problem using ctypes with MMX intrinsics

[Diez B. Roggisch]

Robert Kern schrieb:
> dcharno wrote:
>> Is it possible to use ctypes with a shared library which uses MMX/SSE 
>> intrinsics?  I can load the library and access functions inside it, 
>> but I getting a seg fault when I hit one of the intrinsics.  I'm 
>> wondering if there might be some sort of stack alignment problem.
>>
>> I am using gcc version 4.2.3 and Python 2.5.2 on Ubuntu 8.04.
>>
>> Any suggestions would be helpful.
> 
> Well, stack alignment would be a problem with how the shared library 
> gets compiled, nothing to do with ctypes (I think). However, if you are 
> passing in arrays from ctypes, *they* may also be misaligned. Try to 
> check the addresses of the ctypes values you are passing in. I'm not 
> entirely sure how to do that, though.

there is the addressof-function. If this is really the problem, it 
should be possible to allocate data + margin (e.g. c_int-arrays), and 
cast the proper aligned address via from_address.

Diez