preprocessing question

["Jan Beulich" <jbeulich at novell dot com>]

Can anyone set me strait on why, in the following code fragment

int x(unsigned);

struct alt_x {
	unsigned val;
};

#define x        alt_x
#define alt_x(p) x(p+1)

int test(struct x *p) {
	return x(p->val);
}

the function invoked in test() is alt_x (rather than x)? I would have
expected that the preprocessor
- finds that x is an object like macro, and replaces it with alt_x
- finds that alt_x is a function-like macro and replaces it with x(...)
- finds that again x is an object like macro, but recognizes that it
already participated in expansion, so doesn't replace x by alt_x a
second time.

Our compiler team also considers this misbehavior, but since I
tested three other compilers, and they all behave the same, I
continue to wonder if I'm mis-reading something in the standard.

Thanks a lot, Jan