C++ 标识符

Question

C++ Primer 说:

The identifier we define in our programs may not contain 2 consecutive underscores, nor can identifier begin with an underscore followed immediately by an uppercase letter. In addition, identifiers be fined outside of a function may not begin with an underscore

一切都很好，但是

int _c = 55;                  // outside function starts with _

int main () {

    int _A = 12;              // _ followed by uppercase letter
    cout << _A << endl;

    int __b__ =33;            // 2 consecutive __
    cout << __b__ << endl;

    cout << _c << endl;

}

上面的代码在 mac 上编译得很好，g++ 4.7.1，使用以下标志

g++ -pedantic -Wall -Werror -std=c++11 -O3 -funroll-loops -fprefetch-loop-arrays

请问我错过了什么？

Answer 1

过马路而不注意双向交通并不能保证您会被公共(public)汽车碾过，但这仍然是一个坏主意。

有一天它不会工作......