1. const 之 const 型对象只能调用const型成员

#include <iostream>
using namespace std;
class base1
{
    public:
        void fun1a();
    protected:
      
};

int main()
{
    const base1 b0;
    b0.fun1a();
    return 0;
}

g++ -Wall -c "const_initial.cpp" (在目录 E:\1_MYPROJECT\cTest\keyword 中)
const_initial.cpp: In function 'int main()':
const_initial.cpp:14:14: error: passing 'const base1' as 'this' argument of 'void base1::fun1a()' discards qualifiers [-fpermissive]
编译失败。

#include <iostream>
using namespace std;
class base1
{
    public:
        void fun1a() const;
    protected:
      
};

int main()
{
    const base1 b0;
    b0.fun1a();
    return 0;
}

g++ -Wall -c "const_initial.cpp" (在目录 E:\1_MYPROJECT\cTest\keyword 中)
编译成功结束。