I am trying to set the most significant bit in a long long unsigned, x. 
To do that I am using this line of code:

```
x |= 1<<((sizeof(x)*8)-1);

```

I thought this should work, because sizeof gives size in bytes, so I multiplied by 8 and subtract one to set the final bit. Whenever I do that, the compiler has this warning: "warning: left shift count >= width of type"

I don't understand why this error is occurring.