There are at least two problems here. First of all, string literals are pointers, so SIZEOF_STAMP(UNIQUE_STAMP_BEGIN) == sizeof( char* ).
This is not true. Try it. A string literal is a const char array.
It is too clear and so it is hard to see.
A dunce once searched for fire with a lighted lantern.
Had he known what fire was,
He could have cooked his rice much sooner.