Passing empty buffer as default argument

[mdorier]

I have a code that looks like the following:

    .def("send", [](..., py::buffer& header) {
       ...
    }, ..., "header"_a=py::buffer())

What I want to do here is pass, as default argument, an empty buffer (something that would have a size of 0 when requesting its buffer_info). However the code above fails when the module is imported, with the following exception:

ImportError: arg(): could not convert default argument into a Python object (type not registered yet?). Compile in debug mode for more information.

Note that I'm able to use py::buffer as argument without any problem. It's only when I try to use it as a default value for a parameter that the exception is raised.

Is that a bug? If not, how can I provider a default "empty buffer" argument to such a function?

Note: I would like to avoid using py::object as argument that I would cast into a py::buffer into the function, and handle None as an empty buffer, because I have other overloads of this function (for instance one that takes an std::string instead of a py::buffer).