Haskell, GHC, win32, cairo

Question

I have problem with ghci+cairo on windows. When I try to load, for example like this "ghci -package cairo" it fails with the following error:

Loading package random-1.0.0.2 ... linking ... done.
Loading package haskell98 ... linking ... done.
Loading package syb-0.1.0.2 ... linking ... done.
Loading package base-3.0.3.2 ... linking ... done.
Loading package mtl-1.1.0.2 ... linking ... done.
: C:\Users\alexeys\AppData\Roaming\cabal\cairo-0.12.0\ghc-6.12.3\HScairo-0.12.0.o: unknown symbol `_cairo_surface_destroy'
Loading package cairo-0.12.0 ... linking ... : unable to load package `cairo-0.12.0'

Even simplest programs don't work in interactive mode, like for example 'Text.hs' that comes with cairo package. However compiled with 'ghc --make' everything works as expected, so its not a "missing dll" problem - everything is in place.

I used 'filemon' to look what "ghci" loads and in the log I can see 'libcairo-2.dll' (and this library has '_cairo_surface_destroy' symbol defined) being found and loaded successfully, so I don't really understand - what more does it wants?

Maybe it as a 'threading' problem? There was a recent Haskell-cafe thread about the SOE graphics library exhibiting similar behaviour "Code from Haskell School of Expression Hanging" - haskell.org/pipermail/haskell-cafe/2011-January/088697.html. I'm sorry I don't know the resolution. — stephen tetley
By any chance is libcairo-2.dll in a location with spaces in the pathname? Also could you please post which version of ghci you're using (this looks like a linker bug in any case)? — John L
Could be a stdcall/ccall mismatch. Does the symbol name in the DLL have a suffix like @4? — Simon Marlow
I'm using ghc 6.12.3 which comes with HaskellPlatform 2010.2.0.0. 'libcairo-2.dll' is in C:\GTK\bin, no spaces or anything. More, I looked with 'filemon' at what ghci does and in there it is can be seen that it loads this library in the process - so probably not a library location problem. — dilettant
As for library, nm for this symbol gives: "68df9f58 T _cairo_surface_destroy". I see nothing wrong and symbol is defined. Library is taken from — dilettant

NovaDenizen NovaDenizen · Accepted Answer · 2012-09-28T17:08:54

I suspect you're running into many of the issues I just did.

I tried to do something recently with Haskell and ZeroMQ on windows. GHC runs on Windows, and ZeroMQ has a MingW32 port, and there is a standard ZeroMQ Cabal package, so I thought this would work.

However:

GHC only has partial support for dynamic linking on Windows. See here.
The ZeroMQ Cabal package depends on the static version of libzmq.
GHC on Windows uses MingW32 conventions for its libraries and dll's.
ZeroMQ only builds a dynamic .dll in their MingW32 port, not a .a static archive.

I could not make all the pieces fit together, so no Haskell-based ZeroMQ coding on my windows box.

Haskell, GHC, win32, cairo

2 Answers