STACK_UPPER        67 gc.h           # define STACK_UPPER(x, a, b) (a)
STACK_UPPER        69 gc.h           # define STACK_UPPER(x, a, b) (b)
STACK_UPPER        77 gc.h           # define STACK_UPPER(x, a, b) (stack_growup_p(x) ? (a) : (b))