struct foo { unsigned long long b:40; } x; extern void abort (void); void test1(unsigned long long res) { /* Build a rotate expression on a 40 bit argument. */ if ((x.b<<8) + (x.b>>32) != res) abort (); } int main() { x.b = 0x0100000001; test1(0x0000000101); x.b = 0x0100000000; test1(0x0000000001); return 0; }