On 10/04/17 13:50, Niklas Hambüchen wrote:
I'm not sure if it's the solution to your problem already, but there's a Cabal bug that makes it not pass cc-options and ld-options to GHC as ghc-options correctly:
https://github.com/haskell/cabal/issues/4435
You need to additionally pass these options as `ghc-options: "-optl -lyourlib"` if you want to be sure.
Further, looking at an example I have around, my cabal `library` output (say I have mypackage.cabal with a "library" in there, it's called "dist/build/libHSmypackage-...so") link against things like libHSghc-prim, but not against the RTS (libHSrts...so). I think this makes sense, because as far as I can tell, the RTS is only linked in when you compile the final executable, and which RTS .so file is chosen depends on whether you link in the standard runtime, the -threaded runtime, the debug runtime, etc.
So I believe that when loading Haskell from C you will have to dlopen() the RTS you want explicitly, before loading your own .so file. You probably also need to load the RTS with the RTLD_GLOBAL dlopen flag so that when you later load your .so, it can see the RTS symbols.
An alternative is probably to add HSrts-ghc-VERSION to `extra-libraries`, like I do here: https://github.com/nh2/call-haskell-from-anything/blob/0ba6737ea17a45e59704d.... That links it explicitly like you planned to do.
According to https://github.com/nh2/call-haskell-from-anything/issues/19#issuecomment-263... there is now a `foreign-library` stanza in Cabal that is supposed to free you of manually having to link/load the RTS. I haven't tried it yet, since at the time that comment was written, it wasn't released yet. Now it might be.
Detail documentation of that feature: https://github.com/haskell/cabal/blob/db26fa21cba92097d9fdeb580ddf797c35af8e...
Hope this helps!
Niklas
Unfortunately, adding rts to extra-libraries section doesn't help. Now I get a build error from cabal: Process exited with code: ExitFailure 1 Logs have been written to: /home/void/dev/hs/test/.stack-work/logs/test-0.1.log Configuring test-0.1... Cabal-simple_mPHDZzAJ_1.24.2.0_ghc-8.0.2: Missing dependency on a foreign library: * Missing C library: HSrts-ghc8.0.2 This problem can usually be solved by installing the system package that provides this library (you may need the "-dev" version). If the library is already installed but in a non-standard location then you can use the flags --extra-include-dirs= and --extra-lib-dirs= to specify where it is. Relevant cabal file options: extra-lib-dirs: /usr/lib/ghc-8.0.2/rts extra-libraries: HSrts-ghc8.0.2 ghc-options: -Wall -Werror -shared -fPIC -dynamic Note that this is a library, not an executable as in call-haskell-from-anything.