Upgrading ASDF reveals many bug in PCL
On all other implementations, ASDF can upgrade itself. On CMUCL, this breaks badly.
To test it, go into a git checkout of asdf and do:
make u l=cmucl
Trying to upgrade from 3.1.7, I have an issue whereby CMUCL believe that, after reloading and redefinitions, MODULE isn't subtypep of its superclass COMPONENT.
Trying to upgrade from 3.2.0, the CMUCL fails to allocate a newly added slot FORCED when creating an object of class SEQUENTIAL-PLAN, which causes INITIALIZE-INSTANCE to fail when trying to initialize it:
defined slot inside INITIALIZE-INSTANCE:
Error in function "DEFMETHOD SLOT-MISSING (T T T T)": When attempting
to set the slot's value to NIL (setf of slot-value), the slot
ASDF/FORCING:FORCED is missing from the object
#<ASDF/PLAN:SEQUENTIAL-PLAN {5A38C46D}>.
NB: Upgrading ASDF on CMUCL has traditionally always been unstable due to various PCL bugs.