf ⟨suffix⟩` | set the suffix to use for intermediate C files | dynamic |
`-hidir ⟨dir⟩` | set directory for interface files | dynamic |
`-hiedir ⟨dir⟩` | set directory for extended interface files | dynamic |
`-hiesuf ⟨suffix⟩` | set the suffix to use for extended interface files | dynamic |
`-hisuf ⟨suffix⟩` | set the suffix to use for interface files | dynamic |
`-include-pkg-deps` | Regard modules imported from packages as unstable | dynamic |
`-o ⟨file⟩` | set output filename | dynamic |
`-odir ⟨dir⟩` | set directory for object files | dynamic |
`-ohi ⟨file⟩` | set the filename in which to put the interface | dynamic |
`-osuf ⟨suffix⟩` | set the output file suffix | dynamic |
`-outputdir ⟨dir⟩` | set output directory | dynamic |
`-stubdir ⟨dir⟩` | redirect FFI stub files | dynamic |

## 8.6.5. Keeping intermediate files

More details in Keeping Intermediate Files

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-keep-hc-file`, `-keep-hc-files` | Retain intermediate `.hc` files. | dynamic |
`-keep-hi-files` | Retain intermediate `.hi` files (the default). | dynamic | `-no-keep-hi-files`
`-keep-hscpp-file`, `-keep-hscpp-files` | Retain intermediate `.hscpp` files. | dynamic |
`-keep-llvm-file`, `-keep-llvm-files` | Retain intermediate LLVM `.ll` files. Implies `-fllvm`. | dynamic |
`-keep-o-files` | Retain intermediate `.o` files (the default). | dynamic | `-no-keep-o-files`
`-keep-s-file`, `-keep-s-files` | Retain intermediate `.s` files. | dynamic |
`-keep-tmp-files` | Retain all intermediate temporary files. | dynamic |

## 8.6.6. Temporary files

More details in Redirecting temporary files

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-tmpdir ⟨dir⟩` | set the directory for temporary files | dynamic |

## 8.6.7. Finding imports

More details in The search path

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-i` | Empty the import directory list | dynamic |
`-i⟨dir⟩[:⟨dir⟩]*` | add ⟨dir⟩, ⟨dir2⟩, etc. to import path | dynamic |

## 8.6.8. Interface file options

More details in Other options related to interface files

Flag | Description | Type | Reverse
--- | --- | --- | ---
`--show-iface ⟨file⟩` | See Modes of operation. | mode |
`-ddump-hi` | Dump the new interface to stdout | dynamic |
`-ddump-hi-diffs` | Show the differences vs. the old interface | dynamic |
`-ddump-minimal-imports` | Dump a minimal set of imports | dynamic |

## 8.6.9. Recompilation checking

More details in The recompilation checker

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-fforce-recomp` | Turn off recompilation checking. This is implied by any `-ddump-X` option when compiling a single file (i.e. when using `-c`). | dynamic | `-fno-force-recomp`
`-fignore-hpc-changes` | Do not recompile modules just to match changes to HPC flags. This is especially useful for avoiding recompilation when using GHCi, and is enabled by default for GHCi. | dynamic | `-fno-ignore-hpc-changes`
`-fignore-optim-changes` | Do not recompile modules just to match changes to optimisation flags. This is especially useful for avoiding recompilation when using GHCi, and is enabled by default for GHCi. | dynamic | `-fno-ignore-optim-changes`

## 8.6.10. Interactive-mode options

More details in The .ghci and .haskeline files

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-fbreak-on-error` | Break on uncaught exceptions and errors | dynamic | `-fno-break-on-error`
`-fbreak-on-exception` | Break on any exception thrown | dynamic | `-fno-break-on-exception`
`-fghci-hist-size=⟨n⟩` | Set the number of entries GHCi keeps for `:history`. See The GHCi Debugger. | dynamic |
`-fghci-leak-check` | (Debugging only) check for space leaks when loading new modules in GHCi. | dynamic | `-fno-ghci-leak-check`
`-flocal-ghci-history` | Use current directory for the GHCi command history file `.ghci-history`. | dynamic | `-fno-local-ghci-history`
`-fno-it` | No longer set the special variable `it`. | dynamic | `-fno-no-it`
`-fprint-bind-result` | Turn on printing of binding results in GHCi | dynamic | `-fno-print-bind-result`
`-fshow-loaded-modules` | Show the names of modules that GHCi loaded after a `:load` command. | dynamic |
`-ghci-script` | Read additional `.ghci` files | dynamic |
`-ignore-dot-ghci` | Disable reading of `.ghci` files | dynamic |
`-interactive-print ⟨expr⟩` | Select the function to use for printing evaluated expressions in GHCi | dynamic |

## 8.6.11. Packages

More details in Packages

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-clear-package-db` | Clear the package db stack. | dynamic |
`-distrust ⟨pkg⟩` | Expose package ⟨pkg⟩ and set it to be distrusted. See Safe Haskell. | dynamic |
`-distrust-all-packages` | Distrust all packages by default. See Safe Haskell. | dynamic |
`-fpackage-trust` | Enable Safe Haskell trusted package requirement for trustworthy modules. | dynamic |
`-global-package-db` | Add the global package db to the stack. | dynamic |
`-hide-all-packages` | Hide all packages by default | dynamic |
`-hide-package ⟨pkg⟩` | Hide package ⟨pkg⟩ | dynamic |
`-ignore-package ⟨pkg⟩` | Ignore package ⟨pkg⟩ | dynamic |
`-no-auto-link-packages` | Don’t automatically link in the base and rts packages. | dynamic |
`-no-global-package-db` | Remove the global package db from the stack. | dynamic |
`-no-user-package-db` | Remove the user’s package db from the stack. | dynamic |
`-package ⟨pkg⟩` | Expose package ⟨pkg⟩ | dynamic |
`-package-db ⟨file⟩` | Add ⟨file⟩ to the package db stack. | dynamic |
`-package-env ⟨file⟩|⟨name⟩` | Use the specified package environment. | dynamic |
`-package-id ⟨unit-id⟩` | Expose package by id ⟨unit-id⟩ | dynamic |
`-this-unit-id ⟨unit-id⟩` | Compile to be part of unit (i.e. package) ⟨unit-id⟩ | dynamic |
`-trust ⟨pkg⟩` | Expose package ⟨pkg⟩ and set it to be trusted. See Safe Haskell. | dynamic |
`-user-package-db` | Add the user’s package db to the stack. | dynamic |

## 8.6.12. Language options

Language options can be enabled either by a command-line option `-Xblah`, or by a `{-# LANGUAGE blah #-}` pragma in the file itself. See Language options.

## 8.6.13. Warnings

More details in Warnings and sanity-checking

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-fdefer-out-of-scope-variables` | Convert variable out of scope variables errors into warnings. Implied by `-fdefer-type-errors`. See also `-Wdeferred-out-of-scope-variables`. | dynamic | `-fno-defer-out-of-scope-variables`
`-fdefer-type-errors` | Turn type errors into warnings, deferring the error until runtime. Implies `-fdefer-typed-holes` and `-fdefer-out-of-scope-variables`. See also `-Wdeferred-type-errors` | dynamic | `-fno-defer-type-errors`
`-fdefer-typed-holes` | Convert typed hole errors into warnings, deferring the error until runtime. Implied by `-fdefer-type-errors`. See also `-Wtyped-holes`. | dynamic | `-fno-defer-typed-holes`
`-fhelpful-errors` | Make suggestions for mis-spelled names. | dynamic | `-fno-helpful-errors`
`-fmax-pmcheck-iterations=⟨n⟩` | the iteration limit for the pattern match checker | dynamic |
`-fshow-warning-groups` | show which group an emitted warning belongs to. | dynamic | `-fno-show-warning-groups`
`-W` | enable normal warnings | dynamic | `-w`
`-w` | disable all warnings | dynamic |
`-Wall` | enable almost all warnings (details in Warnings and sanity-checking) | dynamic | `-w`
`-Wall-missed-specialisations` | warn when specialisation of any overloaded function fails. | dynamic | `-Wno-all-missed-specialisations`
`-Wcompat` | enable future compatibility warnings (details in Warnings and sanity-checking) | dynamic | `-Wno-compat`
`-Wcpp-undef` | warn on uses of the #if directive on undefined identifiers | dynamic |
`-Wdeferred-out-of-scope-variables` | Report warnings when variable out-of-scope errors are deferred until runtime. See `-fdefer-out-of-scope-variables`. | dynamic | `-Wno-deferred-out-of-scope-variables`
`-Wdeferred-type-errors` | Report warnings when deferred type errors are enabled. This option is enabled by default. See `-fdefer-type-errors`. | dynamic | `-Wno-deferred-type-errors`
`-Wdeprecated-flags` | warn about uses of commandline flags that are deprecated | dynamic | `-Wno-deprecated-flags`
`-Wdeprecations` | warn about uses of functions & types that have warnings or deprecated pragmas. Alias for `-Wwarnings-deprecations` | dynamic | `-Wno-deprecations`
`-Wdodgy-exports` | warn about dodgy exports | dynamic | `-Wno-dodgy-exports`
`-Wdodgy-foreign-imports` | warn about dodgy foreign imports | dynamic | `-Wno-dodgy-foreign-import`
`-Wdodgy-imports` | warn about dodgy imports | dynamic | `-Wno-dodgy-imports`
`-Wduplicate-constraints` | warn when a constraint appears duplicated in a type signature | dynamic | `-Wno-duplicate-constraints`
`-Wduplicate-exports` | warn when an entity is exported multiple times | dynamic | `-Wno-duplicate-exports`
`-Wempty-enumerations` | warn about enumerations that are empty | dynamic | `-Wno-empty-enumerations`
`-Werror` | make warnings fatal | dynamic | `-Wwarn`
`-Weverything` | enable all warnings supported by GHC | dynamic |
`-Whi-shadowing` | warn when a `.hi` file in the current directory shadows a library | dynamic | `-Wno-hi-shadowing`
`-Widentities` | warn about uses of Prelude numeric conversions that are probably the identity (and hence could be omitted) | dynamic | `-Wno-identities`
`-Wimplicit-kind-vars` | warn when kind variables are brought into scope implicitly despite the “forall-or-nothing” rule | dynamic | `-Wno-implicit-kind-vars`
`-Wimplicit-prelude` | warn when the Prelude is implicitly imported | dynamic | `-Wno-implicit-prelude`
`-Winaccessible-code` | warn about inaccessible code | dynamic | `-Wno-inaccessible-code`
`-Wincomplete-patterns` | warn when a pattern match could fail | dynamic | `-Wno-incomplete-patterns`
`-Wincomplete-record-updates` | warn when a record update could fail | dynamic | `-Wno-incomplete-record-updates`
`-Wincomplete-uni-patterns` | warn when a pattern match in a lambda expression or pattern binding could fail | dynamic | `-Wno-incomplete-uni-patterns`
`-Winline-rule-shadowing` | Warn if a rewrite RULE might fail to fire because the function might be inlined before the rule has a chance to fire. See How rules interact with INLINE/NOINLINE pragmas. | dynamic | `-Wno-inline-rule-shadowing`
`-Wmissed-extra-shared-lib` | Warn when GHCi can’t load a shared lib. | dynamic | `-Wno-missed-extra-shared-lib`
`-Wmissed-specialisations` | warn when specialisation of an imported, overloaded function fails. | dynamic | `-Wno-missed-specialisations`
`-Wmissing-deriving-strategies` | warn when a deriving clause is missing a deriving strategy | dynamic | `-Wno-missing-deriving-strategies`
`-Wmissing-export-lists` | warn when a module declaration does not explicitly list all exports | dynamic | `-fnowarn-missing-export-lists`
`-Wmissing-exported-signatures` | warn about top-level functions without signatures, only if they are exported. takes precedence over -Wmissing-signatures | dynamic | `-Wno-missing-exported-signatures`
`-Wmissing-exported-sigs` | (deprecated) warn about top-level functions without signatures, only if they are exported. takes precedence over -Wmissing-signatures | dynamic | `-Wno-missing-exported-sigs`
`-Wmissing-fields` | warn when fields of a record are uninitialised | dynamic | `-Wno-missing-fields`
`-Wmissing-home-modules` | warn when encountering a home module imported, but not listed on the command line. Useful for cabal to ensure GHC won’t pick up modules, not listed neither in `exposed-modules`, nor in `other-modules`. | dynamic | `-Wno-missing-home-modules`
`-Wmissing-import-lists` | warn when an import declaration does not explicitly list all the names brought into scope | dynamic | `-fnowarn-missing-import-lists`
`-Wmissing-local-signatures` | warn about polymorphic local bindings without signatures | dynamic | `-Wno-missing-local-signatures`
`-Wmissing-local-sigs` | (deprecated) warn about polymorphic local bindings without signatures | dynamic | `-Wno-missing-local-sigs`
`-Wmissing-methods` | warn when class methods are undefined | dynamic | `-Wno-missing-methods`
`-Wmissing-monadfail-instances` | Warn when a failable pattern is used in a do-block that does not have a `MonadFail` instance. | dynamic | `-Wno-missing-monadfail-instances`
`-Wmissing-pattern-synonym-signatures` | warn when pattern synonyms do not have type signatures | dynamic | `-Wno-missing-pattern-synonym-signatures`
`-Wmissing-signatures` | warn about top-level functions without signatures | dynamic | `-Wno-missing-signatures`
`-Wmonomorphism-restriction` | warn when the Monomorphism Restriction is applied | dynamic | `-Wno-monomorphism-restriction`
`-Wname-shadowing` | warn when names are shadowed | dynamic | `-Wno-name-shadowing`
`-Wno-compat` | Disables all warnings enabled by `-Wcompat`. | dynamic | `-Wcompat`
`-Wnoncanonical-monad-instances` | warn when `Applicative` or `Monad` instances have noncanonical definitions of `return`, `pure`, `(>>)`, or `(*>)`. See flag description in Warnings and sanity-checking for more details. | dynamic | `-Wno-noncanonical-monad-instances`
`-Wnoncanonical-monadfail-instances` | warn when `Monad` or `MonadFail` instances have noncanonical definitions of `fail`. See flag description in Warnings and sanity-checking for more details. | dynamic | `-Wno-noncanonical-monadfail-instances`
`-Wnoncanonical-monoid-instances` | warn when `Semigroup` or `Monoid` instances have noncanonical definitions of `(<>)` or `mappend`. See flag description in Warnings and sanity-checking for more details. | dynamic | `-Wno-noncanonical-monoid-instances`
`-Worphans` | warn when the module contains orphan instance declarations or rewrite rules | dynamic | `-Wno-orphans`
`-Woverflowed-literals` | warn about literals that will overflow their type | dynamic | `-Wno-overflowed-literals`
`-Woverlapping-patterns` | warn about overlapping patterns | dynamic | `-Wno-overlapping-patterns`
`-Wpartial-fields` | warn when defining a partial record field. | dynamic | `-Wno-partial-fields`
`-Wpartial-type-signatures` | warn about holes in partial type signatures when `-XPartialTypeSignatures` is enabled. Not applicable when `-XPartialTypesignatures` is not enabled, in which case errors are generated for such holes. See Partial Type Signatures. | dynamic | `-Wno-partial-type-signatures`
`-Wredundant-constraints` | Have the compiler warn about redundant constraints in type signatures. | dynamic | `-Wno-redundant-constraints`
`-Wsafe` | warn if the module being compiled is regarded to be safe. | dynamic | `-Wno-safe`
`-Wsemigroup` | warn when a `Monoid` is not `Semigroup`, and on non- `Semigroup` definitions of `(<>)`? | dynamic | `-Wno-semigroup`
`-Wsimplifiable-class-constraints` | Warn about class constraints in a type signature that can be simplified using a top-level instance declaration. | dynamic | `-Wno-simplifiable-class-constraints`
`-Wspace-after-bang` | warn for missing space before the second argument of an infix definition of `(!)` when `-XBangPatterns` are not enabled | dynamic | `-Wno-missing-space-after-bang`
`-Wstar-binder` | warn about binding the `(*)` type operator despite `-XStarIsType` | dynamic | `-Wno-star-binder`
`-Wstar-is-type` | warn when `*` is used to mean `Data.Kind.Type` | dynamic | `-Wno-star-is-type`
`-Wtabs` | warn if there are tabs in the source file | dynamic | `-Wno-tabs`
`-Wtrustworthy-safe` | warn if the module being compiled is marked as `Trustworthy` but it could instead be marked as `Safe`, a more informative bound. | dynamic | `-Wno-safe`
`-Wtype-defaults` | warn when defaulting happens | dynamic | `-Wno-type-defaults`
`-Wtyped-holes` | Report warnings when typed hole errors are deferred until runtime. See `-fdefer-typed-holes`. | dynamic | `-Wno-typed-holes`
`-Wunbanged-strict-patterns` | warn on pattern bind of unlifted variable that is neither bare nor banged | dynamic | `-Wno-unbanged-strict-patterns`
`-Wunrecognised-pragmas` | warn about uses of pragmas that GHC doesn’t recognise | dynamic | `-Wno-unrecognised-pragmas`
`-Wunrecognised-warning-flags` | throw a warning when an unreconised `-W...` flag is encountered on the command line. | dynamic | `-Wno-unrecognised-warning-flags`
`-Wunsafe` | warn if the module being compiled is regarded to be unsafe. See Safe Haskell | dynamic | `-Wno-unsafe`
`-Wunsupported-calling-conventions` | warn about use of an unsupported calling convention | dynamic | `-Wno-unsupported-calling-conventions`
`-Wunsupported-llvm-version` | Warn when using `-fllvm` with an unsupported version of LLVM. | dynamic | `-Wno-monomorphism-restriction`
`-Wunticked-promoted-constructors` | warn if promoted constructors are not ticked | dynamic | `-Wno-unticked-promoted-constructors`
`-Wunused-binds` | warn about bindings that are unused. Alias for `-Wunused-top-binds`, `-Wunused-local-binds` and `-Wunused-pattern-binds` | dynamic | `-Wno-unused-binds`
`-Wunused-do-bind` | warn about do bindings that appear to throw away values of types other than `()` | dynamic | `-Wno-unused-do-bind`
`-Wunused-foralls` | warn about type variables in user-written `forall`\s that are unused | dynamic | `-Wno-unused-foralls`
`-Wunused-imports` | warn about unnecessary imports | dynamic | `-Wno-unused-imports`
`-Wunused-local-binds` | warn about local bindings that are unused | dynamic | `-Wno-unused-local-binds`
`-Wunused-matches` | warn about variables in patterns that aren’t used | dynamic | `-Wno-unused-matches`
`-Wunused-pattern-binds` | warn about pattern match bindings that are unused | dynamic | `-Wno-unused-pattern-binds`
`-Wunused-top-binds` | warn about top-level bindings that are unused | dynamic | `-Wno-unused-top-binds`
`-Wunused-type-patterns` | warn about unused type variables which arise from patterns in in type family and data family instances | dynamic | `-Wno-unused-type-patterns`
`-Wwarn` | make warnings non-fatal | dynamic | `-Werror`
`-Wwarnings-deprecations` | warn about uses of functions & types that have warnings or deprecated pragmas | dynamic | `-Wno-warnings-deprecations`
`-Wwrong-do-bind` | warn about do bindings that appear to throw away monadic values that you should have bound instead | dynamic | `-Wno-wrong-do-bind`

## 8.6.14. Optimisation levels

These options are described in more detail in Optimisation (code improvement).

See Individual optimisations for a list of optimisations enabled on level 1 and level 2.

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-O`, `-O1` | Enable level 1 optimisations | dynamic | `-O0`
`-O0` | Disable optimisations (default) | dynamic |
`-O2` | Enable level 2 optimisations | dynamic | `-O0`

## 8.6.15. Individual optimisations

These options are described in more detail in -f*: platform-independent flags. If a flag is implied by `-O` then it is also implied by `-O2` (unless flag description explicitly says otherwise). If a flag is implied by `-O0` only then the flag is not implied by `-O` and `-O2`.

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-fasm-shortcutting` | Enable shortcutting on assembly. Implied by `-O2`. | dynamic | `-fno-asm-shortcutting`
`-fblock-layout-cfg` | Use the new cfg based block layout algorithm. | dynamic | `-fno-block-layout-cfg`
`-fblock-layout-weightless` | Ignore cfg weights for code layout. | dynamic | `-fno-block-layout-weightless`
`-fblock-layout-weights` | Sets edge weights used by the new code layout algorithm. | dynamic |
`-fcall-arity` | Enable call-arity optimisation. Implied by `-O`. | dynamic | `-fno-call-arity`
`-fcase-folding` | Enable constant folding in case expressions. Implied by `-O`. | dynamic | `-fno-case-folding`
`-fcase-merge` | Enable case-merging. Implied by `-O`. | dynamic | `-fno-case-merge`
`-fcmm-elim-common-blocks` | Enable Cmm common block elimination. Implied by `-O`. | dynamic | `-fno-cmm-elim-common-blocks`
`-fcmm-sink` | Enable Cmm sinking. Implied by `-O`. | dynamic | `-fno-cmm-sink`
`-fcpr-anal` | Turn on CPR analysis in the demand analyser. Implied by `-O`. | dynamic | `-fno-cpr-anal`
`-fcross-module-specialise` | Turn on specialisation of overloaded functions imported from other modules. | dynamic | `-fno-cross-module-specialise`
`-fcse` | Enable common sub-expression elimination. Implied by `-O`. | dynamic | `-fno-cse`
`-fdicts-cheap` | Make dictionary-valued expressions seem cheap to the optimiser. | dynamic | `-fno-dicts-cheap`
`-fdicts-strict` | Make dictionaries strict | dynamic | `-fno-dicts-strict`
`-fdmd-tx-dict-sel` | Use a special demand transformer for dictionary selectors. Always enabled by default. | dynamic | `-fno-dmd-tx-dict-sel`
`-fdo-eta-reduction` | Enable eta-reduction. Implied by `-O`. | dynamic | `-fno-do-eta-reduction`
`-fdo-lambda-eta-expansion` | Enable lambda eta-expansion. Always enabled by default. | dynamic | `-fno-do-lambda-eta-expansion`
`-feager-blackholing` | Turn on eager blackholing | dynamic |
`-fenable-rewrite-rules` | Switch on all rewrite rules (including rules generated by automatic specialisation of overloaded functions). Implied by `-O`. | dynamic | `-fno-enable-rewrite-rules`
`-fexcess-precision` | Enable excess intermediate precision | dynamic | `-fno-excess-precision`
`-fexitification` | Enables exitification optimisation. Implied by `-O`. | dynamic | `-fno-exitification`
`-fexpose-all-unfoldings` | Expose all unfoldings, even for very large or recursive functions. | dynamic | `-fno-expose-all-unfoldings`
`-ffloat-in` | Turn on the float-in transformation. Implied by `-O`. | dynamic | `-fno-float-in`
`-ffull-laziness` | Turn on full laziness (floating bindings outwards). Implied by `-O`. | dynamic | `-fno-full-laziness`
`-ffun-to-thunk` | Allow worker-wrapper to convert a function closure into a thunk if the function does not use any of its arguments. Off by default. | dynamic | `-fno-fun-to-thunk`
`-fignore-asserts` | Ignore assertions in the source. Implied by `-O`. | dynamic | `-fno-ignore-asserts`
`-fignore-interface-pragmas` | Ignore pragmas in interface files. Implied by `-O0` only. | dynamic | `-fno-ignore-interface-pragmas`
`-flate-dmd-anal` | Run demand analysis again, at the end of the simplification pipeline | dynamic | `-fno-late-dmd-anal`
`-flate-specialise` | Run a late specialisation pass | dynamic | `-fno-late-specialise`
`-fliberate-case` | Turn on the liberate-case transformation. Implied by `-O2`. | dynamic | `-fno-liberate-case`
`-fliberate-case-threshold=⟨n⟩` | default: 2000. Set the size threshold for the liberate-case transformation to ⟨n⟩ | dynamic | `-fno-liberate-case-threshold`
`-fllvm-pass-vectors-in-regs` | Pass vector value in vector registers for function calls | dynamic | `-fno-llvm-pass-vectors-in-regs`
`-floopification` | Turn saturated self-recursive tail-calls into local jumps in the generated assembly. Implied by `-O`. | dynamic | `-fno-loopification`
`-fmax-inline-alloc-size=⟨n⟩` | default: 128. Set the maximum size of inline array allocations to ⟨n⟩ bytes (default: 128). | dynamic |
`-fmax-inline-memcpy-insns=⟨n⟩` | default: 32. Inline `memcpy` calls if they would generate no more than ⟨n⟩ pseudo instructions. | dynamic |
`-fmax-inline-memset-insns=⟨n⟩` | default: 32. Inline `memset` calls if they would generate no more than ⟨n⟩ pseudo instructions | dynamic |
`-fmax-simplifier-iterations=⟨n⟩` | default: 4. Set the max iterations for the simplifier. | dynamic |
`-fmax-uncovered-patterns=⟨n⟩` | default: 4. Set the maximum number of patterns to display in warnings about non-exhaustive ones. | dynamic |
`-fmax-worker-args=⟨n⟩` | default: 10. If a worker has that many arguments, none will be unpacked anymore. | dynamic |
`-fno-opt-coercion` | Turn off the coercion optimiser | dynamic |
`-fno-pre-inlining` | Turn off pre-inlining | dynamic |
`-fno-state-hack` | Turn off the state hackwhereby any lambda with a real-world state token as argument is considered to be single-entry. Hence OK to inline things inside it. | dynamic |
`-fomit-interface-pragmas` | Don’t generate interface pragmas. Implied by `-O0` only. | dynamic | `-fno-omit-interface-pragmas`
`-fomit-yields` | Omit heap checks when no allocation is being performed. | dynamic | `-fno-omit-yields`
`-foptimal-applicative-do` | Use a slower but better algorithm for ApplicativeDo | dynamic | `-fno-optimal-applicative-do`
`-fpedantic-bottoms` | Make GHC be more precise about its treatment of bottom (but see also `-fno-state-hack`). In particular, GHC will not eta-expand through a case expression. | dynamic | `-fno-pedantic-bottoms`
`-fregs-graph` | Use the graph colouring register allocator for register allocation in the native code generator. Implied by `-O2`. | dynamic | `-fno-regs-graph`
`-fregs-iterative` | Use the iterative coalescing graph colouring register allocator in the native code generator. | dynamic | `-fno-regs-iterative`
`-fsimpl-tick-factor=⟨n⟩` | default: 100. Set the percentage factor for simplifier ticks. | dynamic |
`-fsimplifier-phases=⟨n⟩` | default: 2. Set the number of phases for the simplifier. Ignored with `-O0`. | dynamic |
`-fsolve-constant-dicts` | When solving constraints, try to eagerly solve super classes using available dictionaries. | dynamic | `-fno-solve-constant-dicts`
`-fspec-constr` | Turn on the SpecConstr transformation. Implied by `-O2`. | dynamic | `-fno-spec-constr`
`-fspec-constr-count=⟨n⟩` | default: 3.* Set to ⟨n⟩ the maximum number of specialisations that will be created for any one function by the SpecConstr transformation. | dynamic | `-fno-spec-constr-count`
`-fspec-constr-keen` | Specialize a call with an explicit constructor argument, even if the argument is not scrutinised in the body of the function | dynamic | `-fno-spec-constr-keen`
`-fspec-constr-threshold=⟨n⟩` | default: 2000. Set the size threshold for the SpecConstr transformation to ⟨n⟩. | dynamic | `-fno-spec-constr-threshold`
`-fspecialise` | Turn on specialisation of overloaded functions. Implied by `-O`. | dynamic | `-fno-specialise`
`-fspecialise-aggressively` | Turn on specialisation of overloaded functions regardless of size, if unfolding is available | dynamic | `-fno-specialise-aggressively`
`-fstatic-argument-transformation` | Turn on the static argument transformation. | dynamic | `-fno-static-argument-transformation`
`-fstg-cse` | Enable common sub-expression elimination on the STG intermediate language | dynamic | `-fno-stg-cse`
`-fstg-lift-lams` | Enable late lambda lifting on the STG intermediate language. Implied by `-O2`. | dynamic | `-fno-stg-lift-lams`
`-fstg-lift-lams-known` | Allow turning known into unknown calls while performing late lambda lifting. | dynamic | `-fno-stg-lift-lams-known`
`-fstg-lift-lams-non-rec-args` | Create top-level non-recursive functions with at most <n> parameters while performing late lambda lifting. | dynamic | `-fno-stg-lift-lams-non-rec-args-any`
`-fstg-lift-lams-rec-args` | Create top-level recursive functions with at most <n> parameters while performing late lambda lifting. | dynamic | `-fno-stg-lift-lams-rec-args-any`
`-fstrictness` | Turn on strictness analysis. Implied by `-O`. Implies `-fworker-wrapper` | dynamic | `-fno-strictness`
`-fstrictness-before=⟨n⟩` | Run an additional strictness analysis before simplifier phase ⟨n⟩ | dynamic |
`-funbox-small-strict-fields` | Flatten strict constructor fields with a pointer-sized representation. Implied by `-O`. | dynamic | `-fno-unbox-small-strict-fields`
`-funbox-strict-fields` | Flatten strict constructor fields | dynamic | `-fno-unbox-strict-fields`
`-funfolding-creation-threshold=⟨n⟩` | default: 750. Tweak unfolding settings. | dynamic |
`-funfolding-dict-discount=⟨n⟩` | default: 30. Tweak unfolding settings. | dynamic |
`-funfolding-fun-discount=⟨n⟩` | default: 60. Tweak unfolding settings. | dynamic |
`-funfolding-keeness-factor=⟨n⟩` | default: 1.5. Tweak unfolding settings. | dynamic |
`-funfolding-use-threshold=⟨n⟩` | default: 60. Tweak unfolding settings. | dynamic |

## 8.6.16. Profiling options

More details in Profiling

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-fno-prof-auto` | Disables any previous `-fprof-auto`, `-fprof-auto-top`, or `-fprof-auto-exported` options. | dynamic | `-fprof-auto`
`-fno-prof-cafs` | Disables any previous `-fprof-cafs` option. | dynamic | `-fprof-cafs`
`-fno-prof-count-entries` | Do not collect entry counts | dynamic | `-fprof-count-entries`
`-fprof-auto` | Auto-add `SCC`\ s to all bindings not marked INLINE | dynamic | `-fno-prof-auto`
`-fprof-auto-calls` | Auto-add `SCC`\ s to all call sites | dynamic | `-fno-prof-auto-calls`
`-fprof-auto-exported` | Auto-add `SCC`\ s to all exported bindings not marked INLINE | dynamic | `-fno-prof-auto`
`-fprof-auto-top` | Auto-add `SCC`\ s to all top-level bindings not marked INLINE | dynamic | `-fno-prof-auto`
`-fprof-cafs` | Auto-add `SCC`\ s to all CAFs | dynamic | `-fno-prof-cafs`
`-prof` | Turn on profiling | dynamic |
`-ticky` | Turn on ticky-ticky profiling | dynamic |

## 8.6.17. Program coverage options

More details in Observing Code Coverage

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-fhpc` | Turn on Haskell program coverage instrumentation | dynamic |

## 8.6.18. C pre-processor options

More details in Options affecting the C pre-processor

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-cpp` | Run the C pre-processor on Haskell source files | dynamic |
`-D⟨symbol⟩[=⟨value⟩]` | Define a symbol in the C pre-processor | dynamic | `-U⟨symbol⟩`
`-I⟨dir⟩` | Add ⟨dir⟩ to the directory search list for `#include` files | dynamic |
`-U⟨symbol⟩` | Undefine a symbol in the C pre-processor | dynamic |

## 8.6.19. Code generation options

More details in Options affecting code generation

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-dynamic-too` | Build dynamic object files as well as static object files during compilation | dynamic |
`-fasm` | Use the native code generator | dynamic | `-fllvm`
`-fbyte-code` | Generate byte-code | dynamic |
`-fexternal-dynamic-refs` | Generate code for linking against dynamic libraries | dynamic |
`-fllvm` | Compile using the LLVM code generator | dynamic | `-fasm`
`-fno-code` | Omit code generation | dynamic |
`-fobject-code` | Generate object code | dynamic |
`-fPIC` | Generate position-independent code (where available) | dynamic |
`-fPIE` | Generate code for a position-independent executable (where available) | dynamic |
`-fwrite-interface` | Always write interface files | dynamic |

## 8.6.20. Linking options

More details in Options affecting linking

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-c` | Stop after generating object (`.o`) file | mode |
`-debug` | Use the debugging runtime | dynamic |
`-dylib-install-name ⟨path⟩` | Set the install name (via `-install_name` passed to Apple’s linker), specifying the full install path of the library file. Any libraries or executables that link with it later will pick up that path as their runtime search location for it. (Darwin/OS X only) | dynamic |
`-dynamic` | Build dynamically-linked object files and executables | dynamic |
`-dynload` | Selects one of a number of modes for finding shared libraries at runtime. | dynamic |
`-eventlog` | Enable runtime event tracing | dynamic |
`-fno-embed-manifest` | Do not embed the manifest in the executable (Windows only) | dynamic |
`-fno-gen-manifest` | Do not generate a manifest file (Windows only) | dynamic |
`-fno-shared-implib` | Don’t generate an import library for a DLL (Windows only) | dynamic |
`-framework ⟨name⟩` | On Darwin/OS X/iOS only, link in the framework ⟨name⟩. This option corresponds to the `-framework` option for Apple’s Linker. | dynamic |
`-framework-path ⟨dir⟩` | On Darwin/OS X/iOS only, add ⟨dir⟩ to the list of directories searched for frameworks. This option corresponds to the `-F` option for Apple’s Linker. | dynamic |
`-fwhole-archive-hs-libs` | When linking a binary executable, this inserts the flag `-Wl,--whole-archive` before any `-l` flags for Haskell libraries, and `-Wl,--no-whole-archive` afterwards | dynamic |
`-keep-cafs` | Do not garbage-collect CAFs (top-level expressions) at runtime | dynamic |
`-L ⟨dir⟩` | Add ⟨dir⟩ to the list of directories searched for libraries | dynamic |
`-l ⟨lib⟩` | Link in library ⟨lib⟩ | dynamic |
`-main-is ⟨thing⟩` | Set main module and function | dynamic |
`-no-hs-main` | Don’t assume this program contains `main` | dynamic |
`-no-rtsopts-suggestions` | Don’t print RTS suggestions about linking with `-rtsopts[=⟨none|some|all|ignore|ignoreAll⟩]`. | dynamic |
`-package ⟨name⟩` | Expose package ⟨pkg⟩ | dynamic |
`-pie` | Instruct the linker to produce a position-independent executable. | dynamic |
`-rdynamic` | This instructs the linker to add all symbols, not only used ones, to the dynamic symbol table. Currently Linux and Windows/MinGW32 only. This is equivalent to using `-optl -rdynamic` on Linux, and `-optl -export-all-symbols` on Windows. | dynamic |
`-rtsopts[=⟨none|some|all|ignore|ignoreAll⟩]` | Control whether the RTS behaviour can be tweaked via command-line flags and the `GHCRTS` environment variable. Using `none` means no RTS flags can be given; `some` means only a minimum of safe options can be given (the default); `all` (or no argument at all) means that all RTS flags are permitted; `ignore` means RTS flags can be given, but are treated as regular arguments and passed to the Haskell program as arguments; `ignoreAll` is the same as `ignore`, but `GHCRTS` is also ignored. `-rtsopts` does not affect `-with-rtsopts` behavior; flags passed via `-with-rtsopts` are used regardless of `-rtsopts`. | dynamic |
`-shared` | Generate a shared library (as opposed to an executable) | dynamic |
`-split-objs` | Split objects (for libraries) | dynamic |
`-split-sections` | Split sections for link-time dead-code stripping | dynamic |
`-static` | Use static Haskell libraries | dynamic |
`-staticlib` | Generate a standalone static library (as opposed to an executable). This is useful when cross compiling. The library together with all its dependencies ends up in in a single static library that can be linked against. | dynamic |
`-threaded` | Use the threaded runtime | dynamic |
`-with-rtsopts=⟨opts⟩` | Set the default RTS options to ⟨opts⟩. | dynamic |

## 8.6.21. Plugin options

More details in Compiler Plugins

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-fclear-plugins` | Clear the list of active plugins | dynamic |
`-fplugin-opt=⟨module⟩:⟨args⟩` | Give arguments to a plugin module; module must be specified with `-fplugin=⟨module⟩` | dynamic |
`-fplugin=⟨module⟩` | Load a plugin exported by a given module | dynamic |
`-hide-all-plugin-packages` | Hide all packages for plugins by default | dynamic |
`-plugin-package ⟨pkg⟩` | Expose ⟨pkg⟩ for plugins | dynamic |
`-plugin-package-id ⟨pkg-id⟩` | Expose ⟨pkg-id⟩ for plugins | dynamic |

## 8.6.22. Replacing phases

More details in Replacing the program for one or more phases

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-pgma ⟨cmd⟩` | Use ⟨cmd⟩ as the assembler | dynamic |
`-pgmc ⟨cmd⟩` | Use ⟨cmd⟩ as the C compiler | dynamic |
`-pgmdll ⟨cmd⟩` | Use ⟨cmd⟩ as the DLL generator | dynamic |
`-pgmF ⟨cmd⟩` | Use ⟨cmd⟩ as the pre-processor (with `-F` only) | dynamic |
`-pgmi ⟨cmd⟩` | Use ⟨cmd⟩ as the external interpreter command. | dynamic |
`-pgmL ⟨cmd⟩` | Use ⟨cmd⟩ as the literate pre-processor | dynamic |
`-pgml ⟨cmd⟩` | Use ⟨cmd⟩ as the linker | dynamic |
`-pgmlc ⟨cmd⟩` | Use ⟨cmd⟩ as the LLVM compiler | dynamic |
`-pgmlibtool ⟨cmd⟩` | Use ⟨cmd⟩ as the command for libtool (with `-staticlib` only). | dynamic |
`-pgmlo ⟨cmd⟩` | Use ⟨cmd⟩ as the LLVM optimiser | dynamic |
`-pgmP ⟨cmd⟩` | Use ⟨cmd⟩ as the C pre-processor (with `-cpp` only) | dynamic |
`-pgms ⟨cmd⟩` | Use ⟨cmd⟩ as the splitter | dynamic |
`-pgmwindres ⟨cmd⟩` | Use ⟨cmd⟩ as the program for embedding manifests on Windows. | dynamic |

## 8.6.23. Forcing options to particular phases

More details in Forcing options to a particular phase

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-opta ⟨option⟩` | pass ⟨option⟩ to the assembler | dynamic |
`-optc ⟨option⟩` | pass ⟨option⟩ to the C compiler | dynamic |
`-optdll ⟨option⟩` | pass ⟨option⟩ to the DLL generator | dynamic |
`-optF ⟨option⟩` | pass ⟨option⟩ to the custom pre-processor | dynamic |
`-opti ⟨option⟩` | pass ⟨option⟩ to the interpreter sub-process. | dynamic |
`-optL ⟨option⟩` | pass ⟨option⟩ to the literate pre-processor | dynamic |
`-optl ⟨option⟩` | pass ⟨option⟩ to the linker | dynamic |
`-optlc ⟨option⟩` | pass ⟨option⟩ to the LLVM compiler | dynamic |
`-optlo ⟨option⟩` | pass ⟨option⟩ to the LLVM optimiser | dynamic |
`-optP ⟨option⟩` | pass ⟨option⟩ to cpp (with `-cpp` only) | dynamic |
`-optwindres ⟨option⟩` | pass ⟨option⟩ to `windres`. | dynamic |

## 8.6.24. Platform-specific options

More details in Platform-specific Flags

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-msse2` | (x86 only) Use SSE2 for floating-point operations | dynamic |
`-msse4.2` | (x86 only) Use SSE4.2 for floating-point operations | dynamic |

## 8.6.25. Compiler debugging options

More details in Debugging the compiler

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-dcmm-lint` | C-\- pass sanity checking | dynamic |
`-dcore-lint` | Turn on internal sanity checking | dynamic |
`-ddump-asm` | Dump final assembly | dynamic |
`-ddump-asm-expanded` | Dump the result of the synthetic instruction expansion pass. | dynamic |
`-ddump-asm-liveness` | Dump assembly augmented with register liveness | dynamic |
`-ddump-asm-native` | Dump initial assembly | dynamic |
`-ddump-asm-regalloc` | Dump the result of register allocation | dynamic |
`-ddump-asm-regalloc-stages` | Dump the build/spill stages of the `-fregs-graph` register allocator. | dynamic |
`-ddump-asm-stats` | Dump statistics from the register allocator. | dynamic |
`-ddump-bcos` | Dump interpreter byte code | dynamic |
`-ddump-cfg-weights` | Dump the assumed weights of the CFG. | dynamic |
`-ddump-cmm` | Dump the final C-\- output | dynamic |
`-ddump-cmm-caf` | Dump the results of the C-\- CAF analysis pass. | dynamic |
`-ddump-cmm-cbe` | Dump the results of common block elimination | dynamic |
`-ddump-cmm-cfg` | Dump the results of the C-\- control flow optimisation pass. | dynamic |
`-ddump-cmm-cps` | Dump the results of the CPS pass | dynamic |
`-ddump-cmm-from-stg` | Dump STG-to-C-\- output | dynamic |
`-ddump-cmm-info` | Dump the results of the C-\- info table augmentation pass. | dynamic |
`-ddump-cmm-proc` | Dump the results of proc-point analysis | dynamic |
`-ddump-cmm-procmap` | Dump the results of the C-\- proc-point map pass. | dynamic |
`-ddump-cmm-raw` | Dump raw C-\- | dynamic |
`-ddump-cmm-sink` | Dump the results of the C-\- sinking pass. | dynamic |
`-ddump-cmm-sp` | Dump the results of the C-\- stack layout pass. | dynamic |
`-ddump-cmm-split` | Dump the results of the C-\- proc-point splitting pass. | dynamic |
`-ddump-cmm-switch` | Dump the results of switch lowering passes | dynamic |
`-ddump-cmm-verbose` | Show output from main C-\- pipeline passes | dynamic |
`-ddump-core-stats` | Print a one-line summary of the size of the Core program at the end of the optimisation pipeline | dynamic |
`-ddump-cse` | Dump CSE output | dynamic |
`-ddump-deriv` | Dump deriving output | dynamic |
`-ddump-ds`, `-ddump-ds-preopt` | Dump desugarer output. | dynamic |
`-ddump-ec-trace` | Trace exhaustiveness checker | dynamic |
`-ddump-file-prefix=⟨str⟩` | Set the prefix of the filenames used for debugging output. | dynamic |
`-ddump-foreign` | Dump `foreign export` stubs | dynamic |
`-ddump-hpc` | An alias for `-ddump-ticked`. | dynamic |
`-ddump-if-trace` | Trace interface files | dynamic |
`-ddump-inlinings` | Dump inlining info | dynamic |
`-ddump-json` | Dump error messages as JSON documents | dynamic |
`-ddump-llvm` | Dump LLVM intermediate code. | dynamic |
`-ddump-mod-map` | Dump the state of the module mapping database. | dynamic |
`-ddump-occur-anal` | Dump occurrence analysis output | dynamic |
`-ddump-opt-cmm` | Dump the results of C-\- to C-\- optimising passes | dynamic |
`-ddump-parsed` | Dump parse tree | dynamic |
`-ddump-parsed-ast` | Dump parser output as a syntax tree | dynamic |
`-ddump-prep` | Dump prepared core | dynamic |
`-ddump-rn` | Dump renamer output | dynamic |
`-ddump-rn-ast` | Dump renamer output as a syntax tree | dynamic |
`-ddump-rn-stats` | Renamer stats | dynamic |
`-ddump-rn-trace` | Trace renamer | dynamic |
`-ddump-rtti` | Trace runtime type inference | dynamic |
`-ddump-rule-firings` | Dump rule firing info | dynamic |
`-ddump-rule-rewrites` | Dump detailed rule firing info | dynamic |
`-ddump-rules` | Dump rewrite rules | dynamic |
`-ddump-simpl` | Dump final simplifier output | dynamic |
`-ddump-simpl-iterations` | Dump output from each simplifier iteration | dynamic |
`-ddump-simpl-stats` | Dump simplifier stats | dynamic |
`-ddump-spec` | Dump specialiser output | dynamic |
`-ddump-splices` | Dump TH spliced expressions, and what they evaluate to | dynamic |
`-ddump-stg` | Dump final STG | dynamic |
`-ddump-str-signatures` | Dump strictness signatures | dynamic |
`-ddump-stranal` | Dump strictness analyser output | dynamic |
`-ddump-tc` | Dump typechecker output | dynamic |
`-ddump-tc-ast` | Dump typechecker output as a syntax tree | dynamic |
`-ddump-tc-trace` | Trace typechecker | dynamic |
`-ddump-ticked` | Dump the code instrumented by HPC (Observing Code Coverage). | dynamic |
`-ddump-timings` | Dump per-pass timing and allocation statistics | dynamic |
`-ddump-to-file` | Dump to files instead of stdout | dynamic |
`-ddump-types` | Dump type signatures | dynamic |
`-ddump-worker-wrapper` | Dump worker-wrapper output | dynamic |
`-dfaststring-stats` | Show statistics for fast string usage when finished | dynamic |
`-dhex-word-literals` | Print values of type Word# in hexadecimal. | dynamic |
`-dinitial-unique=⟨s⟩` | Start `UniqSupply` allocation from ⟨s⟩. | dynamic |
`-dinline-check=⟨str⟩` | Dump information about inlining decisions | dynamic |
`-dno-debug-output` | Suppress unsolicited debugging output | dynamic | `-ddebug-output`
`-dppr-case-as-let` | Print single alternative case expressions as strict lets. | dynamic |
`-dppr-cols=⟨n⟩` | Set the width of debugging output. For example `-dppr-cols200` | dynamic |
`-dppr-debug` | Turn on debug printing (more verbose) | dynamic |
`-dppr-user-length` | Set the depth for printing expressions in error msgs | dynamic |
`-drule-check=⟨str⟩` | Dump information about potential rule application | dynamic |
`-dshow-passes` | Print out each pass name as it happens | dynamic |
`-dstg-lint` | STG pass sanity checking | dynamic |
`-dsuppress-all` | In dumps, suppress everything (except for uniques) that is suppressible. | dynamic |
`-dsuppress-coercions` | Suppress the printing of coercions in Core dumps to make them shorter | dynamic |
`-dsuppress-idinfo` | Suppress extended information about identifiers where they are bound | dynamic |
`-dsuppress-module-prefixes` | Suppress the printing of module qualification prefixes | dynamic |
`-dsuppress-stg-free-vars` | Suppress the printing of closure free variable lists in STG output | dynamic |
`-dsuppress-ticks` | Suppress “ticks” in the pretty-printer output. | dynamic |
`-dsuppress-timestamps` | Suppress timestamps in dumps | dynamic |
`-dsuppress-type-applications` | Suppress type applications | dynamic |
`-dsuppress-type-signatures` | Suppress type signatures | dynamic |
`-dsuppress-unfoldings` | Suppress the printing of the stable unfolding of a variable at its binding site | dynamic |
`-dsuppress-uniques` | Suppress the printing of uniques in debug output (easier to use `diff`) | dynamic |
`-dsuppress-var-kinds` | Suppress the printing of variable kinds | dynamic |
`-dth-dec-file` | Dump evaluated TH declarations into *.th.hs files | dynamic |
`-dunique-increment=⟨i⟩` | Set the increment for the generated `Unique`‘s to ⟨i⟩. | dynamic |
`-dverbose-core2core` | Show output from each core-to-core pass | dynamic |
`-dverbose-stg2stg` | Show output from each STG-to-STG pass | dynamic |
`-falignment-sanitisation` | Compile with alignment checks for all info table dereferences. | dynamic |
`-fcatch-bottoms` | Insert `error` expressions after bottoming expressions; useful when debugging the compiler. | dynamic |
`-fllvm-fill-undef-with-garbage` | Intruct LLVM to fill dead STG registers with garbage | dynamic |
`-fproc-alignment` | Align functions at given boundary. | dynamic |
`-g`, `-g⟨n⟩` | Produce DWARF debug information in compiled object files. ⟨n⟩ can be 0, 1, or 2, with higher numbers producing richer output. If ⟨n⟩ is omitted, level 2 is assumed. | dynamic |

## 8.6.26. Miscellaneous compiler options

Flag | Description | Type | Reverse
--- | --- | --- | ---
`-fexternal-interpreter` | Run interpreted code in a separate process | dynamic |
`-fglasgow-exts` | Deprecated. Enable most language extensions; see Language options for exactly which ones. | dynamic | `-fno-glasgow-exts`
`-ghcversion-file ⟨path to ghcversion.h⟩` | (GHC as a C compiler only) Use this `ghcversion.h` file | dynamic |
`-H ⟨size⟩` | Set the minimum size of the heap to ⟨size⟩ | dynamic |
`-j[⟨n⟩]` | When compiling with `--make`, compile ⟨n⟩ modules in parallel. | dynamic |