SystemError: <built-in function xxx_iterator> returned a result with an error set

Question

I'm trying to upgrade from: SWIG 2.0.11 and Python 2.7.12 to SWIG 3.0.12 and Python 3.6, but I get the following exception when I run the tests on any iterator (automatically generated using %template):

SystemError: <built-in function xxx_iterator> returned a result with an error set

For example, even the simplest iteration fails:

Traceback (most recent call last):
File "testRender.py", line 459, in testRender
    for v in vertices:
File "ncore.py", line 90833, in __iter__
    return self.iterator()
File "ncore.py", line 90830, in iterator
    return _ncore.Vertices_iterator(self)
SystemError: <built-in function Vertices_iterator> returned a result with an error set

Any ideas?

Again, this was all working great with SWIG 2.0.11 and Python 2.7.12....

Edit: Adding simpler example:

It could be ANY %template-generated iterator, so, for example, this template, defined in the .i file:

%template(Ints) std::list<int>;

will fail when using this simple code:

intsList = ncore.Ints()
intsList.append(1)
intsList.append(2)
for i in intsList:
    print(i)

with a message similar to this:

Traceback (most recent call last):
File "testRender.py", line 459, in testRender
    for i in intsList:
File "ncore.py", line 90833, in __iter__
    return self.iterator()
File "ncore.py", line 90830, in iterator
    return _ncore.Ints_iterator(self)
SystemError: <built-in function Ints_iterator> returned a result with an error set

Answer 1

That is strange, just recompiled everything from scratch. Then I tested your simplified example (if understood correctly):

Mytest.i:

%module mytest                                                                                             
%{                                                                                                       
    #include <list>
     using namespace std;                                                                                     
%}                                                                                                       

%include "std_list.i"
namespace std {                                                                                          
    %template(Ints) list<int>;                                                           
}   

Compile steps:

swig -Wall -c++ -python -py3 -o mytest_wrap.cpp mytest.i
g++ -c -g -ansi mytest_wrap.cpp -I/usr/local/include/python3.6m/ -fPIC -o mytest_wrap.o
g++ -g -ansi -o _mytest.so mytest_wrap.o -shared

Then, after importing mytest module to python, everything works like a charm.

Tested configurations:

• dockerized Ubuntu16.04: Python 3.6.1, SWIG 3.0.12, g++ 5.4.
• dockerized Centos6: Python 3.6.1, SWIG 3.0.12, g++ (4.9.2 and 4.4.7)

Answer 2

Though it's an old question relatively, but recently I encountered a similar issue ( <built-in function delete_qpol_iterator_t> returned a result with an error set ) while dealing with SELinux and setools in CentOS7 docker. Building and installing libsepol and libselinux from source code might solve the problem.

So I guess updating relevant libs and other dependencies might be useful.