[Haskell-cafe] Re: Problem with directory-1.0.0.0

[Simon Marlow]

Bartosz Wójcik wrote:
> Hi Folks,
> 
> I'm facing problem after I've reinstalled directory-1.0.0.0 (setup 
> configure/build/install). Since then I cannot complie anything that needs 
> this library. It fails with following messages:
> 
> Preprocessing library haddock-2.4.0...
> Preprocessing executables for haddock-2.4.0...
> Building haddock-2.4.0...
> /usr/bin/ar: creating dist/build/libHShaddock-2.4.0.a
> Linking dist/build/haddock/haddock ...
> /usr/local/lib/ghc-6.8.2/libHSghc.a(Coverage.o): In function `scXR_info':
> (.text+0x17b7c): undefined reference to 
> `directoryzm1zi0zi0zi0_SystemziDirectory_lvl29_closure'
> /usr/local/lib/ghc-6.8.2/libHSghc.a(Coverage.o): In function `s8xU_info':
> (.text+0x1792c): undefined reference to 
> `directoryzm1zi0zi0zi0_SystemziDirectory_a43_info'
> /usr/local/lib/ghc-6.8.2/libHSghc.a(Coverage.o): In function `r7aC_closure':
> (.data+0xd18): undefined reference to 
> `directoryzm1zi0zi0zi0_SystemziDirectory_a43_closure'
> collect2: ld returned 1 exit status
> 
> Situation is following:
> Old directory-1.0.0.0 resides 
> in /usr/local/lib/ghc-6.8.2/lib/directory-1.0.0.0.
> New one in /usr/local/lib/directory-1.0.0.0.
> 
> Why new one doesn't work?
> How to force linker to use old one?

What happened here is that you recompiled directory without recompiling the 
things that depend on it (e.g. GHC).  This is a problem because compiled 
Haskell libraries don't have a fixed ABI: if you recompile the library, you 
get a different result, and all the compiled clients of the library must be 
recompiled.

For libraries that GHC depends on, this is a problem, because it's usually 
not practical to recompile GHC.  You can usually install a newer version of 
these libraries without conflicting with the old version, though.

We do think this is something that needs to be fixed in a future version of 
GHC (hopefully 6.12).

Cheers,
	Simon