Some classes in Dungeons & Dolls serialize themselves using
`File.Write(this)` in their destructors. Because `File.Write` takes the
argument by value, a copy of `this` is created. If the destructor is
called on the copied `this`, it falls into an an infinite loop.
Delegates "weakly" reference objects, meaning that referenced objects
can be deleted. Delegate invocations must not invoke on deleted objects.
This is achieved as follows:
* Each heap object has a sequential number.
* Each delegate object is backed by a page storing (object, function,
seq) triples.
* Deleted objects can be detected by comparing the sequential number
stored in the delegate with the sequential number of the object
currently on the heap.
This is consistent with the AliceSoft's implementation (presumed from
the contents of resume save).
This implementation removes dead objects from the delegate in DG_CALL
and DG_NUMOF instructions. (We could do that more often, e.g. when an
object is added to a delegate.)
This breaks existing resume saves that contain delegates. For games that
predate delegate support, this does not affect the save format.
This reverts the following commits:
* 4b1257f "Fix delegate memory management"
* 9bb4665 "Add changes to vm.h" (partial revert)
* 75d6386 "Fix ResumeSave/ResumeLoad bugs with delegates" (partial
revert)
We are going to take a different approach to implementing weak
references in delegates.
Although delegate pages store references to objects on the heap,
adding/removing objects from a delegate does not affect their reference
counts. When an object that is a member of a delegate is deleted, it is
automatically removed from the delegate.
In practice, this means that every object needs to keep a list of
delegates that it belongs to. This increases the size of the page header
on 64 bit systems, but not by much since the additional metadata can be
stored in a union with the array-specific metadata.
1. DG_CALL has to clean up the stack before jumping to the return
address.
2. DG_SET (contrary to its name) is an append operation; it's basically
a combination of DG_NEW_FROM_METHOD and DG_PLUSA.
3. DG_SET and DG_PLUSA need to check for and ignore duplicates.
4. Delegate pages store *references* to structs; the VM should NOT copy
the struct page when copying a delegate page.
Print the new v11+ array types properly. Also, print the array rank for
old array types.
The code for reading v11+ ain data is simplified a lot here as well.
- Create separate directories for source and header files.
- Build code shared between xsystem4 and aindump as a static library.
- Create header dirs gfx/ system4/ and vm/
- Make CG.c/h usable without a running VM
kichikuou