New submission from Nicolas Lelong <[email protected]>:
We currently try to run some of our code which relies heavily on ctypes.
We define our C structures the usual way, and then 'augment' them by
subclassing
the C definition. Something along the
lines of :
import ctypes
class cStruct( ctypes.Structure ):
_fields_ = [
( "x", ctypes.c_float )
, ( "y", ctypes.c_float )
]
class pyStruct( cStruct ):
def __init__(self, *args):
super(pyStruct, self).__init__(*args)
Pypy behaviour is different from CPython. The following code runs fine with
CPython :
assert cStruct._fields_ == pyStruct._fields_
a = cStruct()
b = pyStruct()
print "a._fields_ =", a._fields_
print "b._fields_ =", b._fields_
b = pyStruct(1.0, 2.0)
And gives the following output :
a._fields_ = [('x', <class 'ctypes.c_float'>), ('y', <class 'ctypes.c_float'>)]
b._fields_ = [('x', <class 'ctypes.c_float'>), ('y', <class 'ctypes.c_float'>)]
With pypy, it seems that _fields_ is empty for 'b' ; see below. Is this to be
expected ?
Thanks
==
This gives the following output / exception :
a._fields_ = [('x', <class 'ctypes.c_float'>), ('y', <class 'ctypes.c_float'>)]
b._fields_ = []
Traceback (most recent call last):
File "app_main.py", line 72, in run_toplevel
File "D:\rotoglup-scratchpad\experiments\pypy_ctypes\test_struct_inherit.py",
line 18, in <module>
b = pyStruct(1.0, 2.0)
File "D:\rotoglup-scratchpad\experiments\pypy_ctypes\test_struct_inherit.py",
line 11, in __init__
super(pyStruct, self).__init__(*args)
File "D:\pypy\pypy-2.0.2\lib_pypy\_ctypes\structure.py", line 232, in __init__
self.__setattr__(name, arg)
File "D:\pypy\pypy-2.0.2\lib_pypy\_ctypes\structure.py", line 116, in __set__
obj._buffer.__setattr__(self.name, arg)
AttributeError: C Structure has no attribute x
pypy-2.0-beta1.1 failed with another exception :
a._fields_ = [('x', <class 'ctypes.c_float'>), ('y', <class 'ctypes.c_float'>)]
b._fields_ = []
Traceback (most recent call last):
File "app_main.py", line 52, in run_toplevel
File "D:\rotoglup-scratchpad\experiments\pypy_ctypes\test_struct_inherit.py",
line 18, in <module>
b = pyStruct(1.0, 2.0)
File "D:\rotoglup-scratchpad\experiments\pypy_ctypes\test_struct_inherit.py",
line 11, in __init__
super(pyStruct, self).__init__(*args)
File "D:\pypy\pypy-2.0-beta1.1-win32\pypy-2.0-
beta1\lib_pypy\_ctypes\structure.py", line 228, in __init__
raise TypeError("too many initializers")
TypeError: too many initializers
----------
messages: 5762
nosy: pypy-issue, rotoglup
priority: bug
status: unread
title: Problems subclassing from a defined ctypes Structure
________________________________________
PyPy bug tracker <[email protected]>
<https://bugs.pypy.org/issue1498>
________________________________________
_______________________________________________
pypy-issue mailing list
[email protected]
http://mail.python.org/mailman/listinfo/pypy-issue
