COMPAR
cmp = COMPAR(key, p);
if (child_i < nmemb && COMPAR(child, child + size) < 0) { \
if (child_i == 1 || COMPAR(k, par) < 0) { \
if (child_i < nmemb && COMPAR(child, child + size) < 0) { \
if (COMPAR(child, par) <= 0) \