string initialization

[zhanghongqi]

Hi, all

What is the difference of following char initializations.
char *p="Hello";
char p[]="Hello";

[Meetee]

Hi, all

What is the difference of following char initializations.
char *p="Hello";
char p[]="Hello";

Hi,

In the first case if *p is assigned to some other value the allocate memory can change, where as in the second case 5 bytes are allocated to the variable p which is fixed.

Regards

[oler1s]

Let me clarify. The first method gets you a pointer to a constant literal. You can't modify it. Well, you could always point p to something else, but then you lose the reference to the string literal.

The second method gets you an actual character array, and then initializes it.

[mattmao]

I reckon the difference is: with the first option you allocate new memory every time you modify the content, whereas with the second option, you allocate the memory address once and then only change the content start from that address.

#include <stdio.h>
 
int main()
{
    char *array1="ABCDEFG";
    char array2[]="ABCDEFG";
    int i;
 
 
    printf("array1 contains:%s\n", array1);
    printf("array2 contains:%s\n", array2);
 
    array1="XXXXXXX";
 
    for(i=0; i<7; i++)
    {
        array2[i]='X';
    }
 
    printf("array1 contains:%s\n", array1);
    printf("array2 contains:%s\n", array2);
 
    return 0;
}

Here is the result:

Mattmao@(dspp) 181$gcc arrays.c
Mattmao@(dspp) 182$./a.exe
array1 contains:ABCDEFG
array2 contains:ABCDEFG
array1 contains:XXXXXXX
array2 contains:XXXXXXX
Mattmao@(dspp) 183$