ValueError: PyCapsule_SetPointer called with null pointer

[Stolb27]

on call kerberos.authGSSServerClean(context)

Cause:

if PY_MAJOR_VERSION >= 3

    PyCapsule_SetPointer(pystate, NULL);

else

in authGSSServerClean in kerberos.c

Documentation:
int PyCapsule_SetPointer(PyObject *capsule, void *pointer)
Set the void pointer inside capsule to pointer. The pointer may not be NULL.
https://docs.python.org/3.4/c-api/capsule.html#capsules

[02strich]

Thanks for raising this point. I have not found a nice and backwards compatible way to address this issue and welcome any ideas. Conceptually I would convert the clean functions to destructors of the pyCapsule state, but I am not sure this behaves the same.

Alternatively, one could remove the line and depend on the Python application not calling the clean function twice, which would be even worse.

[Stolb27]

http://svn.python.org/projects/python/trunk/Objects/capsule.c
When the number of references to an python object becomes equal to zero, the function from pointer tp_dealloc is called. In the case of PyCapsule object, there is pointer to capsule_dealloc function.
static void capsule_dealloc(PyObject *o)
{
PyCapsule *capsule = (PyCapsule *)o;
if (capsule->destructor) {
capsule->destructor(o);
}
PyObject_DEL(o);
}
Consequently, in the case of using PyCapsule, nothing to do. Right?

[laurivosandi]

Hi, facing the same issue here with Python3. Currently the only workaround is commenting out authGSSServerClean lines?

[Stolb27]

Hi. I made the fork https://github.com/Stolb27/pykerberos, which, I think, has solved this problem. But I'm not sure I do the right thing, to offer pull-request. It might be not to remove clean-methods, leaving them empty and marking depricated. 02strich, this solution is suitable for pull-request?

[02strich]

I will have a look at it tonight. Just for my education, can you explain what exact kind of issue where you facing on Py3? Compiler issues?
On Oct 26, 2015, at 15:23, Lauri Võsandi <notifications@git.luolix.topmailto:notifications@github.com> wrote:

Hi. I made the fork https://github.com/Stolb27/pykerberos, which, I think, has solved this problem. But I'm not sure I do the right thing, to offer pull-request. It might be not to remove clean-methods, leaving them empty and marking depricated. 02strich, this solution is suitable for pull-request?

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/6#issuecomment-151301861.

[02strich]

@Stolb27 glancing over the code that looks very interesting. If you are ok with it, let's get a pull request going and see where we get to?

[laurivosandi]

Hi again, I get "PyCapsule_SetPointer called with null pointer" errors whenever I have authGSSServerClean in my code. Interestingly the exceptions are not raised by authGSSServerClean but by arbitrary statements in the code. I'm sure that authGSSServerClean is not being called twice and I am not referencing to the objects after calling authGSSServerClean.

[02strich]

Hi,

I am sorry for taking so long to get back to this. @Stolb27 your changes are very interesting and I incorporated some of them into master here - can you have a look?

@laurivosandi can you try head of master, it should fix your issue?

[Stolb27]

Omg...
Are you sure you want to call a method with the O-option in the format string of method Py_BuildValue? I think the reference count is not decremented to zero and the destructor will not work. You may need to use the N-option (according to https://docs.python.org/3/c-api/arg.html#building-values).
PS. There are a few warnings when building the library, I solved my request. Maybe these changes also accept?
PS2. Similarly, the file test.py is not compatible with py3.

[02strich]

Thanks for the hint with the N vs O, that is actually also broken upstream. Also fixed the warnings and the test.py. What other changes did you have in mind?

[Stolb27]

Thank you. Everything is fine:)

Perhaps this is a separate issue, but ... In Debian 8 krb5-config has been renamed to krb5-config.mit (don't know, why).

(env) user@debian:~/development/kerberos-test/pykerberos$ python setup.py build
Traceback (most recent call last):
  File "setup.py", line 31, in check_krb5_config
    process = subprocess.Popen(("krb5-config",) + options, stdout=subprocess.PIPE, universal_newlines=True)
  File "/usr/lib/python3.4/subprocess.py", line 859, in __init__
    restore_signals, start_new_session)
  File "/usr/lib/python3.4/subprocess.py", line 1457, in _execute_child
    raise child_exception_type(errno_num, err_msg)
FileNotFoundError: [Errno 2] No such file or directory: 'krb5-config'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "setup.py", line 50, in <module>
    extra_link_args = check_krb5_config("--libs", "gssapi")
  File "setup.py", line 42, in check_krb5_config
    raise Exception("You are missing krb5-config")
Exception: You are missing krb5-config

Can you somehow solve?

[02strich]

Can you check whether the new master HEAD solves the debian problem?

[Stolb27]

Yes, there is no more error. Thank you.

вт, 15 дек. 2015 г., 15:27, Stefan Richter notifications@github.com:

Can you check whether the new master HEAD solves the debian problem?

—
Reply to this email directly or view it on GitHub
#6 (comment).

С уважением, Василий Иванов

[02strich]

Thanks for your help. I have pushed the changes into v1.1.9 and uploaded the new version to PyPi