On Wed, May 8, 2013 at 6:54 PM, Niklas Hambüchen
I have an annoying bug in a C binding that can be triggered like this:
handle <- open ...
prep <- makePreparedStatement handle "INSERT ..."
performGC
runStatement prep
close handle
If I run these steps one by one in ghci, garbage ends up in my handle as expected.
However, if I "let main = do ..." this whole block in order to pack it in a test case, it does not happen, neither in ghci nor ghc.
What might be the special magic in ghci's REPL that allows me to trigger my bug so easily there?
One thing to investigate: Thread Local Storage By default ghci puts each action you run into a thread and executes it. If the underlying C code stores something (or accesses it) from thread local storage, then you will run into issues like this. Try starting ghci with -fno-ghci-sandbox. If the bad behavior goes away there, try running each step of your test case inside a forkIO from ghc with the threaded RTS. If the problem disappears in ghci but shows up with forkIO, then it's a pretty good indicator that it's related to the way the C code uses thread local storage. I hope that helps, Jason