#define str(s)    # s
#define xstr(s) str(s)
#define debug(s, t) printf("x" # s "= %d, x" # t "= %s", \
    x ## s, x ## t)
#define INCFILE(n) vers ## n
#define glue(a, b) a ## b
#define xglue(a, b) glue(a, b)
#define HIGHLOW "hello"
#define LOW LOW ", world"

debug(1, 2);
fputs(str(strncmp("abc\0d", "abc", '\4')  /*this goes away */
    == 0) str(: @\n), s);
#include xstr(INCFILE(2).h)
glue(HIGH, LOW)
xglue(HIGH, LOW)