On 5/14/22, Jonathan Kaczynski <jonathan.kaczyn...@guildeducation.com> wrote:
>
> So, I'm still wondering how Py_TYPE(v)->tp_richcompare resolves to __eq__
> on a user-defined class. Conversely, my understanding is, for a type
> defined in cpython, like str, there is usually an explicitly
> defined tp_richcompare function.
Sometimes it's simplest to directly examine an object using a native
debugger (e.g. gdb in Linux; cdb/windbg in Windows).
With a debugger attached to the interpreter, create two classes, one
that doesn't override __eq__() and one that does:
>>> class C:
... pass
...
>>> class D:
... __eq__ = lambda s, o: False
...
In CPython, the id() of an object is its address in memory:
>>> hex(id(C))
'0x2806a705790'
>>> hex(id(D))
'0x2806a6bbfe0'
Break into the attached debugger to examine the class objects:
>>> kernel32.DebugBreak()
(1968.1958): Break instruction exception - code 80000003 (first chance)
KERNELBASE!wil::details::DebugBreak+0x2:
00007ffd`8818fd12 cc int 3
Class C uses the default object_richcompare():
0:000> ?? *((python310!PyTypeObject *)0x2806a705790)->tp_richcompare
<function> 0x00007ffd`55cac288
_object* python310!object_richcompare+0(
_object*,
_object*,
int)
Class D uses slot_tp_richcompare():
0:000> ?? *((python310!PyTypeObject *)0x2806a6bbfe0)->tp_richcompare
<function> 0x00007ffd`55cdef1c
_object* python310!slot_tp_richcompare+0(
_object*,
_object*,
int)
Source code of slot_tp_richcompare():
https://github.com/python/cpython/blob/v3.10.4/Objects/typeobject.c#L7610-L7626
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