add0
p = add0(p, skq - skp);
q = add0(q, skp - skq);
p = add0(rem, skd - (skr + k));
t = add0(p, n);
arg1 = add0(p, n);
r = add0(dd, c);
struct blk *pop(void), *readin(void), *add0(struct blk *, int),