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Hi all,
I found a bug in the exception handler. When I
start the app without any arguments I get an
output I expect:
__main__:2:DeprecationWarning: Deprecated function.
When I run the app with arguments, the arguments
are printed somehow in the exception output:
-test=HALLO:1:DeprecationWarning: Deprecated function
Can anyone please confirm?
Bye, Seb
[code]
#include "Python/Python.h"
static PyObject *testfunc(PyObject *self, PyObject *args, PyObject *keywords)
{
	PyErr_Warn(PyExc_DeprecationWarning, "Deprecated function.");
	Py_RETURN_NONE;
}
static PyMethodDef testmod[] =
{		
	{"testfunc", (PyCFunction)testfunc, METH_NOARGS, "Prints out a text to stdout."},
	{NULL}
};
int main (int argc, char **argv)
{
	Py_Initialize();
	
	PySys_SetArgv(argc, argv);
	
	PyObject *mod = Py_InitModule4("testmod", testmod, "", NULL, PYTHON_API_VERSION);
	if(mod == NULL) return -1;
	
	PyRun_SimpleString(	"import testmod\n"
											"testmod.testfunc()");
	Py_Finalize();
	return 0;
}
[/code]

Could anyone please correct the title? Thx :)

Yes, the warnings module tries to display the file name. Inside PyRun_SimpleString(), globals()['__name__'] == '__main__', and the warnings module supposes that argv[1] is the name of the script.
I wonder whether __file__ would be more accurate: it is filled when running a script, but not when running a string. And sys.argv would not be used any more.

Oh, damn. I really forgot the argv filename thing. Nevermind :)
But back to topic. __file__ might be not the best solution for that. What does Python when embedded, and __file__ is not set? That can happen when the source of your code is not a file (multiline textbox, ...)
I would simply follow the way how the traceback solves this. Just print out the filename passed to:
Py_CompileStringFlags(const char *str, const char *filename, int start, PyCompilerFlags *flags)
PyRun_SimpleFileExFlags(FILE *fp, const char *filename, int closeit, PyCompilerFlags *flags)
[...]

attached a patch for this issue now.
Now it first uses the name of the script,
instead of __file__.

any news on this?

First of all, your patch needs a test.

Fixed in bpo-33375.
commit 11a896652ee98aa44e59ed25237f9efb56635dcf
Author: Thomas Kluyver <takowl@gmail.com>
Date: Fri Jun 8 21:28:37 2018 +0200
 bpo-33375: Get filename for warnings from frame.f_code.co_filename (GH-6622)
 
 More consistent with how other parts of Python find the filename (e.g. tracebacks and pdb).