RE: swap leak problem

Oh yes, one more datum. If I run hs_perform_gc before each and every mallocForeignPtrBytes and reallocBytes, the leak goes much more slowly, and the code gets much further in the job before getting killed. But it still leaks, and still gets killed.

It could potentially be a memory leak in the RTS. There are two ways to proceed: if you have a GHC build around, you can compile up a debugging RTS and run with sanity checking enabled (+RTS -DS), which will check for memory leaks. If there are any memory leaks in the RTS, this will throw an assertion failure immediately. Alternatively, you can package up your code and send it to us with instructions on how to reproduce. Cheers, Simon