Hi, I'm trying to use a shared lib written in Haskell to overload C functions via LD_PRELOAD. You might think this is a bit silly, but hey, why not? I want to overload connect() from sys/socket.h. I'll document what I've written so far; unfortunately there doesn't seem to be a lot of documentation about this topic. This is my haskell code (in testffi.hs):
module Socks where
import Foreign.C.Types import Foreign.Ptr
newtype S_sockaddr = S_sockaddr ()
foreign export ccall "connect" connect :: CInt -> Ptr (S_sockaddr) -> CUInt -> IO CInt
connect :: CInt -> Ptr (S_sockaddr) -> CUInt -> IO CInt connect _ _ _ = return (-1::CInt)
Here's how I compile it: ghc -Wall -c -fffi testffi.hs ghc -Wall -optl "-shared" -optl "-Wl,-soname,libtestffi.so" \ -o libtestffi.so testffi.o testffi_stub.o I'm not at all sure about these compiler and linker options, but this is the best I could come up with (i.e., no errors or warnings) Then I run a test program which calls connect(). I won't include the C source of that program, but it basically connects to the IP address given as the first argument (at port given by third argument) and sends a string. Basic error checking is done, i.e. the program does test the return value of connect(): LD_PRELOAD=./libtestffi.so ./conntest 127.0.0.1 "HELO" 1234 This aborts with a segfault in scheduleWaitThread() from ./libtestffi.so The test program doesn't use threads, so I'm wondering what I did wrong? Any help is appreciated. Greetings, Stephan Walter