C API PyObject_Call segfaults with string

[Jen Kris]

With the help of PyErr_Print() I have it solved.  Here is the final code (the part relevant to sents):

   Py_ssize_t listIndex = 0;
   pListItem = PyList_GetItem(pFileIds, listIndex);
   pListStrE = PyUnicode_AsEncodedString(pListItem, "UTF-8", "strict");
   pListStr = PyBytes_AS_STRING(pListStrE); // Borrowed pointer

   // Then:  sentences = gutenberg.sents(fileid) - this is a sequence item
   PyObject *c_args = Py_BuildValue("s", pListStr);
   PyObject *args_tuple = PyTuple_New(1);
   PyTuple_SetItem(args_tuple, 0, c_args);

   pSents = PyObject_CallObject(pSentMod, args_tuple);

   if ( pSents == 0x0){
       PyErr_Print();
       return return_value; }

As you mentioned yesterday, CallObject needs a tuple, so that was the problem.  Now it works.  

You also asked why I don't just use pListStrE.  I tried that and got a long error message from PyErr_Print.  I'm not far enough along in my C_API work to understand why, but it doesn't work.  

Thanks very much for your help on this.  

Jen


Feb 9, 2022, 17:40 by songofacandy at gmail.com:

> On Thu, Feb 10, 2022 at 10:37 AM Jen Kris <jenkris at tutanota.com> wrote:
>
>>
>> I'm using Python 3.8 so I tried your second choice:
>>
>> pSents = PyObject_CallFunctionObjArgs(pSentMod, pListItem);
>>
>> but pSents is 0x0.  pSentMod and pListItem are valid pointers.
>>
>
> It means exception happened.
> If you are writing Python/C function, return NULL (e.g. `if (pSents ==
> NULL) return NULL`)
> Then Python show the exception and traceback for you.
>
> -- 
> Inada Naoki  <songofacandy at gmail.com>
>