agl:

I believe that I've managed to distill a crash which has been driving me crazy for a few days into a short enough test case (22 lines) that it might be useful.

In short: the threaded RTS will call the finialiser of a ForeignPtr while an exception handler still holds a reference to it:

% ghc -make fptest.hs cbits.c -threaded [1 of 1] Compiling Main ( fptest.hs, fptest.o ) Linking fptest ... % ./fptest New object getting created: 66f010 Finaliser getting called for 66f010 Use called for 66f010

cbits.c: http://hpaste.org/6420 fptest.hs: http://hpaste.org/6421

I'm hoping that this is useful to someone who knows the RTS.

Create a ticket on the bug tracker, and I'm sure Ian or Simon M will have a look at it. http://hackage.haskell.org/trac/ghc/newticket?type=bug -- Don