New submission from Pauli Virtanen <[email protected]>:
Currently on Python 3.x:
>>> import ctypes
>>> memoryview(ctypes.c_long()).format
'<l'
This is invalid on 64-bit platforms: the above means 32-bit little-endian
float. The '<' endian specification turns on the "standard size" mode
(similarly as for the struct module), which makes type character have a
platform-independent meaning.
Unfortunately, the struct module format syntax does *not* allow specifying
native-size non-native-endian items. So just replacing '<' by '^' cannot be in
general be done.
Suggested fix attached. It adds a converter function that maps the
platform-dependent ctypes codes to struct module standard-size codes; handling
c_long and c_bool specially.
***
After this patch (and the one in http://bugs.python.org/issue10744 ):
>>> import numpy as np
>>> from ctypes import *
>>> class Point(Structure):
... _fields_ = [("x", c_long), ("y", c_long)]
...
>>> class StructWithArrays(Structure):
... _fields_ = [("x", c_long * 3 * 2), ("y", Point * 4)]
...
>>> x = StructWithArrays()
>>> y = np.asarray(x)
>>> y.dtype
dtype([('x', '<i8', (2, 3)), ('y', [('x', '<i8'), ('y', '<i8')], (4,))])
>>> y['x'] = [[1,2,3],[4,5,6]]
>>> y['y']['x'] = np.arange(4) + 10
>>> y['y']['y'] = np.arange(4) + 20
>>> x.x[0][0]
1
>>> x.x[0][1]
2
>>> x.x[0][2]
3
>>> x.y[0].x
10
>>> x.y[1].x
11
>>> x.y[0].y
20
>>> x.y[1].y
21
----------
files: 001-ctypes-fix-pep-3118-type-codes-for-c-long-and-c-bool.patch
keywords: patch
messages: 124411
nosy: pv
priority: normal
severity: normal
status: open
title: ctypes c_long & c_bool have incorrect PEP-3118 type codes
Added file:
http://bugs.python.org/file20124/001-ctypes-fix-pep-3118-type-codes-for-c-long-and-c-bool.patch
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Python tracker <[email protected]>
<http://bugs.python.org/issue10746>
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