I have a haskell project which I compile with -Werror by default. This means that when I run cabal repl it runs with the option -Werror turned on. This means that for example when I evaluate 2 + 2 I get the following error message:
<interactive>:2:3: Warning:
Defaulting the following constraint(s) to type `Integer'
(Num a0) arising from a use of `+'
In the expression: 2 + 2
In an equation for `it': it = 2 + 2
So I need a way to turn on the option, -w or maybe -Wwarn on by default for cabal repl. How do I do this? Also what are the default flags for ghci?
You can set GHCi options in your ~/.ghci file:
:set -w
This overrides the -Wall from cabal repl for me.
My understanding is that ghci has the same defaults a ghc: it's like calling the compiler with no flags. cabal repl gets its defaults from your .cabal file (like ghc-options: -Wall), but this is overridden by your ~/.ghci file.
You can also create a .ghci file in your project directory, with per-project settings there. However, this seems to interact awkwardly with my global ~/.ghci file: adding a set -Wall does not override the :set -w from the global one. I'm not sure if this behavior is intended or I'm just misunderstanding something.
Related
I have a .ghci in my local project directory, and another one in my $HOME. When I do a stack ghci, then $HOME/.ghci is loaded first, followed by $PWD/.ghci. Is it possible to have ONLY the local .ghci be loaded, and the global one ignored?
I could do a stack exec -- ghci -ignore-dot-ghci, but then, none is loaded.
What I also tried is:
stack exec -- ghci -ignore-dot-ghci -W .ghci
The idea being to first tell ghci not to load anything and then explicitly requesting the local .ghci file, but this gives the error message Warning: ignoring unrecognised input `.ghci'
GHCi has a -ghci-script flag which can be used alongside -ignore-dot-ghci. It can be used with stack ghci through --ghci-options:
stack ghci --ghci-options "-ignore-dot-ghci -ghci-script .ghci"
For the sake of completeness, here is the corresponding cabal repl invocation:
cabal repl --repl-options "-ignore-dot-ghci" --repl-options "-ghci-script .ghci"
I have a project which exports a shared static library and I use the following part in my project.cabal file
executable libsxp.so
main-is: Somefile.hs
default-language: Haskell2010
ghc-options: -shared -dynamic -fPIC -lHSrts-ghc7.10.2
The version of GHC is controlled using Stack, so is there a way wherein I can either get and append the version to make -lHSrts-ghc{version} or is there some config for it? I tried setting
stack build --ghc-options='-O0 -lHSrts-ghc7.10.2'
but it doesn't seem to pick it.
Also to clarify, cabal install is called by Stack and not by me.
Does that cabal file work? If so, then it should be sufficient to do something like this:
executable libsxp.so
ghc-options: -shared -dynamic -fPIC
if impl (ghc >= 7.10.2 && < 7.10.3)
ghc-options: -lHSrts-ghc7.10.2
else if impl (ghc >= 7.10.3 && < 7.10.4)
ghc-options: -lHSrts-ghc7.10.3
else if ...
BTW, why does your executable end in .so? I've never seen that in an executable clause.
Are you sure you're using 7.10.2 and not 7.10.3? Try stack exec -- ghc --version
The general principle is described in this answer: https://stackoverflow.com/a/6034881/1663197
Using the configure style in Cabal, you can write a little configure
script that substitutes a variable for the output of the sdl-config
command. The values will then be replaced in a $foo.buildinfo.in file,
yielding a $foo.buildinfo file, that Cabal will include in the build
process.
First you need to switch your cabal build-type to Configure in project.cabal. Configure style is described in cabal users guide. For build type Configure the contents of Setup.hs must be:
import Distribution.Simple
main = defaultMainWithHooks autoconfUserHooks
In case of handling GHC runtime version you can have a variable #GHC_VERSION# corresponding to it in a project.buildinfo.in file:
ghc-options: -lHSrts-ghc#GHC_VERSION#
Finally you write a configure bash script that gets GHC version as mgsloan suggested and generates project.buildinfo file by substitution of #GHC_VERSION# varibale in project.buildinfo.in file:
GHC_VERSION=$(stack exec -- ghc-pkg field ghc version --simple-output)
sed 's,#GHC_VERSION#,'"$GHC_VERSION"',' project.buildinfo.in > project.buildinfo
This way when build is started it will first execute configure script, then read project.buildinfo file and merge with project.cabal.
Also it may be worth to populate extra-source-files with configure and
project.buildinfo.in; extra-tmp-files with project.buildinfo in project.cabal.
A more sophisticated solution may be inspired by this answer: https://stackoverflow.com/a/2940799/1663197
I am writing a module that relies on optimization. I want to test this module in ghci. But starting ghc in --interactive mode automatically disables optimization; if I compile the module with -O and then try to load it in an interactive session, ghc insists on loading it in interpreted mode.
For a simple test case to distinguish optimized and unoptimized modules, isOptimized below evaluates to True with optimization on, but False with optimization off:
isOptimized :: Bool
isOptimized = g
g :: Bool
g = False
{-# NOINLINE g #-}
{-# RULES "g/True" g = True #-}
Either use ghci -fobject-code -O Test.hs or cabal repl --ghc-options="-fobject-code -O". In more detail:
ghci must be invoked with the -fobject-code flag.
Optimization flag(s) must be given after -fobject-code on the command line, or in an OPTIONS_GHC pragma at the top of the module. Trying ghc --interactive -O -fobject-code produces a warning that "-O conflicts with --interactive; -O ignored." This is perhaps a bug.
If you're working on a cabalized project and using cabal repl, you need to pass the flags either on the command line (i.e. cabal repl --ghc-options="-fobject-code -O") or in a pragma. Cabal (currently) discards optimization flags set in the .cabal file with ghc-options when invoking ghci; in fact, it explicitly sets -O0 instead. This is perhaps a bug.
Note in any case that you sometimes need to force recompilation manually when switching between optimized and unoptimized mode. Build artifacts are, for some reason, not invalidated when the optimization flags change so long as -fobject-code remains on. If, starting from a clean slate, you have -fobject-code set in your .cabal file, run cabal repl which compiles the module, and then remember you need to set -O on the command line and run cabal repl --ghc-options=-O, ghc will happily load the previously-compiled, unoptimized module. This is also perhaps a bug.
The most reliable scenario for testing a single module seems to be to put {-# OPTIONS_GHC -fobject-code -O #-} at the top of the module. You will get optimized code no matter how you invoke ghci. I haven't investigated what happens in multi-module situations where some but not all modules have the pragma.
Incidentally, note that only code in the module is optimized. Even with optimization on, evaluating g in the repl will always produce False, because the repl input is not subject to rewrite rules.
I have a module which binds to a C function using the FFI. How can I make this module use doctest?
The error I get when running doctest Foo.hs is something like this:
ByteCodeLink: can't find label
During interactive linking, GHCi couldn't find the following symbol:
bar
This may be due to you not asking GHCi to load extra object files,
archives or DLLs needed by your current session. Restart GHCi, specifying
the missing library using the -L/path/to/object/dir and -lmissinglibname
flags, or simply by naming the relevant files on the GHCi command line.
Alternatively, this link failure might indicate a bug in GHCi.
If you suspect the latter, please send a bug report to:
glasgow-haskell-bugs#haskell.org
### Failure in Foo.hs:41: expression `foo'
expected: [42]
but got:
<interactive>:24:1: Not in scope: `bar'
Examples: 2 Tried: 2 Errors: 0 Failures: 1
Doctest accepts arbitrary GHC flags. If you want to run Doctest with FFI code you need to pass the exact same flags that you would need to run a GHCi session with that code. Have e.g. a look at the Doctest driver of unix-time.
after install hugs and then install ghc6 then install generic-haskell has the following message, How to do?
# make package
Creating generic-haskell package ...
ghc-pkg: cannot find package generic-haskell
Reading package info from "generic-haskell.cabal.pkg" ... done.
generic-haskell-1.80: missing id field
generic-haskell-1.80: dependency "base-4.2.0.0" doesn't exist (use --force to override)
generic-haskell-1.80: dependency "haskell98-1.0.1.1" doesn't exist (use --force to override)
generic-haskell-1.80: dependency "containers-0.3.0.0" doesn't exist (use --force to override)
make: *** [package] Error 1
in ubuntu i compile ghc-6.2.2 got the following error
/usr/bin/ghc -M -optdep-f -optdep.depend -osuf o -H16m -O HaskTags.hs
on the commandline:
Warning: -optdep-f is deprecated: Use -dep-makefile instead
------------------------------------------------------------------------
==fptools== make boot - --no-print-directory -r;
in /home/martin/ghc-6.2.2/ghc/utils/ghc-pkg
------------------------------------------------------------------------
/usr/bin/ghc -M -optdep-f -optdep.depend -osuf o -H16m -O -cpp -DPKG_TOOL -DWANT_PRETTY Main.hs Package.hs ParsePkgConfLite.hs Version.hs
on the commandline:
Warning: -optdep-f is deprecated: Use -dep-makefile instead
make all
/usr/bin/ghc -H16m -O -cpp -DPKG_TOOL -DWANT_PRETTY -c Main.hs -o Main.o -ohi Main.hi
Main.hs:496:11:
Ambiguous type variable `e' in the constraint:
`Exception.Exception e'
arising from a use of `Exception.throw' at Main.hs:496:11-25
Possible cause: the monomorphism restriction applied to the following:
my_catch :: forall a. IO a -> (e -> IO a) -> IO a
(bound at Main.hs:499:0)
my_throw :: forall a. e -> a (bound at Main.hs:496:0)
Probable fix: give these definition(s) an explicit type signature
or use -XNoMonomorphismRestriction
Main.hs:498:13:
Ambiguous type variable `e1' in the constraint:
`Exception.Exception e1'
arising from a use of `Exception.catch' at Main.hs:498:13-27
Possible cause: the monomorphism restriction applied to the following:
eval_catch :: forall a. a -> (e1 -> IO a) -> IO a
(bound at Main.hs:498:0)
Probable fix: give these definition(s) an explicit type signature
or use -XNoMonomorphismRestriction
make[4]: *** [Main.o] Error 1
make[3]: *** [boot] Error 2
make[2]: *** [boot] Error 1
make[1]: *** [boot] Error 1
Any one have installed old version of GHC and generic haskell in ubuntu 10?
There are many pairs of version , i tried ghc-6.2.2 got above error, will i need to uninstall ubuntu 10 to install older version ubuntu to get it work? which version of ubuntu for which version of ghc work?
http://www.cs.uu.nl/research/projects/generic-haskell/compiler.html
I tried installing generic-haskell myself from the source, I managed, and am able to describe how I fixed it. My installation platform is the Haskell Platform 2011.2.0.1-x86_64, but the following instruction are somewhat more general.
I met three problems, including the first one you describe (no. 3 below). For other users, I also describe the first two ones, which you probably solved as well.
1) Other users have first to fix an error depending on Data.Map.lookup type having changed, for containers >= 0.2.0.0: it used to return Monad m => m b (in containers-1.0.0.0), now it returns just Maybe b.
I added calls to Data.Maybe.maybeToList to fix a few call-sites needing to use a list type; I bet you fixed the same error in some way. You can find this fix at:
http://hpaste.org/47624.
2) Another error I had, with GHC 7, is that the configure script does not realize that it is newer than GHC 6.8, so it needs to also depend on containers. configure output included this line:
checking whether base package is split (GHC 6.8 or newer)... no
To fix this, you need to replace
if test $ghc_ma -ge 6 -a $ghc_mi -ge 8; then
with
if test $ghc_ma -eq 6 -a $ghc_mi -ge 8 -o $ghc_ma -ge 7; then
3) To fix your problem, you need to edit build/generic-haskell.cabal.pkg (assuming you are not doing an in-place installation with make in-place). You need to add an id: line and fix the depends line to use package-ids of packages present on your systems instead of package names. You can find out the ids using the following commands (output on my system included):
$ ghc-pkg field base id
id: base-4.3.1.0-f5c465200a37a65ca26c5c6c600f6c76
$ ghc-pkg field haskell98 id
id: haskell98-1.1.0.1-150131ea75216886448a7146c9e0526b
$ ghc-pkg field containers id
id: containers-0.4.0.0-b4885363abca642443ccd842502a3b7e
The change to build/generic-haskell.cabal.pkg would then be:
-depends: base-4.3.1.0
- haskell98-1.1.0.1
- containers-0.4.0.0
+depends: base-4.3.1.0-f5c465200a37a65ca26c5c6c600f6c76
+ haskell98-1.1.0.1-150131ea75216886448a7146c9e0526b
+ containers-0.4.0.0-b4885363abca642443ccd842502a3b7e
Furthermore, you need to add an id line to the same file - any id will do, as long as you change it if/when you reinstall the library. Here I've used:
id: generic-haskell-1.80-lib-md5sum-2a7ae9d60440627618ad0b0139ef090b
I've also aligned all fields with spaces, as in the existing files. The syntax reference for this file can be found in:
http://www.haskell.org/ghc/docs/6.12.2/html/users_guide/packages.html#installed-pkg-info
Apparently, the generic-haskell package depends on an old version of base.
The Haskell Platform specifies base-4.3.1.0, while generic-haskell needs an older version. Please contact the maintainers, or possibly, install an older version of GHC.