Why does inserting URLs in C and C++ code work?

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.

I went ahead and properly formatted your question using the code formatting, instead of block quote - that makes it pretty obvious, as Daniel said. — Cascabel, Mar 21 '11 at 05:22
http://stackoverflow.com/questions/75538/hidden-features-of-c/78840#78840 — Inverse, Mar 26 '11 at 06:53

hiddensunset4 · Accepted Answer · 2017-07-13T03:37:45.010

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).

score 3 · Answer 2 · answered Mar 21 '11 at 05:19

3

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.

answered Mar 21 '11 at 05:19

Mark B

Prasoon Saurav · Answer 3 · 2011-03-21T05:29:46.747

1

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.

edited Mar 21 '11 at 05:29

answered Mar 21 '11 at 05:19

Prasoon Saurav

3 Answers3