Impose new limit for Python integers #123497
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interpreter-core
(Objects, Python, Grammar, and Parser dirs)
type-feature
A feature request or enhancement
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serhiy-storchaka
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Instead of be limited just by the size of addressable memory (2**63 bytes), Python integers are now also limited by the number of bits, so the number of bit now always fit in 64-bit integer. Both limits are much larger than what can be available on practice, so there is no effect on users. _PyLong_NumBits() and _PyLong_Frexp() are now always successful.
This was referenced Sep 5, 2024
serhiy-storchaka
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Sep 29, 2024
Instead of be limited just by the size of addressable memory (2**63 bytes), Python integers are now also limited by the number of bits, so the number of bit now always fit in a 64-bit integer. Both limits are much larger than what might be available in practice, so it doesn't affect users. _PyLong_NumBits() and _PyLong_Frexp() are now always successful.
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Merged the signed version, as this is what @encukou preferred. |
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The upper limit of Python integers is determined by by the size of addressable memory. On 64-bit platforms this is about$2^{63}$ bytes or about $15\cdot 2^{62} < 2^{66}$ bits. Unfortunately, the number of bits of some integers cannot be represented as a 64-bit integer, this complicates the code.
The following PR lowers the limit to about$2^{64}$ bits or about $2^{65}/15 > 2^{61}$ bytes. It is still much larger than practically achievable (larger that the limit of addressable memory in modern processors).
First proposed in #121486, then discussed in https://discuss.python.org/t/imposing-a-hard-limit-on-python-integers/62302.
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