OLDNUM_SIZE
assert(OLDNUM_SIZE(SP_PARM) >= 0);
|| (OLDNUM_SIZE(SP_PARM) < screen_lines(SP_PARM))) {
int need_lines = ((OLDNUM_SIZE(SP_PARM) < screen_lines(SP_PARM))
: OLDNUM_SIZE(SP_PARM));
OLDNUM_SIZE(SP_PARM) = need_lines;