Hello John, When this has happened to me in the past, it was because I was trying to allocate using a corrupted read (though, this was a userland). So it's very plausible you've hit a bug in GHC. Have you tried 7.2? HEAD? Edward Excerpts from John Meacham's message of Fri Jan 27 19:33:13 -0500 2012:

So... I knew that ghc was a memory hog.. but I am suddenly running into it dying with messages like the following:

ghc: out of memory (requested 5997056753664 bytes) make[1]: *** [jhc] Error 1

Before I go out and find a machine with 6 terrabytes of RAM, I figured I'd post here first :)

now the strange thing is, this started happening at the same time for both ghc 6.12.1 and 7.0.x (will report exact version later) so clearly something about my code is tickling ghc the wrong way. Though, ghc 7.0.x is slightly better in that it requests only one and a half terrabytes of ram :)

Hmm.. I will try to track down a smaller test case, or narrow down what change caused it, but everything looks quite benign. I did recently add NoMonomorphismRestriction, NoMonoLocalBinds, and OverloadedStrings to my standard options, which is the only global change across the board I can think of...

John