Thread: char* functions

The bzzzzzt in my head is starting to get clearer now, it’s a wonderful sound! Tanks, again Bee.

I rest my case…

Code:

const char* myStringconst()
{
	return "FooBar";
}

int main()
{

  const void *p1 = myStringconst(), *p2 = myStringconst(), *p3 = myStringconst();
  std::cout << p1 << '\n' << p2 << '\n' << p3 << std::endl;


  system("pause");
  return 0;
}

/* OUT: 
00417A28
00417A28
00417A28	
*/

Originally Posted by Noir

Yes, a string constant has static lifetime.

The constant itself does, but it's still possible to shoot yourself in the foot. For instance:

Code:

#include <iostream>

// This function works correctly.
const char *get_string()
{
    char *hello = "Hello!";
    return hello;
}

// This function is wrong.
const char *get_string_2()
{
    // But I'm still using a string constant, right? What's goin' on?
    char hello[] = "Hello!";
    return hello;
}

// This function makes sure you see the problem
void kill_stack(int a, int b, int c, int d, int e, int f, int g)
{
}

int main()
{
    const char *str;

    str = get_string();
    std::cout << str << std::endl;
    str = get_string_2();
    kill_stack(1,2,3,4,5,6,7);
    std::cout << str << std::endl;
    return 0;
}

I'll leave it a mystery for those who don't get it. Arrays and pointers are not the same thing!

The constant itself does, but it's still possible to shoot yourself in the foot.

When you use a string constant to initialize an array, you're not working with a string constant anymore and the lifetime of the array is your rule, not the lifetime of the constant you used to initialize it. It's like you're saying that you can only get hit by a train on train tracks, but it's still possible to shoot yourself in the foot by jumping off a bridge. They're two completely different things.

Originally Posted by Noir

When you use a string constant to initialize an array, you're not working with a string constant anymore and the lifetime of the array is your rule, not the lifetime of the constant you used to initialize it. It's like you're saying that you can only get hit by a train on train tracks, but it's still possible to shoot yourself in the foot by jumping off a bridge. They're two completely different things.

The entire point I'm trying to make is that they ARE completely different things, but look alarmingly similar. All I did was replace a "*" with a "[]". This is an immensely confusing aspect of C for many people.

The question had nothing to do with the difference between pointers and arrays, so bringing it up doesn't accomplish anything. It's like warning that = is different from == whenever someone posts code using a comparison. It would be good to know...if we cared.