ImportError for newer pybind11 versions

[h-larsson]

Hi Huanchen,

It looks like Pybind Version >= 2.10.2 introduces the error

ImportError: generic_type: cannot initialize type "KeysView[Tuple[str, int]]": an object with that name is already defined

Which seems to be due to pybind/pybind11#4353
Do you have an idea how to fix this?

[hczhai]

Yes that's why I restricted the version number here: https://github.com/block-hczhai/block2-preview/blob/master/setup.py#L170
I will have a look at the link and see if I can fix it.

[hczhai]

Hi, I think this is a bug introduced in pybind11==2.10.2 due to the pull request you mentioned, and it is not solved even in the newest version pybind11==2.10.4. You can get the error using the following minimal example:

#include <pybind11/numpy.h>
#include <pybind11/pybind11.h>
#include <pybind11/stl_bind.h>
#include <map>
#include <string>

namespace py = pybind11;
using namespace std;

PYBIND11_MODULE(xtest, m) {
    m.doc() = "xtest.";
    py::bind_map<map<int, int>>(m, "xx");
    py::bind_map<map<long long int, int>>(m, "yy");
}

Save this file as xtest.cpp and you can compile it using

g++ -O3 -Wall -shared -std=c++11 -fPIC $(python3 -m pybind11 --includes) xtest.cpp -o xtest$(python3-config --extension-suffix)

And then if you do python -c 'import xtest' you get the following

ImportError: generic_type: cannot initialize type "KeysView[int]": an object with that name is already defined

Now if you change the two lines to

    py::bind_map<map<int, double>>(m, "xx");
    py::bind_map<map<long long int, int>>(m, "yy");

You get even strange warnings at compile time. So there is nothing I can do to fix this. Let's just give up the version >=2.10.2.

[hczhai]

This is basically pybind/pybind11#4529

[h-larsson]

Thanks for checking this. Hopefully they will resolve it soon.

[Tobias-Fischer]

Have you found a workaround for this?

[hczhai]

@Tobias-Fischer @h-larsson The issue was fixed in pybind/pybind11#4985.