On 10/12/12 00:11, Nils wrote:

I'm currently working with a C library that needs to use/modify global C variables, for example:

igraph_bool_t igraphhaskell_initialized = 0;

int igraphhaskell_initialize() { if (igraphhaskell_initialized != 0) { printf("C: Not initializing. igraphhaskell_initialized = %i\n", igraphhaskell_initialized); return 1; } // initialization }

If I compile an example programm using this library everything works fine, but if I try to run the same program in GHCi it dies with the message

C: Not initializing. igraphhaskell_initialized = -907777

The value (and apparently the adress of the global variable) is completly off, and I have no idea what is causing this or how to solve this issue and make the library GHCi-friendly. Is it possible to run this code in GHCi at all? Also, since it's a foreign library I obviously cannot just change the C code to simply not use any global variables at all.

Sounds like it could be this: http://hackage.haskell.org/trac/ghc/ticket/781 Compiling your program with -fPIC should fix it. Cheers, Simon