convert_integer
int64_t convert_integer(int64_t, tspec_t, unsigned int);
ui = (uint64_t)convert_integer((int64_t)ui, t, size_in_bits(t));
? convert_integer((int64_t)val, CHAR, CHAR_SIZE)
v->u.integer = convert_integer(res, t, size_in_bits(t));
nv->u.integer = convert_integer(nv->u.integer, nt, size);