ctypes question

[MrJean1]

It is not entirely clear what the functions and especially what their
signatures are in that C library clibsmi.

In general, for shared libraries, you need to define those first as
prototype using ctypes.CFUNCTYPE() and then instantiate each prototype
once supplying the necessary parameter flags using
prototype(func_spec, tuple_of_param_flags).  See sections 15.16.2.3
and 4 of the ctypes docs*.

Take a look the Python bindings** for the VLC library, the file called
vlc.py***.  The function _Cfunction is used to create the Python
callable for each C function in that VLC library.  All the Python
callables are in the second half of the vlc.py file, starting at line
2600.

Hope this helps,

/Jean

*) <http://docs.python.org/library/ctypes.html#foreign-functions>

**) <http://wiki.videolan.org/Python_bindings>

***) <http://git.videolan.org/?p=vlc/bindings/
python.git;a=tree;f=generated;b=HEAD>


On Dec 10, 3:32 pm, News Wombat <newswom... at gmail.com> wrote:
> Hi everyone,
>
> I've been experimenting with the ctypes module and think it's great.
> I'm hitting a few snags though with seg faults.  I attached two links
> that holds the code.  The line i'm having problems with is this,
>
> sn=clibsmi.smiGetNextNode(pointer(sno),SMI_NODEKIND_ANY)
>
> It will work one time, and if I call it again with the result of the
> previous, even though the result (a c struct) looks ok, it will
> segfault.  I think it's a problem with pointers or maybe the function
> in the c library trying to change a string that python won't let it
> change.  I'm stuck, any tips would be appreciated.  Thanks, and Merry
> Christmas!
>
> constants.py:http://pastebin.com/HvngjzZN
> libsmi.py:http://pastebin.com/19C9kYEa