// get the n'th bit of a number
// the bit number starts from 0
#define BIT_N(number, bit_num)  (((number)>>(bit_num))&0x1)
#define OVERFLOW(A,B,S) ((A)&(B)&(~(C))|(~(A))&(~(B))&(C))


//#define INT_OVERFLOW(a,b,s) OVERFLOW(a>>31,b>>31,c>>31)

int main()
{
        char a = -4;
        char b = -125;
        char s = a + b;
        int bp = sizeof(a)*8-1; // number of the last bit
        int overflow = OVERFLOW(BIT_N(a,bp), BIT_N(b,bp), BIT_N(s,bp));

        printf("for numbers a:%d and b:%d the sum is %d and overflow:%d\n", a, b, s, overflow);
}
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