类型转换

    // static_cast<>

    // 1. 内置对象
    int a = 97;
    char c = static_cast<char>(a); // OK
    cout << c << endl;
    // 2. 自定义类型对象
    // Building bb;
    // Animal aa = static_cast<Animal>(bb); // error: no matching function for call to ‘Animal::Animal(Building&)’
    // 3. 不同类型的指针转换
    // int *p = &a;
    // char *pc = static_cast<char*>(p); // error: invalid static_cast from type ‘int*’ to type ‘char*’
    // cout << pc << endl;
    // Animal * pa = NULL;
    // Building *pb = static_cast<Building*>(pa); // error: invalid static_cast from type ‘Animal*’ to type ‘Building*’
    // 4. 有继承关系的指针或引用
    Animal * pa = NULL;
    Cat *pc = static_cast<Cat*>(pa);  // OK
    pa = static_cast<Animal*>(pc); // OK

    // dynamic_cast<>

    // 1. 内置对象
    // c = dynamic_cast<char>(a); // error: cannot dynamic_cast ‘a’ (of type ‘int’) to type ‘char’ (target is not pointer or reference)
    // 2. 非继承关系指针
    // Building *pb = dynamic_cast<Building*>(pa); // error: cannot dynamic_cast ‘pa’ (of type ‘class Animal*’) to type ‘class Building*’ (source type is not polymorphic)
    // 3. 继承关系指针会做安全检查，只能将子类指针转为父类指针
    // pc = dynamic_cast<Cat*>(pa); // error: cannot dynamic_cast ‘pa’ (of type ‘class Animal*’) to type ‘class Cat*’ (source type is not polymorphic)
    pa = dynamic_cast<Animal*>(pc); // OK

int i = 0;
int *a = &i
const int* b = const_cast<const int*>(a);
const int* bb = a; // OK
a = const_cast<int*>(b); // OK
a = b;  // error: invalid conversion from ‘const int*’ to ‘int*’ [-fpermissive]