virtual inheritance problem

[jcpryan]

When moving from version 2.0.1 to 2.2.1, compiled using both visual studio 2015 and 2019, I encountered an error

Run-Time Check Failure #0 - The value of ESP was not properly 
saved across a function call.  This is usually a result of 
calling a function declared with one calling convention with 
a function pointer declared with a different calling convention.

in code that had virtual inheritance. Here is a simplified example that illustrates the issue:

struct A0 {
virtual int size() const = 0;
int non_virtual() const { return 2; }
};
struct A1 : public virtual A0 {
int size() const { return 1; }
};
inline void A_test(const A0& a) {
std::cout << a.non_virtual() << std::endl;
std::cout << a.size() << std::endl;
}

PYBIND11_PLUGIN(virtual_test) {
pybind11::module m("virtual_test", "virtual test extension module");
pybind11::class_(m, "A0")
.def("size", &A0::size)
.def("non_virtual", &A0::non_virtual);
pybind11::class_<A1, A0>(m, "A1")
.def(py::init<>());
m.def("A_test", A_test);
}

and in the python script

a1 = A1()
A_test(a1)
print 'done'

With virtual inheritance, thd code only prints
2
then crashes, but correctly prints
2
1
done
when the virtual keyword is removed.

Thanks,
jcr

[jcpryan]

It seems I just need to change
class_<A1, A0>(m, "A1")
to
class_<A1, A0>(m, "A1", multiple_inheritance())
even though the eventual class that uses multiple inheritance is not wrapped.
I'm not sure why it worked in 2.0.1.
Regards,
jcr

[bstaletic]

Seems like this issue is resolved. @jcpryan Thanks for providing the answer.