plugins package unknown symbol when using cabal
cabal, cabal-install, ghc, haskell, plugins
Solution
Ok, so I had the exact same problem. Here is a workaround I found
Change the load call to
load "Plug.o" [".","dist/build/plugintest/plugintest-tmp"] [] "testplugin"
Make sure you compile the thing with -c or by using the "make" library from plugins.
Quite annoyed by this... The error suggests it is having issues linking against the standard libs, so why does showing it these .o files fix it? Anyways, this worked for me, and didn't require a ton of mucking around with .cabal files.
Problem
I'm messing around with the plugins package however I bumped into a problem. Here's the code: Util/Header.hs ``` module Util.Header(PT(..)) where data PT a = PT a deriving Show ``` Plug.hs ``` module Plug(helloPlugin) where import Util.Header helloPlugin :: PT Int helloPlugin = PT 1 ``` Main.hs ``` module Main where import Util.Header import System.Plugins main :: IO () main = do mv <- load "Plug.o" ["."] [] "helloPlugin" case mv of LoadFailure msg -> print msg LoadSuccess _ v -> print $ show (v :: PT Int) ``` This all works fine then compiling with ghc. Building with Cabal works fine as well, but when I run the executable I get this error: ``` plugintest: /home/kevin/.cabal/lib/plugins-1.5.4.0/ghc-7.6.3/HSplugins-1.5.4.0.o: unknown symbol `ghczm7zi6zi3_ErrUtils_zdsinsertzuzdsgo5_info' plugintest: user error (resolvedObjs failed.) ``` My very minimalistic cabal file: ``` name: plugintest version: 0.1.0.0 license-file: LICENSE build-type: Simple cabal-version: >=1.8 library hs-source-dirs: src exposed-modules: Util.Header build-depends: base ==4.6.*, plugins ==1.5.* executable plugintest main-is: Main.hs build-depends: base ==4.6.*, plugins ==1.5.*, plugintest == 0.1.0.0 hs-source-dirs: src ``` Now I assume the problem is that it can't find the "ErrUtils" module which is part of the ghc package installed in /usr/lib/ghc-7.x.x. Since it's using cabal it'll use the $HOME/.cabal/lib/ instead. Now I obviously wouldn't want to use /usr/lib if I wanted to make it distributable. Sadly I'm not very familiar with how packages are managed nor am I familiar with the plugins package. I have a feeling this is extremly nooby but I wasn't able to find a solution myself. So a few questions: - How can I get my dependencies to work in a way to make this distributable? - It seems I'll need to know beforehand what my Plugin.o files will depend on before actually being able to use them (If I understand correctly). Is there a way to package a .o files that I wouldn't have to worry about this problem? (Sorry if this question is too vague, feel free to ignore) Thanks in advance!