constant pointer to variable char

utkarshrawat · 03-09-2012, 03:24 AM

If I am declaring pointer like this

int *const cpi;

& I want to assign some value to this pointer ,how should I do it .I did like this but error exist

Code:

main()
{
        int const ci = 123;
        int *const cpi;
  	
        cpi = &ci;
	printf("%d",*cpi);
 
}

OUTPUT IS

Code:

const.c: In function ‘main’:
const.c:9: error: assignment of read-only variable ‘cpi’

dwhitney67 · 03-09-2012, 05:56 AM

Try to get into the habit of initializing your variables when you declare them.

Code:

#include <stdio.h>

int main()
{
    int const ci = 123;
    const int *const cpi = &ci;

    printf("%d\n",*cpi);

    return 0;
}

Note, these two style of declarations are the same:

Code:

int const ci = 123;

/* and */

const int ci = 123;

Personally, I prefer the second style; it is more intuitive for me to comprehend. And because you opted to declare ci as a const int, it was necessary to declare cpi such that the value it points to also would be treated as const.

Alternative declarations for cpi could be:

Code:

int const *const cpi = &ci;

/* or even */

const int const* cpi = &ci;

Again, I prefer the last style, although I rarely ever declare the pointer itself as const. All I typically care about is that the value that is being referenced is const.

sundialsvcs · 03-09-2012, 10:21 AM

Also consider that, even if you say that something is "constant," if you start developing addresses to that data, the compiler really can't keep you from shooting yourself in the foot anymore. Be very careful that you know what you are telling the compiler, and that what you are telling the compiler is really what you want to say. Study the compiler's documentation and the language references carefully.

"Well, it compiles..." is not enough.