[Haskell-cafe] zlib build failure on recent GHC

[Jason Dagit]

On Mon, Nov 7, 2011 at 8:17 AM, Johan Tibell <johan.tibell at gmail.com> wrote:
> On Mon, Nov 7, 2011 at 7:53 AM, Ben Gamari <bgamari.foss at gmail.com> wrote:
>>
>> With GHC 1ece7b27a11c6947f0ae3a11703e22b7065a6b6c zlib fails to build,
>> apparently due to Safe Haskell (bug 5610 [1]). The error is specifically,
>>
>> $ cabal install zlib
>> Resolving dependencies...
>> Configuring zlib-0.5.3.1...
>> Preprocessing library zlib-0.5.3.1...
>> Building zlib-0.5.3.1...
>> [1 of 5] Compiling Codec.Compression.Zlib.Stream (
>> dist/build/Codec/Compression/Zlib/Stream.hs,
>> dist/build/Codec/Compression/Zlib/Stream.o )
>>
>> Codec/Compression/Zlib/Stream.hsc:857:1:
>>    Unacceptable argument type in foreign declaration: CInt
>>    When checking declaration:
>>      foreign import ccall unsafe "static zlib.h inflateInit2_"
>> c_inflateInit2_
>>        :: StreamState -> CInt -> Ptr CChar -> CInt -> IO CInt
>>
>> Codec/Compression/Zlib/Stream.hsc:857:1:
>>    Unacceptable argument type in foreign declaration: CInt
>>    When checking declaration:
>>      foreign import ccall unsafe "static zlib.h inflateInit2_"
>> c_inflateInit2_
>>        :: StreamState -> CInt -> Ptr CChar -> CInt -> IO CInt
>>
>> Codec/Compression/Zlib/Stream.hsc:857:1:
>>    Unacceptable result type in foreign declaration: IO CInt
>>    Safe Haskell is on, all FFI imports must be in the IO monad
>>    When checking declaration:
>>      foreign import ccall unsafe "static zlib.h inflateInit2_"
>> c_inflateInit2_
>>        :: StreamState -> CInt -> Ptr CChar -> CInt -> IO CInt
>> ...
>>
>> This is a little strange since,
>>
>>  a) It's not clear why Safe Haskell is enabled
>>  b) The declarations in question seem to be valid
>>
>> Does this seem like a compiler issue to you?
>
> This is due to a change in how FFI imports and newtypes work. GHC was
> recently changed to not allow you to use newtypes in FFI imports unless the
> constructor of the newtype is in scope. This broke quite a few libraries. I
> have patched a few of them and I've sent a patch to the zlib maintainer.

This seems like a big change.  Where should I be watching to know
about this ahead of time?  I bet I have to fix some of my packages.

Thanks,
Jason