On 26/01/2022 22:41, Barry wrote:
Run python and your code under a debugger and check the ref count of
the object as you step through the code.
Don’t just step through your code but also step through the C python code.
That will allow you to see how this works at a low level.
Setting a watch point on the ref count will allow you run the code and
just break as the ref count changes.
That is what I do when a see odd c api behaviour.
Barry
Thanks - I have tried a few times on a few projects to run a debugger in
mixed language mode and never had any success.
I will have to try again.
As posted in the original message - immediately before the call to
the C function/method sys.getrefcount reports the count to be 2
(meaning it is actually a 1).
Inside the C function the ref count is incremented and the Py_REFCNT
macro reports the count as 3 inside the C function as expected (1 for
the name in the Python code, 1 for the argument as passed to the C
function, and 1 for the increment), so outside the function one would
expect the ref count to now be 2 (since the reference caused by
calling the function is then reversed).
However - Immediately outside the C function and back in the Python
code sys.getrefcount reports the count to be 2 again - meaning it is
now really 1. So that means that the refcount has been decremented
twice in-between the return of the C function and the execution of
the immediate next python statement. I understand one of those
decrements - the parameter's ref count is incremented on the way in
so the same object is decremented on the way out (so that calls don't
leak references) but I don't understand where the second decrement is
coming from.
Again there is nothing in the Python code that would cause that
decrement - the decrement behavior is in the Python runtime.
--
Anthony Flury
email :anthony.fl...@btinternet.com
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Anthony Flury
email :anthony.fl...@btinternet.com
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Anthony Flury
email : anthony.fl...@btinternet.com
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