[Python-Dev] Fun with numbers (original) (raw)

Guido van Rossum guido@python.org
Thu, 25 Apr 2002 21:02:53 -0400

Tim, Jeremy, and I are having so much fun... [...] >>> 23000 .class = bool Debug memory block at address p=0x814f544: 485823496 bytes originally requested the 4 pad bytes at p-4 are not all FORBIDDENBYTE (0xfb): at p-4: 0x7a *** OUCH at p-3: 0x61 *** OUCH at p-2: 0xc8 *** OUCH at p-1: 0x3c *** OUCH the 4 pad bytes at tail=0x250a094c are Segmentation fault

Ouch. Fixed in CVS for this particular case, but I think you may still be able provoke this with a built-in type that derives from another built-in type without adding any new fields, if the base type has a funky allocator that the derived type doesn't inherit. Also, the fix means that if an extension defines a type that inherits from int but doesn't override tp_alloc and tp_free, it inherits a tp_alloc that's not matched to the tp_free. But why would anyone do that...?

Inspired by this, I tried something else.

>>> print True
True
>>> True.__class__ = int
>>> print True
1
>>>

There are no ill side effects. Handy for bool-haters. :-)

--Guido van Rossum (home page: http://www.python.org/~guido/)