[Numpy-discussion] segv PyArray_Check

[Burlen Loring]

Hi David,

Yes, that the situation. using your naming convention, in addtion to 
foo_wrap.c I have another file , say foo_convert.cxx, for massaging 
python data structures into our internal data structures. This source is 
compiled with a c++ compiler so that I can use templates to simplify 
handling the numerous types a user could throw at us. All of the sources 
are linked into the module's .so. I need to use various numpy functions 
in my data conversions functions that live in foo_convert.cxx. For 
example I'm using PyArray_Check because I need to discerne between numpy 
arrays, and python lists and tuples.

What I'm confused about is that calls to numpy funtions from this file 
are segv'ing unless I add another call to import_array() made from 
foo_convert.cxx. I'd like to understand why that's necessary, and why 
the import_array() call in the module's init section in foo_wrap.c 
doesn't have any affect even though it's called first?

Thanks
Burlen

On 11/13/2013 10:48 PM, David Froger wrote:
> Hi Burlen,
>
> SWIG will generate a file named for example foo_wrap.c, which will
> contains a call to import_array() inserted by SWIG because of the
> %init %{
>      import_array();
> %}
> in the SWIG script.
> So in the file foo_wrap.c (which will be compiled to a Python module
> _foo.so), you should be able to used PyArray_Check without segfault.
> Typically, PyArray_Check will be inserted in foo_wrap.c by a typemap,
> for example a typemap from numpy.i .
>
> Do you use PyArray_Check in the foo_wrap.c or in another file? Is
> PyArray_Check in called in another C library, that _foo.so is linked
> with?
>
> David
>
> Quoting Burlen Loring (2013-11-14 02:21:19)
>> Hi,
>>
>> I'd like to add numpy support to an existing code that uses swig. I've
>> changed the source file that has code to convert python lists into
>> native data from c to c++ so I can use templates to handle data
>> conversions. The problem I'm having is a segfault on PyArray_Check
>> called from my c++ source. Looking at things in the debugger the
>> argument passed to it is indeed an intialized python list, my swig file
>> has import_array() in it's init, and I've verified that it is getting
>> called. adding a function in my c++ source to call import_array() a
>> second time prevents the segfault. Could anyone explain why I need the
>> import_array() in both places? If that's the correct way to handle it?
>>
>> Thanks
>> Burlen
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