_weakref.__init__() doesn't catch errors correctly. Example:
--------------------- 8< -------------------------
from gc import collect
import _weakref

class FuzzingUserClass:
    pass

obj = _weakref.ref(FuzzingUserClass)

# Exception not raised??
obj.__init__(
    0,
    0,
    0,
)

# Exception catched here??
collect()
--------------------- 8< -------------------------

Attached patch fix the bug for py3k branch: return -1 on error 
(instead of 1).

The bug and the fix are trivials. Can anyone review my patch?

The patch looks absolutely fine to me. (I think I have to have another
core developer look at it too, though.)

Adding a simple unit test would be nice.

Add a test to check to regression.

I think the test should check that TypeError is actually raised:
  self.assertRaises(TypeError, r.__init__, 0, 0, 0, 0, 0)
It's even shorter than the try/except block...

amaury: oh yes, i forget to use assertRaise(). A new patch is 
attached.

Both patches look fine to me.
They could be backported to 2.5 as well.

Fixed in r66352.