bit shifting with unsigned long type produces wrong results
Solution 1:
1 << 63 will be computed in int arithmetic, and your int is probably 32 bit.
Remedy this by promoting one of the arguments: 1ULL << 63 will do it.
ULL means the expression will be at least 64 bits.
Solution 2:
The expression 1 << 63 has type int. The range of an int is -231 … 231 - 1 on most systems, 263 is too large for that. Try either (unsigned long)1 << 63 or 1UL << 63 to shift a value of type unsigned long left by 63 places.