dirtysalt edited a comment on pull request #670:
URL: https://github.com/apache/orc/pull/670#issuecomment-808692529
@dongjoon-hyun Oh. I never know that Java bit shift `<<` is sort of like a
circular bit shift. That's to say `1L << 129` equals `1L << (129 % 64)`. So
that explains why `1L << position` works.
If I do that in C++, the compiler will give a warning, and the result is
undefined.
```
/// c++ code
int main() {
unsigned long long x = 0;
x |= (1ULL << 129);
printf("%llu\n", x);
return 0;
}
/// shell execution
mac :: ~/Public » g++ test.cpp
test.cpp:14:16: warning: shift count >= width of type
[-Wshift-count-overflow]
x |= (1ULL << 129);
^ ~~~
1 warning generated.
mac :: ~/Public » ./a.out
4526632784
mac :: ~/Public » ./a.out
4345032528
```
But I do suggest modifying documentation as `1L << (position % 64)` which is
less confused to C++ guys.
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