c++ trap compilation

收集一下奇奇怪怪的玩意。。。。

虚函数的默认参数

#include <iostream>
using namespace std;

class Base {
public:
    virtual void show(int x = 10) = 0;

    virtual ~Base() { cout << "~Base\n"; }
};


class Derive : public Base {
public:
    void show(int x = 20) override {
        cout << "x = " << x << endl;
    }

    ~Derive() override { cout << "~Derive\n"; }
};

int main(int argc, char* argv[]) {
    Base* bb = new Derive();
    bb->show();
    delete(bb);

    return 0;
}