为什么在C和C ++代码中插入URL有效？

Question

Why does the following code compile? Which section of the language allows URLs to be added in C and C++ code?

int main()
{
     http://www.stackoverflow.com
     return 0;
}

Thanks in advance, Castro.

Answer 1

If you compiled with warnings, you would notice:

warning: label ‘http’ defined but not used

That should be indicative enough of the problem here.

The http: text is treated as a label.

Followed by // negating the remaining text as a comment, ignoring it.

http://www.stackoverflow.com

Even the SO syntax colour schemes indicated as above show this to be true, as the section after the http, is treated as a comment (grayed out).

Answer 2

It's because the compiler treats http: as a label and // whatever as a comment. This is perfectly legal code.

Unless you use goto http; somewhere however, it'll be completely useless code.

Answer 3

In your code http is just a label and //www.stackoverflow.com is a comment.

Also note that

int main()
{
     http://www.stackoverflow.com
}

or

int main()
{
 http://www.stackoverflow.com
 http://www.facebook.com
 return 0;
}

won't compile.