What's the proper use of printf to display pointers padded with 0s

Question

In C, I\'d like to use printf to display pointers, and so that they line up properly, I\'d like to pad them with 0s.

My guess was that the proper way to do this was:

Answer 1

Maybe this will be interesting (from a 32-bit windows machine, using mingw):

rjeq@RJEQXPD /u
$ cat test.c
#include 

int main()
{
    char c;

    printf("p: %016p\n", &c);
    printf("x: %016llx\n", (unsigned long long) (unsigned long) &c);

    return 0;
}

rjeq@RJEQXPD /u
$ gcc -Wall -o test test.c
test.c: In function `main':
test.c:7: warning: `0' flag used with `%p' printf format

rjeq@RJEQXPD /u
$ ./test.exe
p:         0022FF77
x: 000000000022ff77

As you can see, the %p version pads with zeros to the size of a pointer, and then spaces to the specified size, whereas using %x and casts (the casts and format specifier are highly unportable) uses only zeros.