Question

I am trying to implement a simple string copy in the following code.

However, I got a run-time error in the line “*d = *c;”.

Could anyone tell me what is wrong with that?

void test3()
{
    char *a="123456";
    char *b="000000";

    char *c=a;
    char *d=b;

    while(*c){
        *d = *c;
        cout << *c << endl;
        c++;
        d++;
    }

    *d='\0';
}

Answer 1

Basically, string litterals are constant and can’t be changed. In the following line:

char *a="123456";

char *a should be replaced with const char * a because a points to a block of constant memory. Further down the function, you attempt to change that block of constant memory and this yields a run-time error.

To get a real character array that you can use in such a function, you should use:

char a[] = "123456";

This will produce a mutable (non-const) array that you can manipulate freely.