Comment 4 for bug 1664302

The original stack trace points to a (I think) clear this==NULL bug in cac::transferChanToVirtCircuit. Specifically the piiu->installChannel which looks like it should be conditional on newIIU.

The handling of piiu isn't so straightforward. As I read it, this->serverTable.lookup() returns NULL of failure. piiu is then passed to findOrCreateVirtCircuit() by *reference*. That is, a reference to a pointer. findOrCreateVirtCircuit() returns true if piiu is now non-NULL. So it seems clear that piiu should not be de-referenced unless this boolean newIIU is true.

https://github.com/epics-base/epics-base/blob/3.14/src/ca/cac.cpp#L638

I won't pretend to understand the logic here. The most recent footprints in this area are in 2010 with changes dating from 2008. This commit carries the inspiring message "COMPLETELY UNTESTED" :)

https://github.com/epics-base/epics-base/commit/23612a7afe1c6e0a208bf4a0acecd2a5e2468380