Do you remember your first computer program? When you had finished writing it, what was the first thing you did? You did the simplest possible test: you ran it.
As programs increase in size, so do the amount of possible tests. It’s worth considering which tests we actually end up running: imagine the children’s game Battleship, where the ocean is the space of all possible program executions, the battleships are the bugs that you are looking for, and each individual missile you fire is a test you run (white if the test passes, red if the test fails.) You don’t have infinite missiles, so you have to decide where you are going to send them.
Read more...
An “easy”, two-step process:
- Apply this patch for i686. (Why they haven’t fixed this in the trunk, I have no idea.)
- Configure with
CFLAGS="-U_FORTIFY_SOURCE -fno-stack-protector -O2" (this disables fortify source and stack protection which Ubuntu enables by default but interferes with glibc. You need to keep optimizations on, because glibc won’t build without it.) You’ll need to do the usual extra dance of creating a separate build directory and specifying a prefix.
Hope this helps someone else. In case you were wondering why I was building glibc, it’s because I was reporting these two bugs in iconv:
Read more...
Someone recently asked on haskell-beginners how to access an lazy (and potentially infinite) data structure in C. I failed to find some example code on how to do this, so I wrote some myself. May this help you in your C calling Haskell endeavours!
The main file Main.hs:
{-# LANGUAGE ForeignFunctionInterface #-}
import Foreign.C.Types
import Foreign.StablePtr
import Control.Monad
lazy :: [CInt]
lazy = [1..]
main = do
pLazy <- newStablePtr lazy
test pLazy -- we let C deallocate the stable pointer with cfree
chead = liftM head . deRefStablePtr
ctail = newStablePtr . tail <=< deRefStablePtr
cfree = freeStablePtr
foreign import ccall test :: StablePtr [CInt] -> IO ()
foreign export ccall chead :: StablePtr [CInt] -> IO CInt
foreign export ccall ctail :: StablePtr [CInt] -> IO (StablePtr [CInt])
foreign export ccall cfree :: StablePtr a -> IO ()
The C file export.c:
Read more...
