How is “const” implemented?

Question

How does a compiler, C or C++, (for example, gcc) honors the const declaration?

For example, in the following code, how does the compiler keeps trac

Answer 1

As others have said, const is tracked by the compiler the same way the compiler tracks the fact that a variable is an int. In fact, I have read that at least gcc considers const int a distinct type from int, so it's not even tracked as a modifier, it's tracked the exact same way as an int.

Note that you actually can change the value of a const via pointer casting, but the result is undefined:

#include 
#include 

int main(void) {
        const int c = 0;
        printf("%d\n", c);
        ++*(int*)&c;
        printf("%d\n", c);
}

On my machine using gcc, this prints

0
1

But compiling with g++ gives

0
0