[C++-sig] Non-const reference arguments and from_python conversions

[Bilokon, Paul]

Hi all,

I have written a from_python_stream converter for Python streams (like
sys.stdout).

The converter registers itself as follows:

        	boost::python::converter::registry::push_back(
                &convertible,
                &construct,
                boost::python::type_id<_Stream>());

So nothing unusual here. _Stream is the template argument.

Then I do the following:

    StreamConversions::from_python_stream<reference_wrapper<ostream>
>();

Again, nothing unusual here.

I'm testing it on two functions:

void outTest(const ostream & out)
{
	// cout << "Test-----outTest successful" << endl;
}

void outTestRef(ostream & out)
{
	cout << "Test-----outTest successful" << endl;
}

Which are registered like this:

    def("outTest", outTest);
    def("outTestRef", outTestRef);

Obviously I need outTestRef to work. Otherwise I can't use operator<<,
so what's the point.

Unfortunately, outTest works, outTestRef does not work:

outTest(sys.stderr) # works
outTestRef(sys.stderr) # fails

The error is:

  File "proto_test.py", line 23, in <module>
    outTestRef(sys.stderr)
Boost.Python.ArgumentError: Python argument types in
    pyamp.proto.outTestRef(file)
did not match C++ signature:
    outTestRef(class std::basic_ostream<char,struct
std::char_traits<char> > {lvalue})

Hence the question: is there absolutely no support for non-const
reference arguments?

Many thanks for your help!

Regards,
Paul
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