Is %p specifier only for valid pointers?

Question

Suppose on my platform sizeof(int)==sizeof(void*) and I have this code:

printf( \"%p\", rand() );

Will this be undefined behavior

Answer 1

Yes, it's undefined. From C++11, 3.7.4.2/4:

The effect of using an invalid pointer value (including passing it to a deallocation function) is undefined.

with a footnote:

On some implementations, it causes a system-generated runtime fault.