Use dynamic_pointer_cast to avoid bad_weak_ptr

shared_from_this.cpp

#include <memory>
#include <iostream>
#include <type_traits>
#include <typeinfo>
#include <string>

struct Executor;
struct Intepreter;
struct Executor1 {
  Executor1(const std::shared_ptr<Executor>& executor,
            int x): parent(executor) {
    std::cout << x << std::endl;
  }
  std::shared_ptr<Executor> parent;
};

struct Backend: public std::enable_shared_from_this<Backend> {
  virtual ~Backend() {}
  virtual void run() = 0;
};

struct Executor: public Backend {
  const int data = 10;
  virtual void run() override {
    Executor1 x(std::dynamic_pointer_cast<Executor>(shared_from_this()), data);
  }
};

struct Intepreter: public Backend {
  const int data = 9;
  virtual void run() override {
    // Executor1 x(shared_from_this(), data);
  }
};

std::unique_ptr<Backend> createBackend(int k = 0) {
  if (k == 0) {
    return std::make_unique<Executor>();
  }
  else {
    return std::make_unique<Intepreter>();
  }
}

class MainInstance {
private:
  std::shared_ptr<Backend> backend;
public:
  MainInstance(): backend(createBackend()) {
    backend->run();
  }
};

int main() {
  MainInstance m;
  std::unique_ptr<Backend> b = createBackend();
  return 0;
}