Foreign.C.Types in haskell2010

According to Haskell 2010, a marshallable foreign type has to be a newtype of a basic type with exposed constructor. Why constructors are not exposed in the module Foreign.C.Types from haskell2010? When I replace base with haskell2010 in

module Test where

import Foreign.C

foreign import ccall unsafe "sys/mount.h umount" umount :: CString -> IO CInt

I get

Unacceptable result type in foreign declaration: IO CInt
When checking declaration:
  foreign import ccall unsafe "static sys/mount.h umount" umount
    :: CString -> IO CInt

Trac metadata

Trac field	Value
Version	7.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	libraries/haskell2010
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

changed weight to 5

added Tbug Trac import core libraries labels

closed

Interesting. Foreign.C.Types does export CInt(..). And compiling the module you show works just fine for me:

bash$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.8.2

bash$ ghc -c T9079.hs -fforce-recomp
bash$ cat T9079.hs
module T9079 where

import Foreign.C

foreign import ccall unsafe "sys/mount.h umount" umount :: CString -> IO CInt

Perhaps you aren't using 7.8.2? I'll close as "worksforme" but if you disagree then please do re-open with more details.

Simon

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedWorksForMe
CC	→ core-libraries-committee@haskell.org

I'm talking about compiling using haskell2010:

ghc -package haskell2010 -hide-package base Test.hs

As I see from this source the constructors for C types are not exposed.

reopened

Trac metadata

Trac field	Value
Resolution	ResolvedWorksForMe → Unresolved

I believe this is related to the breaking change that went into GHC 7.6.1:

Warning: newtype `CInt' is used in an FFI declaration,
         but its constructor is not in scope.
         This will become an error in GHC 7.6.1.

Well, this looks to me like a bug in the Haskell 2010 report

• Section 8.4.2 says that newtypes must have their constructors visible, and claims that Foreign.C.Types follows this convention.
• But Chapter 28 which shows Foreign.C.Types manifestly does not follow this convention.

That looks like an outright contradiction.

I think we should export all the data constructors in Foreign.C.Types in the haskell2010 package. Does anyone disagree?

Meanwhile, I'm adding Simon M to the cc list, as editor of the H2010 report.

Autin: could you act on this after a suitable delay?

Simon

assigned to @trac-ekmett

Moving over to new owning component 'Core Libraries'.

Trac metadata

Trac field	Value
Component	libraries/haskell2010 → Core Libraries

We've dropped core library support for the haskell2010 package, due to #9590 (closed), but this still seems actionable.

Herbert has been exploring ways to get users who really want it a fully compliant haskell2010 package, and this unfortunate contradiction seems like it'd still impact his efforts on that front.

See also #PRIME156

Trac metadata

Trac field	Value
CC	core-libraries-committee@haskell.org → core-libraries-committee@haskell.org, ekmett

https://prime.haskell.org/ticket/156

(since the Gitlab migration didn't handle PRIME issue links)

added Pnormal label