C module weirdness

I don’t have any test code for this, it’s something I have observed. But I’ll probe deeper the next time I come across it.

Anyway – when there is a crash in a C module, sometimes it becomes a zombie. More specifically, trying to kill the module reports “Incarnation not found”, and trying to reload the module reports “% in module title”.

What causes these messages to appear? Looking at Kernel.s.ModHand, it appears as if the “Incarnation not found” happens when the module apparently exists, but doesn’t have any incarnations (looking at LookUp_Module).
I’m not sure how we get from here to the module handler thinking there’s an unwanted postfix (the ‘%’) when loading a new copy of the module.

Does anybody have any ideas as to what might be going wrong to get the kernel into having a zombie module?

At a guess I’d say there’s three ways you could end up in this state:

1. A crash during module initialisation
2. A crash during module shutdown
3. Random memory corruption

1 and 2 should be easy enough to reproduce for testing purposes, 3 would be a lot harder.