Compiled FFI static imports are invalid when imported in GHCI
When I try to use the FFI syntax for static storage, only modules running in interpreted mode (ie GHCI) work properly. Compiled modules have invalid pointers, and do not work. I asked in #haskell, and tommd suggested that this might be an architecture-dependent error in GHC.
Here's the code used to reproduce the problem. I'm using sys_siglist
declared in <signal.h>
, since it's similar to how I originally found the problem, but I suspect this will occur for any static data.
Given the following modules:
-- A.hs
{-# LANGUAGE ForeignFunctionInterface #-}
module A where
import Foreign
import Foreign.C
foreign import ccall "&sys_siglist"
siglist_a :: Ptr CString
-- B.hs
{-# LANGUAGE ForeignFunctionInterface #-}
module B where
import Foreign
import Foreign.C
foreign import ccall "&sys_siglist"
siglist_b :: Ptr CString
-- Main.hs
{-# LANGUAGE ForeignFunctionInterface #-}
module Main where
import Foreign
import Foreign.C
import A
import B
foreign import ccall "&sys_siglist"
siglist_main :: Ptr CString
main = do
putStrLn $ "siglist_a = " ++ show siglist_a
putStrLn $ "siglist_b = " ++ show siglist_b
putStrLn $ "siglist_main = " ++ show siglist_main
peekSiglist "a " siglist_a
peekSiglist "b " siglist_b
peekSiglist "main" siglist_main
peekSiglist name siglist = do
ptr <- peekElemOff siglist 2
str <- maybePeek peekCString ptr
putStrLn $ "siglist_" ++ name ++ "[2] = " ++ show str
Running the application via GHCI gives correct output:
$ runhaskell Main.hs
siglist_a = 0x00007f53a948fe00
siglist_b = 0x00007f53a948fe00
siglist_main = 0x00007f53a948fe00
siglist_a [2] = Just "Interrupt"
siglist_b [2] = Just "Interrupt"
siglist_main[2] = Just "Interrupt"
However, if one of them is compiled, its pointer will be invalid:
$ ghc -c A.hs
$ runhaskell Main.hs
siglist_a = 0x0000000040378918
siglist_b = 0x00007fe7c029ce00
siglist_main = 0x00007fe7c029ce00
siglist_a [2] = Nothing
siglist_b [2] = Just "Interrupt"
siglist_main[2] = Just "Interrupt"
I thought this might be related to
Trac metadata
Trac field | Value |
---|---|
Version | 6.12.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (FFI) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |