Odd c2hs error

[mitchellwrosen]

I've put together a repo that reproduces what I thought was a language-c bug, but cabal is behaving oddly as well.

The repo:

https://github.com/mitchellwrosen/language-c-issue-54

To reproduce:

• Run ./build once:

Resolving dependencies...
Build profile: -w ghc-8.4.3 -O1
In order, the following will be built (use -v for more details):
 - foo-0 (lib:foo) (first run)
Configuring foo-0...
Preprocessing library for foo-0..
c2hs: Errors during generation of C wrappers:

./Foo.chs:9: (column 4) [ERROR]  >>> Internal wrapper error!
  Something went wrong generating a bare structure wrapper.
  makeArg:arg=False
  cdecl=CDecl [CTypeSpec (CTypeDef (Ident "WINDOW" 143904934 (NodeInfo ("./foo.h": line 1635) (("./foo.h": line 1635),6) (Name {nameId = 4053}))) (NodeInfo ("./foo.h": line 1635) (("./foo.h": line 1635),6) (Name {nameId = 4054})))] [(Just (CDeclr Nothing [CPtrDeclr [] (NodeInfo ("./foo.h": line 1635) (("./foo.h": line 1635),1) (Name {nameId = 4055}))] Nothing [] (OnlyPos <no file> (<no file>,-1))),Nothing,Nothing)] (NodeInfo ("./foo.h": line 1635) (("./foo.h": line 1635),1) (Name {nameId = 4056}))
  idx=1

• Run ./build again:

Build profile: -w ghc-8.4.3 -O1
In order, the following will be built (use -v for more details):
 - foo-0 (lib:foo) (first run)
Preprocessing library for foo-0..
Building library for foo-0..
[1 of 1] Compiling Foo              ( /home/mitchell/junk/dist-newstyle/build/x86_64-linux/ghc-8.4.3/foo-0/build/Foo.hs, /home/mitchell/junk/dist-newstyle/build/x86_64-linux/ghc-8.4.3/foo-0/build/Foo.o )
ignoring (possibly broken) abi-depends field for packages

For some reason, c2hs barfs the first time, then stops complaining. The generated file looks fine to me, even after only one invocation of ./build:

$ cat $(find dist-newstyle -name Foo.hs)

-- GENERATED by C->Haskell Compiler, version 0.28.3 Switcheroo, 25 November 2017 (Haskell)
-- Edit the ORIGNAL .chs file instead!


{-# LINE 1 "./Foo.chs" #-}
{-# language ForeignFunctionInterface #-}

module Foo where
import qualified Foreign.C.Types as C2HSImp
import qualified Foreign.Marshal.Utils as C2HSImp
import qualified Foreign.Ptr as C2HSImp





type Window = C2HSImp.Ptr (())
{-# LINE 7 "./Foo.chs" #-}


keypad :: (Window) -> (Bool) -> IO ((Int))
keypad a1 a2 =
  let {a1' = id a1} in 
  let {a2' = C2HSImp.fromBool a2} in 
  keypad'_ a1' a2' >>= \res ->
  let {res' = fromIntegral res} in
  return (res')

{-# LINE 9 "./Foo.chs" #-}


foreign import ccall safe "Foo.chs.h __c2hs_wrapped__keypad"
  keypad'_ :: ((Window) -> (C2HSImp.CInt{-bool-} -> (IO C2HSImp.CInt)))

Sorry for the mess of info, I'm not too sure what's going on here :) Thanks.

[vmchale]

I've run into a similar issue. After c2hs invocation fails once, cabal tries to use the generated .hs file anyhow, and then fails to find it, viz.

vanessa@vanessa-desktop ~/programming/haskell/done/lzlib 🌸 cabal build
Resolving dependencies...
Build profile: -w ghc-8.6.5 -O1
In order, the following will be built (use -v for more details):
 - lzlib-0.2.0.2 (lib) (first run)
Configuring library for lzlib-0.2.0.2..
Preprocessing library for lzlib-0.2.0.2..
c2hs: C header contains errors:

cbits/lzlib.h:59: (column 23) [ERROR]  >>> Syntax error !
  The symbol `uint8_t' does not fit here.

vanessa@vanessa-desktop ~/programming/haskell/done/lzlib 🌸 cabal build
Build profile: -w ghc-8.6.5 -O1
In order, the following will be built (use -v for more details):
 - lzlib-0.2.0.2 (lib) (first run)
Preprocessing library for lzlib-0.2.0.2..
Building library for lzlib-0.2.0.2..

<no location info>: error:
    module ‘Codec.Lzip.Raw’ cannot be found locally

There's a branch that can be used to reproduce it: https://github.com/vmchale/lzlib/tree/cabal-bug