Strange issue with a Bitset of size 64 (cardinality always 0)

[kevinjalbert]

If you have a Bitset of size 64, you get an incorrect cardinality value (always 0).

bits = Bitset.new(64)
bits.set(13,23)
puts bits.cardinality

Results in the value of 0, when it should be 2.

[brendon9x]

This occurs with all Bitsets that have sizes that are multiples of 64. Bits set in the final word will not be counted.

For example:

a = Bitset.new(128)
a[65] = 1
a.cardinality #= prints 0

Error down to this line:

if(i+1 == max)
        segment &= ((((uint64_t) 1) << (bs->len & 0x3F)) - 1)

Substituting bs->len for any multiple of 64 results in segment &= 0

This is a bit beyond my comfort zone. I'd suggest a modulo check, but the source looks like it's geared for speed.

[brendon9x]

Perhaps if(i+1 == max && (bs->len & 0x3F)) ?

[kevinjalbert]

I'm closing this issue as a great deal of time has passed. If there is renewed interest just reopen or make a new issue and link to this one.