Python C/API simple debugging

[k3xji]

On Nov 26, 1:43 pm, "Diez B. Roggisch" <de... at nospam.web.de> wrote:
> k3xji wrote:
> > On Nov 26, 1:34 pm, Stefan Behnel <stefan... at behnel.de> wrote:
> >> k3xji wrote:
> >> > I am new to Python C API and finding it difficult to debug C
> >> > extensions. So, basically I want to see the value of an integer value
> >> > during the C API. Here is the code:
>
> >> > #define LAST_MIX_VAL 0xDEADBEEF
>
> >> > static PyObject *
> >> > chash(PyObject *self, PyObject *args)
> >> > {
> >> > unsigned int key,result; //treat key like an usinged int.
> >> > unsigned char a,b,c,d;
>
> >> > key = result = 0;
> >> > if (!PyArg_ParseTuple(args, "i", &key))
> >> > return NULL;
>
> >> > printf("Key:%i\n",Py_BuildValue("i", key));
> >> > .
> >> > .
> >> > [...]
> >> > - What is the preffered approach for these kind simple-debugging
> >> > issue?
>
> >> If you want to simplify this kind of debugging as well as the general
> >> code writing itself, consider using Cython.
>
> >>http://cython.org/
>
> >> Apart from that, I'd use gdb for debugging these things. It does have a
> >> learning curve, but in change gives you a lot more than just
> >> "print-debugging".
>
> >> Stefan
>
> > OK.
>
> > How to use gdb? I am compiling the extension to a "pyd" file and
> > importing it right now. So, I assume we need to, somehow load the
> > extension dynamically for debugging? But how?
>
> You write a testscript that exposes the error you want to observe in the
> C-layer.
>
> Then you do
>
> $ gdb python
> # set args testscript.py
> # break <some breakpoint, see how to enter that in gdb-docs>
> # run
>
> That pretty much is it. You can't single-step python code this way, but you
> can walk through C/C++-code.
>
> Diez

OK I see your point, I just expected an another way to do that from
distutils itself. Thanks for the answer.

By the way for simple print-debugging, below works right now, I forgot
to try that
fprintf(stderr,"%d", key);

Thanks all again