[Python] Avoid hack in setting __reduce__ attribute of CPPInstance
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Test Results 19 files 19 suites 3d 4h 24m 37s ⏱️ Results for commit b0cb54c. ♻️ This comment has been updated with latest results. |
The CPPIntance type is immutable, and new attributes can't be set:
```txt
import cppyy
>>> setattr(cppyy._backend.CPPInstance, "test", 10)
Traceback (most recent call last):
File "<python-input-3>", line 1, in <module>
setattr(cppyy._backend.CPPInstance, "test", 10)
~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: cannot set 'test' attribute of immutable type 'cppyy.CPPInstance'
>>>
```
In our pythonizations, we still want to monkey-patch a `__reduce__`
method anyway, and to make Python not complain we to a hack by setting
the attribute with the C Python API using `PyObject_GenericSetAttr`.
This function doesn't normally do any safety checks, and our monkey
patching works.
However, the Python debug build is not having any of that, thanks to a
new assert that was added a year ago:
https://github.com/python/cpython/blame/c419af9e277bea7dd78f4defefc752fe93b0b8ec/Objects/object.c#L1921
To make the ROOT Python interface work with debug builds of the Python
interpreter, we therefore have to implement adding the reduce method
properly.
This commit suggests to achieve this by defining the `__reduce__` method
in the immutable CPPInstance type within CPyCppyy, but in such a way
that its implementation can be routed to ROOT via a private API.
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The CPPIntance type is immutable, and new attributes can't be set:
import cppyy >>> setattr(cppyy._backend.CPPInstance, "test", 10) Traceback (most recent call last): File "<python-input-3>", line 1, in <module> setattr(cppyy._backend.CPPInstance, "test", 10) ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ TypeError: cannot set 'test' attribute of immutable type 'cppyy.CPPInstance' >>>In our pythonizations, we still want to monkey-patch a
__reduce__method anyway, and to make Python not complain we to a hack by setting the attribute with the C Python API usingPyObject_GenericSetAttr. This function doesn't normally do any safety checks, and our monkey patching works.However, the Python debug build is not having any of that, thanks to a new assert that was added a year ago:
https://github.com/python/cpython/blame/c419af9e277bea7dd78f4defefc752fe93b0b8ec/Objects/object.c#L1921
To make the ROOT Python interface work with debug builds of the Python interpreter, we therefore have to implement adding the reduce method properly.
This commit suggests to achieve this by defining the
__reduce__method in the immutable CPPInstance type within CPyCppyy, but in such a way that its implementation can be routed to ROOT via a private API.