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[3.13] gh-87595: Support mmap.size() for anonymous mapping on Unix (GH-24781) #138405

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[3.13] gh-87595: Support mmap.size() for anonymous mapping on Unix (GH-24781) #138405

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4 changes: 4 additions & 0 deletions Doc/library/mmap.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -312,6 +312,10 @@ To map anonymous memory, -1 should be passed as the fileno along with the length

Return the length of the file, which can be larger than the size of the
memory-mapped area.
For anonymous mapping, return its size.

.. versionchanged:: next
Supports anonymous mapping on Unix.


.. method:: tell()
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7 changes: 3 additions & 4 deletions Lib/test/test_mmap.py
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Expand Up @@ -5,7 +5,6 @@
from test.support.os_helper import TESTFN, unlink
from test.support.script_helper import assert_python_ok
import unittest
import errno
import os
import re
import itertools
Expand Down Expand Up @@ -281,9 +280,8 @@ def test_trackfd_parameter(self):
if close_original_fd:
f.close()
self.assertEqual(len(m), size)
with self.assertRaises(OSError) as err_cm:
with self.assertRaises(ValueError):
m.size()
self.assertEqual(err_cm.exception.errno, errno.EBADF)
with self.assertRaises(ValueError):
m.resize(size * 2)
with self.assertRaises(ValueError):
Expand All @@ -308,7 +306,7 @@ def test_trackfd_parameter(self):
def test_trackfd_neg1(self):
size = 64
with mmap.mmap(-1, size, trackfd=False) as m:
with self.assertRaises(OSError):
with self.assertRaises(ValueError):
m.size()
with self.assertRaises(ValueError):
m.resize(size // 2)
Expand Down Expand Up @@ -504,6 +502,7 @@ def test_anonymous(self):
b = x & 0xff
m[x] = b
self.assertEqual(m[x], b)
self.assertEqual(m.size(), PAGESIZE)

def test_read_all(self):
m = mmap.mmap(-1, 16)
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5 changes: 5 additions & 0 deletions Misc/NEWS.d/next/Library/2021-03-07-16-31-36.bpo-43429.Koa0mf.rst
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@@ -0,0 +1,5 @@
The :meth:`~mmap.mmap.size` method of the :class:`mmap.mmap` class now
returns the size of an anonymous mapping on both Unix and Windows.
Previously, the size would be returned on Windows and an :exc:`OSError`
would be raised on Unix.
Raise :exc:`ValueError` instead of :exc:`OSError` with ``trackfd=False``.
10 changes: 9 additions & 1 deletion Modules/mmapmodule.c
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Expand Up @@ -728,7 +728,7 @@ mmap_size_method(mmap_object *self,
#endif /* MS_WINDOWS */

#ifdef UNIX
{
if (self->fd != -1) {
struct _Py_stat_struct status;
if (_Py_fstat(self->fd, &status) == -1)
return NULL;
Expand All @@ -738,6 +738,14 @@ mmap_size_method(mmap_object *self,
return PyLong_FromLong(status.st_size);
#endif
}
else if (self->trackfd) {
return PyLong_FromSsize_t(self->size);
}
else {
PyErr_SetString(PyExc_ValueError,
"can't get size with trackfd=False");
return NULL;
}
#endif /* UNIX */
}

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