[Haskell-beginners] using Shake to compile c++

[David McBride]

Sorry that should have been command, not command_ which is very different.

On Sat, Jul 8, 2017 at 7:37 AM, David McBride <toad3k at gmail.com> wrote:
> The easy option is to just use command instead of cmd.  Variadic
> functions are always a little weird to type check.
>
> command_ [] "pkg-config" ["glib-2.0","--cflags"]
>
> That will *probably* solve the ambiguity in both lines, but I haven't tested.
>
> On Sat, Jul 8, 2017 at 7:19 AM, Roger Mason <rmason at mun.ca> wrote:
>> Hello,
>>
>> I am trying the Shake build system to compile some c++.  I would
>> appreciate some advice on how to use the result of a call to pkg-config
>> in constructing a compiler command.  This is what I have currently in Build.hs:
>>
>> import Development.Shake
>> import Development.Shake.Command
>> import Development.Shake.FilePath
>> import Development.Shake.Util
>>
>> main :: IO ()
>> main = shakeArgs shakeOptions{shakeFiles="bin"} $ do
>>     want ["bin/makelist", "bin/makejpeg" <.> exe]
>>
>>     phony "clean" $ do
>>         putNormal "Cleaning files in _build"
>>         removeFilesAfter "bin" ["//*"]
>>
>>     "bin/makelist" <.> exe %> \out -> do
>>         cs <- getDirectoryFiles "" ["src/MakeList.cxx"]
>>         let os = ["objects" </> c -<.> "o" | c <- cs]
>>         need os
>>         cmd "c++ -o" [out] os
>>
>>     "bin/makejpeg" <.> exe %> \out -> do
>>         cs <- getDirectoryFiles "" ["src/MakeJpeg.cxx"]
>>         let os = ["objects" </> c -<.> "o" | c <- cs]
>>         need os
>>         cmd "c++ -o" [out] os
>>
>>     "objects//*.o" %> \out -> do
>>         let c = dropDirectory1 $ out -<.> "cxx"
>>         let m = out -<.> "m"
>>         let i = cmd "pkg-config glib-2.0 --cflags"
>>         () <- cmd "c++ -c" [c] "-o" [out] "-MMD -MF" [m] [i]
>>         needMakefileDependencies m
>>
>> This is the output from 'stack runhaskell Build.sh':
>>
>> Build.hs:29:17: error:
>>     * Ambiguous type variable `t0' arising from a use of `cmd'
>>       prevents the constraint `(CmdArguments t0)' from being solved.
>>       Relevant bindings include i :: t0 (bound at Build.hs:29:13)
>>       Probable fix: use a type annotation to specify what `t0' should be.
>>       These potential instances exist:
>>         instance CmdResult r => CmdArguments (IO r)
>>           -- Defined in `Development.Shake.Command'
>>         instance CmdResult r => CmdArguments (Action r)
>>           -- Defined in `Development.Shake.Command'
>>         instance (Development.Shake.Command.Arg a, CmdArguments r) =>
>>                  CmdArguments (a -> r)
>>           -- Defined in `Development.Shake.Command'
>>         ...plus one other
>>         (use -fprint-potential-instances to see them all)
>>     * In the expression: cmd "pkg-config glib-2.0 --cflags"
>>       In an equation for `i': i = cmd "pkg-config glib-2.0 --cflags"
>>       In the expression:
>>         do { let c = dropDirectory1 $ out -<.> "cxx";
>>              let m = out -<.> "m";
>>              let i = cmd "pkg-config glib-2.0 --cflags";
>>              () <- cmd "c++ -c" [c] "-o" [out] "-MMD -MF" [m] [i];
>>              .... }
>>
>> Build.hs:30:15: error:
>>     * Ambiguous type variable `t0' arising from a use of `cmd'
>>       prevents the constraint `(Development.Shake.Command.Arg
>>                                   [t0])' from being solved.
>>       Relevant bindings include i :: t0 (bound at Build.hs:29:13)
>>       Probable fix: use a type annotation to specify what `t0' should be.
>>       These potential instances exist:
>>         instance Development.Shake.Command.Arg [CmdOption]
>>           -- Defined in `Development.Shake.Command'
>>         instance Development.Shake.Command.Arg [String]
>>           -- Defined in `Development.Shake.Command'
>>         instance Development.Shake.Command.Arg String
>>           -- Defined in `Development.Shake.Command'
>>     * In a stmt of a 'do' block:
>>         () <- cmd "c++ -c" [c] "-o" [out] "-MMD -MF" [m] [i]
>>       In the expression:
>>         do { let c = dropDirectory1 $ out -<.> "cxx";
>>              let m = out -<.> "m";
>>              let i = cmd "pkg-config glib-2.0 --cflags";
>>              () <- cmd "c++ -c" [c] "-o" [out] "-MMD -MF" [m] [i];
>>              .... }
>>       In the second argument of `(%>)', namely
>>         `\ out
>>            -> do { let ...;
>>                    let ...;
>>                    .... }'
>>
>> I would appreciate any help in getting the output of the call to
>> pkg-config into the compiler invocation.
>>
>> Thanks,
>> Roger
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