Missing symbol in Haskell libclang binding: clang_toggleCrashRecovery - haskell

Question

have a bug with libClang, then i install it with cabal at the end i get:
[13 of 13] Compiling Clang ( src/Clang.hs, dist/build/Clang.o )
In file included from ./src/Clang/FFI_stub_ffi.h:6,
from src/Clang/FFI_stub_ffi.c:4:0:
/usr/local/lib/ghc-7.0.3/include/HsFFI.h:29:0:
warning: "__STDC_LIMIT_MACROS" redefined
<command-line>:0:0:
note: this is the location of the previous definition
src/Clang/FFI_stub_ffi.c: In function ‘prim_getCString’:
src/Clang/FFI_stub_ffi.c:33:0:
warning: assignment discards qualifiers from pointer target type
src/Clang/FFI_stub_ffi.c: In function ‘prim_toggleCrashRecovery’:
src/Clang/FFI_stub_ffi.c:2181:0:
warning: implicit declaration of function ‘clang_toggleCrashRecovery’
Registering LibClang-0.0.9...
when i now want to compile a script with ghc that uses Clang i get:
ghc --make test.hs -L.
[1 of 1] Compiling Main ( test.hs, test.o )
Linking test ...
/home/foo/.cabal/lib/LibClang-0.0.9/ghc-7.0.3/libHSLibClang-0.0.9.a(FFI_stub_ffi.o): In function `prim_toggleCrashRecovery':
FFI_stub_ffi.c:(.text+0x1577): undefined reference to `clang_toggleCrashRecovery'
collect2: ld returned 1 exit status
someone a idea what to do?

Answer 1

I can reproduce this on Arch Linux / x86_64: my libclang build emits a warning about the missing symbol,
src/Clang/FFI_stub_ffi.c:2181:1:
warning: implicit declaration of function ‘clang_toggleCrashRecovery’
[-Wimplicit-function-declaration]
Registering LibClang-0.0.9...
Installing library in /home/dons/.cabal/lib/LibClang-0.0.9/ghc-7.0.3
Registering LibClang-0.0.9...
and linking a test program:
import Clang
main = print "yes"
fails with:
$ ghc --make A.hs
Linking A ...
/home/dons/.cabal/lib/LibClang-0.0.9/ghc-7.0.3/libHSLibClang-0.0.9.a(FFI_stub_ffi.o):
In function `prim_toggleCrashRecovery':
FFI_stub_ffi.c:(.text+0x3513): undefined reference to `clang_toggleCrashRecovery'
collect2: ld returned 1 exit status
The process of solving these kind of linker errors is to identify which C library archive that symbol lives in. Searching in my libclang install, I can't find this symbol:
$ find . -type f -exec grep toggleCrashRecovery {} \;
$ grep toggleCrashRecovery /usr/lib/llvm/*
$ grep toggleCrashRecovery /usr/lib/llvm/*/*
zsh: no matches found: /usr/lib/llvm/*/*
which is a clue that it might be something only available in a different version of libclang. I'm using clang/llvm 2.9, which does not have this symbol, while google does turn up some older headers that do include it. So my best guess is that this symbol is no longer available in LLVM, and thus the current haskell/libclang package depends on LLVM/Clang 2.8.
Solution:
Download the libclang source,
$ cabal unpack libclang
and patch it to remove references to the toggle* functions.
$ ghc --make A.hs
[1 of 1] Compiling Main ( A.hs, A.o )
Linking A ...
A patched version is here: http://www.galois.com/~dons/tmp/LibClang-0.0.10.tar.gz
I've also forwarded this info to the author.

Answer 2

Thanks Don for the quick fix.
This issue is fixed with the latest version on Hackage:
http://hackage.haskell.org/package/LibClang-0.1.0
Please "cabal update" and you should be good to go.
Alternatively, you could get the source from https://github.com/chetant/LibClang