Cython: registering a Python function for callback in a DLL

Question

I'm trying to register a Python function for callback in a DLL written in C++ and I can't figure out how to do it.

My C++ code header looks like:

extern "C" {
    __declspec(dllexport) void RegisterFunc((void (*)());
 }

And the implementation is:

void (*funcCallback)() = NULL;
__declspec(dllimport) void RegisterFunc(void(*func)())
{
    funcCallback = func;
}

My Cython pyx file looks like:

cdef extern void RegisterFunc(void (*)())

def PyRegisterFunc(func):
    RegisterFunc(func)

When compiled this gives the error message: Cannot convert Python object to 'void (*)(void)'

If I change the code to:

def PyRegisterFunc(func):
    RegisterFunc(<void (*)()>func)

I get the error message: Python objects cannot be cast to pointers of primitive types

I've also tried &func and get the error message: Cannot take address of Python variable.

What is the correct way of passing this Python function as a pointer to my C code?

UPDATE: I should mention my intended purpose for this Python function. The Python application is written in PyQt and the function will emit a signal. The DLL itself has no knowledge of Qt and is compiled without the Qt libraries. A method in the DLL will call this function indirectly which will emit a signal to the Python application.

Answer 1

请参阅 Cython 文档： 使用来自 C 的 Cython 声明