Elipses是否为case语句标准C/C++

Question

我正在浏览linux内核中的一些代码,我遇到了类似的语句 case '0' ... '9':

为了试试这个,我在下面创建了测试程序.

#include <iostream>

int main()
{
    const int k = 15;

    switch (k)
    {
    case 0 ... 10:
        std::cout << "k is less than 10" << std::endl;
        break;
    case 11 ... 100:
        std::cout << "k is between 11 and 100" << std::endl;
        break;
    default:    
        std::cout << "k greater than 100" << std::endl;
        break;
    }
}   

上面的程序确实编译了,虽然我之前从未遇到过case语句构造中的elipses.这个标准的C和C++还是这个语言的GNU特定扩展？

Answer 1

这是GNU C编译器的案例范围扩展,它不是标准的C或C++.

Answer 2

这是一个扩展.编译你的程序-pedantic给出:

example.cpp: In function ‘int main()’:
example.cpp:9: error: range expressions in switch statements are non-standard
example.cpp:12: error: range expressions in switch statements are non-standard

clang 给出更好的警告:

example.cpp:9:12: warning: use of GNU case range extension [-Wgnu]
    case 0 ... 10:
           ^
example.cpp:12:13: warning: use of GNU case range extension [-Wgnu]
    case 11 ... 100:
            ^