SHN_HIRESERVE
if (index >= SHN_LORESERVE && index <= SHN_HIRESERVE)
return index - SHN_HIRESERVE - 1;
#define SPECIAL(i) ((i) - (SHN_HIRESERVE + 1))
return i != SHN_XINDEX && i >= SHN_LORESERVE && i <= SHN_HIRESERVE;