[QUESTION] pybind11+eigen warning in O2 optimization with gcc

Thanks for maintaining this project. I love it.

When I compile the ode below, mainly involved with the use of Eigen+Pybind11 I have unexpected compilation warnings appearing:

#include <Eigen/Dense>
#include <pybind11/eigen.h>
#include <pybind11/pybind11.h>

namespace py = pybind11;

void foo() {
  py::object val;
  pybind11::cast<Eigen::Vector3d>(val);
}

I compile it with:
g++ -Wall -c -O2 -I $EIGEN_INCLUDE_PATH -I $PYBIND11_INCLUDE_PATH -I $PYTHON_INCLUDE_PATH test.cc
to obtain:

Eigen/src/Core/DenseStorage.h:211:9: warning: ‘<anonymous>’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  211 |         m_data = std::move(other.m_data);

This suggest a temporary object is partially initiallized during the cast (or confuses the compiler)
I am trying to remove such worrying warnings for sanity. Any help is really appreciated.

Information of the system setup:

eigen: 391094c50743f28f9174f455661f650bf07e0177
pybind11: f61855b9d8821e2576960109a2a67379a6c2366f
python-3.8
compiler: g++ (Debian 10.2.1-6) 10.2.1 20210110

Reproduce the report using test.cc, the shown g++ command, and the recorded Eigen, pybind11, Python, and GCC versions. Start by examining the compiler warning through the Eigen/Dense and pybind11/eigen.h includes; done would mean establishing whether the warning is caused by pybind11 and identifying a clear resolution or confirmed upstream cause.