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4.18. Flag reference

This section is a quick-reference for GHC's command-line flags. For each flag, we also list its static/dynamic status (see Section 4.2), and the flag's opposite (if available).

4.18.1. Help and verbosity options (Section 4.4)

Flag	Description	Static/Dynamic	Reverse
`-?`	help	static	-
`-help`	help	static	-
`-v`	verbose mode (equivalent to `-v3`)	dynamic	-
`-vn`	set verbosity level	dynamic	-
`--version`	display GHC version	static	-
`--numeric-version`	display GHC version (numeric only)	static	-

4.18.2. Which phases to run (Section 4.6)

Flag	Description	Static/Dynamic	Reverse
`-E`	Stop after preprocessing (`.hspp` file)	static	-
`-C`	Stop after generating C (`.hc` file)	static	-
`-S`	Stop after generating assembly (`.s` file)	static	-
`-c`	Stop after compiling to object code (`.o` file)	static	-

4.18.3. Redirecting output (Section 4.7)

Flag	Description	Static/Dynamic	Reverse
`-hcsuf` `suffix`	set the suffix to use for intermediate C files	static	-
`-hidir` `dir`	set directory for interface files	static	-
`-hisuf` `suffix`	set the suffix to use for interface files	static	-
`-o` `filename`	set output filename	static	-
`-odir` `dir`	set output directory	static	-
`-ohi` `filename`	set the filename in which to put the interface	static
`-osuf` `suffix`	set the output file suffix	static	-

4.18.4. Keeping intermediate files (Section 4.7.1)

Flag	Description	Static/Dynamic	Reverse
`-keep-hc-file`	retain intermediate `.hc` files	static	-
`-keep-s-file`	retain intermediate `.s` files	static	-
`-keep-raw-s-file`	retain intermediate `.raw_s` files	static	-
`-keep-tmp-files`	retain all intermediate temporary files	static	-

4.18.5. Temporary files (Section 4.7.2)

Flag	Description	Static/Dynamic	Reverse
`-tmpdir`	set the directory for temporary files	static	-

4.18.6. Finding imports (Section 4.9.2)

Flag	Description	Static/Dynamic	Reverse
`-idir1`:`dir2`:...	add `dir`, `dir2`, etc. to import path	static	-
`-i`	Empty the import directory list	static	-

4.18.7. Interface file options (Section 4.9.3)

Flag	Description	Static/Dynamic	Reverse
`-ddump-hi`	Dump the new interface to stdout	dynamic	-
`-ddump-hi-diffs`	Show the differences vs. the old interface	dynamic	-

4.18.8. Recompilation checking (Section 4.9.4)

Flag	Description	Static/Dynamic	Reverse
`-no-recomp`	Turn off recompilation checking	static	`-recomp`

4.18.9. Interactive-mode options (Section 3.8)

Flag	Description	Static/Dynamic	Reverse
`-ignore-dot-ghci`	Disable reading of `.ghci` files	static	-
`-read-dot-ghci`	Enable reading of `.ghci` files	static	-

4.18.10. Packages (Section 4.10)

Flag	Description	Static/Dynamic	Reverse
`-package` `name`	Use package `name`	static	-
`-package-conf` `file`	Load more packages from `file`	static	-
`-package-name` `name`	Compile code for package `name`	static	-

4.18.11. Language options (Section 7.1)

Flag	Description	Static/Dynamic	Reverse
`-fallow-overlapping-instances`		dynamic	`-fno-allow-overlapping-instances`
`-fallow-undecidable-instances`	Enable undecidable instances	dynamic	`-fno-allow-undecidable-instances`
`-fgenerics`	Enable generics	dynamic	`-fno-fgenerics`
`-fglasgow-exts`	Enable most language extensions	dynamic	`-fno-glasgow-exts`
`-fignore-asserts`	Ignore assertions	dynamic	`-fno-ignore-asserts`
`-fno-implicit-prelude`	Don't implicitly `import Prelude`	dynamic	-
`-fno-monomorphism-restriction`	Disable the monomorphism restriction	dynamic	`-`
`-firrefutable-tuples`	Make tuple pattern matching irrefutable	dynamic	`-fno-irrefutable-tuples`
`-fcontext-stackn`	set the limit for context reduction	dynamic	`-`

4.18.12. Warnings (Section 4.8)

Flag	Description	Static/Dynamic	Reverse
`-W`	enable normal warnings	dynamic	`-w`
`-w`	disable all warnings	dynamic	-
`-Wall`	enable all warnings	dynamic	`-w`
`-fwarn-deprecations`	warn about uses of functions & types that are deprecated	dynamic	`-fno-warn-deprecations`
`-fwarn-duplicate-exports`	warn when an entity is exported multiple times	dynamic	`-fno-warn-duplicate-exports`
`-fwarn-hi-shadowing`	warn when a `.hi` file in the current directory shadows a library	dynamic	`-fno-warn-hi-shadowing`
`-fwarn-incomplete-patterns`	warn when a pattern match could fail	dynamic	`-fno-warn-incomplete-patterns`
`-fwarn-misc`	enable miscellaneous warnings	dynamic	`-fno-warn-misc`
`-fwarn-missing-fields`	warn when fields of a record are uninitialised	dynamic	`-fno-warn-missing-fields`
`-fwarn-missing-methods`	warn when class methods are undefined	dynamic	`-fno-warn-missing-methods`
`-fwarn-missing-signatures`	warn about top-level functions without signatures	dynamic	`-fno-warn-missing-signatures`
`-fwarn-name-shadowing`	warn when names are shadowed	dynamic	`-fno-warn-name-shadowing`
`-fwarn-overlapping-patterns`	warn about overlapping patterns	dynamic	`-fno-warn-overlapping-patterns`
`-fwarn-simple-patterns`	warn about lambda-patterns that can fail	dynamic	`-fno-warn-simple-patterns`
`-fwarn-type-defaults`	warn when defaulting happens	dynamic	`-fno-warn-type-defaults`
`-fwarn-unused-binds`	warn about bindings that are unused	dynamic	`-fno-warn-unused-binds`
`-fwarn-unused-imports`	warn about unnecessary imports	dynamic	`-fno-warn-unused-imports`
`-fwarn-unused-matches`	warn about variables in patterns that aren't used	dynamic	`-fno-warn-unused-matches`

4.18.13. Optimisation levels (Section 4.11)

Flag	Description	Static/Dynamic	Reverse
`-O`	Enable default optimisation (level 1)	static	`-O0`
`-On`	Set optimisation level `n`	static	`-O0`
`-O2-for-C`	Run gcc with `-O2`	static	-

4.18.14. Individual optimisations (Section 4.11.2)

Flag	Description	Static/Dynamic	Reverse
`-fall-strict`	Make everything strict	dynamic	`-fno-all-strict`
`-fcase-merge`	Enable case-merging	static	`-fno-case-merge`
`-fdicts-strict`	Make dictionaries strict	dynamic	`-fno-dicts-strict`
`-fdo-eta-reduction`	Enable eta-reduction	static	`-fno-do-eta-reduction`
`-fdo-lambda-eta-expansion`	Enable lambda eta-reduction	static	`-fno-do-lambda-eta-expansion`
`-fexcess-precision`	Enable excess intermediate precision	static	`-fno-excess-precision`
`-ffoldr-build-on`	Enable foldr-build optimisation	static	`-fno-foldr-build-on`
`-fignore-asserts`	Ignore assertions in the source	static	`-fno-ignore-asserts`
`-fignore-interface-pragmas`	Ignore pragmas in interface files	static	`-fno-ignore-interface-pragmas`
`-flet-no-escape`	Enable let-no-escape optimisation	static	`-fno-let-no-escape`
`-fliberate-case-threshold`	Tweak the liberate-case optimisation (default: 10)	static	`-fno-liberate-case-threshold`
`-fomit-interface-pragmas`	Don't generate interface pragmas	static	`-fno-omit-interface-pragmas`
`-fmax-worker-args`	If a worker has that many arguments, none will be unpacked anymore (default: 10)	static	-
`-fmax-simplifier-iterations`	Set the max iterations for the simplifier	static	-
`-fno-cpr`	Turn off CPR analysis	static	-
`-fno-cse`	Turn off common sub-expression	static	-
`-fno-pre-inlining`	Turn off pre-inlining	static	-
`-fno-strictness`	Turn off strictness analysis	static	-
`-fnumbers-strict`	Make numbers strict	dynamic	`-fno-numbers-strict`
`-funbox-strict-fields`	Flatten strict constructor fields	static	`-fno-unbox-strict-fields`
`-funfolding-creation-threshold`	Tweak unfolding settings	static	`-fno-unfolding-creation-threshold`
`-funfolding-fun-discount`	Tweak unfolding settings	static	`-fno-unfolding-fun-discount`
`-funfolding-keeness-factor`	Tweak unfolding settings	static	`-fno-unfolding-keeness-factor`
`-funfolding-update-in-place`	Tweak unfolding settings	static	`-fno-unfolding-update-in-place`
`-funfolding-use-threshold`	Tweak unfolding settings	static	`-fno-unfolding-use-threshold`
`-fusagesp`	Turn on UsageSP analysis	static	`-fno-usagesp`

4.18.15. Profiling options (Chapter 5)

Flag	Description	Static/Dynamic	Reverse
`-auto`	Auto-add `_scc_`s to all exported functions	static	`-no-auto`
`-auto-all`	Auto-add `_scc_`s to all top-level functions	static	`-no-auto-all`
`-auto-dicts`	Auto-add `_scc_`s to all dictionaries	static	`-no-auto-dicts`
`-caf-all`	Auto-add `_scc_`s to all CAFs	static	`-no-caf-all`
`-prof`	Turn on profiling	static	-
`-ticky`	Turn on ticky-ticky profiling	static	-

4.18.16. Parallelism options (Section 4.14)

Flag	Description	Static/Dynamic	Reverse
`-gransim`	Enable GRANSIM	static	-
`-parallel`	Enable Parallel Haskell	static	-
`-smp`	Enable SMP support	static	-

4.18.17. C pre-processor options (Section 4.12.3)

Flag	Description	Static/Dynamic	Reverse
`-cpp`	Run the C pre-processor on Haskell source files	dynamic	-
`-Dsymbol`[=`value`]	Define a symbol in the C pre-processor	dynamic	`-Usymbol`
`-Usymbol`	Undefine a symbol in the C pre-processor	dynamic	-
`-Idir`	Add `dir` to the directory search list for `#include` files	static	-

4.18.18. C compiler options (Section 4.12.4)

Flag	Description	Static/Dynamic	Reverse
`-#include` `file`	Include `file` when compiling the `.hc` file	dynamic	-

4.18.19. Code generation options (Section 4.12.5)

Flag	Description	Static/Dynamic	Reverse
`-fasm`	Use the native code generator	dynamic	-fvia-C
`-fvia-C`	Compile via C	dynamic	-fasm
`-fno-code`	Omit code generation	static	-

4.18.20. Linking options (Section 4.12.6)

Flag	Description	Static/Dynamic	Reverse
`-dynamic`	Use dynamic Haskell libraries (if available)	static	-
`-llib`	Link in library `lib`	static	-
`-Ldir`	Add `dir` to the list of directories searched for libraries	static	-
`-package` `name`	Link in package `name`	static	-
`-split-objs`	Split objects (for libraries)	static	-
`-static`	Use static Haskell libraries	static	-
`-no-hs-main`	Don't asssume this program contains `main`	static	-

4.18.21. Replacing phases (Section 4.12.1)

Flag	Description	Static/Dynamic	Reverse
`-pgmL` `cmd`	Use `cmd` as the literate pre-processor	static	-
`-pgmP` `cmd`	Use `cmd` as the C pre-processor (with `-cpp` only)	static	-
`-pgmc` `cmd`	Use `cmd` as the C compiler	static	-
`-pgma` `cmd`	Use `cmd` as the assembler	static	-
`-pgml` `cmd`	Use `cmd` as the linker	static	-
`-pgmdll` `cmd`	Use `cmd` as the DLL generator	static	-
`-pgmdep` `cmd`	Use `cmd` as the dependency generator	static	-

4.18.22. Forcing options to particular phases (Section 4.12.2)

Flag	Description	Static/Dynamic	Reverse
`-optL` `option`	pass `option` to the literate pre-processor	dynamic	-
`-optP` `option`	pass `option` to cpp (with `-cpp` only)	dynamic	-
`-optc` `option`	pass `option` to the C compiler	dynamic	-
`-opta` `option`	pass `option` to the assembler	dynamic	-
`-optl` `option`	pass `option` to the linker	static	-
`-optdll` `option`	pass `option` to the DLL generator	static	-
`-optdep` `option`	pass `option` to the dependency generator	static	-

4.18.23. Platform-specific options (Section 4.15)

Flag	Description	Static/Dynamic	Reverse
`-mv8`	(SPARC only) enable version 8 support	static	-
`-monly-[32]-regs`	(x86 only) give some registers back to the C compiler	dynamic	-

4.18.24. Compiler debugging options (Section 4.17)

Flag	Description	Static/Dynamic	Reverse
`-dcore-lint`	Turn on internal sanity checking	dynamic	-
`-ddump-absC`	Dump abstract C	dynamic	-
`-ddump-asm`	Dump assembly	dynamic	-
`-ddump-bcos`	Dump interpreter byte code	dynamic	-
`-ddump-cpranal`	Dump output from CPR analysis	dynamic	-
`-ddump-cse`	Dump CSE output	dynamic	-
`-ddump-deriv`	Dump deriving output	dynamic	-
`-ddump-ds`	Dump desugarer output	dynamic	-
`-ddump-flatC`	Dump “flat” C	dynamic	-
`-ddump-foreign`	Dump `foreign export` stubs	dynamic	-
`-ddump-inlinings`	Dump inlining info	dynamic	-
`-ddump-occur-anal`	Dump occurrence analysis output	dynamic	-
`-ddump-parsed`	Dump parse tree	dynamic	-
`-ddump-realC`	Dump “real” C	dynamic	-
`-ddump-rn`	Dump renamer output	dynamic	-
`-ddump-rules`	Dump rules	dynamic	-
`-ddump-sat`	Dump saturated output	dynamic	-
`-ddump-simpl`	Dump final simplifier output	dynamic	-
`-ddump-simpl-iterations`	Dump output from each simplifier iteration	dynamic	-
`-ddump-spec`	Dump specialiser output	dynamic	-
`-ddump-stg`	Dump final STG	dynamic	-
`-ddump-stranal`	Dump strictness analyser output	dynamic	-
`-ddump-tc`	Dump typechecker output	dynamic	-
`-ddump-types`	Dump type signatures	dynamic	-
`-ddump-usagesp`	Dump UsageSP analysis output	dynamic	-
`-ddump-worker-wrapper`	Dump worker-wrapper output	dynamic	-
`-ddump-rn-trace`	Trace renamer	dynamic	-
`-ddump-rn-stats`	Renamer stats	dynamic	-
`-ddump-stix`	Native code generator intermediate form	dynamic	-
`-ddump-simpl-stats`	Dump simplifier stats	dynamic	-
`-dppr-debug`	Turn on debug printing (more verbose)	static	-
`-dppr-noprags`	Don't output pragma info in dumps	static	-
`-dppr-user-length`	Set the depth for printing expressions in error msgs	static	-
`-dsource-stats`	Dump haskell source stats	dynamic	-
`-dstg-lint`	STG pass sanity checking	dynamic	-
`-dstg-stats`	Dump STG stats	dynamic	-
`-dusagesp-lint`	UsageSP sanity checker	dynamic	-
`-dverbose-core2core`	Show output from each core-to-core pass	dynamic	-
`-dverbose-stg2stg`	Show output from each STG-to-STG pass	dynamic	-
`-unreg`	Enable unregisterised compilation	static	-

4.18.25. Misc compiler options

Flag	Description	Static/Dynamic	Reverse
`-funfold-casms-in-hi-file`	Allow casms in unfoldings	static	-
`-femit-extern-decls`	???	static	-
`-fglobalise-toplev-names`	Make all top-level names global (for `-split-objs`)	static	-
`-fno-hi-version-check`	Don't complain about `.hi` file mismatches	static	-
`-dno-black-holing`	Turn off black holing (probably doesn't work)	static	-
`-fno-method-sharing`	Don't share specialisations of overloaded functions	static	-
`-fno-prune-decls`	Renamer: don't prune declarations	static	-
`-fno-prune-tydecls`	Renamer: don't prune type declarations	static	-
`-fhistory-size`	Set simplification history size	static	-
`-funregisterised`	Unregisterised compilation (use `-unreg` instead)	static	-
`-fno-asm-mangling`	Turn off assembly mangling (use `-unreg` instead)	static	-