Question

I wrote this short program

int main(){
    char * c = "abcd";
    c[1] = '\0';
    cout << c << endl;
}

and it doesn’t work… actually it compiles the program but in the runtime an error occures…
Why? I thought it will print an “a” as the “string” now looks like this: “a0cd” so after a zero it is supposed to detect an end of the string, right? So where is the problem?

Thank you!

Answer 1

You can’t modify string literals like that.

Try this instead:

int main(){
    char c[] = "abcd";
    c[1] = '\0';
    cout << c << endl;
}

The reason behind this is that string literals are stored in global memory (often in a read-only segment). Modifying them is undefined behavior. However, if you initialize it as an array char c[] = "abcd" it will be on the stack (as opposed to global memory), so you can freely modify it.