CODEWITHSUNDEEP
macoshaskellghcghci
Wilbur Vandrsmith
Wilbur Vandrsmith

Reputation: 5050

Calling dynamic libraries from c-sources fails in ghci

I have some C functions from a dynamic library (just zlibVersion here) that I'd like to call from bundled C code in a cabal package. Here I call it both directly as a foreign import and indirectly through the bundled C code to show that the latter crashes ghci, even after the former succeeds.

Main.hs:

module Main (main) where

import Foreign.C.String (CString, peekCString)

foreign import ccall "foreign_test" foreignTest :: IO ()
foreign import ccall "zlibVersion" zlibVersion :: IO CString

main :: IO ()
main = do
  zlibVersion >>= peekCString >>= putStrLn
  foreignTest

foreign_test.c:

#include <stdio.h>
#include <zlib.h>

void foreign_test() {
    puts(zlibVersion());
}

It works fine from a compiled binary:

$ cabal build
$ dist/build/cabal-extra-libs-test/cabal-extra-libs-test
1.2.5
1.2.5

But the indirect call crashes ghci:

$ cabal repl
Preprocessing executable 'cabal-extra-libs-test' for
cabal-extra-libs-test-0.1.0.0...
GHCi, version 7.10.3: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( Main.hs, interpreted )
Ok, modules loaded: Main.
*Main> main
1.2.5
dyld: lazy symbol binding failed: Symbol not found: _zlibVersion
  Referenced from: /var/folders/pz/920gzhqn01q8d6vjkvy1yvdr0000gn/T/ghc6850_0/libghc_1.dylib
  Expected in: flat namespace

dyld: Symbol not found: _zlibVersion
  Referenced from: /var/folders/pz/920gzhqn01q8d6vjkvy1yvdr0000gn/T/ghc6850_0/libghc_1.dylib
  Expected in: flat namespace

cabal-extra-libs-test.cabal:

name:                cabal-extra-libs-test
version:             0.1.0.0
build-type:          Simple
cabal-version:       >=1.10

executable cabal-extra-libs-test
  default-language: Haskell2010
  main-is: Main.hs
  build-depends: base

  c-sources: foreign_test.c
  extra-libraries: z

GHC is 7.10.3 with cabal-install 1.24.0.0 on OS X 10.11.5. Building with stack and stack ghci produces the same crash.

Upvotes: 2

Views: 156

Answers (1)

Phyx
Phyx

Reputation: 2697

That's peculiar.. I don't know much about OSX but dyld: lazy symbol binding failed: Symbol not found: _zlibVersion gives the impression It thinks OSX is an underscore platform (e.g. one where C functions are mangled with an _).

Is this a standard GHC build? and can you try with 8.0.1? lots has changed in the linker.

Upvotes: 1

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