PickleWarning thrown when pickling ArrayInstance

[mmckerns]

Warnings are thrown when pickling an ArrayInstance, however it appears that the ArrayInstance does pickle.

$ pypy test_objects.py 
/Users/mmckerns/lib/pypy-2.7/site-packages/dill-0.3.5.dev0-py2.7.egg/dill/_dill.py:1658: PicklingWarning: Cannot locate reference to <type 'ArrayInstance'>.
  warnings.warn('Cannot locate reference to %r.' % (obj,), PicklingWarning)
/Users/mmckerns/lib/pypy-2.7/site-packages/dill-0.3.5.dev0-py2.7.egg/dill/_dill.py:1660: PicklingWarning: Cannot pickle <type 'ArrayInstance'>: __builtin__.ArrayInstance has recursive self-references that trigger a RecursionError.
  warnings.warn('Cannot pickle %r: %s.%s has recursive self-references that trigger a RecursionError.' % (obj, obj.__module__, obj_name), PicklingWarning)
fails: CCharType <class 'ctypes.c_char'>
fails: CWCharType <class 'ctypes.c_wchar'>
fails: CByteType <class 'ctypes.c_byte'>
...

SEEN WITH:

• pypy-2.7-v7.3.8, dill-0.3.5.dev0, numpy-1.16.6
• pypy-3.7-v7.3.8, dill-0.3.5.dev0, numpy-1.19.5
• pypy-3.8-v7.3.8, dill-0.3.5.dev0, numpy-1.19.5
• pypy-3.9-v7.3.8, dill-0.3.5.dev0, numpy-1.19.5

NOT WITH:

• pypy-3.6-v7.3.3, dill-0.3.5.dev0, numpy-1.19.5
• python2.7, dill-0.3.5.dev0, numpy-1.16.6
• python3.6, dill-0.3.5.dev0, numpy-1.19.5
• python3.7, dill-0.3.5.dev0, numpy-1.21.5
• python3.x, dill-0.3.5.dev0, numpy-1.22.2 (x=8,9,10)

[mmckerns]

ping: @anivegesana
Consequence of changes in #443, and apparently updates to pypy from v7.3.7.

[anivegesana]

I believe that this is expected behavior. I just ran the following code snippet on dill 0.3.4 and it gives the following error:

import ctypes, dill
dill.dumps(ctypes.c_char(b'8'))

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/ani/Git/dill/dill/_dill.py", line 304, in dumps
    dump(obj, file, protocol, byref, fmode, recurse, **kwds)#, strictio)
  File "/Users/ani/Git/dill/dill/_dill.py", line 276, in dump
    Pickler(file, protocol, **_kwds).dump(obj)
  File "/Users/ani/Git/dill/dill/_dill.py", line 498, in dump
    StockPickler.dump(self, obj)
  File "/Users/ani/pypy3.8-v7.3.7-osx64/lib/pypy3.8/pickle.py", line 500, in dump
    self.save(obj)
  File "/Users/ani/pypy3.8-v7.3.7-osx64/lib/pypy3.8/pickle.py", line 616, in save
    self.save_reduce(obj=obj, *rv)
  File "/Users/ani/pypy3.8-v7.3.7-osx64/lib/pypy3.8/pickle.py", line 730, in save_reduce
    save(state)
  File "/Users/ani/pypy3.8-v7.3.7-osx64/lib/pypy3.8/pickle.py", line 573, in save
    f(self, obj)  # Call unbound method with explicit self
  File "/Users/ani/Git/dill/dill/_dill.py", line 990, in save_module_dict
    StockPickler.save_dict(pickler, obj)
  File "/Users/ani/pypy3.8-v7.3.7-osx64/lib/pypy3.8/pickle.py", line 985, in save_dict
    self._batch_setitems(obj.items())
  File "/Users/ani/pypy3.8-v7.3.7-osx64/lib/pypy3.8/pickle.py", line 1016, in _batch_setitems
    save(v)
  File "/Users/ani/pypy3.8-v7.3.7-osx64/lib/pypy3.8/pickle.py", line 616, in save
    self.save_reduce(obj=obj, *rv)
  File "/Users/ani/pypy3.8-v7.3.7-osx64/lib/pypy3.8/pickle.py", line 700, in save_reduce
    save(cls)
  File "/Users/ani/pypy3.8-v7.3.7-osx64/lib/pypy3.8/pickle.py", line 573, in save
    f(self, obj)  # Call unbound method with explicit self
  File "/Users/ani/Git/dill/dill/_dill.py", line 1439, in save_type
    StockPickler.save_global(pickler, obj, name=name)
  File "/Users/ani/pypy3.8-v7.3.7-osx64/lib/pypy3.8/pickle.py", line 1086, in save_global
    (obj, module_name, name)) from None
pickle.PicklingError: Can't pickle <class 'ArrayInstanceAutoFree'>: it's not found as builtins.ArrayInstanceAutoFree

I don't think pickling ctypes via dill is supported on pypy. Let me know if I am missing something.

[mmckerns]

Ah... sorry my bad. I recently ended support for 3.6 (see #452), and thus is using an older build than the other pypy above. pypy3.6 fails, but doesn't throw the warning... but that's because it's testing against an older build. So, yes, this issue should be voided.

It's a bit weird to see that dumping a ctypes.c_char throws a warning about an ArrayInstance (and not the CCharType)... but I guess this is what it should do.