gcc Compiler and Pointers

Hi there,

The first sample program that I am reading on the book has the following code:

Code:

* Demonstrates basic pointer use. */

#include <stdio.h>

/* Declare and initialize an int variable */

int var = 1;

/* Declare a pointer to int */

int *ptr;

int main( void )
{
    /* Initialize ptr to point to var */

    ptr = &var;

    /* Access var directly and indirectly */

    printf("\nDirect access, var = %d", var);
    printf("\nIndirect access, var = %d", *ptr);

    /* Display the address of var two ways */

    printf("\n\nThe address of var = %d", &var);
    printf("\nThe address of var = %d\n", ptr);

    return 0;
}

When I compile it using the gcc compiler, it gives the error:

ptr.c: In function ‘main’:
ptr.c:26:5: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘int *’ [-Wformat]
ptr.c:27:5: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘int *’ [-Wformat]

Is this a compiler error or is there a proper syntax for pointers using the gcc compiler?

Thanks

Yes, the correct way to print a pointer is using the %p format.

Code:

    printf("\n\nThe address of var = %p", (void*)&var);
    printf("\nThe address of var = %p\n", (void*)ptr);

Originally Posted by Salem

Yes, the correct way to print a pointer is using the %p format.

Code:

    printf("\n\nThe address of var = %p", (void*)&var);
    printf("\nThe address of var = %p\n", (void*)ptr);

So whenever the pointer address is to be printed, the syntax above should be used? Thanks.

When you find yourself asking, "Is this a gcc compiler error, or is the code wrong?"..... it would be the latter.