Question

I am writing reverseString function by myself. (For test use) And I use iOS platform to run my c code, which sounds weird, but again, for test use…

Here is my code:

-(char *) reverseString:(char *)str
{
    char *end = str;
    char tmp;

    if (str)
    {
        while (*end) { end++; }
        --end;
        NSLog(@"%c", *end);
        while (end>str)
        {
            tmp = *str;
            *str = *end;
            str++;
            *end = tmp;
            end--;
        }
    }
    NSLog(@"%s", str);
    return str;
}

After running the function by calling:

char *testChar = "abcd";
[self reverseString:testChar];

I received the error on line:

*str = *end;
Thread 1: EXC_BAD_ACCESS(code=2, address=0x2de4)

I don’t really know understand what’s wrong with the pointer here…Anyone has any idea?

Answer 1

You can’t modify a string literal. Use a char array instead.

char testChar[] = "abcd";