相关疑难解决方法(0)

令我感到惊讶的是,在下面的示例中,声明Middle的基类private使该名称在后续派生中不可用作为类型.

class Base {
public:
  Base(Base const& b) : i(b.i) {}

  int i;
};

class Middle : private Base {            //<<<<<<<<<<<
public:
  Middle(Base const* p) : Base(*p) {}
};

class Upper : public Middle {
public:
  Upper(Base const* p) : Middle(p) {}    //<<<<<<<<<<<
};

用g ++编译(Debian 6.3.0-18 + deb9u1)6.3.0 20170516 ......

g++ -std=c++11 privateBase.cpp

我得到以下诊断:

privateBase.cpp:15:9: error: ‘class Base Base::Base’ is inaccessible within this context
   Upper(Base const* p) : Middle(p) {}
         ^~~~
privateBase.cpp:1:12: note: declared here
 class Base {
            ^ …