On Wed, 2012-07-11 at 09:50 +0100, Simon Marlow wrote:
On 10/07/2012 23:03, Nicolas Trangez wrote:
All,
I sent this mail to Haskell Cafe earlier today, and was pointed [1] at this list. As such...
Any help/advice would be greatly appreciated!
It looks like you're making a ForeignPtr from the Addr# or Ptr that points to the contents of the ByteArray#. Since this ForeignPtr doesn't keep the original ByteArray# alive, the GC will collect it. You need to keep a reference to the ByteArray# too.
Even though I suspected this and it's blatantly obvious, I failed to recognize the ForeignPtr as returned by mallocPlainForeignPtrBytes keeps the reference. Stupid me. Thanks.
Basically you need a version of mallocForeignPtrBytes that has supports alignment. Unfortunately it's not possible to write one because the internals of ForeignPtrContents are not exported - we had a recent ticket about that (http://hackage.haskell.org/trac/ghc/ticket/7012) and in 7.6.1 we will export the necessary internals. If you want we could also add mallocForeignPtrAlignedBytes - please send a patch.
http://hackage.haskell.org/trac/ghc/ticket/7067 Thanks, Nicolas