python::boost 模块优于别名：RecursionError

Question

所以我正在使用 python boost。我的目标是能够从 python 模块重载 c++ 函数。我已经做到了，但在使用别名时我观察到了奇怪的行为。

我重新创建了一个基本示例来重现该错误：

#include <boost/python.hpp>
#include <iostream>
#include <string>

// CppBase class
class CppBase {
 public:
  CppBase(){};  // Default constructor

  virtual std::string myOverridableCallback() {
    return "Callback triggered from CppBase";  // Default implementation
  }

  virtual void display() {
    std::cout << "CppBase class display function" << std::endl;
    std::cout << this->myOverridableCallback() << std::endl;
  }
};

// CppBase class WRAPPER
struct CppBaseWrap : public CppBase, boost::python::wrapper<CppBase> {
 public:
  virtual std::string myOverridableCallback() override {
    // Check if override is provided in Python
    if (boost::python::override f =
            this->get_override("myOverridableCallback")) {
      return f();  // Call the Python version
    }
    return CppBase::myOverridableCallback();  // Call the Default implementation
  }
};

// CppDerived class
class CppDerived : public CppBase {
 public:
  CppDerived() {}  // Default constructor

  void show() {
    std::cout << "CppDerived class show function" << std::endl;
    std::cout << this->myOverridableCallback() << std::endl;
  }
};

using CppDerivedCopy = CppDerived;

// CppDerived class WRAPPER
struct CppDerivedWrap : public CppDerived, boost::python::wrapper<CppDerived> {
  virtual std::string myOverridableCallback() override {
    // Check if override is provided in Python
    if (boost::python::override f =
            this->get_override("myOverridableCallback")) {
      return f();  // Call the Python version
    }
    return CppBase::myOverridableCallback();  // Call the Default implementation
  }
};

BOOST_PYTHON_MODULE(InheritedFunctionTest) {
  // Expose the CppBase class
  boost::python::class_<CppBaseWrap, boost::noncopyable>("CppBase", boost::python::init<>())
      .def("myOverridableCallback", &CppBaseWrap::myOverridableCallback)
      .def("display", &CppBase::display);

  // Expose the CppDerived class
  boost::python::class_<CppDerivedWrap, boost::python::bases<CppBase>, boost::noncopyable>("CppDerived", boost::python::init<>())
      .def("myOverridableCallback", &CppDerived::myOverridableCallback)
      .def("show", &CppDerived::show);

  // Expose the CppDerivedCopy class
  boost::python::class_<CppDerivedWrap, boost::python::bases<CppBase>, boost::noncopyable>("CppDerivedCopy", boost::python::init<>())
      .def("myOverridableCallback", &CppDerivedCopy::myOverridableCallback)
      .def("show", &CppDerivedCopy::show);
}

所以如你所见，我有

using CppDerivedCopy = CppDerived;

。我的想法是能够在 python 中实现

from InheritedFunctionTest import CppDerivedCopy

并具有与

CppDerived

完全相同的行为。

我的代码可以编译，这是我的 python 基本示例：

import sys
sys.path.append('./build')
import InheritedFunctionTest


derived_obj = InheritedFunctionTest.CppDerived()
derived_obj.show()  # Calls show from Derived and myCallback from CppBase

derived_obj2 = InheritedFunctionTest.CppDerivedCopy()
derived_obj2.show()  # Calls show from Derived and myCallback from CppBase

这将触发以下错误：

Traceback (most recent call last):
  File "test_script.py", line 13, in <module>
    derived_obj.show()  # Calls show from Derived and myCallback from CppBase
RecursionError: maximum recursion depth exceeded while calling a Python object

所以这里

InheritedFunctionTest.CppDerived()

触发了这个错误。这里出现了奇怪的行为，如果在我的 cpp 代码中，我在

CppDerivedCopy

之前暴露了

CppDerived

（因此只需反转 c++ 文件中的最后 2 个代码块），我会遇到相同的错误，但在

InheritedFunctionTest.CppDerivedCopy() 上

对象，并且

InheritedFunctionTest.CppDerived()

对象没有引起任何问题。

因此，两个声明中的最后一个不会有问题，而第一个声明将出现此 RecursionError。

我尝试了很多不同的方法，但我没有找到问题的根源，chatGPT 也没有，谷歌也没有给我太多文档。任何帮助将不胜感激 ！！ 谢谢

Answer 1

请测试下面提供的修改后的 Boost.Python 代码，看看它是否解决了递归错误。确保使用以下更改替换现有代码：

1. 在

   call

   函数中使用

   get_override

   代替

   myOverridableCallback

   。

virtual std::string myOverridableCallback() override {
  namespace bp = boost::python;
  bp::object pyOverride = this->get_override("myOverridableCallback");
  if (pyOverride) {
    return bp::extract<std::string>(pyOverride());
  }
  return CppBase::myOverridableCallback();
}
// Expose the CppBase class
boost::python::class_<CppBaseWrap, boost::noncopyable>("CppBase", boost::python::init<>())
    .def("display", &CppBase::display);

// Expose the CppDerived class
boost::python::class_<CppDerivedWrap, boost::python::bases<CppBase>, boost::noncopyable>("CppDerived", boost::python::init<>())
    .def("myOverridableCallback", &CppDerived::myOverridableCallback)
    .def("show", &CppDerived::show);
// Expose the CppBase class
boost::python::class_<CppBaseWrap, boost::noncopyable>("CppBase", boost::python::init<>())
    .def("display", &CppBase::display)
    .def("myOverridableCallback", &CppBase::myOverridableCallback);

// Expose the CppDerived class
boost::python::class_<CppDerivedWrap, boost::python::bases<CppBase>, boost::noncopyable>("CppDerived", boost::python::init<>())
    .def("show", &CppDerived::show);