Description

MrBitBucket

opened on Nov 23, 2024

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Bug report

Bug description:

An existing C api extension compiled with Python 3.7-3.11 behaves differently when run in Python 3.14.0a2. Causing a reference count change where none is expected. The python test code looks like this

from sys import getrefcount
from _rl_accel import unicode2T1

utext = 'This is the end of the world'

class Font:
    def __init__(self,name):
        self.fontName = name
        self.substitutionFonts = []
        self.encName = 'utf8'

font = Font('Helvetica')

defns = 'utext font font.encName font.fontName font.substitutionFonts'.split()
rc0 = [getrefcount(eval(x,globals())) for x in defns]
print(rc0)
unicode2T1(utext,[font]+font.substitutionFonts)
rc1 = [getrefcount(eval(x,globals())) for x in defns]
print(rc1)
if rc1!=rc0:
    print('!!!!! reference counts changed !!!!!')

The C function unicode2T1 is not expected to change any of the refcounts checked, but if built with python 3.7-3.11
we see a decrease in the refcount for font.encName when running in python 3.14.0a2.

If built with python 3.14.0a2 the reference count decrease is not seen in the test. It seems that my code is broken in terms of the abi3 guarantee.

To ease checking I built a bash script to checkout and build the test environments; this can be found here.

I run this like

EARLYPYTHON=~/bin/python311 LATEPYTHON=~/bin/python314 tests/runner.sh

Sorry this example is so large, but at least reportlab is not required. We do have a python version of this code rl_accel.py

CPython versions tested on:

3.9, 3.10, 3.11, 3.12, 3.13, 3.14

Operating systems tested on:

Linux

Related

discuss.python.org/t/3-14-0a2-rebuild-needed-for-0x03070000-limited-api-c-extension/72006

Activity

1. MrBitBucket

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Nov 23, 2024
2. MrBitBucket commented on Nov 23, 2024

   

   MrBitBucket

   on Nov 23, 2024

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   I think this is expected now that the immortality of some/all globals is happening in Python >= 3.12. Probably I just need to build new wheels using a late python.

   Reacted by Erlend E. Aasland
3. picnixz commented on Nov 23, 2024

   

   picnixz

   on Nov 23, 2024

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   I'm not sure we can do anything on our side since it affects 3rd party extensions and a security-branch only. However I don't know the exact policy concerning that kind of breaking change hence I'm asking @iritkatriel or @vstinner.
4. picnixz

   added

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   pendingThe issue will be closed if no feedback is providedThe issue will be closed if no feedback is provided

   on Nov 23, 2024
5. ZeroIntensity commented on Nov 23, 2024

   

   ZeroIntensity

   on Nov 23, 2024

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   As far as I know, the actual reference count of an object is an implementation detail, not part of the stable ABI.
6. vstinner commented on Nov 25, 2024

   

   vstinner

   on Nov 25, 2024

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   Can you try to write a reproducer which doesn't depend on third party code?
7. vstinner commented on Nov 25, 2024

   

   vstinner

   on Nov 25, 2024

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   Ah, this issue is also discussed at: https://discuss.python.org/t/3-14-0a2-rebuild-needed-for-0x03070000-limited-api-c-extension/72006
8. picnixz

   added

   3.14bugs and security fixesbugs and security fixes

   buildThe build process and cross-buildThe build process and cross-build

   and removed

   pendingThe issue will be closed if no feedback is providedThe issue will be closed if no feedback is provided

   buildThe build process and cross-buildThe build process and cross-build

   on Dec 15, 2024
9. erlend-aasland commented on Jan 4, 2025

   

   erlend-aasland

   on Jan 4, 2025

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   Based on the discussion over at DPO, it sounds to me we can close this as "not planned".
10. erlend-aasland

    added

    pendingThe issue will be closed if no feedback is providedThe issue will be closed if no feedback is provided

    on Jan 4, 2025
11. ZeroIntensity commented on Jan 4, 2025

    

    ZeroIntensity

    on Jan 4, 2025

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    Yeah, reference counts aren't part of the stable ABI. I wonder if we should add a sys._is_immortal for situations like this, similar to how we have sys._is_interned.

    Reacted by Erlend E. Aasland
12. erlend-aasland

    closed this as not plannedon Jan 4, 2025
13. erlend-aasland

    removed

    pendingThe issue will be closed if no feedback is providedThe issue will be closed if no feedback is provided

    on Jan 4, 2025

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