How to print variable addresses in C?

Question

When i run this code.

#include <stdio.h>  void moo(int a, int *b);  int main() {     int x;     int *y;      x = 1;     y = &x;      printf("Address of x = %d, value of x = %d\n", &x, x);     printf("Address of y = &d, value of y = %d, value of *y = %d\n", &y, y, *y);     moo(9, y); }  void moo(int a, int *b) {     printf("Address of a = %d, value of a = %d\n", &a, a);     printf("Address of b = %d, value of b = %d, value of *b = %d\n", &b, b, *b); } 

I keep getting this error in my compiler.

/Volumes/MY USB/C Programming/Practice/addresses.c:16: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘int *’ /Volumes/MY USB/C Programming/Practice/addresses.c:17: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘int **’ /Volumes/MY USB/C Programming/Practice/addresses.c:17: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘int *’ /Volumes/MY USB/C Programming/Practice/addresses.c: In function ‘moo’: /Volumes/MY USB/C Programming/Practice/addresses.c:23: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘int *’ /Volumes/MY USB/C Programming/Practice/addresses.c:24: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘int **’ /Volumes/MY USB/C Programming/Practice/addresses.c:24: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘int *’ 

Could you help me?

Thanks

blargman

Answer 1

You want to use %p to print a pointer. From the spec:

p The argument shall be a pointer to void. The value of the pointer is converted to a sequence of printing characters, in an implementation-defined manner.

And don't forget the cast, e.g.

printf("%p\n",(void*)&a); 

Answer 2

When you intend to print the memory address of any variable or a pointer, using %d won't do the job and will cause some compilation errors, because you're trying to print out a number instead of an address, and even if it does work, you'd have an intent error, because a memory address is not a number. the value 0xbfc0d878 is surely not a number, but an address.

What you should use is %p. e.g.,

#include<stdio.h>  int main(void) {      int a;     a = 5;     printf("The memory address of a is: %p\n", (void*) &a);     return 0; } 

Good luck!