Bugs item #1701409, was opened at 2007-04-16 12:45
Message generated for change (Comment added) made by theller
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Category: Extension Modules
Group: None
Status: Open
Resolution: None
Priority: 7
Private: No
Submitted By: sebastien Martini (seb_martini)
Assigned to: Thomas Heller (theller)
Summary: Segfault in c_char_p of ctypes
Initial Comment:
Hi,
I experienced a segmentation fault (when providing a wrong argument type to
c_char_p) in the ctypes module under Linux and with the version 2.5 .
sundae:~$ python
Python 2.5.1c1 (release25-maint, Apr 6 2007, 22:02:36)
[GCC 4.1.2 (Ubuntu 4.1.2-0ubuntu4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from ctypes import *
>>> c_char_p(42)
zsh: segmentation fault (core dumped) python
sundae:~$
Regards,
Sebastien Martini
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>Comment By: Thomas Heller (theller)
Date: 2007-04-18 21:20
Message:
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This is a difficult issue. The integer (which is interpreted as address)
is allowed because some libraries use 'char *' pointers initialized to
small, invalid addresses for special purposes.
On windows, printing a c_char_p(42) does not crash, it raises a ValueError
instead:
>>> from ctypes import *
>>> c_char_p(42)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid string pointer 0x00B20B48
>>>
Windows does this by checking if there is a valid string at the address
(see Modules/_ctypes/cfield.c, line 1366) by calling the IsBadStringPointer
api function. Do other platforms have a function that can do this check?
If not, I'm afraid we would have to give up on the very convenient repr of
'normal' c_char_p instances:
>>> c_char_p("foo bar")
c_char_p('foo bar')
>>>
and only print the address (at least on non-windows).
----------------------------------------------------------------------
Comment By: Neal Norwitz (nnorwitz)
Date: 2007-04-18 09:37
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Thanks for the bug report Sebastien.
This bug occurs in 2.5 and in the trunk, so it's not a regression.
Thomas, could you take a look? Integers are specifically allowed here
(floats are not). The problem is when trying to print the repr:
#0 PyString_FromString (str=0x2a <Address 0x2a out of bounds>) at
Objects/stringobject.c:108
#1 z_get (ptr=0x2ae1aa9d6450, size=8) at Modules/_ctypes/cfield.c:1373
#2 Simple_get_value (self=0x2ae1aa9d63f8) at
Modules/_ctypes/_ctypes.c:4007
#3 Simple_repr (self=0x2ae1aa9d63f8) at Modules/_ctypes/_ctypes.c:4095
#4 PyObject_Repr (v=0x2ae1aa9d63f8) at Objects/object.c:361
----------------------------------------------------------------------
Comment By: sebastien Martini (seb_martini)
Date: 2007-04-16 21:40
Message:
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Originator: YES
c_wchar_p also contains this bug.
----------------------------------------------------------------------
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