scc

 1#define CAT(x,y) x ## y
 2#define XCAT(x,y) CAT(x,y)
 3#define FOO foo
 4#define BAR bar
 5
 6int foobar;
 7
 8int
 9main(void)
10{
11	int foo = 1, bar = 0;
12
13	CAT(foo,bar) += foo + bar;
14	if (foobar != 1)
15		return 1;
16	XCAT(FOO,BAR) += foo + bar;
17	if (foobar != 2)
18		return 2;
19
20	return 0;
21}