Where is `%p` useful with printf?

Question

After all, both these statements do the same thing...

int a = 10;
int *b = &a;
printf(\"%p\\n\",b);
printf(\"%08X\\n\",b);

For example

Answer 1

They do not do the same thing. The latter printf statement interprets b as an unsigned int, which is wrong, as b is a pointer.

Pointers and unsigned ints are not always the same size, so these are not interchangeable. When they aren't the same size (an increasingly common case, as 64-bit CPUs and operating systems become more common), %x will only print half of the address. On a Mac (and probably some other systems), that will ruin the address; the output will be wrong.

Always use %p for pointers.