c++ - 模板代码在 G++ 下工作正常，但在 VC++ 下出错

Question

下面是代码，在g++下运行良好，但在VC++ 2014下出错:

template <class A>
struct Expression 
{
public:
    static const int status = A::status_;
}; 

struct Foo : public Expression<Foo>
{
    static const int  status_ = 0;
};

int main(void) {
    return 0;
}

为什么？谢谢!

错误信息是:

error C2039: 'status_': is not a member of 'Foo'

error C2065: 'status_': undeclared identifier

error C2131: expression did not evaluate to a constant

Answer 1

定义 status 它将起作用。见下文。至于标准，我不知道哪个编译器是正确的。

template <class A>
struct Expression
{
public:
  static const int status;
};

struct Foo : public Expression<Foo>
{
  static const int  status_ = 0;
};

template< typename A >
const int Expression<A>::status = A::status_;

int main( void ) {
  return 0;
}