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Issues with Decimal and three-argument pow() #130230
Description
Crash report
- Three-argument
pow()with non-Decimal first argument does not work in the Python implementation.
>>> from decimal import Decimal
>>> pow(10, Decimal(2), 7)
Decimal('2')
>>> from _pydecimal import Decimal
>>> pow(10, Decimal(2), 7)
Traceback (most recent call last):
File "<python-input-3>", line 1, in <module>
pow(10, Decimal(2), 7)
~~~^^^^^^^^^^^^^^^^^^^
TypeError: unsupported operand type(s) for ** or pow(): 'int', 'Decimal', 'int'But it works in the C implementation.
- Three-argument
pow()with only Decimal third argument crashes in the C implementation.
>>> from decimal import Decimal
>>> pow(10, 2, Decimal(7))
python: ./Modules/_decimal/_decimal.c:139: find_state_left_or_right: Assertion `mod != NULL' failed.
Aborted (core dumped)In the Python implementation it only raises TypeError, which is expected.
Activity
pythongh-130230: Fix crash in pow() with only Decimal third argument
serhiy-storchaka commentedon Feb 17, 2025
#130237 fixes the second issue. It was a regression in 3.13 (most likely introduced in #106078). In 3.12 and older,
pow(10, 2, Decimal(7))evaluates toDecimal('2').The first issue is older (it exists from the beginning) and much more complex.
skirpichev commentedon Feb 18, 2025
It's just an instance of #130104. I doubt we can do something on side of the pure-Python module.
BTW, 100% compatibility is not a goal here.
skirpichev commentedon Feb 18, 2025
Second issue works for me (no crash) for <3.13, removing label.
gh-130230: Fix crash in pow() with only Decimal third argument (GH-13…
pythongh-130230: Fix crash in pow() with only Decimal third argument (p…
[3.12] pythongh-130230: Fix crash in pow() with only Decimal third ar…
[3.12] pythongh-130230: Add new tests for 3-arg pow() with Decimal (p…
[3.12] gh-130230: Add new tests for 3-arg pow() with Decimal (GH-130237…
serhiy-storchaka commentedon Feb 18, 2025
I found these issues when writing tests for #130104, but I was not sure that it was the only cause.
[3.13] gh-130230: Fix crash in pow() with only Decimal third argument (…