bpo-36027: Fix a potential refcount bug in long_pow #26690
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mdickinson
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needs backport to 3.8
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3.8 is in security-fix-only mode; adjusting the backport labels. |
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Yes, this showed up for me because I introduced a new path that, for exponent 1 and no modulus, invoked REDUCE but not MULT. Without a modulus, REDUCE didn't overwrite |
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Thanks @mdickinson for the PR 🌮🎉.. I'm working now to backport this PR to: 3.10, 3.9. |
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Sorry @mdickinson, I had trouble checking out the |
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GH-26702 is a backport of this pull request to the 3.9 branch. |
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(cherry picked from commit 5924243) Co-authored-by: Mark Dickinson <mdickinson@enthought.com>
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GH-26703 is a backport of this pull request to the 3.10 branch. |
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This PR fixes a reference counting bug introduced in #13266 and identified by @tim-one in #26662: if we don't set
temptoNULL, and if the value it has at this point is retained until the end of the function, then we end up doing an extra decref. I spent some time trying to identify a test-case that exercises this bug, and failed - I couldn't find a code path wheretempisn't re-used at some point. Nevertheless, it's a potential point of fragility for maintenance of this code.https://bugs.python.org/issue36027