Mysterious intermittent error

[kripken]

Some of the spec tests fail randomly. This is very odd as there is nothing random in the interpreter, nor the test. I seem to only see it on a 32-bit machine.

To see it, I just run ./check and stop after the spec tests, then keep doing that until it fails.

Valgrind finds nothing.

Looks somehow float rounding or signaling nan related, based on the error (we fail the spec test due to a nan having or not having the signaling bit).