>> The test was, if I recall correctly >> >> x = a + b; >> if ((x ^ a) & (x ^ b)) < 0) >> >> all you have to do is convert everything to unsigned values, then >> >> ux = ua + ub; >> if ((ux ^ ua) & (ux ^ ub)) & (unsigned)INT_MIN)) >> goto deal_with_overflow; >> // we now know there is no overflow >> x = ux; >> >> which is exactly the same test as before, but perfectly compliant. > > The comment is wrong. The code checks for signed overflow, but the > following assignment still overflwos when ux is larger than INT_MAX. No, it doesn't. This conversion is implementation-defined (6.3.1.3/3), and GCC does the obvious two's complement thing. This code is fine. Segher
