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gh-102701: Fix overflow in dictobject.c#102750
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The change looks good, but it will need a test and a machine large enough to test it on. |
I used GCP n2d-standard-16 (64GiB RAM):
|
markshannon approved these changesMar 17, 2023
| @@ -596,7 +596,7 @@ new_keys_object(PyInterpreterState *interp, uint8_t log2_size, bool unicode) | |||
| assert(log2_size >= PyDict_LOG_MINSIZE); | |||
| usable = USABLE_FRACTION(1<<log2_size); | |||
| usable = USABLE_FRACTION((size_t)1<<log2_size); | |||
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I am asking for my curiosity(to become familiar with cpython); How does casting the result of1<<log2_size tosize_t fix the overflow in the dict?
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1 is int. And int is 32bit on most platforms. So 1 << 32 will overflow.
Here is example:
$ cat x.c#include <stdio.h>#include <stdlib.h>#define USABLE_FRACTION(n) (((n) << 1)/3)int main() { size_t x = USABLE_FRACTION(1 << 31); size_t y = USABLE_FRACTION((size_t)1 << 31); printf("x=%zd y=%zd\n", x, y);}$ gcc x.c && ./a.outx.c:7:16: warning: shifting a negative signed value is undefined [-Wshift-negative-value] size_t x = USABLE_FRACTION(1 << 31); ^~~~~~~~~~~~~~~~~~~~~~~~x.c:4:34: note: expanded from macro 'USABLE_FRACTION'#define USABLE_FRACTION(n) (((n) << 1)/3) ~~~ ^1 warning generated.x=0 y=1431655765There was a problem hiding this comment.
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Thanks!
Thanks@methane for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11. |
bedevere-bot commentedMar 17, 2023
GH-102777 is a backport of this pull request to the3.11 branch. |
miss-islington pushed a commit to miss-islington/cpython that referenced this pull requestMar 17, 2023
(cherry picked from commit65fb7c4)Co-authored-by: Inada Naoki <songofacandy@gmail.com>
miss-islington added a commit that referenced this pull requestMar 17, 2023
carljm added a commit to carljm/cpython that referenced this pull requestMar 17, 2023
* main: (34 commits)pythongh-102701: Fix overflow in dictobject.c (pythonGH-102750)pythonGH-78530: add support for generators in `asyncio.wait` (python#102761) Increase stack reserve size for Windows debug builds to avoid test crashes (pythonGH-102764)pythongh-102755: Add PyErr_DisplayException(exc) (python#102756) Fix outdated note about 'int' rounding or truncating (python#102736)pythongh-102192: Replace PyErr_Fetch/Restore etc by more efficient alternatives (python#102760)pythongh-99726: Improves correctness of stat results for Windows, and uses faster API when available (pythonGH-102149)pythongh-102192: remove redundant exception fields from ssl module socket (python#102466)pythongh-102192: Replace PyErr_Fetch/Restore etc by more efficient alternatives (python#102743)pythongh-102737: Un-ignore ceval.c in the CI globals check (pythongh-102745)pythonGH-102748: remove legacy support for generator based coroutines from `asyncio.iscoroutine` (python#102749)pythongh-102721: Improve coverage of `_collections_abc._CallableGenericAlias` (python#102722)pythonGH-102653: Make recipe docstring show the correct distribution (python#102742) Add comments to `{typing,_collections_abc}._type_repr` about each other (python#102752)pythongh-102594: PyErr_SetObject adds note to exception raised on normalization error (python#102675)pythongh-94440: Fix issue of ProcessPoolExecutor shutdown hanging (python#94468)pythonGH-100112: avoid using iterable coroutines in asyncio internally (python#100128)pythongh-102690: Use Edge as fallback in webbrowser instead of IE (python#102691)pythongh-102660: Fix Refleaks in import.c (python#102744)pythongh-102738: remove from cases generator the code related to register instructions (python#102739) ...
Fidget-Spinner pushed a commit to Fidget-Spinner/cpython that referenced this pull requestMar 27, 2023
warsaw pushed a commit to warsaw/cpython that referenced this pull requestApr 11, 2023
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interpreter-core(Objects, Python, Grammar, and Parser dirs) type-bugAn unexpected behavior, bug, or error
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