NULL used in arithmetic

[Michael Morrell]

The following code compiles without warning using g++ version 4.2.1, but I
get a warning "NULL used in arithmetic" with version 4.3.3.  Is the code
wrong or is the compiler wrong?

================================
#include <stddef.h>

class FooClass
{
};

typedef void (FooClass::*foo_type)(void);

int foo(foo_type x)
{
    return x != NULL;
}
================================

   Michael