Why does // in a string does not start a comment in C++?

Question

I am printing a line like this

cout<<"Hello //stackoverflow";

And this produces the following output

Hello //stackoverflow

I want to know why it does not give me an error as I commented half of the statement and there should be

missing terminating " character

error.

Answer 1

The grammar of C++ (like most of programming languages) is context-sensitive. Simply, // does not start a comment if it is within a string literal.

Answer 2

For an in depth analysis of this, you'd have to refer to the language grammar, and the string literal production rules in particular.

Informally speaking, the fact that // appears in the quoted string literal means that it does not denote a comment block. The same applies to /* and */ .

The converse applies to other constructs, where maximal munch requires parsing into the token denoting the start of a comment block; a space is needed before the pointer dereference operator in

#include <iostream>
using namespace std;

int main() {
    int n = 1;
    int* p = &n;
    cout << 1 / *p; // Removing the final space will fail compilation.
}

Answer 3

简单来说，这是因为引号内的所有内容都被识别为字符串，因此计算机不会评估//作为开始评论的方式。