Bitwise shift operation in C on uint64_t variable

Question

I have the following sample code:

uint64_t x, y;
x = ~(0xF<<24);
y = ~(0xFF<<24);

The result would be:

x=0xffff         


        

Answer 1

Other posters have shown why it does this. But to get the expected results:

uint64_t x, y; 
x = ~(0xFULL<<24); 
y = ~(0xFFULL<<24);

Or you can do this (I don't know if this is is any slower than the above though):

uint64_t x, y; 
x = ~(uint64_t(0xF)<<24); 
y = ~(uint64_t(0xFF)<<24); 

Then:

x = 0xfffffffff0ffffff
y = 0xffffffff00ffffff