Shared GHC libraries and the runtime system

[Max Bolingbroke]

Hi Tyson,

This blog post (http://blog.well-typed.com/2009/05/buildings-plugins-as-haskell-shared-libs/)
might help explain the  motivation (actually there are a few relevant
posts on the well-typed site).

Essentially, I believe that this is done so that you can vary the RTS
by changing LD_LIBRARY_PATH. I've never used this facility so I'm
unable to say how useful this actually is (or if it actually works at
the moment).

Cheers,
Max

On 22 February 2010 21:34, Tyson Whitehead <twhitehead at gmail.com> wrote:
> I was working on a shared library that loads up the GHC runtime (via hs_init)
> and have been running into a bunch of undefined stg symbols.
>
> A bit of digging and it seems that GHC doesn't embed
>
>  - the dependency libHSrts-ghc6.12.1.so, and
>  - the associated rpath /usr/lib/ghc-6.12.1
>
> into shared libraries that it builds.  Thus, if your main executable isn't GHC
> generated (and hence has these), you run into unresolved symbols.
>
> I can work around this by manually adding them myself.  Is there any reason
> GHC can't put this information by default into shared libraries though?
>
> Thanks!  -Tyson
>
> PS:  Further digging into the various shared libraries packaged with GHC
> (Debian GHC package 6.12.1-2) reveal that they are actually missing
>
>  - the dependency libHSrts-ghc6.12.1.so, and
>  - all rpaths (i.e., there are absolutely no rpaths in any of them)
>
> $ objdump -p /usr/lib/ghc-6.12.1/base-4.2.0.0/libHSbase-4.2.0.0-ghc6.12.1.so
> ...
> Dynamic Section:
>  NEEDED      libHSinteger-gmp-0.2.0.0-ghc6.12.1.so
>  NEEDED      libgmp.so.3
>  NEEDED      libHSghc-prim-0.2.0.0-ghc6.12.1.so
>  NEEDED      libc.so.6
>  SONAME      libHSbase-4.2.0.0-ghc6.12.1.so
> ...
>
>
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