GeezerVison is showing github.com — GH-120754: Make PY_READ_MAX smaller than max byteobject size by cmaloney · Pull Request #121633 · python/cpython
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cmaloney
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Jul 11, 2024
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edited by bedevere-app
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Currently if code tries to do a os.read larger than the max bytes object length, the size to read gets capped to _PY_READ_MAX, then the code tries to allocate a PyBytes which fails with an OverflowError as the size is longer than what is allocatable.
Since os.read is capping the max size anyways, cap it to a size which is always allocatable as a PyBytes.
This changes behavior from bpo-21932 and enables the large file os.read test on 32 bit platforms, as it should cap the read to a platform acceptable size.
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Currently if code tries to do a os.read larger than the max bytes object
length, the size to read gets capped to `_PY_READ_MAX`, then the code
tries to allocate a PyBytes which fails with an OverflowError as the
size is larger than the max py bytes object.
Since os.read is capping the max size anyways, cap it to a size which is
always allocatable as a PyBytes.
This changes behavior from bpo-21932 and enables the large file os.read
test on 32 bit platforms, as it should cap the read to a platform
acceptable size.
cmaloney
changed the title
gh-120754: Make PY_READ_MAX smaller than max byteobject size
GH-120754: Make PY_READ_MAX smaller than max byteobject size
Jul 11, 2024
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Cap read size to smaller than the max BytesObject size. read() in POSIX
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returns at most the number of requseted bytes, this updates python ``os.read``
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to do similarly, and rather than throw an OverflowError in this case, return
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a smaller than requseted byte object.
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# Py_ssize_t type
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@unittest.skipUnless(INT_MAX < PY_SSIZE_T_MAX,
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"needs INT_MAX < PY_SSIZE_T_MAX")
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@support.bigmemtest(size=INT_MAX + 10, memuse=1, dry_run=False)
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issue here is that this will result in a memory allocation error on 32 bit machines, and this bigmemtest effectively makes it not run on 32 bit machines (They are unlikely to have that much RAM)
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