This seems like a bug, you shouldn't need to link to libpthread at all on Mac. /usr/lib/libpthread.dylib is just a symlink to libSystem… Not sure how to get around the issue without rebuilding GHC, it looks like iOS is special cased in the compiler (OSiOS) but not Mac OS X (OSDarwin) [1]. 

[1] https://github.com/ghc/ghc/blob/master/compiler/main/DriverPipeline.hs#L1869-L1873

On Mon, Jun 9, 2014 at 11:36 AM, Frode Nerbråten <frode@nerbraten.no> wrote:

Hi,

I'm having trouble building my Haskell library with GHC 7.8.2 and
Cabal 1.20.0.2 on OSX 10.9.3 with both -staticlib and -threaded
enabled.

The library I'm building exports several functions using FFI to be
called from ObjectiveC in an Xcode project. This works fine with just
-staticlib enabled, but now I realize I need to call into my Haskell
library from multiple OS-threads simultaneously. But when I add
-threaded to ghc-options I get an error when linking:

    error: libtool: can't locate file for: -lpthread
    error: libtool: file: -lpthread is not an object file (not allowed
in a library)

The linker command that fails looks like this (... replaces a bunch of
-l and -L options):

    libtool -static -o liba.a dist/build/HsCocoa.o ... -lCffi -lpthread

In /usr/lib I have a libpthread.dylib that links to libSystem.dylib,
but no libpthread.a. I was under the impression that libpthread was
included with the system install.

Is this supposed to work or am I misunderstanding something basic? :)
Any help would be greatly appreciated!

The project source is available on github:
https://github.com/froden/digipostarkiv
(I asked the same question on stackoverflow:
http://stackoverflow.com/q/24096257/777411)

Best regards,
Frode Nerbråten
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