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    <p>Add <code>PySys_SetArgv(argc, argv)</code> (along with <code>int argc, char **argv</code> parameters to <code>main</code>), and your code will work.</p> <p><code>tk.Tk()</code> accesses <code>sys.argv</code>, which doesn't exist unless <code>PySys_SetArgv</code> has been called. This causes an exception which gets propagated out of <code>get_ip</code> and reported to Python/C by <code>PyObject_CallObject</code> returning <code>NULL</code>. The <code>NULL</code> gets stored to <code>result</code> and passed to <code>PyString_AsString</code>, which is the immediate cause of the observed crash.</p> <p>Several remarks on the code:</p> <ul> <li><p>It took effort to debug this because the code does no error checking whatsoever, it blindly presses forward until it crashes due to passing NULL pointers around. The least one can do is write something like:</p> <pre><code>if (!ip_module_name) { PyErr_Print(); exit(1); } // and so on for every PyObject* that you get from a Python API call </code></pre> <p>In real code you wouldn't <code>exit()</code>, but do some cleanup and return <code>NULL</code> (or raise a C++-level exception, or whatever is appropriate).</p></li> <li><p>There is no need to call <code>PyGILState_Ensure</code> in the thread that you already know holds the GIL. As the <a href="http://docs.python.org/2/c-api/init.html#PyEval_InitThreads" rel="nofollow">documentation of <code>PyEval_InitThreads</code></a> states, it initializes the GIL and <em>acquires</em> it. You only need to re-acquire the GIL when calling into Python from a C callback that comes from, say, the toolkit event loop that has nothing to do with Python.</p></li> <li><p>New references received from Python need to be <code>Py_DECREF</code>'ed once no longer needed. Reference counting might be omitted from the minimal example for brevity, but it should always be minded.</p></li> </ul>
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    1. COOhhhhh okay. Yeah that made it work. Thank you so much!
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    2. CO@nbsdx No problem. Please note the additional remarks on code style — the bug would have been much easier to catch with good coding practices. In any case, good luck hacking Python/C!
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    3. COYeah, I was in a hurry, and hadn't worked with Python or the Python/C bindings before. I agree 100% with the code style comments. I should be doing error checking, I was just in a hurry haha. Thanks again :)
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