[Swig-devel] [ swig-Bugs-1727629 ] RuntimeError in garbage collection with shadowed functions

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Bugs item #1727629, was opened at 2007-05-29 10:40
Message generated for change (Comment added) made by lukemoore
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Category: python
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Luke Moore (lukemoore)
Assigned to: Marcelo Matus (marcelomatus)
Summary: RuntimeError in garbage collection with shadowed functions

Initial Comment:
When swig wraps the following overloaded functions:
    foo(const std::vector<float>& values);
    foo(const std::vector<std::string>& values);
the wrapper code it generates calls swig::asptr() to check if the argument is a vector of floats or a vector of strings.  However, if swig::asptr() fails, it raises a Python RuntimeError that often isn't apparent until garbage collection occurs.

Attached is an example illustrating the problem.  It wraps the above functions into a module named shadow, and then runs the following:

luke@lasalle:~/shadow_problem$ python2.5
Python 2.5.1 (r251:54863, Apr 25 2007, 21:31:46) 
[GCC 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import gc
>>> import shadow
>>> shadow.foo(("one", "two"))
one two 
>>> gc.collect()
Exception exceptions.RuntimeError: 'in sequence element 0' in 'garbage collection' ignored
Fatal Python error: unexpected exception during garbage collection
Aborted
luke@lasalle:~/shadow_problem$ 

The run_it.sh script in the tarball will invoke swig, compile the shared object, and invoke Python.

I'm using swig 1.3.31 and gcc 4.1.3 on Debian unstable.

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>Comment By: Luke Moore (lukemoore)
Date: 2007-05-29 10:44

Message:
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Originator: YES

I was able to avoid the RuntimeError by changing
swig::traits_asptr_stdseq::asptr to pass false to PySequence_Cont::check()
so it doesn't set the error.  I don't know if this is the proper fix,
though.

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