Debugging Cython code

[Raniere Gaia Silva]

Hi,
how is the easy way to debug a Cython code?

Thanks,
Raniere

[Jason Grout]

On 11/12/12 12:26 PM, Raniere Gaia Silva wrote:
> Hi,
> how is the easy way to debug a Cython code?

I insert print statements, think really hard, insert more print
statements, etc.

I think you can also use gdb; it seems I've done it once before, at least.

Thanks,

Jason

[Robert Bradshaw]

On Mon, Nov 12, 2012 at 12:08 PM, Jason Grout
<jason...@creativetrax.com> wrote:
> On 11/12/12 12:26 PM, Raniere Gaia Silva wrote:
>>
>> Hi,
>> how is the easy way to debug a Cython code?
>
>
> I insert print statements, think really hard, insert more print statements,
> etc.

This is what I typically do.

> I think you can also use gdb; it seems I've done it once before, at least.

See http://wiki.cython.org/DebuggingTechniques and
http://docs.cython.org/src/userguide/debugging.html too.

- Robert

[Nils Bruin]

On Nov 12, 12:08 pm, Jason Grout <jason-s...@creativetrax.com> wrote:
> I think you can also use gdb; it seems I've done it once before, at least.

I have used gdb for stack examination after a segfault. For "C-like"
pieces of Cython it works quite well. For "Python-like" pieces it's
horrible, because python objects are virtually impossible to
investigate with gdb (i.e., C-level). There is the added problem that
gdb will happily give you the source context, but that will refer to
the C that cython produced, not the original ".pyx". That means you
have to deal with mangled identifier names too (which isn't too bad
for C-like cython, which allows an almost 1-1 translation to C).

A thing that would make gdb-debugging of cython immensely more useful
would be if one could set breakpoints in a sensible way. I haven't
used it, but gdb allows setting breakpoints by filename and
linenumber. Those would be ".c" filename and linenumber, though. If we
could somehow have a convenient translation tool from ".pyx" filename
+linenumber to ".c" filename+linenumber, setting breakpoints would be
much more doable. Is this something the cython people have thought
about? Does this need a "cydb" wrapper around gdb or does gdb have its
own customization options that allow something along these lines?

People tend to say that debuggers provide a more efficient
investigation tool than print-and-recompile, but I doubt this is
presently true for cython. Perhaps this can be improved?

[Nils Bruin]

On Nov 12, 12:33 pm, Nils Bruin <nbr...@sfu.ca> wrote:
> Does this need a "cydb" wrapper around gdb or does gdb have its
> own customization options that allow something along these lines?

I should have googled before I replied:

http://docs.cython.org/src/userguide/debugging.html

It would be great if someone would check and report if and how this
can be used for sage and if it works well.

[Raniere Gaia Silva]

Thanks for all the reply.

I hope that anyone know a good way to debug cython "Python-like" code
without using insert print statements.

> I should have googled before I replied:
>
> http://docs.cython.org/src/userguide/debugging.html

Before I post the question I had take a look it the link above but
have not succeeded.

Best regards,
Raniere